Adding upstream version 2.7.6.upstream/2.7.6upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

65 files changed, 20938 insertions, 0 deletions

diff --git a/src/contrib/Makefile.inc b/src/contrib/Makefile.inc
new file mode 100644
index 0000000..a6b6576
--- /dev/null
+++ b/src/contrib/Makefile.inc
@@ -0,0 +1,103 @@
+noinst_LTLIBRARIES += libcontrib.la
+
+libcontrib_la_CPPFLAGS = $(AM_CPPFLAGS) $(CFLAG_VISIBILITY)
+libcontrib_la_LDFLAGS  = $(AM_LDFLAGS) $(LDFLAG_EXCLUDE_LIBS)
+if !HAVE_LMDB
+libcontrib_la_LDFLAGS += $(pthread_LIBS)
+endif !HAVE_LMDB
+
+EXTRA_DIST += \
+	contrib/licenses/0BSD			\
+	contrib/licenses/BSD-3-Clause		\
+	contrib/licenses/LGPL-2.0		\
+	contrib/licenses/OLDAP-2.8		\
+	contrib/lmdb/LICENSE			\
+	contrib/openbsd/LICENSE			\
+	contrib/ucw/LICENSE			\
+	contrib/dnstap/dnstap.proto
+
+libcontrib_la_SOURCES = \
+	contrib/asan.h				\
+	contrib/base32hex.c			\
+	contrib/base32hex.h			\
+	contrib/base64.c			\
+	contrib/base64.h			\
+	contrib/ctype.h				\
+	contrib/dynarray.h			\
+	contrib/files.c				\
+	contrib/files.h				\
+	contrib/getline.c			\
+	contrib/getline.h			\
+	contrib/macros.h			\
+	contrib/mempattern.c			\
+	contrib/mempattern.h			\
+	contrib/net.c				\
+	contrib/net.h				\
+	contrib/qp-trie/trie.c			\
+	contrib/qp-trie/trie.h			\
+	contrib/sockaddr.c			\
+	contrib/sockaddr.h			\
+	contrib/string.c			\
+	contrib/string.h			\
+	contrib/strtonum.h			\
+	contrib/time.c				\
+	contrib/time.h				\
+	contrib/tolower.h			\
+	contrib/trim.h				\
+	contrib/wire_ctx.h			\
+	contrib/openbsd/siphash.c		\
+	contrib/openbsd/siphash.h		\
+	contrib/openbsd/strlcat.c		\
+	contrib/openbsd/strlcat.h		\
+	contrib/openbsd/strlcpy.c		\
+	contrib/openbsd/strlcpy.h		\
+	contrib/ucw/array-sort.h		\
+	contrib/ucw/binsearch.h			\
+	contrib/ucw/heap.c			\
+	contrib/ucw/heap.h			\
+	contrib/ucw/lists.c			\
+	contrib/ucw/lists.h			\
+	contrib/ucw/mempool.c			\
+	contrib/ucw/mempool.h
+
+if !HAVE_LMDB
+libcontrib_la_SOURCES += \
+	contrib/lmdb/lmdb.h			\
+	contrib/lmdb/mdb.c			\
+	contrib/lmdb/midl.c			\
+	contrib/lmdb/midl.h
+endif !HAVE_LMDB
+
+if HAVE_LIBDNSTAP
+noinst_LTLIBRARIES += libdnstap.la
+
+libdnstap_la_CPPFLAGS = $(AM_CPPFLAGS) $(DNSTAP_CFLAGS)
+libdnstap_la_LDFLAGS  = $(AM_LDFLAGS) $(DNSTAP_LIBS)
+
+SUFFIXES = .proto .pb-c.c .pb-c.h
+
+.proto.pb-c.c:
+	$(AM_V_GEN)@PROTOC_C@ --c_out=. -I$(srcdir) $<
+
+.proto.pb-c.h:
+	$(AM_V_GEN)@PROTOC_C@ --c_out=. -I$(srcdir) $<
+
+libdnstap_la_SOURCES = \
+	contrib/dnstap/convert.c	\
+	contrib/dnstap/convert.h	\
+	contrib/dnstap/dnstap.c		\
+	contrib/dnstap/dnstap.h		\
+	contrib/dnstap/message.c	\
+	contrib/dnstap/message.h	\
+	contrib/dnstap/reader.c		\
+	contrib/dnstap/reader.h		\
+	contrib/dnstap/writer.c		\
+	contrib/dnstap/writer.h
+
+nodist_libdnstap_la_SOURCES = \
+	contrib/dnstap/dnstap.pb-c.c	\
+	contrib/dnstap/dnstap.pb-c.h
+
+BUILT_SOURCES += $(nodist_libdnstap_la_SOURCES)
+CLEANFILES    += $(nodist_libdnstap_la_SOURCES)
+endif HAVE_LIBDNSTAP
diff --git a/src/contrib/asan.h b/src/contrib/asan.h
new file mode 100644
index 0000000..112f81e
--- /dev/null
+++ b/src/contrib/asan.h
@@ -0,0 +1,37 @@
+/*  Copyright (C) 2015 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+/*
+ * see sanitizer/asan_interface.h in compiler-rt (LLVM)
+ */
+#ifndef __has_feature
+  #define __has_feature(feature) 0
+#endif
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+  void __asan_poison_memory_region(void const volatile *addr, size_t size);
+  void __asan_unpoison_memory_region(void const volatile *addr, size_t size);
+  #define ASAN_POISON_MEMORY_REGION(addr, size) \
+    __asan_poison_memory_region((addr), (size))
+  #define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+    __asan_unpoison_memory_region((addr), (size))
+#else
+  #define ASAN_POISON_MEMORY_REGION(addr, size) \
+    ((void)(addr), (void)(size))
+  #define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+    ((void)(addr), (void)(size))
+#endif
diff --git a/src/contrib/base32hex.c b/src/contrib/base32hex.c
new file mode 100644
index 0000000..56fb427
--- /dev/null
+++ b/src/contrib/base32hex.c
@@ -0,0 +1,353 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "contrib/base32hex.h"
+#include "libknot/errcode.h"
+
+#include <stdlib.h>
+#include <stdint.h>
+
+/*! \brief Maximal length of binary input to Base32hex encoding. */
+#define MAX_BIN_DATA_LEN	((INT32_MAX / 8) * 5)
+
+/*! \brief Base32hex padding character. */
+static const uint8_t base32hex_pad = '=';
+/*! \brief Base32hex alphabet. */
+static const uint8_t base32hex_enc[] = "0123456789abcdefghijklmnopqrstuv";
+
+/*! \brief Indicates bad Base32hex character. */
+#define KO	255
+/*! \brief Indicates Base32hex padding character. */
+#define PD	 32
+
+/*! \brief Transformation and validation table for decoding Base32hex. */
+static const uint8_t base32hex_dec[256] = {
+	[  0] = KO, [ 43] = KO, ['V'] = 31, [129] = KO, [172] = KO, [215] = KO,
+	[  1] = KO, [ 44] = KO, ['W'] = KO, [130] = KO, [173] = KO, [216] = KO,
+	[  2] = KO, [ 45] = KO, ['X'] = KO, [131] = KO, [174] = KO, [217] = KO,
+	[  3] = KO, [ 46] = KO, ['Y'] = KO, [132] = KO, [175] = KO, [218] = KO,
+	[  4] = KO, [ 47] = KO, ['Z'] = KO, [133] = KO, [176] = KO, [219] = KO,
+	[  5] = KO, ['0'] =  0, [ 91] = KO, [134] = KO, [177] = KO, [220] = KO,
+	[  6] = KO, ['1'] =  1, [ 92] = KO, [135] = KO, [178] = KO, [221] = KO,
+	[  7] = KO, ['2'] =  2, [ 93] = KO, [136] = KO, [179] = KO, [222] = KO,
+	[  8] = KO, ['3'] =  3, [ 94] = KO, [137] = KO, [180] = KO, [223] = KO,
+	[  9] = KO, ['4'] =  4, [ 95] = KO, [138] = KO, [181] = KO, [224] = KO,
+	[ 10] = KO, ['5'] =  5, [ 96] = KO, [139] = KO, [182] = KO, [225] = KO,
+	[ 11] = KO, ['6'] =  6, ['a'] = 10, [140] = KO, [183] = KO, [226] = KO,
+	[ 12] = KO, ['7'] =  7, ['b'] = 11, [141] = KO, [184] = KO, [227] = KO,
+	[ 13] = KO, ['8'] =  8, ['c'] = 12, [142] = KO, [185] = KO, [228] = KO,
+	[ 14] = KO, ['9'] =  9, ['d'] = 13, [143] = KO, [186] = KO, [229] = KO,
+	[ 15] = KO, [ 58] = KO, ['e'] = 14, [144] = KO, [187] = KO, [230] = KO,
+	[ 16] = KO, [ 59] = KO, ['f'] = 15, [145] = KO, [188] = KO, [231] = KO,
+	[ 17] = KO, [ 60] = KO, ['g'] = 16, [146] = KO, [189] = KO, [232] = KO,
+	[ 18] = KO, ['='] = PD, ['h'] = 17, [147] = KO, [190] = KO, [233] = KO,
+	[ 19] = KO, [ 62] = KO, ['i'] = 18, [148] = KO, [191] = KO, [234] = KO,
+	[ 20] = KO, [ 63] = KO, ['j'] = 19, [149] = KO, [192] = KO, [235] = KO,
+	[ 21] = KO, [ 64] = KO, ['k'] = 20, [150] = KO, [193] = KO, [236] = KO,
+	[ 22] = KO, ['A'] = 10, ['l'] = 21, [151] = KO, [194] = KO, [237] = KO,
+	[ 23] = KO, ['B'] = 11, ['m'] = 22, [152] = KO, [195] = KO, [238] = KO,
+	[ 24] = KO, ['C'] = 12, ['n'] = 23, [153] = KO, [196] = KO, [239] = KO,
+	[ 25] = KO, ['D'] = 13, ['o'] = 24, [154] = KO, [197] = KO, [240] = KO,
+	[ 26] = KO, ['E'] = 14, ['p'] = 25, [155] = KO, [198] = KO, [241] = KO,
+	[ 27] = KO, ['F'] = 15, ['q'] = 26, [156] = KO, [199] = KO, [242] = KO,
+	[ 28] = KO, ['G'] = 16, ['r'] = 27, [157] = KO, [200] = KO, [243] = KO,
+	[ 29] = KO, ['H'] = 17, ['s'] = 28, [158] = KO, [201] = KO, [244] = KO,
+	[ 30] = KO, ['I'] = 18, ['t'] = 29, [159] = KO, [202] = KO, [245] = KO,
+	[ 31] = KO, ['J'] = 19, ['u'] = 30, [160] = KO, [203] = KO, [246] = KO,
+	[ 32] = KO, ['K'] = 20, ['v'] = 31, [161] = KO, [204] = KO, [247] = KO,
+	[ 33] = KO, ['L'] = 21, ['w'] = KO, [162] = KO, [205] = KO, [248] = KO,
+	[ 34] = KO, ['M'] = 22, ['x'] = KO, [163] = KO, [206] = KO, [249] = KO,
+	[ 35] = KO, ['N'] = 23, ['y'] = KO, [164] = KO, [207] = KO, [250] = KO,
+	[ 36] = KO, ['O'] = 24, ['z'] = KO, [165] = KO, [208] = KO, [251] = KO,
+	[ 37] = KO, ['P'] = 25, [123] = KO, [166] = KO, [209] = KO, [252] = KO,
+	[ 38] = KO, ['Q'] = 26, [124] = KO, [167] = KO, [210] = KO, [253] = KO,
+	[ 39] = KO, ['R'] = 27, [125] = KO, [168] = KO, [211] = KO, [254] = KO,
+	[ 40] = KO, ['S'] = 28, [126] = KO, [169] = KO, [212] = KO, [255] = KO,
+	[ 41] = KO, ['T'] = 29, [127] = KO, [170] = KO, [213] = KO,
+	[ 42] = KO, ['U'] = 30, [128] = KO, [171] = KO, [214] = KO,
+};
+
+int32_t base32hex_encode(const uint8_t  *in,
+                         const uint32_t in_len,
+                         uint8_t        *out,
+                         const uint32_t out_len)
+{
+	// Checking inputs.
+	if (in == NULL || out == NULL) {
+		return KNOT_EINVAL;
+	}
+	if (in_len > MAX_BIN_DATA_LEN || out_len < ((in_len + 4) / 5) * 8) {
+		return KNOT_ERANGE;
+	}
+
+	uint8_t		rest_len = in_len % 5;
+	const uint8_t	*stop = in + in_len - rest_len;
+	uint8_t		*text = out;
+
+	// Encoding loop takes 5 bytes and creates 8 characters.
+	while (in < stop) {
+		text[0] = base32hex_enc[in[0] >> 3];
+		text[1] = base32hex_enc[(in[0] & 0x07) << 2 | in[1] >> 6];
+		text[2] = base32hex_enc[(in[1] & 0x3E) >> 1];
+		text[3] = base32hex_enc[(in[1] & 0x01) << 4 | in[2] >> 4];
+		text[4] = base32hex_enc[(in[2] & 0x0F) << 1 | in[3] >> 7];
+		text[5] = base32hex_enc[(in[3] & 0x7C) >> 2];
+		text[6] = base32hex_enc[(in[3] & 0x03) << 3 | in[4] >> 5];
+		text[7] = base32hex_enc[in[4] & 0x1F];
+		text += 8;
+		in += 5;
+	}
+
+	// Processing of padding, if any.
+	switch (rest_len) {
+	case 4:
+		text[0] = base32hex_enc[in[0] >> 3];
+		text[1] = base32hex_enc[(in[0] & 0x07) << 2 | in[1] >> 6];
+		text[2] = base32hex_enc[(in[1] & 0x3E) >> 1];
+		text[3] = base32hex_enc[(in[1] & 0x01) << 4 | in[2] >> 4];
+		text[4] = base32hex_enc[(in[2] & 0x0F) << 1 | in[3] >> 7];
+		text[5] = base32hex_enc[(in[3] & 0x7C) >> 2];
+		text[6] = base32hex_enc[(in[3] & 0x03) << 3];
+		text[7] = base32hex_pad;
+		text += 8;
+		break;
+	case 3:
+		text[0] = base32hex_enc[in[0] >> 3];
+		text[1] = base32hex_enc[(in[0] & 0x07) << 2 | in[1] >> 6];
+		text[2] = base32hex_enc[(in[1] & 0x3E) >> 1];
+		text[3] = base32hex_enc[(in[1] & 0x01) << 4 | in[2] >> 4];
+		text[4] = base32hex_enc[(in[2] & 0x0F) << 1];
+		text[5] = base32hex_pad;
+		text[6] = base32hex_pad;
+		text[7] = base32hex_pad;
+		text += 8;
+		break;
+	case 2:
+		text[0] = base32hex_enc[in[0] >> 3];
+		text[1] = base32hex_enc[(in[0] & 0x07) << 2 | in[1] >> 6];
+		text[2] = base32hex_enc[(in[1] & 0x3E) >> 1];
+		text[3] = base32hex_enc[(in[1] & 0x01) << 4];
+		text[4] = base32hex_pad;
+		text[5] = base32hex_pad;
+		text[6] = base32hex_pad;
+		text[7] = base32hex_pad;
+		text += 8;
+		break;
+	case 1:
+		text[0] = base32hex_enc[in[0] >> 3];
+		text[1] = base32hex_enc[(in[0] & 0x07) << 2];
+		text[2] = base32hex_pad;
+		text[3] = base32hex_pad;
+		text[4] = base32hex_pad;
+		text[5] = base32hex_pad;
+		text[6] = base32hex_pad;
+		text[7] = base32hex_pad;
+		text += 8;
+		break;
+	}
+
+	return (text - out);
+}
+
+int32_t base32hex_encode_alloc(const uint8_t  *in,
+                               const uint32_t in_len,
+                               uint8_t        **out)
+{
+	// Checking inputs.
+	if (out == NULL) {
+		return KNOT_EINVAL;
+	}
+	if (in_len > MAX_BIN_DATA_LEN) {
+		return KNOT_ERANGE;
+	}
+
+	// Compute output buffer length.
+	uint32_t out_len = ((in_len + 4) / 5) * 8;
+
+	// Allocate output buffer.
+	*out = malloc(out_len);
+	if (*out == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	// Encode data.
+	int32_t ret = base32hex_encode(in, in_len, *out, out_len);
+	if (ret < 0) {
+		free(*out);
+		*out = NULL;
+	}
+
+	return ret;
+}
+
+int32_t base32hex_decode(const uint8_t  *in,
+                         const uint32_t in_len,
+                         uint8_t        *out,
+                         const uint32_t out_len)
+{
+	// Checking inputs.
+	if (in == NULL || out == NULL) {
+		return KNOT_EINVAL;
+	}
+	if (in_len > INT32_MAX || out_len < ((in_len + 7) / 8) * 5) {
+		return KNOT_ERANGE;
+	}
+	if ((in_len % 8) != 0) {
+		return KNOT_BASE32HEX_ESIZE;
+	}
+
+	const uint8_t	*stop = in + in_len;
+	uint8_t		*bin = out;
+	uint8_t		pad_len = 0;
+	uint8_t		c1, c2, c3, c4, c5, c6, c7, c8;
+
+	// Decoding loop takes 8 characters and creates 5 bytes.
+	while (in < stop) {
+		// Filling and transforming 8 Base32hex chars.
+		c1 = base32hex_dec[in[0]];
+		c2 = base32hex_dec[in[1]];
+		c3 = base32hex_dec[in[2]];
+		c4 = base32hex_dec[in[3]];
+		c5 = base32hex_dec[in[4]];
+		c6 = base32hex_dec[in[5]];
+		c7 = base32hex_dec[in[6]];
+		c8 = base32hex_dec[in[7]];
+
+		// Check 8. char if is bad or padding.
+		if (c8 >= PD) {
+			if (c8 == PD && pad_len == 0) {
+				pad_len = 1;
+			} else {
+				return KNOT_BASE32HEX_ECHAR;
+			}
+		}
+
+		// Check 7. char if is bad or padding (if so, 6. must be too).
+		if (c7 >= PD) {
+			if (c7 == PD && c6 == PD && pad_len == 1) {
+				pad_len = 3;
+			} else {
+				return KNOT_BASE32HEX_ECHAR;
+			}
+		}
+
+		// Check 6. char if is bad or padding.
+		if (c6 >= PD) {
+			if (!(c6 == PD && pad_len == 3)) {
+				return KNOT_BASE32HEX_ECHAR;
+			}
+		}
+
+		// Check 5. char if is bad or padding.
+		if (c5 >= PD) {
+			if (c5 == PD && pad_len == 3) {
+				pad_len = 4;
+			} else {
+				return KNOT_BASE32HEX_ECHAR;
+			}
+		}
+
+		// Check 4. char if is bad or padding (if so, 3. must be too).
+		if (c4 >= PD) {
+			if (c4 == PD && c3 == PD && pad_len == 4) {
+				pad_len = 6;
+			} else {
+				return KNOT_BASE32HEX_ECHAR;
+			}
+		}
+
+		// Check 3. char if is bad or padding.
+		if (c3 >= PD) {
+			if (!(c3 == PD && pad_len == 6)) {
+				return KNOT_BASE32HEX_ECHAR;
+			}
+		}
+
+		// 1. and 2. chars must not be padding.
+		if (c2 >= PD || c1 >= PD) {
+			return KNOT_BASE32HEX_ECHAR;
+		}
+
+		// Computing of output data based on padding length.
+		switch (pad_len) {
+		case 0:
+			bin[4] = (c7 << 5) + c8;
+			// FALLTHROUGH
+		case 1:
+			bin[3] = (c5 << 7) + (c6 << 2) + (c7 >> 3);
+			// FALLTHROUGH
+		case 3:
+			bin[2] = (c4 << 4) + (c5 >> 1);
+			// FALLTHROUGH
+		case 4:
+			bin[1] = (c2 << 6) + (c3 << 1) + (c4 >> 4);
+			// FALLTHROUGH
+		case 6:
+			bin[0] = (c1 << 3) + (c2 >> 2);
+		}
+
+		// Update output end.
+		switch (pad_len) {
+		case 0:
+			bin += 5;
+			break;
+		case 1:
+			bin += 4;
+			break;
+		case 3:
+			bin += 3;
+			break;
+		case 4:
+			bin += 2;
+			break;
+		case 6:
+			bin += 1;
+			break;
+		}
+
+		in += 8;
+	}
+
+	return (bin - out);
+}
+
+int32_t base32hex_decode_alloc(const uint8_t  *in,
+                               const uint32_t in_len,
+                               uint8_t        **out)
+{
+	// Checking inputs.
+	if (out == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	// Compute output buffer length.
+	uint32_t out_len = ((in_len + 7) / 8) * 5;
+
+	// Allocate output buffer.
+	*out = malloc(out_len);
+	if (*out == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	// Decode data.
+	int32_t ret = base32hex_decode(in, in_len, *out, out_len);
+	if (ret < 0) {
+		free(*out);
+		*out = NULL;
+	}
+
+	return ret;
+}
diff --git a/src/contrib/base32hex.h b/src/contrib/base32hex.h
new file mode 100644
index 0000000..027acd8
--- /dev/null
+++ b/src/contrib/base32hex.h
@@ -0,0 +1,103 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Base32hex implementation (RFC 4648).
+ *
+ * \note Input Base32hex string can contain a-v characters. These characters
+ *       are considered as A-V equivalent. Lower-case variant is used for encoding!
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+/*!
+ * \brief Encodes binary data using Base32hex.
+ *
+ * \note Output data buffer contains Base32hex text string which isn't
+ *       terminated with '\0'!
+ *
+ * \param in		Input binary data.
+ * \param in_len	Length of input data.
+ * \param out		Output data buffer.
+ * \param out_len	Size of output buffer.
+ *
+ * \retval >=0		length of output string.
+ * \retval KNOT_E*	if error.
+ */
+int32_t base32hex_encode(const uint8_t  *in,
+                         const uint32_t in_len,
+                         uint8_t        *out,
+                         const uint32_t out_len);
+
+/*!
+ * \brief Encodes binary data using Base32hex and output stores to own buffer.
+ *
+ * \note Output data buffer contains Base32hex text string which isn't
+ *       terminated with '\0'!
+ *
+ * \note Output buffer should be deallocated after use.
+ *
+ * \param in		Input binary data.
+ * \param in_len	Length of input data.
+ * \param out		Output data buffer.
+ *
+ * \retval >=0		length of output string.
+ * \retval KNOT_E*	if error.
+ */
+int32_t base32hex_encode_alloc(const uint8_t  *in,
+                               const uint32_t in_len,
+                               uint8_t        **out);
+
+/*!
+ * \brief Decodes text data using Base32hex.
+ *
+ * \note Input data needn't be terminated with '\0'.
+ *
+ * \note Input data must be continuous Base32hex string!
+ *
+ * \param in		Input text data.
+ * \param in_len	Length of input string.
+ * \param out		Output data buffer.
+ * \param out_len	Size of output buffer.
+ *
+ * \retval >=0		length of output data.
+ * \retval KNOT_E*	if error.
+ */
+int32_t base32hex_decode(const uint8_t  *in,
+                         const uint32_t in_len,
+                         uint8_t        *out,
+                         const uint32_t out_len);
+
+/*!
+ * \brief Decodes text data using Base32hex and output stores to own buffer.
+ *
+ * \note Input data needn't be terminated with '\0'.
+ *
+ * \note Input data must be continuous Base32hex string!
+ *
+ * \note Output buffer should be deallocated after use.
+ *
+ * \param in		Input text data.
+ * \param in_len	Length of input string.
+ * \param out		Output data buffer.
+ *
+ * \retval >=0		length of output data.
+ * \retval KNOT_E*	if error.
+ */
+int32_t base32hex_decode_alloc(const uint8_t  *in,
+                               const uint32_t in_len,
+                               uint8_t        **out);
diff --git a/src/contrib/base64.c b/src/contrib/base64.c
new file mode 100644
index 0000000..a0d83a4
--- /dev/null
+++ b/src/contrib/base64.c
@@ -0,0 +1,272 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "contrib/base64.h"
+#include "libknot/errcode.h"
+
+#include <stdlib.h>
+#include <stdint.h>
+
+/*! \brief Maximal length of binary input to Base64 encoding. */
+#define MAX_BIN_DATA_LEN	((INT32_MAX / 4) * 3)
+
+/*! \brief Base64 padding character. */
+static const uint8_t base64_pad = '=';
+/*! \brief Base64 alphabet. */
+static const uint8_t base64_enc[] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+/*! \brief Indicates bad Base64 character. */
+#define KO	255
+/*! \brief Indicates Base64 padding character. */
+#define PD	 64
+
+/*! \brief Transformation and validation table for decoding Base64. */
+static const uint8_t base64_dec[256] = {
+	[  0] = KO, ['+'] = 62, ['V'] = 21, [129] = KO, [172] = KO, [215] = KO,
+	[  1] = KO, [ 44] = KO, ['W'] = 22, [130] = KO, [173] = KO, [216] = KO,
+	[  2] = KO, [ 45] = KO, ['X'] = 23, [131] = KO, [174] = KO, [217] = KO,
+	[  3] = KO, [ 46] = KO, ['Y'] = 24, [132] = KO, [175] = KO, [218] = KO,
+	[  4] = KO, ['/'] = 63, ['Z'] = 25, [133] = KO, [176] = KO, [219] = KO,
+	[  5] = KO, ['0'] = 52, [ 91] = KO, [134] = KO, [177] = KO, [220] = KO,
+	[  6] = KO, ['1'] = 53, [ 92] = KO, [135] = KO, [178] = KO, [221] = KO,
+	[  7] = KO, ['2'] = 54, [ 93] = KO, [136] = KO, [179] = KO, [222] = KO,
+	[  8] = KO, ['3'] = 55, [ 94] = KO, [137] = KO, [180] = KO, [223] = KO,
+	[  9] = KO, ['4'] = 56, [ 95] = KO, [138] = KO, [181] = KO, [224] = KO,
+	[ 10] = KO, ['5'] = 57, [ 96] = KO, [139] = KO, [182] = KO, [225] = KO,
+	[ 11] = KO, ['6'] = 58, ['a'] = 26, [140] = KO, [183] = KO, [226] = KO,
+	[ 12] = KO, ['7'] = 59, ['b'] = 27, [141] = KO, [184] = KO, [227] = KO,
+	[ 13] = KO, ['8'] = 60, ['c'] = 28, [142] = KO, [185] = KO, [228] = KO,
+	[ 14] = KO, ['9'] = 61, ['d'] = 29, [143] = KO, [186] = KO, [229] = KO,
+	[ 15] = KO, [ 58] = KO, ['e'] = 30, [144] = KO, [187] = KO, [230] = KO,
+	[ 16] = KO, [ 59] = KO, ['f'] = 31, [145] = KO, [188] = KO, [231] = KO,
+	[ 17] = KO, [ 60] = KO, ['g'] = 32, [146] = KO, [189] = KO, [232] = KO,
+	[ 18] = KO, ['='] = PD, ['h'] = 33, [147] = KO, [190] = KO, [233] = KO,
+	[ 19] = KO, [ 62] = KO, ['i'] = 34, [148] = KO, [191] = KO, [234] = KO,
+	[ 20] = KO, [ 63] = KO, ['j'] = 35, [149] = KO, [192] = KO, [235] = KO,
+	[ 21] = KO, [ 64] = KO, ['k'] = 36, [150] = KO, [193] = KO, [236] = KO,
+	[ 22] = KO, ['A'] =  0, ['l'] = 37, [151] = KO, [194] = KO, [237] = KO,
+	[ 23] = KO, ['B'] =  1, ['m'] = 38, [152] = KO, [195] = KO, [238] = KO,
+	[ 24] = KO, ['C'] =  2, ['n'] = 39, [153] = KO, [196] = KO, [239] = KO,
+	[ 25] = KO, ['D'] =  3, ['o'] = 40, [154] = KO, [197] = KO, [240] = KO,
+	[ 26] = KO, ['E'] =  4, ['p'] = 41, [155] = KO, [198] = KO, [241] = KO,
+	[ 27] = KO, ['F'] =  5, ['q'] = 42, [156] = KO, [199] = KO, [242] = KO,
+	[ 28] = KO, ['G'] =  6, ['r'] = 43, [157] = KO, [200] = KO, [243] = KO,
+	[ 29] = KO, ['H'] =  7, ['s'] = 44, [158] = KO, [201] = KO, [244] = KO,
+	[ 30] = KO, ['I'] =  8, ['t'] = 45, [159] = KO, [202] = KO, [245] = KO,
+	[ 31] = KO, ['J'] =  9, ['u'] = 46, [160] = KO, [203] = KO, [246] = KO,
+	[ 32] = KO, ['K'] = 10, ['v'] = 47, [161] = KO, [204] = KO, [247] = KO,
+	[ 33] = KO, ['L'] = 11, ['w'] = 48, [162] = KO, [205] = KO, [248] = KO,
+	[ 34] = KO, ['M'] = 12, ['x'] = 49, [163] = KO, [206] = KO, [249] = KO,
+	[ 35] = KO, ['N'] = 13, ['y'] = 50, [164] = KO, [207] = KO, [250] = KO,
+	[ 36] = KO, ['O'] = 14, ['z'] = 51, [165] = KO, [208] = KO, [251] = KO,
+	[ 37] = KO, ['P'] = 15, [123] = KO, [166] = KO, [209] = KO, [252] = KO,
+	[ 38] = KO, ['Q'] = 16, [124] = KO, [167] = KO, [210] = KO, [253] = KO,
+	[ 39] = KO, ['R'] = 17, [125] = KO, [168] = KO, [211] = KO, [254] = KO,
+	[ 40] = KO, ['S'] = 18, [126] = KO, [169] = KO, [212] = KO, [255] = KO,
+	[ 41] = KO, ['T'] = 19, [127] = KO, [170] = KO, [213] = KO,
+	[ 42] = KO, ['U'] = 20, [128] = KO, [171] = KO, [214] = KO,
+};
+
+int32_t base64_encode(const uint8_t  *in,
+                      const uint32_t in_len,
+                      uint8_t        *out,
+                      const uint32_t out_len)
+{
+	// Checking inputs.
+	if (in == NULL || out == NULL) {
+		return KNOT_EINVAL;
+	}
+	if (in_len > MAX_BIN_DATA_LEN || out_len < ((in_len + 2) / 3) * 4) {
+		return KNOT_ERANGE;
+	}
+
+	uint8_t		rest_len = in_len % 3;
+	const uint8_t	*stop = in + in_len - rest_len;
+	uint8_t		*text = out;
+
+	// Encoding loop takes 3 bytes and creates 4 characters.
+	while (in < stop) {
+		text[0] = base64_enc[in[0] >> 2];
+		text[1] = base64_enc[(in[0] & 0x03) << 4 | in[1] >> 4];
+		text[2] = base64_enc[(in[1] & 0x0F) << 2 | in[2] >> 6];
+		text[3] = base64_enc[in[2] & 0x3F];
+		text += 4;
+		in += 3;
+	}
+
+	// Processing of padding, if any.
+	switch (rest_len) {
+	case 2:
+		text[0] = base64_enc[in[0] >> 2];
+		text[1] = base64_enc[(in[0] & 0x03) << 4 | in[1] >> 4];
+		text[2] = base64_enc[(in[1] & 0x0F) << 2];
+		text[3] = base64_pad;
+		text += 4;
+		break;
+	case 1:
+		text[0] = base64_enc[in[0] >> 2];
+		text[1] = base64_enc[(in[0] & 0x03) << 4];
+		text[2] = base64_pad;
+		text[3] = base64_pad;
+		text += 4;
+		break;
+	}
+
+	return (text - out);
+}
+
+int32_t base64_encode_alloc(const uint8_t  *in,
+                            const uint32_t in_len,
+                            uint8_t        **out)
+{
+	// Checking inputs.
+	if (out == NULL) {
+		return KNOT_EINVAL;
+	}
+	if (in_len > MAX_BIN_DATA_LEN) {
+		return KNOT_ERANGE;
+	}
+
+	// Compute output buffer length.
+	uint32_t out_len = ((in_len + 2) / 3) * 4;
+
+	// Allocate output buffer.
+	*out = malloc(out_len);
+	if (*out == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	// Encode data.
+	int32_t ret = base64_encode(in, in_len, *out, out_len);
+	if (ret < 0) {
+		free(*out);
+		*out = NULL;
+	}
+
+	return ret;
+}
+
+int32_t base64_decode(const uint8_t  *in,
+                      const uint32_t in_len,
+                      uint8_t        *out,
+                      const uint32_t out_len)
+{
+	// Checking inputs.
+	if (in == NULL || out == NULL) {
+		return KNOT_EINVAL;
+	}
+	if (in_len > INT32_MAX || out_len < ((in_len + 3) / 4) * 3) {
+		return KNOT_ERANGE;
+	}
+	if ((in_len % 4) != 0) {
+		return KNOT_BASE64_ESIZE;
+	}
+
+	const uint8_t	*stop = in + in_len;
+	uint8_t		*bin = out;
+	uint8_t		pad_len = 0;
+	uint8_t		c1, c2, c3, c4;
+
+	// Decoding loop takes 4 characters and creates 3 bytes.
+	while (in < stop) {
+		// Filling and transforming 4 Base64 chars.
+		c1 = base64_dec[in[0]];
+		c2 = base64_dec[in[1]];
+		c3 = base64_dec[in[2]];
+		c4 = base64_dec[in[3]];
+
+		// Check 4. char if is bad or padding.
+		if (c4 >= PD) {
+			if (c4 == PD && pad_len == 0) {
+				pad_len = 1;
+			} else {
+				return KNOT_BASE64_ECHAR;
+			}
+		}
+
+		// Check 3. char if is bad or padding.
+		if (c3 >= PD) {
+			if (c3 == PD && pad_len == 1) {
+				pad_len = 2;
+			} else {
+				return KNOT_BASE64_ECHAR;
+			}
+		}
+
+		// Check 1. and 2. chars if are not padding.
+		if (c2 >= PD || c1 >= PD) {
+			return KNOT_BASE64_ECHAR;
+		}
+
+		// Computing of output data based on padding length.
+		switch (pad_len) {
+		case 0:
+			bin[2] = (c3 << 6) + c4;
+			// FALLTHROUGH
+		case 1:
+			bin[1] = (c2 << 4) + (c3 >> 2);
+			// FALLTHROUGH
+		case 2:
+			bin[0] = (c1 << 2) + (c2 >> 4);
+		}
+
+		// Update output end.
+		switch (pad_len) {
+		case 0:
+			bin += 3;
+			break;
+		case 1:
+			bin += 2;
+			break;
+		case 2:
+			bin += 1;
+			break;
+		}
+
+		in += 4;
+	}
+
+	return (bin - out);
+}
+
+int32_t base64_decode_alloc(const uint8_t  *in,
+                            const uint32_t in_len,
+                            uint8_t        **out)
+{
+	// Checking inputs.
+	if (out == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	// Compute output buffer length.
+	uint32_t out_len = ((in_len + 3) / 4) * 3;
+
+	// Allocate output buffer.
+	*out = malloc(out_len);
+	if (*out == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	// Decode data.
+	int32_t ret = base64_decode(in, in_len, *out, out_len);
+	if (ret < 0) {
+		free(*out);
+		*out = NULL;
+	}
+
+	return ret;
+}
diff --git a/src/contrib/base64.h b/src/contrib/base64.h
new file mode 100644
index 0000000..611574e
--- /dev/null
+++ b/src/contrib/base64.h
@@ -0,0 +1,102 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Base64 implementation (RFC 4648).
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+/*!
+ * \brief Encodes binary data using Base64.
+ *
+ * \note Output data buffer contains Base64 text string which isn't
+ *       terminated with '\0'!
+ *
+ * \param in		Input binary data.
+ * \param in_len	Length of input data.
+ * \param out		Output data buffer.
+ * \param out_len	Size of output buffer.
+ *
+ * \retval >=0		length of output string.
+ * \retval KNOT_E*	if error.
+ */
+int32_t base64_encode(const uint8_t  *in,
+                      const uint32_t in_len,
+                      uint8_t        *out,
+                      const uint32_t out_len);
+
+/*!
+ * \brief Encodes binary data using Base64 and output stores to own buffer.
+ *
+ * \note Output data buffer contains Base64 text string which isn't
+ *       terminated with '\0'!
+ *
+ * \note Output buffer should be deallocated after use.
+ *
+ * \param in		Input binary data.
+ * \param in_len	Length of input data.
+ * \param out		Output data buffer.
+ *
+ * \retval >=0		length of output string.
+ * \retval KNOT_E*	if error.
+ */
+int32_t base64_encode_alloc(const uint8_t  *in,
+                            const uint32_t in_len,
+                            uint8_t        **out);
+
+/*!
+ * \brief Decodes text data using Base64.
+ *
+ * \note Input data needn't be terminated with '\0'.
+ *
+ * \note Input data must be continuous Base64 string!
+ *
+ * \param in		Input text data.
+ * \param in_len	Length of input string.
+ * \param out		Output data buffer.
+ * \param out_len	Size of output buffer.
+ *
+ * \retval >=0		length of output data.
+ * \retval KNOT_E*	if error.
+ */
+int32_t base64_decode(const uint8_t  *in,
+                      const uint32_t in_len,
+                      uint8_t        *out,
+                      const uint32_t out_len);
+
+/*!
+ * \brief Decodes text data using Base64 and output stores to own buffer.
+ *
+ * \note Input data needn't be terminated with '\0'.
+ *
+ * \note Input data must be continuous Base64 string!
+ *
+ * \note Output buffer should be deallocated after use.
+ *
+ * \param in		Input text data.
+ * \param in_len	Length of input string.
+ * \param out		Output data buffer.
+ *
+ * \retval >=0		length of output data.
+ * \retval KNOT_E*	if error.
+ */
+int32_t base64_decode_alloc(const uint8_t  *in,
+                            const uint32_t in_len,
+                            uint8_t        **out);
+
+/*! @} */
diff --git a/src/contrib/ctype.h b/src/contrib/ctype.h
new file mode 100644
index 0000000..93b85db
--- /dev/null
+++ b/src/contrib/ctype.h
@@ -0,0 +1,192 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Locale-independent ctype functions.
+ */
+
+#pragma once
+
+#include <ctype.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+enum {
+	CT_DIGIT = 1 << 0,
+	CT_UPPER = 1 << 1,
+	CT_LOWER = 1 << 2,
+	CT_XDIGT = 1 << 3,
+	CT_PUNCT = 1 << 4,
+	CT_PRINT = 1 << 5,
+	CT_SPACE = 1 << 6,
+};
+
+static const uint8_t char_mask[256] = {
+	// 0 - 8
+	['\t'] = CT_SPACE,
+	['\n'] = CT_SPACE,
+	['\v'] = CT_SPACE,
+	['\f'] = CT_SPACE,
+	['\r'] = CT_SPACE,
+	// 14 - 31
+	[' ']  = CT_PRINT | CT_SPACE,
+
+	['!']  = CT_PRINT | CT_PUNCT,
+	['"']  = CT_PRINT | CT_PUNCT,
+	['#']  = CT_PRINT | CT_PUNCT,
+	['$']  = CT_PRINT | CT_PUNCT,
+	['%']  = CT_PRINT | CT_PUNCT,
+	['&']  = CT_PRINT | CT_PUNCT,
+	['\''] = CT_PRINT | CT_PUNCT,
+	['(']  = CT_PRINT | CT_PUNCT,
+	[')']  = CT_PRINT | CT_PUNCT,
+	['*']  = CT_PRINT | CT_PUNCT,
+	['+']  = CT_PRINT | CT_PUNCT,
+	[',']  = CT_PRINT | CT_PUNCT,
+	['-']  = CT_PRINT | CT_PUNCT,
+	['.']  = CT_PRINT | CT_PUNCT,
+	['/']  = CT_PRINT | CT_PUNCT,
+
+	['0']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['1']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['2']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['3']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['4']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['5']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['6']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['7']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['8']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+	['9']  = CT_PRINT | CT_DIGIT | CT_XDIGT,
+
+	[':']  = CT_PRINT | CT_PUNCT,
+	[';']  = CT_PRINT | CT_PUNCT,
+	['<']  = CT_PRINT | CT_PUNCT,
+	['=']  = CT_PRINT | CT_PUNCT,
+	['>']  = CT_PRINT | CT_PUNCT,
+	['?']  = CT_PRINT | CT_PUNCT,
+	['@']  = CT_PRINT | CT_PUNCT,
+
+	['A']  = CT_PRINT | CT_UPPER | CT_XDIGT,
+	['B']  = CT_PRINT | CT_UPPER | CT_XDIGT,
+	['C']  = CT_PRINT | CT_UPPER | CT_XDIGT,
+	['D']  = CT_PRINT | CT_UPPER | CT_XDIGT,
+	['E']  = CT_PRINT | CT_UPPER | CT_XDIGT,
+	['F']  = CT_PRINT | CT_UPPER | CT_XDIGT,
+	['G']  = CT_PRINT | CT_UPPER,
+	['H']  = CT_PRINT | CT_UPPER,
+	['I']  = CT_PRINT | CT_UPPER,
+	['J']  = CT_PRINT | CT_UPPER,
+	['K']  = CT_PRINT | CT_UPPER,
+	['L']  = CT_PRINT | CT_UPPER,
+	['M']  = CT_PRINT | CT_UPPER,
+	['N']  = CT_PRINT | CT_UPPER,
+	['O']  = CT_PRINT | CT_UPPER,
+	['P']  = CT_PRINT | CT_UPPER,
+	['Q']  = CT_PRINT | CT_UPPER,
+	['R']  = CT_PRINT | CT_UPPER,
+	['S']  = CT_PRINT | CT_UPPER,
+	['T']  = CT_PRINT | CT_UPPER,
+	['U']  = CT_PRINT | CT_UPPER,
+	['V']  = CT_PRINT | CT_UPPER,
+	['W']  = CT_PRINT | CT_UPPER,
+	['X']  = CT_PRINT | CT_UPPER,
+	['Y']  = CT_PRINT | CT_UPPER,
+	['Z']  = CT_PRINT | CT_UPPER,
+
+	['[']  = CT_PRINT | CT_PUNCT,
+	['\\'] = CT_PRINT | CT_PUNCT,
+	[']']  = CT_PRINT | CT_PUNCT,
+	['^']  = CT_PRINT | CT_PUNCT,
+	['_']  = CT_PRINT | CT_PUNCT,
+	['`']  = CT_PRINT | CT_PUNCT,
+
+	['a']  = CT_PRINT | CT_LOWER | CT_XDIGT,
+	['b']  = CT_PRINT | CT_LOWER | CT_XDIGT,
+	['c']  = CT_PRINT | CT_LOWER | CT_XDIGT,
+	['d']  = CT_PRINT | CT_LOWER | CT_XDIGT,
+	['e']  = CT_PRINT | CT_LOWER | CT_XDIGT,
+	['f']  = CT_PRINT | CT_LOWER | CT_XDIGT,
+	['g']  = CT_PRINT | CT_LOWER,
+	['h']  = CT_PRINT | CT_LOWER,
+	['i']  = CT_PRINT | CT_LOWER,
+	['j']  = CT_PRINT | CT_LOWER,
+	['k']  = CT_PRINT | CT_LOWER,
+	['l']  = CT_PRINT | CT_LOWER,
+	['m']  = CT_PRINT | CT_LOWER,
+	['n']  = CT_PRINT | CT_LOWER,
+	['o']  = CT_PRINT | CT_LOWER,
+	['p']  = CT_PRINT | CT_LOWER,
+	['q']  = CT_PRINT | CT_LOWER,
+	['r']  = CT_PRINT | CT_LOWER,
+	['s']  = CT_PRINT | CT_LOWER,
+	['t']  = CT_PRINT | CT_LOWER,
+	['u']  = CT_PRINT | CT_LOWER,
+	['v']  = CT_PRINT | CT_LOWER,
+	['w']  = CT_PRINT | CT_LOWER,
+	['x']  = CT_PRINT | CT_LOWER,
+	['y']  = CT_PRINT | CT_LOWER,
+	['z']  = CT_PRINT | CT_LOWER,
+
+	['{']  = CT_PRINT | CT_PUNCT,
+	['|']  = CT_PRINT | CT_PUNCT,
+	['}']  = CT_PRINT | CT_PUNCT,
+	['~']  = CT_PRINT | CT_PUNCT,
+	// 127 - 255
+};
+
+static inline bool is_alnum(uint8_t c)
+{
+	return char_mask[c] & (CT_DIGIT | CT_UPPER | CT_LOWER);
+}
+
+static inline bool is_alpha(uint8_t c)
+{
+	return char_mask[c] & (CT_UPPER | CT_LOWER);
+}
+
+static inline bool is_digit(uint8_t c)
+{
+	return char_mask[c] & CT_DIGIT;
+}
+
+static inline bool is_xdigit(uint8_t c)
+{
+	return char_mask[c] & CT_XDIGT;
+}
+
+static inline bool is_lower(uint8_t c)
+{
+	return char_mask[c] & CT_LOWER;
+}
+
+static inline bool is_upper(uint8_t c)
+{
+	return char_mask[c] & CT_UPPER;
+}
+
+static inline bool is_print(uint8_t c)
+{
+	return char_mask[c] & CT_PRINT;
+}
+
+static inline bool is_punct(uint8_t c)
+{
+	return char_mask[c] & CT_PUNCT;
+}
+
+static inline bool is_space(uint8_t c)
+{
+	return char_mask[c] & CT_SPACE;
+}
diff --git a/src/contrib/dnstap/convert.c b/src/contrib/dnstap/convert.c
new file mode 100644
index 0000000..f59bacd
--- /dev/null
+++ b/src/contrib/dnstap/convert.c
@@ -0,0 +1,142 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+
+#include "contrib/dnstap/convert.h"
+#include "contrib/dnstap/dnstap.pb-c.h"
+
+/*!
+ * \brief Translation between real and Dnstap value.
+ */
+typedef struct mapping {
+	int real;
+	int dnstap;
+} mapping_t;
+
+/*!
+ * \brief Mapping for network family.
+ */
+static const mapping_t SOCKET_FAMILY_MAPPING[] = {
+	{ AF_INET,  DNSTAP__SOCKET_FAMILY__INET },
+	{ AF_INET6, DNSTAP__SOCKET_FAMILY__INET6 },
+	{ 0 }
+};
+
+/*!
+ * \brief Mapping from network protocol.
+ */
+static const mapping_t SOCKET_PROTOCOL_MAPPING[] = {
+	{ IPPROTO_UDP, DNSTAP__SOCKET_PROTOCOL__UDP },
+	{ IPPROTO_TCP, DNSTAP__SOCKET_PROTOCOL__TCP },
+	{ 0 }
+};
+
+/*!
+ * \brief Get Dnstap value for a given real value.
+ */
+static int encode(const mapping_t *mapping, int real)
+{
+	for (const mapping_t *m = mapping; m->real != 0; m += 1) {
+		if (m->real == real) {
+			return m->dnstap;
+		}
+	}
+
+	return 0;
+}
+
+/*!
+ * \brief Get real value for a given Dnstap value.
+ */
+static int decode(const mapping_t *mapping, int dnstap)
+{
+	for (const mapping_t *m = mapping; m->real != 0; m += 1) {
+		if (m->dnstap == dnstap) {
+			return m->real;
+		}
+	}
+
+	return 0;
+}
+
+/* -- public API ----------------------------------------------------------- */
+
+Dnstap__SocketFamily dt_family_encode(int family)
+{
+	return encode(SOCKET_FAMILY_MAPPING, family);
+}
+
+int dt_family_decode(Dnstap__SocketFamily dnstap_family)
+{
+	return decode(SOCKET_FAMILY_MAPPING, dnstap_family);
+}
+
+Dnstap__SocketProtocol dt_protocol_encode(int protocol)
+{
+	return encode(SOCKET_PROTOCOL_MAPPING, protocol);
+}
+
+int dt_protocol_decode(Dnstap__SocketProtocol dnstap_protocol)
+{
+	return decode(SOCKET_PROTOCOL_MAPPING, dnstap_protocol);
+}
+
+bool dt_message_type_is_query(Dnstap__Message__Type type)
+{
+	switch (type) {
+	case DNSTAP__MESSAGE__TYPE__AUTH_QUERY:
+	case DNSTAP__MESSAGE__TYPE__CLIENT_QUERY:
+	case DNSTAP__MESSAGE__TYPE__FORWARDER_QUERY:
+	case DNSTAP__MESSAGE__TYPE__RESOLVER_QUERY:
+	case DNSTAP__MESSAGE__TYPE__STUB_QUERY:
+	case DNSTAP__MESSAGE__TYPE__TOOL_QUERY:
+		return true;
+	default:
+		return false;
+	}
+}
+
+bool dt_message_type_is_response(Dnstap__Message__Type type)
+{
+	switch (type) {
+	case DNSTAP__MESSAGE__TYPE__AUTH_RESPONSE:
+	case DNSTAP__MESSAGE__TYPE__CLIENT_RESPONSE:
+	case DNSTAP__MESSAGE__TYPE__FORWARDER_RESPONSE:
+	case DNSTAP__MESSAGE__TYPE__RESOLVER_RESPONSE:
+	case DNSTAP__MESSAGE__TYPE__STUB_RESPONSE:
+	case DNSTAP__MESSAGE__TYPE__TOOL_RESPONSE:
+		return true;
+	default:
+		return false;
+	}
+}
+
+bool dt_message_role_is_initiator(Dnstap__Message__Type type)
+{
+	switch (type) {
+	case DNSTAP__MESSAGE__TYPE__AUTH_QUERY:
+	case DNSTAP__MESSAGE__TYPE__AUTH_RESPONSE:
+	case DNSTAP__MESSAGE__TYPE__CLIENT_QUERY:
+	case DNSTAP__MESSAGE__TYPE__CLIENT_RESPONSE:
+		return false;
+	default:
+		return true;
+	}
+}
diff --git a/src/contrib/dnstap/convert.h b/src/contrib/dnstap/convert.h
new file mode 100644
index 0000000..bf00ffb
--- /dev/null
+++ b/src/contrib/dnstap/convert.h
@@ -0,0 +1,59 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Dnstap identifiers conversions.
+ */
+
+#pragma once
+
+#include <stdbool.h>
+
+#include "contrib/dnstap/dnstap.pb-c.h"
+
+/*!
+ * \brief Get Dnstap socket family from the real one.
+ */
+Dnstap__SocketFamily dt_family_encode(int family);
+
+/*!
+ * \brief Get real socket family from the Dnstap one.
+ */
+int dt_family_decode(Dnstap__SocketFamily dnstap_family);
+
+/*!
+ * \brief Get Dnstap protocol from a real one.
+ */
+Dnstap__SocketProtocol dt_protocol_encode(int protocol);
+
+/*!
+ * \brief Get real protocol from the Dnstap one.
+ */
+int dt_protocol_decode(Dnstap__SocketProtocol dnstap_protocol);
+
+/*!
+ * Check if a message type is any type of a query.
+ */
+bool dt_message_type_is_query(Dnstap__Message__Type type);
+
+/*!
+ * Check if a message type is any type of a response.
+ */
+bool dt_message_type_is_response(Dnstap__Message__Type type);
+
+/*!
+ * Check if a message role is any type of an initiator.
+ */
+bool dt_message_role_is_initiator(Dnstap__Message__Type type);
diff --git a/src/contrib/dnstap/dnstap.c b/src/contrib/dnstap/dnstap.c
new file mode 100644
index 0000000..9e24eac
--- /dev/null
+++ b/src/contrib/dnstap/dnstap.c
@@ -0,0 +1,40 @@
+/*  Copyright (C) 2014 Farsight Security, Inc. <software@farsightsecurity.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "contrib/dnstap/dnstap.pb-c.h"
+
+#define DNSTAP_INITIAL_BUF_SIZE         256
+
+uint8_t* dt_pack(const Dnstap__Dnstap *d, uint8_t **buf, size_t *sz)
+{
+	ProtobufCBufferSimple sbuf = { { NULL } };
+
+	sbuf.base.append = protobuf_c_buffer_simple_append;
+	sbuf.len = 0;
+	sbuf.alloced = DNSTAP_INITIAL_BUF_SIZE;
+	sbuf.data = malloc(sbuf.alloced);
+	if (sbuf.data == NULL) {
+		return NULL;
+	}
+	sbuf.must_free_data = 1;
+
+	*sz = dnstap__dnstap__pack_to_buffer(d, (ProtobufCBuffer *) &sbuf);
+	*buf = sbuf.data;
+	return *buf;
+}
diff --git a/src/contrib/dnstap/dnstap.h b/src/contrib/dnstap/dnstap.h
new file mode 100644
index 0000000..41e5f65
--- /dev/null
+++ b/src/contrib/dnstap/dnstap.h
@@ -0,0 +1,46 @@
+/*  Copyright (C) 2014 Farsight Security, Inc. <software@farsightsecurity.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \author Robert Edmonds <edmonds@fsi.io>
+ *
+ * \brief Public interface for dnstap.
+ */
+
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "contrib/dnstap/dnstap.pb-c.h"
+
+/*! \brief Frame Streams "Content Type" value for dnstap. */
+#define DNSTAP_CONTENT_TYPE     "protobuf:dnstap.Dnstap"
+
+/*!
+ * \brief Serializes a filled out dnstap protobuf struct. Dynamically allocates
+ * storage for the serialized frame.
+ *
+ * \note This function returns a copy of its parameter return value 'buf' to
+ * make error checking slightly easier.
+ *
+ * \param d             dnstap protobuf struct.
+ * \param[out] buf      Serialized frame.
+ * \param[out] sz       Size in bytes of the serialized frame.
+ *
+ * \return              Serialized frame.
+ * \retval NULL         if error.
+ */
+uint8_t* dt_pack(const Dnstap__Dnstap *d, uint8_t **buf, size_t *sz);
diff --git a/src/contrib/dnstap/dnstap.proto b/src/contrib/dnstap/dnstap.proto
new file mode 100644
index 0000000..ea5c77a
--- /dev/null
+++ b/src/contrib/dnstap/dnstap.proto
@@ -0,0 +1,270 @@
+// dnstap: flexible, structured event replication format for DNS software
+//
+// This file contains the protobuf schemas for the "dnstap" structured event
+// replication format for DNS software.
+
+// Written in 2013-2014 by Farsight Security, Inc.
+//
+// To the extent possible under law, the author(s) have dedicated all
+// copyright and related and neighboring rights to this file to the public
+// domain worldwide. This file is distributed without any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication along
+// with this file. If not, see:
+//
+// <http://creativecommons.org/publicdomain/zero/1.0/>.
+
+syntax = "proto2";
+
+package dnstap;
+
+// "Dnstap": this is the top-level dnstap type, which is a "union" type that
+// contains other kinds of dnstap payloads, although currently only one type
+// of dnstap payload is defined.
+// See: https://developers.google.com/protocol-buffers/docs/techniques#union
+message Dnstap {
+    // DNS server identity.
+    // If enabled, this is the identity string of the DNS server which generated
+    // this message. Typically this would be the same string as returned by an
+    // "NSID" (RFC 5001) query.
+    optional bytes      identity = 1;
+
+    // DNS server version.
+    // If enabled, this is the version string of the DNS server which generated
+    // this message. Typically this would be the same string as returned by a
+    // "version.bind" query.
+    optional bytes      version = 2;
+
+    // Extra data for this payload.
+    // This field can be used for adding an arbitrary byte-string annotation to
+    // the payload. No encoding or interpretation is applied or enforced.
+    optional bytes      extra = 3;
+
+    // Identifies which field below is filled in.
+    enum Type {
+        MESSAGE = 1;
+    }
+    required Type       type = 15;
+
+    // One of the following will be filled in.
+    optional Message    message = 14;
+}
+
+// SocketFamily: the network protocol family of a socket. This specifies how
+// to interpret "network address" fields.
+enum SocketFamily {
+    INET = 1;   // IPv4 (RFC 791)
+    INET6 = 2;  // IPv6 (RFC 2460)
+}
+
+// SocketProtocol: the transport protocol of a socket. This specifies how to
+// interpret "transport port" fields.
+enum SocketProtocol {
+    UDP = 1;    // User Datagram Protocol (RFC 768)
+    TCP = 2;    // Transmission Control Protocol (RFC 793)
+}
+
+// Message: a wire-format (RFC 1035 section 4) DNS message and associated
+// metadata. Applications generating "Message" payloads should follow
+// certain requirements based on the MessageType, see below.
+message Message {
+
+    // There are eight types of "Message" defined that correspond to the
+    // four arrows in the following diagram, slightly modified from RFC 1035
+    // section 2:
+
+    //    +---------+               +----------+           +--------+
+    //    |         |     query     |          |   query   |        |
+    //    | Stub    |-SQ--------CQ->| Recursive|-RQ----AQ->| Auth.  |
+    //    | Resolver|               | Server   |           | Name   |
+    //    |         |<-SR--------CR-|          |<-RR----AR-| Server |
+    //    +---------+    response   |          |  response |        |
+    //                              +----------+           +--------+
+
+    // Each arrow has two Type values each, one for each "end" of each arrow,
+    // because these are considered to be distinct events. Each end of each
+    // arrow on the diagram above has been marked with a two-letter Type
+    // mnemonic. Clockwise from upper left, these mnemonic values are:
+    //
+    //   SQ:        STUB_QUERY
+    //   CQ:      CLIENT_QUERY
+    //   RQ:    RESOLVER_QUERY
+    //   AQ:        AUTH_QUERY
+    //   AR:        AUTH_RESPONSE
+    //   RR:    RESOLVER_RESPONSE
+    //   CR:      CLIENT_RESPONSE
+    //   SR:        STUB_RESPONSE
+
+    // Two additional types of "Message" have been defined for the
+    // "forwarding" case where an upstream DNS server is responsible for
+    // further recursion. These are not shown on the diagram above, but have
+    // the following mnemonic values:
+
+    //   FQ:   FORWARDER_QUERY
+    //   FR:   FORWARDER_RESPONSE
+
+    // The "Message" Type values are defined below.
+
+    enum Type {
+        // AUTH_QUERY is a DNS query message received from a resolver by an
+        // authoritative name server, from the perspective of the authoritative
+        // name server.
+        AUTH_QUERY = 1;
+
+        // AUTH_RESPONSE is a DNS response message sent from an authoritative
+        // name server to a resolver, from the perspective of the authoritative
+        // name server.
+        AUTH_RESPONSE = 2;
+
+        // RESOLVER_QUERY is a DNS query message sent from a resolver to an
+        // authoritative name server, from the perspective of the resolver.
+        // Resolvers typically clear the RD (recursion desired) bit when
+        // sending queries.
+        RESOLVER_QUERY = 3;
+
+        // RESOLVER_RESPONSE is a DNS response message received from an
+        // authoritative name server by a resolver, from the perspective of
+        // the resolver.
+        RESOLVER_RESPONSE = 4;
+
+        // CLIENT_QUERY is a DNS query message sent from a client to a DNS
+        // server which is expected to perform further recursion, from the
+        // perspective of the DNS server. The client may be a stub resolver or
+        // forwarder or some other type of software which typically sets the RD
+        // (recursion desired) bit when querying the DNS server. The DNS server
+        // may be a simple forwarding proxy or it may be a full recursive
+        // resolver.
+        CLIENT_QUERY = 5;
+
+        // CLIENT_RESPONSE is a DNS response message sent from a DNS server to
+        // a client, from the perspective of the DNS server. The DNS server
+        // typically sets the RA (recursion available) bit when responding.
+        CLIENT_RESPONSE = 6;
+
+        // FORWARDER_QUERY is a DNS query message sent from a downstream DNS
+        // server to an upstream DNS server which is expected to perform
+        // further recursion, from the perspective of the downstream DNS
+        // server.
+        FORWARDER_QUERY = 7;
+
+        // FORWARDER_RESPONSE is a DNS response message sent from an upstream
+        // DNS server performing recursion to a downstream DNS server, from the
+        // perspective of the downstream DNS server.
+        FORWARDER_RESPONSE = 8;
+
+        // STUB_QUERY is a DNS query message sent from a stub resolver to a DNS
+        // server, from the perspective of the stub resolver.
+        STUB_QUERY = 9;
+
+        // STUB_RESPONSE is a DNS response message sent from a DNS server to a
+        // stub resolver, from the perspective of the stub resolver.
+        STUB_RESPONSE = 10;
+
+        // TOOL_QUERY is a DNS query message sent from a DNS software tool to a
+        // DNS server, from the perspective of the tool.
+        TOOL_QUERY = 11;
+
+        // TOOL_RESPONSE is a DNS response message received by a DNS software
+        // tool from a DNS server, from the perspective of the tool.
+        TOOL_RESPONSE = 12;
+    }
+
+    // One of the Type values described above.
+    required Type               type = 1;
+
+    // One of the SocketFamily values described above.
+    optional SocketFamily       socket_family = 2;
+
+    // One of the SocketProtocol values described above.
+    optional SocketProtocol     socket_protocol = 3;
+
+    // The network address of the message initiator.
+    // For SocketFamily INET, this field is 4 octets (IPv4 address).
+    // For SocketFamily INET6, this field is 16 octets (IPv6 address).
+    optional bytes              query_address = 4;
+
+    // The network address of the message responder.
+    // For SocketFamily INET, this field is 4 octets (IPv4 address).
+    // For SocketFamily INET6, this field is 16 octets (IPv6 address).
+    optional bytes              response_address = 5;
+
+    // The transport port of the message initiator.
+    // This is a 16-bit UDP or TCP port number, depending on SocketProtocol.
+    optional uint32             query_port = 6;
+
+    // The transport port of the message responder.
+    // This is a 16-bit UDP or TCP port number, depending on SocketProtocol.
+    optional uint32             response_port = 7;
+
+    // The time at which the DNS query message was sent or received, depending
+    // on whether this is an AUTH_QUERY, RESOLVER_QUERY, or CLIENT_QUERY.
+    // This is the number of seconds since the UNIX epoch.
+    optional uint64             query_time_sec = 8;
+
+    // The time at which the DNS query message was sent or received.
+    // This is the seconds fraction, expressed as a count of nanoseconds.
+    optional fixed32            query_time_nsec = 9;
+
+    // The initiator's original wire-format DNS query message, verbatim.
+    optional bytes              query_message = 10;
+
+    // The "zone" or "bailiwick" pertaining to the DNS query message.
+    // This is a wire-format DNS domain name.
+    optional bytes              query_zone = 11;
+
+    // The time at which the DNS response message was sent or received,
+    // depending on whether this is an AUTH_RESPONSE, RESOLVER_RESPONSE, or
+    // CLIENT_RESPONSE.
+    // This is the number of seconds since the UNIX epoch.
+    optional uint64             response_time_sec = 12;
+
+    // The time at which the DNS response message was sent or received.
+    // This is the seconds fraction, expressed as a count of nanoseconds.
+    optional fixed32            response_time_nsec = 13;
+
+    // The responder's original wire-format DNS response message, verbatim.
+    optional bytes              response_message = 14;
+}
+
+// All fields except for 'type' in the Message schema are optional.
+// It is recommended that at least the following fields be filled in for
+// particular types of Messages.
+
+// AUTH_QUERY:
+//      socket_family, socket_protocol
+//      query_address, query_port
+//      query_message
+//      query_time_sec, query_time_nsec
+
+// AUTH_RESPONSE:
+//      socket_family, socket_protocol
+//      query_address, query_port
+//      query_time_sec, query_time_nsec
+//      response_message
+//      response_time_sec, response_time_nsec
+
+// RESOLVER_QUERY:
+//      socket_family, socket_protocol
+//      query_message
+//      query_time_sec, query_time_nsec
+//      query_zone
+//      response_address, response_port
+
+// RESOLVER_RESPONSE:
+//      socket_family, socket_protocol
+//      query_time_sec, query_time_nsec
+//      query_zone
+//      response_address, response_port
+//      response_message
+//      response_time_sec, response_time_nsec
+
+// CLIENT_QUERY:
+//      socket_family, socket_protocol
+//      query_message
+//      query_time_sec, query_time_nsec
+
+// CLIENT_RESPONSE:
+//      socket_family, socket_protocol
+//      query_time_sec, query_time_nsec
+//      response_message
+//      response_time_sec, response_time_nsec
diff --git a/src/contrib/dnstap/message.c b/src/contrib/dnstap/message.c
new file mode 100644
index 0000000..0b41e9d
--- /dev/null
+++ b/src/contrib/dnstap/message.c
@@ -0,0 +1,130 @@
+/*  Copyright (C) 2017 Farsight Security, Inc. <software@farsightsecurity.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <netinet/in.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "libknot/errcode.h"
+
+#include "contrib/dnstap/convert.h"
+#include "contrib/dnstap/message.h"
+
+static void set_address(const struct sockaddr *sockaddr,
+                        ProtobufCBinaryData   *addr,
+                        protobuf_c_boolean    *has_addr,
+                        uint32_t              *port,
+                        protobuf_c_boolean    *has_port)
+{
+	if (sockaddr == NULL) {
+		*has_addr = 0;
+		*has_port = 0;
+		return;
+	}
+
+	*has_addr = 1;
+	*has_port = 1;
+
+	if (sockaddr->sa_family == AF_INET) {
+		const struct sockaddr_in *sai;
+		sai = (const struct sockaddr_in *)sockaddr;
+		addr->len = sizeof(sai->sin_addr);
+		addr->data = (uint8_t *)&sai->sin_addr.s_addr;
+		*port = ntohs(sai->sin_port);
+	} else if (sockaddr->sa_family == AF_INET6) {
+		const struct sockaddr_in6 *sai6;
+		sai6 = (const struct sockaddr_in6 *)sockaddr;
+		addr->len = sizeof(sai6->sin6_addr);
+		addr->data = (uint8_t *)&sai6->sin6_addr.s6_addr;
+		*port = ntohs(sai6->sin6_port);
+	}
+}
+
+static int get_family(const struct sockaddr *query_sa,
+	              const struct sockaddr *response_sa)
+{
+	const struct sockaddr *source = query_sa ? query_sa : response_sa;
+	if (source == NULL) {
+		return 0;
+	}
+
+	return dt_family_encode(source->sa_family);
+}
+
+int dt_message_fill(Dnstap__Message             *m,
+                    const Dnstap__Message__Type type,
+                    const struct sockaddr       *query_sa,
+                    const struct sockaddr       *response_sa,
+                    const int                   protocol,
+                    const void                  *wire,
+                    const size_t                len_wire,
+                    const struct timespec       *mtime)
+{
+	if (m == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	memset(m, 0, sizeof(*m));
+
+	m->base.descriptor = &dnstap__message__descriptor;
+
+	// Message.type
+	m->type = type;
+
+	// Message.socket_family
+	m->socket_family = get_family(query_sa, response_sa);
+	m->has_socket_family = m->socket_family != 0;
+
+	// Message.socket_protocol
+	m->socket_protocol = dt_protocol_encode(protocol);
+	m->has_socket_protocol = m->socket_protocol != 0;
+
+	// Message addresses
+	set_address(query_sa, &m->query_address, &m->has_query_address,
+	            &m->query_port, &m->has_query_port);
+	set_address(response_sa, &m->response_address, &m->has_response_address,
+	            &m->response_port, &m->has_response_port);
+
+	if (dt_message_type_is_query(type)) {
+		// Message.query_message
+		m->query_message.len = len_wire;
+		m->query_message.data = (uint8_t *)wire;
+		m->has_query_message = 1;
+		// Message.query_time_sec, Message.query_time_nsec
+		if (mtime != NULL) {
+			m->query_time_sec = mtime->tv_sec;
+			m->query_time_nsec = mtime->tv_nsec;
+			m->has_query_time_sec = 1;
+			m->has_query_time_nsec = 1;
+		}
+	} else if (dt_message_type_is_response(type)) {
+		// Message.response_message
+		m->response_message.len = len_wire;
+		m->response_message.data = (uint8_t *)wire;
+		m->has_response_message = 1;
+		// Message.response_time_sec, Message.response_time_nsec
+		if (mtime != NULL) {
+			m->response_time_sec = mtime->tv_sec;
+			m->response_time_nsec = mtime->tv_nsec;
+			m->has_response_time_sec = 1;
+			m->has_response_time_nsec = 1;
+		}
+	}
+
+	return KNOT_EOK;
+}
diff --git a/src/contrib/dnstap/message.h b/src/contrib/dnstap/message.h
new file mode 100644
index 0000000..11a967d
--- /dev/null
+++ b/src/contrib/dnstap/message.h
@@ -0,0 +1,62 @@
+/*  Copyright (C) 2017 Farsight Security, Inc. <software@farsightsecurity.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \author Robert Edmonds <edmonds@fsi.io>
+ *
+ * \brief Dnstap message interface.
+ */
+
+#pragma once
+
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <stddef.h>
+
+#include "contrib/dnstap/dnstap.pb-c.h"
+
+/*!
+ * \brief Fill a Dnstap__Message structure with the given parameters.
+ *
+ * \param[out] m
+ *      Dnstap__Message structure to fill. Will be zeroed first.
+ * \param type
+ *      One of the DNSTAP__MESSAGE__TYPE__* values.
+ * \param query_sa
+ *      sockaddr_in or sockaddr_in6 to use when filling the 'socket_family',
+ *      'query_address', 'query_port' fields.
+ * \param response_sa
+ *      sockaddr_in or sockaddr_in6 to use when filling the 'socket_family',
+ *      'response_address', 'response_port' fields.
+ * \param protocol
+ *      \c IPPROTO_UDP or \c IPPROTO_TCP.
+ * \param wire
+ *	Wire-format query message or response message (depending on 'type').
+ * \param len_wire
+ *	Length in bytes of 'wire'.
+ * \param mtime
+ *	Message time. May be NULL.
+ *
+ * \retval KNOT_EOK
+ * \retval KNOT_EINVAL
+ */
+int dt_message_fill(Dnstap__Message             *m,
+                    const Dnstap__Message__Type type,
+                    const struct sockaddr       *query_sa,
+                    const struct sockaddr       *response_sa,
+                    const int                   protocol,
+                    const void                  *wire,
+                    const size_t                len_wire,
+                    const struct timespec       *mtime);
diff --git a/src/contrib/dnstap/reader.c b/src/contrib/dnstap/reader.c
new file mode 100644
index 0000000..593c6ec
--- /dev/null
+++ b/src/contrib/dnstap/reader.c
@@ -0,0 +1,105 @@
+/*  Copyright (C) 2014 Farsight Security, Inc. <software@farsightsecurity.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "libknot/errcode.h"
+
+#include "contrib/macros.h"
+#include "contrib/dnstap/dnstap.h"
+#include "contrib/dnstap/reader.h"
+
+dt_reader_t* dt_reader_create(const char *file_path)
+{
+	struct fstrm_file_options *fopt = NULL;
+	struct fstrm_reader_options *ropt = NULL;
+	dt_reader_t *reader = NULL;
+	fstrm_res res;
+
+	reader = calloc(1, sizeof(dt_reader_t));
+	if (reader == NULL) {
+		goto fail;
+	}
+
+	// Open reader.
+	fopt = fstrm_file_options_init();
+	fstrm_file_options_set_file_path(fopt, file_path);
+	ropt = fstrm_reader_options_init();
+	fstrm_reader_options_add_content_type(ropt,
+		(const uint8_t *) DNSTAP_CONTENT_TYPE,
+		strlen(DNSTAP_CONTENT_TYPE));
+	reader->fr = fstrm_file_reader_init(fopt, ropt);
+	fstrm_file_options_destroy(&fopt);
+	fstrm_reader_options_destroy(&ropt);
+	if (reader->fr == NULL) {
+		goto fail;
+	}
+	res = fstrm_reader_open(reader->fr);
+	if (res != fstrm_res_success) {
+		goto fail;
+	}
+
+	return reader;
+fail:
+	dt_reader_free(reader);
+	return NULL;
+}
+
+void dt_reader_free(dt_reader_t *reader)
+{
+	if (reader == NULL) {
+		return;
+	}
+
+	fstrm_reader_destroy(&reader->fr);
+	free(reader);
+}
+
+int dt_reader_read(dt_reader_t *reader, Dnstap__Dnstap **d)
+{
+	fstrm_res res;
+	const uint8_t *data = NULL;
+	size_t len = 0;
+
+	res = fstrm_reader_read(reader->fr, &data, &len);
+	if (res == fstrm_res_success) {
+		*d = dnstap__dnstap__unpack(NULL, len, data);
+		if (*d == NULL) {
+			return KNOT_ENOMEM;
+		}
+	} else if (res == fstrm_res_failure) {
+		return KNOT_ERROR;
+	} else if (res == fstrm_res_stop) {
+		return KNOT_EOF;
+	}
+
+	return KNOT_EOK;
+}
+
+void dt_reader_free_frame(dt_reader_t *reader, Dnstap__Dnstap **frame_ptr)
+{
+	if (!*frame_ptr) {
+		return;
+	}
+
+	UNUSED(reader);
+
+	dnstap__dnstap__free_unpacked(*frame_ptr, NULL);
+	*frame_ptr = NULL;
+}
diff --git a/src/contrib/dnstap/reader.h b/src/contrib/dnstap/reader.h
new file mode 100644
index 0000000..c8cda26
--- /dev/null
+++ b/src/contrib/dnstap/reader.h
@@ -0,0 +1,72 @@
+/*  Copyright (C) 2017 Farsight Security, Inc. <software@farsightsecurity.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Dnstap file reader.
+ */
+
+#pragma once
+
+#include <fstrm.h>
+#include <protobuf-c/protobuf-c.h>
+
+#include "contrib/dnstap/dnstap.pb-c.h"
+
+/*! \brief Structure for dnstap file reader. */
+typedef struct {
+	/*!< Input reader. */
+	struct fstrm_reader	*fr;
+} dt_reader_t;
+
+/*!
+ * \brief Creates dnstap file reader structure.
+ *
+ * \param file_path		Name of file to read input from.
+ *
+ * \retval reader		if success.
+ * \retval NULL			if error.
+ */
+dt_reader_t* dt_reader_create(const char *file_path);
+
+/*!
+ * \brief Close dnstap file reader.
+ *
+ * \param reader		dnstap file reader structure.
+ */
+void dt_reader_free(dt_reader_t *reader);
+
+/*!
+ * \brief Read a dnstap protobuf from a dnstap file reader.
+ *
+ * Caller must deallocate the returned protobuf with the
+ * dnstap__dnstap__free_unpacked() function.
+ *
+ * \param[in]  reader		dnstap file reader structure.
+ * \param[out] d     		Unpacked dnstap protobuf.
+ *
+ * \retval KNOT_EOK
+ * \retval KNOT_ERROR
+ * \retval KNOT_EOF
+ * \retval KNOT_ENOMEM
+ */
+int dt_reader_read(dt_reader_t *reader, Dnstap__Dnstap **d);
+
+/*!
+ * \brief free the frame allocated by dt_read_data.
+ *
+ * \param reader                Dnstap reader context.
+ * \param d                     The frame to be freed.
+ */
+void dt_reader_free_frame(dt_reader_t *reader, Dnstap__Dnstap **d);
diff --git a/src/contrib/dnstap/writer.c b/src/contrib/dnstap/writer.c
new file mode 100644
index 0000000..08f4519
--- /dev/null
+++ b/src/contrib/dnstap/writer.c
@@ -0,0 +1,120 @@
+/*  Copyright (C) 2014 Farsight Security, Inc. <software@farsightsecurity.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "libknot/errcode.h"
+
+#include "contrib/dnstap/dnstap.h"
+#include "contrib/dnstap/writer.h"
+
+dt_writer_t* dt_writer_create(const char *file_path, const char *version)
+{
+	struct fstrm_file_options *fopt = NULL;
+	struct fstrm_writer_options *wopt = NULL;
+	dt_writer_t *writer = NULL;
+	fstrm_res res;
+
+	writer = calloc(1, sizeof(dt_writer_t));
+	if (writer == NULL) {
+		goto fail;
+	}
+
+	// Set "version".
+	if (version != NULL) {
+		writer->len_version = strlen(version);
+		writer->version = strdup(version);
+		if (!writer->version) {
+			goto fail;
+		}
+	}
+
+	// Open writer.
+	fopt = fstrm_file_options_init();
+	fstrm_file_options_set_file_path(fopt, file_path);
+	wopt = fstrm_writer_options_init();
+	fstrm_writer_options_add_content_type(wopt,
+		(const uint8_t *) DNSTAP_CONTENT_TYPE,
+		strlen(DNSTAP_CONTENT_TYPE));
+	writer->fw = fstrm_file_writer_init(fopt, wopt);
+	fstrm_file_options_destroy(&fopt);
+	fstrm_writer_options_destroy(&wopt);
+	if (writer->fw == NULL) {
+		goto fail;
+	}
+
+	res = fstrm_writer_open(writer->fw);
+	if (res != fstrm_res_success) {
+		goto fail;
+	}
+
+	return writer;
+fail:
+	dt_writer_free(writer);
+	return NULL;
+}
+
+void dt_writer_free(dt_writer_t *writer)
+{
+	if (writer == NULL) {
+		return;
+	}
+
+	fstrm_writer_destroy(&writer->fw);
+	free(writer->version);
+	free(writer);
+}
+
+int dt_writer_write(dt_writer_t *writer, const ProtobufCMessage *msg)
+{
+	Dnstap__Dnstap dnstap = DNSTAP__DNSTAP__INIT;
+	size_t len;
+	uint8_t *data;
+
+	if (writer->fw == NULL) {
+		return KNOT_EOK;
+	}
+
+	// Only handle dnstap/Message.
+	assert(msg->descriptor == &dnstap__message__descriptor);
+
+	// Fill out 'dnstap'.
+	if (writer->version) {
+		dnstap.version.data = writer->version;
+		dnstap.version.len = writer->len_version;
+		dnstap.has_version = 1;
+	}
+	dnstap.type = DNSTAP__DNSTAP__TYPE__MESSAGE;
+	dnstap.message = (Dnstap__Message *)msg;
+
+	// Serialize the dnstap frame.
+	if (!dt_pack(&dnstap, &data, &len)) {
+		return KNOT_ENOMEM;
+	}
+
+	// Write the dnstap frame to the output stream.
+	if (fstrm_writer_write(writer->fw, data, len) != fstrm_res_success) {
+		return KNOT_ERROR;
+	}
+
+	// Cleanup.
+	free(data);
+
+	return KNOT_EOK;
+}
diff --git a/src/contrib/dnstap/writer.h b/src/contrib/dnstap/writer.h
new file mode 100644
index 0000000..4fe7326
--- /dev/null
+++ b/src/contrib/dnstap/writer.h
@@ -0,0 +1,70 @@
+/*  Copyright (C) 2014 Farsight Security, Inc. <software@farsightsecurity.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \author Robert Edmonds <edmonds@fsi.io>
+ *
+ * \brief Dnstap file writer.
+ */
+
+#pragma once
+
+#include <fstrm.h>
+#include <protobuf-c/protobuf-c.h>
+
+/*! \brief Structure for dnstap file writer. */
+typedef struct {
+	/*!< Output writer. */
+	struct fstrm_writer	*fw;
+
+	/*!< dnstap "version" field. */
+	void			*version;
+
+	/*!< length of dnstap "version" field. */
+	size_t			len_version;
+} dt_writer_t;
+
+/*!
+ * \brief Creates dnstap file writer structure.
+ *
+ * \param file_path		Name of file to write output to.
+ * \param version		Version string of software. May be NULL.
+ *
+ * \retval writer		if success.
+ * \retval NULL			if error.
+ */
+dt_writer_t* dt_writer_create(const char *file_path, const char *version);
+
+/*!
+ * \brief Finish writing dnstap file writer and free resources.
+ *
+ * \param writer		dnstap file writer structure.
+ */
+void dt_writer_free(dt_writer_t *writer);
+
+/*!
+ * \brief Write a protobuf to the dnstap file writer.
+ *
+ * Supported protobuf types for the 'msg' parameter:
+ *	\c Dnstap__Message
+ *
+ * \param writer		dnstap file writer structure.
+ * \param msg			dnstap protobuf. Must be a supported type.
+ *
+ * \retval KNOT_EOK
+ * \retval KNOT_EINVAL
+ * \retval KNOT_ENOMEM
+ */
+int dt_writer_write(dt_writer_t *writer, const ProtobufCMessage *msg);
diff --git a/src/contrib/dynarray.h b/src/contrib/dynarray.h
new file mode 100644
index 0000000..79eab31
--- /dev/null
+++ b/src/contrib/dynarray.h
@@ -0,0 +1,123 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Simple write-once allocation-optimal dynamic array.
+ *
+ * Include it into your .c file
+ *
+ * prefix - identifier prefix, e.g. ptr -> struct ptr_dynarray, ptr_dynarray_add(), ...
+ * ntype - data type to be stored. Let it be a number, pointer or small struct
+ * initial_capacity - how many data items will be allocated on stac and copied with assignment
+ *
+ * prefix_dynarray_add() - add a data item
+ * prefix_dynarray_fix() - call EVERYTIME the array is copied from some already invalid stack
+ * prefix_dynarray_free() - call EVERYTIME you dismiss all copies of the array
+ *
+ */
+
+#include <stdlib.h>
+#include <assert.h>
+
+#pragma once
+
+#define DYNARRAY_VISIBILITY_STATIC static
+#define DYNARRAY_VISIBILITY_PUBLIC
+#define DYNARRAY_VISIBILITY_LIBRARY __public__
+
+#define dynarray_declare(prefix, ntype, visibility, initial_capacity) \
+	typedef struct prefix ## _dynarray { \
+		ssize_t capacity; \
+		ssize_t size; \
+		ntype *(*arr)(struct prefix ## _dynarray *dynarray); \
+		ntype init[initial_capacity]; \
+		ntype *_arr; \
+	} prefix ## _dynarray_t; \
+	\
+	visibility ntype *prefix ## _dynarray_arr(prefix ## _dynarray_t *dynarray); \
+	visibility void prefix ## _dynarray_add(prefix ## _dynarray_t *dynarray, \
+	                                        ntype const *to_add); \
+	visibility void prefix ## _dynarray_free(prefix ## _dynarray_t *dynarray);
+
+#define dynarray_foreach(prefix, ntype, ptr, array) \
+	for (ntype *ptr = prefix ## _dynarray_arr(&(array)); \
+	     ptr < prefix ## _dynarray_arr(&(array)) + (array).size; ptr++)
+
+#define dynarray_define(prefix, ntype, visibility) \
+	\
+	static void prefix ## _dynarray_free__(struct prefix ## _dynarray *dynarray) \
+	{ \
+		if (dynarray->capacity > sizeof(dynarray->init) / sizeof(*dynarray->init)) { \
+			free(dynarray->_arr); \
+		} \
+	} \
+	\
+	__attribute__((unused)) \
+	visibility ntype *prefix ## _dynarray_arr(struct prefix ## _dynarray *dynarray) \
+	{ \
+		assert(dynarray->size <= dynarray->capacity); \
+		return (dynarray->capacity <= sizeof(dynarray->init) / sizeof(*dynarray->init) ? \
+			dynarray->init : dynarray->_arr); \
+	} \
+	\
+	static ntype *prefix ## _dynarray_arr_init__(struct prefix ## _dynarray *dynarray) \
+	{ \
+		assert(dynarray->capacity == sizeof(dynarray->init) / sizeof(*dynarray->init)); \
+		return dynarray->init; \
+	} \
+	\
+	static ntype *prefix ## _dynarray_arr_arr__(struct prefix ## _dynarray *dynarray) \
+	{ \
+		assert(dynarray->capacity > sizeof(dynarray->init) / sizeof(*dynarray->init)); \
+		return dynarray->_arr; \
+	} \
+	\
+	__attribute__((unused)) \
+	visibility void prefix ## _dynarray_add(struct prefix ## _dynarray *dynarray, \
+	                                        ntype const *to_add) \
+	{ \
+		if (dynarray->capacity < 0) { \
+			return; \
+		} \
+		if (dynarray->capacity == 0) { \
+			dynarray->capacity = sizeof(dynarray->init) / sizeof(*dynarray->init); \
+			dynarray->arr = prefix ## _dynarray_arr_init__; \
+		} \
+		if (dynarray->size >= dynarray->capacity) { \
+			ssize_t new_capacity = dynarray->capacity * 2 + 1; \
+			ntype *new_arr = calloc(new_capacity, sizeof(ntype)); \
+			if (new_arr == NULL) { \
+				prefix ## _dynarray_free__(dynarray); \
+				dynarray->capacity = dynarray->size = -1; \
+				return; \
+			} \
+			if (dynarray->capacity > 0) { \
+				memcpy(new_arr, prefix ## _dynarray_arr(dynarray), \
+				       dynarray->capacity * sizeof(ntype)); \
+			} \
+			prefix ## _dynarray_free__(dynarray); \
+			dynarray->_arr = new_arr; \
+			dynarray->capacity = new_capacity; \
+			dynarray->arr = prefix ## _dynarray_arr_arr__; \
+		} \
+		prefix ## _dynarray_arr(dynarray)[dynarray->size++] = *to_add; \
+	} \
+	\
+	__attribute__((unused)) \
+	visibility void prefix ## _dynarray_free(struct prefix ## _dynarray *dynarray) \
+	{ \
+		prefix ## _dynarray_free__(dynarray); \
+		memset(dynarray, 0, sizeof(*dynarray)); \
+	}
diff --git a/src/contrib/files.c b/src/contrib/files.c
new file mode 100644
index 0000000..3181386
--- /dev/null
+++ b/src/contrib/files.c
@@ -0,0 +1,134 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <assert.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <ftw.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "contrib/files.h"
+#include "contrib/string.h"
+#include "libknot/errcode.h"
+
+static int remove_file(const char *path, const struct stat *stat, int type, struct FTW *ftw)
+{
+	(void)stat;
+	(void)ftw;
+	if (type == FTW_DP) {
+		return rmdir(path);
+	} else {
+		return unlink(path);
+	}
+}
+
+bool remove_path(const char *path)
+{
+	return (0 == nftw(path, remove_file, 1, FTW_DEPTH | FTW_PHYS));
+}
+
+int make_dir(const char *path, mode_t mode, bool ignore_existing)
+{
+	if (mkdir(path, mode) == 0) {
+		return KNOT_EOK;
+	}
+
+	if (!ignore_existing || errno != EEXIST) {
+		return knot_map_errno();
+	}
+
+	assert(errno == EEXIST);
+
+	struct stat st = { 0 };
+	if (stat(path, &st) != 0) {
+		return knot_map_errno();
+	}
+
+	if (!S_ISDIR(st.st_mode)) {
+		return knot_map_errno_code(ENOTDIR);
+	}
+
+	return KNOT_EOK;
+}
+
+int make_path(const char *path, mode_t mode)
+{
+	if (path == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	char *dir = strdup(path);
+	if (dir == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	for (char *p = strchr(dir + 1, '/'); p != NULL; p = strchr(p + 1, '/')) {
+		*p = '\0';
+		if (mkdir(dir, mode) == -1 && errno != EEXIST) {
+			free(dir);
+			return knot_map_errno();
+		}
+		*p = '/';
+	}
+
+	free(dir);
+
+	return KNOT_EOK;
+}
+
+int open_tmp_file(const char *path, char **tmp_name, FILE **file, mode_t mode)
+{
+	int ret;
+
+	*tmp_name = sprintf_alloc("%s.XXXXXX", path);
+	if (*tmp_name == NULL) {
+		ret = KNOT_ENOMEM;
+		goto open_tmp_failed;
+	}
+
+	int fd = mkstemp(*tmp_name);
+	if (fd < 0) {
+		ret = knot_map_errno();
+		goto open_tmp_failed;
+	}
+
+	if (fchmod(fd, mode) != 0) {
+		ret = knot_map_errno();
+		close(fd);
+		unlink(*tmp_name);
+		goto open_tmp_failed;
+	}
+
+	*file = fdopen(fd, "w");
+	if (*file == NULL) {
+		ret = knot_map_errno();
+		close(fd);
+		unlink(*tmp_name);
+		goto open_tmp_failed;
+	}
+
+	return KNOT_EOK;
+open_tmp_failed:
+	free(*tmp_name);
+	*tmp_name = NULL;
+	*file = NULL;
+
+	assert(ret != KNOT_EOK);
+	return ret;
+}
diff --git a/src/contrib/files.h b/src/contrib/files.h
new file mode 100644
index 0000000..c4c681f
--- /dev/null
+++ b/src/contrib/files.h
@@ -0,0 +1,43 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/types.h>
+
+/*!
+ * \brief Delete file or directory (recursive).
+ *
+ * \return true on success, false when one or more files failed to be removed.
+ */
+bool remove_path(const char *path);
+
+/*!
+ * Equivalent to mkdir(2), can succeed if the directory already exists.
+ */
+int make_dir(const char *path, mode_t mode, bool ignore_existing);
+
+/*!
+ * Makes a directory part of the path with all parent directories if not exist.
+ */
+int make_path(const char *path, mode_t mode);
+
+/*!
+ * Creates and opens for writing a temporary file based on given path.
+ */
+int open_tmp_file(const char *path, char **tmp_name, FILE **file, mode_t mode);
diff --git a/src/contrib/getline.c b/src/contrib/getline.c
new file mode 100644
index 0000000..074c511
--- /dev/null
+++ b/src/contrib/getline.c
@@ -0,0 +1,60 @@
+/*  Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+// FreeBSD POSIX2008 getline
+#ifndef _WITH_GETLINE
+#define _WITH_GETLINE
+#endif
+
+#include "contrib/getline.h"
+
+#include <stdio.h>		// getline or fgetln
+#include <stdlib.h>		// free
+#include <string.h>		// memcpy
+
+ssize_t knot_getline(char **lineptr, size_t *n, FILE *stream)
+{
+#ifdef HAVE_GETLINE
+	return getline(lineptr, n, stream);
+#else
+#ifdef HAVE_FGETLN
+	size_t length = 0;
+	char *buffer = fgetln(stream, &length);
+	if (buffer == NULL) {
+		return -1;
+	}
+
+	/* NOTE: Function fgetln doesn't return terminated string!
+	 *       Output buffer from the fgetln can't be freed.
+	 */
+
+	// If the output buffer is not specified or is small, extend it.
+	if (*lineptr == NULL || *n <= length) {
+		char *tmp = realloc(*lineptr, length + 1);
+		if (tmp == NULL) {
+			return -1;
+		}
+		*lineptr = tmp;
+		*n = length + 1;
+	}
+
+	memcpy(*lineptr, buffer, length);
+	(*lineptr)[length] = '\0';
+
+	return length;
+#endif
+#endif
+}
diff --git a/src/contrib/getline.h b/src/contrib/getline.h
new file mode 100644
index 0000000..11c7fe3
--- /dev/null
+++ b/src/contrib/getline.h
@@ -0,0 +1,38 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Multiplatform getline wrapper.
+ */
+
+#pragma once
+
+#include <stdio.h>
+#include <sys/types.h>
+
+/*!
+ * \brief Reads a line from a stream.
+ *
+ * This function has the same semantics as POSIX.1-2008 getline().
+ * If necessary, the output buffer will be allocated/reallocated.
+ *
+ * \param lineptr	Output buffer.
+ * \param n		Output buffer size.
+ * \param stream	Input stream.
+ *
+ * \retval Number of characters read, including new line delimiter,
+ *         not including terminating. -1 on error or EOF.
+ */
+ssize_t knot_getline(char **lineptr, size_t *n, FILE *stream);
diff --git a/src/contrib/licenses/0BSD b/src/contrib/licenses/0BSD
new file mode 100644
index 0000000..56c5528
--- /dev/null
+++ b/src/contrib/licenses/0BSD
@@ -0,0 +1,12 @@
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
diff --git a/src/contrib/licenses/BSD-3-Clause b/src/contrib/licenses/BSD-3-Clause
new file mode 100644
index 0000000..8041f21
--- /dev/null
+++ b/src/contrib/licenses/BSD-3-Clause
@@ -0,0 +1,21 @@
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+3. Neither the name of the copyright holder nor the names of its contributors
+   may be used to endorse or promote products derived from this software without
+   specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/src/contrib/licenses/LGPL-2.0 b/src/contrib/licenses/LGPL-2.0
new file mode 100644
index 0000000..d159169
--- /dev/null
+++ b/src/contrib/licenses/LGPL-2.0
@@ -0,0 +1,339 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary.  To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
+    announcement including an appropriate copyright notice and a
+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
+    these conditions, and telling the user how to view a copy of this
+    License.  (Exception: if the Program itself is interactive but
+    does not normally print such an announcement, your work based on
+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+    a) Accompany it with the complete corresponding machine-readable
+    source code, which must be distributed under the terms of Sections
+    1 and 2 above on a medium customarily used for software interchange; or,
+
+    b) Accompany it with a written offer, valid for at least three
+    years, to give any third party, for a charge no more than your
+    cost of physically performing source distribution, a complete
+    machine-readable copy of the corresponding source code, to be
+    distributed under the terms of Sections 1 and 2 above on a medium
+    customarily used for software interchange; or,
+
+    c) Accompany it with the information you received as to the offer
+    to distribute corresponding source code.  (This alternative is
+    allowed only for noncommercial distribution and only if you
+    received the program in object code or executable form with such
+    an offer, in accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for
+making modifications to it.  For an executable work, complete source
+code means all the source code for all modules it contains, plus any
+associated interface definition files, plus the scripts used to
+control compilation and installation of the executable.  However, as a
+special exception, the source code distributed need not include
+anything that is normally distributed (in either source or binary
+form) with the major components (compiler, kernel, and so on) of the
+operating system on which the executable runs, unless that component
+itself accompanies the executable.
+
+If distribution of executable or object code is made by offering
+access to copy from a designated place, then offering equivalent
+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
+distribute the Program or its derivative works.  These actions are
+prohibited by law if you do not accept this License.  Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions.  You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot
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+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
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+It is not the purpose of this section to induce you to infringe any
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+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
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+countries not thus excluded.  In such case, this License incorporates
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+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
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+make exceptions for this.  Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
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+
+                            NO WARRANTY
+
+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/src/contrib/licenses/OLDAP-2.8 b/src/contrib/licenses/OLDAP-2.8
new file mode 100644
index 0000000..05ad757
--- /dev/null
+++ b/src/contrib/licenses/OLDAP-2.8
@@ -0,0 +1,47 @@
+The OpenLDAP Public License
+  Version 2.8, 17 August 2003
+
+Redistribution and use of this software and associated documentation
+("Software"), with or without modification, are permitted provided
+that the following conditions are met:
+
+1. Redistributions in source form must retain copyright statements
+   and notices,
+
+2. Redistributions in binary form must reproduce applicable copyright
+   statements and notices, this list of conditions, and the following
+   disclaimer in the documentation and/or other materials provided
+   with the distribution, and
+
+3. Redistributions must contain a verbatim copy of this document.
+
+The OpenLDAP Foundation may revise this license from time to time.
+Each revision is distinguished by a version number.  You may use
+this Software under terms of this license revision or under the
+terms of any subsequent revision of the license.
+
+THIS SOFTWARE IS PROVIDED BY THE OPENLDAP FOUNDATION AND ITS
+CONTRIBUTORS ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
+INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT
+SHALL THE OPENLDAP FOUNDATION, ITS CONTRIBUTORS, OR THE AUTHOR(S)
+OR OWNER(S) OF THE SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+The names of the authors and copyright holders must not be used in
+advertising or otherwise to promote the sale, use or other dealing
+in this Software without specific, written prior permission.  Title
+to copyright in this Software shall at all times remain with copyright
+holders.
+
+OpenLDAP is a registered trademark of the OpenLDAP Foundation.
+
+Copyright 1999-2003 The OpenLDAP Foundation, Redwood City,
+California, USA.  All Rights Reserved.  Permission to copy and
+distribute verbatim copies of this document is granted.
diff --git a/src/contrib/lmdb/LICENSE b/src/contrib/lmdb/LICENSE
new file mode 100644
index 0000000..66210f0
--- /dev/null
+++ b/src/contrib/lmdb/LICENSE
@@ -0,0 +1 @@
+../licenses/OLDAP-2.8
\ No newline at end of file
diff --git a/src/contrib/lmdb/lmdb.h b/src/contrib/lmdb/lmdb.h
new file mode 100644
index 0000000..32a278e
--- /dev/null
+++ b/src/contrib/lmdb/lmdb.h
@@ -0,0 +1,1604 @@
+/** @file lmdb.h
+ *	@brief Lightning memory-mapped database library
+ *
+ *	@mainpage	Lightning Memory-Mapped Database Manager (LMDB)
+ *
+ *	@section intro_sec Introduction
+ *	LMDB is a Btree-based database management library modeled loosely on the
+ *	BerkeleyDB API, but much simplified. The entire database is exposed
+ *	in a memory map, and all data fetches return data directly
+ *	from the mapped memory, so no malloc's or memcpy's occur during
+ *	data fetches. As such, the library is extremely simple because it
+ *	requires no page caching layer of its own, and it is extremely high
+ *	performance and memory-efficient. It is also fully transactional with
+ *	full ACID semantics, and when the memory map is read-only, the
+ *	database integrity cannot be corrupted by stray pointer writes from
+ *	application code.
+ *
+ *	The library is fully thread-aware and supports concurrent read/write
+ *	access from multiple processes and threads. Data pages use a copy-on-
+ *	write strategy so no active data pages are ever overwritten, which
+ *	also provides resistance to corruption and eliminates the need of any
+ *	special recovery procedures after a system crash. Writes are fully
+ *	serialized; only one write transaction may be active at a time, which
+ *	guarantees that writers can never deadlock. The database structure is
+ *	multi-versioned so readers run with no locks; writers cannot block
+ *	readers, and readers don't block writers.
+ *
+ *	Unlike other well-known database mechanisms which use either write-ahead
+ *	transaction logs or append-only data writes, LMDB requires no maintenance
+ *	during operation. Both write-ahead loggers and append-only databases
+ *	require periodic checkpointing and/or compaction of their log or database
+ *	files otherwise they grow without bound. LMDB tracks free pages within
+ *	the database and re-uses them for new write operations, so the database
+ *	size does not grow without bound in normal use.
+ *
+ *	The memory map can be used as a read-only or read-write map. It is
+ *	read-only by default as this provides total immunity to corruption.
+ *	Using read-write mode offers much higher write performance, but adds
+ *	the possibility for stray application writes thru pointers to silently
+ *	corrupt the database. Of course if your application code is known to
+ *	be bug-free (...) then this is not an issue.
+ *
+ *	If this is your first time using a transactional embedded key/value
+ *	store, you may find the \ref starting page to be helpful.
+ *
+ *	@section caveats_sec Caveats
+ *	Troubleshooting the lock file, plus semaphores on BSD systems:
+ *
+ *	- A broken lockfile can cause sync issues.
+ *	  Stale reader transactions left behind by an aborted program
+ *	  cause further writes to grow the database quickly, and
+ *	  stale locks can block further operation.
+ *
+ *	  Fix: Check for stale readers periodically, using the
+ *	  #mdb_reader_check function or the \ref mdb_stat_1 "mdb_stat" tool.
+ *	  Stale writers will be cleared automatically on some systems:
+ *	  - Windows - automatic
+ *	  - Linux, systems using POSIX mutexes with Robust option - automatic
+ *	  - not on BSD, systems using POSIX semaphores.
+ *	  Otherwise just make all programs using the database close it;
+ *	  the lockfile is always reset on first open of the environment.
+ *
+ *	- On BSD systems or others configured with MDB_USE_POSIX_SEM,
+ *	  startup can fail due to semaphores owned by another userid.
+ *
+ *	  Fix: Open and close the database as the user which owns the
+ *	  semaphores (likely last user) or as root, while no other
+ *	  process is using the database.
+ *
+ *	Restrictions/caveats (in addition to those listed for some functions):
+ *
+ *	- Only the database owner should normally use the database on
+ *	  BSD systems or when otherwise configured with MDB_USE_POSIX_SEM.
+ *	  Multiple users can cause startup to fail later, as noted above.
+ *
+ *	- There is normally no pure read-only mode, since readers need write
+ *	  access to locks and lock file. Exceptions: On read-only filesystems
+ *	  or with the #MDB_NOLOCK flag described under #mdb_env_open().
+ *
+ *	- An LMDB configuration will often reserve considerable \b unused
+ *	  memory address space and maybe file size for future growth.
+ *	  This does not use actual memory or disk space, but users may need
+ *	  to understand the difference so they won't be scared off.
+ *
+ *	- By default, in versions before 0.9.10, unused portions of the data
+ *	  file might receive garbage data from memory freed by other code.
+ *	  (This does not happen when using the #MDB_WRITEMAP flag.) As of
+ *	  0.9.10 the default behavior is to initialize such memory before
+ *	  writing to the data file. Since there may be a slight performance
+ *	  cost due to this initialization, applications may disable it using
+ *	  the #MDB_NOMEMINIT flag. Applications handling sensitive data
+ *	  which must not be written should not use this flag. This flag is
+ *	  irrelevant when using #MDB_WRITEMAP.
+ *
+ *	- A thread can only use one transaction at a time, plus any child
+ *	  transactions.  Each transaction belongs to one thread.  See below.
+ *	  The #MDB_NOTLS flag changes this for read-only transactions.
+ *
+ *	- Use an MDB_env* in the process which opened it, not after fork().
+ *
+ *	- Do not have open an LMDB database twice in the same process at
+ *	  the same time.  Not even from a plain open() call - close()ing it
+ *	  breaks fcntl() advisory locking.  (It is OK to reopen it after
+ *	  fork() - exec*(), since the lockfile has FD_CLOEXEC set.)
+ *
+ *	- Avoid long-lived transactions.  Read transactions prevent
+ *	  reuse of pages freed by newer write transactions, thus the
+ *	  database can grow quickly.  Write transactions prevent
+ *	  other write transactions, since writes are serialized.
+ *
+ *	- Avoid suspending a process with active transactions.  These
+ *	  would then be "long-lived" as above.  Also read transactions
+ *	  suspended when writers commit could sometimes see wrong data.
+ *
+ *	...when several processes can use a database concurrently:
+ *
+ *	- Avoid aborting a process with an active transaction.
+ *	  The transaction becomes "long-lived" as above until a check
+ *	  for stale readers is performed or the lockfile is reset,
+ *	  since the process may not remove it from the lockfile.
+ *
+ *	  This does not apply to write transactions if the system clears
+ *	  stale writers, see above.
+ *
+ *	- If you do that anyway, do a periodic check for stale readers. Or
+ *	  close the environment once in a while, so the lockfile can get reset.
+ *
+ *	- Do not use LMDB databases on remote filesystems, even between
+ *	  processes on the same host.  This breaks flock() on some OSes,
+ *	  possibly memory map sync, and certainly sync between programs
+ *	  on different hosts.
+ *
+ *	- Opening a database can fail if another process is opening or
+ *	  closing it at exactly the same time.
+ *
+ *	@author	Howard Chu, Symas Corporation.
+ *
+ *	@copyright Copyright 2011-2018 Howard Chu, Symas Corp. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ *
+ *	@par Derived From:
+ * This code is derived from btree.c written by Martin Hedenfalk.
+ *
+ * Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#ifndef _LMDB_H_
+#define _LMDB_H_
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Unix permissions for creating files, or dummy definition for Windows */
+#ifdef _MSC_VER
+typedef	int	mdb_mode_t;
+#else
+typedef	mode_t	mdb_mode_t;
+#endif
+
+/** An abstraction for a file handle.
+ *	On POSIX systems file handles are small integers. On Windows
+ *	they're opaque pointers.
+ */
+#ifdef _WIN32
+typedef	void *mdb_filehandle_t;
+#else
+typedef int mdb_filehandle_t;
+#endif
+
+/** @defgroup mdb LMDB API
+ *	@{
+ *	@brief OpenLDAP Lightning Memory-Mapped Database Manager
+ */
+/** @defgroup Version Version Macros
+ *	@{
+ */
+/** Library major version */
+#define MDB_VERSION_MAJOR	0
+/** Library minor version */
+#define MDB_VERSION_MINOR	9
+/** Library patch version */
+#define MDB_VERSION_PATCH	22
+
+/** Combine args a,b,c into a single integer for easy version comparisons */
+#define MDB_VERINT(a,b,c)	(((a) << 24) | ((b) << 16) | (c))
+
+/** The full library version as a single integer */
+#define MDB_VERSION_FULL	\
+	MDB_VERINT(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH)
+
+/** The release date of this library version */
+#define MDB_VERSION_DATE	"March 21, 2018"
+
+/** A stringifier for the version info */
+#define MDB_VERSTR(a,b,c,d)	"LMDB " #a "." #b "." #c ": (" d ")"
+
+/** A helper for the stringifier macro */
+#define MDB_VERFOO(a,b,c,d)	MDB_VERSTR(a,b,c,d)
+
+/** The full library version as a C string */
+#define	MDB_VERSION_STRING	\
+	MDB_VERFOO(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH,MDB_VERSION_DATE)
+/**	@} */
+
+/** @brief Opaque structure for a database environment.
+ *
+ * A DB environment supports multiple databases, all residing in the same
+ * shared-memory map.
+ */
+typedef struct MDB_env MDB_env;
+
+/** @brief Opaque structure for a transaction handle.
+ *
+ * All database operations require a transaction handle. Transactions may be
+ * read-only or read-write.
+ */
+typedef struct MDB_txn MDB_txn;
+
+/** @brief A handle for an individual database in the DB environment. */
+typedef unsigned int	MDB_dbi;
+
+/** @brief Opaque structure for navigating through a database */
+typedef struct MDB_cursor MDB_cursor;
+
+/** @brief Generic structure used for passing keys and data in and out
+ * of the database.
+ *
+ * Values returned from the database are valid only until a subsequent
+ * update operation, or the end of the transaction. Do not modify or
+ * free them, they commonly point into the database itself.
+ *
+ * Key sizes must be between 1 and #mdb_env_get_maxkeysize() inclusive.
+ * The same applies to data sizes in databases with the #MDB_DUPSORT flag.
+ * Other data items can in theory be from 0 to 0xffffffff bytes long.
+ */
+typedef struct MDB_val {
+	size_t		 mv_size;	/**< size of the data item */
+	void		*mv_data;	/**< address of the data item */
+} MDB_val;
+
+/** @brief A callback function used to compare two keys in a database */
+typedef int  (MDB_cmp_func)(const MDB_val *a, const MDB_val *b);
+
+/** @brief A callback function used to relocate a position-dependent data item
+ * in a fixed-address database.
+ *
+ * The \b newptr gives the item's desired address in
+ * the memory map, and \b oldptr gives its previous address. The item's actual
+ * data resides at the address in \b item.  This callback is expected to walk
+ * through the fields of the record in \b item and modify any
+ * values based at the \b oldptr address to be relative to the \b newptr address.
+ * @param[in,out] item The item that is to be relocated.
+ * @param[in] oldptr The previous address.
+ * @param[in] newptr The new address to relocate to.
+ * @param[in] relctx An application-provided context, set by #mdb_set_relctx().
+ * @todo This feature is currently unimplemented.
+ */
+typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *relctx);
+
+/** @defgroup	mdb_env	Environment Flags
+ *	@{
+ */
+	/** mmap at a fixed address (experimental) */
+#define MDB_FIXEDMAP	0x01
+	/** no environment directory */
+#define MDB_NOSUBDIR	0x4000
+	/** don't fsync after commit */
+#define MDB_NOSYNC		0x10000
+	/** read only */
+#define MDB_RDONLY		0x20000
+	/** don't fsync metapage after commit */
+#define MDB_NOMETASYNC		0x40000
+	/** use writable mmap */
+#define MDB_WRITEMAP		0x80000
+	/** use asynchronous msync when #MDB_WRITEMAP is used */
+#define MDB_MAPASYNC		0x100000
+	/** tie reader locktable slots to #MDB_txn objects instead of to threads */
+#define MDB_NOTLS		0x200000
+	/** don't do any locking, caller must manage their own locks */
+#define MDB_NOLOCK		0x400000
+	/** don't do readahead (no effect on Windows) */
+#define MDB_NORDAHEAD	0x800000
+	/** don't initialize malloc'd memory before writing to datafile */
+#define MDB_NOMEMINIT	0x1000000
+/** @} */
+
+/**	@defgroup	mdb_dbi_open	Database Flags
+ *	@{
+ */
+	/** use reverse string keys */
+#define MDB_REVERSEKEY	0x02
+	/** use sorted duplicates */
+#define MDB_DUPSORT		0x04
+	/** numeric keys in native byte order: either unsigned int or size_t.
+	 *  The keys must all be of the same size. */
+#define MDB_INTEGERKEY	0x08
+	/** with #MDB_DUPSORT, sorted dup items have fixed size */
+#define MDB_DUPFIXED	0x10
+	/** with #MDB_DUPSORT, dups are #MDB_INTEGERKEY-style integers */
+#define MDB_INTEGERDUP	0x20
+	/** with #MDB_DUPSORT, use reverse string dups */
+#define MDB_REVERSEDUP	0x40
+	/** create DB if not already existing */
+#define MDB_CREATE		0x40000
+/** @} */
+
+/**	@defgroup mdb_put	Write Flags
+ *	@{
+ */
+/** For put: Don't write if the key already exists. */
+#define MDB_NOOVERWRITE	0x10
+/** Only for #MDB_DUPSORT<br>
+ * For put: don't write if the key and data pair already exist.<br>
+ * For mdb_cursor_del: remove all duplicate data items.
+ */
+#define MDB_NODUPDATA	0x20
+/** For mdb_cursor_put: overwrite the current key/data pair */
+#define MDB_CURRENT	0x40
+/** For put: Just reserve space for data, don't copy it. Return a
+ * pointer to the reserved space.
+ */
+#define MDB_RESERVE	0x10000
+/** Data is being appended, don't split full pages. */
+#define MDB_APPEND	0x20000
+/** Duplicate data is being appended, don't split full pages. */
+#define MDB_APPENDDUP	0x40000
+/** Store multiple data items in one call. Only for #MDB_DUPFIXED. */
+#define MDB_MULTIPLE	0x80000
+/*	@} */
+
+/**	@defgroup mdb_copy	Copy Flags
+ *	@{
+ */
+/** Compacting copy: Omit free space from copy, and renumber all
+ * pages sequentially.
+ */
+#define MDB_CP_COMPACT	0x01
+/*	@} */
+
+/** @brief Cursor Get operations.
+ *
+ *	This is the set of all operations for retrieving data
+ *	using a cursor.
+ */
+typedef enum MDB_cursor_op {
+	MDB_FIRST,				/**< Position at first key/data item */
+	MDB_FIRST_DUP,			/**< Position at first data item of current key.
+								Only for #MDB_DUPSORT */
+	MDB_GET_BOTH,			/**< Position at key/data pair. Only for #MDB_DUPSORT */
+	MDB_GET_BOTH_RANGE,		/**< position at key, nearest data. Only for #MDB_DUPSORT */
+	MDB_GET_CURRENT,		/**< Return key/data at current cursor position */
+	MDB_GET_MULTIPLE,		/**< Return key and up to a page of duplicate data items
+								from current cursor position. Move cursor to prepare
+								for #MDB_NEXT_MULTIPLE. Only for #MDB_DUPFIXED */
+	MDB_LAST,				/**< Position at last key/data item */
+	MDB_LAST_DUP,			/**< Position at last data item of current key.
+								Only for #MDB_DUPSORT */
+	MDB_NEXT,				/**< Position at next data item */
+	MDB_NEXT_DUP,			/**< Position at next data item of current key.
+								Only for #MDB_DUPSORT */
+	MDB_NEXT_MULTIPLE,		/**< Return key and up to a page of duplicate data items
+								from next cursor position. Move cursor to prepare
+								for #MDB_NEXT_MULTIPLE. Only for #MDB_DUPFIXED */
+	MDB_NEXT_NODUP,			/**< Position at first data item of next key */
+	MDB_PREV,				/**< Position at previous data item */
+	MDB_PREV_DUP,			/**< Position at previous data item of current key.
+								Only for #MDB_DUPSORT */
+	MDB_PREV_NODUP,			/**< Position at last data item of previous key */
+	MDB_SET,				/**< Position at specified key */
+	MDB_SET_KEY,			/**< Position at specified key, return key + data */
+	MDB_SET_RANGE,			/**< Position at first key greater than or equal to specified key. */
+	MDB_PREV_MULTIPLE		/**< Position at previous page and return key and up to
+								a page of duplicate data items. Only for #MDB_DUPFIXED */
+} MDB_cursor_op;
+
+/** @defgroup  errors	Return Codes
+ *
+ *	BerkeleyDB uses -30800 to -30999, we'll go under them
+ *	@{
+ */
+	/**	Successful result */
+#define MDB_SUCCESS	 0
+	/** key/data pair already exists */
+#define MDB_KEYEXIST	(-30799)
+	/** key/data pair not found (EOF) */
+#define MDB_NOTFOUND	(-30798)
+	/** Requested page not found - this usually indicates corruption */
+#define MDB_PAGE_NOTFOUND	(-30797)
+	/** Located page was wrong type */
+#define MDB_CORRUPTED	(-30796)
+	/** Update of meta page failed or environment had fatal error */
+#define MDB_PANIC		(-30795)
+	/** Environment version mismatch */
+#define MDB_VERSION_MISMATCH	(-30794)
+	/** File is not a valid LMDB file */
+#define MDB_INVALID	(-30793)
+	/** Environment mapsize reached */
+#define MDB_MAP_FULL	(-30792)
+	/** Environment maxdbs reached */
+#define MDB_DBS_FULL	(-30791)
+	/** Environment maxreaders reached */
+#define MDB_READERS_FULL	(-30790)
+	/** Too many TLS keys in use - Windows only */
+#define MDB_TLS_FULL	(-30789)
+	/** Txn has too many dirty pages */
+#define MDB_TXN_FULL	(-30788)
+	/** Cursor stack too deep - internal error */
+#define MDB_CURSOR_FULL	(-30787)
+	/** Page has not enough space - internal error */
+#define MDB_PAGE_FULL	(-30786)
+	/** Database contents grew beyond environment mapsize */
+#define MDB_MAP_RESIZED	(-30785)
+	/** Operation and DB incompatible, or DB type changed. This can mean:
+	 *	<ul>
+	 *	<li>The operation expects an #MDB_DUPSORT / #MDB_DUPFIXED database.
+	 *	<li>Opening a named DB when the unnamed DB has #MDB_DUPSORT / #MDB_INTEGERKEY.
+	 *	<li>Accessing a data record as a database, or vice versa.
+	 *	<li>The database was dropped and recreated with different flags.
+	 *	</ul>
+	 */
+#define MDB_INCOMPATIBLE	(-30784)
+	/** Invalid reuse of reader locktable slot */
+#define MDB_BAD_RSLOT		(-30783)
+	/** Transaction must abort, has a child, or is invalid */
+#define MDB_BAD_TXN			(-30782)
+	/** Unsupported size of key/DB name/data, or wrong DUPFIXED size */
+#define MDB_BAD_VALSIZE		(-30781)
+	/** The specified DBI was changed unexpectedly */
+#define MDB_BAD_DBI		(-30780)
+	/** The last defined error code */
+#define MDB_LAST_ERRCODE	MDB_BAD_DBI
+/** @} */
+
+/** @brief Statistics for a database in the environment */
+typedef struct MDB_stat {
+	unsigned int	ms_psize;			/**< Size of a database page.
+											This is currently the same for all databases. */
+	unsigned int	ms_depth;			/**< Depth (height) of the B-tree */
+	size_t		ms_branch_pages;	/**< Number of internal (non-leaf) pages */
+	size_t		ms_leaf_pages;		/**< Number of leaf pages */
+	size_t		ms_overflow_pages;	/**< Number of overflow pages */
+	size_t		ms_entries;			/**< Number of data items */
+} MDB_stat;
+
+/** @brief Information about the environment */
+typedef struct MDB_envinfo {
+	void	*me_mapaddr;			/**< Address of map, if fixed */
+	size_t	me_mapsize;				/**< Size of the data memory map */
+	size_t	me_last_pgno;			/**< ID of the last used page */
+	size_t	me_last_txnid;			/**< ID of the last committed transaction */
+	unsigned int me_maxreaders;		/**< max reader slots in the environment */
+	unsigned int me_numreaders;		/**< max reader slots used in the environment */
+} MDB_envinfo;
+
+	/** @brief Return the LMDB library version information.
+	 *
+	 * @param[out] major if non-NULL, the library major version number is copied here
+	 * @param[out] minor if non-NULL, the library minor version number is copied here
+	 * @param[out] patch if non-NULL, the library patch version number is copied here
+	 * @retval "version string" The library version as a string
+	 */
+char *mdb_version(int *major, int *minor, int *patch);
+
+	/** @brief Return a string describing a given error code.
+	 *
+	 * This function is a superset of the ANSI C X3.159-1989 (ANSI C) strerror(3)
+	 * function. If the error code is greater than or equal to 0, then the string
+	 * returned by the system function strerror(3) is returned. If the error code
+	 * is less than 0, an error string corresponding to the LMDB library error is
+	 * returned. See @ref errors for a list of LMDB-specific error codes.
+	 * @param[in] err The error code
+	 * @retval "error message" The description of the error
+	 */
+char *mdb_strerror(int err);
+
+	/** @brief Create an LMDB environment handle.
+	 *
+	 * This function allocates memory for a #MDB_env structure. To release
+	 * the allocated memory and discard the handle, call #mdb_env_close().
+	 * Before the handle may be used, it must be opened using #mdb_env_open().
+	 * Various other options may also need to be set before opening the handle,
+	 * e.g. #mdb_env_set_mapsize(), #mdb_env_set_maxreaders(), #mdb_env_set_maxdbs(),
+	 * depending on usage requirements.
+	 * @param[out] env The address where the new handle will be stored
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int  mdb_env_create(MDB_env **env);
+
+	/** @brief Open an environment handle.
+	 *
+	 * If this function fails, #mdb_env_close() must be called to discard the #MDB_env handle.
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] path The directory in which the database files reside. This
+	 * directory must already exist and be writable.
+	 * @param[in] flags Special options for this environment. This parameter
+	 * must be set to 0 or by bitwise OR'ing together one or more of the
+	 * values described here.
+	 * Flags set by mdb_env_set_flags() are also used.
+	 * <ul>
+	 *	<li>#MDB_FIXEDMAP
+	 *      use a fixed address for the mmap region. This flag must be specified
+	 *      when creating the environment, and is stored persistently in the environment.
+	 *		If successful, the memory map will always reside at the same virtual address
+	 *		and pointers used to reference data items in the database will be constant
+	 *		across multiple invocations. This option may not always work, depending on
+	 *		how the operating system has allocated memory to shared libraries and other uses.
+	 *		The feature is highly experimental.
+	 *	<li>#MDB_NOSUBDIR
+	 *		By default, LMDB creates its environment in a directory whose
+	 *		pathname is given in \b path, and creates its data and lock files
+	 *		under that directory. With this option, \b path is used as-is for
+	 *		the database main data file. The database lock file is the \b path
+	 *		with "-lock" appended.
+	 *	<li>#MDB_RDONLY
+	 *		Open the environment in read-only mode. No write operations will be
+	 *		allowed. LMDB will still modify the lock file - except on read-only
+	 *		filesystems, where LMDB does not use locks.
+	 *	<li>#MDB_WRITEMAP
+	 *		Use a writeable memory map unless MDB_RDONLY is set. This uses
+	 *		fewer mallocs but loses protection from application bugs
+	 *		like wild pointer writes and other bad updates into the database.
+	 *		This may be slightly faster for DBs that fit entirely in RAM, but
+	 *		is slower for DBs larger than RAM.
+	 *		Incompatible with nested transactions.
+	 *		Do not mix processes with and without MDB_WRITEMAP on the same
+	 *		environment.  This can defeat durability (#mdb_env_sync etc).
+	 *	<li>#MDB_NOMETASYNC
+	 *		Flush system buffers to disk only once per transaction, omit the
+	 *		metadata flush. Defer that until the system flushes files to disk,
+	 *		or next non-MDB_RDONLY commit or #mdb_env_sync(). This optimization
+	 *		maintains database integrity, but a system crash may undo the last
+	 *		committed transaction. I.e. it preserves the ACI (atomicity,
+	 *		consistency, isolation) but not D (durability) database property.
+	 *		This flag may be changed at any time using #mdb_env_set_flags().
+	 *	<li>#MDB_NOSYNC
+	 *		Don't flush system buffers to disk when committing a transaction.
+	 *		This optimization means a system crash can corrupt the database or
+	 *		lose the last transactions if buffers are not yet flushed to disk.
+	 *		The risk is governed by how often the system flushes dirty buffers
+	 *		to disk and how often #mdb_env_sync() is called.  However, if the
+	 *		filesystem preserves write order and the #MDB_WRITEMAP flag is not
+	 *		used, transactions exhibit ACI (atomicity, consistency, isolation)
+	 *		properties and only lose D (durability).  I.e. database integrity
+	 *		is maintained, but a system crash may undo the final transactions.
+	 *		Note that (#MDB_NOSYNC | #MDB_WRITEMAP) leaves the system with no
+	 *		hint for when to write transactions to disk, unless #mdb_env_sync()
+	 *		is called. (#MDB_MAPASYNC | #MDB_WRITEMAP) may be preferable.
+	 *		This flag may be changed at any time using #mdb_env_set_flags().
+	 *	<li>#MDB_MAPASYNC
+	 *		When using #MDB_WRITEMAP, use asynchronous flushes to disk.
+	 *		As with #MDB_NOSYNC, a system crash can then corrupt the
+	 *		database or lose the last transactions. Calling #mdb_env_sync()
+	 *		ensures on-disk database integrity until next commit.
+	 *		This flag may be changed at any time using #mdb_env_set_flags().
+	 *	<li>#MDB_NOTLS
+	 *		Don't use Thread-Local Storage. Tie reader locktable slots to
+	 *		#MDB_txn objects instead of to threads. I.e. #mdb_txn_reset() keeps
+	 *		the slot reseved for the #MDB_txn object. A thread may use parallel
+	 *		read-only transactions. A read-only transaction may span threads if
+	 *		the user synchronizes its use. Applications that multiplex many
+	 *		user threads over individual OS threads need this option. Such an
+	 *		application must also serialize the write transactions in an OS
+	 *		thread, since LMDB's write locking is unaware of the user threads.
+	 *	<li>#MDB_NOLOCK
+	 *		Don't do any locking. If concurrent access is anticipated, the
+	 *		caller must manage all concurrency itself. For proper operation
+	 *		the caller must enforce single-writer semantics, and must ensure
+	 *		that no readers are using old transactions while a writer is
+	 *		active. The simplest approach is to use an exclusive lock so that
+	 *		no readers may be active at all when a writer begins.
+	 *	<li>#MDB_NORDAHEAD
+	 *		Turn off readahead. Most operating systems perform readahead on
+	 *		read requests by default. This option turns it off if the OS
+	 *		supports it. Turning it off may help random read performance
+	 *		when the DB is larger than RAM and system RAM is full.
+	 *		The option is not implemented on Windows.
+	 *	<li>#MDB_NOMEMINIT
+	 *		Don't initialize malloc'd memory before writing to unused spaces
+	 *		in the data file. By default, memory for pages written to the data
+	 *		file is obtained using malloc. While these pages may be reused in
+	 *		subsequent transactions, freshly malloc'd pages will be initialized
+	 *		to zeroes before use. This avoids persisting leftover data from other
+	 *		code (that used the heap and subsequently freed the memory) into the
+	 *		data file. Note that many other system libraries may allocate
+	 *		and free memory from the heap for arbitrary uses. E.g., stdio may
+	 *		use the heap for file I/O buffers. This initialization step has a
+	 *		modest performance cost so some applications may want to disable
+	 *		it using this flag. This option can be a problem for applications
+	 *		which handle sensitive data like passwords, and it makes memory
+	 *		checkers like Valgrind noisy. This flag is not needed with #MDB_WRITEMAP,
+	 *		which writes directly to the mmap instead of using malloc for pages. The
+	 *		initialization is also skipped if #MDB_RESERVE is used; the
+	 *		caller is expected to overwrite all of the memory that was
+	 *		reserved in that case.
+	 *		This flag may be changed at any time using #mdb_env_set_flags().
+	 * </ul>
+	 * @param[in] mode The UNIX permissions to set on created files and semaphores.
+	 * This parameter is ignored on Windows.
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>#MDB_VERSION_MISMATCH - the version of the LMDB library doesn't match the
+	 *	version that created the database environment.
+	 *	<li>#MDB_INVALID - the environment file headers are corrupted.
+	 *	<li>ENOENT - the directory specified by the path parameter doesn't exist.
+	 *	<li>EACCES - the user didn't have permission to access the environment files.
+	 *	<li>EAGAIN - the environment was locked by another process.
+	 * </ul>
+	 */
+int  mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode);
+
+	/** @brief Copy an LMDB environment to the specified path.
+	 *
+	 * This function may be used to make a backup of an existing environment.
+	 * No lockfile is created, since it gets recreated at need.
+	 * @note This call can trigger significant file size growth if run in
+	 * parallel with write transactions, because it employs a read-only
+	 * transaction. See long-lived transactions under @ref caveats_sec.
+	 * @param[in] env An environment handle returned by #mdb_env_create(). It
+	 * must have already been opened successfully.
+	 * @param[in] path The directory in which the copy will reside. This
+	 * directory must already exist and be writable but must otherwise be
+	 * empty.
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int  mdb_env_copy(MDB_env *env, const char *path);
+
+	/** @brief Copy an LMDB environment to the specified file descriptor.
+	 *
+	 * This function may be used to make a backup of an existing environment.
+	 * No lockfile is created, since it gets recreated at need.
+	 * @note This call can trigger significant file size growth if run in
+	 * parallel with write transactions, because it employs a read-only
+	 * transaction. See long-lived transactions under @ref caveats_sec.
+	 * @param[in] env An environment handle returned by #mdb_env_create(). It
+	 * must have already been opened successfully.
+	 * @param[in] fd The filedescriptor to write the copy to. It must
+	 * have already been opened for Write access.
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int  mdb_env_copyfd(MDB_env *env, mdb_filehandle_t fd);
+
+	/** @brief Copy an LMDB environment to the specified path, with options.
+	 *
+	 * This function may be used to make a backup of an existing environment.
+	 * No lockfile is created, since it gets recreated at need.
+	 * @note This call can trigger significant file size growth if run in
+	 * parallel with write transactions, because it employs a read-only
+	 * transaction. See long-lived transactions under @ref caveats_sec.
+	 * @param[in] env An environment handle returned by #mdb_env_create(). It
+	 * must have already been opened successfully.
+	 * @param[in] path The directory in which the copy will reside. This
+	 * directory must already exist and be writable but must otherwise be
+	 * empty.
+	 * @param[in] flags Special options for this operation. This parameter
+	 * must be set to 0 or by bitwise OR'ing together one or more of the
+	 * values described here.
+	 * <ul>
+	 *	<li>#MDB_CP_COMPACT - Perform compaction while copying: omit free
+	 *		pages and sequentially renumber all pages in output. This option
+	 *		consumes more CPU and runs more slowly than the default.
+	 *		Currently it fails if the environment has suffered a page leak.
+	 * </ul>
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int  mdb_env_copy2(MDB_env *env, const char *path, unsigned int flags);
+
+	/** @brief Copy an LMDB environment to the specified file descriptor,
+	 *	with options.
+	 *
+	 * This function may be used to make a backup of an existing environment.
+	 * No lockfile is created, since it gets recreated at need. See
+	 * #mdb_env_copy2() for further details.
+	 * @note This call can trigger significant file size growth if run in
+	 * parallel with write transactions, because it employs a read-only
+	 * transaction. See long-lived transactions under @ref caveats_sec.
+	 * @param[in] env An environment handle returned by #mdb_env_create(). It
+	 * must have already been opened successfully.
+	 * @param[in] fd The filedescriptor to write the copy to. It must
+	 * have already been opened for Write access.
+	 * @param[in] flags Special options for this operation.
+	 * See #mdb_env_copy2() for options.
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int  mdb_env_copyfd2(MDB_env *env, mdb_filehandle_t fd, unsigned int flags);
+
+	/** @brief Return statistics about the LMDB environment.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[out] stat The address of an #MDB_stat structure
+	 * 	where the statistics will be copied
+	 */
+int  mdb_env_stat(MDB_env *env, MDB_stat *stat);
+
+	/** @brief Return information about the LMDB environment.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[out] stat The address of an #MDB_envinfo structure
+	 * 	where the information will be copied
+	 */
+int  mdb_env_info(MDB_env *env, MDB_envinfo *stat);
+
+	/** @brief Flush the data buffers to disk.
+	 *
+	 * Data is always written to disk when #mdb_txn_commit() is called,
+	 * but the operating system may keep it buffered. LMDB always flushes
+	 * the OS buffers upon commit as well, unless the environment was
+	 * opened with #MDB_NOSYNC or in part #MDB_NOMETASYNC. This call is
+	 * not valid if the environment was opened with #MDB_RDONLY.
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] force If non-zero, force a synchronous flush.  Otherwise
+	 *  if the environment has the #MDB_NOSYNC flag set the flushes
+	 *	will be omitted, and with #MDB_MAPASYNC they will be asynchronous.
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EACCES - the environment is read-only.
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 *	<li>EIO - an error occurred during synchronization.
+	 * </ul>
+	 */
+int  mdb_env_sync(MDB_env *env, int force);
+
+	/** @brief Close the environment and release the memory map.
+	 *
+	 * Only a single thread may call this function. All transactions, databases,
+	 * and cursors must already be closed before calling this function. Attempts to
+	 * use any such handles after calling this function will cause a SIGSEGV.
+	 * The environment handle will be freed and must not be used again after this call.
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 */
+void mdb_env_close(MDB_env *env);
+
+	/** @brief Set environment flags.
+	 *
+	 * This may be used to set some flags in addition to those from
+	 * #mdb_env_open(), or to unset these flags.  If several threads
+	 * change the flags at the same time, the result is undefined.
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] flags The flags to change, bitwise OR'ed together
+	 * @param[in] onoff A non-zero value sets the flags, zero clears them.
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_env_set_flags(MDB_env *env, unsigned int flags, int onoff);
+
+	/** @brief Get environment flags.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[out] flags The address of an integer to store the flags
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_env_get_flags(MDB_env *env, unsigned int *flags);
+
+	/** @brief Return the path that was used in #mdb_env_open().
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[out] path Address of a string pointer to contain the path. This
+	 * is the actual string in the environment, not a copy. It should not be
+	 * altered in any way.
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_env_get_path(MDB_env *env, const char **path);
+
+	/** @brief Return the filedescriptor for the given environment.
+	 *
+	 * This function may be called after fork(), so the descriptor can be
+	 * closed before exec*().  Other LMDB file descriptors have FD_CLOEXEC.
+	 * (Until LMDB 0.9.18, only the lockfile had that.)
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[out] fd Address of a mdb_filehandle_t to contain the descriptor.
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_env_get_fd(MDB_env *env, mdb_filehandle_t *fd);
+
+	/** @brief Set the size of the memory map to use for this environment.
+	 *
+	 * The size should be a multiple of the OS page size. The default is
+	 * 10485760 bytes. The size of the memory map is also the maximum size
+	 * of the database. The value should be chosen as large as possible,
+	 * to accommodate future growth of the database.
+	 * This function should be called after #mdb_env_create() and before #mdb_env_open().
+	 * It may be called at later times if no transactions are active in
+	 * this process. Note that the library does not check for this condition,
+	 * the caller must ensure it explicitly.
+	 *
+	 * The new size takes effect immediately for the current process but
+	 * will not be persisted to any others until a write transaction has been
+	 * committed by the current process. Also, only mapsize increases are
+	 * persisted into the environment.
+	 *
+	 * If the mapsize is increased by another process, and data has grown
+	 * beyond the range of the current mapsize, #mdb_txn_begin() will
+	 * return #MDB_MAP_RESIZED. This function may be called with a size
+	 * of zero to adopt the new size.
+	 *
+	 * Any attempt to set a size smaller than the space already consumed
+	 * by the environment will be silently changed to the current size of the used space.
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] size The size in bytes
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified, or the environment has
+	 *   	an active write transaction.
+	 * </ul>
+	 */
+int  mdb_env_set_mapsize(MDB_env *env, size_t size);
+
+	/** @brief Set the maximum number of threads/reader slots for the environment.
+	 *
+	 * This defines the number of slots in the lock table that is used to track readers in the
+	 * the environment. The default is 126.
+	 * Starting a read-only transaction normally ties a lock table slot to the
+	 * current thread until the environment closes or the thread exits. If
+	 * MDB_NOTLS is in use, #mdb_txn_begin() instead ties the slot to the
+	 * MDB_txn object until it or the #MDB_env object is destroyed.
+	 * This function may only be called after #mdb_env_create() and before #mdb_env_open().
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] readers The maximum number of reader lock table slots
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified, or the environment is already open.
+	 * </ul>
+	 */
+int  mdb_env_set_maxreaders(MDB_env *env, unsigned int readers);
+
+	/** @brief Get the maximum number of threads/reader slots for the environment.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[out] readers Address of an integer to store the number of readers
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_env_get_maxreaders(MDB_env *env, unsigned int *readers);
+
+	/** @brief Set the maximum number of named databases for the environment.
+	 *
+	 * This function is only needed if multiple databases will be used in the
+	 * environment. Simpler applications that use the environment as a single
+	 * unnamed database can ignore this option.
+	 * This function may only be called after #mdb_env_create() and before #mdb_env_open().
+	 *
+	 * Currently a moderate number of slots are cheap but a huge number gets
+	 * expensive: 7-120 words per transaction, and every #mdb_dbi_open()
+	 * does a linear search of the opened slots.
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] dbs The maximum number of databases
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified, or the environment is already open.
+	 * </ul>
+	 */
+int  mdb_env_set_maxdbs(MDB_env *env, MDB_dbi dbs);
+
+	/** @brief Get the maximum size of keys and #MDB_DUPSORT data we can write.
+	 *
+	 * Depends on the compile-time constant #MDB_MAXKEYSIZE. Default 511.
+	 * See @ref MDB_val.
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @return The maximum size of a key we can write
+	 */
+int  mdb_env_get_maxkeysize(MDB_env *env);
+
+	/** @brief Set application information associated with the #MDB_env.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] ctx An arbitrary pointer for whatever the application needs.
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int  mdb_env_set_userctx(MDB_env *env, void *ctx);
+
+	/** @brief Get the application information associated with the #MDB_env.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @return The pointer set by #mdb_env_set_userctx().
+	 */
+void *mdb_env_get_userctx(MDB_env *env);
+
+	/** @brief A callback function for most LMDB assert() failures,
+	 * called before printing the message and aborting.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create().
+	 * @param[in] msg The assertion message, not including newline.
+	 */
+typedef void MDB_assert_func(MDB_env *env, const char *msg);
+
+	/** Set or reset the assert() callback of the environment.
+	 * Disabled if liblmdb is buillt with NDEBUG.
+	 * @note This hack should become obsolete as lmdb's error handling matures.
+	 * @param[in] env An environment handle returned by #mdb_env_create().
+	 * @param[in] func An #MDB_assert_func function, or 0.
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int  mdb_env_set_assert(MDB_env *env, MDB_assert_func *func);
+
+	/** @brief Create a transaction for use with the environment.
+	 *
+	 * The transaction handle may be discarded using #mdb_txn_abort() or #mdb_txn_commit().
+	 * @note A transaction and its cursors must only be used by a single
+	 * thread, and a thread may only have a single transaction at a time.
+	 * If #MDB_NOTLS is in use, this does not apply to read-only transactions.
+	 * @note Cursors may not span transactions.
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] parent If this parameter is non-NULL, the new transaction
+	 * will be a nested transaction, with the transaction indicated by \b parent
+	 * as its parent. Transactions may be nested to any level. A parent
+	 * transaction and its cursors may not issue any other operations than
+	 * mdb_txn_commit and mdb_txn_abort while it has active child transactions.
+	 * @param[in] flags Special options for this transaction. This parameter
+	 * must be set to 0 or by bitwise OR'ing together one or more of the
+	 * values described here.
+	 * <ul>
+	 *	<li>#MDB_RDONLY
+	 *		This transaction will not perform any write operations.
+	 * </ul>
+	 * @param[out] txn Address where the new #MDB_txn handle will be stored
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>#MDB_PANIC - a fatal error occurred earlier and the environment
+	 *		must be shut down.
+	 *	<li>#MDB_MAP_RESIZED - another process wrote data beyond this MDB_env's
+	 *		mapsize and this environment's map must be resized as well.
+	 *		See #mdb_env_set_mapsize().
+	 *	<li>#MDB_READERS_FULL - a read-only transaction was requested and
+	 *		the reader lock table is full. See #mdb_env_set_maxreaders().
+	 *	<li>ENOMEM - out of memory.
+	 * </ul>
+	 */
+int  mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **txn);
+
+	/** @brief Returns the transaction's #MDB_env
+	 *
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 */
+MDB_env *mdb_txn_env(MDB_txn *txn);
+
+	/** @brief Return the transaction's ID.
+	 *
+	 * This returns the identifier associated with this transaction. For a
+	 * read-only transaction, this corresponds to the snapshot being read;
+	 * concurrent readers will frequently have the same transaction ID.
+	 *
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @return A transaction ID, valid if input is an active transaction.
+	 */
+size_t mdb_txn_id(MDB_txn *txn);
+
+	/** @brief Commit all the operations of a transaction into the database.
+	 *
+	 * The transaction handle is freed. It and its cursors must not be used
+	 * again after this call, except with #mdb_cursor_renew().
+	 * @note Earlier documentation incorrectly said all cursors would be freed.
+	 * Only write-transactions free cursors.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 *	<li>ENOSPC - no more disk space.
+	 *	<li>EIO - a low-level I/O error occurred while writing.
+	 *	<li>ENOMEM - out of memory.
+	 * </ul>
+	 */
+int  mdb_txn_commit(MDB_txn *txn);
+
+	/** @brief Abandon all the operations of the transaction instead of saving them.
+	 *
+	 * The transaction handle is freed. It and its cursors must not be used
+	 * again after this call, except with #mdb_cursor_renew().
+	 * @note Earlier documentation incorrectly said all cursors would be freed.
+	 * Only write-transactions free cursors.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 */
+void mdb_txn_abort(MDB_txn *txn);
+
+	/** @brief Reset a read-only transaction.
+	 *
+	 * Abort the transaction like #mdb_txn_abort(), but keep the transaction
+	 * handle. #mdb_txn_renew() may reuse the handle. This saves allocation
+	 * overhead if the process will start a new read-only transaction soon,
+	 * and also locking overhead if #MDB_NOTLS is in use. The reader table
+	 * lock is released, but the table slot stays tied to its thread or
+	 * #MDB_txn. Use mdb_txn_abort() to discard a reset handle, and to free
+	 * its lock table slot if MDB_NOTLS is in use.
+	 * Cursors opened within the transaction must not be used
+	 * again after this call, except with #mdb_cursor_renew().
+	 * Reader locks generally don't interfere with writers, but they keep old
+	 * versions of database pages allocated. Thus they prevent the old pages
+	 * from being reused when writers commit new data, and so under heavy load
+	 * the database size may grow much more rapidly than otherwise.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 */
+void mdb_txn_reset(MDB_txn *txn);
+
+	/** @brief Renew a read-only transaction.
+	 *
+	 * This acquires a new reader lock for a transaction handle that had been
+	 * released by #mdb_txn_reset(). It must be called before a reset transaction
+	 * may be used again.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>#MDB_PANIC - a fatal error occurred earlier and the environment
+	 *		must be shut down.
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_txn_renew(MDB_txn *txn);
+
+/** Compat with version <= 0.9.4, avoid clash with libmdb from MDB Tools project */
+#define mdb_open(txn,name,flags,dbi)	mdb_dbi_open(txn,name,flags,dbi)
+/** Compat with version <= 0.9.4, avoid clash with libmdb from MDB Tools project */
+#define mdb_close(env,dbi)				mdb_dbi_close(env,dbi)
+
+	/** @brief Open a database in the environment.
+	 *
+	 * A database handle denotes the name and parameters of a database,
+	 * independently of whether such a database exists.
+	 * The database handle may be discarded by calling #mdb_dbi_close().
+	 * The old database handle is returned if the database was already open.
+	 * The handle may only be closed once.
+	 *
+	 * The database handle will be private to the current transaction until
+	 * the transaction is successfully committed. If the transaction is
+	 * aborted the handle will be closed automatically.
+	 * After a successful commit the handle will reside in the shared
+	 * environment, and may be used by other transactions.
+	 *
+	 * This function must not be called from multiple concurrent
+	 * transactions in the same process. A transaction that uses
+	 * this function must finish (either commit or abort) before
+	 * any other transaction in the process may use this function.
+	 *
+	 * To use named databases (with name != NULL), #mdb_env_set_maxdbs()
+	 * must be called before opening the environment.  Database names are
+	 * keys in the unnamed database, and may be read but not written.
+	 *
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] name The name of the database to open. If only a single
+	 * 	database is needed in the environment, this value may be NULL.
+	 * @param[in] flags Special options for this database. This parameter
+	 * must be set to 0 or by bitwise OR'ing together one or more of the
+	 * values described here.
+	 * <ul>
+	 *	<li>#MDB_REVERSEKEY
+	 *		Keys are strings to be compared in reverse order, from the end
+	 *		of the strings to the beginning. By default, Keys are treated as strings and
+	 *		compared from beginning to end.
+	 *	<li>#MDB_DUPSORT
+	 *		Duplicate keys may be used in the database. (Or, from another perspective,
+	 *		keys may have multiple data items, stored in sorted order.) By default
+	 *		keys must be unique and may have only a single data item.
+	 *	<li>#MDB_INTEGERKEY
+	 *		Keys are binary integers in native byte order, either unsigned int
+	 *		or size_t, and will be sorted as such.
+	 *		The keys must all be of the same size.
+	 *	<li>#MDB_DUPFIXED
+	 *		This flag may only be used in combination with #MDB_DUPSORT. This option
+	 *		tells the library that the data items for this database are all the same
+	 *		size, which allows further optimizations in storage and retrieval. When
+	 *		all data items are the same size, the #MDB_GET_MULTIPLE, #MDB_NEXT_MULTIPLE
+	 *		and #MDB_PREV_MULTIPLE cursor operations may be used to retrieve multiple
+	 *		items at once.
+	 *	<li>#MDB_INTEGERDUP
+	 *		This option specifies that duplicate data items are binary integers,
+	 *		similar to #MDB_INTEGERKEY keys.
+	 *	<li>#MDB_REVERSEDUP
+	 *		This option specifies that duplicate data items should be compared as
+	 *		strings in reverse order.
+	 *	<li>#MDB_CREATE
+	 *		Create the named database if it doesn't exist. This option is not
+	 *		allowed in a read-only transaction or a read-only environment.
+	 * </ul>
+	 * @param[out] dbi Address where the new #MDB_dbi handle will be stored
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>#MDB_NOTFOUND - the specified database doesn't exist in the environment
+	 *		and #MDB_CREATE was not specified.
+	 *	<li>#MDB_DBS_FULL - too many databases have been opened. See #mdb_env_set_maxdbs().
+	 * </ul>
+	 */
+int  mdb_dbi_open(MDB_txn *txn, const char *name, unsigned int flags, MDB_dbi *dbi);
+
+	/** @brief Retrieve statistics for a database.
+	 *
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[out] stat The address of an #MDB_stat structure
+	 * 	where the statistics will be copied
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_stat(MDB_txn *txn, MDB_dbi dbi, MDB_stat *stat);
+
+	/** @brief Retrieve the DB flags for a database handle.
+	 *
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[out] flags Address where the flags will be returned.
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int mdb_dbi_flags(MDB_txn *txn, MDB_dbi dbi, unsigned int *flags);
+
+	/** @brief Close a database handle. Normally unnecessary. Use with care:
+	 *
+	 * This call is not mutex protected. Handles should only be closed by
+	 * a single thread, and only if no other threads are going to reference
+	 * the database handle or one of its cursors any further. Do not close
+	 * a handle if an existing transaction has modified its database.
+	 * Doing so can cause misbehavior from database corruption to errors
+	 * like MDB_BAD_VALSIZE (since the DB name is gone).
+	 *
+	 * Closing a database handle is not necessary, but lets #mdb_dbi_open()
+	 * reuse the handle value.  Usually it's better to set a bigger
+	 * #mdb_env_set_maxdbs(), unless that value would be large.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 */
+void mdb_dbi_close(MDB_env *env, MDB_dbi dbi);
+
+	/** @brief Empty or delete+close a database.
+	 *
+	 * See #mdb_dbi_close() for restrictions about closing the DB handle.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] del 0 to empty the DB, 1 to delete it from the
+	 * environment and close the DB handle.
+	 * @return A non-zero error value on failure and 0 on success.
+	 */
+int  mdb_drop(MDB_txn *txn, MDB_dbi dbi, int del);
+
+	/** @brief Set a custom key comparison function for a database.
+	 *
+	 * The comparison function is called whenever it is necessary to compare a
+	 * key specified by the application with a key currently stored in the database.
+	 * If no comparison function is specified, and no special key flags were specified
+	 * with #mdb_dbi_open(), the keys are compared lexically, with shorter keys collating
+	 * before longer keys.
+	 * @warning This function must be called before any data access functions are used,
+	 * otherwise data corruption may occur. The same comparison function must be used by every
+	 * program accessing the database, every time the database is used.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] cmp A #MDB_cmp_func function
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_set_compare(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp);
+
+	/** @brief Set a custom data comparison function for a #MDB_DUPSORT database.
+	 *
+	 * This comparison function is called whenever it is necessary to compare a data
+	 * item specified by the application with a data item currently stored in the database.
+	 * This function only takes effect if the database was opened with the #MDB_DUPSORT
+	 * flag.
+	 * If no comparison function is specified, and no special key flags were specified
+	 * with #mdb_dbi_open(), the data items are compared lexically, with shorter items collating
+	 * before longer items.
+	 * @warning This function must be called before any data access functions are used,
+	 * otherwise data corruption may occur. The same comparison function must be used by every
+	 * program accessing the database, every time the database is used.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] cmp A #MDB_cmp_func function
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_set_dupsort(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp);
+
+	/** @brief Set a relocation function for a #MDB_FIXEDMAP database.
+	 *
+	 * @todo The relocation function is called whenever it is necessary to move the data
+	 * of an item to a different position in the database (e.g. through tree
+	 * balancing operations, shifts as a result of adds or deletes, etc.). It is
+	 * intended to allow address/position-dependent data items to be stored in
+	 * a database in an environment opened with the #MDB_FIXEDMAP option.
+	 * Currently the relocation feature is unimplemented and setting
+	 * this function has no effect.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] rel A #MDB_rel_func function
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_set_relfunc(MDB_txn *txn, MDB_dbi dbi, MDB_rel_func *rel);
+
+	/** @brief Set a context pointer for a #MDB_FIXEDMAP database's relocation function.
+	 *
+	 * See #mdb_set_relfunc and #MDB_rel_func for more details.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] ctx An arbitrary pointer for whatever the application needs.
+	 * It will be passed to the callback function set by #mdb_set_relfunc
+	 * as its \b relctx parameter whenever the callback is invoked.
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_set_relctx(MDB_txn *txn, MDB_dbi dbi, void *ctx);
+
+	/** @brief Get items from a database.
+	 *
+	 * This function retrieves key/data pairs from the database. The address
+	 * and length of the data associated with the specified \b key are returned
+	 * in the structure to which \b data refers.
+	 * If the database supports duplicate keys (#MDB_DUPSORT) then the
+	 * first data item for the key will be returned. Retrieval of other
+	 * items requires the use of #mdb_cursor_get().
+	 *
+	 * @note The memory pointed to by the returned values is owned by the
+	 * database. The caller need not dispose of the memory, and may not
+	 * modify it in any way. For values returned in a read-only transaction
+	 * any modification attempts will cause a SIGSEGV.
+	 * @note Values returned from the database are valid only until a
+	 * subsequent update operation, or the end of the transaction.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] key The key to search for in the database
+	 * @param[out] data The data corresponding to the key
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>#MDB_NOTFOUND - the key was not in the database.
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_get(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data);
+
+	/** @brief Store items into a database.
+	 *
+	 * This function stores key/data pairs in the database. The default behavior
+	 * is to enter the new key/data pair, replacing any previously existing key
+	 * if duplicates are disallowed, or adding a duplicate data item if
+	 * duplicates are allowed (#MDB_DUPSORT).
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] key The key to store in the database
+	 * @param[in,out] data The data to store
+	 * @param[in] flags Special options for this operation. This parameter
+	 * must be set to 0 or by bitwise OR'ing together one or more of the
+	 * values described here.
+	 * <ul>
+	 *	<li>#MDB_NODUPDATA - enter the new key/data pair only if it does not
+	 *		already appear in the database. This flag may only be specified
+	 *		if the database was opened with #MDB_DUPSORT. The function will
+	 *		return #MDB_KEYEXIST if the key/data pair already appears in the
+	 *		database.
+	 *	<li>#MDB_NOOVERWRITE - enter the new key/data pair only if the key
+	 *		does not already appear in the database. The function will return
+	 *		#MDB_KEYEXIST if the key already appears in the database, even if
+	 *		the database supports duplicates (#MDB_DUPSORT). The \b data
+	 *		parameter will be set to point to the existing item.
+	 *	<li>#MDB_RESERVE - reserve space for data of the given size, but
+	 *		don't copy the given data. Instead, return a pointer to the
+	 *		reserved space, which the caller can fill in later - before
+	 *		the next update operation or the transaction ends. This saves
+	 *		an extra memcpy if the data is being generated later.
+	 *		LMDB does nothing else with this memory, the caller is expected
+	 *		to modify all of the space requested. This flag must not be
+	 *		specified if the database was opened with #MDB_DUPSORT.
+	 *	<li>#MDB_APPEND - append the given key/data pair to the end of the
+	 *		database. This option allows fast bulk loading when keys are
+	 *		already known to be in the correct order. Loading unsorted keys
+	 *		with this flag will cause a #MDB_KEYEXIST error.
+	 *	<li>#MDB_APPENDDUP - as above, but for sorted dup data.
+	 * </ul>
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>#MDB_MAP_FULL - the database is full, see #mdb_env_set_mapsize().
+	 *	<li>#MDB_TXN_FULL - the transaction has too many dirty pages.
+	 *	<li>EACCES - an attempt was made to write in a read-only transaction.
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_put(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data,
+			    unsigned int flags);
+
+	/** @brief Delete items from a database.
+	 *
+	 * This function removes key/data pairs from the database.
+	 * If the database does not support sorted duplicate data items
+	 * (#MDB_DUPSORT) the data parameter is ignored.
+	 * If the database supports sorted duplicates and the data parameter
+	 * is NULL, all of the duplicate data items for the key will be
+	 * deleted. Otherwise, if the data parameter is non-NULL
+	 * only the matching data item will be deleted.
+	 * This function will return #MDB_NOTFOUND if the specified key/data
+	 * pair is not in the database.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] key The key to delete from the database
+	 * @param[in] data The data to delete
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EACCES - an attempt was made to write in a read-only transaction.
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_del(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data);
+
+	/** @brief Create a cursor handle.
+	 *
+	 * A cursor is associated with a specific transaction and database.
+	 * A cursor cannot be used when its database handle is closed.  Nor
+	 * when its transaction has ended, except with #mdb_cursor_renew().
+	 * It can be discarded with #mdb_cursor_close().
+	 * A cursor in a write-transaction can be closed before its transaction
+	 * ends, and will otherwise be closed when its transaction ends.
+	 * A cursor in a read-only transaction must be closed explicitly, before
+	 * or after its transaction ends. It can be reused with
+	 * #mdb_cursor_renew() before finally closing it.
+	 * @note Earlier documentation said that cursors in every transaction
+	 * were closed when the transaction committed or aborted.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[out] cursor Address where the new #MDB_cursor handle will be stored
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_cursor_open(MDB_txn *txn, MDB_dbi dbi, MDB_cursor **cursor);
+
+	/** @brief Close a cursor handle.
+	 *
+	 * The cursor handle will be freed and must not be used again after this call.
+	 * Its transaction must still be live if it is a write-transaction.
+	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+	 */
+void mdb_cursor_close(MDB_cursor *cursor);
+
+	/** @brief Renew a cursor handle.
+	 *
+	 * A cursor is associated with a specific transaction and database.
+	 * Cursors that are only used in read-only
+	 * transactions may be re-used, to avoid unnecessary malloc/free overhead.
+	 * The cursor may be associated with a new read-only transaction, and
+	 * referencing the same database handle as it was created with.
+	 * This may be done whether the previous transaction is live or dead.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_cursor_renew(MDB_txn *txn, MDB_cursor *cursor);
+
+	/** @brief Return the cursor's transaction handle.
+	 *
+	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+	 */
+MDB_txn *mdb_cursor_txn(MDB_cursor *cursor);
+
+	/** @brief Return the cursor's database handle.
+	 *
+	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+	 */
+MDB_dbi mdb_cursor_dbi(MDB_cursor *cursor);
+
+	/** @brief Retrieve by cursor.
+	 *
+	 * This function retrieves key/data pairs from the database. The address and length
+	 * of the key are returned in the object to which \b key refers (except for the
+	 * case of the #MDB_SET option, in which the \b key object is unchanged), and
+	 * the address and length of the data are returned in the object to which \b data
+	 * refers.
+	 * See #mdb_get() for restrictions on using the output values.
+	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+	 * @param[in,out] key The key for a retrieved item
+	 * @param[in,out] data The data of a retrieved item
+	 * @param[in] op A cursor operation #MDB_cursor_op
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>#MDB_NOTFOUND - no matching key found.
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_cursor_get(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
+			    MDB_cursor_op op);
+
+	/** @brief Store by cursor.
+	 *
+	 * This function stores key/data pairs into the database.
+	 * The cursor is positioned at the new item, or on failure usually near it.
+	 * @note Earlier documentation incorrectly said errors would leave the
+	 * state of the cursor unchanged.
+	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+	 * @param[in] key The key operated on.
+	 * @param[in] data The data operated on.
+	 * @param[in] flags Options for this operation. This parameter
+	 * must be set to 0 or one of the values described here.
+	 * <ul>
+	 *	<li>#MDB_CURRENT - replace the item at the current cursor position.
+	 *		The \b key parameter must still be provided, and must match it.
+	 *		If using sorted duplicates (#MDB_DUPSORT) the data item must still
+	 *		sort into the same place. This is intended to be used when the
+	 *		new data is the same size as the old. Otherwise it will simply
+	 *		perform a delete of the old record followed by an insert.
+	 *	<li>#MDB_NODUPDATA - enter the new key/data pair only if it does not
+	 *		already appear in the database. This flag may only be specified
+	 *		if the database was opened with #MDB_DUPSORT. The function will
+	 *		return #MDB_KEYEXIST if the key/data pair already appears in the
+	 *		database.
+	 *	<li>#MDB_NOOVERWRITE - enter the new key/data pair only if the key
+	 *		does not already appear in the database. The function will return
+	 *		#MDB_KEYEXIST if the key already appears in the database, even if
+	 *		the database supports duplicates (#MDB_DUPSORT).
+	 *	<li>#MDB_RESERVE - reserve space for data of the given size, but
+	 *		don't copy the given data. Instead, return a pointer to the
+	 *		reserved space, which the caller can fill in later - before
+	 *		the next update operation or the transaction ends. This saves
+	 *		an extra memcpy if the data is being generated later. This flag
+	 *		must not be specified if the database was opened with #MDB_DUPSORT.
+	 *	<li>#MDB_APPEND - append the given key/data pair to the end of the
+	 *		database. No key comparisons are performed. This option allows
+	 *		fast bulk loading when keys are already known to be in the
+	 *		correct order. Loading unsorted keys with this flag will cause
+	 *		a #MDB_KEYEXIST error.
+	 *	<li>#MDB_APPENDDUP - as above, but for sorted dup data.
+	 *	<li>#MDB_MULTIPLE - store multiple contiguous data elements in a
+	 *		single request. This flag may only be specified if the database
+	 *		was opened with #MDB_DUPFIXED. The \b data argument must be an
+	 *		array of two MDB_vals. The mv_size of the first MDB_val must be
+	 *		the size of a single data element. The mv_data of the first MDB_val
+	 *		must point to the beginning of the array of contiguous data elements.
+	 *		The mv_size of the second MDB_val must be the count of the number
+	 *		of data elements to store. On return this field will be set to
+	 *		the count of the number of elements actually written. The mv_data
+	 *		of the second MDB_val is unused.
+	 * </ul>
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>#MDB_MAP_FULL - the database is full, see #mdb_env_set_mapsize().
+	 *	<li>#MDB_TXN_FULL - the transaction has too many dirty pages.
+	 *	<li>EACCES - an attempt was made to write in a read-only transaction.
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_cursor_put(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
+				unsigned int flags);
+
+	/** @brief Delete current key/data pair
+	 *
+	 * This function deletes the key/data pair to which the cursor refers.
+	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+	 * @param[in] flags Options for this operation. This parameter
+	 * must be set to 0 or one of the values described here.
+	 * <ul>
+	 *	<li>#MDB_NODUPDATA - delete all of the data items for the current key.
+	 *		This flag may only be specified if the database was opened with #MDB_DUPSORT.
+	 * </ul>
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EACCES - an attempt was made to write in a read-only transaction.
+	 *	<li>EINVAL - an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_cursor_del(MDB_cursor *cursor, unsigned int flags);
+
+	/** @brief Return count of duplicates for current key.
+	 *
+	 * This call is only valid on databases that support sorted duplicate
+	 * data items #MDB_DUPSORT.
+	 * @param[in] cursor A cursor handle returned by #mdb_cursor_open()
+	 * @param[out] countp Address where the count will be stored
+	 * @return A non-zero error value on failure and 0 on success. Some possible
+	 * errors are:
+	 * <ul>
+	 *	<li>EINVAL - cursor is not initialized, or an invalid parameter was specified.
+	 * </ul>
+	 */
+int  mdb_cursor_count(MDB_cursor *cursor, size_t *countp);
+
+	/** @brief Compare two data items according to a particular database.
+	 *
+	 * This returns a comparison as if the two data items were keys in the
+	 * specified database.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] a The first item to compare
+	 * @param[in] b The second item to compare
+	 * @return < 0 if a < b, 0 if a == b, > 0 if a > b
+	 */
+int  mdb_cmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b);
+
+	/** @brief Compare two data items according to a particular database.
+	 *
+	 * This returns a comparison as if the two items were data items of
+	 * the specified database. The database must have the #MDB_DUPSORT flag.
+	 * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+	 * @param[in] dbi A database handle returned by #mdb_dbi_open()
+	 * @param[in] a The first item to compare
+	 * @param[in] b The second item to compare
+	 * @return < 0 if a < b, 0 if a == b, > 0 if a > b
+	 */
+int  mdb_dcmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b);
+
+	/** @brief A callback function used to print a message from the library.
+	 *
+	 * @param[in] msg The string to be printed.
+	 * @param[in] ctx An arbitrary context pointer for the callback.
+	 * @return < 0 on failure, >= 0 on success.
+	 */
+typedef int (MDB_msg_func)(const char *msg, void *ctx);
+
+	/** @brief Dump the entries in the reader lock table.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[in] func A #MDB_msg_func function
+	 * @param[in] ctx Anything the message function needs
+	 * @return < 0 on failure, >= 0 on success.
+	 */
+int	mdb_reader_list(MDB_env *env, MDB_msg_func *func, void *ctx);
+
+	/** @brief Check for stale entries in the reader lock table.
+	 *
+	 * @param[in] env An environment handle returned by #mdb_env_create()
+	 * @param[out] dead Number of stale slots that were cleared
+	 * @return 0 on success, non-zero on failure.
+	 */
+int	mdb_reader_check(MDB_env *env, int *dead);
+/**	@} */
+
+#ifdef __cplusplus
+}
+#endif
+/** @page tools LMDB Command Line Tools
+	The following describes the command line tools that are available for LMDB.
+	\li \ref mdb_copy_1
+	\li \ref mdb_dump_1
+	\li \ref mdb_load_1
+	\li \ref mdb_stat_1
+*/
+
+#endif /* _LMDB_H_ */
diff --git a/src/contrib/lmdb/mdb.c b/src/contrib/lmdb/mdb.c
new file mode 100644
index 0000000..d9e7c5e
--- /dev/null
+++ b/src/contrib/lmdb/mdb.c
@@ -0,0 +1,10266 @@
+/** @file mdb.c
+ *	@brief Lightning memory-mapped database library
+ *
+ *	A Btree-based database management library modeled loosely on the
+ *	BerkeleyDB API, but much simplified.
+ */
+/*
+ * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ *
+ * This code is derived from btree.c written by Martin Hedenfalk.
+ *
+ * Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE 1
+#endif
+#if defined(__WIN64__)
+#define _FILE_OFFSET_BITS	64
+#endif
+#ifdef _WIN32
+#include <malloc.h>
+#include <windows.h>
+#include <wchar.h>				/* get wcscpy() */
+
+/** getpid() returns int; MinGW defines pid_t but MinGW64 typedefs it
+ *  as int64 which is wrong. MSVC doesn't define it at all, so just
+ *  don't use it.
+ */
+#define MDB_PID_T	int
+#define MDB_THR_T	DWORD
+#include <sys/types.h>
+#include <sys/stat.h>
+#ifdef __GNUC__
+# include <sys/param.h>
+#else
+# define LITTLE_ENDIAN	1234
+# define BIG_ENDIAN	4321
+# define BYTE_ORDER	LITTLE_ENDIAN
+# ifndef SSIZE_MAX
+#  define SSIZE_MAX	INT_MAX
+# endif
+#endif
+#else
+#include <sys/types.h>
+#include <sys/stat.h>
+#define MDB_PID_T	pid_t
+#define MDB_THR_T	pthread_t
+#include <sys/param.h>
+#include <sys/uio.h>
+#include <sys/mman.h>
+#ifdef HAVE_SYS_FILE_H
+#include <sys/file.h>
+#endif
+#include <fcntl.h>
+#endif
+
+#if defined(__mips) && defined(__linux)
+/* MIPS has cache coherency issues, requires explicit cache control */
+#include <asm/cachectl.h>
+extern int cacheflush(char *addr, int nbytes, int cache);
+#define CACHEFLUSH(addr, bytes, cache)	cacheflush(addr, bytes, cache)
+#else
+#define CACHEFLUSH(addr, bytes, cache)
+#endif
+
+#if defined(__linux) && !defined(MDB_FDATASYNC_WORKS)
+/** fdatasync is broken on ext3/ext4fs on older kernels, see
+ *	description in #mdb_env_open2 comments. You can safely
+ *	define MDB_FDATASYNC_WORKS if this code will only be run
+ *	on kernels 3.6 and newer.
+ */
+#define	BROKEN_FDATASYNC
+#endif
+
+#include <errno.h>
+#include <limits.h>
+#include <stddef.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#ifdef _MSC_VER
+#include <io.h>
+typedef SSIZE_T	ssize_t;
+#else
+#include <unistd.h>
+#endif
+
+#if defined(__sun) || defined(ANDROID)
+/* Most platforms have posix_memalign, older may only have memalign */
+#define HAVE_MEMALIGN	1
+#include <malloc.h>
+/* On Solaris, we need the POSIX sigwait function */
+#if defined (__sun)
+# define _POSIX_PTHREAD_SEMANTICS	1
+#endif
+#endif
+
+#if !(defined(BYTE_ORDER) || defined(__BYTE_ORDER))
+#include <netinet/in.h>
+#include <resolv.h>	/* defines BYTE_ORDER on HPUX and Solaris */
+#endif
+
+#if defined(__APPLE__) || defined (BSD) || defined(__FreeBSD_kernel__)
+# define MDB_USE_POSIX_SEM	1
+# define MDB_FDATASYNC		fsync
+#elif defined(ANDROID)
+# define MDB_FDATASYNC		fsync
+#endif
+
+#ifndef _WIN32
+#include <pthread.h>
+#include <signal.h>
+#ifdef MDB_USE_POSIX_SEM
+# define MDB_USE_HASH		1
+#include <semaphore.h>
+#else
+#define MDB_USE_POSIX_MUTEX	1
+#endif
+#endif
+
+#if defined(_WIN32) + defined(MDB_USE_POSIX_SEM) \
+	+ defined(MDB_USE_POSIX_MUTEX) != 1
+# error "Ambiguous shared-lock implementation"
+#endif
+
+#ifdef USE_VALGRIND
+#include <valgrind/memcheck.h>
+#define VGMEMP_CREATE(h,r,z)    VALGRIND_CREATE_MEMPOOL(h,r,z)
+#define VGMEMP_ALLOC(h,a,s) VALGRIND_MEMPOOL_ALLOC(h,a,s)
+#define VGMEMP_FREE(h,a) VALGRIND_MEMPOOL_FREE(h,a)
+#define VGMEMP_DESTROY(h)	VALGRIND_DESTROY_MEMPOOL(h)
+#define VGMEMP_DEFINED(a,s)	VALGRIND_MAKE_MEM_DEFINED(a,s)
+#else
+#define VGMEMP_CREATE(h,r,z)
+#define VGMEMP_ALLOC(h,a,s)
+#define VGMEMP_FREE(h,a)
+#define VGMEMP_DESTROY(h)
+#define VGMEMP_DEFINED(a,s)
+#endif
+
+#ifndef BYTE_ORDER
+# if (defined(_LITTLE_ENDIAN) || defined(_BIG_ENDIAN)) && !(defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN))
+/* Solaris just defines one or the other */
+#  define LITTLE_ENDIAN	1234
+#  define BIG_ENDIAN	4321
+#  ifdef _LITTLE_ENDIAN
+#   define BYTE_ORDER  LITTLE_ENDIAN
+#  else
+#   define BYTE_ORDER  BIG_ENDIAN
+#  endif
+# else
+#  define BYTE_ORDER   __BYTE_ORDER
+# endif
+#endif
+
+#ifndef LITTLE_ENDIAN
+#define LITTLE_ENDIAN	__LITTLE_ENDIAN
+#endif
+#ifndef BIG_ENDIAN
+#define BIG_ENDIAN	__BIG_ENDIAN
+#endif
+
+#if defined(__i386) || defined(__x86_64) || defined(_M_IX86)
+#define MISALIGNED_OK	1
+#endif
+
+#include "lmdb.h"
+#include "midl.h"
+
+#if (BYTE_ORDER == LITTLE_ENDIAN) == (BYTE_ORDER == BIG_ENDIAN)
+# error "Unknown or unsupported endianness (BYTE_ORDER)"
+#elif (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
+# error "Two's complement, reasonably sized integer types, please"
+#endif
+
+#ifdef __GNUC__
+/** Put infrequently used env functions in separate section */
+# ifdef __APPLE__
+#  define	ESECT	__attribute__ ((section("__TEXT,text_env")))
+# else
+#  define	ESECT	__attribute__ ((section("text_env")))
+# endif
+#else
+#define ESECT
+#endif
+
+#ifdef _WIN32
+#define CALL_CONV WINAPI
+#else
+#define CALL_CONV
+#endif
+
+/** @defgroup internal	LMDB Internals
+ *	@{
+ */
+/** @defgroup compat	Compatibility Macros
+ *	A bunch of macros to minimize the amount of platform-specific ifdefs
+ *	needed throughout the rest of the code. When the features this library
+ *	needs are similar enough to POSIX to be hidden in a one-or-two line
+ *	replacement, this macro approach is used.
+ *	@{
+ */
+
+	/** Features under development */
+#ifndef MDB_DEVEL
+#define MDB_DEVEL 0
+#endif
+
+	/** Wrapper around __func__, which is a C99 feature */
+#if __STDC_VERSION__ >= 199901L
+# define mdb_func_	__func__
+#elif __GNUC__ >= 2 || _MSC_VER >= 1300
+# define mdb_func_	__FUNCTION__
+#else
+/* If a debug message says <mdb_unknown>(), update the #if statements above */
+# define mdb_func_	"<mdb_unknown>"
+#endif
+
+/* Internal error codes, not exposed outside liblmdb */
+#define	MDB_NO_ROOT		(MDB_LAST_ERRCODE + 10)
+#ifdef _WIN32
+#define MDB_OWNERDEAD	((int) WAIT_ABANDONED)
+#elif defined(MDB_USE_POSIX_MUTEX) && defined(EOWNERDEAD)
+#define MDB_OWNERDEAD	EOWNERDEAD	/**< #LOCK_MUTEX0() result if dead owner */
+#endif
+
+#ifdef __GLIBC__
+#define	GLIBC_VER	((__GLIBC__ << 16 )| __GLIBC_MINOR__)
+#endif
+/** Some platforms define the EOWNERDEAD error code
+ * even though they don't support Robust Mutexes.
+ * Compile with -DMDB_USE_ROBUST=0, or use some other
+ * mechanism like -DMDB_USE_POSIX_SEM instead of
+ * -DMDB_USE_POSIX_MUTEX.
+ * (Posix semaphores are not robust.)
+ */
+#ifndef MDB_USE_ROBUST
+/* Android currently lacks Robust Mutex support. So does glibc < 2.4. */
+# if defined(MDB_USE_POSIX_MUTEX) && (defined(ANDROID) || \
+	(defined(__GLIBC__) && GLIBC_VER < 0x020004))
+#  define MDB_USE_ROBUST	0
+# else
+#  define MDB_USE_ROBUST	1
+# endif
+#endif /* !MDB_USE_ROBUST */
+
+#if defined(MDB_USE_POSIX_MUTEX) && (MDB_USE_ROBUST)
+/* glibc < 2.12 only provided _np API */
+#  if (defined(__GLIBC__) && GLIBC_VER < 0x02000c) || \
+	(defined(PTHREAD_MUTEX_ROBUST_NP) && !defined(PTHREAD_MUTEX_ROBUST))
+#   define PTHREAD_MUTEX_ROBUST	PTHREAD_MUTEX_ROBUST_NP
+#   define pthread_mutexattr_setrobust(attr, flag)	pthread_mutexattr_setrobust_np(attr, flag)
+#   define pthread_mutex_consistent(mutex)	pthread_mutex_consistent_np(mutex)
+#  endif
+#endif /* MDB_USE_POSIX_MUTEX && MDB_USE_ROBUST */
+
+#if defined(MDB_OWNERDEAD) && (MDB_USE_ROBUST)
+#define MDB_ROBUST_SUPPORTED	1
+#endif
+
+#ifdef _WIN32
+#define MDB_USE_HASH	1
+#define MDB_PIDLOCK	0
+#define THREAD_RET	DWORD
+#define pthread_t	HANDLE
+#define pthread_mutex_t	HANDLE
+#define pthread_cond_t	HANDLE
+typedef HANDLE mdb_mutex_t, mdb_mutexref_t;
+#define pthread_key_t	DWORD
+#define pthread_self()	GetCurrentThreadId()
+#define pthread_key_create(x,y)	\
+	((*(x) = TlsAlloc()) == TLS_OUT_OF_INDEXES ? ErrCode() : 0)
+#define pthread_key_delete(x)	TlsFree(x)
+#define pthread_getspecific(x)	TlsGetValue(x)
+#define pthread_setspecific(x,y)	(TlsSetValue(x,y) ? 0 : ErrCode())
+#define pthread_mutex_unlock(x)	ReleaseMutex(*x)
+#define pthread_mutex_lock(x)	WaitForSingleObject(*x, INFINITE)
+#define pthread_cond_signal(x)	SetEvent(*x)
+#define pthread_cond_wait(cond,mutex)	do{SignalObjectAndWait(*mutex, *cond, INFINITE, FALSE); WaitForSingleObject(*mutex, INFINITE);}while(0)
+#define THREAD_CREATE(thr,start,arg) \
+	(((thr) = CreateThread(NULL, 0, start, arg, 0, NULL)) ? 0 : ErrCode())
+#define THREAD_FINISH(thr) \
+	(WaitForSingleObject(thr, INFINITE) ? ErrCode() : 0)
+#define LOCK_MUTEX0(mutex)		WaitForSingleObject(mutex, INFINITE)
+#define UNLOCK_MUTEX(mutex)		ReleaseMutex(mutex)
+#define mdb_mutex_consistent(mutex)	0
+#define getpid()	GetCurrentProcessId()
+#define	MDB_FDATASYNC(fd)	(!FlushFileBuffers(fd))
+#define	MDB_MSYNC(addr,len,flags)	(!FlushViewOfFile(addr,len))
+#define	ErrCode()	GetLastError()
+#define GET_PAGESIZE(x) {SYSTEM_INFO si; GetSystemInfo(&si); (x) = si.dwPageSize;}
+#define	close(fd)	(CloseHandle(fd) ? 0 : -1)
+#define	munmap(ptr,len)	UnmapViewOfFile(ptr)
+#ifdef PROCESS_QUERY_LIMITED_INFORMATION
+#define MDB_PROCESS_QUERY_LIMITED_INFORMATION PROCESS_QUERY_LIMITED_INFORMATION
+#else
+#define MDB_PROCESS_QUERY_LIMITED_INFORMATION 0x1000
+#endif
+#define	Z	"I"
+#else
+#define THREAD_RET	void *
+#define THREAD_CREATE(thr,start,arg)	pthread_create(&thr,NULL,start,arg)
+#define THREAD_FINISH(thr)	pthread_join(thr,NULL)
+#define	Z	"z"			/**< printf format modifier for size_t */
+
+	/** For MDB_LOCK_FORMAT: True if readers take a pid lock in the lockfile */
+#define MDB_PIDLOCK			1
+
+#ifdef MDB_USE_POSIX_SEM
+
+typedef sem_t *mdb_mutex_t, *mdb_mutexref_t;
+#define LOCK_MUTEX0(mutex)		mdb_sem_wait(mutex)
+#define UNLOCK_MUTEX(mutex)		sem_post(mutex)
+
+static int
+mdb_sem_wait(sem_t *sem)
+{
+   int rc;
+   while ((rc = sem_wait(sem)) && (rc = errno) == EINTR) ;
+   return rc;
+}
+
+#else	/* MDB_USE_POSIX_MUTEX: */
+	/** Shared mutex/semaphore as the original is stored.
+	 *
+	 *	Not for copies.  Instead it can be assigned to an #mdb_mutexref_t.
+	 *	When mdb_mutexref_t is a pointer and mdb_mutex_t is not, then it
+	 *	is array[size 1] so it can be assigned to the pointer.
+	 */
+typedef pthread_mutex_t mdb_mutex_t[1];
+	/** Reference to an #mdb_mutex_t */
+typedef pthread_mutex_t *mdb_mutexref_t;
+	/** Lock the reader or writer mutex.
+	 *	Returns 0 or a code to give #mdb_mutex_failed(), as in #LOCK_MUTEX().
+	 */
+#define LOCK_MUTEX0(mutex)	pthread_mutex_lock(mutex)
+	/** Unlock the reader or writer mutex.
+	 */
+#define UNLOCK_MUTEX(mutex)	pthread_mutex_unlock(mutex)
+	/** Mark mutex-protected data as repaired, after death of previous owner.
+	 */
+#define mdb_mutex_consistent(mutex)	pthread_mutex_consistent(mutex)
+#endif	/* MDB_USE_POSIX_SEM */
+
+	/** Get the error code for the last failed system function.
+	 */
+#define	ErrCode()	errno
+
+	/** An abstraction for a file handle.
+	 *	On POSIX systems file handles are small integers. On Windows
+	 *	they're opaque pointers.
+	 */
+#define	HANDLE	int
+
+	/**	A value for an invalid file handle.
+	 *	Mainly used to initialize file variables and signify that they are
+	 *	unused.
+	 */
+#define INVALID_HANDLE_VALUE	(-1)
+
+	/** Get the size of a memory page for the system.
+	 *	This is the basic size that the platform's memory manager uses, and is
+	 *	fundamental to the use of memory-mapped files.
+	 */
+#define	GET_PAGESIZE(x)	((x) = sysconf(_SC_PAGE_SIZE))
+#endif
+
+#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
+#define MNAME_LEN	32
+#else
+#define MNAME_LEN	(sizeof(pthread_mutex_t))
+#endif
+
+/** @} */
+
+#ifdef MDB_ROBUST_SUPPORTED
+	/** Lock mutex, handle any error, set rc = result.
+	 *	Return 0 on success, nonzero (not rc) on error.
+	 */
+#define LOCK_MUTEX(rc, env, mutex) \
+	(((rc) = LOCK_MUTEX0(mutex)) && \
+	 ((rc) = mdb_mutex_failed(env, mutex, rc)))
+static int mdb_mutex_failed(MDB_env *env, mdb_mutexref_t mutex, int rc);
+#else
+#define LOCK_MUTEX(rc, env, mutex) ((rc) = LOCK_MUTEX0(mutex))
+#define mdb_mutex_failed(env, mutex, rc) (rc)
+#endif
+
+#ifndef _WIN32
+/**	A flag for opening a file and requesting synchronous data writes.
+ *	This is only used when writing a meta page. It's not strictly needed;
+ *	we could just do a normal write and then immediately perform a flush.
+ *	But if this flag is available it saves us an extra system call.
+ *
+ *	@note If O_DSYNC is undefined but exists in /usr/include,
+ * preferably set some compiler flag to get the definition.
+ */
+#ifndef MDB_DSYNC
+# ifdef O_DSYNC
+# define MDB_DSYNC	O_DSYNC
+# else
+# define MDB_DSYNC	O_SYNC
+# endif
+#endif
+#endif
+
+/** Function for flushing the data of a file. Define this to fsync
+ *	if fdatasync() is not supported.
+ */
+#ifndef MDB_FDATASYNC
+# define MDB_FDATASYNC	fdatasync
+#endif
+
+#ifndef MDB_MSYNC
+# define MDB_MSYNC(addr,len,flags)	msync(addr,len,flags)
+#endif
+
+#ifndef MS_SYNC
+#define	MS_SYNC	1
+#endif
+
+#ifndef MS_ASYNC
+#define	MS_ASYNC	0
+#endif
+
+	/** A page number in the database.
+	 *	Note that 64 bit page numbers are overkill, since pages themselves
+	 *	already represent 12-13 bits of addressable memory, and the OS will
+	 *	always limit applications to a maximum of 63 bits of address space.
+	 *
+	 *	@note In the #MDB_node structure, we only store 48 bits of this value,
+	 *	which thus limits us to only 60 bits of addressable data.
+	 */
+typedef MDB_ID	pgno_t;
+
+	/** A transaction ID.
+	 *	See struct MDB_txn.mt_txnid for details.
+	 */
+typedef MDB_ID	txnid_t;
+
+/** @defgroup debug	Debug Macros
+ *	@{
+ */
+#ifndef MDB_DEBUG
+	/**	Enable debug output.  Needs variable argument macros (a C99 feature).
+	 *	Set this to 1 for copious tracing. Set to 2 to add dumps of all IDLs
+	 *	read from and written to the database (used for free space management).
+	 */
+#define MDB_DEBUG 0
+#endif
+
+#if MDB_DEBUG
+static int mdb_debug;
+static txnid_t mdb_debug_start;
+
+	/**	Print a debug message with printf formatting.
+	 *	Requires double parenthesis around 2 or more args.
+	 */
+# define DPRINTF(args) ((void) ((mdb_debug) && DPRINTF0 args))
+# define DPRINTF0(fmt, ...) \
+	fprintf(stderr, "%s:%d " fmt "\n", mdb_func_, __LINE__, __VA_ARGS__)
+#else
+# define DPRINTF(args)	((void) 0)
+#endif
+	/**	Print a debug string.
+	 *	The string is printed literally, with no format processing.
+	 */
+#define DPUTS(arg)	DPRINTF(("%s", arg))
+	/** Debuging output value of a cursor DBI: Negative in a sub-cursor. */
+#define DDBI(mc) \
+	(((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
+/** @} */
+
+	/**	@brief The maximum size of a database page.
+	 *
+	 *	It is 32k or 64k, since value-PAGEBASE must fit in
+	 *	#MDB_page.%mp_upper.
+	 *
+	 *	LMDB will use database pages < OS pages if needed.
+	 *	That causes more I/O in write transactions: The OS must
+	 *	know (read) the whole page before writing a partial page.
+	 *
+	 *	Note that we don't currently support Huge pages. On Linux,
+	 *	regular data files cannot use Huge pages, and in general
+	 *	Huge pages aren't actually pageable. We rely on the OS
+	 *	demand-pager to read our data and page it out when memory
+	 *	pressure from other processes is high. So until OSs have
+	 *	actual paging support for Huge pages, they're not viable.
+	 */
+#define MAX_PAGESIZE	 (PAGEBASE ? 0x10000 : 0x8000)
+
+	/** The minimum number of keys required in a database page.
+	 *	Setting this to a larger value will place a smaller bound on the
+	 *	maximum size of a data item. Data items larger than this size will
+	 *	be pushed into overflow pages instead of being stored directly in
+	 *	the B-tree node. This value used to default to 4. With a page size
+	 *	of 4096 bytes that meant that any item larger than 1024 bytes would
+	 *	go into an overflow page. That also meant that on average 2-3KB of
+	 *	each overflow page was wasted space. The value cannot be lower than
+	 *	2 because then there would no longer be a tree structure. With this
+	 *	value, items larger than 2KB will go into overflow pages, and on
+	 *	average only 1KB will be wasted.
+	 */
+#define MDB_MINKEYS	 2
+
+	/**	A stamp that identifies a file as an LMDB file.
+	 *	There's nothing special about this value other than that it is easily
+	 *	recognizable, and it will reflect any byte order mismatches.
+	 */
+#define MDB_MAGIC	 0xBEEFC0DE
+
+	/**	The version number for a database's datafile format. */
+#define MDB_DATA_VERSION	 ((MDB_DEVEL) ? 999 : 1)
+	/**	The version number for a database's lockfile format. */
+#define MDB_LOCK_VERSION	 1
+
+	/**	@brief The max size of a key we can write, or 0 for computed max.
+	 *
+	 *	This macro should normally be left alone or set to 0.
+	 *	Note that a database with big keys or dupsort data cannot be
+	 *	reliably modified by a liblmdb which uses a smaller max.
+	 *	The default is 511 for backwards compat, or 0 when #MDB_DEVEL.
+	 *
+	 *	Other values are allowed, for backwards compat.  However:
+	 *	A value bigger than the computed max can break if you do not
+	 *	know what you are doing, and liblmdb <= 0.9.10 can break when
+	 *	modifying a DB with keys/dupsort data bigger than its max.
+	 *
+	 *	Data items in an #MDB_DUPSORT database are also limited to
+	 *	this size, since they're actually keys of a sub-DB.  Keys and
+	 *	#MDB_DUPSORT data items must fit on a node in a regular page.
+	 */
+#ifndef MDB_MAXKEYSIZE
+#define MDB_MAXKEYSIZE	 ((MDB_DEVEL) ? 0 : 511)
+#endif
+
+	/**	The maximum size of a key we can write to the environment. */
+#if MDB_MAXKEYSIZE
+#define ENV_MAXKEY(env)	(MDB_MAXKEYSIZE)
+#else
+#define ENV_MAXKEY(env)	((env)->me_maxkey)
+#endif
+
+	/**	@brief The maximum size of a data item.
+	 *
+	 *	We only store a 32 bit value for node sizes.
+	 */
+#define MAXDATASIZE	0xffffffffUL
+
+#if MDB_DEBUG
+	/**	Key size which fits in a #DKBUF.
+	 *	@ingroup debug
+	 */
+#define DKBUF_MAXKEYSIZE ((MDB_MAXKEYSIZE) > 0 ? (MDB_MAXKEYSIZE) : 511)
+	/**	A key buffer.
+	 *	@ingroup debug
+	 *	This is used for printing a hex dump of a key's contents.
+	 */
+#define DKBUF	char kbuf[DKBUF_MAXKEYSIZE*2+1]
+	/**	Display a key in hex.
+	 *	@ingroup debug
+	 *	Invoke a function to display a key in hex.
+	 */
+#define	DKEY(x)	mdb_dkey(x, kbuf)
+#else
+#define	DKBUF
+#define DKEY(x)	0
+#endif
+
+	/** An invalid page number.
+	 *	Mainly used to denote an empty tree.
+	 */
+#define P_INVALID	 (~(pgno_t)0)
+
+	/** Test if the flags \b f are set in a flag word \b w. */
+#define F_ISSET(w, f)	 (((w) & (f)) == (f))
+
+	/** Round \b n up to an even number. */
+#define EVEN(n)		(((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
+
+	/**	Used for offsets within a single page.
+	 *	Since memory pages are typically 4 or 8KB in size, 12-13 bits,
+	 *	this is plenty.
+	 */
+typedef uint16_t	 indx_t;
+
+	/**	Default size of memory map.
+	 *	This is certainly too small for any actual applications. Apps should always set
+	 *	the size explicitly using #mdb_env_set_mapsize().
+	 */
+#define DEFAULT_MAPSIZE	1048576
+
+/**	@defgroup readers	Reader Lock Table
+ *	Readers don't acquire any locks for their data access. Instead, they
+ *	simply record their transaction ID in the reader table. The reader
+ *	mutex is needed just to find an empty slot in the reader table. The
+ *	slot's address is saved in thread-specific data so that subsequent read
+ *	transactions started by the same thread need no further locking to proceed.
+ *
+ *	If #MDB_NOTLS is set, the slot address is not saved in thread-specific data.
+ *
+ *	No reader table is used if the database is on a read-only filesystem, or
+ *	if #MDB_NOLOCK is set.
+ *
+ *	Since the database uses multi-version concurrency control, readers don't
+ *	actually need any locking. This table is used to keep track of which
+ *	readers are using data from which old transactions, so that we'll know
+ *	when a particular old transaction is no longer in use. Old transactions
+ *	that have discarded any data pages can then have those pages reclaimed
+ *	for use by a later write transaction.
+ *
+ *	The lock table is constructed such that reader slots are aligned with the
+ *	processor's cache line size. Any slot is only ever used by one thread.
+ *	This alignment guarantees that there will be no contention or cache
+ *	thrashing as threads update their own slot info, and also eliminates
+ *	any need for locking when accessing a slot.
+ *
+ *	A writer thread will scan every slot in the table to determine the oldest
+ *	outstanding reader transaction. Any freed pages older than this will be
+ *	reclaimed by the writer. The writer doesn't use any locks when scanning
+ *	this table. This means that there's no guarantee that the writer will
+ *	see the most up-to-date reader info, but that's not required for correct
+ *	operation - all we need is to know the upper bound on the oldest reader,
+ *	we don't care at all about the newest reader. So the only consequence of
+ *	reading stale information here is that old pages might hang around a
+ *	while longer before being reclaimed. That's actually good anyway, because
+ *	the longer we delay reclaiming old pages, the more likely it is that a
+ *	string of contiguous pages can be found after coalescing old pages from
+ *	many old transactions together.
+ *	@{
+ */
+	/**	Number of slots in the reader table.
+	 *	This value was chosen somewhat arbitrarily. 126 readers plus a
+	 *	couple mutexes fit exactly into 8KB on my development machine.
+	 *	Applications should set the table size using #mdb_env_set_maxreaders().
+	 */
+#define DEFAULT_READERS	126
+
+	/**	The size of a CPU cache line in bytes. We want our lock structures
+	 *	aligned to this size to avoid false cache line sharing in the
+	 *	lock table.
+	 *	This value works for most CPUs. For Itanium this should be 128.
+	 */
+#ifndef CACHELINE
+#define CACHELINE	64
+#endif
+
+	/**	The information we store in a single slot of the reader table.
+	 *	In addition to a transaction ID, we also record the process and
+	 *	thread ID that owns a slot, so that we can detect stale information,
+	 *	e.g. threads or processes that went away without cleaning up.
+	 *	@note We currently don't check for stale records. We simply re-init
+	 *	the table when we know that we're the only process opening the
+	 *	lock file.
+	 */
+typedef struct MDB_rxbody {
+	/**	Current Transaction ID when this transaction began, or (txnid_t)-1.
+	 *	Multiple readers that start at the same time will probably have the
+	 *	same ID here. Again, it's not important to exclude them from
+	 *	anything; all we need to know is which version of the DB they
+	 *	started from so we can avoid overwriting any data used in that
+	 *	particular version.
+	 */
+	volatile txnid_t		mrb_txnid;
+	/** The process ID of the process owning this reader txn. */
+	volatile MDB_PID_T	mrb_pid;
+	/** The thread ID of the thread owning this txn. */
+	volatile MDB_THR_T	mrb_tid;
+} MDB_rxbody;
+
+	/** The actual reader record, with cacheline padding. */
+typedef struct MDB_reader {
+	union {
+		MDB_rxbody mrx;
+		/** shorthand for mrb_txnid */
+#define	mr_txnid	mru.mrx.mrb_txnid
+#define	mr_pid	mru.mrx.mrb_pid
+#define	mr_tid	mru.mrx.mrb_tid
+		/** cache line alignment */
+		char pad[(sizeof(MDB_rxbody)+CACHELINE-1) & ~(CACHELINE-1)];
+	} mru;
+} MDB_reader;
+
+	/** The header for the reader table.
+	 *	The table resides in a memory-mapped file. (This is a different file
+	 *	than is used for the main database.)
+	 *
+	 *	For POSIX the actual mutexes reside in the shared memory of this
+	 *	mapped file. On Windows, mutexes are named objects allocated by the
+	 *	kernel; we store the mutex names in this mapped file so that other
+	 *	processes can grab them. This same approach is also used on
+	 *	MacOSX/Darwin (using named semaphores) since MacOSX doesn't support
+	 *	process-shared POSIX mutexes. For these cases where a named object
+	 *	is used, the object name is derived from a 64 bit FNV hash of the
+	 *	environment pathname. As such, naming collisions are extremely
+	 *	unlikely. If a collision occurs, the results are unpredictable.
+	 */
+typedef struct MDB_txbody {
+		/** Stamp identifying this as an LMDB file. It must be set
+		 *	to #MDB_MAGIC. */
+	uint32_t	mtb_magic;
+		/** Format of this lock file. Must be set to #MDB_LOCK_FORMAT. */
+	uint32_t	mtb_format;
+#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
+	char	mtb_rmname[MNAME_LEN];
+#else
+		/** Mutex protecting access to this table.
+		 *	This is the reader table lock used with LOCK_MUTEX().
+		 */
+	mdb_mutex_t	mtb_rmutex;
+#endif
+		/**	The ID of the last transaction committed to the database.
+		 *	This is recorded here only for convenience; the value can always
+		 *	be determined by reading the main database meta pages.
+		 */
+	volatile txnid_t		mtb_txnid;
+		/** The number of slots that have been used in the reader table.
+		 *	This always records the maximum count, it is not decremented
+		 *	when readers release their slots.
+		 */
+	volatile unsigned	mtb_numreaders;
+} MDB_txbody;
+
+	/** The actual reader table definition. */
+typedef struct MDB_txninfo {
+	union {
+		MDB_txbody mtb;
+#define mti_magic	mt1.mtb.mtb_magic
+#define mti_format	mt1.mtb.mtb_format
+#define mti_rmutex	mt1.mtb.mtb_rmutex
+#define mti_rmname	mt1.mtb.mtb_rmname
+#define mti_txnid	mt1.mtb.mtb_txnid
+#define mti_numreaders	mt1.mtb.mtb_numreaders
+		char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
+	} mt1;
+	union {
+#if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
+		char mt2_wmname[MNAME_LEN];
+#define	mti_wmname	mt2.mt2_wmname
+#else
+		mdb_mutex_t	mt2_wmutex;
+#define mti_wmutex	mt2.mt2_wmutex
+#endif
+		char pad[(MNAME_LEN+CACHELINE-1) & ~(CACHELINE-1)];
+	} mt2;
+	MDB_reader	mti_readers[1];
+} MDB_txninfo;
+
+	/** Lockfile format signature: version, features and field layout */
+#define MDB_LOCK_FORMAT \
+	((uint32_t) \
+	 ((MDB_LOCK_VERSION) \
+	  /* Flags which describe functionality */ \
+	  + (((MDB_PIDLOCK) != 0) << 16)))
+/** @} */
+
+/** Common header for all page types. The page type depends on #mp_flags.
+ *
+ * #P_BRANCH and #P_LEAF pages have unsorted '#MDB_node's at the end, with
+ * sorted #mp_ptrs[] entries referring to them. Exception: #P_LEAF2 pages
+ * omit mp_ptrs and pack sorted #MDB_DUPFIXED values after the page header.
+ *
+ * #P_OVERFLOW records occupy one or more contiguous pages where only the
+ * first has a page header. They hold the real data of #F_BIGDATA nodes.
+ *
+ * #P_SUBP sub-pages are small leaf "pages" with duplicate data.
+ * A node with flag #F_DUPDATA but not #F_SUBDATA contains a sub-page.
+ * (Duplicate data can also go in sub-databases, which use normal pages.)
+ *
+ * #P_META pages contain #MDB_meta, the start point of an LMDB snapshot.
+ *
+ * Each non-metapage up to #MDB_meta.%mm_last_pg is reachable exactly once
+ * in the snapshot: Either used by a database or listed in a freeDB record.
+ */
+typedef struct MDB_page {
+#define	mp_pgno	mp_p.p_pgno
+#define	mp_next	mp_p.p_next
+	union {
+		pgno_t		p_pgno;	/**< page number */
+		struct MDB_page *p_next; /**< for in-memory list of freed pages */
+	} mp_p;
+	uint16_t	mp_pad;			/**< key size if this is a LEAF2 page */
+/**	@defgroup mdb_page	Page Flags
+ *	@ingroup internal
+ *	Flags for the page headers.
+ *	@{
+ */
+#define	P_BRANCH	 0x01		/**< branch page */
+#define	P_LEAF		 0x02		/**< leaf page */
+#define	P_OVERFLOW	 0x04		/**< overflow page */
+#define	P_META		 0x08		/**< meta page */
+#define	P_DIRTY		 0x10		/**< dirty page, also set for #P_SUBP pages */
+#define	P_LEAF2		 0x20		/**< for #MDB_DUPFIXED records */
+#define	P_SUBP		 0x40		/**< for #MDB_DUPSORT sub-pages */
+#define	P_LOOSE		 0x4000		/**< page was dirtied then freed, can be reused */
+#define	P_KEEP		 0x8000		/**< leave this page alone during spill */
+/** @} */
+	uint16_t	mp_flags;		/**< @ref mdb_page */
+#define mp_lower	mp_pb.pb.pb_lower
+#define mp_upper	mp_pb.pb.pb_upper
+#define mp_pages	mp_pb.pb_pages
+	union {
+		struct {
+			indx_t		pb_lower;		/**< lower bound of free space */
+			indx_t		pb_upper;		/**< upper bound of free space */
+		} pb;
+		uint32_t	pb_pages;	/**< number of overflow pages */
+	} mp_pb;
+	indx_t		mp_ptrs[1];		/**< dynamic size */
+} MDB_page;
+
+	/** Size of the page header, excluding dynamic data at the end */
+#define PAGEHDRSZ	 ((unsigned) offsetof(MDB_page, mp_ptrs))
+
+	/** Address of first usable data byte in a page, after the header */
+#define METADATA(p)	 ((void *)((char *)(p) + PAGEHDRSZ))
+
+	/** ITS#7713, change PAGEBASE to handle 65536 byte pages */
+#define	PAGEBASE	((MDB_DEVEL) ? PAGEHDRSZ : 0)
+
+	/** Number of nodes on a page */
+#define NUMKEYS(p)	 (((p)->mp_lower - (PAGEHDRSZ-PAGEBASE)) >> 1)
+
+	/** The amount of space remaining in the page */
+#define SIZELEFT(p)	 (indx_t)((p)->mp_upper - (p)->mp_lower)
+
+	/** The percentage of space used in the page, in tenths of a percent. */
+#define PAGEFILL(env, p) (1000L * ((env)->me_psize - PAGEHDRSZ - SIZELEFT(p)) / \
+				((env)->me_psize - PAGEHDRSZ))
+	/** The minimum page fill factor, in tenths of a percent.
+	 *	Pages emptier than this are candidates for merging.
+	 */
+#define FILL_THRESHOLD	 250
+
+	/** Test if a page is a leaf page */
+#define IS_LEAF(p)	 F_ISSET((p)->mp_flags, P_LEAF)
+	/** Test if a page is a LEAF2 page */
+#define IS_LEAF2(p)	 F_ISSET((p)->mp_flags, P_LEAF2)
+	/** Test if a page is a branch page */
+#define IS_BRANCH(p)	 F_ISSET((p)->mp_flags, P_BRANCH)
+	/** Test if a page is an overflow page */
+#define IS_OVERFLOW(p)	 F_ISSET((p)->mp_flags, P_OVERFLOW)
+	/** Test if a page is a sub page */
+#define IS_SUBP(p)	 F_ISSET((p)->mp_flags, P_SUBP)
+
+	/** The number of overflow pages needed to store the given size. */
+#define OVPAGES(size, psize)	((PAGEHDRSZ-1 + (size)) / (psize) + 1)
+
+	/** Link in #MDB_txn.%mt_loose_pgs list.
+	 *  Kept outside the page header, which is needed when reusing the page.
+	 */
+#define NEXT_LOOSE_PAGE(p)		(*(MDB_page **)((p) + 2))
+
+	/** Header for a single key/data pair within a page.
+	 * Used in pages of type #P_BRANCH and #P_LEAF without #P_LEAF2.
+	 * We guarantee 2-byte alignment for 'MDB_node's.
+	 *
+	 * #mn_lo and #mn_hi are used for data size on leaf nodes, and for child
+	 * pgno on branch nodes.  On 64 bit platforms, #mn_flags is also used
+	 * for pgno.  (Branch nodes have no flags).  Lo and hi are in host byte
+	 * order in case some accesses can be optimized to 32-bit word access.
+	 *
+	 * Leaf node flags describe node contents.  #F_BIGDATA says the node's
+	 * data part is the page number of an overflow page with actual data.
+	 * #F_DUPDATA and #F_SUBDATA can be combined giving duplicate data in
+	 * a sub-page/sub-database, and named databases (just #F_SUBDATA).
+	 */
+typedef struct MDB_node {
+	/** part of data size or pgno
+	 *	@{ */
+#if BYTE_ORDER == LITTLE_ENDIAN
+	unsigned short	mn_lo, mn_hi;
+#else
+	unsigned short	mn_hi, mn_lo;
+#endif
+	/** @} */
+/** @defgroup mdb_node Node Flags
+ *	@ingroup internal
+ *	Flags for node headers.
+ *	@{
+ */
+#define F_BIGDATA	 0x01			/**< data put on overflow page */
+#define F_SUBDATA	 0x02			/**< data is a sub-database */
+#define F_DUPDATA	 0x04			/**< data has duplicates */
+
+/** valid flags for #mdb_node_add() */
+#define	NODE_ADD_FLAGS	(F_DUPDATA|F_SUBDATA|MDB_RESERVE|MDB_APPEND)
+
+/** @} */
+	unsigned short	mn_flags;		/**< @ref mdb_node */
+	unsigned short	mn_ksize;		/**< key size */
+	char		mn_data[1];			/**< key and data are appended here */
+} MDB_node;
+
+	/** Size of the node header, excluding dynamic data at the end */
+#define NODESIZE	 offsetof(MDB_node, mn_data)
+
+	/** Bit position of top word in page number, for shifting mn_flags */
+#define PGNO_TOPWORD ((pgno_t)-1 > 0xffffffffu ? 32 : 0)
+
+	/** Size of a node in a branch page with a given key.
+	 *	This is just the node header plus the key, there is no data.
+	 */
+#define INDXSIZE(k)	 (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))
+
+	/** Size of a node in a leaf page with a given key and data.
+	 *	This is node header plus key plus data size.
+	 */
+#define LEAFSIZE(k, d)	 (NODESIZE + (k)->mv_size + (d)->mv_size)
+
+	/** Address of node \b i in page \b p */
+#define NODEPTR(p, i)	 ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i] + PAGEBASE))
+
+	/** Address of the key for the node */
+#define NODEKEY(node)	 (void *)((node)->mn_data)
+
+	/** Address of the data for a node */
+#define NODEDATA(node)	 (void *)((char *)(node)->mn_data + (node)->mn_ksize)
+
+	/** Get the page number pointed to by a branch node */
+#define NODEPGNO(node) \
+	((node)->mn_lo | ((pgno_t) (node)->mn_hi << 16) | \
+	 (PGNO_TOPWORD ? ((pgno_t) (node)->mn_flags << PGNO_TOPWORD) : 0))
+	/** Set the page number in a branch node */
+#define SETPGNO(node,pgno)	do { \
+	(node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
+	if (PGNO_TOPWORD) (node)->mn_flags = (pgno) >> PGNO_TOPWORD; } while(0)
+
+	/** Get the size of the data in a leaf node */
+#define NODEDSZ(node)	 ((node)->mn_lo | ((unsigned)(node)->mn_hi << 16))
+	/** Set the size of the data for a leaf node */
+#define SETDSZ(node,size)	do { \
+	(node)->mn_lo = (size) & 0xffff; (node)->mn_hi = (size) >> 16;} while(0)
+	/** The size of a key in a node */
+#define NODEKSZ(node)	 ((node)->mn_ksize)
+
+	/** Copy a page number from src to dst */
+#ifdef MISALIGNED_OK
+#define COPY_PGNO(dst,src)	dst = src
+#else
+#if SIZE_MAX > 4294967295UL
+#define COPY_PGNO(dst,src)	do { \
+	unsigned short *s, *d;	\
+	s = (unsigned short *)&(src);	\
+	d = (unsigned short *)&(dst);	\
+	*d++ = *s++;	\
+	*d++ = *s++;	\
+	*d++ = *s++;	\
+	*d = *s;	\
+} while (0)
+#else
+#define COPY_PGNO(dst,src)	do { \
+	unsigned short *s, *d;	\
+	s = (unsigned short *)&(src);	\
+	d = (unsigned short *)&(dst);	\
+	*d++ = *s++;	\
+	*d = *s;	\
+} while (0)
+#endif
+#endif
+	/** The address of a key in a LEAF2 page.
+	 *	LEAF2 pages are used for #MDB_DUPFIXED sorted-duplicate sub-DBs.
+	 *	There are no node headers, keys are stored contiguously.
+	 */
+#define LEAF2KEY(p, i, ks)	((char *)(p) + PAGEHDRSZ + ((i)*(ks)))
+
+	/** Set the \b node's key into \b keyptr, if requested. */
+#define MDB_GET_KEY(node, keyptr)	{ if ((keyptr) != NULL) { \
+	(keyptr)->mv_size = NODEKSZ(node); (keyptr)->mv_data = NODEKEY(node); } }
+
+	/** Set the \b node's key into \b key. */
+#define MDB_GET_KEY2(node, key)	{ key.mv_size = NODEKSZ(node); key.mv_data = NODEKEY(node); }
+
+	/** Information about a single database in the environment. */
+typedef struct MDB_db {
+	uint32_t	md_pad;		/**< also ksize for LEAF2 pages */
+	uint16_t	md_flags;	/**< @ref mdb_dbi_open */
+	uint16_t	md_depth;	/**< depth of this tree */
+	pgno_t		md_branch_pages;	/**< number of internal pages */
+	pgno_t		md_leaf_pages;		/**< number of leaf pages */
+	pgno_t		md_overflow_pages;	/**< number of overflow pages */
+	size_t		md_entries;		/**< number of data items */
+	pgno_t		md_root;		/**< the root page of this tree */
+} MDB_db;
+
+#define MDB_VALID	0x8000		/**< DB handle is valid, for me_dbflags */
+#define PERSISTENT_FLAGS	(0xffff & ~(MDB_VALID))
+	/** #mdb_dbi_open() flags */
+#define VALID_FLAGS	(MDB_REVERSEKEY|MDB_DUPSORT|MDB_INTEGERKEY|MDB_DUPFIXED|\
+	MDB_INTEGERDUP|MDB_REVERSEDUP|MDB_CREATE)
+
+	/** Handle for the DB used to track free pages. */
+#define	FREE_DBI	0
+	/** Handle for the default DB. */
+#define	MAIN_DBI	1
+	/** Number of DBs in metapage (free and main) - also hardcoded elsewhere */
+#define CORE_DBS	2
+
+	/** Number of meta pages - also hardcoded elsewhere */
+#define NUM_METAS	2
+
+	/** Meta page content.
+	 *	A meta page is the start point for accessing a database snapshot.
+	 *	Pages 0-1 are meta pages. Transaction N writes meta page #(N % 2).
+	 */
+typedef struct MDB_meta {
+		/** Stamp identifying this as an LMDB file. It must be set
+		 *	to #MDB_MAGIC. */
+	uint32_t	mm_magic;
+		/** Version number of this file. Must be set to #MDB_DATA_VERSION. */
+	uint32_t	mm_version;
+	void		*mm_address;		/**< address for fixed mapping */
+	size_t		mm_mapsize;			/**< size of mmap region */
+	MDB_db		mm_dbs[CORE_DBS];	/**< first is free space, 2nd is main db */
+	/** The size of pages used in this DB */
+#define	mm_psize	mm_dbs[FREE_DBI].md_pad
+	/** Any persistent environment flags. @ref mdb_env */
+#define	mm_flags	mm_dbs[FREE_DBI].md_flags
+	/** Last used page in the datafile.
+	 *	Actually the file may be shorter if the freeDB lists the final pages.
+	 */
+	pgno_t		mm_last_pg;
+	volatile txnid_t	mm_txnid;	/**< txnid that committed this page */
+} MDB_meta;
+
+	/** Buffer for a stack-allocated meta page.
+	 *	The members define size and alignment, and silence type
+	 *	aliasing warnings.  They are not used directly; that could
+	 *	mean incorrectly using several union members in parallel.
+	 */
+typedef union MDB_metabuf {
+	MDB_page	mb_page;
+	struct {
+		char		mm_pad[PAGEHDRSZ];
+		MDB_meta	mm_meta;
+	} mb_metabuf;
+} MDB_metabuf;
+
+	/** Auxiliary DB info.
+	 *	The information here is mostly static/read-only. There is
+	 *	only a single copy of this record in the environment.
+	 */
+typedef struct MDB_dbx {
+	MDB_val		md_name;		/**< name of the database */
+	MDB_cmp_func	*md_cmp;	/**< function for comparing keys */
+	MDB_cmp_func	*md_dcmp;	/**< function for comparing data items */
+	MDB_rel_func	*md_rel;	/**< user relocate function */
+	void		*md_relctx;		/**< user-provided context for md_rel */
+} MDB_dbx;
+
+	/** A database transaction.
+	 *	Every operation requires a transaction handle.
+	 */
+struct MDB_txn {
+	MDB_txn		*mt_parent;		/**< parent of a nested txn */
+	/** Nested txn under this txn, set together with flag #MDB_TXN_HAS_CHILD */
+	MDB_txn		*mt_child;
+	pgno_t		mt_next_pgno;	/**< next unallocated page */
+	/** The ID of this transaction. IDs are integers incrementing from 1.
+	 *	Only committed write transactions increment the ID. If a transaction
+	 *	aborts, the ID may be re-used by the next writer.
+	 */
+	txnid_t		mt_txnid;
+	MDB_env		*mt_env;		/**< the DB environment */
+	/** The list of pages that became unused during this transaction.
+	 */
+	MDB_IDL		mt_free_pgs;
+	/** The list of loose pages that became unused and may be reused
+	 *	in this transaction, linked through #NEXT_LOOSE_PAGE(page).
+	 */
+	MDB_page	*mt_loose_pgs;
+	/** Number of loose pages (#mt_loose_pgs) */
+	int			mt_loose_count;
+	/** The sorted list of dirty pages we temporarily wrote to disk
+	 *	because the dirty list was full. page numbers in here are
+	 *	shifted left by 1, deleted slots have the LSB set.
+	 */
+	MDB_IDL		mt_spill_pgs;
+	union {
+		/** For write txns: Modified pages. Sorted when not MDB_WRITEMAP. */
+		MDB_ID2L	dirty_list;
+		/** For read txns: This thread/txn's reader table slot, or NULL. */
+		MDB_reader	*reader;
+	} mt_u;
+	/** Array of records for each DB known in the environment. */
+	MDB_dbx		*mt_dbxs;
+	/** Array of MDB_db records for each known DB */
+	MDB_db		*mt_dbs;
+	/** Array of sequence numbers for each DB handle */
+	unsigned int	*mt_dbiseqs;
+/** @defgroup mt_dbflag	Transaction DB Flags
+ *	@ingroup internal
+ * @{
+ */
+#define DB_DIRTY	0x01		/**< DB was written in this txn */
+#define DB_STALE	0x02		/**< Named-DB record is older than txnID */
+#define DB_NEW		0x04		/**< Named-DB handle opened in this txn */
+#define DB_VALID	0x08		/**< DB handle is valid, see also #MDB_VALID */
+#define DB_USRVALID	0x10		/**< As #DB_VALID, but not set for #FREE_DBI */
+#define DB_DUPDATA	0x20		/**< DB is #MDB_DUPSORT data */
+/** @} */
+	/** In write txns, array of cursors for each DB */
+	MDB_cursor	**mt_cursors;
+	/** Array of flags for each DB */
+	unsigned char	*mt_dbflags;
+	/**	Number of DB records in use, or 0 when the txn is finished.
+	 *	This number only ever increments until the txn finishes; we
+	 *	don't decrement it when individual DB handles are closed.
+	 */
+	MDB_dbi		mt_numdbs;
+
+/** @defgroup mdb_txn	Transaction Flags
+ *	@ingroup internal
+ *	@{
+ */
+	/** #mdb_txn_begin() flags */
+#define MDB_TXN_BEGIN_FLAGS	MDB_RDONLY
+#define MDB_TXN_RDONLY		MDB_RDONLY	/**< read-only transaction */
+	/* internal txn flags */
+#define MDB_TXN_WRITEMAP	MDB_WRITEMAP	/**< copy of #MDB_env flag in writers */
+#define MDB_TXN_FINISHED	0x01		/**< txn is finished or never began */
+#define MDB_TXN_ERROR		0x02		/**< txn is unusable after an error */
+#define MDB_TXN_DIRTY		0x04		/**< must write, even if dirty list is empty */
+#define MDB_TXN_SPILLS		0x08		/**< txn or a parent has spilled pages */
+#define MDB_TXN_HAS_CHILD	0x10		/**< txn has an #MDB_txn.%mt_child */
+	/** most operations on the txn are currently illegal */
+#define MDB_TXN_BLOCKED		(MDB_TXN_FINISHED|MDB_TXN_ERROR|MDB_TXN_HAS_CHILD)
+/** @} */
+	unsigned int	mt_flags;		/**< @ref mdb_txn */
+	/** #dirty_list room: Array size - \#dirty pages visible to this txn.
+	 *	Includes ancestor txns' dirty pages not hidden by other txns'
+	 *	dirty/spilled pages. Thus commit(nested txn) has room to merge
+	 *	dirty_list into mt_parent after freeing hidden mt_parent pages.
+	 */
+	unsigned int	mt_dirty_room;
+};
+
+/** Enough space for 2^32 nodes with minimum of 2 keys per node. I.e., plenty.
+ * At 4 keys per node, enough for 2^64 nodes, so there's probably no need to
+ * raise this on a 64 bit machine.
+ */
+#define CURSOR_STACK		 32
+
+struct MDB_xcursor;
+
+	/** Cursors are used for all DB operations.
+	 *	A cursor holds a path of (page pointer, key index) from the DB
+	 *	root to a position in the DB, plus other state. #MDB_DUPSORT
+	 *	cursors include an xcursor to the current data item. Write txns
+	 *	track their cursors and keep them up to date when data moves.
+	 *	Exception: An xcursor's pointer to a #P_SUBP page can be stale.
+	 *	(A node with #F_DUPDATA but no #F_SUBDATA contains a subpage).
+	 */
+struct MDB_cursor {
+	/** Next cursor on this DB in this txn */
+	MDB_cursor	*mc_next;
+	/** Backup of the original cursor if this cursor is a shadow */
+	MDB_cursor	*mc_backup;
+	/** Context used for databases with #MDB_DUPSORT, otherwise NULL */
+	struct MDB_xcursor	*mc_xcursor;
+	/** The transaction that owns this cursor */
+	MDB_txn		*mc_txn;
+	/** The database handle this cursor operates on */
+	MDB_dbi		mc_dbi;
+	/** The database record for this cursor */
+	MDB_db		*mc_db;
+	/** The database auxiliary record for this cursor */
+	MDB_dbx		*mc_dbx;
+	/** The @ref mt_dbflag for this database */
+	unsigned char	*mc_dbflag;
+	unsigned short 	mc_snum;	/**< number of pushed pages */
+	unsigned short	mc_top;		/**< index of top page, normally mc_snum-1 */
+/** @defgroup mdb_cursor	Cursor Flags
+ *	@ingroup internal
+ *	Cursor state flags.
+ *	@{
+ */
+#define C_INITIALIZED	0x01	/**< cursor has been initialized and is valid */
+#define C_EOF	0x02			/**< No more data */
+#define C_SUB	0x04			/**< Cursor is a sub-cursor */
+#define C_DEL	0x08			/**< last op was a cursor_del */
+#define C_UNTRACK	0x40		/**< Un-track cursor when closing */
+/** @} */
+	unsigned int	mc_flags;	/**< @ref mdb_cursor */
+	MDB_page	*mc_pg[CURSOR_STACK];	/**< stack of pushed pages */
+	indx_t		mc_ki[CURSOR_STACK];	/**< stack of page indices */
+};
+
+	/** Context for sorted-dup records.
+	 *	We could have gone to a fully recursive design, with arbitrarily
+	 *	deep nesting of sub-databases. But for now we only handle these
+	 *	levels - main DB, optional sub-DB, sorted-duplicate DB.
+	 */
+typedef struct MDB_xcursor {
+	/** A sub-cursor for traversing the Dup DB */
+	MDB_cursor mx_cursor;
+	/** The database record for this Dup DB */
+	MDB_db	mx_db;
+	/**	The auxiliary DB record for this Dup DB */
+	MDB_dbx	mx_dbx;
+	/** The @ref mt_dbflag for this Dup DB */
+	unsigned char mx_dbflag;
+} MDB_xcursor;
+
+	/** Check if there is an inited xcursor */
+#define XCURSOR_INITED(mc) \
+	((mc)->mc_xcursor && ((mc)->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED))
+
+	/** Update the xcursor's sub-page pointer, if any, in \b mc.  Needed
+	 *	when the node which contains the sub-page may have moved.  Called
+	 *	with leaf page \b mp = mc->mc_pg[\b top].
+	 */
+#define XCURSOR_REFRESH(mc, top, mp) do { \
+	MDB_page *xr_pg = (mp); \
+	MDB_node *xr_node; \
+	if (!XCURSOR_INITED(mc) || (mc)->mc_ki[top] >= NUMKEYS(xr_pg)) break; \
+	xr_node = NODEPTR(xr_pg, (mc)->mc_ki[top]); \
+	if ((xr_node->mn_flags & (F_DUPDATA|F_SUBDATA)) == F_DUPDATA) \
+		(mc)->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(xr_node); \
+} while (0)
+
+	/** State of FreeDB old pages, stored in the MDB_env */
+typedef struct MDB_pgstate {
+	pgno_t		*mf_pghead;	/**< Reclaimed freeDB pages, or NULL before use */
+	txnid_t		mf_pglast;	/**< ID of last used record, or 0 if !mf_pghead */
+} MDB_pgstate;
+
+	/** The database environment. */
+struct MDB_env {
+	HANDLE		me_fd;		/**< The main data file */
+	HANDLE		me_lfd;		/**< The lock file */
+	HANDLE		me_mfd;		/**< For writing and syncing the meta pages */
+	/** Failed to update the meta page. Probably an I/O error. */
+#define	MDB_FATAL_ERROR	0x80000000U
+	/** Some fields are initialized. */
+#define	MDB_ENV_ACTIVE	0x20000000U
+	/** me_txkey is set */
+#define	MDB_ENV_TXKEY	0x10000000U
+	/** fdatasync is unreliable */
+#define	MDB_FSYNCONLY	0x08000000U
+	uint32_t 	me_flags;		/**< @ref mdb_env */
+	unsigned int	me_psize;	/**< DB page size, inited from me_os_psize */
+	unsigned int	me_os_psize;	/**< OS page size, from #GET_PAGESIZE */
+	unsigned int	me_maxreaders;	/**< size of the reader table */
+	/** Max #MDB_txninfo.%mti_numreaders of interest to #mdb_env_close() */
+	volatile int	me_close_readers;
+	MDB_dbi		me_numdbs;		/**< number of DBs opened */
+	MDB_dbi		me_maxdbs;		/**< size of the DB table */
+	MDB_PID_T	me_pid;		/**< process ID of this env */
+	char		*me_path;		/**< path to the DB files */
+	char		*me_map;		/**< the memory map of the data file */
+	MDB_txninfo	*me_txns;		/**< the memory map of the lock file or NULL */
+	MDB_meta	*me_metas[NUM_METAS];	/**< pointers to the two meta pages */
+	void		*me_pbuf;		/**< scratch area for DUPSORT put() */
+	MDB_txn		*me_txn;		/**< current write transaction */
+	MDB_txn		*me_txn0;		/**< prealloc'd write transaction */
+	size_t		me_mapsize;		/**< size of the data memory map */
+	off_t		me_size;		/**< current file size */
+	pgno_t		me_maxpg;		/**< me_mapsize / me_psize */
+	MDB_dbx		*me_dbxs;		/**< array of static DB info */
+	uint16_t	*me_dbflags;	/**< array of flags from MDB_db.md_flags */
+	unsigned int	*me_dbiseqs;	/**< array of dbi sequence numbers */
+	pthread_key_t	me_txkey;	/**< thread-key for readers */
+	txnid_t		me_pgoldest;	/**< ID of oldest reader last time we looked */
+	MDB_pgstate	me_pgstate;		/**< state of old pages from freeDB */
+#	define		me_pglast	me_pgstate.mf_pglast
+#	define		me_pghead	me_pgstate.mf_pghead
+	MDB_page	*me_dpages;		/**< list of malloc'd blocks for re-use */
+	/** IDL of pages that became unused in a write txn */
+	MDB_IDL		me_free_pgs;
+	/** ID2L of pages written during a write txn. Length MDB_IDL_UM_SIZE. */
+	MDB_ID2L	me_dirty_list;
+	/** Max number of freelist items that can fit in a single overflow page */
+	int			me_maxfree_1pg;
+	/** Max size of a node on a page */
+	unsigned int	me_nodemax;
+#if !(MDB_MAXKEYSIZE)
+	unsigned int	me_maxkey;	/**< max size of a key */
+#endif
+	int		me_live_reader;		/**< have liveness lock in reader table */
+#ifdef _WIN32
+	int		me_pidquery;		/**< Used in OpenProcess */
+#endif
+#ifdef MDB_USE_POSIX_MUTEX	/* Posix mutexes reside in shared mem */
+#	define		me_rmutex	me_txns->mti_rmutex /**< Shared reader lock */
+#	define		me_wmutex	me_txns->mti_wmutex /**< Shared writer lock */
+#else
+	mdb_mutex_t	me_rmutex;
+	mdb_mutex_t	me_wmutex;
+#endif
+	void		*me_userctx;	 /**< User-settable context */
+	MDB_assert_func *me_assert_func; /**< Callback for assertion failures */
+};
+
+	/** Nested transaction */
+typedef struct MDB_ntxn {
+	MDB_txn		mnt_txn;		/**< the transaction */
+	MDB_pgstate	mnt_pgstate;	/**< parent transaction's saved freestate */
+} MDB_ntxn;
+
+	/** max number of pages to commit in one writev() call */
+#define MDB_COMMIT_PAGES	 64
+#if defined(IOV_MAX) && IOV_MAX < MDB_COMMIT_PAGES
+#undef MDB_COMMIT_PAGES
+#define MDB_COMMIT_PAGES	IOV_MAX
+#endif
+
+	/** max bytes to write in one call */
+#define MAX_WRITE		(0x40000000U >> (sizeof(ssize_t) == 4))
+
+	/** Check \b txn and \b dbi arguments to a function */
+#define TXN_DBI_EXIST(txn, dbi, validity) \
+	((txn) && (dbi)<(txn)->mt_numdbs && ((txn)->mt_dbflags[dbi] & (validity)))
+
+	/** Check for misused \b dbi handles */
+#define TXN_DBI_CHANGED(txn, dbi) \
+	((txn)->mt_dbiseqs[dbi] != (txn)->mt_env->me_dbiseqs[dbi])
+
+static int  mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp);
+static int  mdb_page_new(MDB_cursor *mc, uint32_t flags, int num, MDB_page **mp);
+static int  mdb_page_touch(MDB_cursor *mc);
+
+#define MDB_END_NAMES {"committed", "empty-commit", "abort", "reset", \
+	"reset-tmp", "fail-begin", "fail-beginchild"}
+enum {
+	/* mdb_txn_end operation number, for logging */
+	MDB_END_COMMITTED, MDB_END_EMPTY_COMMIT, MDB_END_ABORT, MDB_END_RESET,
+	MDB_END_RESET_TMP, MDB_END_FAIL_BEGIN, MDB_END_FAIL_BEGINCHILD
+};
+#define MDB_END_OPMASK	0x0F	/**< mask for #mdb_txn_end() operation number */
+#define MDB_END_UPDATE	0x10	/**< update env state (DBIs) */
+#define MDB_END_FREE	0x20	/**< free txn unless it is #MDB_env.%me_txn0 */
+#define MDB_END_SLOT MDB_NOTLS	/**< release any reader slot if #MDB_NOTLS */
+static void mdb_txn_end(MDB_txn *txn, unsigned mode);
+
+static int  mdb_page_get(MDB_cursor *mc, pgno_t pgno, MDB_page **mp, int *lvl);
+static int  mdb_page_search_root(MDB_cursor *mc,
+			    MDB_val *key, int modify);
+#define MDB_PS_MODIFY	1
+#define MDB_PS_ROOTONLY	2
+#define MDB_PS_FIRST	4
+#define MDB_PS_LAST		8
+static int  mdb_page_search(MDB_cursor *mc,
+			    MDB_val *key, int flags);
+static int	mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst);
+
+#define MDB_SPLIT_REPLACE	MDB_APPENDDUP	/**< newkey is not new */
+static int	mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata,
+				pgno_t newpgno, unsigned int nflags);
+
+static int  mdb_env_read_header(MDB_env *env, MDB_meta *meta);
+static MDB_meta *mdb_env_pick_meta(const MDB_env *env);
+static int  mdb_env_write_meta(MDB_txn *txn);
+#ifdef MDB_USE_POSIX_MUTEX /* Drop unused excl arg */
+# define mdb_env_close0(env, excl) mdb_env_close1(env)
+#endif
+static void mdb_env_close0(MDB_env *env, int excl);
+
+static MDB_node *mdb_node_search(MDB_cursor *mc, MDB_val *key, int *exactp);
+static int  mdb_node_add(MDB_cursor *mc, indx_t indx,
+			    MDB_val *key, MDB_val *data, pgno_t pgno, unsigned int flags);
+static void mdb_node_del(MDB_cursor *mc, int ksize);
+static void mdb_node_shrink(MDB_page *mp, indx_t indx);
+static int	mdb_node_move(MDB_cursor *csrc, MDB_cursor *cdst, int fromleft);
+static int  mdb_node_read(MDB_cursor *mc, MDB_node *leaf, MDB_val *data);
+static size_t	mdb_leaf_size(MDB_env *env, MDB_val *key, MDB_val *data);
+static size_t	mdb_branch_size(MDB_env *env, MDB_val *key);
+
+static int	mdb_rebalance(MDB_cursor *mc);
+static int	mdb_update_key(MDB_cursor *mc, MDB_val *key);
+
+static void	mdb_cursor_pop(MDB_cursor *mc);
+static int	mdb_cursor_push(MDB_cursor *mc, MDB_page *mp);
+
+static int	mdb_cursor_del0(MDB_cursor *mc);
+static int	mdb_del0(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, unsigned flags);
+static int	mdb_cursor_sibling(MDB_cursor *mc, int move_right);
+static int	mdb_cursor_next(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op);
+static int	mdb_cursor_prev(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op);
+static int	mdb_cursor_set(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op,
+				int *exactp);
+static int	mdb_cursor_first(MDB_cursor *mc, MDB_val *key, MDB_val *data);
+static int	mdb_cursor_last(MDB_cursor *mc, MDB_val *key, MDB_val *data);
+
+static void	mdb_cursor_init(MDB_cursor *mc, MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx);
+static void	mdb_xcursor_init0(MDB_cursor *mc);
+static void	mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node);
+static void	mdb_xcursor_init2(MDB_cursor *mc, MDB_xcursor *src_mx, int force);
+
+static int	mdb_drop0(MDB_cursor *mc, int subs);
+static void mdb_default_cmp(MDB_txn *txn, MDB_dbi dbi);
+static int mdb_reader_check0(MDB_env *env, int rlocked, int *dead);
+
+/** @cond */
+static MDB_cmp_func	mdb_cmp_memn, mdb_cmp_memnr, mdb_cmp_int, mdb_cmp_cint, mdb_cmp_long;
+/** @endcond */
+
+/** Compare two items pointing at size_t's of unknown alignment. */
+#ifdef MISALIGNED_OK
+# define mdb_cmp_clong mdb_cmp_long
+#else
+# define mdb_cmp_clong mdb_cmp_cint
+#endif
+
+#ifdef _WIN32
+static SECURITY_DESCRIPTOR mdb_null_sd;
+static SECURITY_ATTRIBUTES mdb_all_sa;
+static int mdb_sec_inited;
+
+struct MDB_name;
+static int utf8_to_utf16(const char *src, struct MDB_name *dst, int xtra);
+#endif
+
+/** Return the library version info. */
+char * ESECT
+mdb_version(int *major, int *minor, int *patch)
+{
+	if (major) *major = MDB_VERSION_MAJOR;
+	if (minor) *minor = MDB_VERSION_MINOR;
+	if (patch) *patch = MDB_VERSION_PATCH;
+	return MDB_VERSION_STRING;
+}
+
+/** Table of descriptions for LMDB @ref errors */
+static char *const mdb_errstr[] = {
+	"MDB_KEYEXIST: Key/data pair already exists",
+	"MDB_NOTFOUND: No matching key/data pair found",
+	"MDB_PAGE_NOTFOUND: Requested page not found",
+	"MDB_CORRUPTED: Located page was wrong type",
+	"MDB_PANIC: Update of meta page failed or environment had fatal error",
+	"MDB_VERSION_MISMATCH: Database environment version mismatch",
+	"MDB_INVALID: File is not an LMDB file",
+	"MDB_MAP_FULL: Environment mapsize limit reached",
+	"MDB_DBS_FULL: Environment maxdbs limit reached",
+	"MDB_READERS_FULL: Environment maxreaders limit reached",
+	"MDB_TLS_FULL: Thread-local storage keys full - too many environments open",
+	"MDB_TXN_FULL: Transaction has too many dirty pages - transaction too big",
+	"MDB_CURSOR_FULL: Internal error - cursor stack limit reached",
+	"MDB_PAGE_FULL: Internal error - page has no more space",
+	"MDB_MAP_RESIZED: Database contents grew beyond environment mapsize",
+	"MDB_INCOMPATIBLE: Operation and DB incompatible, or DB flags changed",
+	"MDB_BAD_RSLOT: Invalid reuse of reader locktable slot",
+	"MDB_BAD_TXN: Transaction must abort, has a child, or is invalid",
+	"MDB_BAD_VALSIZE: Unsupported size of key/DB name/data, or wrong DUPFIXED size",
+	"MDB_BAD_DBI: The specified DBI handle was closed/changed unexpectedly",
+};
+
+char *
+mdb_strerror(int err)
+{
+#ifdef _WIN32
+	/** HACK: pad 4KB on stack over the buf. Return system msgs in buf.
+	 *	This works as long as no function between the call to mdb_strerror
+	 *	and the actual use of the message uses more than 4K of stack.
+	 */
+#define MSGSIZE	1024
+#define PADSIZE	4096
+	char buf[MSGSIZE+PADSIZE], *ptr = buf;
+#endif
+	int i;
+	if (!err)
+		return ("Successful return: 0");
+
+	if (err >= MDB_KEYEXIST && err <= MDB_LAST_ERRCODE) {
+		i = err - MDB_KEYEXIST;
+		return mdb_errstr[i];
+	}
+
+#ifdef _WIN32
+	/* These are the C-runtime error codes we use. The comment indicates
+	 * their numeric value, and the Win32 error they would correspond to
+	 * if the error actually came from a Win32 API. A major mess, we should
+	 * have used LMDB-specific error codes for everything.
+	 */
+	switch(err) {
+	case ENOENT:	/* 2, FILE_NOT_FOUND */
+	case EIO:		/* 5, ACCESS_DENIED */
+	case ENOMEM:	/* 12, INVALID_ACCESS */
+	case EACCES:	/* 13, INVALID_DATA */
+	case EBUSY:		/* 16, CURRENT_DIRECTORY */
+	case EINVAL:	/* 22, BAD_COMMAND */
+	case ENOSPC:	/* 28, OUT_OF_PAPER */
+		return strerror(err);
+	default:
+		;
+	}
+	buf[0] = 0;
+	FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM |
+		FORMAT_MESSAGE_IGNORE_INSERTS,
+		NULL, err, 0, ptr, MSGSIZE, (va_list *)buf+MSGSIZE);
+	return ptr;
+#else
+	return strerror(err);
+#endif
+}
+
+/** assert(3) variant in cursor context */
+#define mdb_cassert(mc, expr)	mdb_assert0((mc)->mc_txn->mt_env, expr, #expr)
+/** assert(3) variant in transaction context */
+#define mdb_tassert(txn, expr)	mdb_assert0((txn)->mt_env, expr, #expr)
+/** assert(3) variant in environment context */
+#define mdb_eassert(env, expr)	mdb_assert0(env, expr, #expr)
+
+#ifndef NDEBUG
+# define mdb_assert0(env, expr, expr_txt) ((expr) ? (void)0 : \
+		mdb_assert_fail(env, expr_txt, mdb_func_, __FILE__, __LINE__))
+
+static void ESECT
+mdb_assert_fail(MDB_env *env, const char *expr_txt,
+	const char *func, const char *file, int line)
+{
+	char buf[400];
+	sprintf(buf, "%.100s:%d: Assertion '%.200s' failed in %.40s()",
+		file, line, expr_txt, func);
+	if (env->me_assert_func)
+		env->me_assert_func(env, buf);
+	fprintf(stderr, "%s\n", buf);
+	abort();
+}
+#else
+# define mdb_assert0(env, expr, expr_txt) ((void) 0)
+#endif /* NDEBUG */
+
+#if MDB_DEBUG
+/** Return the page number of \b mp which may be sub-page, for debug output */
+static pgno_t
+mdb_dbg_pgno(MDB_page *mp)
+{
+	pgno_t ret;
+	COPY_PGNO(ret, mp->mp_pgno);
+	return ret;
+}
+
+/** Display a key in hexadecimal and return the address of the result.
+ * @param[in] key the key to display
+ * @param[in] buf the buffer to write into. Should always be #DKBUF.
+ * @return The key in hexadecimal form.
+ */
+char *
+mdb_dkey(MDB_val *key, char *buf)
+{
+	char *ptr = buf;
+	unsigned char *c = key->mv_data;
+	unsigned int i;
+
+	if (!key)
+		return "";
+
+	if (key->mv_size > DKBUF_MAXKEYSIZE)
+		return "MDB_MAXKEYSIZE";
+	/* may want to make this a dynamic check: if the key is mostly
+	 * printable characters, print it as-is instead of converting to hex.
+	 */
+#if 1
+	buf[0] = '\0';
+	for (i=0; i<key->mv_size; i++)
+		ptr += sprintf(ptr, "%02x", *c++);
+#else
+	sprintf(buf, "%.*s", key->mv_size, key->mv_data);
+#endif
+	return buf;
+}
+
+static const char *
+mdb_leafnode_type(MDB_node *n)
+{
+	static char *const tp[2][2] = {{"", ": DB"}, {": sub-page", ": sub-DB"}};
+	return F_ISSET(n->mn_flags, F_BIGDATA) ? ": overflow page" :
+		tp[F_ISSET(n->mn_flags, F_DUPDATA)][F_ISSET(n->mn_flags, F_SUBDATA)];
+}
+
+/** Display all the keys in the page. */
+void
+mdb_page_list(MDB_page *mp)
+{
+	pgno_t pgno = mdb_dbg_pgno(mp);
+	const char *type, *state = (mp->mp_flags & P_DIRTY) ? ", dirty" : "";
+	MDB_node *node;
+	unsigned int i, nkeys, nsize, total = 0;
+	MDB_val key;
+	DKBUF;
+
+	switch (mp->mp_flags & (P_BRANCH|P_LEAF|P_LEAF2|P_META|P_OVERFLOW|P_SUBP)) {
+	case P_BRANCH:              type = "Branch page";		break;
+	case P_LEAF:                type = "Leaf page";			break;
+	case P_LEAF|P_SUBP:         type = "Sub-page";			break;
+	case P_LEAF|P_LEAF2:        type = "LEAF2 page";		break;
+	case P_LEAF|P_LEAF2|P_SUBP: type = "LEAF2 sub-page";	break;
+	case P_OVERFLOW:
+		fprintf(stderr, "Overflow page %"Z"u pages %u%s\n",
+			pgno, mp->mp_pages, state);
+		return;
+	case P_META:
+		fprintf(stderr, "Meta-page %"Z"u txnid %"Z"u\n",
+			pgno, ((MDB_meta *)METADATA(mp))->mm_txnid);
+		return;
+	default:
+		fprintf(stderr, "Bad page %"Z"u flags 0x%X\n", pgno, mp->mp_flags);
+		return;
+	}
+
+	nkeys = NUMKEYS(mp);
+	fprintf(stderr, "%s %"Z"u numkeys %d%s\n", type, pgno, nkeys, state);
+
+	for (i=0; i<nkeys; i++) {
+		if (IS_LEAF2(mp)) {	/* LEAF2 pages have no mp_ptrs[] or node headers */
+			key.mv_size = nsize = mp->mp_pad;
+			key.mv_data = LEAF2KEY(mp, i, nsize);
+			total += nsize;
+			fprintf(stderr, "key %d: nsize %d, %s\n", i, nsize, DKEY(&key));
+			continue;
+		}
+		node = NODEPTR(mp, i);
+		key.mv_size = node->mn_ksize;
+		key.mv_data = node->mn_data;
+		nsize = NODESIZE + key.mv_size;
+		if (IS_BRANCH(mp)) {
+			fprintf(stderr, "key %d: page %"Z"u, %s\n", i, NODEPGNO(node),
+				DKEY(&key));
+			total += nsize;
+		} else {
+			if (F_ISSET(node->mn_flags, F_BIGDATA))
+				nsize += sizeof(pgno_t);
+			else
+				nsize += NODEDSZ(node);
+			total += nsize;
+			nsize += sizeof(indx_t);
+			fprintf(stderr, "key %d: nsize %d, %s%s\n",
+				i, nsize, DKEY(&key), mdb_leafnode_type(node));
+		}
+		total = EVEN(total);
+	}
+	fprintf(stderr, "Total: header %d + contents %d + unused %d\n",
+		IS_LEAF2(mp) ? PAGEHDRSZ : PAGEBASE + mp->mp_lower, total, SIZELEFT(mp));
+}
+
+void
+mdb_cursor_chk(MDB_cursor *mc)
+{
+	unsigned int i;
+	MDB_node *node;
+	MDB_page *mp;
+
+	if (!mc->mc_snum || !(mc->mc_flags & C_INITIALIZED)) return;
+	for (i=0; i<mc->mc_top; i++) {
+		mp = mc->mc_pg[i];
+		node = NODEPTR(mp, mc->mc_ki[i]);
+		if (NODEPGNO(node) != mc->mc_pg[i+1]->mp_pgno)
+			printf("oops!\n");
+	}
+	if (mc->mc_ki[i] >= NUMKEYS(mc->mc_pg[i]))
+		printf("ack!\n");
+	if (XCURSOR_INITED(mc)) {
+		node = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+		if (((node->mn_flags & (F_DUPDATA|F_SUBDATA)) == F_DUPDATA) &&
+			mc->mc_xcursor->mx_cursor.mc_pg[0] != NODEDATA(node)) {
+			printf("blah!\n");
+		}
+	}
+}
+#endif
+
+#if (MDB_DEBUG) > 2
+/** Count all the pages in each DB and in the freelist
+ *  and make sure it matches the actual number of pages
+ *  being used.
+ *  All named DBs must be open for a correct count.
+ */
+static void mdb_audit(MDB_txn *txn)
+{
+	MDB_cursor mc;
+	MDB_val key, data;
+	MDB_ID freecount, count;
+	MDB_dbi i;
+	int rc;
+
+	freecount = 0;
+	mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
+	while ((rc = mdb_cursor_get(&mc, &key, &data, MDB_NEXT)) == 0)
+		freecount += *(MDB_ID *)data.mv_data;
+	mdb_tassert(txn, rc == MDB_NOTFOUND);
+
+	count = 0;
+	for (i = 0; i<txn->mt_numdbs; i++) {
+		MDB_xcursor mx;
+		if (!(txn->mt_dbflags[i] & DB_VALID))
+			continue;
+		mdb_cursor_init(&mc, txn, i, &mx);
+		if (txn->mt_dbs[i].md_root == P_INVALID)
+			continue;
+		count += txn->mt_dbs[i].md_branch_pages +
+			txn->mt_dbs[i].md_leaf_pages +
+			txn->mt_dbs[i].md_overflow_pages;
+		if (txn->mt_dbs[i].md_flags & MDB_DUPSORT) {
+			rc = mdb_page_search(&mc, NULL, MDB_PS_FIRST);
+			for (; rc == MDB_SUCCESS; rc = mdb_cursor_sibling(&mc, 1)) {
+				unsigned j;
+				MDB_page *mp;
+				mp = mc.mc_pg[mc.mc_top];
+				for (j=0; j<NUMKEYS(mp); j++) {
+					MDB_node *leaf = NODEPTR(mp, j);
+					if (leaf->mn_flags & F_SUBDATA) {
+						MDB_db db;
+						memcpy(&db, NODEDATA(leaf), sizeof(db));
+						count += db.md_branch_pages + db.md_leaf_pages +
+							db.md_overflow_pages;
+					}
+				}
+			}
+			mdb_tassert(txn, rc == MDB_NOTFOUND);
+		}
+	}
+	if (freecount + count + NUM_METAS != txn->mt_next_pgno) {
+		fprintf(stderr, "audit: %"Z"u freecount: %"Z"u count: %"Z"u total: %"Z"u next_pgno: %"Z"u\n",
+			txn->mt_txnid, freecount, count+NUM_METAS,
+			freecount+count+NUM_METAS, txn->mt_next_pgno);
+	}
+}
+#endif
+
+int
+mdb_cmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b)
+{
+	return txn->mt_dbxs[dbi].md_cmp(a, b);
+}
+
+int
+mdb_dcmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b)
+{
+	MDB_cmp_func *dcmp = txn->mt_dbxs[dbi].md_dcmp;
+#if UINT_MAX < SIZE_MAX
+	if (dcmp == mdb_cmp_int && a->mv_size == sizeof(size_t))
+		dcmp = mdb_cmp_clong;
+#endif
+	return dcmp(a, b);
+}
+
+/** Allocate memory for a page.
+ * Re-use old malloc'd pages first for singletons, otherwise just malloc.
+ * Set #MDB_TXN_ERROR on failure.
+ */
+static MDB_page *
+mdb_page_malloc(MDB_txn *txn, unsigned num)
+{
+	MDB_env *env = txn->mt_env;
+	MDB_page *ret = env->me_dpages;
+	size_t psize = env->me_psize, sz = psize, off;
+	/* For ! #MDB_NOMEMINIT, psize counts how much to init.
+	 * For a single page alloc, we init everything after the page header.
+	 * For multi-page, we init the final page; if the caller needed that
+	 * many pages they will be filling in at least up to the last page.
+	 */
+	if (num == 1) {
+		if (ret) {
+			VGMEMP_ALLOC(env, ret, sz);
+			VGMEMP_DEFINED(ret, sizeof(ret->mp_next));
+			env->me_dpages = ret->mp_next;
+			return ret;
+		}
+		psize -= off = PAGEHDRSZ;
+	} else {
+		sz *= num;
+		off = sz - psize;
+	}
+	if ((ret = malloc(sz)) != NULL) {
+		VGMEMP_ALLOC(env, ret, sz);
+		if (!(env->me_flags & MDB_NOMEMINIT)) {
+			memset((char *)ret + off, 0, psize);
+			ret->mp_pad = 0;
+		}
+	} else {
+		txn->mt_flags |= MDB_TXN_ERROR;
+	}
+	return ret;
+}
+/** Free a single page.
+ * Saves single pages to a list, for future reuse.
+ * (This is not used for multi-page overflow pages.)
+ */
+static void
+mdb_page_free(MDB_env *env, MDB_page *mp)
+{
+	mp->mp_next = env->me_dpages;
+	VGMEMP_FREE(env, mp);
+	env->me_dpages = mp;
+}
+
+/** Free a dirty page */
+static void
+mdb_dpage_free(MDB_env *env, MDB_page *dp)
+{
+	if (!IS_OVERFLOW(dp) || dp->mp_pages == 1) {
+		mdb_page_free(env, dp);
+	} else {
+		/* large pages just get freed directly */
+		VGMEMP_FREE(env, dp);
+		free(dp);
+	}
+}
+
+/**	Return all dirty pages to dpage list */
+static void
+mdb_dlist_free(MDB_txn *txn)
+{
+	MDB_env *env = txn->mt_env;
+	MDB_ID2L dl = txn->mt_u.dirty_list;
+	unsigned i, n = dl[0].mid;
+
+	for (i = 1; i <= n; i++) {
+		mdb_dpage_free(env, dl[i].mptr);
+	}
+	dl[0].mid = 0;
+}
+
+/** Loosen or free a single page.
+ * Saves single pages to a list for future reuse
+ * in this same txn. It has been pulled from the freeDB
+ * and already resides on the dirty list, but has been
+ * deleted. Use these pages first before pulling again
+ * from the freeDB.
+ *
+ * If the page wasn't dirtied in this txn, just add it
+ * to this txn's free list.
+ */
+static int
+mdb_page_loose(MDB_cursor *mc, MDB_page *mp)
+{
+	int loose = 0;
+	pgno_t pgno = mp->mp_pgno;
+	MDB_txn *txn = mc->mc_txn;
+
+	if ((mp->mp_flags & P_DIRTY) && mc->mc_dbi != FREE_DBI) {
+		if (txn->mt_parent) {
+			MDB_ID2 *dl = txn->mt_u.dirty_list;
+			/* If txn has a parent, make sure the page is in our
+			 * dirty list.
+			 */
+			if (dl[0].mid) {
+				unsigned x = mdb_mid2l_search(dl, pgno);
+				if (x <= dl[0].mid && dl[x].mid == pgno) {
+					if (mp != dl[x].mptr) { /* bad cursor? */
+						mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
+						txn->mt_flags |= MDB_TXN_ERROR;
+						return MDB_CORRUPTED;
+					}
+					/* ok, it's ours */
+					loose = 1;
+				}
+			}
+		} else {
+			/* no parent txn, so it's just ours */
+			loose = 1;
+		}
+	}
+	if (loose) {
+		DPRINTF(("loosen db %d page %"Z"u", DDBI(mc),
+			mp->mp_pgno));
+		NEXT_LOOSE_PAGE(mp) = txn->mt_loose_pgs;
+		txn->mt_loose_pgs = mp;
+		txn->mt_loose_count++;
+		mp->mp_flags |= P_LOOSE;
+	} else {
+		int rc = mdb_midl_append(&txn->mt_free_pgs, pgno);
+		if (rc)
+			return rc;
+	}
+
+	return MDB_SUCCESS;
+}
+
+/** Set or clear P_KEEP in dirty, non-overflow, non-sub pages watched by txn.
+ * @param[in] mc A cursor handle for the current operation.
+ * @param[in] pflags Flags of the pages to update:
+ * P_DIRTY to set P_KEEP, P_DIRTY|P_KEEP to clear it.
+ * @param[in] all No shortcuts. Needed except after a full #mdb_page_flush().
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_pages_xkeep(MDB_cursor *mc, unsigned pflags, int all)
+{
+	enum { Mask = P_SUBP|P_DIRTY|P_LOOSE|P_KEEP };
+	MDB_txn *txn = mc->mc_txn;
+	MDB_cursor *m3, *m0 = mc;
+	MDB_xcursor *mx;
+	MDB_page *dp, *mp;
+	MDB_node *leaf;
+	unsigned i, j;
+	int rc = MDB_SUCCESS, level;
+
+	/* Mark pages seen by cursors */
+	if (mc->mc_flags & C_UNTRACK)
+		mc = NULL;				/* will find mc in mt_cursors */
+	for (i = txn->mt_numdbs;; mc = txn->mt_cursors[--i]) {
+		for (; mc; mc=mc->mc_next) {
+			if (!(mc->mc_flags & C_INITIALIZED))
+				continue;
+			for (m3 = mc;; m3 = &mx->mx_cursor) {
+				mp = NULL;
+				for (j=0; j<m3->mc_snum; j++) {
+					mp = m3->mc_pg[j];
+					if ((mp->mp_flags & Mask) == pflags)
+						mp->mp_flags ^= P_KEEP;
+				}
+				mx = m3->mc_xcursor;
+				/* Proceed to mx if it is at a sub-database */
+				if (! (mx && (mx->mx_cursor.mc_flags & C_INITIALIZED)))
+					break;
+				if (! (mp && (mp->mp_flags & P_LEAF)))
+					break;
+				leaf = NODEPTR(mp, m3->mc_ki[j-1]);
+				if (!(leaf->mn_flags & F_SUBDATA))
+					break;
+			}
+		}
+		if (i == 0)
+			break;
+	}
+
+	if (all) {
+		/* Mark dirty root pages */
+		for (i=0; i<txn->mt_numdbs; i++) {
+			if (txn->mt_dbflags[i] & DB_DIRTY) {
+				pgno_t pgno = txn->mt_dbs[i].md_root;
+				if (pgno == P_INVALID)
+					continue;
+				if ((rc = mdb_page_get(m0, pgno, &dp, &level)) != MDB_SUCCESS)
+					break;
+				if ((dp->mp_flags & Mask) == pflags && level <= 1)
+					dp->mp_flags ^= P_KEEP;
+			}
+		}
+	}
+
+	return rc;
+}
+
+static int mdb_page_flush(MDB_txn *txn, int keep);
+
+/**	Spill pages from the dirty list back to disk.
+ * This is intended to prevent running into #MDB_TXN_FULL situations,
+ * but note that they may still occur in a few cases:
+ *	1) our estimate of the txn size could be too small. Currently this
+ *	 seems unlikely, except with a large number of #MDB_MULTIPLE items.
+ *	2) child txns may run out of space if their parents dirtied a
+ *	 lot of pages and never spilled them. TODO: we probably should do
+ *	 a preemptive spill during #mdb_txn_begin() of a child txn, if
+ *	 the parent's dirty_room is below a given threshold.
+ *
+ * Otherwise, if not using nested txns, it is expected that apps will
+ * not run into #MDB_TXN_FULL any more. The pages are flushed to disk
+ * the same way as for a txn commit, e.g. their P_DIRTY flag is cleared.
+ * If the txn never references them again, they can be left alone.
+ * If the txn only reads them, they can be used without any fuss.
+ * If the txn writes them again, they can be dirtied immediately without
+ * going thru all of the work of #mdb_page_touch(). Such references are
+ * handled by #mdb_page_unspill().
+ *
+ * Also note, we never spill DB root pages, nor pages of active cursors,
+ * because we'll need these back again soon anyway. And in nested txns,
+ * we can't spill a page in a child txn if it was already spilled in a
+ * parent txn. That would alter the parent txns' data even though
+ * the child hasn't committed yet, and we'd have no way to undo it if
+ * the child aborted.
+ *
+ * @param[in] m0 cursor A cursor handle identifying the transaction and
+ *	database for which we are checking space.
+ * @param[in] key For a put operation, the key being stored.
+ * @param[in] data For a put operation, the data being stored.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
+{
+	MDB_txn *txn = m0->mc_txn;
+	MDB_page *dp;
+	MDB_ID2L dl = txn->mt_u.dirty_list;
+	unsigned int i, j, need;
+	int rc;
+
+	if (m0->mc_flags & C_SUB)
+		return MDB_SUCCESS;
+
+	/* Estimate how much space this op will take */
+	i = m0->mc_db->md_depth;
+	/* Named DBs also dirty the main DB */
+	if (m0->mc_dbi >= CORE_DBS)
+		i += txn->mt_dbs[MAIN_DBI].md_depth;
+	/* For puts, roughly factor in the key+data size */
+	if (key)
+		i += (LEAFSIZE(key, data) + txn->mt_env->me_psize) / txn->mt_env->me_psize;
+	i += i;	/* double it for good measure */
+	need = i;
+
+	if (txn->mt_dirty_room > i)
+		return MDB_SUCCESS;
+
+	if (!txn->mt_spill_pgs) {
+		txn->mt_spill_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX);
+		if (!txn->mt_spill_pgs)
+			return ENOMEM;
+	} else {
+		/* purge deleted slots */
+		MDB_IDL sl = txn->mt_spill_pgs;
+		unsigned int num = sl[0];
+		j=0;
+		for (i=1; i<=num; i++) {
+			if (!(sl[i] & 1))
+				sl[++j] = sl[i];
+		}
+		sl[0] = j;
+	}
+
+	/* Preserve pages which may soon be dirtied again */
+	if ((rc = mdb_pages_xkeep(m0, P_DIRTY, 1)) != MDB_SUCCESS)
+		goto done;
+
+	/* Less aggressive spill - we originally spilled the entire dirty list,
+	 * with a few exceptions for cursor pages and DB root pages. But this
+	 * turns out to be a lot of wasted effort because in a large txn many
+	 * of those pages will need to be used again. So now we spill only 1/8th
+	 * of the dirty pages. Testing revealed this to be a good tradeoff,
+	 * better than 1/2, 1/4, or 1/10.
+	 */
+	if (need < MDB_IDL_UM_MAX / 8)
+		need = MDB_IDL_UM_MAX / 8;
+
+	/* Save the page IDs of all the pages we're flushing */
+	/* flush from the tail forward, this saves a lot of shifting later on. */
+	for (i=dl[0].mid; i && need; i--) {
+		MDB_ID pn = dl[i].mid << 1;
+		dp = dl[i].mptr;
+		if (dp->mp_flags & (P_LOOSE|P_KEEP))
+			continue;
+		/* Can't spill twice, make sure it's not already in a parent's
+		 * spill list.
+		 */
+		if (txn->mt_parent) {
+			MDB_txn *tx2;
+			for (tx2 = txn->mt_parent; tx2; tx2 = tx2->mt_parent) {
+				if (tx2->mt_spill_pgs) {
+					j = mdb_midl_search(tx2->mt_spill_pgs, pn);
+					if (j <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[j] == pn) {
+						dp->mp_flags |= P_KEEP;
+						break;
+					}
+				}
+			}
+			if (tx2)
+				continue;
+		}
+		if ((rc = mdb_midl_append(&txn->mt_spill_pgs, pn)))
+			goto done;
+		need--;
+	}
+	mdb_midl_sort(txn->mt_spill_pgs);
+
+	/* Flush the spilled part of dirty list */
+	if ((rc = mdb_page_flush(txn, i)) != MDB_SUCCESS)
+		goto done;
+
+	/* Reset any dirty pages we kept that page_flush didn't see */
+	rc = mdb_pages_xkeep(m0, P_DIRTY|P_KEEP, i);
+
+done:
+	txn->mt_flags |= rc ? MDB_TXN_ERROR : MDB_TXN_SPILLS;
+	return rc;
+}
+
+/** Find oldest txnid still referenced. Expects txn->mt_txnid > 0. */
+static txnid_t
+mdb_find_oldest(MDB_txn *txn)
+{
+	int i;
+	txnid_t mr, oldest = txn->mt_txnid - 1;
+	if (txn->mt_env->me_txns) {
+		MDB_reader *r = txn->mt_env->me_txns->mti_readers;
+		for (i = txn->mt_env->me_txns->mti_numreaders; --i >= 0; ) {
+			if (r[i].mr_pid) {
+				mr = r[i].mr_txnid;
+				if (oldest > mr)
+					oldest = mr;
+			}
+		}
+	}
+	return oldest;
+}
+
+/** Add a page to the txn's dirty list */
+static void
+mdb_page_dirty(MDB_txn *txn, MDB_page *mp)
+{
+	MDB_ID2 mid;
+	int rc, (*insert)(MDB_ID2L, MDB_ID2 *);
+
+	if (txn->mt_flags & MDB_TXN_WRITEMAP) {
+		insert = mdb_mid2l_append;
+	} else {
+		insert = mdb_mid2l_insert;
+	}
+	mid.mid = mp->mp_pgno;
+	mid.mptr = mp;
+	rc = insert(txn->mt_u.dirty_list, &mid);
+	mdb_tassert(txn, rc == 0);
+	txn->mt_dirty_room--;
+}
+
+/** Allocate page numbers and memory for writing.  Maintain me_pglast,
+ * me_pghead and mt_next_pgno.  Set #MDB_TXN_ERROR on failure.
+ *
+ * If there are free pages available from older transactions, they
+ * are re-used first. Otherwise allocate a new page at mt_next_pgno.
+ * Do not modify the freedB, just merge freeDB records into me_pghead[]
+ * and move me_pglast to say which records were consumed.  Only this
+ * function can create me_pghead and move me_pglast/mt_next_pgno.
+ * @param[in] mc cursor A cursor handle identifying the transaction and
+ *	database for which we are allocating.
+ * @param[in] num the number of pages to allocate.
+ * @param[out] mp Address of the allocated page(s). Requests for multiple pages
+ *  will always be satisfied by a single contiguous chunk of memory.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
+{
+#ifdef MDB_PARANOID	/* Seems like we can ignore this now */
+	/* Get at most <Max_retries> more freeDB records once me_pghead
+	 * has enough pages.  If not enough, use new pages from the map.
+	 * If <Paranoid> and mc is updating the freeDB, only get new
+	 * records if me_pghead is empty. Then the freelist cannot play
+	 * catch-up with itself by growing while trying to save it.
+	 */
+	enum { Paranoid = 1, Max_retries = 500 };
+#else
+	enum { Paranoid = 0, Max_retries = INT_MAX /*infinite*/ };
+#endif
+	int rc, retry = num * 60;
+	MDB_txn *txn = mc->mc_txn;
+	MDB_env *env = txn->mt_env;
+	pgno_t pgno, *mop = env->me_pghead;
+	unsigned i, j, mop_len = mop ? mop[0] : 0, n2 = num-1;
+	MDB_page *np;
+	txnid_t oldest = 0, last;
+	MDB_cursor_op op;
+	MDB_cursor m2;
+	int found_old = 0;
+
+	/* If there are any loose pages, just use them */
+	if (num == 1 && txn->mt_loose_pgs) {
+		np = txn->mt_loose_pgs;
+		txn->mt_loose_pgs = NEXT_LOOSE_PAGE(np);
+		txn->mt_loose_count--;
+		DPRINTF(("db %d use loose page %"Z"u", DDBI(mc),
+				np->mp_pgno));
+		*mp = np;
+		return MDB_SUCCESS;
+	}
+
+	*mp = NULL;
+
+	/* If our dirty list is already full, we can't do anything */
+	if (txn->mt_dirty_room == 0) {
+		rc = MDB_TXN_FULL;
+		goto fail;
+	}
+
+	for (op = MDB_FIRST;; op = MDB_NEXT) {
+		MDB_val key, data;
+		MDB_node *leaf;
+		pgno_t *idl;
+
+		/* Seek a big enough contiguous page range. Prefer
+		 * pages at the tail, just truncating the list.
+		 */
+		if (mop_len > n2) {
+			i = mop_len;
+			do {
+				pgno = mop[i];
+				if (mop[i-n2] == pgno+n2)
+					goto search_done;
+			} while (--i > n2);
+			if (--retry < 0)
+				break;
+		}
+
+		if (op == MDB_FIRST) {	/* 1st iteration */
+			/* Prepare to fetch more and coalesce */
+			last = env->me_pglast;
+			oldest = env->me_pgoldest;
+			mdb_cursor_init(&m2, txn, FREE_DBI, NULL);
+			if (last) {
+				op = MDB_SET_RANGE;
+				key.mv_data = &last; /* will look up last+1 */
+				key.mv_size = sizeof(last);
+			}
+			if (Paranoid && mc->mc_dbi == FREE_DBI)
+				retry = -1;
+		}
+		if (Paranoid && retry < 0 && mop_len)
+			break;
+
+		last++;
+		/* Do not fetch more if the record will be too recent */
+		if (oldest <= last) {
+			if (!found_old) {
+				oldest = mdb_find_oldest(txn);
+				env->me_pgoldest = oldest;
+				found_old = 1;
+			}
+			if (oldest <= last)
+				break;
+		}
+		rc = mdb_cursor_get(&m2, &key, NULL, op);
+		if (rc) {
+			if (rc == MDB_NOTFOUND)
+				break;
+			goto fail;
+		}
+		last = *(txnid_t*)key.mv_data;
+		if (oldest <= last) {
+			if (!found_old) {
+				oldest = mdb_find_oldest(txn);
+				env->me_pgoldest = oldest;
+				found_old = 1;
+			}
+			if (oldest <= last)
+				break;
+		}
+		np = m2.mc_pg[m2.mc_top];
+		leaf = NODEPTR(np, m2.mc_ki[m2.mc_top]);
+		if ((rc = mdb_node_read(&m2, leaf, &data)) != MDB_SUCCESS)
+			goto fail;
+
+		idl = (MDB_ID *) data.mv_data;
+		i = idl[0];
+		if (!mop) {
+			if (!(env->me_pghead = mop = mdb_midl_alloc(i))) {
+				rc = ENOMEM;
+				goto fail;
+			}
+		} else {
+			if ((rc = mdb_midl_need(&env->me_pghead, i)) != 0)
+				goto fail;
+			mop = env->me_pghead;
+		}
+		env->me_pglast = last;
+#if (MDB_DEBUG) > 1
+		DPRINTF(("IDL read txn %"Z"u root %"Z"u num %u",
+			last, txn->mt_dbs[FREE_DBI].md_root, i));
+		for (j = i; j; j--)
+			DPRINTF(("IDL %"Z"u", idl[j]));
+#endif
+		/* Merge in descending sorted order */
+		mdb_midl_xmerge(mop, idl);
+		mop_len = mop[0];
+	}
+
+	/* Use new pages from the map when nothing suitable in the freeDB */
+	i = 0;
+	pgno = txn->mt_next_pgno;
+	if (pgno + num >= env->me_maxpg) {
+			DPUTS("DB size maxed out");
+			rc = MDB_MAP_FULL;
+			goto fail;
+	}
+
+search_done:
+	if (env->me_flags & MDB_WRITEMAP) {
+		np = (MDB_page *)(env->me_map + env->me_psize * pgno);
+	} else {
+		if (!(np = mdb_page_malloc(txn, num))) {
+			rc = ENOMEM;
+			goto fail;
+		}
+	}
+	if (i) {
+		mop[0] = mop_len -= num;
+		/* Move any stragglers down */
+		for (j = i-num; j < mop_len; )
+			mop[++j] = mop[++i];
+	} else {
+		txn->mt_next_pgno = pgno + num;
+	}
+	np->mp_pgno = pgno;
+	mdb_page_dirty(txn, np);
+	*mp = np;
+
+	return MDB_SUCCESS;
+
+fail:
+	txn->mt_flags |= MDB_TXN_ERROR;
+	return rc;
+}
+
+/** Copy the used portions of a non-overflow page.
+ * @param[in] dst page to copy into
+ * @param[in] src page to copy from
+ * @param[in] psize size of a page
+ */
+static void
+mdb_page_copy(MDB_page *dst, MDB_page *src, unsigned int psize)
+{
+	enum { Align = sizeof(pgno_t) };
+	indx_t upper = src->mp_upper, lower = src->mp_lower, unused = upper-lower;
+
+	/* If page isn't full, just copy the used portion. Adjust
+	 * alignment so memcpy may copy words instead of bytes.
+	 */
+	if ((unused &= -Align) && !IS_LEAF2(src)) {
+		upper = (upper + PAGEBASE) & -Align;
+		memcpy(dst, src, (lower + PAGEBASE + (Align-1)) & -Align);
+		memcpy((pgno_t *)((char *)dst+upper), (pgno_t *)((char *)src+upper),
+			psize - upper);
+	} else {
+		memcpy(dst, src, psize - unused);
+	}
+}
+
+/** Pull a page off the txn's spill list, if present.
+ * If a page being referenced was spilled to disk in this txn, bring
+ * it back and make it dirty/writable again.
+ * @param[in] txn the transaction handle.
+ * @param[in] mp the page being referenced. It must not be dirty.
+ * @param[out] ret the writable page, if any. ret is unchanged if
+ * mp wasn't spilled.
+ */
+static int
+mdb_page_unspill(MDB_txn *txn, MDB_page *mp, MDB_page **ret)
+{
+	MDB_env *env = txn->mt_env;
+	const MDB_txn *tx2;
+	unsigned x;
+	pgno_t pgno = mp->mp_pgno, pn = pgno << 1;
+
+	for (tx2 = txn; tx2; tx2=tx2->mt_parent) {
+		if (!tx2->mt_spill_pgs)
+			continue;
+		x = mdb_midl_search(tx2->mt_spill_pgs, pn);
+		if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pn) {
+			MDB_page *np;
+			int num;
+			if (txn->mt_dirty_room == 0)
+				return MDB_TXN_FULL;
+			if (IS_OVERFLOW(mp))
+				num = mp->mp_pages;
+			else
+				num = 1;
+			if (env->me_flags & MDB_WRITEMAP) {
+				np = mp;
+			} else {
+				np = mdb_page_malloc(txn, num);
+				if (!np)
+					return ENOMEM;
+				if (num > 1)
+					memcpy(np, mp, num * env->me_psize);
+				else
+					mdb_page_copy(np, mp, env->me_psize);
+			}
+			if (tx2 == txn) {
+				/* If in current txn, this page is no longer spilled.
+				 * If it happens to be the last page, truncate the spill list.
+				 * Otherwise mark it as deleted by setting the LSB.
+				 */
+				if (x == txn->mt_spill_pgs[0])
+					txn->mt_spill_pgs[0]--;
+				else
+					txn->mt_spill_pgs[x] |= 1;
+			}	/* otherwise, if belonging to a parent txn, the
+				 * page remains spilled until child commits
+				 */
+
+			mdb_page_dirty(txn, np);
+			np->mp_flags |= P_DIRTY;
+			*ret = np;
+			break;
+		}
+	}
+	return MDB_SUCCESS;
+}
+
+/** Touch a page: make it dirty and re-insert into tree with updated pgno.
+ * Set #MDB_TXN_ERROR on failure.
+ * @param[in] mc cursor pointing to the page to be touched
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_touch(MDB_cursor *mc)
+{
+	MDB_page *mp = mc->mc_pg[mc->mc_top], *np;
+	MDB_txn *txn = mc->mc_txn;
+	MDB_cursor *m2, *m3;
+	pgno_t	pgno;
+	int rc;
+
+	if (!F_ISSET(mp->mp_flags, P_DIRTY)) {
+		if (txn->mt_flags & MDB_TXN_SPILLS) {
+			np = NULL;
+			rc = mdb_page_unspill(txn, mp, &np);
+			if (rc)
+				goto fail;
+			if (np)
+				goto done;
+		}
+		if ((rc = mdb_midl_need(&txn->mt_free_pgs, 1)) ||
+			(rc = mdb_page_alloc(mc, 1, &np)))
+			goto fail;
+		pgno = np->mp_pgno;
+		DPRINTF(("touched db %d page %"Z"u -> %"Z"u", DDBI(mc),
+			mp->mp_pgno, pgno));
+		mdb_cassert(mc, mp->mp_pgno != pgno);
+		mdb_midl_xappend(txn->mt_free_pgs, mp->mp_pgno);
+		/* Update the parent page, if any, to point to the new page */
+		if (mc->mc_top) {
+			MDB_page *parent = mc->mc_pg[mc->mc_top-1];
+			MDB_node *node = NODEPTR(parent, mc->mc_ki[mc->mc_top-1]);
+			SETPGNO(node, pgno);
+		} else {
+			mc->mc_db->md_root = pgno;
+		}
+	} else if (txn->mt_parent && !IS_SUBP(mp)) {
+		MDB_ID2 mid, *dl = txn->mt_u.dirty_list;
+		pgno = mp->mp_pgno;
+		/* If txn has a parent, make sure the page is in our
+		 * dirty list.
+		 */
+		if (dl[0].mid) {
+			unsigned x = mdb_mid2l_search(dl, pgno);
+			if (x <= dl[0].mid && dl[x].mid == pgno) {
+				if (mp != dl[x].mptr) { /* bad cursor? */
+					mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
+					txn->mt_flags |= MDB_TXN_ERROR;
+					return MDB_CORRUPTED;
+				}
+				return 0;
+			}
+		}
+		mdb_cassert(mc, dl[0].mid < MDB_IDL_UM_MAX);
+		/* No - copy it */
+		np = mdb_page_malloc(txn, 1);
+		if (!np)
+			return ENOMEM;
+		mid.mid = pgno;
+		mid.mptr = np;
+		rc = mdb_mid2l_insert(dl, &mid);
+		mdb_cassert(mc, rc == 0);
+	} else {
+		return 0;
+	}
+
+	mdb_page_copy(np, mp, txn->mt_env->me_psize);
+	np->mp_pgno = pgno;
+	np->mp_flags |= P_DIRTY;
+
+done:
+	/* Adjust cursors pointing to mp */
+	mc->mc_pg[mc->mc_top] = np;
+	m2 = txn->mt_cursors[mc->mc_dbi];
+	if (mc->mc_flags & C_SUB) {
+		for (; m2; m2=m2->mc_next) {
+			m3 = &m2->mc_xcursor->mx_cursor;
+			if (m3->mc_snum < mc->mc_snum) continue;
+			if (m3->mc_pg[mc->mc_top] == mp)
+				m3->mc_pg[mc->mc_top] = np;
+		}
+	} else {
+		for (; m2; m2=m2->mc_next) {
+			if (m2->mc_snum < mc->mc_snum) continue;
+			if (m2 == mc) continue;
+			if (m2->mc_pg[mc->mc_top] == mp) {
+				m2->mc_pg[mc->mc_top] = np;
+				if (IS_LEAF(np))
+					XCURSOR_REFRESH(m2, mc->mc_top, np);
+			}
+		}
+	}
+	return 0;
+
+fail:
+	txn->mt_flags |= MDB_TXN_ERROR;
+	return rc;
+}
+
+int
+mdb_env_sync(MDB_env *env, int force)
+{
+	int rc = 0;
+	if (env->me_flags & MDB_RDONLY)
+		return EACCES;
+	if (force || !F_ISSET(env->me_flags, MDB_NOSYNC)) {
+		if (env->me_flags & MDB_WRITEMAP) {
+			int flags = ((env->me_flags & MDB_MAPASYNC) && !force)
+				? MS_ASYNC : MS_SYNC;
+			if (MDB_MSYNC(env->me_map, env->me_mapsize, flags))
+				rc = ErrCode();
+#ifdef _WIN32
+			else if (flags == MS_SYNC && MDB_FDATASYNC(env->me_fd))
+				rc = ErrCode();
+#endif
+		} else {
+#ifdef BROKEN_FDATASYNC
+			if (env->me_flags & MDB_FSYNCONLY) {
+				if (fsync(env->me_fd))
+					rc = ErrCode();
+			} else
+#endif
+			if (MDB_FDATASYNC(env->me_fd))
+				rc = ErrCode();
+		}
+	}
+	return rc;
+}
+
+/** Back up parent txn's cursors, then grab the originals for tracking */
+static int
+mdb_cursor_shadow(MDB_txn *src, MDB_txn *dst)
+{
+	MDB_cursor *mc, *bk;
+	MDB_xcursor *mx;
+	size_t size;
+	int i;
+
+	for (i = src->mt_numdbs; --i >= 0; ) {
+		if ((mc = src->mt_cursors[i]) != NULL) {
+			size = sizeof(MDB_cursor);
+			if (mc->mc_xcursor)
+				size += sizeof(MDB_xcursor);
+			for (; mc; mc = bk->mc_next) {
+				bk = malloc(size);
+				if (!bk)
+					return ENOMEM;
+				*bk = *mc;
+				mc->mc_backup = bk;
+				mc->mc_db = &dst->mt_dbs[i];
+				/* Kill pointers into src to reduce abuse: The
+				 * user may not use mc until dst ends. But we need a valid
+				 * txn pointer here for cursor fixups to keep working.
+				 */
+				mc->mc_txn    = dst;
+				mc->mc_dbflag = &dst->mt_dbflags[i];
+				if ((mx = mc->mc_xcursor) != NULL) {
+					*(MDB_xcursor *)(bk+1) = *mx;
+					mx->mx_cursor.mc_txn = dst;
+				}
+				mc->mc_next = dst->mt_cursors[i];
+				dst->mt_cursors[i] = mc;
+			}
+		}
+	}
+	return MDB_SUCCESS;
+}
+
+/** Close this write txn's cursors, give parent txn's cursors back to parent.
+ * @param[in] txn the transaction handle.
+ * @param[in] merge true to keep changes to parent cursors, false to revert.
+ * @return 0 on success, non-zero on failure.
+ */
+static void
+mdb_cursors_close(MDB_txn *txn, unsigned merge)
+{
+	MDB_cursor **cursors = txn->mt_cursors, *mc, *next, *bk;
+	MDB_xcursor *mx;
+	int i;
+
+	for (i = txn->mt_numdbs; --i >= 0; ) {
+		for (mc = cursors[i]; mc; mc = next) {
+			next = mc->mc_next;
+			if ((bk = mc->mc_backup) != NULL) {
+				if (merge) {
+					/* Commit changes to parent txn */
+					mc->mc_next = bk->mc_next;
+					mc->mc_backup = bk->mc_backup;
+					mc->mc_txn = bk->mc_txn;
+					mc->mc_db = bk->mc_db;
+					mc->mc_dbflag = bk->mc_dbflag;
+					if ((mx = mc->mc_xcursor) != NULL)
+						mx->mx_cursor.mc_txn = bk->mc_txn;
+				} else {
+					/* Abort nested txn */
+					*mc = *bk;
+					if ((mx = mc->mc_xcursor) != NULL)
+						*mx = *(MDB_xcursor *)(bk+1);
+				}
+				mc = bk;
+			}
+			/* Only malloced cursors are permanently tracked. */
+			free(mc);
+		}
+		cursors[i] = NULL;
+	}
+}
+
+#if !(MDB_PIDLOCK)		/* Currently the same as defined(_WIN32) */
+enum Pidlock_op {
+	Pidset, Pidcheck
+};
+#else
+enum Pidlock_op {
+	Pidset = F_SETLK, Pidcheck = F_GETLK
+};
+#endif
+
+/** Set or check a pid lock. Set returns 0 on success.
+ * Check returns 0 if the process is certainly dead, nonzero if it may
+ * be alive (the lock exists or an error happened so we do not know).
+ *
+ * On Windows Pidset is a no-op, we merely check for the existence
+ * of the process with the given pid. On POSIX we use a single byte
+ * lock on the lockfile, set at an offset equal to the pid.
+ */
+static int
+mdb_reader_pid(MDB_env *env, enum Pidlock_op op, MDB_PID_T pid)
+{
+#if !(MDB_PIDLOCK)		/* Currently the same as defined(_WIN32) */
+	int ret = 0;
+	HANDLE h;
+	if (op == Pidcheck) {
+		h = OpenProcess(env->me_pidquery, FALSE, pid);
+		/* No documented "no such process" code, but other program use this: */
+		if (!h)
+			return ErrCode() != ERROR_INVALID_PARAMETER;
+		/* A process exists until all handles to it close. Has it exited? */
+		ret = WaitForSingleObject(h, 0) != 0;
+		CloseHandle(h);
+	}
+	return ret;
+#else
+	for (;;) {
+		int rc;
+		struct flock lock_info;
+		memset(&lock_info, 0, sizeof(lock_info));
+		lock_info.l_type = F_WRLCK;
+		lock_info.l_whence = SEEK_SET;
+		lock_info.l_start = pid;
+		lock_info.l_len = 1;
+		if ((rc = fcntl(env->me_lfd, op, &lock_info)) == 0) {
+			if (op == F_GETLK && lock_info.l_type != F_UNLCK)
+				rc = -1;
+		} else if ((rc = ErrCode()) == EINTR) {
+			continue;
+		}
+		return rc;
+	}
+#endif
+}
+
+/** Common code for #mdb_txn_begin() and #mdb_txn_renew().
+ * @param[in] txn the transaction handle to initialize
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_txn_renew0(MDB_txn *txn)
+{
+	MDB_env *env = txn->mt_env;
+	MDB_txninfo *ti = env->me_txns;
+	MDB_meta *meta;
+	unsigned int i, nr, flags = txn->mt_flags;
+	uint16_t x;
+	int rc, new_notls = 0;
+
+	if ((flags &= MDB_TXN_RDONLY) != 0) {
+		if (!ti) {
+			meta = mdb_env_pick_meta(env);
+			txn->mt_txnid = meta->mm_txnid;
+			txn->mt_u.reader = NULL;
+		} else {
+			MDB_reader *r = (env->me_flags & MDB_NOTLS) ? txn->mt_u.reader :
+				pthread_getspecific(env->me_txkey);
+			if (r) {
+				if (r->mr_pid != env->me_pid || r->mr_txnid != (txnid_t)-1)
+					return MDB_BAD_RSLOT;
+			} else {
+				MDB_PID_T pid = env->me_pid;
+				MDB_THR_T tid = pthread_self();
+				mdb_mutexref_t rmutex = env->me_rmutex;
+
+				if (!env->me_live_reader) {
+					rc = mdb_reader_pid(env, Pidset, pid);
+					if (rc)
+						return rc;
+					env->me_live_reader = 1;
+				}
+
+				if (LOCK_MUTEX(rc, env, rmutex))
+					return rc;
+				nr = ti->mti_numreaders;
+				for (i=0; i<nr; i++)
+					if (ti->mti_readers[i].mr_pid == 0)
+						break;
+				if (i == env->me_maxreaders) {
+					UNLOCK_MUTEX(rmutex);
+					return MDB_READERS_FULL;
+				}
+				r = &ti->mti_readers[i];
+				/* Claim the reader slot, carefully since other code
+				 * uses the reader table un-mutexed: First reset the
+				 * slot, next publish it in mti_numreaders.  After
+				 * that, it is safe for mdb_env_close() to touch it.
+				 * When it will be closed, we can finally claim it.
+				 */
+				r->mr_pid = 0;
+				r->mr_txnid = (txnid_t)-1;
+				r->mr_tid = tid;
+				if (i == nr)
+					ti->mti_numreaders = ++nr;
+				env->me_close_readers = nr;
+				r->mr_pid = pid;
+				UNLOCK_MUTEX(rmutex);
+
+				new_notls = (env->me_flags & MDB_NOTLS);
+				if (!new_notls && (rc=pthread_setspecific(env->me_txkey, r))) {
+					r->mr_pid = 0;
+					return rc;
+				}
+			}
+			do /* LY: Retry on a race, ITS#7970. */
+				r->mr_txnid = ti->mti_txnid;
+			while(r->mr_txnid != ti->mti_txnid);
+			txn->mt_txnid = r->mr_txnid;
+			txn->mt_u.reader = r;
+			meta = env->me_metas[txn->mt_txnid & 1];
+		}
+
+	} else {
+		/* Not yet touching txn == env->me_txn0, it may be active */
+		if (ti) {
+			if (LOCK_MUTEX(rc, env, env->me_wmutex))
+				return rc;
+			txn->mt_txnid = ti->mti_txnid;
+			meta = env->me_metas[txn->mt_txnid & 1];
+		} else {
+			meta = mdb_env_pick_meta(env);
+			txn->mt_txnid = meta->mm_txnid;
+		}
+		txn->mt_txnid++;
+#if MDB_DEBUG
+		if (txn->mt_txnid == mdb_debug_start)
+			mdb_debug = 1;
+#endif
+		txn->mt_child = NULL;
+		txn->mt_loose_pgs = NULL;
+		txn->mt_loose_count = 0;
+		txn->mt_dirty_room = MDB_IDL_UM_MAX;
+		txn->mt_u.dirty_list = env->me_dirty_list;
+		txn->mt_u.dirty_list[0].mid = 0;
+		txn->mt_free_pgs = env->me_free_pgs;
+		txn->mt_free_pgs[0] = 0;
+		txn->mt_spill_pgs = NULL;
+		env->me_txn = txn;
+		memcpy(txn->mt_dbiseqs, env->me_dbiseqs, env->me_maxdbs * sizeof(unsigned int));
+	}
+
+	/* Copy the DB info and flags */
+	memcpy(txn->mt_dbs, meta->mm_dbs, CORE_DBS * sizeof(MDB_db));
+
+	/* Moved to here to avoid a data race in read TXNs */
+	txn->mt_next_pgno = meta->mm_last_pg+1;
+
+	txn->mt_flags = flags;
+
+	/* Setup db info */
+	txn->mt_numdbs = env->me_numdbs;
+	for (i=CORE_DBS; i<txn->mt_numdbs; i++) {
+		x = env->me_dbflags[i];
+		txn->mt_dbs[i].md_flags = x & PERSISTENT_FLAGS;
+		txn->mt_dbflags[i] = (x & MDB_VALID) ? DB_VALID|DB_USRVALID|DB_STALE : 0;
+	}
+	txn->mt_dbflags[MAIN_DBI] = DB_VALID|DB_USRVALID;
+	txn->mt_dbflags[FREE_DBI] = DB_VALID;
+
+	if (env->me_flags & MDB_FATAL_ERROR) {
+		DPUTS("environment had fatal error, must shutdown!");
+		rc = MDB_PANIC;
+	} else if (env->me_maxpg < txn->mt_next_pgno) {
+		rc = MDB_MAP_RESIZED;
+	} else {
+		return MDB_SUCCESS;
+	}
+	mdb_txn_end(txn, new_notls /*0 or MDB_END_SLOT*/ | MDB_END_FAIL_BEGIN);
+	return rc;
+}
+
+int
+mdb_txn_renew(MDB_txn *txn)
+{
+	int rc;
+
+	if (!txn || !F_ISSET(txn->mt_flags, MDB_TXN_RDONLY|MDB_TXN_FINISHED))
+		return EINVAL;
+
+	rc = mdb_txn_renew0(txn);
+	if (rc == MDB_SUCCESS) {
+		DPRINTF(("renew txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
+			txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
+			(void *)txn, (void *)txn->mt_env, txn->mt_dbs[MAIN_DBI].md_root));
+	}
+	return rc;
+}
+
+int
+mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
+{
+	MDB_txn *txn;
+	MDB_ntxn *ntxn;
+	int rc, size, tsize;
+
+	flags &= MDB_TXN_BEGIN_FLAGS;
+	flags |= env->me_flags & MDB_WRITEMAP;
+
+	if (env->me_flags & MDB_RDONLY & ~flags) /* write txn in RDONLY env */
+		return EACCES;
+
+	if (parent) {
+		/* Nested transactions: Max 1 child, write txns only, no writemap */
+		flags |= parent->mt_flags;
+		if (flags & (MDB_RDONLY|MDB_WRITEMAP|MDB_TXN_BLOCKED)) {
+			return (parent->mt_flags & MDB_TXN_RDONLY) ? EINVAL : MDB_BAD_TXN;
+		}
+		/* Child txns save MDB_pgstate and use own copy of cursors */
+		size = env->me_maxdbs * (sizeof(MDB_db)+sizeof(MDB_cursor *)+1);
+		size += tsize = sizeof(MDB_ntxn);
+	} else if (flags & MDB_RDONLY) {
+		size = env->me_maxdbs * (sizeof(MDB_db)+1);
+		size += tsize = sizeof(MDB_txn);
+	} else {
+		/* Reuse preallocated write txn. However, do not touch it until
+		 * mdb_txn_renew0() succeeds, since it currently may be active.
+		 */
+		txn = env->me_txn0;
+		goto renew;
+	}
+	if ((txn = calloc(1, size)) == NULL) {
+		DPRINTF(("calloc: %s", strerror(errno)));
+		return ENOMEM;
+	}
+	txn->mt_dbxs = env->me_dbxs;	/* static */
+	txn->mt_dbs = (MDB_db *) ((char *)txn + tsize);
+	txn->mt_dbflags = (unsigned char *)txn + size - env->me_maxdbs;
+	txn->mt_flags = flags;
+	txn->mt_env = env;
+
+	if (parent) {
+		unsigned int i;
+		txn->mt_cursors = (MDB_cursor **)(txn->mt_dbs + env->me_maxdbs);
+		txn->mt_dbiseqs = parent->mt_dbiseqs;
+		txn->mt_u.dirty_list = malloc(sizeof(MDB_ID2)*MDB_IDL_UM_SIZE);
+		if (!txn->mt_u.dirty_list ||
+			!(txn->mt_free_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX)))
+		{
+			free(txn->mt_u.dirty_list);
+			free(txn);
+			return ENOMEM;
+		}
+		txn->mt_txnid = parent->mt_txnid;
+		txn->mt_dirty_room = parent->mt_dirty_room;
+		txn->mt_u.dirty_list[0].mid = 0;
+		txn->mt_spill_pgs = NULL;
+		txn->mt_next_pgno = parent->mt_next_pgno;
+		parent->mt_flags |= MDB_TXN_HAS_CHILD;
+		parent->mt_child = txn;
+		txn->mt_parent = parent;
+		txn->mt_numdbs = parent->mt_numdbs;
+		memcpy(txn->mt_dbs, parent->mt_dbs, txn->mt_numdbs * sizeof(MDB_db));
+		/* Copy parent's mt_dbflags, but clear DB_NEW */
+		for (i=0; i<txn->mt_numdbs; i++)
+			txn->mt_dbflags[i] = parent->mt_dbflags[i] & ~DB_NEW;
+		rc = 0;
+		ntxn = (MDB_ntxn *)txn;
+		ntxn->mnt_pgstate = env->me_pgstate; /* save parent me_pghead & co */
+		if (env->me_pghead) {
+			size = MDB_IDL_SIZEOF(env->me_pghead);
+			env->me_pghead = mdb_midl_alloc(env->me_pghead[0]);
+			if (env->me_pghead)
+				memcpy(env->me_pghead, ntxn->mnt_pgstate.mf_pghead, size);
+			else
+				rc = ENOMEM;
+		}
+		if (!rc)
+			rc = mdb_cursor_shadow(parent, txn);
+		if (rc)
+			mdb_txn_end(txn, MDB_END_FAIL_BEGINCHILD);
+	} else { /* MDB_RDONLY */
+		txn->mt_dbiseqs = env->me_dbiseqs;
+renew:
+		rc = mdb_txn_renew0(txn);
+	}
+	if (rc) {
+		if (txn != env->me_txn0)
+			free(txn);
+	} else {
+		txn->mt_flags |= flags;	/* could not change txn=me_txn0 earlier */
+		*ret = txn;
+		DPRINTF(("begin txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
+			txn->mt_txnid, (flags & MDB_RDONLY) ? 'r' : 'w',
+			(void *) txn, (void *) env, txn->mt_dbs[MAIN_DBI].md_root));
+	}
+
+	return rc;
+}
+
+MDB_env *
+mdb_txn_env(MDB_txn *txn)
+{
+	if(!txn) return NULL;
+	return txn->mt_env;
+}
+
+size_t
+mdb_txn_id(MDB_txn *txn)
+{
+    if(!txn) return 0;
+    return txn->mt_txnid;
+}
+
+/** Export or close DBI handles opened in this txn. */
+static void
+mdb_dbis_update(MDB_txn *txn, int keep)
+{
+	int i;
+	MDB_dbi n = txn->mt_numdbs;
+	MDB_env *env = txn->mt_env;
+	unsigned char *tdbflags = txn->mt_dbflags;
+
+	for (i = n; --i >= CORE_DBS;) {
+		if (tdbflags[i] & DB_NEW) {
+			if (keep) {
+				env->me_dbflags[i] = txn->mt_dbs[i].md_flags | MDB_VALID;
+			} else {
+				char *ptr = env->me_dbxs[i].md_name.mv_data;
+				if (ptr) {
+					env->me_dbxs[i].md_name.mv_data = NULL;
+					env->me_dbxs[i].md_name.mv_size = 0;
+					env->me_dbflags[i] = 0;
+					env->me_dbiseqs[i]++;
+					free(ptr);
+				}
+			}
+		}
+	}
+	if (keep && env->me_numdbs < n)
+		env->me_numdbs = n;
+}
+
+/** End a transaction, except successful commit of a nested transaction.
+ * May be called twice for readonly txns: First reset it, then abort.
+ * @param[in] txn the transaction handle to end
+ * @param[in] mode why and how to end the transaction
+ */
+static void
+mdb_txn_end(MDB_txn *txn, unsigned mode)
+{
+	MDB_env	*env = txn->mt_env;
+#if MDB_DEBUG
+	static const char *const names[] = MDB_END_NAMES;
+#endif
+
+	/* Export or close DBI handles opened in this txn */
+	mdb_dbis_update(txn, mode & MDB_END_UPDATE);
+
+	DPRINTF(("%s txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
+		names[mode & MDB_END_OPMASK],
+		txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
+		(void *) txn, (void *)env, txn->mt_dbs[MAIN_DBI].md_root));
+
+	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
+		if (txn->mt_u.reader) {
+			txn->mt_u.reader->mr_txnid = (txnid_t)-1;
+			if (!(env->me_flags & MDB_NOTLS)) {
+				txn->mt_u.reader = NULL; /* txn does not own reader */
+			} else if (mode & MDB_END_SLOT) {
+				txn->mt_u.reader->mr_pid = 0;
+				txn->mt_u.reader = NULL;
+			} /* else txn owns the slot until it does MDB_END_SLOT */
+		}
+		txn->mt_numdbs = 0;		/* prevent further DBI activity */
+		txn->mt_flags |= MDB_TXN_FINISHED;
+
+	} else if (!F_ISSET(txn->mt_flags, MDB_TXN_FINISHED)) {
+		pgno_t *pghead = env->me_pghead;
+
+		if (!(mode & MDB_END_UPDATE)) /* !(already closed cursors) */
+			mdb_cursors_close(txn, 0);
+		if (!(env->me_flags & MDB_WRITEMAP)) {
+			mdb_dlist_free(txn);
+		}
+
+		txn->mt_numdbs = 0;
+		txn->mt_flags = MDB_TXN_FINISHED;
+
+		if (!txn->mt_parent) {
+			mdb_midl_shrink(&txn->mt_free_pgs);
+			env->me_free_pgs = txn->mt_free_pgs;
+			/* me_pgstate: */
+			env->me_pghead = NULL;
+			env->me_pglast = 0;
+
+			env->me_txn = NULL;
+			mode = 0;	/* txn == env->me_txn0, do not free() it */
+
+			/* The writer mutex was locked in mdb_txn_begin. */
+			if (env->me_txns)
+				UNLOCK_MUTEX(env->me_wmutex);
+		} else {
+			txn->mt_parent->mt_child = NULL;
+			txn->mt_parent->mt_flags &= ~MDB_TXN_HAS_CHILD;
+			env->me_pgstate = ((MDB_ntxn *)txn)->mnt_pgstate;
+			mdb_midl_free(txn->mt_free_pgs);
+			mdb_midl_free(txn->mt_spill_pgs);
+			free(txn->mt_u.dirty_list);
+		}
+
+		mdb_midl_free(pghead);
+	}
+
+	if (mode & MDB_END_FREE)
+		free(txn);
+}
+
+void
+mdb_txn_reset(MDB_txn *txn)
+{
+	if (txn == NULL)
+		return;
+
+	/* This call is only valid for read-only txns */
+	if (!(txn->mt_flags & MDB_TXN_RDONLY))
+		return;
+
+	mdb_txn_end(txn, MDB_END_RESET);
+}
+
+void
+mdb_txn_abort(MDB_txn *txn)
+{
+	if (txn == NULL)
+		return;
+
+	if (txn->mt_child)
+		mdb_txn_abort(txn->mt_child);
+
+	mdb_txn_end(txn, MDB_END_ABORT|MDB_END_SLOT|MDB_END_FREE);
+}
+
+/** Save the freelist as of this transaction to the freeDB.
+ * This changes the freelist. Keep trying until it stabilizes.
+ */
+static int
+mdb_freelist_save(MDB_txn *txn)
+{
+	/* env->me_pghead[] can grow and shrink during this call.
+	 * env->me_pglast and txn->mt_free_pgs[] can only grow.
+	 * Page numbers cannot disappear from txn->mt_free_pgs[].
+	 */
+	MDB_cursor mc;
+	MDB_env	*env = txn->mt_env;
+	int rc, maxfree_1pg = env->me_maxfree_1pg, more = 1;
+	txnid_t	pglast = 0, head_id = 0;
+	pgno_t	freecnt = 0, *free_pgs, *mop;
+	ssize_t	head_room = 0, total_room = 0, mop_len, clean_limit;
+
+	mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
+
+	if (env->me_pghead) {
+		/* Make sure first page of freeDB is touched and on freelist */
+		rc = mdb_page_search(&mc, NULL, MDB_PS_FIRST|MDB_PS_MODIFY);
+		if (rc && rc != MDB_NOTFOUND)
+			return rc;
+	}
+
+	if (!env->me_pghead && txn->mt_loose_pgs) {
+		/* Put loose page numbers in mt_free_pgs, since
+		 * we may be unable to return them to me_pghead.
+		 */
+		MDB_page *mp = txn->mt_loose_pgs;
+		if ((rc = mdb_midl_need(&txn->mt_free_pgs, txn->mt_loose_count)) != 0)
+			return rc;
+		for (; mp; mp = NEXT_LOOSE_PAGE(mp))
+			mdb_midl_xappend(txn->mt_free_pgs, mp->mp_pgno);
+		txn->mt_loose_pgs = NULL;
+		txn->mt_loose_count = 0;
+	}
+
+	/* MDB_RESERVE cancels meminit in ovpage malloc (when no WRITEMAP) */
+	clean_limit = (env->me_flags & (MDB_NOMEMINIT|MDB_WRITEMAP))
+		? SSIZE_MAX : maxfree_1pg;
+
+	for (;;) {
+		/* Come back here after each Put() in case freelist changed */
+		MDB_val key, data;
+		pgno_t *pgs;
+		ssize_t j;
+
+		/* If using records from freeDB which we have not yet
+		 * deleted, delete them and any we reserved for me_pghead.
+		 */
+		while (pglast < env->me_pglast) {
+			rc = mdb_cursor_first(&mc, &key, NULL);
+			if (rc)
+				return rc;
+			pglast = head_id = *(txnid_t *)key.mv_data;
+			total_room = head_room = 0;
+			mdb_tassert(txn, pglast <= env->me_pglast);
+			rc = mdb_cursor_del(&mc, 0);
+			if (rc)
+				return rc;
+		}
+
+		/* Save the IDL of pages freed by this txn, to a single record */
+		if (freecnt < txn->mt_free_pgs[0]) {
+			if (!freecnt) {
+				/* Make sure last page of freeDB is touched and on freelist */
+				rc = mdb_page_search(&mc, NULL, MDB_PS_LAST|MDB_PS_MODIFY);
+				if (rc && rc != MDB_NOTFOUND)
+					return rc;
+			}
+			free_pgs = txn->mt_free_pgs;
+			/* Write to last page of freeDB */
+			key.mv_size = sizeof(txn->mt_txnid);
+			key.mv_data = &txn->mt_txnid;
+			do {
+				freecnt = free_pgs[0];
+				data.mv_size = MDB_IDL_SIZEOF(free_pgs);
+				rc = mdb_cursor_put(&mc, &key, &data, MDB_RESERVE);
+				if (rc)
+					return rc;
+				/* Retry if mt_free_pgs[] grew during the Put() */
+				free_pgs = txn->mt_free_pgs;
+			} while (freecnt < free_pgs[0]);
+			mdb_midl_sort(free_pgs);
+			memcpy(data.mv_data, free_pgs, data.mv_size);
+#if (MDB_DEBUG) > 1
+			{
+				unsigned int i = free_pgs[0];
+				DPRINTF(("IDL write txn %"Z"u root %"Z"u num %u",
+					txn->mt_txnid, txn->mt_dbs[FREE_DBI].md_root, i));
+				for (; i; i--)
+					DPRINTF(("IDL %"Z"u", free_pgs[i]));
+			}
+#endif
+			continue;
+		}
+
+		mop = env->me_pghead;
+		mop_len = (mop ? mop[0] : 0) + txn->mt_loose_count;
+
+		/* Reserve records for me_pghead[]. Split it if multi-page,
+		 * to avoid searching freeDB for a page range. Use keys in
+		 * range [1,me_pglast]: Smaller than txnid of oldest reader.
+		 */
+		if (total_room >= mop_len) {
+			if (total_room == mop_len || --more < 0)
+				break;
+		} else if (head_room >= maxfree_1pg && head_id > 1) {
+			/* Keep current record (overflow page), add a new one */
+			head_id--;
+			head_room = 0;
+		}
+		/* (Re)write {key = head_id, IDL length = head_room} */
+		total_room -= head_room;
+		head_room = mop_len - total_room;
+		if (head_room > maxfree_1pg && head_id > 1) {
+			/* Overflow multi-page for part of me_pghead */
+			head_room /= head_id; /* amortize page sizes */
+			head_room += maxfree_1pg - head_room % (maxfree_1pg + 1);
+		} else if (head_room < 0) {
+			/* Rare case, not bothering to delete this record */
+			head_room = 0;
+		}
+		key.mv_size = sizeof(head_id);
+		key.mv_data = &head_id;
+		data.mv_size = (head_room + 1) * sizeof(pgno_t);
+		rc = mdb_cursor_put(&mc, &key, &data, MDB_RESERVE);
+		if (rc)
+			return rc;
+		/* IDL is initially empty, zero out at least the length */
+		pgs = (pgno_t *)data.mv_data;
+		j = head_room > clean_limit ? head_room : 0;
+		do {
+			pgs[j] = 0;
+		} while (--j >= 0);
+		total_room += head_room;
+	}
+
+	/* Return loose page numbers to me_pghead, though usually none are
+	 * left at this point.  The pages themselves remain in dirty_list.
+	 */
+	if (txn->mt_loose_pgs) {
+		MDB_page *mp = txn->mt_loose_pgs;
+		unsigned count = txn->mt_loose_count;
+		MDB_IDL loose;
+		/* Room for loose pages + temp IDL with same */
+		if ((rc = mdb_midl_need(&env->me_pghead, 2*count+1)) != 0)
+			return rc;
+		mop = env->me_pghead;
+		loose = mop + MDB_IDL_ALLOCLEN(mop) - count;
+		for (count = 0; mp; mp = NEXT_LOOSE_PAGE(mp))
+			loose[ ++count ] = mp->mp_pgno;
+		loose[0] = count;
+		mdb_midl_sort(loose);
+		mdb_midl_xmerge(mop, loose);
+		txn->mt_loose_pgs = NULL;
+		txn->mt_loose_count = 0;
+		mop_len = mop[0];
+	}
+
+	/* Fill in the reserved me_pghead records */
+	rc = MDB_SUCCESS;
+	if (mop_len) {
+		MDB_val key, data;
+
+		mop += mop_len;
+		rc = mdb_cursor_first(&mc, &key, &data);
+		for (; !rc; rc = mdb_cursor_next(&mc, &key, &data, MDB_NEXT)) {
+			txnid_t id = *(txnid_t *)key.mv_data;
+			ssize_t	len = (ssize_t)(data.mv_size / sizeof(MDB_ID)) - 1;
+			MDB_ID save;
+
+			mdb_tassert(txn, len >= 0 && id <= env->me_pglast);
+			key.mv_data = &id;
+			if (len > mop_len) {
+				len = mop_len;
+				data.mv_size = (len + 1) * sizeof(MDB_ID);
+			}
+			data.mv_data = mop -= len;
+			save = mop[0];
+			mop[0] = len;
+			rc = mdb_cursor_put(&mc, &key, &data, MDB_CURRENT);
+			mop[0] = save;
+			if (rc || !(mop_len -= len))
+				break;
+		}
+	}
+	return rc;
+}
+
+/** Flush (some) dirty pages to the map, after clearing their dirty flag.
+ * @param[in] txn the transaction that's being committed
+ * @param[in] keep number of initial pages in dirty_list to keep dirty.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_flush(MDB_txn *txn, int keep)
+{
+	MDB_env		*env = txn->mt_env;
+	MDB_ID2L	dl = txn->mt_u.dirty_list;
+	unsigned	psize = env->me_psize, j;
+	int			i, pagecount = dl[0].mid, rc;
+	size_t		size = 0, pos = 0;
+	pgno_t		pgno = 0;
+	MDB_page	*dp = NULL;
+#ifdef _WIN32
+	OVERLAPPED	ov;
+#else
+	struct iovec iov[MDB_COMMIT_PAGES];
+	ssize_t		wpos = 0, wsize = 0, wres;
+	size_t		next_pos = 1; /* impossible pos, so pos != next_pos */
+	int			n = 0;
+#endif
+
+	j = i = keep;
+
+	if (env->me_flags & MDB_WRITEMAP) {
+		/* Clear dirty flags */
+		while (++i <= pagecount) {
+			dp = dl[i].mptr;
+			/* Don't flush this page yet */
+			if (dp->mp_flags & (P_LOOSE|P_KEEP)) {
+				dp->mp_flags &= ~P_KEEP;
+				dl[++j] = dl[i];
+				continue;
+			}
+			dp->mp_flags &= ~P_DIRTY;
+		}
+		goto done;
+	}
+
+	/* Write the pages */
+	for (;;) {
+		if (++i <= pagecount) {
+			dp = dl[i].mptr;
+			/* Don't flush this page yet */
+			if (dp->mp_flags & (P_LOOSE|P_KEEP)) {
+				dp->mp_flags &= ~P_KEEP;
+				dl[i].mid = 0;
+				continue;
+			}
+			pgno = dl[i].mid;
+			/* clear dirty flag */
+			dp->mp_flags &= ~P_DIRTY;
+			pos = pgno * psize;
+			size = psize;
+			if (IS_OVERFLOW(dp)) size *= dp->mp_pages;
+		}
+#ifdef _WIN32
+		else break;
+
+		/* Windows actually supports scatter/gather I/O, but only on
+		 * unbuffered file handles. Since we're relying on the OS page
+		 * cache for all our data, that's self-defeating. So we just
+		 * write pages one at a time. We use the ov structure to set
+		 * the write offset, to at least save the overhead of a Seek
+		 * system call.
+		 */
+		DPRINTF(("committing page %"Z"u", pgno));
+		memset(&ov, 0, sizeof(ov));
+		ov.Offset = pos & 0xffffffff;
+		ov.OffsetHigh = pos >> 16 >> 16;
+		if (!WriteFile(env->me_fd, dp, size, NULL, &ov)) {
+			rc = ErrCode();
+			DPRINTF(("WriteFile: %d", rc));
+			return rc;
+		}
+#else
+		/* Write up to MDB_COMMIT_PAGES dirty pages at a time. */
+		if (pos!=next_pos || n==MDB_COMMIT_PAGES || wsize+size>MAX_WRITE) {
+			if (n) {
+retry_write:
+				/* Write previous page(s) */
+#ifdef MDB_USE_PWRITEV
+				wres = pwritev(env->me_fd, iov, n, wpos);
+#else
+				if (n == 1) {
+					wres = pwrite(env->me_fd, iov[0].iov_base, wsize, wpos);
+				} else {
+retry_seek:
+					if (lseek(env->me_fd, wpos, SEEK_SET) == -1) {
+						rc = ErrCode();
+						if (rc == EINTR)
+							goto retry_seek;
+						DPRINTF(("lseek: %s", strerror(rc)));
+						return rc;
+					}
+					wres = writev(env->me_fd, iov, n);
+				}
+#endif
+				if (wres != wsize) {
+					if (wres < 0) {
+						rc = ErrCode();
+						if (rc == EINTR)
+							goto retry_write;
+						DPRINTF(("Write error: %s", strerror(rc)));
+					} else {
+						rc = EIO; /* TODO: Use which error code? */
+						DPUTS("short write, filesystem full?");
+					}
+					return rc;
+				}
+				n = 0;
+			}
+			if (i > pagecount)
+				break;
+			wpos = pos;
+			wsize = 0;
+		}
+		DPRINTF(("committing page %"Z"u", pgno));
+		next_pos = pos + size;
+		iov[n].iov_len = size;
+		iov[n].iov_base = (char *)dp;
+		wsize += size;
+		n++;
+#endif	/* _WIN32 */
+	}
+
+	/* MIPS has cache coherency issues, this is a no-op everywhere else
+	 * Note: for any size >= on-chip cache size, entire on-chip cache is
+	 * flushed.
+	 */
+	CACHEFLUSH(env->me_map, txn->mt_next_pgno * env->me_psize, DCACHE);
+
+	for (i = keep; ++i <= pagecount; ) {
+		dp = dl[i].mptr;
+		/* This is a page we skipped above */
+		if (!dl[i].mid) {
+			dl[++j] = dl[i];
+			dl[j].mid = dp->mp_pgno;
+			continue;
+		}
+		mdb_dpage_free(env, dp);
+	}
+
+done:
+	i--;
+	txn->mt_dirty_room += i - j;
+	dl[0].mid = j;
+	return MDB_SUCCESS;
+}
+
+int
+mdb_txn_commit(MDB_txn *txn)
+{
+	int		rc;
+	unsigned int i, end_mode;
+	MDB_env	*env;
+
+	if (txn == NULL)
+		return EINVAL;
+
+	/* mdb_txn_end() mode for a commit which writes nothing */
+	end_mode = MDB_END_EMPTY_COMMIT|MDB_END_UPDATE|MDB_END_SLOT|MDB_END_FREE;
+
+	if (txn->mt_child) {
+		rc = mdb_txn_commit(txn->mt_child);
+		if (rc)
+			goto fail;
+	}
+
+	env = txn->mt_env;
+
+	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
+		goto done;
+	}
+
+	if (txn->mt_flags & (MDB_TXN_FINISHED|MDB_TXN_ERROR)) {
+		DPUTS("txn has failed/finished, can't commit");
+		if (txn->mt_parent)
+			txn->mt_parent->mt_flags |= MDB_TXN_ERROR;
+		rc = MDB_BAD_TXN;
+		goto fail;
+	}
+
+	if (txn->mt_parent) {
+		MDB_txn *parent = txn->mt_parent;
+		MDB_page **lp;
+		MDB_ID2L dst, src;
+		MDB_IDL pspill;
+		unsigned x, y, len, ps_len;
+
+		/* Append our free list to parent's */
+		rc = mdb_midl_append_list(&parent->mt_free_pgs, txn->mt_free_pgs);
+		if (rc)
+			goto fail;
+		mdb_midl_free(txn->mt_free_pgs);
+		/* Failures after this must either undo the changes
+		 * to the parent or set MDB_TXN_ERROR in the parent.
+		 */
+
+		parent->mt_next_pgno = txn->mt_next_pgno;
+		parent->mt_flags = txn->mt_flags;
+
+		/* Merge our cursors into parent's and close them */
+		mdb_cursors_close(txn, 1);
+
+		/* Update parent's DB table. */
+		memcpy(parent->mt_dbs, txn->mt_dbs, txn->mt_numdbs * sizeof(MDB_db));
+		parent->mt_numdbs = txn->mt_numdbs;
+		parent->mt_dbflags[FREE_DBI] = txn->mt_dbflags[FREE_DBI];
+		parent->mt_dbflags[MAIN_DBI] = txn->mt_dbflags[MAIN_DBI];
+		for (i=CORE_DBS; i<txn->mt_numdbs; i++) {
+			/* preserve parent's DB_NEW status */
+			x = parent->mt_dbflags[i] & DB_NEW;
+			parent->mt_dbflags[i] = txn->mt_dbflags[i] | x;
+		}
+
+		dst = parent->mt_u.dirty_list;
+		src = txn->mt_u.dirty_list;
+		/* Remove anything in our dirty list from parent's spill list */
+		if ((pspill = parent->mt_spill_pgs) && (ps_len = pspill[0])) {
+			x = y = ps_len;
+			pspill[0] = (pgno_t)-1;
+			/* Mark our dirty pages as deleted in parent spill list */
+			for (i=0, len=src[0].mid; ++i <= len; ) {
+				MDB_ID pn = src[i].mid << 1;
+				while (pn > pspill[x])
+					x--;
+				if (pn == pspill[x]) {
+					pspill[x] = 1;
+					y = --x;
+				}
+			}
+			/* Squash deleted pagenums if we deleted any */
+			for (x=y; ++x <= ps_len; )
+				if (!(pspill[x] & 1))
+					pspill[++y] = pspill[x];
+			pspill[0] = y;
+		}
+
+		/* Remove anything in our spill list from parent's dirty list */
+		if (txn->mt_spill_pgs && txn->mt_spill_pgs[0]) {
+			for (i=1; i<=txn->mt_spill_pgs[0]; i++) {
+				MDB_ID pn = txn->mt_spill_pgs[i];
+				if (pn & 1)
+					continue;	/* deleted spillpg */
+				pn >>= 1;
+				y = mdb_mid2l_search(dst, pn);
+				if (y <= dst[0].mid && dst[y].mid == pn) {
+					free(dst[y].mptr);
+					while (y < dst[0].mid) {
+						dst[y] = dst[y+1];
+						y++;
+					}
+					dst[0].mid--;
+				}
+			}
+		}
+
+		/* Find len = length of merging our dirty list with parent's */
+		x = dst[0].mid;
+		dst[0].mid = 0;		/* simplify loops */
+		if (parent->mt_parent) {
+			len = x + src[0].mid;
+			y = mdb_mid2l_search(src, dst[x].mid + 1) - 1;
+			for (i = x; y && i; y--) {
+				pgno_t yp = src[y].mid;
+				while (yp < dst[i].mid)
+					i--;
+				if (yp == dst[i].mid) {
+					i--;
+					len--;
+				}
+			}
+		} else { /* Simplify the above for single-ancestor case */
+			len = MDB_IDL_UM_MAX - txn->mt_dirty_room;
+		}
+		/* Merge our dirty list with parent's */
+		y = src[0].mid;
+		for (i = len; y; dst[i--] = src[y--]) {
+			pgno_t yp = src[y].mid;
+			while (yp < dst[x].mid)
+				dst[i--] = dst[x--];
+			if (yp == dst[x].mid)
+				free(dst[x--].mptr);
+		}
+		mdb_tassert(txn, i == x);
+		dst[0].mid = len;
+		free(txn->mt_u.dirty_list);
+		parent->mt_dirty_room = txn->mt_dirty_room;
+		if (txn->mt_spill_pgs) {
+			if (parent->mt_spill_pgs) {
+				/* TODO: Prevent failure here, so parent does not fail */
+				rc = mdb_midl_append_list(&parent->mt_spill_pgs, txn->mt_spill_pgs);
+				if (rc)
+					parent->mt_flags |= MDB_TXN_ERROR;
+				mdb_midl_free(txn->mt_spill_pgs);
+				mdb_midl_sort(parent->mt_spill_pgs);
+			} else {
+				parent->mt_spill_pgs = txn->mt_spill_pgs;
+			}
+		}
+
+		/* Append our loose page list to parent's */
+		for (lp = &parent->mt_loose_pgs; *lp; lp = &NEXT_LOOSE_PAGE(*lp))
+			;
+		*lp = txn->mt_loose_pgs;
+		parent->mt_loose_count += txn->mt_loose_count;
+
+		parent->mt_child = NULL;
+		mdb_midl_free(((MDB_ntxn *)txn)->mnt_pgstate.mf_pghead);
+		free(txn);
+		return rc;
+	}
+
+	if (txn != env->me_txn) {
+		DPUTS("attempt to commit unknown transaction");
+		rc = EINVAL;
+		goto fail;
+	}
+
+	mdb_cursors_close(txn, 0);
+
+	if (!txn->mt_u.dirty_list[0].mid &&
+		!(txn->mt_flags & (MDB_TXN_DIRTY|MDB_TXN_SPILLS)))
+		goto done;
+
+	DPRINTF(("committing txn %"Z"u %p on mdbenv %p, root page %"Z"u",
+	    txn->mt_txnid, (void*)txn, (void*)env, txn->mt_dbs[MAIN_DBI].md_root));
+
+	/* Update DB root pointers */
+	if (txn->mt_numdbs > CORE_DBS) {
+		MDB_cursor mc;
+		MDB_dbi i;
+		MDB_val data;
+		data.mv_size = sizeof(MDB_db);
+
+		mdb_cursor_init(&mc, txn, MAIN_DBI, NULL);
+		for (i = CORE_DBS; i < txn->mt_numdbs; i++) {
+			if (txn->mt_dbflags[i] & DB_DIRTY) {
+				if (TXN_DBI_CHANGED(txn, i)) {
+					rc = MDB_BAD_DBI;
+					goto fail;
+				}
+				data.mv_data = &txn->mt_dbs[i];
+				rc = mdb_cursor_put(&mc, &txn->mt_dbxs[i].md_name, &data,
+					F_SUBDATA);
+				if (rc)
+					goto fail;
+			}
+		}
+	}
+
+	rc = mdb_freelist_save(txn);
+	if (rc)
+		goto fail;
+
+	mdb_midl_free(env->me_pghead);
+	env->me_pghead = NULL;
+	mdb_midl_shrink(&txn->mt_free_pgs);
+
+#if (MDB_DEBUG) > 2
+	mdb_audit(txn);
+#endif
+
+	if ((rc = mdb_page_flush(txn, 0)) ||
+		(rc = mdb_env_sync(env, 0)) ||
+		(rc = mdb_env_write_meta(txn)))
+		goto fail;
+	end_mode = MDB_END_COMMITTED|MDB_END_UPDATE;
+
+done:
+	mdb_txn_end(txn, end_mode);
+	return MDB_SUCCESS;
+
+fail:
+	mdb_txn_abort(txn);
+	return rc;
+}
+
+/** Read the environment parameters of a DB environment before
+ * mapping it into memory.
+ * @param[in] env the environment handle
+ * @param[out] meta address of where to store the meta information
+ * @return 0 on success, non-zero on failure.
+ */
+static int ESECT
+mdb_env_read_header(MDB_env *env, MDB_meta *meta)
+{
+	MDB_metabuf	pbuf;
+	MDB_page	*p;
+	MDB_meta	*m;
+	int			i, rc, off;
+	enum { Size = sizeof(pbuf) };
+
+	/* We don't know the page size yet, so use a minimum value.
+	 * Read both meta pages so we can use the latest one.
+	 */
+
+	for (i=off=0; i<NUM_METAS; i++, off += meta->mm_psize) {
+#ifdef _WIN32
+		DWORD len;
+		OVERLAPPED ov;
+		memset(&ov, 0, sizeof(ov));
+		ov.Offset = off;
+		rc = ReadFile(env->me_fd, &pbuf, Size, &len, &ov) ? (int)len : -1;
+		if (rc == -1 && ErrCode() == ERROR_HANDLE_EOF)
+			rc = 0;
+#else
+		rc = pread(env->me_fd, &pbuf, Size, off);
+#endif
+		if (rc != Size) {
+			if (rc == 0 && off == 0)
+				return ENOENT;
+			rc = rc < 0 ? (int) ErrCode() : MDB_INVALID;
+			DPRINTF(("read: %s", mdb_strerror(rc)));
+			return rc;
+		}
+
+		p = (MDB_page *)&pbuf;
+
+		if (!F_ISSET(p->mp_flags, P_META)) {
+			DPRINTF(("page %"Z"u not a meta page", p->mp_pgno));
+			return MDB_INVALID;
+		}
+
+		m = METADATA(p);
+		if (m->mm_magic != MDB_MAGIC) {
+			DPUTS("meta has invalid magic");
+			return MDB_INVALID;
+		}
+
+		if (m->mm_version != MDB_DATA_VERSION) {
+			DPRINTF(("database is version %u, expected version %u",
+				m->mm_version, MDB_DATA_VERSION));
+			return MDB_VERSION_MISMATCH;
+		}
+
+		if (off == 0 || m->mm_txnid > meta->mm_txnid)
+			*meta = *m;
+	}
+	return 0;
+}
+
+/** Fill in most of the zeroed #MDB_meta for an empty database environment */
+static void ESECT
+mdb_env_init_meta0(MDB_env *env, MDB_meta *meta)
+{
+	meta->mm_magic = MDB_MAGIC;
+	meta->mm_version = MDB_DATA_VERSION;
+	meta->mm_mapsize = env->me_mapsize;
+	meta->mm_psize = env->me_psize;
+	meta->mm_last_pg = NUM_METAS-1;
+	meta->mm_flags = env->me_flags & 0xffff;
+	meta->mm_flags |= MDB_INTEGERKEY; /* this is mm_dbs[FREE_DBI].md_flags */
+	meta->mm_dbs[FREE_DBI].md_root = P_INVALID;
+	meta->mm_dbs[MAIN_DBI].md_root = P_INVALID;
+}
+
+/** Write the environment parameters of a freshly created DB environment.
+ * @param[in] env the environment handle
+ * @param[in] meta the #MDB_meta to write
+ * @return 0 on success, non-zero on failure.
+ */
+static int ESECT
+mdb_env_init_meta(MDB_env *env, MDB_meta *meta)
+{
+	MDB_page *p, *q;
+	int rc;
+	unsigned int	 psize;
+#ifdef _WIN32
+	DWORD len;
+	OVERLAPPED ov;
+	memset(&ov, 0, sizeof(ov));
+#define DO_PWRITE(rc, fd, ptr, size, len, pos)	do { \
+	ov.Offset = pos;	\
+	rc = WriteFile(fd, ptr, size, &len, &ov);	} while(0)
+#else
+	int len;
+#define DO_PWRITE(rc, fd, ptr, size, len, pos)	do { \
+	len = pwrite(fd, ptr, size, pos);	\
+	if (len == -1 && ErrCode() == EINTR) continue; \
+	rc = (len >= 0); break; } while(1)
+#endif
+
+	DPUTS("writing new meta page");
+
+	psize = env->me_psize;
+
+	p = calloc(NUM_METAS, psize);
+	if (!p)
+		return ENOMEM;
+
+	p->mp_pgno = 0;
+	p->mp_flags = P_META;
+	*(MDB_meta *)METADATA(p) = *meta;
+
+	q = (MDB_page *)((char *)p + psize);
+	q->mp_pgno = 1;
+	q->mp_flags = P_META;
+	*(MDB_meta *)METADATA(q) = *meta;
+
+	DO_PWRITE(rc, env->me_fd, p, psize * NUM_METAS, len, 0);
+	if (!rc)
+		rc = ErrCode();
+	else if ((unsigned) len == psize * NUM_METAS)
+		rc = MDB_SUCCESS;
+	else
+		rc = ENOSPC;
+	free(p);
+	return rc;
+}
+
+/** Update the environment info to commit a transaction.
+ * @param[in] txn the transaction that's being committed
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_env_write_meta(MDB_txn *txn)
+{
+	MDB_env *env;
+	MDB_meta	meta, metab, *mp;
+	unsigned flags;
+	size_t mapsize;
+	off_t off;
+	int rc, len, toggle;
+	char *ptr;
+	HANDLE mfd;
+#ifdef _WIN32
+	OVERLAPPED ov;
+#else
+	int r2;
+#endif
+
+	toggle = txn->mt_txnid & 1;
+	DPRINTF(("writing meta page %d for root page %"Z"u",
+		toggle, txn->mt_dbs[MAIN_DBI].md_root));
+
+	env = txn->mt_env;
+	flags = env->me_flags;
+	mp = env->me_metas[toggle];
+	mapsize = env->me_metas[toggle ^ 1]->mm_mapsize;
+	/* Persist any increases of mapsize config */
+	if (mapsize < env->me_mapsize)
+		mapsize = env->me_mapsize;
+
+	if (flags & MDB_WRITEMAP) {
+		mp->mm_mapsize = mapsize;
+		mp->mm_dbs[FREE_DBI] = txn->mt_dbs[FREE_DBI];
+		mp->mm_dbs[MAIN_DBI] = txn->mt_dbs[MAIN_DBI];
+		mp->mm_last_pg = txn->mt_next_pgno - 1;
+#if (__GNUC__ * 100 + __GNUC_MINOR__ >= 404) && /* TODO: portability */	\
+	!(defined(__i386__) || defined(__x86_64__))
+		/* LY: issue a memory barrier, if not x86. ITS#7969 */
+		__sync_synchronize();
+#endif
+		mp->mm_txnid = txn->mt_txnid;
+		if (!(flags & (MDB_NOMETASYNC|MDB_NOSYNC))) {
+			unsigned meta_size = env->me_psize;
+			rc = (env->me_flags & MDB_MAPASYNC) ? MS_ASYNC : MS_SYNC;
+			ptr = (char *)mp - PAGEHDRSZ;
+#ifndef _WIN32	/* POSIX msync() requires ptr = start of OS page */
+			r2 = (ptr - env->me_map) & (env->me_os_psize - 1);
+			ptr -= r2;
+			meta_size += r2;
+#endif
+			if (MDB_MSYNC(ptr, meta_size, rc)) {
+				rc = ErrCode();
+				goto fail;
+			}
+		}
+		goto done;
+	}
+	metab.mm_txnid = mp->mm_txnid;
+	metab.mm_last_pg = mp->mm_last_pg;
+
+	meta.mm_mapsize = mapsize;
+	meta.mm_dbs[FREE_DBI] = txn->mt_dbs[FREE_DBI];
+	meta.mm_dbs[MAIN_DBI] = txn->mt_dbs[MAIN_DBI];
+	meta.mm_last_pg = txn->mt_next_pgno - 1;
+	meta.mm_txnid = txn->mt_txnid;
+
+	off = offsetof(MDB_meta, mm_mapsize);
+	ptr = (char *)&meta + off;
+	len = sizeof(MDB_meta) - off;
+	off += (char *)mp - env->me_map;
+
+	/* Write to the SYNC fd unless MDB_NOSYNC/MDB_NOMETASYNC.
+	 * (me_mfd goes to the same file as me_fd, but writing to it
+	 * also syncs to disk.  Avoids a separate fdatasync() call.)
+	 */
+	mfd = (flags & (MDB_NOSYNC|MDB_NOMETASYNC)) ? env->me_fd : env->me_mfd;
+#ifdef _WIN32
+	{
+		memset(&ov, 0, sizeof(ov));
+		ov.Offset = off;
+		if (!WriteFile(mfd, ptr, len, (DWORD *)&rc, &ov))
+			rc = -1;
+	}
+#else
+retry_write:
+	rc = pwrite(mfd, ptr, len, off);
+#endif
+	if (rc != len) {
+		rc = rc < 0 ? ErrCode() : EIO;
+#ifndef _WIN32
+		if (rc == EINTR)
+			goto retry_write;
+#endif
+		DPUTS("write failed, disk error?");
+		/* On a failure, the pagecache still contains the new data.
+		 * Write some old data back, to prevent it from being used.
+		 * Use the non-SYNC fd; we know it will fail anyway.
+		 */
+		meta.mm_last_pg = metab.mm_last_pg;
+		meta.mm_txnid = metab.mm_txnid;
+#ifdef _WIN32
+		memset(&ov, 0, sizeof(ov));
+		ov.Offset = off;
+		WriteFile(env->me_fd, ptr, len, NULL, &ov);
+#else
+		r2 = pwrite(env->me_fd, ptr, len, off);
+		(void)r2;	/* Silence warnings. We don't care about pwrite's return value */
+#endif
+fail:
+		env->me_flags |= MDB_FATAL_ERROR;
+		return rc;
+	}
+	/* MIPS has cache coherency issues, this is a no-op everywhere else */
+	CACHEFLUSH(env->me_map + off, len, DCACHE);
+done:
+	/* Memory ordering issues are irrelevant; since the entire writer
+	 * is wrapped by wmutex, all of these changes will become visible
+	 * after the wmutex is unlocked. Since the DB is multi-version,
+	 * readers will get consistent data regardless of how fresh or
+	 * how stale their view of these values is.
+	 */
+	if (env->me_txns)
+		env->me_txns->mti_txnid = txn->mt_txnid;
+
+	return MDB_SUCCESS;
+}
+
+/** Check both meta pages to see which one is newer.
+ * @param[in] env the environment handle
+ * @return newest #MDB_meta.
+ */
+static MDB_meta *
+mdb_env_pick_meta(const MDB_env *env)
+{
+	MDB_meta *const *metas = env->me_metas;
+	return metas[ metas[0]->mm_txnid < metas[1]->mm_txnid ];
+}
+
+int ESECT
+mdb_env_create(MDB_env **env)
+{
+	MDB_env *e;
+
+	e = calloc(1, sizeof(MDB_env));
+	if (!e)
+		return ENOMEM;
+
+	e->me_maxreaders = DEFAULT_READERS;
+	e->me_maxdbs = e->me_numdbs = CORE_DBS;
+	e->me_fd = INVALID_HANDLE_VALUE;
+	e->me_lfd = INVALID_HANDLE_VALUE;
+	e->me_mfd = INVALID_HANDLE_VALUE;
+#ifdef MDB_USE_POSIX_SEM
+	e->me_rmutex = SEM_FAILED;
+	e->me_wmutex = SEM_FAILED;
+#endif
+	e->me_pid = getpid();
+	GET_PAGESIZE(e->me_os_psize);
+	VGMEMP_CREATE(e,0,0);
+	*env = e;
+	return MDB_SUCCESS;
+}
+
+static int ESECT
+mdb_env_map(MDB_env *env, void *addr)
+{
+	MDB_page *p;
+	unsigned int flags = env->me_flags;
+#ifdef _WIN32
+	int rc;
+	HANDLE mh;
+	LONG sizelo, sizehi;
+	size_t msize;
+
+	if (flags & MDB_RDONLY) {
+		/* Don't set explicit map size, use whatever exists */
+		msize = 0;
+		sizelo = 0;
+		sizehi = 0;
+	} else {
+		msize = env->me_mapsize;
+		sizelo = msize & 0xffffffff;
+		sizehi = msize >> 16 >> 16; /* only needed on Win64 */
+
+		/* Windows won't create mappings for zero length files.
+		 * and won't map more than the file size.
+		 * Just set the maxsize right now.
+		 */
+		if (SetFilePointer(env->me_fd, sizelo, &sizehi, 0) != (DWORD)sizelo
+			|| !SetEndOfFile(env->me_fd)
+			|| SetFilePointer(env->me_fd, 0, NULL, 0) != 0)
+			return ErrCode();
+	}
+
+	mh = CreateFileMapping(env->me_fd, NULL, flags & MDB_WRITEMAP ?
+		PAGE_READWRITE : PAGE_READONLY,
+		sizehi, sizelo, NULL);
+	if (!mh)
+		return ErrCode();
+	env->me_map = MapViewOfFileEx(mh, flags & MDB_WRITEMAP ?
+		FILE_MAP_WRITE : FILE_MAP_READ,
+		0, 0, msize, addr);
+	rc = env->me_map ? 0 : ErrCode();
+	CloseHandle(mh);
+	if (rc)
+		return rc;
+#else
+	int prot = PROT_READ;
+	if (flags & MDB_WRITEMAP) {
+		prot |= PROT_WRITE;
+		if (ftruncate(env->me_fd, env->me_mapsize) < 0)
+			return ErrCode();
+	}
+	env->me_map = mmap(addr, env->me_mapsize, prot, MAP_SHARED,
+		env->me_fd, 0);
+	if (env->me_map == MAP_FAILED) {
+		env->me_map = NULL;
+		return ErrCode();
+	}
+
+	if (flags & MDB_NORDAHEAD) {
+		/* Turn off readahead. It's harmful when the DB is larger than RAM. */
+#ifdef MADV_RANDOM
+		madvise(env->me_map, env->me_mapsize, MADV_RANDOM);
+#else
+#ifdef POSIX_MADV_RANDOM
+		posix_madvise(env->me_map, env->me_mapsize, POSIX_MADV_RANDOM);
+#endif /* POSIX_MADV_RANDOM */
+#endif /* MADV_RANDOM */
+	}
+#endif /* _WIN32 */
+
+	/* Can happen because the address argument to mmap() is just a
+	 * hint.  mmap() can pick another, e.g. if the range is in use.
+	 * The MAP_FIXED flag would prevent that, but then mmap could
+	 * instead unmap existing pages to make room for the new map.
+	 */
+	if (addr && env->me_map != addr)
+		return EBUSY;	/* TODO: Make a new MDB_* error code? */
+
+	p = (MDB_page *)env->me_map;
+	env->me_metas[0] = METADATA(p);
+	env->me_metas[1] = (MDB_meta *)((char *)env->me_metas[0] + env->me_psize);
+
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_set_mapsize(MDB_env *env, size_t size)
+{
+	/* If env is already open, caller is responsible for making
+	 * sure there are no active txns.
+	 */
+	if (env->me_map) {
+		int rc;
+		MDB_meta *meta;
+		void *old;
+		if (env->me_txn)
+			return EINVAL;
+		meta = mdb_env_pick_meta(env);
+		if (!size)
+			size = meta->mm_mapsize;
+		{
+			/* Silently round up to minimum if the size is too small */
+			size_t minsize = (meta->mm_last_pg + 1) * env->me_psize;
+			if (size < minsize)
+				size = minsize;
+		}
+		munmap(env->me_map, env->me_mapsize);
+		env->me_mapsize = size;
+		old = (env->me_flags & MDB_FIXEDMAP) ? env->me_map : NULL;
+		rc = mdb_env_map(env, old);
+		if (rc)
+			return rc;
+	}
+	env->me_mapsize = size;
+	if (env->me_psize)
+		env->me_maxpg = env->me_mapsize / env->me_psize;
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_set_maxdbs(MDB_env *env, MDB_dbi dbs)
+{
+	if (env->me_map)
+		return EINVAL;
+	env->me_maxdbs = dbs + CORE_DBS;
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_set_maxreaders(MDB_env *env, unsigned int readers)
+{
+	if (env->me_map || readers < 1)
+		return EINVAL;
+	env->me_maxreaders = readers;
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_get_maxreaders(MDB_env *env, unsigned int *readers)
+{
+	if (!env || !readers)
+		return EINVAL;
+	*readers = env->me_maxreaders;
+	return MDB_SUCCESS;
+}
+
+static int ESECT
+mdb_fsize(HANDLE fd, size_t *size)
+{
+#ifdef _WIN32
+	LARGE_INTEGER fsize;
+
+	if (!GetFileSizeEx(fd, &fsize))
+		return ErrCode();
+
+	*size = fsize.QuadPart;
+#else
+	struct stat st;
+
+	if (fstat(fd, &st))
+		return ErrCode();
+
+	*size = st.st_size;
+#endif
+	return MDB_SUCCESS;
+}
+
+
+#ifdef _WIN32
+typedef wchar_t	mdb_nchar_t;
+# define MDB_NAME(str)	L##str
+# define mdb_name_cpy	wcscpy
+#else
+/** Character type for file names: char on Unix, wchar_t on Windows */
+typedef char	mdb_nchar_t;
+# define MDB_NAME(str)	str		/**< #mdb_nchar_t[] string literal */
+# define mdb_name_cpy	strcpy	/**< Copy name (#mdb_nchar_t string) */
+#endif
+
+/** Filename - string of #mdb_nchar_t[] */
+typedef struct MDB_name {
+	int mn_len;					/**< Length  */
+	int mn_alloced;				/**< True if #mn_val was malloced */
+	mdb_nchar_t	*mn_val;		/**< Contents */
+} MDB_name;
+
+/** Filename suffixes [datafile,lockfile][without,with MDB_NOSUBDIR] */
+static const mdb_nchar_t *const mdb_suffixes[2][2] = {
+	{ MDB_NAME("/data.mdb"), MDB_NAME("")      },
+	{ MDB_NAME("/lock.mdb"), MDB_NAME("-lock") }
+};
+
+#define MDB_SUFFLEN 9	/**< Max string length in #mdb_suffixes[] */
+
+/** Set up filename + scratch area for filename suffix, for opening files.
+ * It should be freed with #mdb_fname_destroy().
+ * On Windows, paths are converted from char *UTF-8 to wchar_t *UTF-16.
+ *
+ * @param[in] path Pathname for #mdb_env_open().
+ * @param[in] envflags Whether a subdir and/or lockfile will be used.
+ * @param[out] fname Resulting filename, with room for a suffix if necessary.
+ */
+static int ESECT
+mdb_fname_init(const char *path, unsigned envflags, MDB_name *fname)
+{
+	int no_suffix = F_ISSET(envflags, MDB_NOSUBDIR|MDB_NOLOCK);
+	fname->mn_alloced = 0;
+#ifdef _WIN32
+	return utf8_to_utf16(path, fname, no_suffix ? 0 : MDB_SUFFLEN);
+#else
+	fname->mn_len = strlen(path);
+	if (no_suffix)
+		fname->mn_val = (char *) path;
+	else if ((fname->mn_val = malloc(fname->mn_len + MDB_SUFFLEN+1)) != NULL) {
+		fname->mn_alloced = 1;
+		strcpy(fname->mn_val, path);
+	}
+	else
+		return ENOMEM;
+	return MDB_SUCCESS;
+#endif
+}
+
+/** Destroy \b fname from #mdb_fname_init() */
+#define mdb_fname_destroy(fname) \
+	do { if ((fname).mn_alloced) free((fname).mn_val); } while (0)
+
+#ifdef O_CLOEXEC /* POSIX.1-2008: Set FD_CLOEXEC atomically at open() */
+# define MDB_CLOEXEC		O_CLOEXEC
+#else
+# define MDB_CLOEXEC		0
+#endif
+
+/** File type, access mode etc. for #mdb_fopen() */
+enum mdb_fopen_type {
+#ifdef _WIN32
+	MDB_O_RDONLY, MDB_O_RDWR, MDB_O_META, MDB_O_COPY, MDB_O_LOCKS
+#else
+	/* A comment in mdb_fopen() explains some O_* flag choices. */
+	MDB_O_RDONLY= O_RDONLY,                            /**< for RDONLY me_fd */
+	MDB_O_RDWR  = O_RDWR  |O_CREAT,                    /**< for me_fd */
+	MDB_O_META  = O_WRONLY|MDB_DSYNC     |MDB_CLOEXEC, /**< for me_mfd */
+	MDB_O_COPY  = O_WRONLY|O_CREAT|O_EXCL|MDB_CLOEXEC, /**< for #mdb_env_copy() */
+	/** Bitmask for open() flags in enum #mdb_fopen_type.  The other bits
+	 * distinguish otherwise-equal MDB_O_* constants from each other.
+	 */
+	MDB_O_MASK  = MDB_O_RDWR|MDB_CLOEXEC | MDB_O_RDONLY|MDB_O_META|MDB_O_COPY,
+	MDB_O_LOCKS = MDB_O_RDWR|MDB_CLOEXEC | ((MDB_O_MASK+1) & ~MDB_O_MASK) /**< for me_lfd */
+#endif
+};
+
+/** Open an LMDB file.
+ * @param[in] env	The LMDB environment.
+ * @param[in,out] fname	Path from from #mdb_fname_init().  A suffix is
+ * appended if necessary to create the filename, without changing mn_len.
+ * @param[in] which	Determines file type, access mode, etc.
+ * @param[in] mode	The Unix permissions for the file, if we create it.
+ * @param[out] res	Resulting file handle.
+ * @return 0 on success, non-zero on failure.
+ */
+static int ESECT
+mdb_fopen(const MDB_env *env, MDB_name *fname,
+	enum mdb_fopen_type which, mdb_mode_t mode,
+	HANDLE *res)
+{
+	int rc = MDB_SUCCESS;
+	HANDLE fd;
+#ifdef _WIN32
+	DWORD acc, share, disp, attrs;
+#else
+	int flags;
+#endif
+
+	if (fname->mn_alloced)		/* modifiable copy */
+		mdb_name_cpy(fname->mn_val + fname->mn_len,
+			mdb_suffixes[which==MDB_O_LOCKS][F_ISSET(env->me_flags, MDB_NOSUBDIR)]);
+
+	/* The directory must already exist.  Usually the file need not.
+	 * MDB_O_META requires the file because we already created it using
+	 * MDB_O_RDWR.  MDB_O_COPY must not overwrite an existing file.
+	 *
+	 * With MDB_O_COPY we do not want the OS to cache the writes, since
+	 * the source data is already in the OS cache.
+	 *
+	 * The lockfile needs FD_CLOEXEC (close file descriptor on exec*())
+	 * to avoid the flock() issues noted under Caveats in lmdb.h.
+	 * Also set it for other filehandles which the user cannot get at
+	 * and close himself, which he may need after fork().  I.e. all but
+	 * me_fd, which programs do use via mdb_env_get_fd().
+	 */
+
+#ifdef _WIN32
+	acc = GENERIC_READ|GENERIC_WRITE;
+	share = FILE_SHARE_READ|FILE_SHARE_WRITE;
+	disp = OPEN_ALWAYS;
+	attrs = FILE_ATTRIBUTE_NORMAL;
+	switch (which) {
+	case MDB_O_RDONLY:			/* read-only datafile */
+		acc = GENERIC_READ;
+		disp = OPEN_EXISTING;
+		break;
+	case MDB_O_META:			/* for writing metapages */
+		acc = GENERIC_WRITE;
+		disp = OPEN_EXISTING;
+		attrs = FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH;
+		break;
+	case MDB_O_COPY:			/* mdb_env_copy() & co */
+		acc = GENERIC_WRITE;
+		share = 0;
+		disp = CREATE_NEW;
+		attrs = FILE_FLAG_NO_BUFFERING|FILE_FLAG_WRITE_THROUGH;
+		break;
+	default: break;	/* silence gcc -Wswitch (not all enum values handled) */
+	}
+	fd = CreateFileW(fname->mn_val, acc, share, NULL, disp, attrs, NULL);
+#else
+	fd = open(fname->mn_val, which & MDB_O_MASK, mode);
+#endif
+
+	if (fd == INVALID_HANDLE_VALUE)
+		rc = ErrCode();
+#ifndef _WIN32
+	else {
+		if (which != MDB_O_RDONLY && which != MDB_O_RDWR) {
+			/* Set CLOEXEC if we could not pass it to open() */
+			if (!MDB_CLOEXEC && (flags = fcntl(fd, F_GETFD)) != -1)
+				(void) fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
+		}
+		if (which == MDB_O_COPY && env->me_psize >= env->me_os_psize) {
+			/* This may require buffer alignment.  There is no portable
+			 * way to ask how much, so we require OS pagesize alignment.
+			 */
+# ifdef F_NOCACHE	/* __APPLE__ */
+			(void) fcntl(fd, F_NOCACHE, 1);
+# elif defined O_DIRECT
+			/* open(...O_DIRECT...) would break on filesystems without
+			 * O_DIRECT support (ITS#7682). Try to set it here instead.
+			 */
+			if ((flags = fcntl(fd, F_GETFL)) != -1)
+				(void) fcntl(fd, F_SETFL, flags | O_DIRECT);
+# endif
+		}
+	}
+#endif	/* !_WIN32 */
+
+	*res = fd;
+	return rc;
+}
+
+
+#ifdef BROKEN_FDATASYNC
+#include <sys/utsname.h>
+#include <sys/vfs.h>
+#endif
+
+/** Further setup required for opening an LMDB environment
+ */
+static int ESECT
+mdb_env_open2(MDB_env *env)
+{
+	unsigned int flags = env->me_flags;
+	int i, newenv = 0, rc;
+	MDB_meta meta;
+
+#ifdef _WIN32
+	/* See if we should use QueryLimited */
+	rc = GetVersion();
+	if ((rc & 0xff) > 5)
+		env->me_pidquery = MDB_PROCESS_QUERY_LIMITED_INFORMATION;
+	else
+		env->me_pidquery = PROCESS_QUERY_INFORMATION;
+#endif /* _WIN32 */
+
+#ifdef BROKEN_FDATASYNC
+	/* ext3/ext4 fdatasync is broken on some older Linux kernels.
+	 * https://lkml.org/lkml/2012/9/3/83
+	 * Kernels after 3.6-rc6 are known good.
+	 * https://lkml.org/lkml/2012/9/10/556
+	 * See if the DB is on ext3/ext4, then check for new enough kernel
+	 * Kernels 2.6.32.60, 2.6.34.15, 3.2.30, and 3.5.4 are also known
+	 * to be patched.
+	 */
+	{
+		struct statfs st;
+		fstatfs(env->me_fd, &st);
+		while (st.f_type == 0xEF53) {
+			struct utsname uts;
+			int i;
+			uname(&uts);
+			if (uts.release[0] < '3') {
+				if (!strncmp(uts.release, "2.6.32.", 7)) {
+					i = atoi(uts.release+7);
+					if (i >= 60)
+						break;	/* 2.6.32.60 and newer is OK */
+				} else if (!strncmp(uts.release, "2.6.34.", 7)) {
+					i = atoi(uts.release+7);
+					if (i >= 15)
+						break;	/* 2.6.34.15 and newer is OK */
+				}
+			} else if (uts.release[0] == '3') {
+				i = atoi(uts.release+2);
+				if (i > 5)
+					break;	/* 3.6 and newer is OK */
+				if (i == 5) {
+					i = atoi(uts.release+4);
+					if (i >= 4)
+						break;	/* 3.5.4 and newer is OK */
+				} else if (i == 2) {
+					i = atoi(uts.release+4);
+					if (i >= 30)
+						break;	/* 3.2.30 and newer is OK */
+				}
+			} else {	/* 4.x and newer is OK */
+				break;
+			}
+			env->me_flags |= MDB_FSYNCONLY;
+			break;
+		}
+	}
+#endif
+
+	if ((i = mdb_env_read_header(env, &meta)) != 0) {
+		if (i != ENOENT)
+			return i;
+		DPUTS("new mdbenv");
+		newenv = 1;
+		env->me_psize = env->me_os_psize;
+		if (env->me_psize > MAX_PAGESIZE)
+			env->me_psize = MAX_PAGESIZE;
+		memset(&meta, 0, sizeof(meta));
+		mdb_env_init_meta0(env, &meta);
+		meta.mm_mapsize = DEFAULT_MAPSIZE;
+	} else {
+		env->me_psize = meta.mm_psize;
+	}
+
+	/* Was a mapsize configured? */
+	if (!env->me_mapsize) {
+		env->me_mapsize = meta.mm_mapsize;
+	}
+	{
+		/* Make sure mapsize >= committed data size.  Even when using
+		 * mm_mapsize, which could be broken in old files (ITS#7789).
+		 */
+		size_t minsize = (meta.mm_last_pg + 1) * meta.mm_psize;
+		if (env->me_mapsize < minsize)
+			env->me_mapsize = minsize;
+	}
+	meta.mm_mapsize = env->me_mapsize;
+
+	if (newenv && !(flags & MDB_FIXEDMAP)) {
+		/* mdb_env_map() may grow the datafile.  Write the metapages
+		 * first, so the file will be valid if initialization fails.
+		 * Except with FIXEDMAP, since we do not yet know mm_address.
+		 * We could fill in mm_address later, but then a different
+		 * program might end up doing that - one with a memory layout
+		 * and map address which does not suit the main program.
+		 */
+		rc = mdb_env_init_meta(env, &meta);
+		if (rc)
+			return rc;
+		newenv = 0;
+	}
+
+	rc = mdb_env_map(env, (flags & MDB_FIXEDMAP) ? meta.mm_address : NULL);
+	if (rc)
+		return rc;
+
+	if (newenv) {
+		if (flags & MDB_FIXEDMAP)
+			meta.mm_address = env->me_map;
+		i = mdb_env_init_meta(env, &meta);
+		if (i != MDB_SUCCESS) {
+			return i;
+		}
+	}
+
+	env->me_maxfree_1pg = (env->me_psize - PAGEHDRSZ) / sizeof(pgno_t) - 1;
+	env->me_nodemax = (((env->me_psize - PAGEHDRSZ) / MDB_MINKEYS) & -2)
+		- sizeof(indx_t);
+#if !(MDB_MAXKEYSIZE)
+	env->me_maxkey = env->me_nodemax - (NODESIZE + sizeof(MDB_db));
+#endif
+	env->me_maxpg = env->me_mapsize / env->me_psize;
+
+#if MDB_DEBUG
+	{
+		MDB_meta *meta = mdb_env_pick_meta(env);
+		MDB_db *db = &meta->mm_dbs[MAIN_DBI];
+
+		DPRINTF(("opened database version %u, pagesize %u",
+			meta->mm_version, env->me_psize));
+		DPRINTF(("using meta page %d",    (int) (meta->mm_txnid & 1)));
+		DPRINTF(("depth: %u",             db->md_depth));
+		DPRINTF(("entries: %"Z"u",        db->md_entries));
+		DPRINTF(("branch pages: %"Z"u",   db->md_branch_pages));
+		DPRINTF(("leaf pages: %"Z"u",     db->md_leaf_pages));
+		DPRINTF(("overflow pages: %"Z"u", db->md_overflow_pages));
+		DPRINTF(("root: %"Z"u",           db->md_root));
+	}
+#endif
+
+	return MDB_SUCCESS;
+}
+
+
+/** Release a reader thread's slot in the reader lock table.
+ *	This function is called automatically when a thread exits.
+ * @param[in] ptr This points to the slot in the reader lock table.
+ */
+static void
+mdb_env_reader_dest(void *ptr)
+{
+	MDB_reader *reader = ptr;
+
+#ifndef _WIN32
+	if (reader->mr_pid == getpid()) /* catch pthread_exit() in child process */
+#endif
+		/* We omit the mutex, so do this atomically (i.e. skip mr_txnid) */
+		reader->mr_pid = 0;
+}
+
+#ifdef _WIN32
+/** Junk for arranging thread-specific callbacks on Windows. This is
+ *	necessarily platform and compiler-specific. Windows supports up
+ *	to 1088 keys. Let's assume nobody opens more than 64 environments
+ *	in a single process, for now. They can override this if needed.
+ */
+#ifndef MAX_TLS_KEYS
+#define MAX_TLS_KEYS	64
+#endif
+static pthread_key_t mdb_tls_keys[MAX_TLS_KEYS];
+static int mdb_tls_nkeys;
+
+static void NTAPI mdb_tls_callback(PVOID module, DWORD reason, PVOID ptr)
+{
+	int i;
+	switch(reason) {
+	case DLL_PROCESS_ATTACH: break;
+	case DLL_THREAD_ATTACH: break;
+	case DLL_THREAD_DETACH:
+		for (i=0; i<mdb_tls_nkeys; i++) {
+			MDB_reader *r = pthread_getspecific(mdb_tls_keys[i]);
+			if (r) {
+				mdb_env_reader_dest(r);
+			}
+		}
+		break;
+	case DLL_PROCESS_DETACH: break;
+	}
+}
+#ifdef __GNUC__
+#ifdef _WIN64
+const PIMAGE_TLS_CALLBACK mdb_tls_cbp __attribute__((section (".CRT$XLB"))) = mdb_tls_callback;
+#else
+PIMAGE_TLS_CALLBACK mdb_tls_cbp __attribute__((section (".CRT$XLB"))) = mdb_tls_callback;
+#endif
+#else
+#ifdef _WIN64
+/* Force some symbol references.
+ *	_tls_used forces the linker to create the TLS directory if not already done
+ *	mdb_tls_cbp prevents whole-program-optimizer from dropping the symbol.
+ */
+#pragma comment(linker, "/INCLUDE:_tls_used")
+#pragma comment(linker, "/INCLUDE:mdb_tls_cbp")
+#pragma const_seg(".CRT$XLB")
+extern const PIMAGE_TLS_CALLBACK mdb_tls_cbp;
+const PIMAGE_TLS_CALLBACK mdb_tls_cbp = mdb_tls_callback;
+#pragma const_seg()
+#else	/* _WIN32 */
+#pragma comment(linker, "/INCLUDE:__tls_used")
+#pragma comment(linker, "/INCLUDE:_mdb_tls_cbp")
+#pragma data_seg(".CRT$XLB")
+PIMAGE_TLS_CALLBACK mdb_tls_cbp = mdb_tls_callback;
+#pragma data_seg()
+#endif	/* WIN 32/64 */
+#endif	/* !__GNUC__ */
+#endif
+
+/** Downgrade the exclusive lock on the region back to shared */
+static int ESECT
+mdb_env_share_locks(MDB_env *env, int *excl)
+{
+	int rc = 0;
+	MDB_meta *meta = mdb_env_pick_meta(env);
+
+	env->me_txns->mti_txnid = meta->mm_txnid;
+
+#ifdef _WIN32
+	{
+		OVERLAPPED ov;
+		/* First acquire a shared lock. The Unlock will
+		 * then release the existing exclusive lock.
+		 */
+		memset(&ov, 0, sizeof(ov));
+		if (!LockFileEx(env->me_lfd, 0, 0, 1, 0, &ov)) {
+			rc = ErrCode();
+		} else {
+			UnlockFile(env->me_lfd, 0, 0, 1, 0);
+			*excl = 0;
+		}
+	}
+#else
+	{
+		struct flock lock_info;
+		/* The shared lock replaces the existing lock */
+		memset((void *)&lock_info, 0, sizeof(lock_info));
+		lock_info.l_type = F_RDLCK;
+		lock_info.l_whence = SEEK_SET;
+		lock_info.l_start = 0;
+		lock_info.l_len = 1;
+		while ((rc = fcntl(env->me_lfd, F_SETLK, &lock_info)) &&
+				(rc = ErrCode()) == EINTR) ;
+		*excl = rc ? -1 : 0;	/* error may mean we lost the lock */
+	}
+#endif
+
+	return rc;
+}
+
+/** Try to get exclusive lock, otherwise shared.
+ *	Maintain *excl = -1: no/unknown lock, 0: shared, 1: exclusive.
+ */
+static int ESECT
+mdb_env_excl_lock(MDB_env *env, int *excl)
+{
+	int rc = 0;
+#ifdef _WIN32
+	if (LockFile(env->me_lfd, 0, 0, 1, 0)) {
+		*excl = 1;
+	} else {
+		OVERLAPPED ov;
+		memset(&ov, 0, sizeof(ov));
+		if (LockFileEx(env->me_lfd, 0, 0, 1, 0, &ov)) {
+			*excl = 0;
+		} else {
+			rc = ErrCode();
+		}
+	}
+#else
+	struct flock lock_info;
+	memset((void *)&lock_info, 0, sizeof(lock_info));
+	lock_info.l_type = F_WRLCK;
+	lock_info.l_whence = SEEK_SET;
+	lock_info.l_start = 0;
+	lock_info.l_len = 1;
+	while ((rc = fcntl(env->me_lfd, F_SETLK, &lock_info)) &&
+			(rc = ErrCode()) == EINTR) ;
+	if (!rc) {
+		*excl = 1;
+	} else
+# ifndef MDB_USE_POSIX_MUTEX
+	if (*excl < 0) /* always true when MDB_USE_POSIX_MUTEX */
+# endif
+	{
+		lock_info.l_type = F_RDLCK;
+		while ((rc = fcntl(env->me_lfd, F_SETLKW, &lock_info)) &&
+				(rc = ErrCode()) == EINTR) ;
+		if (rc == 0)
+			*excl = 0;
+	}
+#endif
+	return rc;
+}
+
+#ifdef MDB_USE_HASH
+/*
+ * hash_64 - 64 bit Fowler/Noll/Vo-0 FNV-1a hash code
+ *
+ * @(#) $Revision: 5.1 $
+ * @(#) $Id: hash_64a.c,v 5.1 2009/06/30 09:01:38 chongo Exp $
+ * @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_64a.c,v $
+ *
+ *	  http://www.isthe.com/chongo/tech/comp/fnv/index.html
+ *
+ ***
+ *
+ * Please do not copyright this code.  This code is in the public domain.
+ *
+ * LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
+ * EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
+ * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ *
+ * By:
+ *	chongo <Landon Curt Noll> /\oo/\
+ *	  http://www.isthe.com/chongo/
+ *
+ * Share and Enjoy!	:-)
+ */
+
+typedef unsigned long long	mdb_hash_t;
+#define MDB_HASH_INIT ((mdb_hash_t)0xcbf29ce484222325ULL)
+
+/** perform a 64 bit Fowler/Noll/Vo FNV-1a hash on a buffer
+ * @param[in] val	value to hash
+ * @param[in] hval	initial value for hash
+ * @return 64 bit hash
+ *
+ * NOTE: To use the recommended 64 bit FNV-1a hash, use MDB_HASH_INIT as the
+ * 	 hval arg on the first call.
+ */
+static mdb_hash_t
+mdb_hash_val(MDB_val *val, mdb_hash_t hval)
+{
+	unsigned char *s = (unsigned char *)val->mv_data;	/* unsigned string */
+	unsigned char *end = s + val->mv_size;
+	/*
+	 * FNV-1a hash each octet of the string
+	 */
+	while (s < end) {
+		/* xor the bottom with the current octet */
+		hval ^= (mdb_hash_t)*s++;
+
+		/* multiply by the 64 bit FNV magic prime mod 2^64 */
+		hval += (hval << 1) + (hval << 4) + (hval << 5) +
+			(hval << 7) + (hval << 8) + (hval << 40);
+	}
+	/* return our new hash value */
+	return hval;
+}
+
+/** Hash the string and output the encoded hash.
+ * This uses modified RFC1924 Ascii85 encoding to accommodate systems with
+ * very short name limits. We don't care about the encoding being reversible,
+ * we just want to preserve as many bits of the input as possible in a
+ * small printable string.
+ * @param[in] str string to hash
+ * @param[out] encbuf an array of 11 chars to hold the hash
+ */
+static const char mdb_a85[]= "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~";
+
+static void ESECT
+mdb_pack85(unsigned long l, char *out)
+{
+	int i;
+
+	for (i=0; i<5; i++) {
+		*out++ = mdb_a85[l % 85];
+		l /= 85;
+	}
+}
+
+static void ESECT
+mdb_hash_enc(MDB_val *val, char *encbuf)
+{
+	mdb_hash_t h = mdb_hash_val(val, MDB_HASH_INIT);
+
+	mdb_pack85(h, encbuf);
+	mdb_pack85(h>>32, encbuf+5);
+	encbuf[10] = '\0';
+}
+#endif
+
+/** Open and/or initialize the lock region for the environment.
+ * @param[in] env The LMDB environment.
+ * @param[in] fname Filename + scratch area, from #mdb_fname_init().
+ * @param[in] mode The Unix permissions for the file, if we create it.
+ * @param[in,out] excl In -1, out lock type: -1 none, 0 shared, 1 exclusive
+ * @return 0 on success, non-zero on failure.
+ */
+static int ESECT
+mdb_env_setup_locks(MDB_env *env, MDB_name *fname, int mode, int *excl)
+{
+#ifdef _WIN32
+#	define MDB_ERRCODE_ROFS	ERROR_WRITE_PROTECT
+#else
+#	define MDB_ERRCODE_ROFS	EROFS
+#endif
+	int rc;
+	off_t size, rsize;
+
+	rc = mdb_fopen(env, fname, MDB_O_LOCKS, mode, &env->me_lfd);
+	if (rc) {
+		/* Omit lockfile if read-only env on read-only filesystem */
+		if (rc == MDB_ERRCODE_ROFS && (env->me_flags & MDB_RDONLY)) {
+			return MDB_SUCCESS;
+		}
+		goto fail;
+	}
+
+	if (!(env->me_flags & MDB_NOTLS)) {
+		rc = pthread_key_create(&env->me_txkey, mdb_env_reader_dest);
+		if (rc)
+			goto fail;
+		env->me_flags |= MDB_ENV_TXKEY;
+#ifdef _WIN32
+		/* Windows TLS callbacks need help finding their TLS info. */
+		if (mdb_tls_nkeys >= MAX_TLS_KEYS) {
+			rc = MDB_TLS_FULL;
+			goto fail;
+		}
+		mdb_tls_keys[mdb_tls_nkeys++] = env->me_txkey;
+#endif
+	}
+
+	/* Try to get exclusive lock. If we succeed, then
+	 * nobody is using the lock region and we should initialize it.
+	 */
+	if ((rc = mdb_env_excl_lock(env, excl))) goto fail;
+
+#ifdef _WIN32
+	size = GetFileSize(env->me_lfd, NULL);
+#else
+	size = lseek(env->me_lfd, 0, SEEK_END);
+	if (size == -1) goto fail_errno;
+#endif
+	rsize = (env->me_maxreaders-1) * sizeof(MDB_reader) + sizeof(MDB_txninfo);
+	if (size < rsize && *excl > 0) {
+#ifdef _WIN32
+		if (SetFilePointer(env->me_lfd, rsize, NULL, FILE_BEGIN) != (DWORD)rsize
+			|| !SetEndOfFile(env->me_lfd))
+			goto fail_errno;
+#else
+		if (ftruncate(env->me_lfd, rsize) != 0) goto fail_errno;
+#endif
+	} else {
+		rsize = size;
+		size = rsize - sizeof(MDB_txninfo);
+		env->me_maxreaders = size/sizeof(MDB_reader) + 1;
+	}
+	{
+#ifdef _WIN32
+		HANDLE mh;
+		mh = CreateFileMapping(env->me_lfd, NULL, PAGE_READWRITE,
+			0, 0, NULL);
+		if (!mh) goto fail_errno;
+		env->me_txns = MapViewOfFileEx(mh, FILE_MAP_WRITE, 0, 0, rsize, NULL);
+		CloseHandle(mh);
+		if (!env->me_txns) goto fail_errno;
+#else
+		void *m = mmap(NULL, rsize, PROT_READ|PROT_WRITE, MAP_SHARED,
+			env->me_lfd, 0);
+		if (m == MAP_FAILED) goto fail_errno;
+		env->me_txns = m;
+#endif
+	}
+	if (*excl > 0) {
+#ifdef _WIN32
+		BY_HANDLE_FILE_INFORMATION stbuf;
+		struct {
+			DWORD volume;
+			DWORD nhigh;
+			DWORD nlow;
+		} idbuf;
+		MDB_val val;
+		char encbuf[11];
+
+		if (!mdb_sec_inited) {
+			InitializeSecurityDescriptor(&mdb_null_sd,
+				SECURITY_DESCRIPTOR_REVISION);
+			SetSecurityDescriptorDacl(&mdb_null_sd, TRUE, 0, FALSE);
+			mdb_all_sa.nLength = sizeof(SECURITY_ATTRIBUTES);
+			mdb_all_sa.bInheritHandle = FALSE;
+			mdb_all_sa.lpSecurityDescriptor = &mdb_null_sd;
+			mdb_sec_inited = 1;
+		}
+		if (!GetFileInformationByHandle(env->me_lfd, &stbuf)) goto fail_errno;
+		idbuf.volume = stbuf.dwVolumeSerialNumber;
+		idbuf.nhigh  = stbuf.nFileIndexHigh;
+		idbuf.nlow   = stbuf.nFileIndexLow;
+		val.mv_data = &idbuf;
+		val.mv_size = sizeof(idbuf);
+		mdb_hash_enc(&val, encbuf);
+		sprintf(env->me_txns->mti_rmname, "Global\\MDBr%s", encbuf);
+		sprintf(env->me_txns->mti_wmname, "Global\\MDBw%s", encbuf);
+		env->me_rmutex = CreateMutexA(&mdb_all_sa, FALSE, env->me_txns->mti_rmname);
+		if (!env->me_rmutex) goto fail_errno;
+		env->me_wmutex = CreateMutexA(&mdb_all_sa, FALSE, env->me_txns->mti_wmname);
+		if (!env->me_wmutex) goto fail_errno;
+#elif defined(MDB_USE_POSIX_SEM)
+		struct stat stbuf;
+		struct {
+			dev_t dev;
+			ino_t ino;
+		} idbuf;
+		MDB_val val;
+		char encbuf[11];
+
+#if defined(__NetBSD__)
+#define	MDB_SHORT_SEMNAMES	1	/* limited to 14 chars */
+#endif
+		if (fstat(env->me_lfd, &stbuf)) goto fail_errno;
+		idbuf.dev = stbuf.st_dev;
+		idbuf.ino = stbuf.st_ino;
+		val.mv_data = &idbuf;
+		val.mv_size = sizeof(idbuf);
+		mdb_hash_enc(&val, encbuf);
+#ifdef MDB_SHORT_SEMNAMES
+		encbuf[9] = '\0';	/* drop name from 15 chars to 14 chars */
+#endif
+		sprintf(env->me_txns->mti_rmname, "/MDBr%s", encbuf);
+		sprintf(env->me_txns->mti_wmname, "/MDBw%s", encbuf);
+		/* Clean up after a previous run, if needed:  Try to
+		 * remove both semaphores before doing anything else.
+		 */
+		sem_unlink(env->me_txns->mti_rmname);
+		sem_unlink(env->me_txns->mti_wmname);
+		env->me_rmutex = sem_open(env->me_txns->mti_rmname,
+			O_CREAT|O_EXCL, mode, 1);
+		if (env->me_rmutex == SEM_FAILED) goto fail_errno;
+		env->me_wmutex = sem_open(env->me_txns->mti_wmname,
+			O_CREAT|O_EXCL, mode, 1);
+		if (env->me_wmutex == SEM_FAILED) goto fail_errno;
+#else	/* MDB_USE_POSIX_MUTEX: */
+		pthread_mutexattr_t mattr;
+
+		/* Solaris needs this before initing a robust mutex.  Otherwise
+		 * it may skip the init and return EBUSY "seems someone already
+		 * inited" or EINVAL "it was inited differently".
+		 */
+		memset(env->me_txns->mti_rmutex, 0, sizeof(*env->me_txns->mti_rmutex));
+		memset(env->me_txns->mti_wmutex, 0, sizeof(*env->me_txns->mti_wmutex));
+
+		if ((rc = pthread_mutexattr_init(&mattr)))
+			goto fail;
+
+		rc = pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
+#ifdef MDB_ROBUST_SUPPORTED
+		if (!rc) rc = pthread_mutexattr_setrobust(&mattr, PTHREAD_MUTEX_ROBUST);
+#endif
+		if (!rc) rc = pthread_mutex_init(env->me_txns->mti_rmutex, &mattr);
+		if (!rc) rc = pthread_mutex_init(env->me_txns->mti_wmutex, &mattr);
+		pthread_mutexattr_destroy(&mattr);
+		if (rc)
+			goto fail;
+#endif	/* _WIN32 || MDB_USE_POSIX_SEM */
+
+		env->me_txns->mti_magic = MDB_MAGIC;
+		env->me_txns->mti_format = MDB_LOCK_FORMAT;
+		env->me_txns->mti_txnid = 0;
+		env->me_txns->mti_numreaders = 0;
+
+	} else {
+		if (env->me_txns->mti_magic != MDB_MAGIC) {
+			DPUTS("lock region has invalid magic");
+			rc = MDB_INVALID;
+			goto fail;
+		}
+		if (env->me_txns->mti_format != MDB_LOCK_FORMAT) {
+			DPRINTF(("lock region has format+version 0x%x, expected 0x%x",
+				env->me_txns->mti_format, MDB_LOCK_FORMAT));
+			rc = MDB_VERSION_MISMATCH;
+			goto fail;
+		}
+		rc = ErrCode();
+		if (rc && rc != EACCES && rc != EAGAIN) {
+			goto fail;
+		}
+#ifdef _WIN32
+		env->me_rmutex = OpenMutexA(SYNCHRONIZE, FALSE, env->me_txns->mti_rmname);
+		if (!env->me_rmutex) goto fail_errno;
+		env->me_wmutex = OpenMutexA(SYNCHRONIZE, FALSE, env->me_txns->mti_wmname);
+		if (!env->me_wmutex) goto fail_errno;
+#elif defined(MDB_USE_POSIX_SEM)
+		env->me_rmutex = sem_open(env->me_txns->mti_rmname, 0);
+		if (env->me_rmutex == SEM_FAILED) goto fail_errno;
+		env->me_wmutex = sem_open(env->me_txns->mti_wmname, 0);
+		if (env->me_wmutex == SEM_FAILED) goto fail_errno;
+#endif
+	}
+	return MDB_SUCCESS;
+
+fail_errno:
+	rc = ErrCode();
+fail:
+	return rc;
+}
+
+	/** Only a subset of the @ref mdb_env flags can be changed
+	 *	at runtime. Changing other flags requires closing the
+	 *	environment and re-opening it with the new flags.
+	 */
+#define	CHANGEABLE	(MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC|MDB_NOMEMINIT)
+#define	CHANGELESS	(MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY| \
+	MDB_WRITEMAP|MDB_NOTLS|MDB_NOLOCK|MDB_NORDAHEAD)
+
+#if VALID_FLAGS & PERSISTENT_FLAGS & (CHANGEABLE|CHANGELESS)
+# error "Persistent DB flags & env flags overlap, but both go in mm_flags"
+#endif
+
+int ESECT
+mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode)
+{
+	int rc, excl = -1;
+	MDB_name fname;
+
+	if (env->me_fd!=INVALID_HANDLE_VALUE || (flags & ~(CHANGEABLE|CHANGELESS)))
+		return EINVAL;
+
+	flags |= env->me_flags;
+
+	rc = mdb_fname_init(path, flags, &fname);
+	if (rc)
+		return rc;
+
+	if (flags & MDB_RDONLY) {
+		/* silently ignore WRITEMAP when we're only getting read access */
+		flags &= ~MDB_WRITEMAP;
+	} else {
+		if (!((env->me_free_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX)) &&
+			  (env->me_dirty_list = calloc(MDB_IDL_UM_SIZE, sizeof(MDB_ID2)))))
+			rc = ENOMEM;
+	}
+	env->me_flags = flags |= MDB_ENV_ACTIVE;
+	if (rc)
+		goto leave;
+
+	env->me_path = strdup(path);
+	env->me_dbxs = calloc(env->me_maxdbs, sizeof(MDB_dbx));
+	env->me_dbflags = calloc(env->me_maxdbs, sizeof(uint16_t));
+	env->me_dbiseqs = calloc(env->me_maxdbs, sizeof(unsigned int));
+	if (!(env->me_dbxs && env->me_path && env->me_dbflags && env->me_dbiseqs)) {
+		rc = ENOMEM;
+		goto leave;
+	}
+	env->me_dbxs[FREE_DBI].md_cmp = mdb_cmp_long; /* aligned MDB_INTEGERKEY */
+
+	/* For RDONLY, get lockfile after we know datafile exists */
+	if (!(flags & (MDB_RDONLY|MDB_NOLOCK))) {
+		rc = mdb_env_setup_locks(env, &fname, mode, &excl);
+		if (rc)
+			goto leave;
+	}
+
+	rc = mdb_fopen(env, &fname,
+		(flags & MDB_RDONLY) ? MDB_O_RDONLY : MDB_O_RDWR,
+		mode, &env->me_fd);
+	if (rc)
+		goto leave;
+
+	if ((flags & (MDB_RDONLY|MDB_NOLOCK)) == MDB_RDONLY) {
+		rc = mdb_env_setup_locks(env, &fname, mode, &excl);
+		if (rc)
+			goto leave;
+	}
+
+	if ((rc = mdb_env_open2(env)) == MDB_SUCCESS) {
+		if (!(flags & (MDB_RDONLY|MDB_WRITEMAP))) {
+			/* Synchronous fd for meta writes. Needed even with
+			 * MDB_NOSYNC/MDB_NOMETASYNC, in case these get reset.
+			 */
+			rc = mdb_fopen(env, &fname, MDB_O_META, mode, &env->me_mfd);
+			if (rc)
+				goto leave;
+		}
+		DPRINTF(("opened dbenv %p", (void *) env));
+		if (excl > 0) {
+			rc = mdb_env_share_locks(env, &excl);
+			if (rc)
+				goto leave;
+		}
+		if (!(flags & MDB_RDONLY)) {
+			MDB_txn *txn;
+			int tsize = sizeof(MDB_txn), size = tsize + env->me_maxdbs *
+				(sizeof(MDB_db)+sizeof(MDB_cursor *)+sizeof(unsigned int)+1);
+			if ((env->me_pbuf = calloc(1, env->me_psize)) &&
+				(txn = calloc(1, size)))
+			{
+				txn->mt_dbs = (MDB_db *)((char *)txn + tsize);
+				txn->mt_cursors = (MDB_cursor **)(txn->mt_dbs + env->me_maxdbs);
+				txn->mt_dbiseqs = (unsigned int *)(txn->mt_cursors + env->me_maxdbs);
+				txn->mt_dbflags = (unsigned char *)(txn->mt_dbiseqs + env->me_maxdbs);
+				txn->mt_env = env;
+				txn->mt_dbxs = env->me_dbxs;
+				txn->mt_flags = MDB_TXN_FINISHED;
+				env->me_txn0 = txn;
+			} else {
+				rc = ENOMEM;
+			}
+		}
+	}
+
+leave:
+	if (rc) {
+		mdb_env_close0(env, excl);
+	}
+	mdb_fname_destroy(fname);
+	return rc;
+}
+
+/** Destroy resources from mdb_env_open(), clear our readers & DBIs */
+static void ESECT
+mdb_env_close0(MDB_env *env, int excl)
+{
+	int i;
+
+	if (!(env->me_flags & MDB_ENV_ACTIVE))
+		return;
+
+	/* Doing this here since me_dbxs may not exist during mdb_env_close */
+	if (env->me_dbxs) {
+		for (i = env->me_maxdbs; --i >= CORE_DBS; )
+			free(env->me_dbxs[i].md_name.mv_data);
+		free(env->me_dbxs);
+	}
+
+	free(env->me_pbuf);
+	free(env->me_dbiseqs);
+	free(env->me_dbflags);
+	free(env->me_path);
+	free(env->me_dirty_list);
+	free(env->me_txn0);
+	mdb_midl_free(env->me_free_pgs);
+
+	if (env->me_flags & MDB_ENV_TXKEY) {
+		pthread_key_delete(env->me_txkey);
+#ifdef _WIN32
+		/* Delete our key from the global list */
+		for (i=0; i<mdb_tls_nkeys; i++)
+			if (mdb_tls_keys[i] == env->me_txkey) {
+				mdb_tls_keys[i] = mdb_tls_keys[mdb_tls_nkeys-1];
+				mdb_tls_nkeys--;
+				break;
+			}
+#endif
+	}
+
+	if (env->me_map) {
+		munmap(env->me_map, env->me_mapsize);
+	}
+	if (env->me_mfd != INVALID_HANDLE_VALUE)
+		(void) close(env->me_mfd);
+	if (env->me_fd != INVALID_HANDLE_VALUE)
+		(void) close(env->me_fd);
+	if (env->me_txns) {
+		MDB_PID_T pid = env->me_pid;
+		/* Clearing readers is done in this function because
+		 * me_txkey with its destructor must be disabled first.
+		 *
+		 * We skip the the reader mutex, so we touch only
+		 * data owned by this process (me_close_readers and
+		 * our readers), and clear each reader atomically.
+		 */
+		for (i = env->me_close_readers; --i >= 0; )
+			if (env->me_txns->mti_readers[i].mr_pid == pid)
+				env->me_txns->mti_readers[i].mr_pid = 0;
+#ifdef _WIN32
+		if (env->me_rmutex) {
+			CloseHandle(env->me_rmutex);
+			if (env->me_wmutex) CloseHandle(env->me_wmutex);
+		}
+		/* Windows automatically destroys the mutexes when
+		 * the last handle closes.
+		 */
+#elif defined(MDB_USE_POSIX_SEM)
+		if (env->me_rmutex != SEM_FAILED) {
+			sem_close(env->me_rmutex);
+			if (env->me_wmutex != SEM_FAILED)
+				sem_close(env->me_wmutex);
+			/* If we have the filelock:  If we are the
+			 * only remaining user, clean up semaphores.
+			 */
+			if (excl == 0)
+				mdb_env_excl_lock(env, &excl);
+			if (excl > 0) {
+				sem_unlink(env->me_txns->mti_rmname);
+				sem_unlink(env->me_txns->mti_wmname);
+			}
+		}
+#endif
+		munmap((void *)env->me_txns, (env->me_maxreaders-1)*sizeof(MDB_reader)+sizeof(MDB_txninfo));
+	}
+	if (env->me_lfd != INVALID_HANDLE_VALUE) {
+#ifdef _WIN32
+		if (excl >= 0) {
+			/* Unlock the lockfile.  Windows would have unlocked it
+			 * after closing anyway, but not necessarily at once.
+			 */
+			UnlockFile(env->me_lfd, 0, 0, 1, 0);
+		}
+#endif
+		(void) close(env->me_lfd);
+	}
+
+	env->me_flags &= ~(MDB_ENV_ACTIVE|MDB_ENV_TXKEY);
+}
+
+void ESECT
+mdb_env_close(MDB_env *env)
+{
+	MDB_page *dp;
+
+	if (env == NULL)
+		return;
+
+	VGMEMP_DESTROY(env);
+	while ((dp = env->me_dpages) != NULL) {
+		VGMEMP_DEFINED(&dp->mp_next, sizeof(dp->mp_next));
+		env->me_dpages = dp->mp_next;
+		free(dp);
+	}
+
+	mdb_env_close0(env, 0);
+	free(env);
+}
+
+/** Compare two items pointing at aligned size_t's */
+static int
+mdb_cmp_long(const MDB_val *a, const MDB_val *b)
+{
+	return (*(size_t *)a->mv_data < *(size_t *)b->mv_data) ? -1 :
+		*(size_t *)a->mv_data > *(size_t *)b->mv_data;
+}
+
+/** Compare two items pointing at aligned unsigned int's.
+ *
+ *	This is also set as #MDB_INTEGERDUP|#MDB_DUPFIXED's #MDB_dbx.%md_dcmp,
+ *	but #mdb_cmp_clong() is called instead if the data type is size_t.
+ */
+static int
+mdb_cmp_int(const MDB_val *a, const MDB_val *b)
+{
+	return (*(unsigned int *)a->mv_data < *(unsigned int *)b->mv_data) ? -1 :
+		*(unsigned int *)a->mv_data > *(unsigned int *)b->mv_data;
+}
+
+/** Compare two items pointing at unsigned ints of unknown alignment.
+ *	Nodes and keys are guaranteed to be 2-byte aligned.
+ */
+static int
+mdb_cmp_cint(const MDB_val *a, const MDB_val *b)
+{
+#if BYTE_ORDER == LITTLE_ENDIAN
+	unsigned short *u, *c;
+	int x;
+
+	u = (unsigned short *) ((char *) a->mv_data + a->mv_size);
+	c = (unsigned short *) ((char *) b->mv_data + a->mv_size);
+	do {
+		x = *--u - *--c;
+	} while(!x && u > (unsigned short *)a->mv_data);
+	return x;
+#else
+	unsigned short *u, *c, *end;
+	int x;
+
+	end = (unsigned short *) ((char *) a->mv_data + a->mv_size);
+	u = (unsigned short *)a->mv_data;
+	c = (unsigned short *)b->mv_data;
+	do {
+		x = *u++ - *c++;
+	} while(!x && u < end);
+	return x;
+#endif
+}
+
+/** Compare two items lexically */
+static int
+mdb_cmp_memn(const MDB_val *a, const MDB_val *b)
+{
+	int diff;
+	ssize_t len_diff;
+	unsigned int len;
+
+	len = a->mv_size;
+	len_diff = (ssize_t) a->mv_size - (ssize_t) b->mv_size;
+	if (len_diff > 0) {
+		len = b->mv_size;
+		len_diff = 1;
+	}
+
+	diff = memcmp(a->mv_data, b->mv_data, len);
+	return diff ? diff : len_diff<0 ? -1 : len_diff;
+}
+
+/** Compare two items in reverse byte order */
+static int
+mdb_cmp_memnr(const MDB_val *a, const MDB_val *b)
+{
+	const unsigned char	*p1, *p2, *p1_lim;
+	ssize_t len_diff;
+	int diff;
+
+	p1_lim = (const unsigned char *)a->mv_data;
+	p1 = (const unsigned char *)a->mv_data + a->mv_size;
+	p2 = (const unsigned char *)b->mv_data + b->mv_size;
+
+	len_diff = (ssize_t) a->mv_size - (ssize_t) b->mv_size;
+	if (len_diff > 0) {
+		p1_lim += len_diff;
+		len_diff = 1;
+	}
+
+	while (p1 > p1_lim) {
+		diff = *--p1 - *--p2;
+		if (diff)
+			return diff;
+	}
+	return len_diff<0 ? -1 : len_diff;
+}
+
+/** Search for key within a page, using binary search.
+ * Returns the smallest entry larger or equal to the key.
+ * If exactp is non-null, stores whether the found entry was an exact match
+ * in *exactp (1 or 0).
+ * Updates the cursor index with the index of the found entry.
+ * If no entry larger or equal to the key is found, returns NULL.
+ */
+static MDB_node *
+mdb_node_search(MDB_cursor *mc, MDB_val *key, int *exactp)
+{
+	unsigned int	 i = 0, nkeys;
+	int		 low, high;
+	int		 rc = 0;
+	MDB_page *mp = mc->mc_pg[mc->mc_top];
+	MDB_node	*node = NULL;
+	MDB_val	 nodekey;
+	MDB_cmp_func *cmp;
+	DKBUF;
+
+	nkeys = NUMKEYS(mp);
+
+	DPRINTF(("searching %u keys in %s %spage %"Z"u",
+	    nkeys, IS_LEAF(mp) ? "leaf" : "branch", IS_SUBP(mp) ? "sub-" : "",
+	    mdb_dbg_pgno(mp)));
+
+	low = IS_LEAF(mp) ? 0 : 1;
+	high = nkeys - 1;
+	cmp = mc->mc_dbx->md_cmp;
+
+	/* Branch pages have no data, so if using integer keys,
+	 * alignment is guaranteed. Use faster mdb_cmp_int.
+	 */
+	if (cmp == mdb_cmp_cint && IS_BRANCH(mp)) {
+		if (NODEPTR(mp, 1)->mn_ksize == sizeof(size_t))
+			cmp = mdb_cmp_long;
+		else
+			cmp = mdb_cmp_int;
+	}
+
+	if (IS_LEAF2(mp)) {
+		nodekey.mv_size = mc->mc_db->md_pad;
+		node = NODEPTR(mp, 0);	/* fake */
+		while (low <= high) {
+			i = (low + high) >> 1;
+			nodekey.mv_data = LEAF2KEY(mp, i, nodekey.mv_size);
+			rc = cmp(key, &nodekey);
+			DPRINTF(("found leaf index %u [%s], rc = %i",
+			    i, DKEY(&nodekey), rc));
+			if (rc == 0)
+				break;
+			if (rc > 0)
+				low = i + 1;
+			else
+				high = i - 1;
+		}
+	} else {
+		while (low <= high) {
+			i = (low + high) >> 1;
+
+			node = NODEPTR(mp, i);
+			nodekey.mv_size = NODEKSZ(node);
+			nodekey.mv_data = NODEKEY(node);
+
+			rc = cmp(key, &nodekey);
+#if MDB_DEBUG
+			if (IS_LEAF(mp))
+				DPRINTF(("found leaf index %u [%s], rc = %i",
+				    i, DKEY(&nodekey), rc));
+			else
+				DPRINTF(("found branch index %u [%s -> %"Z"u], rc = %i",
+				    i, DKEY(&nodekey), NODEPGNO(node), rc));
+#endif
+			if (rc == 0)
+				break;
+			if (rc > 0)
+				low = i + 1;
+			else
+				high = i - 1;
+		}
+	}
+
+	if (rc > 0) {	/* Found entry is less than the key. */
+		i++;	/* Skip to get the smallest entry larger than key. */
+		if (!IS_LEAF2(mp))
+			node = NODEPTR(mp, i);
+	}
+	if (exactp)
+		*exactp = (rc == 0 && nkeys > 0);
+	/* store the key index */
+	mc->mc_ki[mc->mc_top] = i;
+	if (i >= nkeys)
+		/* There is no entry larger or equal to the key. */
+		return NULL;
+
+	/* nodeptr is fake for LEAF2 */
+	return node;
+}
+
+#if 0
+static void
+mdb_cursor_adjust(MDB_cursor *mc, func)
+{
+	MDB_cursor *m2;
+
+	for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
+		if (m2->mc_pg[m2->mc_top] == mc->mc_pg[mc->mc_top]) {
+			func(mc, m2);
+		}
+	}
+}
+#endif
+
+/** Pop a page off the top of the cursor's stack. */
+static void
+mdb_cursor_pop(MDB_cursor *mc)
+{
+	if (mc->mc_snum) {
+		DPRINTF(("popping page %"Z"u off db %d cursor %p",
+			mc->mc_pg[mc->mc_top]->mp_pgno, DDBI(mc), (void *) mc));
+
+		mc->mc_snum--;
+		if (mc->mc_snum) {
+			mc->mc_top--;
+		} else {
+			mc->mc_flags &= ~C_INITIALIZED;
+		}
+	}
+}
+
+/** Push a page onto the top of the cursor's stack.
+ * Set #MDB_TXN_ERROR on failure.
+ */
+static int
+mdb_cursor_push(MDB_cursor *mc, MDB_page *mp)
+{
+	DPRINTF(("pushing page %"Z"u on db %d cursor %p", mp->mp_pgno,
+		DDBI(mc), (void *) mc));
+
+	if (mc->mc_snum >= CURSOR_STACK) {
+		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+		return MDB_CURSOR_FULL;
+	}
+
+	mc->mc_top = mc->mc_snum++;
+	mc->mc_pg[mc->mc_top] = mp;
+	mc->mc_ki[mc->mc_top] = 0;
+
+	return MDB_SUCCESS;
+}
+
+/** Find the address of the page corresponding to a given page number.
+ * Set #MDB_TXN_ERROR on failure.
+ * @param[in] mc the cursor accessing the page.
+ * @param[in] pgno the page number for the page to retrieve.
+ * @param[out] ret address of a pointer where the page's address will be stored.
+ * @param[out] lvl dirty_list inheritance level of found page. 1=current txn, 0=mapped page.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_get(MDB_cursor *mc, pgno_t pgno, MDB_page **ret, int *lvl)
+{
+	MDB_txn *txn = mc->mc_txn;
+	MDB_env *env = txn->mt_env;
+	MDB_page *p = NULL;
+	int level;
+
+	if (! (txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_WRITEMAP))) {
+		MDB_txn *tx2 = txn;
+		level = 1;
+		do {
+			MDB_ID2L dl = tx2->mt_u.dirty_list;
+			unsigned x;
+			/* Spilled pages were dirtied in this txn and flushed
+			 * because the dirty list got full. Bring this page
+			 * back in from the map (but don't unspill it here,
+			 * leave that unless page_touch happens again).
+			 */
+			if (tx2->mt_spill_pgs) {
+				MDB_ID pn = pgno << 1;
+				x = mdb_midl_search(tx2->mt_spill_pgs, pn);
+				if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pn) {
+					p = (MDB_page *)(env->me_map + env->me_psize * pgno);
+					goto done;
+				}
+			}
+			if (dl[0].mid) {
+				unsigned x = mdb_mid2l_search(dl, pgno);
+				if (x <= dl[0].mid && dl[x].mid == pgno) {
+					p = dl[x].mptr;
+					goto done;
+				}
+			}
+			level++;
+		} while ((tx2 = tx2->mt_parent) != NULL);
+	}
+
+	if (pgno < txn->mt_next_pgno) {
+		level = 0;
+		p = (MDB_page *)(env->me_map + env->me_psize * pgno);
+	} else {
+		DPRINTF(("page %"Z"u not found", pgno));
+		txn->mt_flags |= MDB_TXN_ERROR;
+		return MDB_PAGE_NOTFOUND;
+	}
+
+done:
+	*ret = p;
+	if (lvl)
+		*lvl = level;
+	return MDB_SUCCESS;
+}
+
+/** Finish #mdb_page_search() / #mdb_page_search_lowest().
+ *	The cursor is at the root page, set up the rest of it.
+ */
+static int
+mdb_page_search_root(MDB_cursor *mc, MDB_val *key, int flags)
+{
+	MDB_page	*mp = mc->mc_pg[mc->mc_top];
+	int rc;
+	DKBUF;
+
+	while (IS_BRANCH(mp)) {
+		MDB_node	*node;
+		indx_t		i;
+
+		DPRINTF(("branch page %"Z"u has %u keys", mp->mp_pgno, NUMKEYS(mp)));
+		/* Don't assert on branch pages in the FreeDB. We can get here
+		 * while in the process of rebalancing a FreeDB branch page; we must
+		 * let that proceed. ITS#8336
+		 */
+		mdb_cassert(mc, !mc->mc_dbi || NUMKEYS(mp) > 1);
+		DPRINTF(("found index 0 to page %"Z"u", NODEPGNO(NODEPTR(mp, 0))));
+
+		if (flags & (MDB_PS_FIRST|MDB_PS_LAST)) {
+			i = 0;
+			if (flags & MDB_PS_LAST) {
+				i = NUMKEYS(mp) - 1;
+				/* if already init'd, see if we're already in right place */
+				if (mc->mc_flags & C_INITIALIZED) {
+					if (mc->mc_ki[mc->mc_top] == i) {
+						mc->mc_top = mc->mc_snum++;
+						mp = mc->mc_pg[mc->mc_top];
+						goto ready;
+					}
+				}
+			}
+		} else {
+			int	 exact;
+			node = mdb_node_search(mc, key, &exact);
+			if (node == NULL)
+				i = NUMKEYS(mp) - 1;
+			else {
+				i = mc->mc_ki[mc->mc_top];
+				if (!exact) {
+					mdb_cassert(mc, i > 0);
+					i--;
+				}
+			}
+			DPRINTF(("following index %u for key [%s]", i, DKEY(key)));
+		}
+
+		mdb_cassert(mc, i < NUMKEYS(mp));
+		node = NODEPTR(mp, i);
+
+		if ((rc = mdb_page_get(mc, NODEPGNO(node), &mp, NULL)) != 0)
+			return rc;
+
+		mc->mc_ki[mc->mc_top] = i;
+		if ((rc = mdb_cursor_push(mc, mp)))
+			return rc;
+
+ready:
+		if (flags & MDB_PS_MODIFY) {
+			if ((rc = mdb_page_touch(mc)) != 0)
+				return rc;
+			mp = mc->mc_pg[mc->mc_top];
+		}
+	}
+
+	if (!IS_LEAF(mp)) {
+		DPRINTF(("internal error, index points to a %02X page!?",
+		    mp->mp_flags));
+		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+		return MDB_CORRUPTED;
+	}
+
+	DPRINTF(("found leaf page %"Z"u for key [%s]", mp->mp_pgno,
+	    key ? DKEY(key) : "null"));
+	mc->mc_flags |= C_INITIALIZED;
+	mc->mc_flags &= ~C_EOF;
+
+	return MDB_SUCCESS;
+}
+
+/** Search for the lowest key under the current branch page.
+ * This just bypasses a NUMKEYS check in the current page
+ * before calling mdb_page_search_root(), because the callers
+ * are all in situations where the current page is known to
+ * be underfilled.
+ */
+static int
+mdb_page_search_lowest(MDB_cursor *mc)
+{
+	MDB_page	*mp = mc->mc_pg[mc->mc_top];
+	MDB_node	*node = NODEPTR(mp, 0);
+	int rc;
+
+	if ((rc = mdb_page_get(mc, NODEPGNO(node), &mp, NULL)) != 0)
+		return rc;
+
+	mc->mc_ki[mc->mc_top] = 0;
+	if ((rc = mdb_cursor_push(mc, mp)))
+		return rc;
+	return mdb_page_search_root(mc, NULL, MDB_PS_FIRST);
+}
+
+/** Search for the page a given key should be in.
+ * Push it and its parent pages on the cursor stack.
+ * @param[in,out] mc the cursor for this operation.
+ * @param[in] key the key to search for, or NULL for first/last page.
+ * @param[in] flags If MDB_PS_MODIFY is set, visited pages in the DB
+ *   are touched (updated with new page numbers).
+ *   If MDB_PS_FIRST or MDB_PS_LAST is set, find first or last leaf.
+ *   This is used by #mdb_cursor_first() and #mdb_cursor_last().
+ *   If MDB_PS_ROOTONLY set, just fetch root node, no further lookups.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_search(MDB_cursor *mc, MDB_val *key, int flags)
+{
+	int		 rc;
+	pgno_t		 root;
+
+	/* Make sure the txn is still viable, then find the root from
+	 * the txn's db table and set it as the root of the cursor's stack.
+	 */
+	if (mc->mc_txn->mt_flags & MDB_TXN_BLOCKED) {
+		DPUTS("transaction may not be used now");
+		return MDB_BAD_TXN;
+	} else {
+		/* Make sure we're using an up-to-date root */
+		if (*mc->mc_dbflag & DB_STALE) {
+				MDB_cursor mc2;
+				if (TXN_DBI_CHANGED(mc->mc_txn, mc->mc_dbi))
+					return MDB_BAD_DBI;
+				mdb_cursor_init(&mc2, mc->mc_txn, MAIN_DBI, NULL);
+				rc = mdb_page_search(&mc2, &mc->mc_dbx->md_name, 0);
+				if (rc)
+					return rc;
+				{
+					MDB_val data;
+					int exact = 0;
+					uint16_t flags;
+					MDB_node *leaf = mdb_node_search(&mc2,
+						&mc->mc_dbx->md_name, &exact);
+					if (!exact)
+						return MDB_NOTFOUND;
+					if ((leaf->mn_flags & (F_DUPDATA|F_SUBDATA)) != F_SUBDATA)
+						return MDB_INCOMPATIBLE; /* not a named DB */
+					rc = mdb_node_read(&mc2, leaf, &data);
+					if (rc)
+						return rc;
+					memcpy(&flags, ((char *) data.mv_data + offsetof(MDB_db, md_flags)),
+						sizeof(uint16_t));
+					/* The txn may not know this DBI, or another process may
+					 * have dropped and recreated the DB with other flags.
+					 */
+					if ((mc->mc_db->md_flags & PERSISTENT_FLAGS) != flags)
+						return MDB_INCOMPATIBLE;
+					memcpy(mc->mc_db, data.mv_data, sizeof(MDB_db));
+				}
+				*mc->mc_dbflag &= ~DB_STALE;
+		}
+		root = mc->mc_db->md_root;
+
+		if (root == P_INVALID) {		/* Tree is empty. */
+			DPUTS("tree is empty");
+			return MDB_NOTFOUND;
+		}
+	}
+
+	mdb_cassert(mc, root > 1);
+	if (!mc->mc_pg[0] || mc->mc_pg[0]->mp_pgno != root)
+		if ((rc = mdb_page_get(mc, root, &mc->mc_pg[0], NULL)) != 0)
+			return rc;
+
+	mc->mc_snum = 1;
+	mc->mc_top = 0;
+
+	DPRINTF(("db %d root page %"Z"u has flags 0x%X",
+		DDBI(mc), root, mc->mc_pg[0]->mp_flags));
+
+	if (flags & MDB_PS_MODIFY) {
+		if ((rc = mdb_page_touch(mc)))
+			return rc;
+	}
+
+	if (flags & MDB_PS_ROOTONLY)
+		return MDB_SUCCESS;
+
+	return mdb_page_search_root(mc, key, flags);
+}
+
+static int
+mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
+{
+	MDB_txn *txn = mc->mc_txn;
+	pgno_t pg = mp->mp_pgno;
+	unsigned x = 0, ovpages = mp->mp_pages;
+	MDB_env *env = txn->mt_env;
+	MDB_IDL sl = txn->mt_spill_pgs;
+	MDB_ID pn = pg << 1;
+	int rc;
+
+	DPRINTF(("free ov page %"Z"u (%d)", pg, ovpages));
+	/* If the page is dirty or on the spill list we just acquired it,
+	 * so we should give it back to our current free list, if any.
+	 * Otherwise put it onto the list of pages we freed in this txn.
+	 *
+	 * Won't create me_pghead: me_pglast must be inited along with it.
+	 * Unsupported in nested txns: They would need to hide the page
+	 * range in ancestor txns' dirty and spilled lists.
+	 */
+	if (env->me_pghead &&
+		!txn->mt_parent &&
+		((mp->mp_flags & P_DIRTY) ||
+		 (sl && (x = mdb_midl_search(sl, pn)) <= sl[0] && sl[x] == pn)))
+	{
+		unsigned i, j;
+		pgno_t *mop;
+		MDB_ID2 *dl, ix, iy;
+		rc = mdb_midl_need(&env->me_pghead, ovpages);
+		if (rc)
+			return rc;
+		if (!(mp->mp_flags & P_DIRTY)) {
+			/* This page is no longer spilled */
+			if (x == sl[0])
+				sl[0]--;
+			else
+				sl[x] |= 1;
+			goto release;
+		}
+		/* Remove from dirty list */
+		dl = txn->mt_u.dirty_list;
+		x = dl[0].mid--;
+		for (ix = dl[x]; ix.mptr != mp; ix = iy) {
+			if (x > 1) {
+				x--;
+				iy = dl[x];
+				dl[x] = ix;
+			} else {
+				mdb_cassert(mc, x > 1);
+				j = ++(dl[0].mid);
+				dl[j] = ix;		/* Unsorted. OK when MDB_TXN_ERROR. */
+				txn->mt_flags |= MDB_TXN_ERROR;
+				return MDB_CORRUPTED;
+			}
+		}
+		txn->mt_dirty_room++;
+		if (!(env->me_flags & MDB_WRITEMAP))
+			mdb_dpage_free(env, mp);
+release:
+		/* Insert in me_pghead */
+		mop = env->me_pghead;
+		j = mop[0] + ovpages;
+		for (i = mop[0]; i && mop[i] < pg; i--)
+			mop[j--] = mop[i];
+		while (j>i)
+			mop[j--] = pg++;
+		mop[0] += ovpages;
+	} else {
+		rc = mdb_midl_append_range(&txn->mt_free_pgs, pg, ovpages);
+		if (rc)
+			return rc;
+	}
+	mc->mc_db->md_overflow_pages -= ovpages;
+	return 0;
+}
+
+/** Return the data associated with a given node.
+ * @param[in] mc The cursor for this operation.
+ * @param[in] leaf The node being read.
+ * @param[out] data Updated to point to the node's data.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_node_read(MDB_cursor *mc, MDB_node *leaf, MDB_val *data)
+{
+	MDB_page	*omp;		/* overflow page */
+	pgno_t		 pgno;
+	int rc;
+
+	if (!F_ISSET(leaf->mn_flags, F_BIGDATA)) {
+		data->mv_size = NODEDSZ(leaf);
+		data->mv_data = NODEDATA(leaf);
+		return MDB_SUCCESS;
+	}
+
+	/* Read overflow data.
+	 */
+	data->mv_size = NODEDSZ(leaf);
+	memcpy(&pgno, NODEDATA(leaf), sizeof(pgno));
+	if ((rc = mdb_page_get(mc, pgno, &omp, NULL)) != 0) {
+		DPRINTF(("read overflow page %"Z"u failed", pgno));
+		return rc;
+	}
+	data->mv_data = METADATA(omp);
+
+	return MDB_SUCCESS;
+}
+
+int
+mdb_get(MDB_txn *txn, MDB_dbi dbi,
+    MDB_val *key, MDB_val *data)
+{
+	MDB_cursor	mc;
+	MDB_xcursor	mx;
+	int exact = 0;
+	DKBUF;
+
+	DPRINTF(("===> get db %u key [%s]", dbi, DKEY(key)));
+
+	if (!key || !data || !TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+
+	if (txn->mt_flags & MDB_TXN_BLOCKED)
+		return MDB_BAD_TXN;
+
+	mdb_cursor_init(&mc, txn, dbi, &mx);
+	return mdb_cursor_set(&mc, key, data, MDB_SET, &exact);
+}
+
+/** Find a sibling for a page.
+ * Replaces the page at the top of the cursor's stack with the
+ * specified sibling, if one exists.
+ * @param[in] mc The cursor for this operation.
+ * @param[in] move_right Non-zero if the right sibling is requested,
+ * otherwise the left sibling.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_cursor_sibling(MDB_cursor *mc, int move_right)
+{
+	int		 rc;
+	MDB_node	*indx;
+	MDB_page	*mp;
+
+	if (mc->mc_snum < 2) {
+		return MDB_NOTFOUND;		/* root has no siblings */
+	}
+
+	mdb_cursor_pop(mc);
+	DPRINTF(("parent page is page %"Z"u, index %u",
+		mc->mc_pg[mc->mc_top]->mp_pgno, mc->mc_ki[mc->mc_top]));
+
+	if (move_right ? (mc->mc_ki[mc->mc_top] + 1u >= NUMKEYS(mc->mc_pg[mc->mc_top]))
+		       : (mc->mc_ki[mc->mc_top] == 0)) {
+		DPRINTF(("no more keys left, moving to %s sibling",
+		    move_right ? "right" : "left"));
+		if ((rc = mdb_cursor_sibling(mc, move_right)) != MDB_SUCCESS) {
+			/* undo cursor_pop before returning */
+			mc->mc_top++;
+			mc->mc_snum++;
+			return rc;
+		}
+	} else {
+		if (move_right)
+			mc->mc_ki[mc->mc_top]++;
+		else
+			mc->mc_ki[mc->mc_top]--;
+		DPRINTF(("just moving to %s index key %u",
+		    move_right ? "right" : "left", mc->mc_ki[mc->mc_top]));
+	}
+	mdb_cassert(mc, IS_BRANCH(mc->mc_pg[mc->mc_top]));
+
+	indx = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+	if ((rc = mdb_page_get(mc, NODEPGNO(indx), &mp, NULL)) != 0) {
+		/* mc will be inconsistent if caller does mc_snum++ as above */
+		mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
+		return rc;
+	}
+
+	mdb_cursor_push(mc, mp);
+	if (!move_right)
+		mc->mc_ki[mc->mc_top] = NUMKEYS(mp)-1;
+
+	return MDB_SUCCESS;
+}
+
+/** Move the cursor to the next data item. */
+static int
+mdb_cursor_next(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
+{
+	MDB_page	*mp;
+	MDB_node	*leaf;
+	int rc;
+
+	if ((mc->mc_flags & C_DEL && op == MDB_NEXT_DUP))
+		return MDB_NOTFOUND;
+
+	if (!(mc->mc_flags & C_INITIALIZED))
+		return mdb_cursor_first(mc, key, data);
+
+	mp = mc->mc_pg[mc->mc_top];
+
+	if (mc->mc_flags & C_EOF) {
+		if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mp)-1)
+			return MDB_NOTFOUND;
+		mc->mc_flags ^= C_EOF;
+	}
+
+	if (mc->mc_db->md_flags & MDB_DUPSORT) {
+		leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			if (op == MDB_NEXT || op == MDB_NEXT_DUP) {
+				rc = mdb_cursor_next(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_NEXT);
+				if (op != MDB_NEXT || rc != MDB_NOTFOUND) {
+					if (rc == MDB_SUCCESS)
+						MDB_GET_KEY(leaf, key);
+					return rc;
+				}
+			}
+		} else {
+			mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+			if (op == MDB_NEXT_DUP)
+				return MDB_NOTFOUND;
+		}
+	}
+
+	DPRINTF(("cursor_next: top page is %"Z"u in cursor %p",
+		mdb_dbg_pgno(mp), (void *) mc));
+	if (mc->mc_flags & C_DEL) {
+		mc->mc_flags ^= C_DEL;
+		goto skip;
+	}
+
+	if (mc->mc_ki[mc->mc_top] + 1u >= NUMKEYS(mp)) {
+		DPUTS("=====> move to next sibling page");
+		if ((rc = mdb_cursor_sibling(mc, 1)) != MDB_SUCCESS) {
+			mc->mc_flags |= C_EOF;
+			return rc;
+		}
+		mp = mc->mc_pg[mc->mc_top];
+		DPRINTF(("next page is %"Z"u, key index %u", mp->mp_pgno, mc->mc_ki[mc->mc_top]));
+	} else
+		mc->mc_ki[mc->mc_top]++;
+
+skip:
+	DPRINTF(("==> cursor points to page %"Z"u with %u keys, key index %u",
+	    mdb_dbg_pgno(mp), NUMKEYS(mp), mc->mc_ki[mc->mc_top]));
+
+	if (IS_LEAF2(mp)) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	mdb_cassert(mc, IS_LEAF(mp));
+	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		mdb_xcursor_init1(mc, leaf);
+	}
+	if (data) {
+		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
+			return rc;
+
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+			if (rc != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	MDB_GET_KEY(leaf, key);
+	return MDB_SUCCESS;
+}
+
+/** Move the cursor to the previous data item. */
+static int
+mdb_cursor_prev(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
+{
+	MDB_page	*mp;
+	MDB_node	*leaf;
+	int rc;
+
+	if (!(mc->mc_flags & C_INITIALIZED)) {
+		rc = mdb_cursor_last(mc, key, data);
+		if (rc)
+			return rc;
+		mc->mc_ki[mc->mc_top]++;
+	}
+
+	mp = mc->mc_pg[mc->mc_top];
+
+	if (mc->mc_db->md_flags & MDB_DUPSORT) {
+		leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			if (op == MDB_PREV || op == MDB_PREV_DUP) {
+				rc = mdb_cursor_prev(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_PREV);
+				if (op != MDB_PREV || rc != MDB_NOTFOUND) {
+					if (rc == MDB_SUCCESS) {
+						MDB_GET_KEY(leaf, key);
+						mc->mc_flags &= ~C_EOF;
+					}
+					return rc;
+				}
+			}
+		} else {
+			mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+			if (op == MDB_PREV_DUP)
+				return MDB_NOTFOUND;
+		}
+	}
+
+	DPRINTF(("cursor_prev: top page is %"Z"u in cursor %p",
+		mdb_dbg_pgno(mp), (void *) mc));
+
+	mc->mc_flags &= ~(C_EOF|C_DEL);
+
+	if (mc->mc_ki[mc->mc_top] == 0)  {
+		DPUTS("=====> move to prev sibling page");
+		if ((rc = mdb_cursor_sibling(mc, 0)) != MDB_SUCCESS) {
+			return rc;
+		}
+		mp = mc->mc_pg[mc->mc_top];
+		mc->mc_ki[mc->mc_top] = NUMKEYS(mp) - 1;
+		DPRINTF(("prev page is %"Z"u, key index %u", mp->mp_pgno, mc->mc_ki[mc->mc_top]));
+	} else
+		mc->mc_ki[mc->mc_top]--;
+
+	DPRINTF(("==> cursor points to page %"Z"u with %u keys, key index %u",
+	    mdb_dbg_pgno(mp), NUMKEYS(mp), mc->mc_ki[mc->mc_top]));
+
+	if (IS_LEAF2(mp)) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	mdb_cassert(mc, IS_LEAF(mp));
+	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		mdb_xcursor_init1(mc, leaf);
+	}
+	if (data) {
+		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
+			return rc;
+
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
+			if (rc != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	MDB_GET_KEY(leaf, key);
+	return MDB_SUCCESS;
+}
+
+/** Set the cursor on a specific data item. */
+static int
+mdb_cursor_set(MDB_cursor *mc, MDB_val *key, MDB_val *data,
+    MDB_cursor_op op, int *exactp)
+{
+	int		 rc;
+	MDB_page	*mp;
+	MDB_node	*leaf = NULL;
+	DKBUF;
+
+	if (key->mv_size == 0)
+		return MDB_BAD_VALSIZE;
+
+	if (mc->mc_xcursor)
+		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+
+	/* See if we're already on the right page */
+	if (mc->mc_flags & C_INITIALIZED) {
+		MDB_val nodekey;
+
+		mp = mc->mc_pg[mc->mc_top];
+		if (!NUMKEYS(mp)) {
+			mc->mc_ki[mc->mc_top] = 0;
+			return MDB_NOTFOUND;
+		}
+		if (mp->mp_flags & P_LEAF2) {
+			nodekey.mv_size = mc->mc_db->md_pad;
+			nodekey.mv_data = LEAF2KEY(mp, 0, nodekey.mv_size);
+		} else {
+			leaf = NODEPTR(mp, 0);
+			MDB_GET_KEY2(leaf, nodekey);
+		}
+		rc = mc->mc_dbx->md_cmp(key, &nodekey);
+		if (rc == 0) {
+			/* Probably happens rarely, but first node on the page
+			 * was the one we wanted.
+			 */
+			mc->mc_ki[mc->mc_top] = 0;
+			if (exactp)
+				*exactp = 1;
+			goto set1;
+		}
+		if (rc > 0) {
+			unsigned int i;
+			unsigned int nkeys = NUMKEYS(mp);
+			if (nkeys > 1) {
+				if (mp->mp_flags & P_LEAF2) {
+					nodekey.mv_data = LEAF2KEY(mp,
+						 nkeys-1, nodekey.mv_size);
+				} else {
+					leaf = NODEPTR(mp, nkeys-1);
+					MDB_GET_KEY2(leaf, nodekey);
+				}
+				rc = mc->mc_dbx->md_cmp(key, &nodekey);
+				if (rc == 0) {
+					/* last node was the one we wanted */
+					mc->mc_ki[mc->mc_top] = nkeys-1;
+					if (exactp)
+						*exactp = 1;
+					goto set1;
+				}
+				if (rc < 0) {
+					if (mc->mc_ki[mc->mc_top] < NUMKEYS(mp)) {
+						/* This is definitely the right page, skip search_page */
+						if (mp->mp_flags & P_LEAF2) {
+							nodekey.mv_data = LEAF2KEY(mp,
+								 mc->mc_ki[mc->mc_top], nodekey.mv_size);
+						} else {
+							leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+							MDB_GET_KEY2(leaf, nodekey);
+						}
+						rc = mc->mc_dbx->md_cmp(key, &nodekey);
+						if (rc == 0) {
+							/* current node was the one we wanted */
+							if (exactp)
+								*exactp = 1;
+							goto set1;
+						}
+					}
+					rc = 0;
+					mc->mc_flags &= ~C_EOF;
+					goto set2;
+				}
+			}
+			/* If any parents have right-sibs, search.
+			 * Otherwise, there's nothing further.
+			 */
+			for (i=0; i<mc->mc_top; i++)
+				if (mc->mc_ki[i] <
+					NUMKEYS(mc->mc_pg[i])-1)
+					break;
+			if (i == mc->mc_top) {
+				/* There are no other pages */
+				mc->mc_ki[mc->mc_top] = nkeys;
+				return MDB_NOTFOUND;
+			}
+		}
+		if (!mc->mc_top) {
+			/* There are no other pages */
+			mc->mc_ki[mc->mc_top] = 0;
+			if (op == MDB_SET_RANGE && !exactp) {
+				rc = 0;
+				goto set1;
+			} else
+				return MDB_NOTFOUND;
+		}
+	} else {
+		mc->mc_pg[0] = 0;
+	}
+
+	rc = mdb_page_search(mc, key, 0);
+	if (rc != MDB_SUCCESS)
+		return rc;
+
+	mp = mc->mc_pg[mc->mc_top];
+	mdb_cassert(mc, IS_LEAF(mp));
+
+set2:
+	leaf = mdb_node_search(mc, key, exactp);
+	if (exactp != NULL && !*exactp) {
+		/* MDB_SET specified and not an exact match. */
+		return MDB_NOTFOUND;
+	}
+
+	if (leaf == NULL) {
+		DPUTS("===> inexact leaf not found, goto sibling");
+		if ((rc = mdb_cursor_sibling(mc, 1)) != MDB_SUCCESS) {
+			mc->mc_flags |= C_EOF;
+			return rc;		/* no entries matched */
+		}
+		mp = mc->mc_pg[mc->mc_top];
+		mdb_cassert(mc, IS_LEAF(mp));
+		leaf = NODEPTR(mp, 0);
+	}
+
+set1:
+	mc->mc_flags |= C_INITIALIZED;
+	mc->mc_flags &= ~C_EOF;
+
+	if (IS_LEAF2(mp)) {
+		if (op == MDB_SET_RANGE || op == MDB_SET_KEY) {
+			key->mv_size = mc->mc_db->md_pad;
+			key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
+		}
+		return MDB_SUCCESS;
+	}
+
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		mdb_xcursor_init1(mc, leaf);
+	}
+	if (data) {
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			if (op == MDB_SET || op == MDB_SET_KEY || op == MDB_SET_RANGE) {
+				rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+			} else {
+				int ex2, *ex2p;
+				if (op == MDB_GET_BOTH) {
+					ex2p = &ex2;
+					ex2 = 0;
+				} else {
+					ex2p = NULL;
+				}
+				rc = mdb_cursor_set(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_SET_RANGE, ex2p);
+				if (rc != MDB_SUCCESS)
+					return rc;
+			}
+		} else if (op == MDB_GET_BOTH || op == MDB_GET_BOTH_RANGE) {
+			MDB_val olddata;
+			MDB_cmp_func *dcmp;
+			if ((rc = mdb_node_read(mc, leaf, &olddata)) != MDB_SUCCESS)
+				return rc;
+			dcmp = mc->mc_dbx->md_dcmp;
+#if UINT_MAX < SIZE_MAX
+			if (dcmp == mdb_cmp_int && olddata.mv_size == sizeof(size_t))
+				dcmp = mdb_cmp_clong;
+#endif
+			rc = dcmp(data, &olddata);
+			if (rc) {
+				if (op == MDB_GET_BOTH || rc > 0)
+					return MDB_NOTFOUND;
+				rc = 0;
+			}
+			*data = olddata;
+
+		} else {
+			if (mc->mc_xcursor)
+				mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+			if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	/* The key already matches in all other cases */
+	if (op == MDB_SET_RANGE || op == MDB_SET_KEY)
+		MDB_GET_KEY(leaf, key);
+	DPRINTF(("==> cursor placed on key [%s]", DKEY(key)));
+
+	return rc;
+}
+
+/** Move the cursor to the first item in the database. */
+static int
+mdb_cursor_first(MDB_cursor *mc, MDB_val *key, MDB_val *data)
+{
+	int		 rc;
+	MDB_node	*leaf;
+
+	if (mc->mc_xcursor)
+		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+
+	if (!(mc->mc_flags & C_INITIALIZED) || mc->mc_top) {
+		rc = mdb_page_search(mc, NULL, MDB_PS_FIRST);
+		if (rc != MDB_SUCCESS)
+			return rc;
+	}
+	mdb_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
+
+	leaf = NODEPTR(mc->mc_pg[mc->mc_top], 0);
+	mc->mc_flags |= C_INITIALIZED;
+	mc->mc_flags &= ~C_EOF;
+
+	mc->mc_ki[mc->mc_top] = 0;
+
+	if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], 0, key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	if (data) {
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			mdb_xcursor_init1(mc, leaf);
+			rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+			if (rc)
+				return rc;
+		} else {
+			if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
+				return rc;
+		}
+	}
+	MDB_GET_KEY(leaf, key);
+	return MDB_SUCCESS;
+}
+
+/** Move the cursor to the last item in the database. */
+static int
+mdb_cursor_last(MDB_cursor *mc, MDB_val *key, MDB_val *data)
+{
+	int		 rc;
+	MDB_node	*leaf;
+
+	if (mc->mc_xcursor)
+		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+
+	if (!(mc->mc_flags & C_INITIALIZED) || mc->mc_top) {
+		rc = mdb_page_search(mc, NULL, MDB_PS_LAST);
+		if (rc != MDB_SUCCESS)
+			return rc;
+	}
+	mdb_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
+
+	mc->mc_ki[mc->mc_top] = NUMKEYS(mc->mc_pg[mc->mc_top]) - 1;
+	mc->mc_flags |= C_INITIALIZED|C_EOF;
+	leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+
+	if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+		key->mv_size = mc->mc_db->md_pad;
+		key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], key->mv_size);
+		return MDB_SUCCESS;
+	}
+
+	if (data) {
+		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+			mdb_xcursor_init1(mc, leaf);
+			rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
+			if (rc)
+				return rc;
+		} else {
+			if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	MDB_GET_KEY(leaf, key);
+	return MDB_SUCCESS;
+}
+
+int
+mdb_cursor_get(MDB_cursor *mc, MDB_val *key, MDB_val *data,
+    MDB_cursor_op op)
+{
+	int		 rc;
+	int		 exact = 0;
+	int		 (*mfunc)(MDB_cursor *mc, MDB_val *key, MDB_val *data);
+
+	if (mc == NULL)
+		return EINVAL;
+
+	if (mc->mc_txn->mt_flags & MDB_TXN_BLOCKED)
+		return MDB_BAD_TXN;
+
+	switch (op) {
+	case MDB_GET_CURRENT:
+		if (!(mc->mc_flags & C_INITIALIZED)) {
+			rc = EINVAL;
+		} else {
+			MDB_page *mp = mc->mc_pg[mc->mc_top];
+			int nkeys = NUMKEYS(mp);
+			if (!nkeys || mc->mc_ki[mc->mc_top] >= nkeys) {
+				mc->mc_ki[mc->mc_top] = nkeys;
+				rc = MDB_NOTFOUND;
+				break;
+			}
+			rc = MDB_SUCCESS;
+			if (IS_LEAF2(mp)) {
+				key->mv_size = mc->mc_db->md_pad;
+				key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
+			} else {
+				MDB_node *leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+				MDB_GET_KEY(leaf, key);
+				if (data) {
+					if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+						rc = mdb_cursor_get(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_GET_CURRENT);
+					} else {
+						rc = mdb_node_read(mc, leaf, data);
+					}
+				}
+			}
+		}
+		break;
+	case MDB_GET_BOTH:
+	case MDB_GET_BOTH_RANGE:
+		if (data == NULL) {
+			rc = EINVAL;
+			break;
+		}
+		if (mc->mc_xcursor == NULL) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		/* FALLTHRU */
+	case MDB_SET:
+	case MDB_SET_KEY:
+	case MDB_SET_RANGE:
+		if (key == NULL) {
+			rc = EINVAL;
+		} else {
+			rc = mdb_cursor_set(mc, key, data, op,
+				op == MDB_SET_RANGE ? NULL : &exact);
+		}
+		break;
+	case MDB_GET_MULTIPLE:
+		if (data == NULL || !(mc->mc_flags & C_INITIALIZED)) {
+			rc = EINVAL;
+			break;
+		}
+		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		rc = MDB_SUCCESS;
+		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) ||
+			(mc->mc_xcursor->mx_cursor.mc_flags & C_EOF))
+			break;
+		goto fetchm;
+	case MDB_NEXT_MULTIPLE:
+		if (data == NULL) {
+			rc = EINVAL;
+			break;
+		}
+		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		rc = mdb_cursor_next(mc, key, data, MDB_NEXT_DUP);
+		if (rc == MDB_SUCCESS) {
+			if (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
+				MDB_cursor *mx;
+fetchm:
+				mx = &mc->mc_xcursor->mx_cursor;
+				data->mv_size = NUMKEYS(mx->mc_pg[mx->mc_top]) *
+					mx->mc_db->md_pad;
+				data->mv_data = METADATA(mx->mc_pg[mx->mc_top]);
+				mx->mc_ki[mx->mc_top] = NUMKEYS(mx->mc_pg[mx->mc_top])-1;
+			} else {
+				rc = MDB_NOTFOUND;
+			}
+		}
+		break;
+	case MDB_PREV_MULTIPLE:
+		if (data == NULL) {
+			rc = EINVAL;
+			break;
+		}
+		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		if (!(mc->mc_flags & C_INITIALIZED))
+			rc = mdb_cursor_last(mc, key, data);
+		else
+			rc = MDB_SUCCESS;
+		if (rc == MDB_SUCCESS) {
+			MDB_cursor *mx = &mc->mc_xcursor->mx_cursor;
+			if (mx->mc_flags & C_INITIALIZED) {
+				rc = mdb_cursor_sibling(mx, 0);
+				if (rc == MDB_SUCCESS)
+					goto fetchm;
+			} else {
+				rc = MDB_NOTFOUND;
+			}
+		}
+		break;
+	case MDB_NEXT:
+	case MDB_NEXT_DUP:
+	case MDB_NEXT_NODUP:
+		rc = mdb_cursor_next(mc, key, data, op);
+		break;
+	case MDB_PREV:
+	case MDB_PREV_DUP:
+	case MDB_PREV_NODUP:
+		rc = mdb_cursor_prev(mc, key, data, op);
+		break;
+	case MDB_FIRST:
+		rc = mdb_cursor_first(mc, key, data);
+		break;
+	case MDB_FIRST_DUP:
+		mfunc = mdb_cursor_first;
+	mmove:
+		if (data == NULL || !(mc->mc_flags & C_INITIALIZED)) {
+			rc = EINVAL;
+			break;
+		}
+		if (mc->mc_xcursor == NULL) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mc->mc_pg[mc->mc_top])) {
+			mc->mc_ki[mc->mc_top] = NUMKEYS(mc->mc_pg[mc->mc_top]);
+			rc = MDB_NOTFOUND;
+			break;
+		}
+		{
+			MDB_node *leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+			if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+				MDB_GET_KEY(leaf, key);
+				rc = mdb_node_read(mc, leaf, data);
+				break;
+			}
+		}
+		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED)) {
+			rc = EINVAL;
+			break;
+		}
+		rc = mfunc(&mc->mc_xcursor->mx_cursor, data, NULL);
+		break;
+	case MDB_LAST:
+		rc = mdb_cursor_last(mc, key, data);
+		break;
+	case MDB_LAST_DUP:
+		mfunc = mdb_cursor_last;
+		goto mmove;
+	default:
+		DPRINTF(("unhandled/unimplemented cursor operation %u", op));
+		rc = EINVAL;
+		break;
+	}
+
+	if (mc->mc_flags & C_DEL)
+		mc->mc_flags ^= C_DEL;
+
+	return rc;
+}
+
+/** Touch all the pages in the cursor stack. Set mc_top.
+ *	Makes sure all the pages are writable, before attempting a write operation.
+ * @param[in] mc The cursor to operate on.
+ */
+static int
+mdb_cursor_touch(MDB_cursor *mc)
+{
+	int rc = MDB_SUCCESS;
+
+	if (mc->mc_dbi >= CORE_DBS && !(*mc->mc_dbflag & (DB_DIRTY|DB_DUPDATA))) {
+		/* Touch DB record of named DB */
+		MDB_cursor mc2;
+		MDB_xcursor mcx;
+		if (TXN_DBI_CHANGED(mc->mc_txn, mc->mc_dbi))
+			return MDB_BAD_DBI;
+		mdb_cursor_init(&mc2, mc->mc_txn, MAIN_DBI, &mcx);
+		rc = mdb_page_search(&mc2, &mc->mc_dbx->md_name, MDB_PS_MODIFY);
+		if (rc)
+			 return rc;
+		*mc->mc_dbflag |= DB_DIRTY;
+	}
+	mc->mc_top = 0;
+	if (mc->mc_snum) {
+		do {
+			rc = mdb_page_touch(mc);
+		} while (!rc && ++(mc->mc_top) < mc->mc_snum);
+		mc->mc_top = mc->mc_snum-1;
+	}
+	return rc;
+}
+
+/** Do not spill pages to disk if txn is getting full, may fail instead */
+#define MDB_NOSPILL	0x8000
+
+int
+mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
+    unsigned int flags)
+{
+	MDB_env		*env;
+	MDB_node	*leaf = NULL;
+	MDB_page	*fp, *mp, *sub_root = NULL;
+	uint16_t	fp_flags;
+	MDB_val		xdata, *rdata, dkey, olddata;
+	MDB_db dummy;
+	int do_sub = 0, insert_key, insert_data;
+	unsigned int mcount = 0, dcount = 0, nospill;
+	size_t nsize;
+	int rc, rc2;
+	unsigned int nflags;
+	DKBUF;
+
+	if (mc == NULL || key == NULL)
+		return EINVAL;
+
+	env = mc->mc_txn->mt_env;
+
+	/* Check this first so counter will always be zero on any
+	 * early failures.
+	 */
+	if (flags & MDB_MULTIPLE) {
+		dcount = data[1].mv_size;
+		data[1].mv_size = 0;
+		if (!F_ISSET(mc->mc_db->md_flags, MDB_DUPFIXED))
+			return MDB_INCOMPATIBLE;
+	}
+
+	nospill = flags & MDB_NOSPILL;
+	flags &= ~MDB_NOSPILL;
+
+	if (mc->mc_txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_BLOCKED))
+		return (mc->mc_txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
+
+	if (key->mv_size-1 >= ENV_MAXKEY(env))
+		return MDB_BAD_VALSIZE;
+
+#if SIZE_MAX > MAXDATASIZE
+	if (data->mv_size > ((mc->mc_db->md_flags & MDB_DUPSORT) ? ENV_MAXKEY(env) : MAXDATASIZE))
+		return MDB_BAD_VALSIZE;
+#else
+	if ((mc->mc_db->md_flags & MDB_DUPSORT) && data->mv_size > ENV_MAXKEY(env))
+		return MDB_BAD_VALSIZE;
+#endif
+
+	DPRINTF(("==> put db %d key [%s], size %"Z"u, data size %"Z"u",
+		DDBI(mc), DKEY(key), key ? key->mv_size : 0, data->mv_size));
+
+	dkey.mv_size = 0;
+
+	if (flags == MDB_CURRENT) {
+		if (!(mc->mc_flags & C_INITIALIZED))
+			return EINVAL;
+		rc = MDB_SUCCESS;
+	} else if (mc->mc_db->md_root == P_INVALID) {
+		/* new database, cursor has nothing to point to */
+		mc->mc_snum = 0;
+		mc->mc_top = 0;
+		mc->mc_flags &= ~C_INITIALIZED;
+		rc = MDB_NO_ROOT;
+	} else {
+		int exact = 0;
+		MDB_val d2;
+		if (flags & MDB_APPEND) {
+			MDB_val k2;
+			rc = mdb_cursor_last(mc, &k2, &d2);
+			if (rc == 0) {
+				rc = mc->mc_dbx->md_cmp(key, &k2);
+				if (rc > 0) {
+					rc = MDB_NOTFOUND;
+					mc->mc_ki[mc->mc_top]++;
+				} else {
+					/* new key is <= last key */
+					rc = MDB_KEYEXIST;
+				}
+			}
+		} else {
+			rc = mdb_cursor_set(mc, key, &d2, MDB_SET, &exact);
+		}
+		if ((flags & MDB_NOOVERWRITE) && rc == 0) {
+			DPRINTF(("duplicate key [%s]", DKEY(key)));
+			*data = d2;
+			return MDB_KEYEXIST;
+		}
+		if (rc && rc != MDB_NOTFOUND)
+			return rc;
+	}
+
+	if (mc->mc_flags & C_DEL)
+		mc->mc_flags ^= C_DEL;
+
+	/* Cursor is positioned, check for room in the dirty list */
+	if (!nospill) {
+		if (flags & MDB_MULTIPLE) {
+			rdata = &xdata;
+			xdata.mv_size = data->mv_size * dcount;
+		} else {
+			rdata = data;
+		}
+		if ((rc2 = mdb_page_spill(mc, key, rdata)))
+			return rc2;
+	}
+
+	if (rc == MDB_NO_ROOT) {
+		MDB_page *np;
+		/* new database, write a root leaf page */
+		DPUTS("allocating new root leaf page");
+		if ((rc2 = mdb_page_new(mc, P_LEAF, 1, &np))) {
+			return rc2;
+		}
+		mdb_cursor_push(mc, np);
+		mc->mc_db->md_root = np->mp_pgno;
+		mc->mc_db->md_depth++;
+		*mc->mc_dbflag |= DB_DIRTY;
+		if ((mc->mc_db->md_flags & (MDB_DUPSORT|MDB_DUPFIXED))
+			== MDB_DUPFIXED)
+			np->mp_flags |= P_LEAF2;
+		mc->mc_flags |= C_INITIALIZED;
+	} else {
+		/* make sure all cursor pages are writable */
+		rc2 = mdb_cursor_touch(mc);
+		if (rc2)
+			return rc2;
+	}
+
+	insert_key = insert_data = rc;
+	if (insert_key) {
+		/* The key does not exist */
+		DPRINTF(("inserting key at index %i", mc->mc_ki[mc->mc_top]));
+		if ((mc->mc_db->md_flags & MDB_DUPSORT) &&
+			LEAFSIZE(key, data) > env->me_nodemax)
+		{
+			/* Too big for a node, insert in sub-DB.  Set up an empty
+			 * "old sub-page" for prep_subDB to expand to a full page.
+			 */
+			fp_flags = P_LEAF|P_DIRTY;
+			fp = env->me_pbuf;
+			fp->mp_pad = data->mv_size; /* used if MDB_DUPFIXED */
+			fp->mp_lower = fp->mp_upper = (PAGEHDRSZ-PAGEBASE);
+			olddata.mv_size = PAGEHDRSZ;
+			goto prep_subDB;
+		}
+	} else {
+		/* there's only a key anyway, so this is a no-op */
+		if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
+			char *ptr;
+			unsigned int ksize = mc->mc_db->md_pad;
+			if (key->mv_size != ksize)
+				return MDB_BAD_VALSIZE;
+			ptr = LEAF2KEY(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], ksize);
+			memcpy(ptr, key->mv_data, ksize);
+fix_parent:
+			/* if overwriting slot 0 of leaf, need to
+			 * update branch key if there is a parent page
+			 */
+			if (mc->mc_top && !mc->mc_ki[mc->mc_top]) {
+				unsigned short dtop = 1;
+				mc->mc_top--;
+				/* slot 0 is always an empty key, find real slot */
+				while (mc->mc_top && !mc->mc_ki[mc->mc_top]) {
+					mc->mc_top--;
+					dtop++;
+				}
+				if (mc->mc_ki[mc->mc_top])
+					rc2 = mdb_update_key(mc, key);
+				else
+					rc2 = MDB_SUCCESS;
+				mc->mc_top += dtop;
+				if (rc2)
+					return rc2;
+			}
+			return MDB_SUCCESS;
+		}
+
+more:
+		leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+		olddata.mv_size = NODEDSZ(leaf);
+		olddata.mv_data = NODEDATA(leaf);
+
+		/* DB has dups? */
+		if (F_ISSET(mc->mc_db->md_flags, MDB_DUPSORT)) {
+			/* Prepare (sub-)page/sub-DB to accept the new item,
+			 * if needed.  fp: old sub-page or a header faking
+			 * it.  mp: new (sub-)page.  offset: growth in page
+			 * size.  xdata: node data with new page or DB.
+			 */
+			unsigned	i, offset = 0;
+			mp = fp = xdata.mv_data = env->me_pbuf;
+			mp->mp_pgno = mc->mc_pg[mc->mc_top]->mp_pgno;
+
+			/* Was a single item before, must convert now */
+			if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+				MDB_cmp_func *dcmp;
+				/* Just overwrite the current item */
+				if (flags == MDB_CURRENT)
+					goto current;
+				dcmp = mc->mc_dbx->md_dcmp;
+#if UINT_MAX < SIZE_MAX
+				if (dcmp == mdb_cmp_int && olddata.mv_size == sizeof(size_t))
+					dcmp = mdb_cmp_clong;
+#endif
+				/* does data match? */
+				if (!dcmp(data, &olddata)) {
+					if (flags & (MDB_NODUPDATA|MDB_APPENDDUP))
+						return MDB_KEYEXIST;
+					/* overwrite it */
+					goto current;
+				}
+
+				/* Back up original data item */
+				dkey.mv_size = olddata.mv_size;
+				dkey.mv_data = memcpy(fp+1, olddata.mv_data, olddata.mv_size);
+
+				/* Make sub-page header for the dup items, with dummy body */
+				fp->mp_flags = P_LEAF|P_DIRTY|P_SUBP;
+				fp->mp_lower = (PAGEHDRSZ-PAGEBASE);
+				xdata.mv_size = PAGEHDRSZ + dkey.mv_size + data->mv_size;
+				if (mc->mc_db->md_flags & MDB_DUPFIXED) {
+					fp->mp_flags |= P_LEAF2;
+					fp->mp_pad = data->mv_size;
+					xdata.mv_size += 2 * data->mv_size;	/* leave space for 2 more */
+				} else {
+					xdata.mv_size += 2 * (sizeof(indx_t) + NODESIZE) +
+						(dkey.mv_size & 1) + (data->mv_size & 1);
+				}
+				fp->mp_upper = xdata.mv_size - PAGEBASE;
+				olddata.mv_size = xdata.mv_size; /* pretend olddata is fp */
+			} else if (leaf->mn_flags & F_SUBDATA) {
+				/* Data is on sub-DB, just store it */
+				flags |= F_DUPDATA|F_SUBDATA;
+				goto put_sub;
+			} else {
+				/* Data is on sub-page */
+				fp = olddata.mv_data;
+				switch (flags) {
+				default:
+					if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
+						offset = EVEN(NODESIZE + sizeof(indx_t) +
+							data->mv_size);
+						break;
+					}
+					offset = fp->mp_pad;
+					if (SIZELEFT(fp) < offset) {
+						offset *= 4; /* space for 4 more */
+						break;
+					}
+					/* FALLTHRU: Big enough MDB_DUPFIXED sub-page */
+				case MDB_CURRENT:
+					fp->mp_flags |= P_DIRTY;
+					COPY_PGNO(fp->mp_pgno, mp->mp_pgno);
+					mc->mc_xcursor->mx_cursor.mc_pg[0] = fp;
+					flags |= F_DUPDATA;
+					goto put_sub;
+				}
+				xdata.mv_size = olddata.mv_size + offset;
+			}
+
+			fp_flags = fp->mp_flags;
+			if (NODESIZE + NODEKSZ(leaf) + xdata.mv_size > env->me_nodemax) {
+					/* Too big for a sub-page, convert to sub-DB */
+					fp_flags &= ~P_SUBP;
+prep_subDB:
+					if (mc->mc_db->md_flags & MDB_DUPFIXED) {
+						fp_flags |= P_LEAF2;
+						dummy.md_pad = fp->mp_pad;
+						dummy.md_flags = MDB_DUPFIXED;
+						if (mc->mc_db->md_flags & MDB_INTEGERDUP)
+							dummy.md_flags |= MDB_INTEGERKEY;
+					} else {
+						dummy.md_pad = 0;
+						dummy.md_flags = 0;
+					}
+					dummy.md_depth = 1;
+					dummy.md_branch_pages = 0;
+					dummy.md_leaf_pages = 1;
+					dummy.md_overflow_pages = 0;
+					dummy.md_entries = NUMKEYS(fp);
+					xdata.mv_size = sizeof(MDB_db);
+					xdata.mv_data = &dummy;
+					if ((rc = mdb_page_alloc(mc, 1, &mp)))
+						return rc;
+					offset = env->me_psize - olddata.mv_size;
+					flags |= F_DUPDATA|F_SUBDATA;
+					dummy.md_root = mp->mp_pgno;
+					sub_root = mp;
+			}
+			if (mp != fp) {
+				mp->mp_flags = fp_flags | P_DIRTY;
+				mp->mp_pad   = fp->mp_pad;
+				mp->mp_lower = fp->mp_lower;
+				mp->mp_upper = fp->mp_upper + offset;
+				if (fp_flags & P_LEAF2) {
+					memcpy(METADATA(mp), METADATA(fp), NUMKEYS(fp) * fp->mp_pad);
+				} else {
+					memcpy((char *)mp + mp->mp_upper + PAGEBASE, (char *)fp + fp->mp_upper + PAGEBASE,
+						olddata.mv_size - fp->mp_upper - PAGEBASE);
+					memcpy((char *)(&mp->mp_ptrs), (char *)(&fp->mp_ptrs), NUMKEYS(fp) * sizeof(mp->mp_ptrs[0]));
+					for (i=0; i<NUMKEYS(fp); i++)
+						mp->mp_ptrs[i] += offset;
+				}
+			}
+
+			rdata = &xdata;
+			flags |= F_DUPDATA;
+			do_sub = 1;
+			if (!insert_key)
+				mdb_node_del(mc, 0);
+			goto new_sub;
+		}
+current:
+		/* LMDB passes F_SUBDATA in 'flags' to write a DB record */
+		if ((leaf->mn_flags ^ flags) & F_SUBDATA)
+			return MDB_INCOMPATIBLE;
+		/* overflow page overwrites need special handling */
+		if (F_ISSET(leaf->mn_flags, F_BIGDATA)) {
+			MDB_page *omp;
+			pgno_t pg;
+			int level, ovpages, dpages = OVPAGES(data->mv_size, env->me_psize);
+
+			memcpy(&pg, olddata.mv_data, sizeof(pg));
+			if ((rc2 = mdb_page_get(mc, pg, &omp, &level)) != 0)
+				return rc2;
+			ovpages = omp->mp_pages;
+
+			/* Is the ov page large enough? */
+			if (ovpages >= dpages) {
+			  if (!(omp->mp_flags & P_DIRTY) &&
+				  (level || (env->me_flags & MDB_WRITEMAP)))
+			  {
+				rc = mdb_page_unspill(mc->mc_txn, omp, &omp);
+				if (rc)
+					return rc;
+				level = 0;		/* dirty in this txn or clean */
+			  }
+			  /* Is it dirty? */
+			  if (omp->mp_flags & P_DIRTY) {
+				/* yes, overwrite it. Note in this case we don't
+				 * bother to try shrinking the page if the new data
+				 * is smaller than the overflow threshold.
+				 */
+				if (level > 1) {
+					/* It is writable only in a parent txn */
+					size_t sz = (size_t) env->me_psize * ovpages, off;
+					MDB_page *np = mdb_page_malloc(mc->mc_txn, ovpages);
+					MDB_ID2 id2;
+					if (!np)
+						return ENOMEM;
+					id2.mid = pg;
+					id2.mptr = np;
+					/* Note - this page is already counted in parent's dirty_room */
+					rc2 = mdb_mid2l_insert(mc->mc_txn->mt_u.dirty_list, &id2);
+					mdb_cassert(mc, rc2 == 0);
+					/* Currently we make the page look as with put() in the
+					 * parent txn, in case the user peeks at MDB_RESERVEd
+					 * or unused parts. Some users treat ovpages specially.
+					 */
+					if (!(flags & MDB_RESERVE)) {
+						/* Skip the part where LMDB will put *data.
+						 * Copy end of page, adjusting alignment so
+						 * compiler may copy words instead of bytes.
+						 */
+						off = (PAGEHDRSZ + data->mv_size) & -sizeof(size_t);
+						memcpy((size_t *)((char *)np + off),
+							(size_t *)((char *)omp + off), sz - off);
+						sz = PAGEHDRSZ;
+					}
+					memcpy(np, omp, sz); /* Copy beginning of page */
+					omp = np;
+				}
+				SETDSZ(leaf, data->mv_size);
+				if (F_ISSET(flags, MDB_RESERVE))
+					data->mv_data = METADATA(omp);
+				else
+					memcpy(METADATA(omp), data->mv_data, data->mv_size);
+				return MDB_SUCCESS;
+			  }
+			}
+			if ((rc2 = mdb_ovpage_free(mc, omp)) != MDB_SUCCESS)
+				return rc2;
+		} else if (data->mv_size == olddata.mv_size) {
+			/* same size, just replace it. Note that we could
+			 * also reuse this node if the new data is smaller,
+			 * but instead we opt to shrink the node in that case.
+			 */
+			if (F_ISSET(flags, MDB_RESERVE))
+				data->mv_data = olddata.mv_data;
+			else if (!(mc->mc_flags & C_SUB))
+				memcpy(olddata.mv_data, data->mv_data, data->mv_size);
+			else {
+				memcpy(NODEKEY(leaf), key->mv_data, key->mv_size);
+				goto fix_parent;
+			}
+			return MDB_SUCCESS;
+		}
+		mdb_node_del(mc, 0);
+	}
+
+	rdata = data;
+
+new_sub:
+	nflags = flags & NODE_ADD_FLAGS;
+	nsize = IS_LEAF2(mc->mc_pg[mc->mc_top]) ? key->mv_size : mdb_leaf_size(env, key, rdata);
+	if (SIZELEFT(mc->mc_pg[mc->mc_top]) < nsize) {
+		if (( flags & (F_DUPDATA|F_SUBDATA)) == F_DUPDATA )
+			nflags &= ~MDB_APPEND; /* sub-page may need room to grow */
+		if (!insert_key)
+			nflags |= MDB_SPLIT_REPLACE;
+		rc = mdb_page_split(mc, key, rdata, P_INVALID, nflags);
+	} else {
+		/* There is room already in this leaf page. */
+		rc = mdb_node_add(mc, mc->mc_ki[mc->mc_top], key, rdata, 0, nflags);
+		if (rc == 0) {
+			/* Adjust other cursors pointing to mp */
+			MDB_cursor *m2, *m3;
+			MDB_dbi dbi = mc->mc_dbi;
+			unsigned i = mc->mc_top;
+			MDB_page *mp = mc->mc_pg[i];
+
+			for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+				if (mc->mc_flags & C_SUB)
+					m3 = &m2->mc_xcursor->mx_cursor;
+				else
+					m3 = m2;
+				if (m3 == mc || m3->mc_snum < mc->mc_snum || m3->mc_pg[i] != mp) continue;
+				if (m3->mc_ki[i] >= mc->mc_ki[i] && insert_key) {
+					m3->mc_ki[i]++;
+				}
+				XCURSOR_REFRESH(m3, i, mp);
+			}
+		}
+	}
+
+	if (rc == MDB_SUCCESS) {
+		/* Now store the actual data in the child DB. Note that we're
+		 * storing the user data in the keys field, so there are strict
+		 * size limits on dupdata. The actual data fields of the child
+		 * DB are all zero size.
+		 */
+		if (do_sub) {
+			int xflags, new_dupdata;
+			size_t ecount;
+put_sub:
+			xdata.mv_size = 0;
+			xdata.mv_data = "";
+			leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+			if (flags & MDB_CURRENT) {
+				xflags = MDB_CURRENT|MDB_NOSPILL;
+			} else {
+				mdb_xcursor_init1(mc, leaf);
+				xflags = (flags & MDB_NODUPDATA) ?
+					MDB_NOOVERWRITE|MDB_NOSPILL : MDB_NOSPILL;
+			}
+			if (sub_root)
+				mc->mc_xcursor->mx_cursor.mc_pg[0] = sub_root;
+			new_dupdata = (int)dkey.mv_size;
+			/* converted, write the original data first */
+			if (dkey.mv_size) {
+				rc = mdb_cursor_put(&mc->mc_xcursor->mx_cursor, &dkey, &xdata, xflags);
+				if (rc)
+					goto bad_sub;
+				/* we've done our job */
+				dkey.mv_size = 0;
+			}
+			if (!(leaf->mn_flags & F_SUBDATA) || sub_root) {
+				/* Adjust other cursors pointing to mp */
+				MDB_cursor *m2;
+				MDB_xcursor *mx = mc->mc_xcursor;
+				unsigned i = mc->mc_top;
+				MDB_page *mp = mc->mc_pg[i];
+
+				for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
+					if (m2 == mc || m2->mc_snum < mc->mc_snum) continue;
+					if (!(m2->mc_flags & C_INITIALIZED)) continue;
+					if (m2->mc_pg[i] == mp) {
+						if (m2->mc_ki[i] == mc->mc_ki[i]) {
+							mdb_xcursor_init2(m2, mx, new_dupdata);
+						} else if (!insert_key) {
+							XCURSOR_REFRESH(m2, i, mp);
+						}
+					}
+				}
+			}
+			ecount = mc->mc_xcursor->mx_db.md_entries;
+			if (flags & MDB_APPENDDUP)
+				xflags |= MDB_APPEND;
+			rc = mdb_cursor_put(&mc->mc_xcursor->mx_cursor, data, &xdata, xflags);
+			if (flags & F_SUBDATA) {
+				void *db = NODEDATA(leaf);
+				memcpy(db, &mc->mc_xcursor->mx_db, sizeof(MDB_db));
+			}
+			insert_data = mc->mc_xcursor->mx_db.md_entries - ecount;
+		}
+		/* Increment count unless we just replaced an existing item. */
+		if (insert_data)
+			mc->mc_db->md_entries++;
+		if (insert_key) {
+			/* Invalidate txn if we created an empty sub-DB */
+			if (rc)
+				goto bad_sub;
+			/* If we succeeded and the key didn't exist before,
+			 * make sure the cursor is marked valid.
+			 */
+			mc->mc_flags |= C_INITIALIZED;
+		}
+		if (flags & MDB_MULTIPLE) {
+			if (!rc) {
+				mcount++;
+				/* let caller know how many succeeded, if any */
+				data[1].mv_size = mcount;
+				if (mcount < dcount) {
+					data[0].mv_data = (char *)data[0].mv_data + data[0].mv_size;
+					insert_key = insert_data = 0;
+					goto more;
+				}
+			}
+		}
+		return rc;
+bad_sub:
+		if (rc == MDB_KEYEXIST)	/* should not happen, we deleted that item */
+			rc = MDB_CORRUPTED;
+	}
+	mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+	return rc;
+}
+
+int
+mdb_cursor_del(MDB_cursor *mc, unsigned int flags)
+{
+	MDB_node	*leaf;
+	MDB_page	*mp;
+	int rc;
+
+	if (mc->mc_txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_BLOCKED))
+		return (mc->mc_txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
+
+	if (!(mc->mc_flags & C_INITIALIZED))
+		return EINVAL;
+
+	if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mc->mc_pg[mc->mc_top]))
+		return MDB_NOTFOUND;
+
+	if (!(flags & MDB_NOSPILL) && (rc = mdb_page_spill(mc, NULL, NULL)))
+		return rc;
+
+	rc = mdb_cursor_touch(mc);
+	if (rc)
+		return rc;
+
+	mp = mc->mc_pg[mc->mc_top];
+	if (IS_LEAF2(mp))
+		goto del_key;
+	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		if (flags & MDB_NODUPDATA) {
+			/* mdb_cursor_del0() will subtract the final entry */
+			mc->mc_db->md_entries -= mc->mc_xcursor->mx_db.md_entries - 1;
+			mc->mc_xcursor->mx_cursor.mc_flags &= ~C_INITIALIZED;
+		} else {
+			if (!F_ISSET(leaf->mn_flags, F_SUBDATA)) {
+				mc->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
+			}
+			rc = mdb_cursor_del(&mc->mc_xcursor->mx_cursor, MDB_NOSPILL);
+			if (rc)
+				return rc;
+			/* If sub-DB still has entries, we're done */
+			if (mc->mc_xcursor->mx_db.md_entries) {
+				if (leaf->mn_flags & F_SUBDATA) {
+					/* update subDB info */
+					void *db = NODEDATA(leaf);
+					memcpy(db, &mc->mc_xcursor->mx_db, sizeof(MDB_db));
+				} else {
+					MDB_cursor *m2;
+					/* shrink fake page */
+					mdb_node_shrink(mp, mc->mc_ki[mc->mc_top]);
+					leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+					mc->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
+					/* fix other sub-DB cursors pointed at fake pages on this page */
+					for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
+						if (m2 == mc || m2->mc_snum < mc->mc_snum) continue;
+						if (!(m2->mc_flags & C_INITIALIZED)) continue;
+						if (m2->mc_pg[mc->mc_top] == mp) {
+							XCURSOR_REFRESH(m2, mc->mc_top, mp);
+						}
+					}
+				}
+				mc->mc_db->md_entries--;
+				return rc;
+			} else {
+				mc->mc_xcursor->mx_cursor.mc_flags &= ~C_INITIALIZED;
+			}
+			/* otherwise fall thru and delete the sub-DB */
+		}
+
+		if (leaf->mn_flags & F_SUBDATA) {
+			/* add all the child DB's pages to the free list */
+			rc = mdb_drop0(&mc->mc_xcursor->mx_cursor, 0);
+			if (rc)
+				goto fail;
+		}
+	}
+	/* LMDB passes F_SUBDATA in 'flags' to delete a DB record */
+	else if ((leaf->mn_flags ^ flags) & F_SUBDATA) {
+		rc = MDB_INCOMPATIBLE;
+		goto fail;
+	}
+
+	/* add overflow pages to free list */
+	if (F_ISSET(leaf->mn_flags, F_BIGDATA)) {
+		MDB_page *omp;
+		pgno_t pg;
+
+		memcpy(&pg, NODEDATA(leaf), sizeof(pg));
+		if ((rc = mdb_page_get(mc, pg, &omp, NULL)) ||
+			(rc = mdb_ovpage_free(mc, omp)))
+			goto fail;
+	}
+
+del_key:
+	return mdb_cursor_del0(mc);
+
+fail:
+	mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+	return rc;
+}
+
+/** Allocate and initialize new pages for a database.
+ * Set #MDB_TXN_ERROR on failure.
+ * @param[in] mc a cursor on the database being added to.
+ * @param[in] flags flags defining what type of page is being allocated.
+ * @param[in] num the number of pages to allocate. This is usually 1,
+ * unless allocating overflow pages for a large record.
+ * @param[out] mp Address of a page, or NULL on failure.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_new(MDB_cursor *mc, uint32_t flags, int num, MDB_page **mp)
+{
+	MDB_page	*np;
+	int rc;
+
+	if ((rc = mdb_page_alloc(mc, num, &np)))
+		return rc;
+	DPRINTF(("allocated new mpage %"Z"u, page size %u",
+	    np->mp_pgno, mc->mc_txn->mt_env->me_psize));
+	np->mp_flags = flags | P_DIRTY;
+	np->mp_lower = (PAGEHDRSZ-PAGEBASE);
+	np->mp_upper = mc->mc_txn->mt_env->me_psize - PAGEBASE;
+
+	if (IS_BRANCH(np))
+		mc->mc_db->md_branch_pages++;
+	else if (IS_LEAF(np))
+		mc->mc_db->md_leaf_pages++;
+	else if (IS_OVERFLOW(np)) {
+		mc->mc_db->md_overflow_pages += num;
+		np->mp_pages = num;
+	}
+	*mp = np;
+
+	return 0;
+}
+
+/** Calculate the size of a leaf node.
+ * The size depends on the environment's page size; if a data item
+ * is too large it will be put onto an overflow page and the node
+ * size will only include the key and not the data. Sizes are always
+ * rounded up to an even number of bytes, to guarantee 2-byte alignment
+ * of the #MDB_node headers.
+ * @param[in] env The environment handle.
+ * @param[in] key The key for the node.
+ * @param[in] data The data for the node.
+ * @return The number of bytes needed to store the node.
+ */
+static size_t
+mdb_leaf_size(MDB_env *env, MDB_val *key, MDB_val *data)
+{
+	size_t		 sz;
+
+	sz = LEAFSIZE(key, data);
+	if (sz > env->me_nodemax) {
+		/* put on overflow page */
+		sz -= data->mv_size - sizeof(pgno_t);
+	}
+
+	return EVEN(sz + sizeof(indx_t));
+}
+
+/** Calculate the size of a branch node.
+ * The size should depend on the environment's page size but since
+ * we currently don't support spilling large keys onto overflow
+ * pages, it's simply the size of the #MDB_node header plus the
+ * size of the key. Sizes are always rounded up to an even number
+ * of bytes, to guarantee 2-byte alignment of the #MDB_node headers.
+ * @param[in] env The environment handle.
+ * @param[in] key The key for the node.
+ * @return The number of bytes needed to store the node.
+ */
+static size_t
+mdb_branch_size(MDB_env *env, MDB_val *key)
+{
+	size_t		 sz;
+
+	sz = INDXSIZE(key);
+	if (sz > env->me_nodemax) {
+		/* put on overflow page */
+		/* not implemented */
+		/* sz -= key->size - sizeof(pgno_t); */
+	}
+
+	return sz + sizeof(indx_t);
+}
+
+/** Add a node to the page pointed to by the cursor.
+ * Set #MDB_TXN_ERROR on failure.
+ * @param[in] mc The cursor for this operation.
+ * @param[in] indx The index on the page where the new node should be added.
+ * @param[in] key The key for the new node.
+ * @param[in] data The data for the new node, if any.
+ * @param[in] pgno The page number, if adding a branch node.
+ * @param[in] flags Flags for the node.
+ * @return 0 on success, non-zero on failure. Possible errors are:
+ * <ul>
+ *	<li>ENOMEM - failed to allocate overflow pages for the node.
+ *	<li>MDB_PAGE_FULL - there is insufficient room in the page. This error
+ *	should never happen since all callers already calculate the
+ *	page's free space before calling this function.
+ * </ul>
+ */
+static int
+mdb_node_add(MDB_cursor *mc, indx_t indx,
+    MDB_val *key, MDB_val *data, pgno_t pgno, unsigned int flags)
+{
+	unsigned int	 i;
+	size_t		 node_size = NODESIZE;
+	ssize_t		 room;
+	indx_t		 ofs;
+	MDB_node	*node;
+	MDB_page	*mp = mc->mc_pg[mc->mc_top];
+	MDB_page	*ofp = NULL;		/* overflow page */
+	void		*ndata;
+	DKBUF;
+
+	mdb_cassert(mc, mp->mp_upper >= mp->mp_lower);
+
+	DPRINTF(("add to %s %spage %"Z"u index %i, data size %"Z"u key size %"Z"u [%s]",
+	    IS_LEAF(mp) ? "leaf" : "branch",
+		IS_SUBP(mp) ? "sub-" : "",
+		mdb_dbg_pgno(mp), indx, data ? data->mv_size : 0,
+		key ? key->mv_size : 0, key ? DKEY(key) : "null"));
+
+	if (IS_LEAF2(mp)) {
+		/* Move higher keys up one slot. */
+		int ksize = mc->mc_db->md_pad, dif;
+		char *ptr = LEAF2KEY(mp, indx, ksize);
+		dif = NUMKEYS(mp) - indx;
+		if (dif > 0)
+			memmove(ptr+ksize, ptr, dif*ksize);
+		/* insert new key */
+		memcpy(ptr, key->mv_data, ksize);
+
+		/* Just using these for counting */
+		mp->mp_lower += sizeof(indx_t);
+		mp->mp_upper -= ksize - sizeof(indx_t);
+		return MDB_SUCCESS;
+	}
+
+	room = (ssize_t)SIZELEFT(mp) - (ssize_t)sizeof(indx_t);
+	if (key != NULL)
+		node_size += key->mv_size;
+	if (IS_LEAF(mp)) {
+		mdb_cassert(mc, key && data);
+		if (F_ISSET(flags, F_BIGDATA)) {
+			/* Data already on overflow page. */
+			node_size += sizeof(pgno_t);
+		} else if (node_size + data->mv_size > mc->mc_txn->mt_env->me_nodemax) {
+			int ovpages = OVPAGES(data->mv_size, mc->mc_txn->mt_env->me_psize);
+			int rc;
+			/* Put data on overflow page. */
+			DPRINTF(("data size is %"Z"u, node would be %"Z"u, put data on overflow page",
+			    data->mv_size, node_size+data->mv_size));
+			node_size = EVEN(node_size + sizeof(pgno_t));
+			if ((ssize_t)node_size > room)
+				goto full;
+			if ((rc = mdb_page_new(mc, P_OVERFLOW, ovpages, &ofp)))
+				return rc;
+			DPRINTF(("allocated overflow page %"Z"u", ofp->mp_pgno));
+			flags |= F_BIGDATA;
+			goto update;
+		} else {
+			node_size += data->mv_size;
+		}
+	}
+	node_size = EVEN(node_size);
+	if ((ssize_t)node_size > room)
+		goto full;
+
+update:
+	/* Move higher pointers up one slot. */
+	for (i = NUMKEYS(mp); i > indx; i--)
+		mp->mp_ptrs[i] = mp->mp_ptrs[i - 1];
+
+	/* Adjust free space offsets. */
+	ofs = mp->mp_upper - node_size;
+	mdb_cassert(mc, ofs >= mp->mp_lower + sizeof(indx_t));
+	mp->mp_ptrs[indx] = ofs;
+	mp->mp_upper = ofs;
+	mp->mp_lower += sizeof(indx_t);
+
+	/* Write the node data. */
+	node = NODEPTR(mp, indx);
+	node->mn_ksize = (key == NULL) ? 0 : key->mv_size;
+	node->mn_flags = flags;
+	if (IS_LEAF(mp))
+		SETDSZ(node,data->mv_size);
+	else
+		SETPGNO(node,pgno);
+
+	if (key)
+		memcpy(NODEKEY(node), key->mv_data, key->mv_size);
+
+	if (IS_LEAF(mp)) {
+		ndata = NODEDATA(node);
+		if (ofp == NULL) {
+			if (F_ISSET(flags, F_BIGDATA))
+				memcpy(ndata, data->mv_data, sizeof(pgno_t));
+			else if (F_ISSET(flags, MDB_RESERVE))
+				data->mv_data = ndata;
+			else
+				memcpy(ndata, data->mv_data, data->mv_size);
+		} else {
+			memcpy(ndata, &ofp->mp_pgno, sizeof(pgno_t));
+			ndata = METADATA(ofp);
+			if (F_ISSET(flags, MDB_RESERVE))
+				data->mv_data = ndata;
+			else
+				memcpy(ndata, data->mv_data, data->mv_size);
+		}
+	}
+
+	return MDB_SUCCESS;
+
+full:
+	DPRINTF(("not enough room in page %"Z"u, got %u ptrs",
+		mdb_dbg_pgno(mp), NUMKEYS(mp)));
+	DPRINTF(("upper-lower = %u - %u = %"Z"d", mp->mp_upper,mp->mp_lower,room));
+	DPRINTF(("node size = %"Z"u", node_size));
+	mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+	return MDB_PAGE_FULL;
+}
+
+/** Delete the specified node from a page.
+ * @param[in] mc Cursor pointing to the node to delete.
+ * @param[in] ksize The size of a node. Only used if the page is
+ * part of a #MDB_DUPFIXED database.
+ */
+static void
+mdb_node_del(MDB_cursor *mc, int ksize)
+{
+	MDB_page *mp = mc->mc_pg[mc->mc_top];
+	indx_t	indx = mc->mc_ki[mc->mc_top];
+	unsigned int	 sz;
+	indx_t		 i, j, numkeys, ptr;
+	MDB_node	*node;
+	char		*base;
+
+	DPRINTF(("delete node %u on %s page %"Z"u", indx,
+	    IS_LEAF(mp) ? "leaf" : "branch", mdb_dbg_pgno(mp)));
+	numkeys = NUMKEYS(mp);
+	mdb_cassert(mc, indx < numkeys);
+
+	if (IS_LEAF2(mp)) {
+		int x = numkeys - 1 - indx;
+		base = LEAF2KEY(mp, indx, ksize);
+		if (x)
+			memmove(base, base + ksize, x * ksize);
+		mp->mp_lower -= sizeof(indx_t);
+		mp->mp_upper += ksize - sizeof(indx_t);
+		return;
+	}
+
+	node = NODEPTR(mp, indx);
+	sz = NODESIZE + node->mn_ksize;
+	if (IS_LEAF(mp)) {
+		if (F_ISSET(node->mn_flags, F_BIGDATA))
+			sz += sizeof(pgno_t);
+		else
+			sz += NODEDSZ(node);
+	}
+	sz = EVEN(sz);
+
+	ptr = mp->mp_ptrs[indx];
+	for (i = j = 0; i < numkeys; i++) {
+		if (i != indx) {
+			mp->mp_ptrs[j] = mp->mp_ptrs[i];
+			if (mp->mp_ptrs[i] < ptr)
+				mp->mp_ptrs[j] += sz;
+			j++;
+		}
+	}
+
+	base = (char *)mp + mp->mp_upper + PAGEBASE;
+	memmove(base + sz, base, ptr - mp->mp_upper);
+
+	mp->mp_lower -= sizeof(indx_t);
+	mp->mp_upper += sz;
+}
+
+/** Compact the main page after deleting a node on a subpage.
+ * @param[in] mp The main page to operate on.
+ * @param[in] indx The index of the subpage on the main page.
+ */
+static void
+mdb_node_shrink(MDB_page *mp, indx_t indx)
+{
+	MDB_node *node;
+	MDB_page *sp, *xp;
+	char *base;
+	indx_t delta, nsize, len, ptr;
+	int i;
+
+	node = NODEPTR(mp, indx);
+	sp = (MDB_page *)NODEDATA(node);
+	delta = SIZELEFT(sp);
+	nsize = NODEDSZ(node) - delta;
+
+	/* Prepare to shift upward, set len = length(subpage part to shift) */
+	if (IS_LEAF2(sp)) {
+		len = nsize;
+		if (nsize & 1)
+			return;		/* do not make the node uneven-sized */
+	} else {
+		xp = (MDB_page *)((char *)sp + delta); /* destination subpage */
+		for (i = NUMKEYS(sp); --i >= 0; )
+			xp->mp_ptrs[i] = sp->mp_ptrs[i] - delta;
+		len = PAGEHDRSZ;
+	}
+	sp->mp_upper = sp->mp_lower;
+	COPY_PGNO(sp->mp_pgno, mp->mp_pgno);
+	SETDSZ(node, nsize);
+
+	/* Shift <lower nodes...initial part of subpage> upward */
+	base = (char *)mp + mp->mp_upper + PAGEBASE;
+	memmove(base + delta, base, (char *)sp + len - base);
+
+	ptr = mp->mp_ptrs[indx];
+	for (i = NUMKEYS(mp); --i >= 0; ) {
+		if (mp->mp_ptrs[i] <= ptr)
+			mp->mp_ptrs[i] += delta;
+	}
+	mp->mp_upper += delta;
+}
+
+/** Initial setup of a sorted-dups cursor.
+ * Sorted duplicates are implemented as a sub-database for the given key.
+ * The duplicate data items are actually keys of the sub-database.
+ * Operations on the duplicate data items are performed using a sub-cursor
+ * initialized when the sub-database is first accessed. This function does
+ * the preliminary setup of the sub-cursor, filling in the fields that
+ * depend only on the parent DB.
+ * @param[in] mc The main cursor whose sorted-dups cursor is to be initialized.
+ */
+static void
+mdb_xcursor_init0(MDB_cursor *mc)
+{
+	MDB_xcursor *mx = mc->mc_xcursor;
+
+	mx->mx_cursor.mc_xcursor = NULL;
+	mx->mx_cursor.mc_txn = mc->mc_txn;
+	mx->mx_cursor.mc_db = &mx->mx_db;
+	mx->mx_cursor.mc_dbx = &mx->mx_dbx;
+	mx->mx_cursor.mc_dbi = mc->mc_dbi;
+	mx->mx_cursor.mc_dbflag = &mx->mx_dbflag;
+	mx->mx_cursor.mc_snum = 0;
+	mx->mx_cursor.mc_top = 0;
+	mx->mx_cursor.mc_flags = C_SUB;
+	mx->mx_dbx.md_name.mv_size = 0;
+	mx->mx_dbx.md_name.mv_data = NULL;
+	mx->mx_dbx.md_cmp = mc->mc_dbx->md_dcmp;
+	mx->mx_dbx.md_dcmp = NULL;
+	mx->mx_dbx.md_rel = mc->mc_dbx->md_rel;
+}
+
+/** Final setup of a sorted-dups cursor.
+ *	Sets up the fields that depend on the data from the main cursor.
+ * @param[in] mc The main cursor whose sorted-dups cursor is to be initialized.
+ * @param[in] node The data containing the #MDB_db record for the
+ * sorted-dup database.
+ */
+static void
+mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node)
+{
+	MDB_xcursor *mx = mc->mc_xcursor;
+
+	if (node->mn_flags & F_SUBDATA) {
+		memcpy(&mx->mx_db, NODEDATA(node), sizeof(MDB_db));
+		mx->mx_cursor.mc_pg[0] = 0;
+		mx->mx_cursor.mc_snum = 0;
+		mx->mx_cursor.mc_top = 0;
+		mx->mx_cursor.mc_flags = C_SUB;
+	} else {
+		MDB_page *fp = NODEDATA(node);
+		mx->mx_db.md_pad = 0;
+		mx->mx_db.md_flags = 0;
+		mx->mx_db.md_depth = 1;
+		mx->mx_db.md_branch_pages = 0;
+		mx->mx_db.md_leaf_pages = 1;
+		mx->mx_db.md_overflow_pages = 0;
+		mx->mx_db.md_entries = NUMKEYS(fp);
+		COPY_PGNO(mx->mx_db.md_root, fp->mp_pgno);
+		mx->mx_cursor.mc_snum = 1;
+		mx->mx_cursor.mc_top = 0;
+		mx->mx_cursor.mc_flags = C_INITIALIZED|C_SUB;
+		mx->mx_cursor.mc_pg[0] = fp;
+		mx->mx_cursor.mc_ki[0] = 0;
+		if (mc->mc_db->md_flags & MDB_DUPFIXED) {
+			mx->mx_db.md_flags = MDB_DUPFIXED;
+			mx->mx_db.md_pad = fp->mp_pad;
+			if (mc->mc_db->md_flags & MDB_INTEGERDUP)
+				mx->mx_db.md_flags |= MDB_INTEGERKEY;
+		}
+	}
+	DPRINTF(("Sub-db -%u root page %"Z"u", mx->mx_cursor.mc_dbi,
+		mx->mx_db.md_root));
+	mx->mx_dbflag = DB_VALID|DB_USRVALID|DB_DUPDATA;
+#if UINT_MAX < SIZE_MAX
+	if (mx->mx_dbx.md_cmp == mdb_cmp_int && mx->mx_db.md_pad == sizeof(size_t))
+		mx->mx_dbx.md_cmp = mdb_cmp_clong;
+#endif
+}
+
+
+/** Fixup a sorted-dups cursor due to underlying update.
+ *	Sets up some fields that depend on the data from the main cursor.
+ *	Almost the same as init1, but skips initialization steps if the
+ *	xcursor had already been used.
+ * @param[in] mc The main cursor whose sorted-dups cursor is to be fixed up.
+ * @param[in] src_mx The xcursor of an up-to-date cursor.
+ * @param[in] new_dupdata True if converting from a non-#F_DUPDATA item.
+ */
+static void
+mdb_xcursor_init2(MDB_cursor *mc, MDB_xcursor *src_mx, int new_dupdata)
+{
+	MDB_xcursor *mx = mc->mc_xcursor;
+
+	if (new_dupdata) {
+		mx->mx_cursor.mc_snum = 1;
+		mx->mx_cursor.mc_top = 0;
+		mx->mx_cursor.mc_flags |= C_INITIALIZED;
+		mx->mx_cursor.mc_ki[0] = 0;
+		mx->mx_dbflag = DB_VALID|DB_USRVALID|DB_DUPDATA;
+#if UINT_MAX < SIZE_MAX
+		mx->mx_dbx.md_cmp = src_mx->mx_dbx.md_cmp;
+#endif
+	} else if (!(mx->mx_cursor.mc_flags & C_INITIALIZED)) {
+		return;
+	}
+	mx->mx_db = src_mx->mx_db;
+	mx->mx_cursor.mc_pg[0] = src_mx->mx_cursor.mc_pg[0];
+	DPRINTF(("Sub-db -%u root page %"Z"u", mx->mx_cursor.mc_dbi,
+		mx->mx_db.md_root));
+}
+
+/** Initialize a cursor for a given transaction and database. */
+static void
+mdb_cursor_init(MDB_cursor *mc, MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx)
+{
+	mc->mc_next = NULL;
+	mc->mc_backup = NULL;
+	mc->mc_dbi = dbi;
+	mc->mc_txn = txn;
+	mc->mc_db = &txn->mt_dbs[dbi];
+	mc->mc_dbx = &txn->mt_dbxs[dbi];
+	mc->mc_dbflag = &txn->mt_dbflags[dbi];
+	mc->mc_snum = 0;
+	mc->mc_top = 0;
+	mc->mc_pg[0] = 0;
+	mc->mc_ki[0] = 0;
+	mc->mc_flags = 0;
+	if (txn->mt_dbs[dbi].md_flags & MDB_DUPSORT) {
+		mdb_tassert(txn, mx != NULL);
+		mc->mc_xcursor = mx;
+		mdb_xcursor_init0(mc);
+	} else {
+		mc->mc_xcursor = NULL;
+	}
+	if (*mc->mc_dbflag & DB_STALE) {
+		mdb_page_search(mc, NULL, MDB_PS_ROOTONLY);
+	}
+}
+
+int
+mdb_cursor_open(MDB_txn *txn, MDB_dbi dbi, MDB_cursor **ret)
+{
+	MDB_cursor	*mc;
+	size_t size = sizeof(MDB_cursor);
+
+	if (!ret || !TXN_DBI_EXIST(txn, dbi, DB_VALID))
+		return EINVAL;
+
+	if (txn->mt_flags & MDB_TXN_BLOCKED)
+		return MDB_BAD_TXN;
+
+	if (dbi == FREE_DBI && !F_ISSET(txn->mt_flags, MDB_TXN_RDONLY))
+		return EINVAL;
+
+	if (txn->mt_dbs[dbi].md_flags & MDB_DUPSORT)
+		size += sizeof(MDB_xcursor);
+
+	if ((mc = malloc(size)) != NULL) {
+		mdb_cursor_init(mc, txn, dbi, (MDB_xcursor *)(mc + 1));
+		if (txn->mt_cursors) {
+			mc->mc_next = txn->mt_cursors[dbi];
+			txn->mt_cursors[dbi] = mc;
+			mc->mc_flags |= C_UNTRACK;
+		}
+	} else {
+		return ENOMEM;
+	}
+
+	*ret = mc;
+
+	return MDB_SUCCESS;
+}
+
+int
+mdb_cursor_renew(MDB_txn *txn, MDB_cursor *mc)
+{
+	if (!mc || !TXN_DBI_EXIST(txn, mc->mc_dbi, DB_VALID))
+		return EINVAL;
+
+	if ((mc->mc_flags & C_UNTRACK) || txn->mt_cursors)
+		return EINVAL;
+
+	if (txn->mt_flags & MDB_TXN_BLOCKED)
+		return MDB_BAD_TXN;
+
+	mdb_cursor_init(mc, txn, mc->mc_dbi, mc->mc_xcursor);
+	return MDB_SUCCESS;
+}
+
+/* Return the count of duplicate data items for the current key */
+int
+mdb_cursor_count(MDB_cursor *mc, size_t *countp)
+{
+	MDB_node	*leaf;
+
+	if (mc == NULL || countp == NULL)
+		return EINVAL;
+
+	if (mc->mc_xcursor == NULL)
+		return MDB_INCOMPATIBLE;
+
+	if (mc->mc_txn->mt_flags & MDB_TXN_BLOCKED)
+		return MDB_BAD_TXN;
+
+	if (!(mc->mc_flags & C_INITIALIZED))
+		return EINVAL;
+
+	if (!mc->mc_snum)
+		return MDB_NOTFOUND;
+
+	if (mc->mc_flags & C_EOF) {
+		if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mc->mc_pg[mc->mc_top]))
+			return MDB_NOTFOUND;
+		mc->mc_flags ^= C_EOF;
+	}
+
+	leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+	if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		*countp = 1;
+	} else {
+		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED))
+			return EINVAL;
+
+		*countp = mc->mc_xcursor->mx_db.md_entries;
+	}
+	return MDB_SUCCESS;
+}
+
+void
+mdb_cursor_close(MDB_cursor *mc)
+{
+	if (mc && !mc->mc_backup) {
+		/* remove from txn, if tracked */
+		if ((mc->mc_flags & C_UNTRACK) && mc->mc_txn->mt_cursors) {
+			MDB_cursor **prev = &mc->mc_txn->mt_cursors[mc->mc_dbi];
+			while (*prev && *prev != mc) prev = &(*prev)->mc_next;
+			if (*prev == mc)
+				*prev = mc->mc_next;
+		}
+		free(mc);
+	}
+}
+
+MDB_txn *
+mdb_cursor_txn(MDB_cursor *mc)
+{
+	if (!mc) return NULL;
+	return mc->mc_txn;
+}
+
+MDB_dbi
+mdb_cursor_dbi(MDB_cursor *mc)
+{
+	return mc->mc_dbi;
+}
+
+/** Replace the key for a branch node with a new key.
+ * Set #MDB_TXN_ERROR on failure.
+ * @param[in] mc Cursor pointing to the node to operate on.
+ * @param[in] key The new key to use.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_update_key(MDB_cursor *mc, MDB_val *key)
+{
+	MDB_page		*mp;
+	MDB_node		*node;
+	char			*base;
+	size_t			 len;
+	int				 delta, ksize, oksize;
+	indx_t			 ptr, i, numkeys, indx;
+	DKBUF;
+
+	indx = mc->mc_ki[mc->mc_top];
+	mp = mc->mc_pg[mc->mc_top];
+	node = NODEPTR(mp, indx);
+	ptr = mp->mp_ptrs[indx];
+#if MDB_DEBUG
+	{
+		MDB_val	k2;
+		char kbuf2[DKBUF_MAXKEYSIZE*2+1];
+		k2.mv_data = NODEKEY(node);
+		k2.mv_size = node->mn_ksize;
+		DPRINTF(("update key %u (ofs %u) [%s] to [%s] on page %"Z"u",
+			indx, ptr,
+			mdb_dkey(&k2, kbuf2),
+			DKEY(key),
+			mp->mp_pgno));
+	}
+#endif
+
+	/* Sizes must be 2-byte aligned. */
+	ksize = EVEN(key->mv_size);
+	oksize = EVEN(node->mn_ksize);
+	delta = ksize - oksize;
+
+	/* Shift node contents if EVEN(key length) changed. */
+	if (delta) {
+		if (delta > 0 && SIZELEFT(mp) < delta) {
+			pgno_t pgno;
+			/* not enough space left, do a delete and split */
+			DPRINTF(("Not enough room, delta = %d, splitting...", delta));
+			pgno = NODEPGNO(node);
+			mdb_node_del(mc, 0);
+			return mdb_page_split(mc, key, NULL, pgno, MDB_SPLIT_REPLACE);
+		}
+
+		numkeys = NUMKEYS(mp);
+		for (i = 0; i < numkeys; i++) {
+			if (mp->mp_ptrs[i] <= ptr)
+				mp->mp_ptrs[i] -= delta;
+		}
+
+		base = (char *)mp + mp->mp_upper + PAGEBASE;
+		len = ptr - mp->mp_upper + NODESIZE;
+		memmove(base - delta, base, len);
+		mp->mp_upper -= delta;
+
+		node = NODEPTR(mp, indx);
+	}
+
+	/* But even if no shift was needed, update ksize */
+	if (node->mn_ksize != key->mv_size)
+		node->mn_ksize = key->mv_size;
+
+	if (key->mv_size)
+		memcpy(NODEKEY(node), key->mv_data, key->mv_size);
+
+	return MDB_SUCCESS;
+}
+
+static void
+mdb_cursor_copy(const MDB_cursor *csrc, MDB_cursor *cdst);
+
+/** Perform \b act while tracking temporary cursor \b mn */
+#define WITH_CURSOR_TRACKING(mn, act) do { \
+	MDB_cursor dummy, *tracked, **tp = &(mn).mc_txn->mt_cursors[mn.mc_dbi]; \
+	if ((mn).mc_flags & C_SUB) { \
+		dummy.mc_flags =  C_INITIALIZED; \
+		dummy.mc_xcursor = (MDB_xcursor *)&(mn);	\
+		tracked = &dummy; \
+	} else { \
+		tracked = &(mn); \
+	} \
+	tracked->mc_next = *tp; \
+	*tp = tracked; \
+	{ act; } \
+	*tp = tracked->mc_next; \
+} while (0)
+
+/** Move a node from csrc to cdst.
+ */
+static int
+mdb_node_move(MDB_cursor *csrc, MDB_cursor *cdst, int fromleft)
+{
+	MDB_node		*srcnode;
+	MDB_val		 key, data;
+	pgno_t	srcpg;
+	MDB_cursor mn;
+	int			 rc;
+	unsigned short flags;
+
+	DKBUF;
+
+	/* Mark src and dst as dirty. */
+	if ((rc = mdb_page_touch(csrc)) ||
+	    (rc = mdb_page_touch(cdst)))
+		return rc;
+
+	if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+		key.mv_size = csrc->mc_db->md_pad;
+		key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], csrc->mc_ki[csrc->mc_top], key.mv_size);
+		data.mv_size = 0;
+		data.mv_data = NULL;
+		srcpg = 0;
+		flags = 0;
+	} else {
+		srcnode = NODEPTR(csrc->mc_pg[csrc->mc_top], csrc->mc_ki[csrc->mc_top]);
+		mdb_cassert(csrc, !((size_t)srcnode & 1));
+		srcpg = NODEPGNO(srcnode);
+		flags = srcnode->mn_flags;
+		if (csrc->mc_ki[csrc->mc_top] == 0 && IS_BRANCH(csrc->mc_pg[csrc->mc_top])) {
+			unsigned int snum = csrc->mc_snum;
+			MDB_node *s2;
+			/* must find the lowest key below src */
+			rc = mdb_page_search_lowest(csrc);
+			if (rc)
+				return rc;
+			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+				key.mv_size = csrc->mc_db->md_pad;
+				key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], 0, key.mv_size);
+			} else {
+				s2 = NODEPTR(csrc->mc_pg[csrc->mc_top], 0);
+				key.mv_size = NODEKSZ(s2);
+				key.mv_data = NODEKEY(s2);
+			}
+			csrc->mc_snum = snum--;
+			csrc->mc_top = snum;
+		} else {
+			key.mv_size = NODEKSZ(srcnode);
+			key.mv_data = NODEKEY(srcnode);
+		}
+		data.mv_size = NODEDSZ(srcnode);
+		data.mv_data = NODEDATA(srcnode);
+	}
+	mn.mc_xcursor = NULL;
+	if (IS_BRANCH(cdst->mc_pg[cdst->mc_top]) && cdst->mc_ki[cdst->mc_top] == 0) {
+		unsigned int snum = cdst->mc_snum;
+		MDB_node *s2;
+		MDB_val bkey;
+		/* must find the lowest key below dst */
+		mdb_cursor_copy(cdst, &mn);
+		rc = mdb_page_search_lowest(&mn);
+		if (rc)
+			return rc;
+		if (IS_LEAF2(mn.mc_pg[mn.mc_top])) {
+			bkey.mv_size = mn.mc_db->md_pad;
+			bkey.mv_data = LEAF2KEY(mn.mc_pg[mn.mc_top], 0, bkey.mv_size);
+		} else {
+			s2 = NODEPTR(mn.mc_pg[mn.mc_top], 0);
+			bkey.mv_size = NODEKSZ(s2);
+			bkey.mv_data = NODEKEY(s2);
+		}
+		mn.mc_snum = snum--;
+		mn.mc_top = snum;
+		mn.mc_ki[snum] = 0;
+		rc = mdb_update_key(&mn, &bkey);
+		if (rc)
+			return rc;
+	}
+
+	DPRINTF(("moving %s node %u [%s] on page %"Z"u to node %u on page %"Z"u",
+	    IS_LEAF(csrc->mc_pg[csrc->mc_top]) ? "leaf" : "branch",
+	    csrc->mc_ki[csrc->mc_top],
+		DKEY(&key),
+	    csrc->mc_pg[csrc->mc_top]->mp_pgno,
+	    cdst->mc_ki[cdst->mc_top], cdst->mc_pg[cdst->mc_top]->mp_pgno));
+
+	/* Add the node to the destination page.
+	 */
+	rc = mdb_node_add(cdst, cdst->mc_ki[cdst->mc_top], &key, &data, srcpg, flags);
+	if (rc != MDB_SUCCESS)
+		return rc;
+
+	/* Delete the node from the source page.
+	 */
+	mdb_node_del(csrc, key.mv_size);
+
+	{
+		/* Adjust other cursors pointing to mp */
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = csrc->mc_dbi;
+		MDB_page *mpd, *mps;
+
+		mps = csrc->mc_pg[csrc->mc_top];
+		/* If we're adding on the left, bump others up */
+		if (fromleft) {
+			mpd = cdst->mc_pg[csrc->mc_top];
+			for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+				if (csrc->mc_flags & C_SUB)
+					m3 = &m2->mc_xcursor->mx_cursor;
+				else
+					m3 = m2;
+				if (!(m3->mc_flags & C_INITIALIZED) || m3->mc_top < csrc->mc_top)
+					continue;
+				if (m3 != cdst &&
+					m3->mc_pg[csrc->mc_top] == mpd &&
+					m3->mc_ki[csrc->mc_top] >= cdst->mc_ki[csrc->mc_top]) {
+					m3->mc_ki[csrc->mc_top]++;
+				}
+				if (m3 !=csrc &&
+					m3->mc_pg[csrc->mc_top] == mps &&
+					m3->mc_ki[csrc->mc_top] == csrc->mc_ki[csrc->mc_top]) {
+					m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
+					m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+					m3->mc_ki[csrc->mc_top-1]++;
+				}
+				if (IS_LEAF(mps))
+					XCURSOR_REFRESH(m3, csrc->mc_top, m3->mc_pg[csrc->mc_top]);
+			}
+		} else
+		/* Adding on the right, bump others down */
+		{
+			for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+				if (csrc->mc_flags & C_SUB)
+					m3 = &m2->mc_xcursor->mx_cursor;
+				else
+					m3 = m2;
+				if (m3 == csrc) continue;
+				if (!(m3->mc_flags & C_INITIALIZED) || m3->mc_top < csrc->mc_top)
+					continue;
+				if (m3->mc_pg[csrc->mc_top] == mps) {
+					if (!m3->mc_ki[csrc->mc_top]) {
+						m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
+						m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+						m3->mc_ki[csrc->mc_top-1]--;
+					} else {
+						m3->mc_ki[csrc->mc_top]--;
+					}
+					if (IS_LEAF(mps))
+						XCURSOR_REFRESH(m3, csrc->mc_top, m3->mc_pg[csrc->mc_top]);
+				}
+			}
+		}
+	}
+
+	/* Update the parent separators.
+	 */
+	if (csrc->mc_ki[csrc->mc_top] == 0) {
+		if (csrc->mc_ki[csrc->mc_top-1] != 0) {
+			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+				key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], 0, key.mv_size);
+			} else {
+				srcnode = NODEPTR(csrc->mc_pg[csrc->mc_top], 0);
+				key.mv_size = NODEKSZ(srcnode);
+				key.mv_data = NODEKEY(srcnode);
+			}
+			DPRINTF(("update separator for source page %"Z"u to [%s]",
+				csrc->mc_pg[csrc->mc_top]->mp_pgno, DKEY(&key)));
+			mdb_cursor_copy(csrc, &mn);
+			mn.mc_snum--;
+			mn.mc_top--;
+			/* We want mdb_rebalance to find mn when doing fixups */
+			WITH_CURSOR_TRACKING(mn,
+				rc = mdb_update_key(&mn, &key));
+			if (rc)
+				return rc;
+		}
+		if (IS_BRANCH(csrc->mc_pg[csrc->mc_top])) {
+			MDB_val	 nullkey;
+			indx_t	ix = csrc->mc_ki[csrc->mc_top];
+			nullkey.mv_size = 0;
+			csrc->mc_ki[csrc->mc_top] = 0;
+			rc = mdb_update_key(csrc, &nullkey);
+			csrc->mc_ki[csrc->mc_top] = ix;
+			mdb_cassert(csrc, rc == MDB_SUCCESS);
+		}
+	}
+
+	if (cdst->mc_ki[cdst->mc_top] == 0) {
+		if (cdst->mc_ki[cdst->mc_top-1] != 0) {
+			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
+				key.mv_data = LEAF2KEY(cdst->mc_pg[cdst->mc_top], 0, key.mv_size);
+			} else {
+				srcnode = NODEPTR(cdst->mc_pg[cdst->mc_top], 0);
+				key.mv_size = NODEKSZ(srcnode);
+				key.mv_data = NODEKEY(srcnode);
+			}
+			DPRINTF(("update separator for destination page %"Z"u to [%s]",
+				cdst->mc_pg[cdst->mc_top]->mp_pgno, DKEY(&key)));
+			mdb_cursor_copy(cdst, &mn);
+			mn.mc_snum--;
+			mn.mc_top--;
+			/* We want mdb_rebalance to find mn when doing fixups */
+			WITH_CURSOR_TRACKING(mn,
+				rc = mdb_update_key(&mn, &key));
+			if (rc)
+				return rc;
+		}
+		if (IS_BRANCH(cdst->mc_pg[cdst->mc_top])) {
+			MDB_val	 nullkey;
+			indx_t	ix = cdst->mc_ki[cdst->mc_top];
+			nullkey.mv_size = 0;
+			cdst->mc_ki[cdst->mc_top] = 0;
+			rc = mdb_update_key(cdst, &nullkey);
+			cdst->mc_ki[cdst->mc_top] = ix;
+			mdb_cassert(cdst, rc == MDB_SUCCESS);
+		}
+	}
+
+	return MDB_SUCCESS;
+}
+
+/** Merge one page into another.
+ *  The nodes from the page pointed to by \b csrc will
+ *	be copied to the page pointed to by \b cdst and then
+ *	the \b csrc page will be freed.
+ * @param[in] csrc Cursor pointing to the source page.
+ * @param[in] cdst Cursor pointing to the destination page.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst)
+{
+	MDB_page	*psrc, *pdst;
+	MDB_node	*srcnode;
+	MDB_val		 key, data;
+	unsigned	 nkeys;
+	int			 rc;
+	indx_t		 i, j;
+
+	psrc = csrc->mc_pg[csrc->mc_top];
+	pdst = cdst->mc_pg[cdst->mc_top];
+
+	DPRINTF(("merging page %"Z"u into %"Z"u", psrc->mp_pgno, pdst->mp_pgno));
+
+	mdb_cassert(csrc, csrc->mc_snum > 1);	/* can't merge root page */
+	mdb_cassert(csrc, cdst->mc_snum > 1);
+
+	/* Mark dst as dirty. */
+	if ((rc = mdb_page_touch(cdst)))
+		return rc;
+
+	/* get dst page again now that we've touched it. */
+	pdst = cdst->mc_pg[cdst->mc_top];
+
+	/* Move all nodes from src to dst.
+	 */
+	j = nkeys = NUMKEYS(pdst);
+	if (IS_LEAF2(psrc)) {
+		key.mv_size = csrc->mc_db->md_pad;
+		key.mv_data = METADATA(psrc);
+		for (i = 0; i < NUMKEYS(psrc); i++, j++) {
+			rc = mdb_node_add(cdst, j, &key, NULL, 0, 0);
+			if (rc != MDB_SUCCESS)
+				return rc;
+			key.mv_data = (char *)key.mv_data + key.mv_size;
+		}
+	} else {
+		for (i = 0; i < NUMKEYS(psrc); i++, j++) {
+			srcnode = NODEPTR(psrc, i);
+			if (i == 0 && IS_BRANCH(psrc)) {
+				MDB_cursor mn;
+				MDB_node *s2;
+				mdb_cursor_copy(csrc, &mn);
+				mn.mc_xcursor = NULL;
+				/* must find the lowest key below src */
+				rc = mdb_page_search_lowest(&mn);
+				if (rc)
+					return rc;
+				if (IS_LEAF2(mn.mc_pg[mn.mc_top])) {
+					key.mv_size = mn.mc_db->md_pad;
+					key.mv_data = LEAF2KEY(mn.mc_pg[mn.mc_top], 0, key.mv_size);
+				} else {
+					s2 = NODEPTR(mn.mc_pg[mn.mc_top], 0);
+					key.mv_size = NODEKSZ(s2);
+					key.mv_data = NODEKEY(s2);
+				}
+			} else {
+				key.mv_size = srcnode->mn_ksize;
+				key.mv_data = NODEKEY(srcnode);
+			}
+
+			data.mv_size = NODEDSZ(srcnode);
+			data.mv_data = NODEDATA(srcnode);
+			rc = mdb_node_add(cdst, j, &key, &data, NODEPGNO(srcnode), srcnode->mn_flags);
+			if (rc != MDB_SUCCESS)
+				return rc;
+		}
+	}
+
+	DPRINTF(("dst page %"Z"u now has %u keys (%.1f%% filled)",
+	    pdst->mp_pgno, NUMKEYS(pdst),
+		(float)PAGEFILL(cdst->mc_txn->mt_env, pdst) / 10));
+
+	/* Unlink the src page from parent and add to free list.
+	 */
+	csrc->mc_top--;
+	mdb_node_del(csrc, 0);
+	if (csrc->mc_ki[csrc->mc_top] == 0) {
+		key.mv_size = 0;
+		rc = mdb_update_key(csrc, &key);
+		if (rc) {
+			csrc->mc_top++;
+			return rc;
+		}
+	}
+	csrc->mc_top++;
+
+	psrc = csrc->mc_pg[csrc->mc_top];
+	/* If not operating on FreeDB, allow this page to be reused
+	 * in this txn. Otherwise just add to free list.
+	 */
+	rc = mdb_page_loose(csrc, psrc);
+	if (rc)
+		return rc;
+	if (IS_LEAF(psrc))
+		csrc->mc_db->md_leaf_pages--;
+	else
+		csrc->mc_db->md_branch_pages--;
+	{
+		/* Adjust other cursors pointing to mp */
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = csrc->mc_dbi;
+		unsigned int top = csrc->mc_top;
+
+		for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			if (csrc->mc_flags & C_SUB)
+				m3 = &m2->mc_xcursor->mx_cursor;
+			else
+				m3 = m2;
+			if (m3 == csrc) continue;
+			if (m3->mc_snum < csrc->mc_snum) continue;
+			if (m3->mc_pg[top] == psrc) {
+				m3->mc_pg[top] = pdst;
+				m3->mc_ki[top] += nkeys;
+				m3->mc_ki[top-1] = cdst->mc_ki[top-1];
+			} else if (m3->mc_pg[top-1] == csrc->mc_pg[top-1] &&
+				m3->mc_ki[top-1] > csrc->mc_ki[top-1]) {
+				m3->mc_ki[top-1]--;
+			}
+			if (IS_LEAF(psrc))
+				XCURSOR_REFRESH(m3, top, m3->mc_pg[top]);
+		}
+	}
+	{
+		unsigned int snum = cdst->mc_snum;
+		uint16_t depth = cdst->mc_db->md_depth;
+		mdb_cursor_pop(cdst);
+		rc = mdb_rebalance(cdst);
+		/* Did the tree height change? */
+		if (depth != cdst->mc_db->md_depth)
+			snum += cdst->mc_db->md_depth - depth;
+		cdst->mc_snum = snum;
+		cdst->mc_top = snum-1;
+	}
+	return rc;
+}
+
+/** Copy the contents of a cursor.
+ * @param[in] csrc The cursor to copy from.
+ * @param[out] cdst The cursor to copy to.
+ */
+static void
+mdb_cursor_copy(const MDB_cursor *csrc, MDB_cursor *cdst)
+{
+	unsigned int i;
+
+	cdst->mc_txn = csrc->mc_txn;
+	cdst->mc_dbi = csrc->mc_dbi;
+	cdst->mc_db  = csrc->mc_db;
+	cdst->mc_dbx = csrc->mc_dbx;
+	cdst->mc_snum = csrc->mc_snum;
+	cdst->mc_top = csrc->mc_top;
+	cdst->mc_flags = csrc->mc_flags;
+
+	for (i=0; i<csrc->mc_snum; i++) {
+		cdst->mc_pg[i] = csrc->mc_pg[i];
+		cdst->mc_ki[i] = csrc->mc_ki[i];
+	}
+}
+
+/** Rebalance the tree after a delete operation.
+ * @param[in] mc Cursor pointing to the page where rebalancing
+ * should begin.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_rebalance(MDB_cursor *mc)
+{
+	MDB_node	*node;
+	int rc, fromleft;
+	unsigned int ptop, minkeys, thresh;
+	MDB_cursor	mn;
+	indx_t oldki;
+
+	if (IS_BRANCH(mc->mc_pg[mc->mc_top])) {
+		minkeys = 2;
+		thresh = 1;
+	} else {
+		minkeys = 1;
+		thresh = FILL_THRESHOLD;
+	}
+	DPRINTF(("rebalancing %s page %"Z"u (has %u keys, %.1f%% full)",
+	    IS_LEAF(mc->mc_pg[mc->mc_top]) ? "leaf" : "branch",
+	    mdb_dbg_pgno(mc->mc_pg[mc->mc_top]), NUMKEYS(mc->mc_pg[mc->mc_top]),
+		(float)PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) / 10));
+
+	if (PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) >= thresh &&
+		NUMKEYS(mc->mc_pg[mc->mc_top]) >= minkeys) {
+		DPRINTF(("no need to rebalance page %"Z"u, above fill threshold",
+		    mdb_dbg_pgno(mc->mc_pg[mc->mc_top])));
+		return MDB_SUCCESS;
+	}
+
+	if (mc->mc_snum < 2) {
+		MDB_page *mp = mc->mc_pg[0];
+		if (IS_SUBP(mp)) {
+			DPUTS("Can't rebalance a subpage, ignoring");
+			return MDB_SUCCESS;
+		}
+		if (NUMKEYS(mp) == 0) {
+			DPUTS("tree is completely empty");
+			mc->mc_db->md_root = P_INVALID;
+			mc->mc_db->md_depth = 0;
+			mc->mc_db->md_leaf_pages = 0;
+			rc = mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
+			if (rc)
+				return rc;
+			/* Adjust cursors pointing to mp */
+			mc->mc_snum = 0;
+			mc->mc_top = 0;
+			mc->mc_flags &= ~C_INITIALIZED;
+			{
+				MDB_cursor *m2, *m3;
+				MDB_dbi dbi = mc->mc_dbi;
+
+				for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+					if (mc->mc_flags & C_SUB)
+						m3 = &m2->mc_xcursor->mx_cursor;
+					else
+						m3 = m2;
+					if (!(m3->mc_flags & C_INITIALIZED) || (m3->mc_snum < mc->mc_snum))
+						continue;
+					if (m3->mc_pg[0] == mp) {
+						m3->mc_snum = 0;
+						m3->mc_top = 0;
+						m3->mc_flags &= ~C_INITIALIZED;
+					}
+				}
+			}
+		} else if (IS_BRANCH(mp) && NUMKEYS(mp) == 1) {
+			int i;
+			DPUTS("collapsing root page!");
+			rc = mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
+			if (rc)
+				return rc;
+			mc->mc_db->md_root = NODEPGNO(NODEPTR(mp, 0));
+			rc = mdb_page_get(mc, mc->mc_db->md_root, &mc->mc_pg[0], NULL);
+			if (rc)
+				return rc;
+			mc->mc_db->md_depth--;
+			mc->mc_db->md_branch_pages--;
+			mc->mc_ki[0] = mc->mc_ki[1];
+			for (i = 1; i<mc->mc_db->md_depth; i++) {
+				mc->mc_pg[i] = mc->mc_pg[i+1];
+				mc->mc_ki[i] = mc->mc_ki[i+1];
+			}
+			{
+				/* Adjust other cursors pointing to mp */
+				MDB_cursor *m2, *m3;
+				MDB_dbi dbi = mc->mc_dbi;
+
+				for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+					if (mc->mc_flags & C_SUB)
+						m3 = &m2->mc_xcursor->mx_cursor;
+					else
+						m3 = m2;
+					if (m3 == mc) continue;
+					if (!(m3->mc_flags & C_INITIALIZED))
+						continue;
+					if (m3->mc_pg[0] == mp) {
+						for (i=0; i<mc->mc_db->md_depth; i++) {
+							m3->mc_pg[i] = m3->mc_pg[i+1];
+							m3->mc_ki[i] = m3->mc_ki[i+1];
+						}
+						m3->mc_snum--;
+						m3->mc_top--;
+					}
+				}
+			}
+		} else
+			DPUTS("root page doesn't need rebalancing");
+		return MDB_SUCCESS;
+	}
+
+	/* The parent (branch page) must have at least 2 pointers,
+	 * otherwise the tree is invalid.
+	 */
+	ptop = mc->mc_top-1;
+	mdb_cassert(mc, NUMKEYS(mc->mc_pg[ptop]) > 1);
+
+	/* Leaf page fill factor is below the threshold.
+	 * Try to move keys from left or right neighbor, or
+	 * merge with a neighbor page.
+	 */
+
+	/* Find neighbors.
+	 */
+	mdb_cursor_copy(mc, &mn);
+	mn.mc_xcursor = NULL;
+
+	oldki = mc->mc_ki[mc->mc_top];
+	if (mc->mc_ki[ptop] == 0) {
+		/* We're the leftmost leaf in our parent.
+		 */
+		DPUTS("reading right neighbor");
+		mn.mc_ki[ptop]++;
+		node = NODEPTR(mc->mc_pg[ptop], mn.mc_ki[ptop]);
+		rc = mdb_page_get(mc, NODEPGNO(node), &mn.mc_pg[mn.mc_top], NULL);
+		if (rc)
+			return rc;
+		mn.mc_ki[mn.mc_top] = 0;
+		mc->mc_ki[mc->mc_top] = NUMKEYS(mc->mc_pg[mc->mc_top]);
+		fromleft = 0;
+	} else {
+		/* There is at least one neighbor to the left.
+		 */
+		DPUTS("reading left neighbor");
+		mn.mc_ki[ptop]--;
+		node = NODEPTR(mc->mc_pg[ptop], mn.mc_ki[ptop]);
+		rc = mdb_page_get(mc, NODEPGNO(node), &mn.mc_pg[mn.mc_top], NULL);
+		if (rc)
+			return rc;
+		mn.mc_ki[mn.mc_top] = NUMKEYS(mn.mc_pg[mn.mc_top]) - 1;
+		mc->mc_ki[mc->mc_top] = 0;
+		fromleft = 1;
+	}
+
+	DPRINTF(("found neighbor page %"Z"u (%u keys, %.1f%% full)",
+	    mn.mc_pg[mn.mc_top]->mp_pgno, NUMKEYS(mn.mc_pg[mn.mc_top]),
+		(float)PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) / 10));
+
+	/* If the neighbor page is above threshold and has enough keys,
+	 * move one key from it. Otherwise we should try to merge them.
+	 * (A branch page must never have less than 2 keys.)
+	 */
+	if (PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) >= thresh && NUMKEYS(mn.mc_pg[mn.mc_top]) > minkeys) {
+		rc = mdb_node_move(&mn, mc, fromleft);
+		if (fromleft) {
+			/* if we inserted on left, bump position up */
+			oldki++;
+		}
+	} else {
+		if (!fromleft) {
+			rc = mdb_page_merge(&mn, mc);
+		} else {
+			oldki += NUMKEYS(mn.mc_pg[mn.mc_top]);
+			mn.mc_ki[mn.mc_top] += mc->mc_ki[mn.mc_top] + 1;
+			/* We want mdb_rebalance to find mn when doing fixups */
+			WITH_CURSOR_TRACKING(mn,
+				rc = mdb_page_merge(mc, &mn));
+			mdb_cursor_copy(&mn, mc);
+		}
+		mc->mc_flags &= ~C_EOF;
+	}
+	mc->mc_ki[mc->mc_top] = oldki;
+	return rc;
+}
+
+/** Complete a delete operation started by #mdb_cursor_del(). */
+static int
+mdb_cursor_del0(MDB_cursor *mc)
+{
+	int rc;
+	MDB_page *mp;
+	indx_t ki;
+	unsigned int nkeys;
+	MDB_cursor *m2, *m3;
+	MDB_dbi dbi = mc->mc_dbi;
+
+	ki = mc->mc_ki[mc->mc_top];
+	mp = mc->mc_pg[mc->mc_top];
+	mdb_node_del(mc, mc->mc_db->md_pad);
+	mc->mc_db->md_entries--;
+	{
+		/* Adjust other cursors pointing to mp */
+		for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+			if (! (m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+				continue;
+			if (m3 == mc || m3->mc_snum < mc->mc_snum)
+				continue;
+			if (m3->mc_pg[mc->mc_top] == mp) {
+				if (m3->mc_ki[mc->mc_top] == ki) {
+					m3->mc_flags |= C_DEL;
+					if (mc->mc_db->md_flags & MDB_DUPSORT) {
+						/* Sub-cursor referred into dataset which is gone */
+						m3->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
+					}
+					continue;
+				} else if (m3->mc_ki[mc->mc_top] > ki) {
+					m3->mc_ki[mc->mc_top]--;
+				}
+				XCURSOR_REFRESH(m3, mc->mc_top, mp);
+			}
+		}
+	}
+	rc = mdb_rebalance(mc);
+
+	if (rc == MDB_SUCCESS) {
+		/* DB is totally empty now, just bail out.
+		 * Other cursors adjustments were already done
+		 * by mdb_rebalance and aren't needed here.
+		 */
+		if (!mc->mc_snum)
+			return rc;
+
+		mp = mc->mc_pg[mc->mc_top];
+		nkeys = NUMKEYS(mp);
+
+		/* Adjust other cursors pointing to mp */
+		for (m2 = mc->mc_txn->mt_cursors[dbi]; !rc && m2; m2=m2->mc_next) {
+			m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+			if (! (m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+				continue;
+			if (m3->mc_snum < mc->mc_snum)
+				continue;
+			if (m3->mc_pg[mc->mc_top] == mp) {
+				/* if m3 points past last node in page, find next sibling */
+				if (m3->mc_ki[mc->mc_top] >= mc->mc_ki[mc->mc_top]) {
+					if (m3->mc_ki[mc->mc_top] >= nkeys) {
+						rc = mdb_cursor_sibling(m3, 1);
+						if (rc == MDB_NOTFOUND) {
+							m3->mc_flags |= C_EOF;
+							rc = MDB_SUCCESS;
+							continue;
+						}
+					}
+					if (mc->mc_db->md_flags & MDB_DUPSORT) {
+						MDB_node *node = NODEPTR(m3->mc_pg[m3->mc_top], m3->mc_ki[m3->mc_top]);
+						/* If this node has dupdata, it may need to be reinited
+						 * because its data has moved.
+						 * If the xcursor was not initd it must be reinited.
+						 * Else if node points to a subDB, nothing is needed.
+						 * Else (xcursor was initd, not a subDB) needs mc_pg[0] reset.
+						 */
+						if (node->mn_flags & F_DUPDATA) {
+							if (m3->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
+								if (!(node->mn_flags & F_SUBDATA))
+									m3->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(node);
+							} else {
+								mdb_xcursor_init1(m3, node);
+								m3->mc_xcursor->mx_cursor.mc_flags |= C_DEL;
+							}
+						}
+					}
+				}
+			}
+		}
+		mc->mc_flags |= C_DEL;
+	}
+
+	if (rc)
+		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+	return rc;
+}
+
+int
+mdb_del(MDB_txn *txn, MDB_dbi dbi,
+    MDB_val *key, MDB_val *data)
+{
+	if (!key || !TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+
+	if (txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_BLOCKED))
+		return (txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
+
+	if (!F_ISSET(txn->mt_dbs[dbi].md_flags, MDB_DUPSORT)) {
+		/* must ignore any data */
+		data = NULL;
+	}
+
+	return mdb_del0(txn, dbi, key, data, 0);
+}
+
+static int
+mdb_del0(MDB_txn *txn, MDB_dbi dbi,
+	MDB_val *key, MDB_val *data, unsigned flags)
+{
+	MDB_cursor mc;
+	MDB_xcursor mx;
+	MDB_cursor_op op;
+	MDB_val rdata, *xdata;
+	int		 rc, exact = 0;
+	DKBUF;
+
+	DPRINTF(("====> delete db %u key [%s]", dbi, DKEY(key)));
+
+	mdb_cursor_init(&mc, txn, dbi, &mx);
+
+	if (data) {
+		op = MDB_GET_BOTH;
+		rdata = *data;
+		xdata = &rdata;
+	} else {
+		op = MDB_SET;
+		xdata = NULL;
+		flags |= MDB_NODUPDATA;
+	}
+	rc = mdb_cursor_set(&mc, key, xdata, op, &exact);
+	if (rc == 0) {
+		/* let mdb_page_split know about this cursor if needed:
+		 * delete will trigger a rebalance; if it needs to move
+		 * a node from one page to another, it will have to
+		 * update the parent's separator key(s). If the new sepkey
+		 * is larger than the current one, the parent page may
+		 * run out of space, triggering a split. We need this
+		 * cursor to be consistent until the end of the rebalance.
+		 */
+		mc.mc_flags |= C_UNTRACK;
+		mc.mc_next = txn->mt_cursors[dbi];
+		txn->mt_cursors[dbi] = &mc;
+		rc = mdb_cursor_del(&mc, flags);
+		txn->mt_cursors[dbi] = mc.mc_next;
+	}
+	return rc;
+}
+
+/** Split a page and insert a new node.
+ * Set #MDB_TXN_ERROR on failure.
+ * @param[in,out] mc Cursor pointing to the page and desired insertion index.
+ * The cursor will be updated to point to the actual page and index where
+ * the node got inserted after the split.
+ * @param[in] newkey The key for the newly inserted node.
+ * @param[in] newdata The data for the newly inserted node.
+ * @param[in] newpgno The page number, if the new node is a branch node.
+ * @param[in] nflags The #NODE_ADD_FLAGS for the new node.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno,
+	unsigned int nflags)
+{
+	unsigned int flags;
+	int		 rc = MDB_SUCCESS, new_root = 0, did_split = 0;
+	indx_t		 newindx;
+	pgno_t		 pgno = 0;
+	int	 i, j, split_indx, nkeys, pmax;
+	MDB_env 	*env = mc->mc_txn->mt_env;
+	MDB_node	*node;
+	MDB_val	 sepkey, rkey, xdata, *rdata = &xdata;
+	MDB_page	*copy = NULL;
+	MDB_page	*mp, *rp, *pp;
+	int ptop;
+	MDB_cursor	mn;
+	DKBUF;
+
+	mp = mc->mc_pg[mc->mc_top];
+	newindx = mc->mc_ki[mc->mc_top];
+	nkeys = NUMKEYS(mp);
+
+	DPRINTF(("-----> splitting %s page %"Z"u and adding [%s] at index %i/%i",
+	    IS_LEAF(mp) ? "leaf" : "branch", mp->mp_pgno,
+	    DKEY(newkey), mc->mc_ki[mc->mc_top], nkeys));
+
+	/* Create a right sibling. */
+	if ((rc = mdb_page_new(mc, mp->mp_flags, 1, &rp)))
+		return rc;
+	rp->mp_pad = mp->mp_pad;
+	DPRINTF(("new right sibling: page %"Z"u", rp->mp_pgno));
+
+	/* Usually when splitting the root page, the cursor
+	 * height is 1. But when called from mdb_update_key,
+	 * the cursor height may be greater because it walks
+	 * up the stack while finding the branch slot to update.
+	 */
+	if (mc->mc_top < 1) {
+		if ((rc = mdb_page_new(mc, P_BRANCH, 1, &pp)))
+			goto done;
+		/* shift current top to make room for new parent */
+		for (i=mc->mc_snum; i>0; i--) {
+			mc->mc_pg[i] = mc->mc_pg[i-1];
+			mc->mc_ki[i] = mc->mc_ki[i-1];
+		}
+		mc->mc_pg[0] = pp;
+		mc->mc_ki[0] = 0;
+		mc->mc_db->md_root = pp->mp_pgno;
+		DPRINTF(("root split! new root = %"Z"u", pp->mp_pgno));
+		new_root = mc->mc_db->md_depth++;
+
+		/* Add left (implicit) pointer. */
+		if ((rc = mdb_node_add(mc, 0, NULL, NULL, mp->mp_pgno, 0)) != MDB_SUCCESS) {
+			/* undo the pre-push */
+			mc->mc_pg[0] = mc->mc_pg[1];
+			mc->mc_ki[0] = mc->mc_ki[1];
+			mc->mc_db->md_root = mp->mp_pgno;
+			mc->mc_db->md_depth--;
+			goto done;
+		}
+		mc->mc_snum++;
+		mc->mc_top++;
+		ptop = 0;
+	} else {
+		ptop = mc->mc_top-1;
+		DPRINTF(("parent branch page is %"Z"u", mc->mc_pg[ptop]->mp_pgno));
+	}
+
+	mdb_cursor_copy(mc, &mn);
+	mn.mc_xcursor = NULL;
+	mn.mc_pg[mn.mc_top] = rp;
+	mn.mc_ki[ptop] = mc->mc_ki[ptop]+1;
+
+	if (nflags & MDB_APPEND) {
+		mn.mc_ki[mn.mc_top] = 0;
+		sepkey = *newkey;
+		split_indx = newindx;
+		nkeys = 0;
+	} else {
+
+		split_indx = (nkeys+1) / 2;
+
+		if (IS_LEAF2(rp)) {
+			char *split, *ins;
+			int x;
+			unsigned int lsize, rsize, ksize;
+			/* Move half of the keys to the right sibling */
+			x = mc->mc_ki[mc->mc_top] - split_indx;
+			ksize = mc->mc_db->md_pad;
+			split = LEAF2KEY(mp, split_indx, ksize);
+			rsize = (nkeys - split_indx) * ksize;
+			lsize = (nkeys - split_indx) * sizeof(indx_t);
+			mp->mp_lower -= lsize;
+			rp->mp_lower += lsize;
+			mp->mp_upper += rsize - lsize;
+			rp->mp_upper -= rsize - lsize;
+			sepkey.mv_size = ksize;
+			if (newindx == split_indx) {
+				sepkey.mv_data = newkey->mv_data;
+			} else {
+				sepkey.mv_data = split;
+			}
+			if (x<0) {
+				ins = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], ksize);
+				memcpy(rp->mp_ptrs, split, rsize);
+				sepkey.mv_data = rp->mp_ptrs;
+				memmove(ins+ksize, ins, (split_indx - mc->mc_ki[mc->mc_top]) * ksize);
+				memcpy(ins, newkey->mv_data, ksize);
+				mp->mp_lower += sizeof(indx_t);
+				mp->mp_upper -= ksize - sizeof(indx_t);
+			} else {
+				if (x)
+					memcpy(rp->mp_ptrs, split, x * ksize);
+				ins = LEAF2KEY(rp, x, ksize);
+				memcpy(ins, newkey->mv_data, ksize);
+				memcpy(ins+ksize, split + x * ksize, rsize - x * ksize);
+				rp->mp_lower += sizeof(indx_t);
+				rp->mp_upper -= ksize - sizeof(indx_t);
+				mc->mc_ki[mc->mc_top] = x;
+			}
+		} else {
+			int psize, nsize, k;
+			/* Maximum free space in an empty page */
+			pmax = env->me_psize - PAGEHDRSZ;
+			if (IS_LEAF(mp))
+				nsize = mdb_leaf_size(env, newkey, newdata);
+			else
+				nsize = mdb_branch_size(env, newkey);
+			nsize = EVEN(nsize);
+
+			/* grab a page to hold a temporary copy */
+			copy = mdb_page_malloc(mc->mc_txn, 1);
+			if (copy == NULL) {
+				rc = ENOMEM;
+				goto done;
+			}
+			copy->mp_pgno  = mp->mp_pgno;
+			copy->mp_flags = mp->mp_flags;
+			copy->mp_lower = (PAGEHDRSZ-PAGEBASE);
+			copy->mp_upper = env->me_psize - PAGEBASE;
+
+			/* prepare to insert */
+			for (i=0, j=0; i<nkeys; i++) {
+				if (i == newindx) {
+					copy->mp_ptrs[j++] = 0;
+				}
+				copy->mp_ptrs[j++] = mp->mp_ptrs[i];
+			}
+
+			/* When items are relatively large the split point needs
+			 * to be checked, because being off-by-one will make the
+			 * difference between success or failure in mdb_node_add.
+			 *
+			 * It's also relevant if a page happens to be laid out
+			 * such that one half of its nodes are all "small" and
+			 * the other half of its nodes are "large." If the new
+			 * item is also "large" and falls on the half with
+			 * "large" nodes, it also may not fit.
+			 *
+			 * As a final tweak, if the new item goes on the last
+			 * spot on the page (and thus, onto the new page), bias
+			 * the split so the new page is emptier than the old page.
+			 * This yields better packing during sequential inserts.
+			 */
+			if (nkeys < 20 || nsize > pmax/16 || newindx >= nkeys) {
+				/* Find split point */
+				psize = 0;
+				if (newindx <= split_indx || newindx >= nkeys) {
+					i = 0; j = 1;
+					k = newindx >= nkeys ? nkeys : split_indx+1+IS_LEAF(mp);
+				} else {
+					i = nkeys; j = -1;
+					k = split_indx-1;
+				}
+				for (; i!=k; i+=j) {
+					if (i == newindx) {
+						psize += nsize;
+						node = NULL;
+					} else {
+						node = (MDB_node *)((char *)mp + copy->mp_ptrs[i] + PAGEBASE);
+						psize += NODESIZE + NODEKSZ(node) + sizeof(indx_t);
+						if (IS_LEAF(mp)) {
+							if (F_ISSET(node->mn_flags, F_BIGDATA))
+								psize += sizeof(pgno_t);
+							else
+								psize += NODEDSZ(node);
+						}
+						psize = EVEN(psize);
+					}
+					if (psize > pmax || i == k-j) {
+						split_indx = i + (j<0);
+						break;
+					}
+				}
+			}
+			if (split_indx == newindx) {
+				sepkey.mv_size = newkey->mv_size;
+				sepkey.mv_data = newkey->mv_data;
+			} else {
+				node = (MDB_node *)((char *)mp + copy->mp_ptrs[split_indx] + PAGEBASE);
+				sepkey.mv_size = node->mn_ksize;
+				sepkey.mv_data = NODEKEY(node);
+			}
+		}
+	}
+
+	DPRINTF(("separator is %d [%s]", split_indx, DKEY(&sepkey)));
+
+	/* Copy separator key to the parent.
+	 */
+	if (SIZELEFT(mn.mc_pg[ptop]) < mdb_branch_size(env, &sepkey)) {
+		int snum = mc->mc_snum;
+		mn.mc_snum--;
+		mn.mc_top--;
+		did_split = 1;
+		/* We want other splits to find mn when doing fixups */
+		WITH_CURSOR_TRACKING(mn,
+			rc = mdb_page_split(&mn, &sepkey, NULL, rp->mp_pgno, 0));
+		if (rc)
+			goto done;
+
+		/* root split? */
+		if (mc->mc_snum > snum) {
+			ptop++;
+		}
+		/* Right page might now have changed parent.
+		 * Check if left page also changed parent.
+		 */
+		if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+		    mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
+			for (i=0; i<ptop; i++) {
+				mc->mc_pg[i] = mn.mc_pg[i];
+				mc->mc_ki[i] = mn.mc_ki[i];
+			}
+			mc->mc_pg[ptop] = mn.mc_pg[ptop];
+			if (mn.mc_ki[ptop]) {
+				mc->mc_ki[ptop] = mn.mc_ki[ptop] - 1;
+			} else {
+				/* find right page's left sibling */
+				mc->mc_ki[ptop] = mn.mc_ki[ptop];
+				mdb_cursor_sibling(mc, 0);
+			}
+		}
+	} else {
+		mn.mc_top--;
+		rc = mdb_node_add(&mn, mn.mc_ki[ptop], &sepkey, NULL, rp->mp_pgno, 0);
+		mn.mc_top++;
+	}
+	if (rc != MDB_SUCCESS) {
+		goto done;
+	}
+	if (nflags & MDB_APPEND) {
+		mc->mc_pg[mc->mc_top] = rp;
+		mc->mc_ki[mc->mc_top] = 0;
+		rc = mdb_node_add(mc, 0, newkey, newdata, newpgno, nflags);
+		if (rc)
+			goto done;
+		for (i=0; i<mc->mc_top; i++)
+			mc->mc_ki[i] = mn.mc_ki[i];
+	} else if (!IS_LEAF2(mp)) {
+		/* Move nodes */
+		mc->mc_pg[mc->mc_top] = rp;
+		i = split_indx;
+		j = 0;
+		do {
+			if (i == newindx) {
+				rkey.mv_data = newkey->mv_data;
+				rkey.mv_size = newkey->mv_size;
+				if (IS_LEAF(mp)) {
+					rdata = newdata;
+				} else
+					pgno = newpgno;
+				flags = nflags;
+				/* Update index for the new key. */
+				mc->mc_ki[mc->mc_top] = j;
+			} else {
+				node = (MDB_node *)((char *)mp + copy->mp_ptrs[i] + PAGEBASE);
+				rkey.mv_data = NODEKEY(node);
+				rkey.mv_size = node->mn_ksize;
+				if (IS_LEAF(mp)) {
+					xdata.mv_data = NODEDATA(node);
+					xdata.mv_size = NODEDSZ(node);
+					rdata = &xdata;
+				} else
+					pgno = NODEPGNO(node);
+				flags = node->mn_flags;
+			}
+
+			if (!IS_LEAF(mp) && j == 0) {
+				/* First branch index doesn't need key data. */
+				rkey.mv_size = 0;
+			}
+
+			rc = mdb_node_add(mc, j, &rkey, rdata, pgno, flags);
+			if (rc)
+				goto done;
+			if (i == nkeys) {
+				i = 0;
+				j = 0;
+				mc->mc_pg[mc->mc_top] = copy;
+			} else {
+				i++;
+				j++;
+			}
+		} while (i != split_indx);
+
+		nkeys = NUMKEYS(copy);
+		for (i=0; i<nkeys; i++)
+			mp->mp_ptrs[i] = copy->mp_ptrs[i];
+		mp->mp_lower = copy->mp_lower;
+		mp->mp_upper = copy->mp_upper;
+		memcpy(NODEPTR(mp, nkeys-1), NODEPTR(copy, nkeys-1),
+			env->me_psize - copy->mp_upper - PAGEBASE);
+
+		/* reset back to original page */
+		if (newindx < split_indx) {
+			mc->mc_pg[mc->mc_top] = mp;
+		} else {
+			mc->mc_pg[mc->mc_top] = rp;
+			mc->mc_ki[ptop]++;
+			/* Make sure mc_ki is still valid.
+			 */
+			if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+				mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
+				for (i=0; i<=ptop; i++) {
+					mc->mc_pg[i] = mn.mc_pg[i];
+					mc->mc_ki[i] = mn.mc_ki[i];
+				}
+			}
+		}
+		if (nflags & MDB_RESERVE) {
+			node = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
+			if (!(node->mn_flags & F_BIGDATA))
+				newdata->mv_data = NODEDATA(node);
+		}
+	} else {
+		if (newindx >= split_indx) {
+			mc->mc_pg[mc->mc_top] = rp;
+			mc->mc_ki[ptop]++;
+			/* Make sure mc_ki is still valid.
+			 */
+			if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+				mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
+				for (i=0; i<=ptop; i++) {
+					mc->mc_pg[i] = mn.mc_pg[i];
+					mc->mc_ki[i] = mn.mc_ki[i];
+				}
+			}
+		}
+	}
+
+	{
+		/* Adjust other cursors pointing to mp */
+		MDB_cursor *m2, *m3;
+		MDB_dbi dbi = mc->mc_dbi;
+		nkeys = NUMKEYS(mp);
+
+		for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+			if (mc->mc_flags & C_SUB)
+				m3 = &m2->mc_xcursor->mx_cursor;
+			else
+				m3 = m2;
+			if (m3 == mc)
+				continue;
+			if (!(m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+				continue;
+			if (new_root) {
+				int k;
+				/* sub cursors may be on different DB */
+				if (m3->mc_pg[0] != mp)
+					continue;
+				/* root split */
+				for (k=new_root; k>=0; k--) {
+					m3->mc_ki[k+1] = m3->mc_ki[k];
+					m3->mc_pg[k+1] = m3->mc_pg[k];
+				}
+				if (m3->mc_ki[0] >= nkeys) {
+					m3->mc_ki[0] = 1;
+				} else {
+					m3->mc_ki[0] = 0;
+				}
+				m3->mc_pg[0] = mc->mc_pg[0];
+				m3->mc_snum++;
+				m3->mc_top++;
+			}
+			if (m3->mc_top >= mc->mc_top && m3->mc_pg[mc->mc_top] == mp) {
+				if (m3->mc_ki[mc->mc_top] >= newindx && !(nflags & MDB_SPLIT_REPLACE))
+					m3->mc_ki[mc->mc_top]++;
+				if (m3->mc_ki[mc->mc_top] >= nkeys) {
+					m3->mc_pg[mc->mc_top] = rp;
+					m3->mc_ki[mc->mc_top] -= nkeys;
+					for (i=0; i<mc->mc_top; i++) {
+						m3->mc_ki[i] = mn.mc_ki[i];
+						m3->mc_pg[i] = mn.mc_pg[i];
+					}
+				}
+			} else if (!did_split && m3->mc_top >= ptop && m3->mc_pg[ptop] == mc->mc_pg[ptop] &&
+				m3->mc_ki[ptop] >= mc->mc_ki[ptop]) {
+				m3->mc_ki[ptop]++;
+			}
+			if (IS_LEAF(mp))
+				XCURSOR_REFRESH(m3, mc->mc_top, m3->mc_pg[mc->mc_top]);
+		}
+	}
+	DPRINTF(("mp left: %d, rp left: %d", SIZELEFT(mp), SIZELEFT(rp)));
+
+done:
+	if (copy)					/* tmp page */
+		mdb_page_free(env, copy);
+	if (rc)
+		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
+	return rc;
+}
+
+int
+mdb_put(MDB_txn *txn, MDB_dbi dbi,
+    MDB_val *key, MDB_val *data, unsigned int flags)
+{
+	MDB_cursor mc;
+	MDB_xcursor mx;
+	int rc;
+
+	if (!key || !data || !TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+
+	if (flags & ~(MDB_NOOVERWRITE|MDB_NODUPDATA|MDB_RESERVE|MDB_APPEND|MDB_APPENDDUP))
+		return EINVAL;
+
+	if (txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_BLOCKED))
+		return (txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
+
+	mdb_cursor_init(&mc, txn, dbi, &mx);
+	mc.mc_next = txn->mt_cursors[dbi];
+	txn->mt_cursors[dbi] = &mc;
+	rc = mdb_cursor_put(&mc, key, data, flags);
+	txn->mt_cursors[dbi] = mc.mc_next;
+	return rc;
+}
+
+#ifndef MDB_WBUF
+#define MDB_WBUF	(1024*1024)
+#endif
+#define MDB_EOF		0x10	/**< #mdb_env_copyfd1() is done reading */
+
+	/** State needed for a double-buffering compacting copy. */
+typedef struct mdb_copy {
+	MDB_env *mc_env;
+	MDB_txn *mc_txn;
+	pthread_mutex_t mc_mutex;
+	pthread_cond_t mc_cond;	/**< Condition variable for #mc_new */
+	char *mc_wbuf[2];
+	char *mc_over[2];
+	int mc_wlen[2];
+	int mc_olen[2];
+	pgno_t mc_next_pgno;
+	HANDLE mc_fd;
+	int mc_toggle;			/**< Buffer number in provider */
+	int mc_new;				/**< (0-2 buffers to write) | (#MDB_EOF at end) */
+	/** Error code.  Never cleared if set.  Both threads can set nonzero
+	 *	to fail the copy.  Not mutex-protected, LMDB expects atomic int.
+	 */
+	volatile int mc_error;
+} mdb_copy;
+
+	/** Dedicated writer thread for compacting copy. */
+static THREAD_RET ESECT CALL_CONV
+mdb_env_copythr(void *arg)
+{
+	mdb_copy *my = arg;
+	char *ptr;
+	int toggle = 0, wsize, rc;
+#ifdef _WIN32
+	DWORD len;
+#define DO_WRITE(rc, fd, ptr, w2, len)	rc = WriteFile(fd, ptr, w2, &len, NULL)
+#else
+	int len;
+#define DO_WRITE(rc, fd, ptr, w2, len)	len = write(fd, ptr, w2); rc = (len >= 0)
+#ifdef SIGPIPE
+	sigset_t set;
+	sigemptyset(&set);
+	sigaddset(&set, SIGPIPE);
+	if ((rc = pthread_sigmask(SIG_BLOCK, &set, NULL)) != 0)
+		my->mc_error = rc;
+#endif
+#endif
+
+	pthread_mutex_lock(&my->mc_mutex);
+	for(;;) {
+		while (!my->mc_new)
+			pthread_cond_wait(&my->mc_cond, &my->mc_mutex);
+		if (my->mc_new == 0 + MDB_EOF) /* 0 buffers, just EOF */
+			break;
+		wsize = my->mc_wlen[toggle];
+		ptr = my->mc_wbuf[toggle];
+again:
+		rc = MDB_SUCCESS;
+		while (wsize > 0 && !my->mc_error) {
+			DO_WRITE(rc, my->mc_fd, ptr, wsize, len);
+			if (!rc) {
+				rc = ErrCode();
+#if defined(SIGPIPE) && !defined(_WIN32)
+				if (rc == EPIPE) {
+					/* Collect the pending SIGPIPE, otherwise at least OS X
+					 * gives it to the process on thread-exit (ITS#8504).
+					 */
+					int tmp;
+					sigwait(&set, &tmp);
+				}
+#endif
+				break;
+			} else if (len > 0) {
+				rc = MDB_SUCCESS;
+				ptr += len;
+				wsize -= len;
+				continue;
+			} else {
+				rc = EIO;
+				break;
+			}
+		}
+		if (rc) {
+			my->mc_error = rc;
+		}
+		/* If there's an overflow page tail, write it too */
+		if (my->mc_olen[toggle]) {
+			wsize = my->mc_olen[toggle];
+			ptr = my->mc_over[toggle];
+			my->mc_olen[toggle] = 0;
+			goto again;
+		}
+		my->mc_wlen[toggle] = 0;
+		toggle ^= 1;
+		/* Return the empty buffer to provider */
+		my->mc_new--;
+		pthread_cond_signal(&my->mc_cond);
+	}
+	pthread_mutex_unlock(&my->mc_mutex);
+	return (THREAD_RET)0;
+#undef DO_WRITE
+}
+
+	/** Give buffer and/or #MDB_EOF to writer thread, await unused buffer.
+	 *
+	 * @param[in] my control structure.
+	 * @param[in] adjust (1 to hand off 1 buffer) | (MDB_EOF when ending).
+	 */
+static int ESECT
+mdb_env_cthr_toggle(mdb_copy *my, int adjust)
+{
+	pthread_mutex_lock(&my->mc_mutex);
+	my->mc_new += adjust;
+	pthread_cond_signal(&my->mc_cond);
+	while (my->mc_new & 2)		/* both buffers in use */
+		pthread_cond_wait(&my->mc_cond, &my->mc_mutex);
+	pthread_mutex_unlock(&my->mc_mutex);
+
+	my->mc_toggle ^= (adjust & 1);
+	/* Both threads reset mc_wlen, to be safe from threading errors */
+	my->mc_wlen[my->mc_toggle] = 0;
+	return my->mc_error;
+}
+
+	/** Depth-first tree traversal for compacting copy.
+	 * @param[in] my control structure.
+	 * @param[in,out] pg database root.
+	 * @param[in] flags includes #F_DUPDATA if it is a sorted-duplicate sub-DB.
+	 */
+static int ESECT
+mdb_env_cwalk(mdb_copy *my, pgno_t *pg, int flags)
+{
+	MDB_cursor mc = {0};
+	MDB_node *ni;
+	MDB_page *mo, *mp, *leaf;
+	char *buf, *ptr;
+	int rc, toggle;
+	unsigned int i;
+
+	/* Empty DB, nothing to do */
+	if (*pg == P_INVALID)
+		return MDB_SUCCESS;
+
+	mc.mc_snum = 1;
+	mc.mc_txn = my->mc_txn;
+
+	rc = mdb_page_get(&mc, *pg, &mc.mc_pg[0], NULL);
+	if (rc)
+		return rc;
+	rc = mdb_page_search_root(&mc, NULL, MDB_PS_FIRST);
+	if (rc)
+		return rc;
+
+	/* Make cursor pages writable */
+	buf = ptr = malloc(my->mc_env->me_psize * mc.mc_snum);
+	if (buf == NULL)
+		return ENOMEM;
+
+	for (i=0; i<mc.mc_top; i++) {
+		mdb_page_copy((MDB_page *)ptr, mc.mc_pg[i], my->mc_env->me_psize);
+		mc.mc_pg[i] = (MDB_page *)ptr;
+		ptr += my->mc_env->me_psize;
+	}
+
+	/* This is writable space for a leaf page. Usually not needed. */
+	leaf = (MDB_page *)ptr;
+
+	toggle = my->mc_toggle;
+	while (mc.mc_snum > 0) {
+		unsigned n;
+		mp = mc.mc_pg[mc.mc_top];
+		n = NUMKEYS(mp);
+
+		if (IS_LEAF(mp)) {
+			if (!IS_LEAF2(mp) && !(flags & F_DUPDATA)) {
+				for (i=0; i<n; i++) {
+					ni = NODEPTR(mp, i);
+					if (ni->mn_flags & F_BIGDATA) {
+						MDB_page *omp;
+						pgno_t pg;
+
+						/* Need writable leaf */
+						if (mp != leaf) {
+							mc.mc_pg[mc.mc_top] = leaf;
+							mdb_page_copy(leaf, mp, my->mc_env->me_psize);
+							mp = leaf;
+							ni = NODEPTR(mp, i);
+						}
+
+						memcpy(&pg, NODEDATA(ni), sizeof(pg));
+						memcpy(NODEDATA(ni), &my->mc_next_pgno, sizeof(pgno_t));
+						rc = mdb_page_get(&mc, pg, &omp, NULL);
+						if (rc)
+							goto done;
+						if (my->mc_wlen[toggle] >= MDB_WBUF) {
+							rc = mdb_env_cthr_toggle(my, 1);
+							if (rc)
+								goto done;
+							toggle = my->mc_toggle;
+						}
+						mo = (MDB_page *)(my->mc_wbuf[toggle] + my->mc_wlen[toggle]);
+						memcpy(mo, omp, my->mc_env->me_psize);
+						mo->mp_pgno = my->mc_next_pgno;
+						my->mc_next_pgno += omp->mp_pages;
+						my->mc_wlen[toggle] += my->mc_env->me_psize;
+						if (omp->mp_pages > 1) {
+							my->mc_olen[toggle] = my->mc_env->me_psize * (omp->mp_pages - 1);
+							my->mc_over[toggle] = (char *)omp + my->mc_env->me_psize;
+							rc = mdb_env_cthr_toggle(my, 1);
+							if (rc)
+								goto done;
+							toggle = my->mc_toggle;
+						}
+					} else if (ni->mn_flags & F_SUBDATA) {
+						MDB_db db;
+
+						/* Need writable leaf */
+						if (mp != leaf) {
+							mc.mc_pg[mc.mc_top] = leaf;
+							mdb_page_copy(leaf, mp, my->mc_env->me_psize);
+							mp = leaf;
+							ni = NODEPTR(mp, i);
+						}
+
+						memcpy(&db, NODEDATA(ni), sizeof(db));
+						my->mc_toggle = toggle;
+						rc = mdb_env_cwalk(my, &db.md_root, ni->mn_flags & F_DUPDATA);
+						if (rc)
+							goto done;
+						toggle = my->mc_toggle;
+						memcpy(NODEDATA(ni), &db, sizeof(db));
+					}
+				}
+			}
+		} else {
+			mc.mc_ki[mc.mc_top]++;
+			if (mc.mc_ki[mc.mc_top] < n) {
+				pgno_t pg;
+again:
+				ni = NODEPTR(mp, mc.mc_ki[mc.mc_top]);
+				pg = NODEPGNO(ni);
+				rc = mdb_page_get(&mc, pg, &mp, NULL);
+				if (rc)
+					goto done;
+				mc.mc_top++;
+				mc.mc_snum++;
+				mc.mc_ki[mc.mc_top] = 0;
+				if (IS_BRANCH(mp)) {
+					/* Whenever we advance to a sibling branch page,
+					 * we must proceed all the way down to its first leaf.
+					 */
+					mdb_page_copy(mc.mc_pg[mc.mc_top], mp, my->mc_env->me_psize);
+					goto again;
+				} else
+					mc.mc_pg[mc.mc_top] = mp;
+				continue;
+			}
+		}
+		if (my->mc_wlen[toggle] >= MDB_WBUF) {
+			rc = mdb_env_cthr_toggle(my, 1);
+			if (rc)
+				goto done;
+			toggle = my->mc_toggle;
+		}
+		mo = (MDB_page *)(my->mc_wbuf[toggle] + my->mc_wlen[toggle]);
+		mdb_page_copy(mo, mp, my->mc_env->me_psize);
+		mo->mp_pgno = my->mc_next_pgno++;
+		my->mc_wlen[toggle] += my->mc_env->me_psize;
+		if (mc.mc_top) {
+			/* Update parent if there is one */
+			ni = NODEPTR(mc.mc_pg[mc.mc_top-1], mc.mc_ki[mc.mc_top-1]);
+			SETPGNO(ni, mo->mp_pgno);
+			mdb_cursor_pop(&mc);
+		} else {
+			/* Otherwise we're done */
+			*pg = mo->mp_pgno;
+			break;
+		}
+	}
+done:
+	free(buf);
+	return rc;
+}
+
+	/** Copy environment with compaction. */
+static int ESECT
+mdb_env_copyfd1(MDB_env *env, HANDLE fd)
+{
+	MDB_meta *mm;
+	MDB_page *mp;
+	mdb_copy my = {0};
+	MDB_txn *txn = NULL;
+	pthread_t thr;
+	pgno_t root, new_root;
+	int rc = MDB_SUCCESS;
+
+#ifdef _WIN32
+	if (!(my.mc_mutex = CreateMutex(NULL, FALSE, NULL)) ||
+		!(my.mc_cond = CreateEvent(NULL, FALSE, FALSE, NULL))) {
+		rc = ErrCode();
+		goto done;
+	}
+	my.mc_wbuf[0] = _aligned_malloc(MDB_WBUF*2, env->me_os_psize);
+	if (my.mc_wbuf[0] == NULL) {
+		/* _aligned_malloc() sets errno, but we use Windows error codes */
+		rc = ERROR_NOT_ENOUGH_MEMORY;
+		goto done;
+	}
+#else
+	if ((rc = pthread_mutex_init(&my.mc_mutex, NULL)) != 0)
+		return rc;
+	if ((rc = pthread_cond_init(&my.mc_cond, NULL)) != 0)
+		goto done2;
+#ifdef HAVE_MEMALIGN
+	my.mc_wbuf[0] = memalign(env->me_os_psize, MDB_WBUF*2);
+	if (my.mc_wbuf[0] == NULL) {
+		rc = errno;
+		goto done;
+	}
+#else
+	{
+		void *p;
+		if ((rc = posix_memalign(&p, env->me_os_psize, MDB_WBUF*2)) != 0)
+			goto done;
+		my.mc_wbuf[0] = p;
+	}
+#endif
+#endif
+	memset(my.mc_wbuf[0], 0, MDB_WBUF*2);
+	my.mc_wbuf[1] = my.mc_wbuf[0] + MDB_WBUF;
+	my.mc_next_pgno = NUM_METAS;
+	my.mc_env = env;
+	my.mc_fd = fd;
+	rc = THREAD_CREATE(thr, mdb_env_copythr, &my);
+	if (rc)
+		goto done;
+
+	rc = mdb_txn_begin(env, NULL, MDB_RDONLY, &txn);
+	if (rc)
+		goto finish;
+
+	mp = (MDB_page *)my.mc_wbuf[0];
+	memset(mp, 0, NUM_METAS * env->me_psize);
+	mp->mp_pgno = 0;
+	mp->mp_flags = P_META;
+	mm = (MDB_meta *)METADATA(mp);
+	mdb_env_init_meta0(env, mm);
+	mm->mm_address = env->me_metas[0]->mm_address;
+
+	mp = (MDB_page *)(my.mc_wbuf[0] + env->me_psize);
+	mp->mp_pgno = 1;
+	mp->mp_flags = P_META;
+	*(MDB_meta *)METADATA(mp) = *mm;
+	mm = (MDB_meta *)METADATA(mp);
+
+	/* Set metapage 1 with current main DB */
+	root = new_root = txn->mt_dbs[MAIN_DBI].md_root;
+	if (root != P_INVALID) {
+		/* Count free pages + freeDB pages.  Subtract from last_pg
+		 * to find the new last_pg, which also becomes the new root.
+		 */
+		MDB_ID freecount = 0;
+		MDB_cursor mc;
+		MDB_val key, data;
+		mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
+		while ((rc = mdb_cursor_get(&mc, &key, &data, MDB_NEXT)) == 0)
+			freecount += *(MDB_ID *)data.mv_data;
+		if (rc != MDB_NOTFOUND)
+			goto finish;
+		freecount += txn->mt_dbs[FREE_DBI].md_branch_pages +
+			txn->mt_dbs[FREE_DBI].md_leaf_pages +
+			txn->mt_dbs[FREE_DBI].md_overflow_pages;
+
+		new_root = txn->mt_next_pgno - 1 - freecount;
+		mm->mm_last_pg = new_root;
+		mm->mm_dbs[MAIN_DBI] = txn->mt_dbs[MAIN_DBI];
+		mm->mm_dbs[MAIN_DBI].md_root = new_root;
+	} else {
+		/* When the DB is empty, handle it specially to
+		 * fix any breakage like page leaks from ITS#8174.
+		 */
+		mm->mm_dbs[MAIN_DBI].md_flags = txn->mt_dbs[MAIN_DBI].md_flags;
+	}
+	if (root != P_INVALID || mm->mm_dbs[MAIN_DBI].md_flags) {
+		mm->mm_txnid = 1;		/* use metapage 1 */
+	}
+
+	my.mc_wlen[0] = env->me_psize * NUM_METAS;
+	my.mc_txn = txn;
+	rc = mdb_env_cwalk(&my, &root, 0);
+	if (rc == MDB_SUCCESS && root != new_root) {
+		rc = MDB_INCOMPATIBLE;	/* page leak or corrupt DB */
+	}
+
+finish:
+	if (rc)
+		my.mc_error = rc;
+	mdb_env_cthr_toggle(&my, 1 | MDB_EOF);
+	rc = THREAD_FINISH(thr);
+	mdb_txn_abort(txn);
+
+done:
+#ifdef _WIN32
+	if (my.mc_wbuf[0]) _aligned_free(my.mc_wbuf[0]);
+	if (my.mc_cond)  CloseHandle(my.mc_cond);
+	if (my.mc_mutex) CloseHandle(my.mc_mutex);
+#else
+	free(my.mc_wbuf[0]);
+	pthread_cond_destroy(&my.mc_cond);
+done2:
+	pthread_mutex_destroy(&my.mc_mutex);
+#endif
+	return rc ? rc : my.mc_error;
+}
+
+	/** Copy environment as-is. */
+static int ESECT
+mdb_env_copyfd0(MDB_env *env, HANDLE fd)
+{
+	MDB_txn *txn = NULL;
+	mdb_mutexref_t wmutex = NULL;
+	int rc;
+	size_t wsize, w3;
+	char *ptr;
+#ifdef _WIN32
+	DWORD len, w2;
+#define DO_WRITE(rc, fd, ptr, w2, len)	rc = WriteFile(fd, ptr, w2, &len, NULL)
+#else
+	ssize_t len;
+	size_t w2;
+#define DO_WRITE(rc, fd, ptr, w2, len)	len = write(fd, ptr, w2); rc = (len >= 0)
+#endif
+
+	/* Do the lock/unlock of the reader mutex before starting the
+	 * write txn.  Otherwise other read txns could block writers.
+	 */
+	rc = mdb_txn_begin(env, NULL, MDB_RDONLY, &txn);
+	if (rc)
+		return rc;
+
+	if (env->me_txns) {
+		/* We must start the actual read txn after blocking writers */
+		mdb_txn_end(txn, MDB_END_RESET_TMP);
+
+		/* Temporarily block writers until we snapshot the meta pages */
+		wmutex = env->me_wmutex;
+		if (LOCK_MUTEX(rc, env, wmutex))
+			goto leave;
+
+		rc = mdb_txn_renew0(txn);
+		if (rc) {
+			UNLOCK_MUTEX(wmutex);
+			goto leave;
+		}
+	}
+
+	wsize = env->me_psize * NUM_METAS;
+	ptr = env->me_map;
+	w2 = wsize;
+	while (w2 > 0) {
+		DO_WRITE(rc, fd, ptr, w2, len);
+		if (!rc) {
+			rc = ErrCode();
+			break;
+		} else if (len > 0) {
+			rc = MDB_SUCCESS;
+			ptr += len;
+			w2 -= len;
+			continue;
+		} else {
+			/* Non-blocking or async handles are not supported */
+			rc = EIO;
+			break;
+		}
+	}
+	if (wmutex)
+		UNLOCK_MUTEX(wmutex);
+
+	if (rc)
+		goto leave;
+
+	w3 = txn->mt_next_pgno * env->me_psize;
+	{
+		size_t fsize = 0;
+		if ((rc = mdb_fsize(env->me_fd, &fsize)))
+			goto leave;
+		if (w3 > fsize)
+			w3 = fsize;
+	}
+	wsize = w3 - wsize;
+	while (wsize > 0) {
+		if (wsize > MAX_WRITE)
+			w2 = MAX_WRITE;
+		else
+			w2 = wsize;
+		DO_WRITE(rc, fd, ptr, w2, len);
+		if (!rc) {
+			rc = ErrCode();
+			break;
+		} else if (len > 0) {
+			rc = MDB_SUCCESS;
+			ptr += len;
+			wsize -= len;
+			continue;
+		} else {
+			rc = EIO;
+			break;
+		}
+	}
+
+leave:
+	mdb_txn_abort(txn);
+	return rc;
+}
+
+int ESECT
+mdb_env_copyfd2(MDB_env *env, HANDLE fd, unsigned int flags)
+{
+	if (flags & MDB_CP_COMPACT)
+		return mdb_env_copyfd1(env, fd);
+	else
+		return mdb_env_copyfd0(env, fd);
+}
+
+int ESECT
+mdb_env_copyfd(MDB_env *env, HANDLE fd)
+{
+	return mdb_env_copyfd2(env, fd, 0);
+}
+
+int ESECT
+mdb_env_copy2(MDB_env *env, const char *path, unsigned int flags)
+{
+	int rc;
+	MDB_name fname;
+	HANDLE newfd = INVALID_HANDLE_VALUE;
+
+	rc = mdb_fname_init(path, env->me_flags | MDB_NOLOCK, &fname);
+	if (rc == MDB_SUCCESS) {
+		rc = mdb_fopen(env, &fname, MDB_O_COPY, 0666, &newfd);
+		mdb_fname_destroy(fname);
+	}
+	if (rc == MDB_SUCCESS) {
+		rc = mdb_env_copyfd2(env, newfd, flags);
+		if (close(newfd) < 0 && rc == MDB_SUCCESS)
+			rc = ErrCode();
+	}
+	return rc;
+}
+
+int ESECT
+mdb_env_copy(MDB_env *env, const char *path)
+{
+	return mdb_env_copy2(env, path, 0);
+}
+
+int ESECT
+mdb_env_set_flags(MDB_env *env, unsigned int flag, int onoff)
+{
+	if (flag & ~CHANGEABLE)
+		return EINVAL;
+	if (onoff)
+		env->me_flags |= flag;
+	else
+		env->me_flags &= ~flag;
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_get_flags(MDB_env *env, unsigned int *arg)
+{
+	if (!env || !arg)
+		return EINVAL;
+
+	*arg = env->me_flags & (CHANGEABLE|CHANGELESS);
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_set_userctx(MDB_env *env, void *ctx)
+{
+	if (!env)
+		return EINVAL;
+	env->me_userctx = ctx;
+	return MDB_SUCCESS;
+}
+
+void * ESECT
+mdb_env_get_userctx(MDB_env *env)
+{
+	return env ? env->me_userctx : NULL;
+}
+
+int ESECT
+mdb_env_set_assert(MDB_env *env, MDB_assert_func *func)
+{
+	if (!env)
+		return EINVAL;
+#ifndef NDEBUG
+	env->me_assert_func = func;
+#endif
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_get_path(MDB_env *env, const char **arg)
+{
+	if (!env || !arg)
+		return EINVAL;
+
+	*arg = env->me_path;
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_get_fd(MDB_env *env, mdb_filehandle_t *arg)
+{
+	if (!env || !arg)
+		return EINVAL;
+
+	*arg = env->me_fd;
+	return MDB_SUCCESS;
+}
+
+/** Common code for #mdb_stat() and #mdb_env_stat().
+ * @param[in] env the environment to operate in.
+ * @param[in] db the #MDB_db record containing the stats to return.
+ * @param[out] arg the address of an #MDB_stat structure to receive the stats.
+ * @return 0, this function always succeeds.
+ */
+static int ESECT
+mdb_stat0(MDB_env *env, MDB_db *db, MDB_stat *arg)
+{
+	arg->ms_psize = env->me_psize;
+	arg->ms_depth = db->md_depth;
+	arg->ms_branch_pages = db->md_branch_pages;
+	arg->ms_leaf_pages = db->md_leaf_pages;
+	arg->ms_overflow_pages = db->md_overflow_pages;
+	arg->ms_entries = db->md_entries;
+
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_stat(MDB_env *env, MDB_stat *arg)
+{
+	MDB_meta *meta;
+
+	if (env == NULL || arg == NULL)
+		return EINVAL;
+
+	meta = mdb_env_pick_meta(env);
+
+	return mdb_stat0(env, &meta->mm_dbs[MAIN_DBI], arg);
+}
+
+int ESECT
+mdb_env_info(MDB_env *env, MDB_envinfo *arg)
+{
+	MDB_meta *meta;
+
+	if (env == NULL || arg == NULL)
+		return EINVAL;
+
+	meta = mdb_env_pick_meta(env);
+	arg->me_mapaddr = meta->mm_address;
+	arg->me_last_pgno = meta->mm_last_pg;
+	arg->me_last_txnid = meta->mm_txnid;
+
+	arg->me_mapsize = env->me_mapsize;
+	arg->me_maxreaders = env->me_maxreaders;
+	arg->me_numreaders = env->me_txns ? env->me_txns->mti_numreaders : 0;
+	return MDB_SUCCESS;
+}
+
+/** Set the default comparison functions for a database.
+ * Called immediately after a database is opened to set the defaults.
+ * The user can then override them with #mdb_set_compare() or
+ * #mdb_set_dupsort().
+ * @param[in] txn A transaction handle returned by #mdb_txn_begin()
+ * @param[in] dbi A database handle returned by #mdb_dbi_open()
+ */
+static void
+mdb_default_cmp(MDB_txn *txn, MDB_dbi dbi)
+{
+	uint16_t f = txn->mt_dbs[dbi].md_flags;
+
+	txn->mt_dbxs[dbi].md_cmp =
+		(f & MDB_REVERSEKEY) ? mdb_cmp_memnr :
+		(f & MDB_INTEGERKEY) ? mdb_cmp_cint  : mdb_cmp_memn;
+
+	txn->mt_dbxs[dbi].md_dcmp =
+		!(f & MDB_DUPSORT) ? 0 :
+		((f & MDB_INTEGERDUP)
+		 ? ((f & MDB_DUPFIXED)   ? mdb_cmp_int   : mdb_cmp_cint)
+		 : ((f & MDB_REVERSEDUP) ? mdb_cmp_memnr : mdb_cmp_memn));
+}
+
+int mdb_dbi_open(MDB_txn *txn, const char *name, unsigned int flags, MDB_dbi *dbi)
+{
+	MDB_val key, data;
+	MDB_dbi i;
+	MDB_cursor mc;
+	MDB_db dummy;
+	int rc, dbflag, exact;
+	unsigned int unused = 0, seq;
+	char *namedup;
+	size_t len;
+
+	if (flags & ~VALID_FLAGS)
+		return EINVAL;
+	if (txn->mt_flags & MDB_TXN_BLOCKED)
+		return MDB_BAD_TXN;
+
+	/* main DB? */
+	if (!name) {
+		*dbi = MAIN_DBI;
+		if (flags & PERSISTENT_FLAGS) {
+			uint16_t f2 = flags & PERSISTENT_FLAGS;
+			/* make sure flag changes get committed */
+			if ((txn->mt_dbs[MAIN_DBI].md_flags | f2) != txn->mt_dbs[MAIN_DBI].md_flags) {
+				txn->mt_dbs[MAIN_DBI].md_flags |= f2;
+				txn->mt_flags |= MDB_TXN_DIRTY;
+			}
+		}
+		mdb_default_cmp(txn, MAIN_DBI);
+		return MDB_SUCCESS;
+	}
+
+	if (txn->mt_dbxs[MAIN_DBI].md_cmp == NULL) {
+		mdb_default_cmp(txn, MAIN_DBI);
+	}
+
+	/* Is the DB already open? */
+	len = strlen(name);
+	for (i=CORE_DBS; i<txn->mt_numdbs; i++) {
+		if (!txn->mt_dbxs[i].md_name.mv_size) {
+			/* Remember this free slot */
+			if (!unused) unused = i;
+			continue;
+		}
+		if (len == txn->mt_dbxs[i].md_name.mv_size &&
+			!strncmp(name, txn->mt_dbxs[i].md_name.mv_data, len)) {
+			*dbi = i;
+			return MDB_SUCCESS;
+		}
+	}
+
+	/* If no free slot and max hit, fail */
+	if (!unused && txn->mt_numdbs >= txn->mt_env->me_maxdbs)
+		return MDB_DBS_FULL;
+
+	/* Cannot mix named databases with some mainDB flags */
+	if (txn->mt_dbs[MAIN_DBI].md_flags & (MDB_DUPSORT|MDB_INTEGERKEY))
+		return (flags & MDB_CREATE) ? MDB_INCOMPATIBLE : MDB_NOTFOUND;
+
+	/* Find the DB info */
+	dbflag = DB_NEW|DB_VALID|DB_USRVALID;
+	exact = 0;
+	key.mv_size = len;
+	key.mv_data = (void *)name;
+	mdb_cursor_init(&mc, txn, MAIN_DBI, NULL);
+	rc = mdb_cursor_set(&mc, &key, &data, MDB_SET, &exact);
+	if (rc == MDB_SUCCESS) {
+		/* make sure this is actually a DB */
+		MDB_node *node = NODEPTR(mc.mc_pg[mc.mc_top], mc.mc_ki[mc.mc_top]);
+		if ((node->mn_flags & (F_DUPDATA|F_SUBDATA)) != F_SUBDATA)
+			return MDB_INCOMPATIBLE;
+	} else {
+		if (rc != MDB_NOTFOUND || !(flags & MDB_CREATE))
+			return rc;
+		if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY))
+			return EACCES;
+	}
+
+	/* Done here so we cannot fail after creating a new DB */
+	if ((namedup = strdup(name)) == NULL)
+		return ENOMEM;
+
+	if (rc) {
+		/* MDB_NOTFOUND and MDB_CREATE: Create new DB */
+		data.mv_size = sizeof(MDB_db);
+		data.mv_data = &dummy;
+		memset(&dummy, 0, sizeof(dummy));
+		dummy.md_root = P_INVALID;
+		dummy.md_flags = flags & PERSISTENT_FLAGS;
+		WITH_CURSOR_TRACKING(mc,
+			rc = mdb_cursor_put(&mc, &key, &data, F_SUBDATA));
+		dbflag |= DB_DIRTY;
+	}
+
+	if (rc) {
+		free(namedup);
+	} else {
+		/* Got info, register DBI in this txn */
+		unsigned int slot = unused ? unused : txn->mt_numdbs;
+		txn->mt_dbxs[slot].md_name.mv_data = namedup;
+		txn->mt_dbxs[slot].md_name.mv_size = len;
+		txn->mt_dbxs[slot].md_rel = NULL;
+		txn->mt_dbflags[slot] = dbflag;
+		/* txn-> and env-> are the same in read txns, use
+		 * tmp variable to avoid undefined assignment
+		 */
+		seq = ++txn->mt_env->me_dbiseqs[slot];
+		txn->mt_dbiseqs[slot] = seq;
+
+		memcpy(&txn->mt_dbs[slot], data.mv_data, sizeof(MDB_db));
+		*dbi = slot;
+		mdb_default_cmp(txn, slot);
+		if (!unused) {
+			txn->mt_numdbs++;
+		}
+	}
+
+	return rc;
+}
+
+int ESECT
+mdb_stat(MDB_txn *txn, MDB_dbi dbi, MDB_stat *arg)
+{
+	if (!arg || !TXN_DBI_EXIST(txn, dbi, DB_VALID))
+		return EINVAL;
+
+	if (txn->mt_flags & MDB_TXN_BLOCKED)
+		return MDB_BAD_TXN;
+
+	if (txn->mt_dbflags[dbi] & DB_STALE) {
+		MDB_cursor mc;
+		MDB_xcursor mx;
+		/* Stale, must read the DB's root. cursor_init does it for us. */
+		mdb_cursor_init(&mc, txn, dbi, &mx);
+	}
+	return mdb_stat0(txn->mt_env, &txn->mt_dbs[dbi], arg);
+}
+
+void mdb_dbi_close(MDB_env *env, MDB_dbi dbi)
+{
+	char *ptr;
+	if (dbi < CORE_DBS || dbi >= env->me_maxdbs)
+		return;
+	ptr = env->me_dbxs[dbi].md_name.mv_data;
+	/* If there was no name, this was already closed */
+	if (ptr) {
+		env->me_dbxs[dbi].md_name.mv_data = NULL;
+		env->me_dbxs[dbi].md_name.mv_size = 0;
+		env->me_dbflags[dbi] = 0;
+		env->me_dbiseqs[dbi]++;
+		free(ptr);
+	}
+}
+
+int mdb_dbi_flags(MDB_txn *txn, MDB_dbi dbi, unsigned int *flags)
+{
+	/* We could return the flags for the FREE_DBI too but what's the point? */
+	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+	*flags = txn->mt_dbs[dbi].md_flags & PERSISTENT_FLAGS;
+	return MDB_SUCCESS;
+}
+
+/** Add all the DB's pages to the free list.
+ * @param[in] mc Cursor on the DB to free.
+ * @param[in] subs non-Zero to check for sub-DBs in this DB.
+ * @return 0 on success, non-zero on failure.
+ */
+static int
+mdb_drop0(MDB_cursor *mc, int subs)
+{
+	int rc;
+
+	rc = mdb_page_search(mc, NULL, MDB_PS_FIRST);
+	if (rc == MDB_SUCCESS) {
+		MDB_txn *txn = mc->mc_txn;
+		MDB_node *ni;
+		MDB_cursor mx;
+		unsigned int i;
+
+		/* DUPSORT sub-DBs have no ovpages/DBs. Omit scanning leaves.
+		 * This also avoids any P_LEAF2 pages, which have no nodes.
+		 * Also if the DB doesn't have sub-DBs and has no overflow
+		 * pages, omit scanning leaves.
+		 */
+		if ((mc->mc_flags & C_SUB) ||
+			(!subs && !mc->mc_db->md_overflow_pages))
+			mdb_cursor_pop(mc);
+
+		mdb_cursor_copy(mc, &mx);
+		while (mc->mc_snum > 0) {
+			MDB_page *mp = mc->mc_pg[mc->mc_top];
+			unsigned n = NUMKEYS(mp);
+			if (IS_LEAF(mp)) {
+				for (i=0; i<n; i++) {
+					ni = NODEPTR(mp, i);
+					if (ni->mn_flags & F_BIGDATA) {
+						MDB_page *omp;
+						pgno_t pg;
+						memcpy(&pg, NODEDATA(ni), sizeof(pg));
+						rc = mdb_page_get(mc, pg, &omp, NULL);
+						if (rc != 0)
+							goto done;
+						mdb_cassert(mc, IS_OVERFLOW(omp));
+						rc = mdb_midl_append_range(&txn->mt_free_pgs,
+							pg, omp->mp_pages);
+						if (rc)
+							goto done;
+						mc->mc_db->md_overflow_pages -= omp->mp_pages;
+						if (!mc->mc_db->md_overflow_pages && !subs)
+							break;
+					} else if (subs && (ni->mn_flags & F_SUBDATA)) {
+						mdb_xcursor_init1(mc, ni);
+						rc = mdb_drop0(&mc->mc_xcursor->mx_cursor, 0);
+						if (rc)
+							goto done;
+					}
+				}
+				if (!subs && !mc->mc_db->md_overflow_pages)
+					goto pop;
+			} else {
+				if ((rc = mdb_midl_need(&txn->mt_free_pgs, n)) != 0)
+					goto done;
+				for (i=0; i<n; i++) {
+					pgno_t pg;
+					ni = NODEPTR(mp, i);
+					pg = NODEPGNO(ni);
+					/* free it */
+					mdb_midl_xappend(txn->mt_free_pgs, pg);
+				}
+			}
+			if (!mc->mc_top)
+				break;
+			mc->mc_ki[mc->mc_top] = i;
+			rc = mdb_cursor_sibling(mc, 1);
+			if (rc) {
+				if (rc != MDB_NOTFOUND)
+					goto done;
+				/* no more siblings, go back to beginning
+				 * of previous level.
+				 */
+pop:
+				mdb_cursor_pop(mc);
+				mc->mc_ki[0] = 0;
+				for (i=1; i<mc->mc_snum; i++) {
+					mc->mc_ki[i] = 0;
+					mc->mc_pg[i] = mx.mc_pg[i];
+				}
+			}
+		}
+		/* free it */
+		rc = mdb_midl_append(&txn->mt_free_pgs, mc->mc_db->md_root);
+done:
+		if (rc)
+			txn->mt_flags |= MDB_TXN_ERROR;
+	} else if (rc == MDB_NOTFOUND) {
+		rc = MDB_SUCCESS;
+	}
+	mc->mc_flags &= ~C_INITIALIZED;
+	return rc;
+}
+
+int mdb_drop(MDB_txn *txn, MDB_dbi dbi, int del)
+{
+	MDB_cursor *mc, *m2;
+	int rc;
+
+	if ((unsigned)del > 1 || !TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+
+	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY))
+		return EACCES;
+
+	if (TXN_DBI_CHANGED(txn, dbi))
+		return MDB_BAD_DBI;
+
+	rc = mdb_cursor_open(txn, dbi, &mc);
+	if (rc)
+		return rc;
+
+	rc = mdb_drop0(mc, mc->mc_db->md_flags & MDB_DUPSORT);
+	/* Invalidate the dropped DB's cursors */
+	for (m2 = txn->mt_cursors[dbi]; m2; m2 = m2->mc_next)
+		m2->mc_flags &= ~(C_INITIALIZED|C_EOF);
+	if (rc)
+		goto leave;
+
+	/* Can't delete the main DB */
+	if (del && dbi >= CORE_DBS) {
+		rc = mdb_del0(txn, MAIN_DBI, &mc->mc_dbx->md_name, NULL, F_SUBDATA);
+		if (!rc) {
+			txn->mt_dbflags[dbi] = DB_STALE;
+			mdb_dbi_close(txn->mt_env, dbi);
+		} else {
+			txn->mt_flags |= MDB_TXN_ERROR;
+		}
+	} else {
+		/* reset the DB record, mark it dirty */
+		txn->mt_dbflags[dbi] |= DB_DIRTY;
+		txn->mt_dbs[dbi].md_depth = 0;
+		txn->mt_dbs[dbi].md_branch_pages = 0;
+		txn->mt_dbs[dbi].md_leaf_pages = 0;
+		txn->mt_dbs[dbi].md_overflow_pages = 0;
+		txn->mt_dbs[dbi].md_entries = 0;
+		txn->mt_dbs[dbi].md_root = P_INVALID;
+
+		txn->mt_flags |= MDB_TXN_DIRTY;
+	}
+leave:
+	mdb_cursor_close(mc);
+	return rc;
+}
+
+int mdb_set_compare(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp)
+{
+	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+
+	txn->mt_dbxs[dbi].md_cmp = cmp;
+	return MDB_SUCCESS;
+}
+
+int mdb_set_dupsort(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp)
+{
+	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+
+	txn->mt_dbxs[dbi].md_dcmp = cmp;
+	return MDB_SUCCESS;
+}
+
+int mdb_set_relfunc(MDB_txn *txn, MDB_dbi dbi, MDB_rel_func *rel)
+{
+	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+
+	txn->mt_dbxs[dbi].md_rel = rel;
+	return MDB_SUCCESS;
+}
+
+int mdb_set_relctx(MDB_txn *txn, MDB_dbi dbi, void *ctx)
+{
+	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
+		return EINVAL;
+
+	txn->mt_dbxs[dbi].md_relctx = ctx;
+	return MDB_SUCCESS;
+}
+
+int ESECT
+mdb_env_get_maxkeysize(MDB_env *env)
+{
+	return ENV_MAXKEY(env);
+}
+
+int ESECT
+mdb_reader_list(MDB_env *env, MDB_msg_func *func, void *ctx)
+{
+	unsigned int i, rdrs;
+	MDB_reader *mr;
+	char buf[64];
+	int rc = 0, first = 1;
+
+	if (!env || !func)
+		return -1;
+	if (!env->me_txns) {
+		return func("(no reader locks)\n", ctx);
+	}
+	rdrs = env->me_txns->mti_numreaders;
+	mr = env->me_txns->mti_readers;
+	for (i=0; i<rdrs; i++) {
+		if (mr[i].mr_pid) {
+			txnid_t	txnid = mr[i].mr_txnid;
+			sprintf(buf, txnid == (txnid_t)-1 ?
+				"%10d %"Z"x -\n" : "%10d %"Z"x %"Z"u\n",
+				(int)mr[i].mr_pid, (size_t)mr[i].mr_tid, txnid);
+			if (first) {
+				first = 0;
+				rc = func("    pid     thread     txnid\n", ctx);
+				if (rc < 0)
+					break;
+			}
+			rc = func(buf, ctx);
+			if (rc < 0)
+				break;
+		}
+	}
+	if (first) {
+		rc = func("(no active readers)\n", ctx);
+	}
+	return rc;
+}
+
+/** Insert pid into list if not already present.
+ * return -1 if already present.
+ */
+static int ESECT
+mdb_pid_insert(MDB_PID_T *ids, MDB_PID_T pid)
+{
+	/* binary search of pid in list */
+	unsigned base = 0;
+	unsigned cursor = 1;
+	int val = 0;
+	unsigned n = ids[0];
+
+	while( 0 < n ) {
+		unsigned pivot = n >> 1;
+		cursor = base + pivot + 1;
+		val = pid - ids[cursor];
+
+		if( val < 0 ) {
+			n = pivot;
+
+		} else if ( val > 0 ) {
+			base = cursor;
+			n -= pivot + 1;
+
+		} else {
+			/* found, so it's a duplicate */
+			return -1;
+		}
+	}
+
+	if( val > 0 ) {
+		++cursor;
+	}
+	ids[0]++;
+	for (n = ids[0]; n > cursor; n--)
+		ids[n] = ids[n-1];
+	ids[n] = pid;
+	return 0;
+}
+
+int ESECT
+mdb_reader_check(MDB_env *env, int *dead)
+{
+	if (!env)
+		return EINVAL;
+	if (dead)
+		*dead = 0;
+	return env->me_txns ? mdb_reader_check0(env, 0, dead) : MDB_SUCCESS;
+}
+
+/** As #mdb_reader_check(). \b rlocked is set if caller locked #me_rmutex. */
+static int ESECT
+mdb_reader_check0(MDB_env *env, int rlocked, int *dead)
+{
+	mdb_mutexref_t rmutex = rlocked ? NULL : env->me_rmutex;
+	unsigned int i, j, rdrs;
+	MDB_reader *mr;
+	MDB_PID_T *pids, pid;
+	int rc = MDB_SUCCESS, count = 0;
+
+	rdrs = env->me_txns->mti_numreaders;
+	pids = malloc((rdrs+1) * sizeof(MDB_PID_T));
+	if (!pids)
+		return ENOMEM;
+	pids[0] = 0;
+	mr = env->me_txns->mti_readers;
+	for (i=0; i<rdrs; i++) {
+		pid = mr[i].mr_pid;
+		if (pid && pid != env->me_pid) {
+			if (mdb_pid_insert(pids, pid) == 0) {
+				if (!mdb_reader_pid(env, Pidcheck, pid)) {
+					/* Stale reader found */
+					j = i;
+					if (rmutex) {
+						if ((rc = LOCK_MUTEX0(rmutex)) != 0) {
+							if ((rc = mdb_mutex_failed(env, rmutex, rc)))
+								break;
+							rdrs = 0; /* the above checked all readers */
+						} else {
+							/* Recheck, a new process may have reused pid */
+							if (mdb_reader_pid(env, Pidcheck, pid))
+								j = rdrs;
+						}
+					}
+					for (; j<rdrs; j++)
+							if (mr[j].mr_pid == pid) {
+								DPRINTF(("clear stale reader pid %u txn %"Z"d",
+									(unsigned) pid, mr[j].mr_txnid));
+								mr[j].mr_pid = 0;
+								count++;
+							}
+					if (rmutex)
+						UNLOCK_MUTEX(rmutex);
+				}
+			}
+		}
+	}
+	free(pids);
+	if (dead)
+		*dead = count;
+	return rc;
+}
+
+#ifdef MDB_ROBUST_SUPPORTED
+/** Handle #LOCK_MUTEX0() failure.
+ * Try to repair the lock file if the mutex owner died.
+ * @param[in] env	the environment handle
+ * @param[in] mutex	LOCK_MUTEX0() mutex
+ * @param[in] rc	LOCK_MUTEX0() error (nonzero)
+ * @return 0 on success with the mutex locked, or an error code on failure.
+ */
+static int ESECT
+mdb_mutex_failed(MDB_env *env, mdb_mutexref_t mutex, int rc)
+{
+	int rlocked, rc2;
+	MDB_meta *meta;
+
+	if (rc == MDB_OWNERDEAD) {
+		/* We own the mutex. Clean up after dead previous owner. */
+		rc = MDB_SUCCESS;
+		rlocked = (mutex == env->me_rmutex);
+		if (!rlocked) {
+			/* Keep mti_txnid updated, otherwise next writer can
+			 * overwrite data which latest meta page refers to.
+			 */
+			meta = mdb_env_pick_meta(env);
+			env->me_txns->mti_txnid = meta->mm_txnid;
+			/* env is hosed if the dead thread was ours */
+			if (env->me_txn) {
+				env->me_flags |= MDB_FATAL_ERROR;
+				env->me_txn = NULL;
+				rc = MDB_PANIC;
+			}
+		}
+		DPRINTF(("%cmutex owner died, %s", (rlocked ? 'r' : 'w'),
+			(rc ? "this process' env is hosed" : "recovering")));
+		rc2 = mdb_reader_check0(env, rlocked, NULL);
+		if (rc2 == 0)
+			rc2 = mdb_mutex_consistent(mutex);
+		if (rc || (rc = rc2)) {
+			DPRINTF(("LOCK_MUTEX recovery failed, %s", mdb_strerror(rc)));
+			UNLOCK_MUTEX(mutex);
+		}
+	} else {
+#ifdef _WIN32
+		rc = ErrCode();
+#endif
+		DPRINTF(("LOCK_MUTEX failed, %s", mdb_strerror(rc)));
+	}
+
+	return rc;
+}
+#endif	/* MDB_ROBUST_SUPPORTED */
+
+#if defined(_WIN32)
+/** Convert \b src to new wchar_t[] string with room for \b xtra extra chars */
+static int ESECT
+utf8_to_utf16(const char *src, MDB_name *dst, int xtra)
+{
+	int rc, need = 0;
+	wchar_t *result = NULL;
+	for (;;) {					/* malloc result, then fill it in */
+		need = MultiByteToWideChar(CP_UTF8, 0, src, -1, result, need);
+		if (!need) {
+			rc = ErrCode();
+			free(result);
+			return rc;
+		}
+		if (!result) {
+			result = malloc(sizeof(wchar_t) * (need + xtra));
+			if (!result)
+				return ENOMEM;
+			continue;
+		}
+		dst->mn_alloced = 1;
+		dst->mn_len = need - 1;
+		dst->mn_val = result;
+		return MDB_SUCCESS;
+	}
+}
+#endif /* defined(_WIN32) */
+/** @} */
diff --git a/src/contrib/lmdb/midl.c b/src/contrib/lmdb/midl.c
new file mode 100644
index 0000000..7b2b77e
--- /dev/null
+++ b/src/contrib/lmdb/midl.c
@@ -0,0 +1,359 @@
+/**	@file midl.c
+ *	@brief ldap bdb back-end ID List functions */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 2000-2018 The OpenLDAP Foundation.
+ * Portions Copyright 2001-2018 Howard Chu, Symas Corp.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+#include <limits.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/types.h>
+#include "midl.h"
+
+/** @defgroup internal	LMDB Internals
+ *	@{
+ */
+/** @defgroup idls	ID List Management
+ *	@{
+ */
+#define CMP(x,y)	 ( (x) < (y) ? -1 : (x) > (y) )
+
+unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id )
+{
+	/*
+	 * binary search of id in ids
+	 * if found, returns position of id
+	 * if not found, returns first position greater than id
+	 */
+	unsigned base = 0;
+	unsigned cursor = 1;
+	int val = 0;
+	unsigned n = ids[0];
+
+	while( 0 < n ) {
+		unsigned pivot = n >> 1;
+		cursor = base + pivot + 1;
+		val = CMP( ids[cursor], id );
+
+		if( val < 0 ) {
+			n = pivot;
+
+		} else if ( val > 0 ) {
+			base = cursor;
+			n -= pivot + 1;
+
+		} else {
+			return cursor;
+		}
+	}
+
+	if( val > 0 ) {
+		++cursor;
+	}
+	return cursor;
+}
+
+#if 0	/* superseded by append/sort */
+int mdb_midl_insert( MDB_IDL ids, MDB_ID id )
+{
+	unsigned x, i;
+
+	x = mdb_midl_search( ids, id );
+	assert( x > 0 );
+
+	if( x < 1 ) {
+		/* internal error */
+		return -2;
+	}
+
+	if ( x <= ids[0] && ids[x] == id ) {
+		/* duplicate */
+		assert(0);
+		return -1;
+	}
+
+	if ( ++ids[0] >= MDB_IDL_DB_MAX ) {
+		/* no room */
+		--ids[0];
+		return -2;
+
+	} else {
+		/* insert id */
+		for (i=ids[0]; i>x; i--)
+			ids[i] = ids[i-1];
+		ids[x] = id;
+	}
+
+	return 0;
+}
+#endif
+
+MDB_IDL mdb_midl_alloc(int num)
+{
+	MDB_IDL ids = malloc((num+2) * sizeof(MDB_ID));
+	if (ids) {
+		*ids++ = num;
+		*ids = 0;
+	}
+	return ids;
+}
+
+void mdb_midl_free(MDB_IDL ids)
+{
+	if (ids)
+		free(ids-1);
+}
+
+void mdb_midl_shrink( MDB_IDL *idp )
+{
+	MDB_IDL ids = *idp;
+	if (*(--ids) > MDB_IDL_UM_MAX &&
+		(ids = realloc(ids, (MDB_IDL_UM_MAX+2) * sizeof(MDB_ID))))
+	{
+		*ids++ = MDB_IDL_UM_MAX;
+		*idp = ids;
+	}
+}
+
+static int mdb_midl_grow( MDB_IDL *idp, int num )
+{
+	MDB_IDL idn = *idp-1;
+	/* grow it */
+	idn = realloc(idn, (*idn + num + 2) * sizeof(MDB_ID));
+	if (!idn)
+		return ENOMEM;
+	*idn++ += num;
+	*idp = idn;
+	return 0;
+}
+
+int mdb_midl_need( MDB_IDL *idp, unsigned num )
+{
+	MDB_IDL ids = *idp;
+	num += ids[0];
+	if (num > ids[-1]) {
+		num = (num + num/4 + (256 + 2)) & -256;
+		if (!(ids = realloc(ids-1, num * sizeof(MDB_ID))))
+			return ENOMEM;
+		*ids++ = num - 2;
+		*idp = ids;
+	}
+	return 0;
+}
+
+int mdb_midl_append( MDB_IDL *idp, MDB_ID id )
+{
+	MDB_IDL ids = *idp;
+	/* Too big? */
+	if (ids[0] >= ids[-1]) {
+		if (mdb_midl_grow(idp, MDB_IDL_UM_MAX))
+			return ENOMEM;
+		ids = *idp;
+	}
+	ids[0]++;
+	ids[ids[0]] = id;
+	return 0;
+}
+
+int mdb_midl_append_list( MDB_IDL *idp, MDB_IDL app )
+{
+	MDB_IDL ids = *idp;
+	/* Too big? */
+	if (ids[0] + app[0] >= ids[-1]) {
+		if (mdb_midl_grow(idp, app[0]))
+			return ENOMEM;
+		ids = *idp;
+	}
+	memcpy(&ids[ids[0]+1], &app[1], app[0] * sizeof(MDB_ID));
+	ids[0] += app[0];
+	return 0;
+}
+
+int mdb_midl_append_range( MDB_IDL *idp, MDB_ID id, unsigned n )
+{
+	MDB_ID *ids = *idp, len = ids[0];
+	/* Too big? */
+	if (len + n > ids[-1]) {
+		if (mdb_midl_grow(idp, n | MDB_IDL_UM_MAX))
+			return ENOMEM;
+		ids = *idp;
+	}
+	ids[0] = len + n;
+	ids += len;
+	while (n)
+		ids[n--] = id++;
+	return 0;
+}
+
+void mdb_midl_xmerge( MDB_IDL idl, MDB_IDL merge )
+{
+	MDB_ID old_id, merge_id, i = merge[0], j = idl[0], k = i+j, total = k;
+	idl[0] = (MDB_ID)-1;		/* delimiter for idl scan below */
+	old_id = idl[j];
+	while (i) {
+		merge_id = merge[i--];
+		for (; old_id < merge_id; old_id = idl[--j])
+			idl[k--] = old_id;
+		idl[k--] = merge_id;
+	}
+	idl[0] = total;
+}
+
+/* Quicksort + Insertion sort for small arrays */
+
+#define SMALL	8
+#define	MIDL_SWAP(a,b)	{ itmp=(a); (a)=(b); (b)=itmp; }
+
+void
+mdb_midl_sort( MDB_IDL ids )
+{
+	/* Max possible depth of int-indexed tree * 2 items/level */
+	int istack[sizeof(int)*CHAR_BIT * 2];
+	int i,j,k,l,ir,jstack;
+	MDB_ID a, itmp;
+
+	ir = (int)ids[0];
+	l = 1;
+	jstack = 0;
+	for(;;) {
+		if (ir - l < SMALL) {	/* Insertion sort */
+			for (j=l+1;j<=ir;j++) {
+				a = ids[j];
+				for (i=j-1;i>=1;i--) {
+					if (ids[i] >= a) break;
+					ids[i+1] = ids[i];
+				}
+				ids[i+1] = a;
+			}
+			if (jstack == 0) break;
+			ir = istack[jstack--];
+			l = istack[jstack--];
+		} else {
+			k = (l + ir) >> 1;	/* Choose median of left, center, right */
+			MIDL_SWAP(ids[k], ids[l+1]);
+			if (ids[l] < ids[ir]) {
+				MIDL_SWAP(ids[l], ids[ir]);
+			}
+			if (ids[l+1] < ids[ir]) {
+				MIDL_SWAP(ids[l+1], ids[ir]);
+			}
+			if (ids[l] < ids[l+1]) {
+				MIDL_SWAP(ids[l], ids[l+1]);
+			}
+			i = l+1;
+			j = ir;
+			a = ids[l+1];
+			for(;;) {
+				do i++; while(ids[i] > a);
+				do j--; while(ids[j] < a);
+				if (j < i) break;
+				MIDL_SWAP(ids[i],ids[j]);
+			}
+			ids[l+1] = ids[j];
+			ids[j] = a;
+			jstack += 2;
+			if (ir-i+1 >= j-l) {
+				istack[jstack] = ir;
+				istack[jstack-1] = i;
+				ir = j-1;
+			} else {
+				istack[jstack] = j-1;
+				istack[jstack-1] = l;
+				l = i;
+			}
+		}
+	}
+}
+
+unsigned mdb_mid2l_search( MDB_ID2L ids, MDB_ID id )
+{
+	/*
+	 * binary search of id in ids
+	 * if found, returns position of id
+	 * if not found, returns first position greater than id
+	 */
+	unsigned base = 0;
+	unsigned cursor = 1;
+	int val = 0;
+	unsigned n = (unsigned)ids[0].mid;
+
+	while( 0 < n ) {
+		unsigned pivot = n >> 1;
+		cursor = base + pivot + 1;
+		val = CMP( id, ids[cursor].mid );
+
+		if( val < 0 ) {
+			n = pivot;
+
+		} else if ( val > 0 ) {
+			base = cursor;
+			n -= pivot + 1;
+
+		} else {
+			return cursor;
+		}
+	}
+
+	if( val > 0 ) {
+		++cursor;
+	}
+	return cursor;
+}
+
+int mdb_mid2l_insert( MDB_ID2L ids, MDB_ID2 *id )
+{
+	unsigned x, i;
+
+	x = mdb_mid2l_search( ids, id->mid );
+
+	if( x < 1 ) {
+		/* internal error */
+		return -2;
+	}
+
+	if ( x <= ids[0].mid && ids[x].mid == id->mid ) {
+		/* duplicate */
+		return -1;
+	}
+
+	if ( ids[0].mid >= MDB_IDL_UM_MAX ) {
+		/* too big */
+		return -2;
+
+	} else {
+		/* insert id */
+		ids[0].mid++;
+		for (i=(unsigned)ids[0].mid; i>x; i--)
+			ids[i] = ids[i-1];
+		ids[x] = *id;
+	}
+
+	return 0;
+}
+
+int mdb_mid2l_append( MDB_ID2L ids, MDB_ID2 *id )
+{
+	/* Too big? */
+	if (ids[0].mid >= MDB_IDL_UM_MAX) {
+		return -2;
+	}
+	ids[0].mid++;
+	ids[ids[0].mid] = *id;
+	return 0;
+}
+
+/** @} */
+/** @} */
diff --git a/src/contrib/lmdb/midl.h b/src/contrib/lmdb/midl.h
new file mode 100644
index 0000000..1aa374c
--- /dev/null
+++ b/src/contrib/lmdb/midl.h
@@ -0,0 +1,186 @@
+/**	@file midl.h
+ *	@brief LMDB ID List header file.
+ *
+ *	This file was originally part of back-bdb but has been
+ *	modified for use in libmdb. Most of the macros defined
+ *	in this file are unused, just left over from the original.
+ *
+ *	This file is only used internally in libmdb and its definitions
+ *	are not exposed publicly.
+ */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 2000-2018 The OpenLDAP Foundation.
+ * Portions Copyright 2001-2018 Howard Chu, Symas Corp.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+#ifndef _MDB_MIDL_H_
+#define _MDB_MIDL_H_
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** @defgroup internal	LMDB Internals
+ *	@{
+ */
+
+/** @defgroup idls	ID List Management
+ *	@{
+ */
+	/** A generic unsigned ID number. These were entryIDs in back-bdb.
+	 *	Preferably it should have the same size as a pointer.
+	 */
+typedef size_t MDB_ID;
+
+	/** An IDL is an ID List, a sorted array of IDs. The first
+	 * element of the array is a counter for how many actual
+	 * IDs are in the list. In the original back-bdb code, IDLs are
+	 * sorted in ascending order. For libmdb IDLs are sorted in
+	 * descending order.
+	 */
+typedef MDB_ID *MDB_IDL;
+
+/* IDL sizes - likely should be even bigger
+ *   limiting factors: sizeof(ID), thread stack size
+ */
+#define	MDB_IDL_LOGN	16	/* DB_SIZE is 2^16, UM_SIZE is 2^17 */
+#define MDB_IDL_DB_SIZE		(1<<MDB_IDL_LOGN)
+#define MDB_IDL_UM_SIZE		(1<<(MDB_IDL_LOGN+1))
+
+#define MDB_IDL_DB_MAX		(MDB_IDL_DB_SIZE-1)
+#define MDB_IDL_UM_MAX		(MDB_IDL_UM_SIZE-1)
+
+#define MDB_IDL_SIZEOF(ids)		(((ids)[0]+1) * sizeof(MDB_ID))
+#define MDB_IDL_IS_ZERO(ids) ( (ids)[0] == 0 )
+#define MDB_IDL_CPY( dst, src ) (memcpy( dst, src, MDB_IDL_SIZEOF( src ) ))
+#define MDB_IDL_FIRST( ids )	( (ids)[1] )
+#define MDB_IDL_LAST( ids )		( (ids)[(ids)[0]] )
+
+	/** Current max length of an #mdb_midl_alloc()ed IDL */
+#define MDB_IDL_ALLOCLEN( ids )	( (ids)[-1] )
+
+	/** Append ID to IDL. The IDL must be big enough. */
+#define mdb_midl_xappend(idl, id) do { \
+		MDB_ID *xidl = (idl), xlen = ++(xidl[0]); \
+		xidl[xlen] = (id); \
+	} while (0)
+
+	/** Search for an ID in an IDL.
+	 * @param[in] ids	The IDL to search.
+	 * @param[in] id	The ID to search for.
+	 * @return	The index of the first ID greater than or equal to \b id.
+	 */
+unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id );
+
+	/** Allocate an IDL.
+	 * Allocates memory for an IDL of the given size.
+	 * @return	IDL on success, NULL on failure.
+	 */
+MDB_IDL mdb_midl_alloc(int num);
+
+	/** Free an IDL.
+	 * @param[in] ids	The IDL to free.
+	 */
+void mdb_midl_free(MDB_IDL ids);
+
+	/** Shrink an IDL.
+	 * Return the IDL to the default size if it has grown larger.
+	 * @param[in,out] idp	Address of the IDL to shrink.
+	 */
+void mdb_midl_shrink(MDB_IDL *idp);
+
+	/** Make room for num additional elements in an IDL.
+	 * @param[in,out] idp	Address of the IDL.
+	 * @param[in] num	Number of elements to make room for.
+	 * @return	0 on success, ENOMEM on failure.
+	 */
+int mdb_midl_need(MDB_IDL *idp, unsigned num);
+
+	/** Append an ID onto an IDL.
+	 * @param[in,out] idp	Address of the IDL to append to.
+	 * @param[in] id	The ID to append.
+	 * @return	0 on success, ENOMEM if the IDL is too large.
+	 */
+int mdb_midl_append( MDB_IDL *idp, MDB_ID id );
+
+	/** Append an IDL onto an IDL.
+	 * @param[in,out] idp	Address of the IDL to append to.
+	 * @param[in] app	The IDL to append.
+	 * @return	0 on success, ENOMEM if the IDL is too large.
+	 */
+int mdb_midl_append_list( MDB_IDL *idp, MDB_IDL app );
+
+	/** Append an ID range onto an IDL.
+	 * @param[in,out] idp	Address of the IDL to append to.
+	 * @param[in] id	The lowest ID to append.
+	 * @param[in] n		Number of IDs to append.
+	 * @return	0 on success, ENOMEM if the IDL is too large.
+	 */
+int mdb_midl_append_range( MDB_IDL *idp, MDB_ID id, unsigned n );
+
+	/** Merge an IDL onto an IDL. The destination IDL must be big enough.
+	 * @param[in] idl	The IDL to merge into.
+	 * @param[in] merge	The IDL to merge.
+	 */
+void mdb_midl_xmerge( MDB_IDL idl, MDB_IDL merge );
+
+	/** Sort an IDL.
+	 * @param[in,out] ids	The IDL to sort.
+	 */
+void mdb_midl_sort( MDB_IDL ids );
+
+	/** An ID2 is an ID/pointer pair.
+	 */
+typedef struct MDB_ID2 {
+	MDB_ID mid;		/**< The ID */
+	void *mptr;		/**< The pointer */
+} MDB_ID2;
+
+	/** An ID2L is an ID2 List, a sorted array of ID2s.
+	 * The first element's \b mid member is a count of how many actual
+	 * elements are in the array. The \b mptr member of the first element is unused.
+	 * The array is sorted in ascending order by \b mid.
+	 */
+typedef MDB_ID2 *MDB_ID2L;
+
+	/** Search for an ID in an ID2L.
+	 * @param[in] ids	The ID2L to search.
+	 * @param[in] id	The ID to search for.
+	 * @return	The index of the first ID2 whose \b mid member is greater than or equal to \b id.
+	 */
+unsigned mdb_mid2l_search( MDB_ID2L ids, MDB_ID id );
+
+
+	/** Insert an ID2 into a ID2L.
+	 * @param[in,out] ids	The ID2L to insert into.
+	 * @param[in] id	The ID2 to insert.
+	 * @return	0 on success, -1 if the ID was already present in the ID2L.
+	 */
+int mdb_mid2l_insert( MDB_ID2L ids, MDB_ID2 *id );
+
+	/** Append an ID2 into a ID2L.
+	 * @param[in,out] ids	The ID2L to append into.
+	 * @param[in] id	The ID2 to append.
+	 * @return	0 on success, -2 if the ID2L is too big.
+	 */
+int mdb_mid2l_append( MDB_ID2L ids, MDB_ID2 *id );
+
+/** @} */
+/** @} */
+#ifdef __cplusplus
+}
+#endif
+#endif	/* _MDB_MIDL_H_ */
diff --git a/src/contrib/macros.h b/src/contrib/macros.h
new file mode 100644
index 0000000..1db2241
--- /dev/null
+++ b/src/contrib/macros.h
@@ -0,0 +1,43 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Common macros.
+ */
+
+#pragma once
+
+/*! \brief Eliminate compiler warning with unused parameters. */
+#define UNUSED(param) (void)(param)
+
+#ifndef MIN
+/*! \brief Type-safe minimum macro. */
+#define MIN(a, b) \
+	({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
+
+/*! \brief Type-safe maximum macro. */
+#define MAX(a, b) \
+	({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a > _b ? _a : _b; })
+#endif
+
+#ifndef likely
+/*! \brief Optimize for x to be true value. */
+#define likely(x) __builtin_expect((x), 1)
+#endif
+
+#ifndef unlikely
+/*! \brief Optimize for x to be false value. */
+#define unlikely(x) __builtin_expect((x), 0)
+#endif
diff --git a/src/contrib/mempattern.c b/src/contrib/mempattern.c
new file mode 100644
index 0000000..74add91
--- /dev/null
+++ b/src/contrib/mempattern.c
@@ -0,0 +1,122 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+
+#include "contrib/mempattern.h"
+#include "contrib/string.h"
+#include "contrib/ucw/mempool.h"
+
+static void mm_nofree(void *p)
+{
+	/* nop */
+}
+
+static void *mm_malloc(void *ctx, size_t n)
+{
+	(void)ctx;
+	return malloc(n);
+}
+
+void *mm_alloc(knot_mm_t *mm, size_t size)
+{
+	if (mm) {
+		return mm->alloc(mm->ctx, size);
+	} else {
+		return malloc(size);
+	}
+}
+
+void *mm_calloc(knot_mm_t *mm, size_t nmemb, size_t size)
+{
+	if (nmemb == 0 || size == 0) {
+		return NULL;
+	}
+	if (mm) {
+		size_t total_size = nmemb * size;
+		if (total_size / nmemb != size) { // Overflow check
+			return NULL;
+		}
+		void *mem = mm_alloc(mm, total_size);
+		if (mem == NULL) {
+			return NULL;
+		}
+		return memzero(mem, total_size);
+	} else {
+		return calloc(nmemb, size);
+	}
+}
+
+void *mm_realloc(knot_mm_t *mm, void *what, size_t size, size_t prev_size)
+{
+	if (mm) {
+		void *p = mm->alloc(mm->ctx, size);
+		if (p == NULL) {
+			return NULL;
+		} else {
+			if (what) {
+				memcpy(p, what,
+				       prev_size < size ? prev_size : size);
+			}
+			mm_free(mm, what);
+			return p;
+		}
+	} else {
+		return realloc(what, size);
+	}
+}
+
+char *mm_strdup(knot_mm_t *mm, const char *s)
+{
+	if (s == NULL) {
+		return NULL;
+	}
+	if (mm) {
+		size_t len = strlen(s) + 1;
+		void *mem = mm_alloc(mm, len);
+		if (mem == NULL) {
+			return NULL;
+		}
+		return memcpy(mem, s, len);
+	} else {
+		return strdup(s);
+	}
+}
+
+void mm_free(knot_mm_t *mm, void *what)
+{
+	if (mm) {
+		if (mm->free) {
+			mm->free(what);
+		}
+	} else {
+		free(what);
+	}
+}
+
+void mm_ctx_init(knot_mm_t *mm)
+{
+	mm->ctx = NULL;
+	mm->alloc = mm_malloc;
+	mm->free = free;
+}
+
+void mm_ctx_mempool(knot_mm_t *mm, size_t chunk_size)
+{
+	mm->ctx = mp_new(chunk_size);
+	mm->alloc = (knot_mm_alloc_t)mp_alloc;
+	mm->free = mm_nofree;
+}
diff --git a/src/contrib/mempattern.h b/src/contrib/mempattern.h
new file mode 100644
index 0000000..1c5d9a2
--- /dev/null
+++ b/src/contrib/mempattern.h
@@ -0,0 +1,46 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Memory allocation related functions.
+ */
+
+#pragma once
+
+#include "libknot/mm_ctx.h"
+
+/*! \brief Default memory block size. */
+#define MM_DEFAULT_BLKSIZE 4096
+
+/*! \brief Allocs using 'mm' if any, uses system malloc() otherwise. */
+void *mm_alloc(knot_mm_t *mm, size_t size);
+
+/*! \brief Callocs using 'mm' if any, uses system calloc() otherwise. */
+void *mm_calloc(knot_mm_t *mm, size_t nmemb, size_t size);
+
+/*! \brief Reallocs using 'mm' if any, uses system realloc() otherwise. */
+void *mm_realloc(knot_mm_t *mm, void *what, size_t size, size_t prev_size);
+
+/*! \brief Strdups using 'mm' if any, uses system strdup() otherwise. */
+char *mm_strdup(knot_mm_t *mm, const char *s);
+
+/*! \brief Free using 'mm' if any, uses system free() otherwise. */
+void mm_free(knot_mm_t *mm, void *what);
+
+/*! \brief Initialize default memory allocation context. */
+void mm_ctx_init(knot_mm_t *mm);
+
+/*! \brief Memory pool context. */
+void mm_ctx_mempool(knot_mm_t *mm, size_t chunk_size);
diff --git a/src/contrib/net.c b/src/contrib/net.c
new file mode 100644
index 0000000..81fc8ef
--- /dev/null
+++ b/src/contrib/net.c
@@ -0,0 +1,598 @@
+/*  Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <netinet/in.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+#include "libknot/errcode.h"
+#include "contrib/net.h"
+#include "contrib/sockaddr.h"
+
+/*
+ * OS X doesn't support MSG_NOSIGNAL. Use SO_NOSIGPIPE socket option instead.
+ */
+#if defined(__APPLE__) && !defined(MSG_NOSIGNAL)
+#  define MSG_NOSIGNAL 0
+#  define osx_block_sigpipe(sock) sockopt_enable(sock, SOL_SOCKET, SO_NOSIGPIPE)
+#else
+#  define osx_block_sigpipe(sock) KNOT_EOK
+#endif
+
+/*!
+ * \brief Enable socket option.
+ */
+static int sockopt_enable(int sock, int level, int optname)
+{
+	const int enable = 1;
+	if (setsockopt(sock, level, optname, &enable, sizeof(enable)) != 0) {
+		return knot_map_errno();
+	}
+
+	return KNOT_EOK;
+}
+
+/*!
+ * \brief Create a non-blocking socket.
+ *
+ * Prefer SOCK_NONBLOCK if available to save one fcntl() syscall.
+ *
+ */
+static int socket_create(int family, int type, int proto)
+{
+#ifdef SOCK_NONBLOCK
+	type |= SOCK_NONBLOCK;
+#endif
+	int sock = socket(family, type, proto);
+	if (sock < 0) {
+		return knot_map_errno();
+	}
+
+#ifndef SOCK_NONBLOCK
+	if (fcntl(sock, F_SETFL, O_NONBLOCK) != 0) {
+		int ret = knot_map_errno();
+		close(sock);
+		return ret;
+	}
+#endif
+
+	int ret = osx_block_sigpipe(sock);
+	if (ret != KNOT_EOK) {
+		return ret;
+	}
+
+	return sock;
+}
+
+int net_unbound_socket(int type, const struct sockaddr *sa)
+{
+	if (sa == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	/* Create socket. */
+	return socket_create(sa->sa_family, type, 0);
+}
+
+struct option {
+	int level;
+	int name;
+};
+
+/*!
+ * \brief Get setsock option for binding non-local address.
+ */
+static const struct option *nonlocal_option(int family)
+{
+	static const struct option ipv4 = {
+		#if defined(IP_FREEBIND)
+			IPPROTO_IP, IP_FREEBIND
+		#elif defined(IP_BINDANY)
+			IPPROTO_IP, IP_BINDANY
+		#else
+			0, 0
+		#endif
+	};
+
+	static const struct option ipv6 = {
+		#if defined(IP_FREEBIND)
+			IPPROTO_IP, IP_FREEBIND
+		#elif defined(IPV6_BINDANY)
+			IPPROTO_IPV6, IPV6_BINDANY
+		#else
+			0, 0
+		#endif
+
+	};
+
+	switch (family) {
+	case AF_INET:  return &ipv4;
+	case AF_INET6: return &ipv6;
+	default:
+		return NULL;
+	}
+}
+
+static int enable_nonlocal(int sock, int family)
+{
+	const struct option *opt = nonlocal_option(family);
+	if (opt == NULL || opt->name == 0) {
+		return KNOT_ENOTSUP;
+	}
+
+	return sockopt_enable(sock, opt->level, opt->name);
+}
+
+static int enable_reuseport(int sock)
+{
+#ifdef ENABLE_REUSEPORT
+	return sockopt_enable(sock, SOL_SOCKET, SO_REUSEPORT);
+#else
+	return KNOT_ENOTSUP;
+#endif
+}
+
+static void unlink_unix_socket(const struct sockaddr *addr)
+{
+	char path[SOCKADDR_STRLEN] = { 0 };
+	sockaddr_tostr(path, sizeof(path), addr);
+	unlink(path);
+}
+
+int net_bound_socket(int type, const struct sockaddr *sa, enum net_flags flags)
+{
+	/* Create socket. */
+	int sock = net_unbound_socket(type, sa);
+	if (sock < 0) {
+		return sock;
+	}
+
+	/* Unlink UNIX sock if exists. */
+	if (sa->sa_family == AF_UNIX) {
+		unlink_unix_socket(sa);
+	}
+
+	/* Reuse old address if taken. */
+	int ret = sockopt_enable(sock, SOL_SOCKET, SO_REUSEADDR);
+	if (ret != KNOT_EOK) {
+		close(sock);
+		return ret;
+	}
+
+	/* Don't bind IPv4 for IPv6 any address. */
+	if (sa->sa_family == AF_INET6) {
+		ret = sockopt_enable(sock, IPPROTO_IPV6, IPV6_V6ONLY);
+		if (ret != KNOT_EOK) {
+			close(sock);
+			return ret;
+		}
+	}
+
+	/* Allow bind to non-local address. */
+	if (flags & NET_BIND_NONLOCAL) {
+		ret = enable_nonlocal(sock, sa->sa_family);
+		if (ret != KNOT_EOK) {
+			close(sock);
+			return ret;
+		}
+	}
+
+	/* Allow to bind the same address by multiple threads. */
+	if (flags & NET_BIND_MULTIPLE) {
+		ret = enable_reuseport(sock);
+		if (ret != KNOT_EOK) {
+			close(sock);
+			return ret;
+		}
+	}
+
+	/* Bind to specified address. */
+	ret = bind(sock, sa, sockaddr_len(sa));
+	if (ret < 0) {
+		ret = knot_map_errno();
+		close(sock);
+		return ret;
+	}
+
+	return sock;
+}
+
+int net_connected_socket(int type, const struct sockaddr *dst_addr,
+                         const struct sockaddr *src_addr)
+{
+	if (dst_addr == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	/* Check port. */
+	if (sockaddr_port(dst_addr) == 0) {
+		return KNOT_NET_EADDR;
+	}
+
+	/* Bind to specific source address - if set. */
+	int sock = -1;
+	if (src_addr && src_addr->sa_family != AF_UNSPEC) {
+		sock = net_bound_socket(type, src_addr, 0);
+	} else {
+		sock = net_unbound_socket(type, dst_addr);
+	}
+	if (sock < 0) {
+		return sock;
+	}
+
+	/* Connect to destination. */
+	const struct sockaddr *sa = (const struct sockaddr *)dst_addr;
+	int ret = connect(sock, sa, sockaddr_len(sa));
+	if (ret != 0 && errno != EINPROGRESS) {
+		ret = knot_map_errno();
+		close(sock);
+		return ret;
+	}
+
+	return sock;
+}
+
+bool net_is_connected(int sock)
+{
+	struct sockaddr_storage ss;
+	socklen_t len = sizeof(ss);
+	return (getpeername(sock, (struct sockaddr *)&ss, &len) == 0);
+}
+
+int net_socktype(int sock)
+{
+	int type;
+	socklen_t size = sizeof(type);
+
+	if (getsockopt(sock, SOL_SOCKET, SO_TYPE, &type, &size) == 0) {
+		return type;
+	} else {
+		return AF_UNSPEC;
+	}
+}
+
+bool net_is_stream(int sock)
+{
+	return net_socktype(sock) == SOCK_STREAM;
+}
+
+int net_accept(int sock, struct sockaddr_storage *addr)
+{
+	socklen_t sa_len = sizeof(*addr);
+
+	int remote = -1;
+
+#if defined(HAVE_ACCEPT4) && defined(SOCK_NONBLOCK)
+	remote = accept4(sock, (struct sockaddr *)addr, &sa_len, SOCK_NONBLOCK);
+	if (remote < 0) {
+		return knot_map_errno();
+	}
+#else
+	remote = accept(sock, (struct sockaddr *)addr, &sa_len);
+	if (fcntl(remote, F_SETFL, O_NONBLOCK) != 0) {
+		int error = knot_map_errno();
+		close(remote);
+		return error;
+	}
+#endif
+
+	return remote;
+}
+
+/* -- I/O interface handling partial  -------------------------------------- */
+
+/*!
+ * \brief Perform \a poll() on one socket.
+ */
+static int poll_one(int fd, int events, int timeout_ms)
+{
+	struct pollfd pfd = {
+		.fd = fd,
+		.events = events
+	};
+
+	return poll(&pfd, 1, timeout_ms);
+}
+
+/*!
+ * \brief Check if we should wait for I/O readiness.
+ *
+ * \param error  \a errno set by the failed I/O operation.
+ */
+static bool io_should_wait(int error)
+{
+	/* socket data not ready */
+	if (error == EAGAIN || error == EWOULDBLOCK) {
+		return true;
+	}
+
+#ifndef __linux__
+	/* FreeBSD: connection in progress */
+	if (error == ENOTCONN) {
+		return true;
+	}
+#endif
+
+	return false;
+}
+
+/*!
+ * \brief I/O operation callbacks.
+ */
+struct io {
+	ssize_t (*process)(int sockfd, struct msghdr *msg);
+	int (*wait)(int sockfd, int timeout_ms);
+};
+
+/*!
+ * \brief Get total size of I/O vector in a message.
+ */
+static size_t msg_iov_len(const struct msghdr *msg)
+{
+	size_t total = 0;
+
+	for (int i = 0; i < msg->msg_iovlen; i++) {
+		total += msg->msg_iov[i].iov_len;
+	}
+
+	return total;
+}
+
+/*!
+ * \brief Shift processed data out of message IO vectors.
+ */
+static void msg_iov_shift(struct msghdr *msg, size_t done)
+{
+	struct iovec *iov = msg->msg_iov;
+	int iovlen = msg->msg_iovlen;
+
+	for (int i = 0; i < iovlen && done > 0; i++) {
+		if (iov[i].iov_len > done) {
+			iov[i].iov_base += done;
+			iov[i].iov_len -= done;
+			done = 0;
+		} else {
+			done -= iov[i].iov_len;
+			msg->msg_iov += 1;
+			msg->msg_iovlen -= 1;
+		}
+	}
+
+	assert(done == 0);
+}
+
+/*!
+ * \brief Perform an I/O operation with a socket with waiting.
+ *
+ * \param oneshot  If set, doesn't wait until the buffer is fully processed.
+ *
+ */
+static ssize_t io_exec(const struct io *io, int fd, struct msghdr *msg,
+                       bool oneshot, int timeout_ms)
+{
+	size_t done = 0;
+	size_t total = msg_iov_len(msg);
+
+	for (;;) {
+		/* Perform I/O. */
+		ssize_t ret = io->process(fd, msg);
+		if (ret == -1 && errno == EINTR) {
+			continue;
+		}
+		if (ret > 0) {
+			done += ret;
+			if (oneshot || done == total) {
+				break;
+			}
+			msg_iov_shift(msg, ret);
+		}
+
+		/* Wait for data readiness. */
+		if (ret > 0 || (ret == -1 && io_should_wait(errno))) {
+			do {
+				ret = io->wait(fd, timeout_ms);
+			} while (ret == -1 && errno == EINTR);
+			if (ret == 1) {
+				continue;
+			} else if (ret == 0) {
+				return KNOT_ETIMEOUT;
+			}
+		}
+
+		/* Disconnected or error. */
+		return KNOT_ECONN;
+	}
+
+	return done;
+}
+
+static ssize_t recv_process(int fd, struct msghdr *msg)
+{
+	return recvmsg(fd, msg, MSG_DONTWAIT | MSG_NOSIGNAL);
+}
+
+static int recv_wait(int fd, int timeout_ms)
+{
+	return poll_one(fd, POLLIN, timeout_ms);
+}
+
+static ssize_t recv_data(int sock, struct msghdr *msg, bool oneshot, int timeout_ms)
+{
+	static const struct io RECV_IO = {
+		.process = recv_process,
+		.wait = recv_wait
+	};
+
+	return io_exec(&RECV_IO, sock, msg, oneshot, timeout_ms);
+}
+
+static ssize_t send_process(int fd, struct msghdr *msg)
+{
+	return sendmsg(fd, msg, MSG_NOSIGNAL);
+}
+
+static int send_wait(int fd, int timeout_ms)
+{
+	return poll_one(fd, POLLOUT, timeout_ms);
+}
+
+static ssize_t send_data(int sock, struct msghdr *msg, int timeout_ms)
+{
+	static const struct io SEND_IO = {
+		.process = send_process,
+		.wait = send_wait
+	};
+
+	return io_exec(&SEND_IO, sock, msg, false, timeout_ms);
+}
+
+/* -- generic stream and datagram I/O -------------------------------------- */
+
+ssize_t net_send(int sock, const uint8_t *buffer, size_t size,
+                 const struct sockaddr *addr, int timeout_ms)
+{
+	if (sock < 0 || buffer == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	struct iovec iov = { 0 };
+	iov.iov_base = (void *)buffer;
+	iov.iov_len = size;
+
+	struct msghdr msg = { 0 };
+	msg.msg_name = (void *)addr;
+	msg.msg_namelen = sockaddr_len(addr);
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	int ret = send_data(sock, &msg, timeout_ms);
+	if (ret < 0) {
+		return ret;
+	} else if (ret != size) {
+		return KNOT_ECONN;
+	}
+
+	return ret;
+}
+
+ssize_t net_recv(int sock, uint8_t *buffer, size_t size,
+                 struct sockaddr_storage *addr, int timeout_ms)
+{
+	if (sock < 0 || buffer == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	struct iovec iov = { 0 };
+	iov.iov_base = buffer;
+	iov.iov_len = size;
+
+	struct msghdr msg = { 0 };
+	msg.msg_name = (void *)addr;
+	msg.msg_namelen = addr ? sizeof(*addr) : 0;
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	return recv_data(sock, &msg, true, timeout_ms);
+}
+
+ssize_t net_dgram_send(int sock, const uint8_t *buffer, size_t size,
+                       const struct sockaddr *addr)
+{
+	return net_send(sock, buffer, size, addr, 0);
+}
+
+ssize_t net_dgram_recv(int sock, uint8_t *buffer, size_t size, int timeout_ms)
+{
+	return net_recv(sock, buffer, size, NULL, timeout_ms);
+}
+
+ssize_t net_stream_send(int sock, const uint8_t *buffer, size_t size, int timeout_ms)
+{
+	return net_send(sock, buffer, size, NULL, timeout_ms);
+}
+
+ssize_t net_stream_recv(int sock, uint8_t *buffer, size_t size, int timeout_ms)
+{
+	return net_recv(sock, buffer, size, NULL, timeout_ms);
+}
+
+/* -- DNS specific I/O ----------------------------------------------------- */
+
+ssize_t net_dns_tcp_send(int sock, const uint8_t *buffer, size_t size, int timeout_ms)
+{
+	if (sock < 0 || buffer == NULL || size > UINT16_MAX) {
+		return KNOT_EINVAL;
+	}
+
+	struct iovec iov[2];
+	uint16_t pktsize = htons(size);
+	iov[0].iov_base = &pktsize;
+	iov[0].iov_len = sizeof(uint16_t);
+	iov[1].iov_base = (void *)buffer;
+	iov[1].iov_len = size;
+
+	struct msghdr msg = { 0 };
+	msg.msg_iov = iov;
+	msg.msg_iovlen = 2;
+
+	ssize_t ret = send_data(sock, &msg, timeout_ms);
+	if (ret < 0) {
+		return ret;
+	}
+
+	return size; /* Do not count the size prefix. */
+}
+
+ssize_t net_dns_tcp_recv(int sock, uint8_t *buffer, size_t size, int timeout_ms)
+{
+	if (sock < 0 || buffer == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	struct iovec iov = { 0 };
+	struct msghdr msg = { 0 };
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	/* Receive size. */
+	uint16_t pktsize = 0;
+	iov.iov_base = &pktsize;
+	iov.iov_len = sizeof(pktsize);
+	int ret = recv_data(sock, &msg, false, timeout_ms);
+	if (ret != sizeof(pktsize)) {
+		return ret;
+	}
+
+	pktsize = ntohs(pktsize);
+
+	/* Check packet size */
+	if (size < pktsize) {
+		return KNOT_ESPACE;
+	}
+
+	/* Receive payload. */
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+	iov.iov_base = buffer;
+	iov.iov_len = pktsize;
+	return recv_data(sock, &msg, false, timeout_ms);
+}
diff --git a/src/contrib/net.h b/src/contrib/net.h
new file mode 100644
index 0000000..1b6b527
--- /dev/null
+++ b/src/contrib/net.h
@@ -0,0 +1,185 @@
+/*  Copyright (C) 2015 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <sys/socket.h>
+
+/*!
+ * \brief Network interface flags.
+ */
+enum net_flags {
+	NET_BIND_NONLOCAL = (1 << 0), //!< Allow to bind unavailable address.
+	NET_BIND_MULTIPLE = (1 << 1), //!< Allow to bind address multiple times.
+};
+
+/*!
+ * \brief Create unbound socket of given family and type.
+ *
+ * \note The socket is set to non-blocking mode.
+ *
+ * \param type  Socket transport type (SOCK_STREAM, SOCK_DGRAM).
+ * \param sa    Socket address.
+ *
+ * \return socket or error code
+ */
+int net_unbound_socket(int type, const struct sockaddr *sa);
+
+/*!
+ * \brief Create socket bound to given address.
+ *
+ * The socket is set to non-blocking mode.
+ *
+ * \param type   Socket transport type (SOCK_STREAM, SOCK_DGRAM).
+ * \param sa     Socket address.
+ * \param flags  Socket binding options.
+ *
+ * \return socket or error code
+ */
+int net_bound_socket(int type, const struct sockaddr *sa, enum net_flags flags);
+
+/*!
+ * \brief Create socket connected (asynchronously) to destination address.
+ *
+ * \note The socket is set to non-blocking mode.
+ *
+ * \param type      Socket transport type (SOCK_STREAM, SOCK_DGRAM).
+ * \param dst_addr  Destination address.
+ * \param src_addr  Source address (can be NULL).
+ *
+ * \return socket or error code
+ */
+int net_connected_socket(int type, const struct sockaddr *dst_addr,
+                         const struct sockaddr *src_addr);
+
+/*!
+ * \brief Return true if the socket is fully connected.
+ *
+ * \param sock  Socket.
+ *
+ * \return true if connected
+ */
+bool net_is_connected(int sock);
+
+/*!
+ * \brief Get socket type (e.g. \a SOCK_STREAM).
+ *
+ * \param sock  Socket.
+ */
+int net_socktype(int sock);
+
+/*!
+ * \brief Check if socket is a SOCK_STREAM socket.
+ */
+bool net_is_stream(int sock);
+
+/*!
+ * \brief Accept a connection on a listening socket.
+ *
+ * \brief The socket is set to non-blocking mode.
+ *
+ * \param sock  Socket
+ * \param addr  Remote address (can be NULL).
+ *
+ * \return socket or error code
+ */
+int net_accept(int sock, struct sockaddr_storage *addr);
+
+/*!
+ * \brief Send a message on a socket.
+ *
+ * The socket can be SOCK_STREAM or SOCK_DGRAM.
+ *
+ * The implementation handles partial-writes automatically.
+ *
+ * \param[in] sock        Socket.
+ * \param[in] buffer      Message buffer.
+ * \param[in] size        Size of the message.
+ * \param[in] addr        Remote address (ignored for SOCK_STREAM).
+ * \param[in] timeout_ms  Write timeout in miliseconds (-1 for infinity,
+ *                        not valid for SOCK_DGRAM).
+ *
+ * \return Number of bytes sent or negative error code.
+ */
+ssize_t net_send(int sock, const uint8_t *buffer, size_t size,
+                 const struct sockaddr *addr, int timeout_ms);
+
+/*!
+ * \brief Receive a message from a socket.
+ *
+ * \param[in]  sock        Socket.
+ * \param[out] buffer      Receiving buffer.
+ * \param[in]  size        Capacity of the receiving buffer.
+ * \param[out] addr        Remote address (can be NULL).
+ * \param[in]  timeout_ms  Read timeout in miliseconds (-1 for infinity).
+ *
+ * \return Number of bytes read or negative error code.
+ */
+ssize_t net_recv(int sock, uint8_t *buffer, size_t size,
+                 struct sockaddr_storage *addr, int timeout_ms);
+
+/*!
+ * \brief Send a message on a SOCK_DGRAM socket.
+ *
+ * \see net_send
+ */
+ssize_t net_dgram_send(int sock, const uint8_t *buffer, size_t size,
+                       const struct sockaddr *addr);
+
+/*!
+ * \brief Receive a message from a SOCK_DGRAM socket.
+ *
+ * \see net_recv
+ */
+ssize_t net_dgram_recv(int sock, uint8_t *buffer, size_t size, int timeout_ms);
+
+/*!
+ * \brief Send a message on a SOCK_STREAM socket.
+ *
+ * \see net_send
+ */
+ssize_t net_stream_send(int sock, const uint8_t *buffer, size_t size, int timeout_ms);
+
+/*!
+ * \brief Receive a message from a SOCK_STREAM socket.
+ *
+ * \see net_recv
+ */
+ssize_t net_stream_recv(int sock, uint8_t *buffer, size_t size, int timeout_ms);
+
+/*!
+ * \brief Send a DNS message on a TCP socket.
+ *
+ * The outgoing message is prefixed with a two-byte value carrying the DNS
+ * message size according to the specification. These two bytes are not
+ * reflected in the return value.
+ *
+ * \see net_send
+ */
+ssize_t net_dns_tcp_send(int sock, const uint8_t *buffer, size_t size, int timeout_ms);
+
+/*!
+ * \brief Receive a DNS message from a TCP socket.
+ *
+ * The first two bytes of the incoming message are interpreted as a DNS message
+ * size according to the specification. These two bytes are not included in
+ * the returned size. Only a complete DNS message is retrieved.
+ *
+ * \see net_recv
+ */
+ssize_t net_dns_tcp_recv(int sock, uint8_t *buffer, size_t size, int timeout_ms);
diff --git a/src/contrib/openbsd/LICENSE b/src/contrib/openbsd/LICENSE
new file mode 100644
index 0000000..e9a1aaa
--- /dev/null
+++ b/src/contrib/openbsd/LICENSE
@@ -0,0 +1,2 @@
+../licenses/0BSD
+../licenses/BSD-3-Clause
\ No newline at end of file
diff --git a/src/contrib/openbsd/siphash.c b/src/contrib/openbsd/siphash.c
new file mode 100644
index 0000000..26b8cfc
--- /dev/null
+++ b/src/contrib/openbsd/siphash.c
@@ -0,0 +1,176 @@
+/*	$OpenBSD: siphash.c,v 1.6 2017/04/12 17:41:49 deraadt Exp $ */
+
+/*-
+ * Copyright (c) 2013 Andre Oppermann <andre@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * SipHash is a family of PRFs SipHash-c-d where the integer parameters c and d
+ * are the number of compression rounds and the number of finalization rounds.
+ * A compression round is identical to a finalization round and this round
+ * function is called SipRound.  Given a 128-bit key k and a (possibly empty)
+ * byte string m, SipHash-c-d returns a 64-bit value SipHash-c-d(k; m).
+ *
+ * Implemented from the paper "SipHash: a fast short-input PRF", 2012.09.18,
+ * by Jean-Philippe Aumasson and Daniel J. Bernstein,
+ * Permanent Document ID b9a943a805fbfc6fde808af9fc0ecdfa
+ * https://131002.net/siphash/siphash.pdf
+ * https://131002.net/siphash/
+ */
+
+#include <string.h>
+
+#include "libknot/endian.h"
+#include "contrib/string.h"
+#include "contrib/openbsd/siphash.h"
+
+static void	SipHash_CRounds(SIPHASH_CTX *, int);
+static void	SipHash_Rounds(SIPHASH_CTX *, int);
+
+void
+SipHash_Init(SIPHASH_CTX *ctx, const SIPHASH_KEY *key)
+{
+	uint64_t k0, k1;
+
+	k0 = le64toh(key->k0);
+	k1 = le64toh(key->k1);
+
+	ctx->v[0] = 0x736f6d6570736575ULL ^ k0;
+	ctx->v[1] = 0x646f72616e646f6dULL ^ k1;
+	ctx->v[2] = 0x6c7967656e657261ULL ^ k0;
+	ctx->v[3] = 0x7465646279746573ULL ^ k1;
+
+	memset(ctx->buf, 0, sizeof(ctx->buf));
+	ctx->bytes = 0;
+}
+
+void
+SipHash_Update(SIPHASH_CTX *ctx, int rc, int rf, const void *src, size_t len)
+{
+	const uint8_t *ptr = src;
+	size_t left, used;
+
+	if (len == 0)
+		return;
+
+	used = ctx->bytes % sizeof(ctx->buf);
+	ctx->bytes += len;
+
+	if (used > 0) {
+		left = sizeof(ctx->buf) - used;
+
+		if (len >= left) {
+			memcpy(&ctx->buf[used], ptr, left);
+			SipHash_CRounds(ctx, rc);
+			len -= left;
+			ptr += left;
+		} else {
+			memcpy(&ctx->buf[used], ptr, len);
+			return;
+		}
+	}
+
+	while (len >= sizeof(ctx->buf)) {
+		memcpy(ctx->buf, ptr, sizeof(ctx->buf));
+		SipHash_CRounds(ctx, rc);
+		len -= sizeof(ctx->buf);
+		ptr += sizeof(ctx->buf);
+	}
+
+	if (len > 0)
+		memcpy(&ctx->buf, ptr, len);
+}
+
+uint64_t
+SipHash_End(SIPHASH_CTX *ctx, int rc, int rf)
+{
+	uint64_t r;
+	size_t left, used;
+
+	used = ctx->bytes % sizeof(ctx->buf);
+	left = sizeof(ctx->buf) - used;
+	memset(&ctx->buf[used], 0, left - 1);
+	ctx->buf[7] = ctx->bytes;
+
+	SipHash_CRounds(ctx, rc);
+	ctx->v[2] ^= 0xff;
+	SipHash_Rounds(ctx, rf);
+
+	r = (ctx->v[0] ^ ctx->v[1]) ^ (ctx->v[2] ^ ctx->v[3]);
+	memzero(ctx, sizeof(*ctx));
+	return htole64(r);
+}
+
+uint64_t
+SipHash(const SIPHASH_KEY *key, int rc, int rf, const void *src, size_t len)
+{
+	SIPHASH_CTX ctx;
+
+	SipHash_Init(&ctx, key);
+	SipHash_Update(&ctx, rc, rf, src, len);
+	return (SipHash_End(&ctx, rc, rf));
+}
+
+#define SIP_ROTL(x, b) ((x) << (b)) | ( (x) >> (64 - (b)))
+
+static void
+SipHash_Rounds(SIPHASH_CTX *ctx, int rounds)
+{
+	while (rounds--) {
+		ctx->v[0] += ctx->v[1];
+		ctx->v[2] += ctx->v[3];
+		ctx->v[1] = SIP_ROTL(ctx->v[1], 13);
+		ctx->v[3] = SIP_ROTL(ctx->v[3], 16);
+
+		ctx->v[1] ^= ctx->v[0];
+		ctx->v[3] ^= ctx->v[2];
+		ctx->v[0] = SIP_ROTL(ctx->v[0], 32);
+
+		ctx->v[2] += ctx->v[1];
+		ctx->v[0] += ctx->v[3];
+		ctx->v[1] = SIP_ROTL(ctx->v[1], 17);
+		ctx->v[3] = SIP_ROTL(ctx->v[3], 21);
+
+		ctx->v[1] ^= ctx->v[2];
+		ctx->v[3] ^= ctx->v[0];
+		ctx->v[2] = SIP_ROTL(ctx->v[2], 32);
+	}
+}
+
+static void
+SipHash_CRounds(SIPHASH_CTX *ctx, int rounds)
+{
+	uint64_t tmp;
+
+	memcpy(&tmp, ctx->buf, sizeof(tmp));
+	uint64_t m = le64toh(tmp);
+
+	ctx->v[3] ^= m;
+	SipHash_Rounds(ctx, rounds);
+	ctx->v[0] ^= m;
+}
diff --git a/src/contrib/openbsd/siphash.h b/src/contrib/openbsd/siphash.h
new file mode 100644
index 0000000..d551fe8
--- /dev/null
+++ b/src/contrib/openbsd/siphash.h
@@ -0,0 +1,83 @@
+/*-
+ * Copyright (c) 2013 Andre Oppermann <andre@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $OpenBSD: siphash.h,v 1.3 2015/02/20 11:51:03 tedu Exp $
+ */
+
+/*
+ * SipHash is a family of pseudorandom functions (a.k.a. keyed hash functions)
+ * optimized for speed on short messages returning a 64bit hash/digest value.
+ *
+ * The number of rounds is defined during the initialization:
+ *  SipHash24_Init() for the fast and resonable strong version
+ *  SipHash48_Init() for the strong version (half as fast)
+ *
+ * struct SIPHASH_CTX ctx;
+ * SipHash24_Init(&ctx);
+ * SipHash_SetKey(&ctx, "16bytes long key");
+ * SipHash_Update(&ctx, pointer_to_string, length_of_string);
+ * SipHash_End(&ctx);
+ */
+
+#ifndef _SIPHASH_H_
+#define _SIPHASH_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#define SIPHASH_BLOCK_LENGTH	 8
+#define SIPHASH_KEY_LENGTH	16
+#define SIPHASH_DIGEST_LENGTH	 8
+
+typedef struct _SIPHASH_CTX {
+	uint64_t	v[4];
+	uint8_t		buf[SIPHASH_BLOCK_LENGTH];
+	uint32_t	bytes;
+} SIPHASH_CTX;
+
+typedef struct {
+	uint64_t	k0;
+	uint64_t	k1;
+} SIPHASH_KEY;
+
+void		SipHash_Init(SIPHASH_CTX *, const SIPHASH_KEY *);
+void		SipHash_Update(SIPHASH_CTX *, int, int, const void *, size_t);
+uint64_t	SipHash_End(SIPHASH_CTX *, int, int);
+uint64_t	SipHash(const SIPHASH_KEY *, int, int, const void *, size_t);
+
+#define SipHash24_Init(_c, _k)		SipHash_Init((_c), (_k))
+#define SipHash24_Update(_c, _p, _l)	SipHash_Update((_c), 2, 4, (_p), (_l))
+#define SipHash24_End(_d)		SipHash_End((_d), 2, 4)
+#define SipHash24(_k, _p, _l)		SipHash((_k), 2, 4, (_p), (_l))
+
+#define SipHash48_Init(_c, _k)		SipHash_Init((_c), (_k))
+#define SipHash48_Update(_c, _p, _l)	SipHash_Update((_c), 4, 8, (_p), (_l))
+#define SipHash48_End(_d)		SipHash_End((_d), 4, 8)
+#define SipHash48(_k, _p, _l)		SipHash((_k), 4, 8, (_p), (_l))
+
+#endif /* _SIPHASH_H_ */
diff --git a/src/contrib/openbsd/strlcat.c b/src/contrib/openbsd/strlcat.c
new file mode 100644
index 0000000..1409062
--- /dev/null
+++ b/src/contrib/openbsd/strlcat.c
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <string.h>
+
+#include "contrib/openbsd/strlcat.h"
+
+size_t
+knot_strlcat(char *dst, const char *src, size_t siz)
+{
+	char *d = dst;
+	const char *s = src;
+	size_t n = siz;
+	size_t dlen;
+
+	/* Find the end of dst and adjust bytes left but don't go past end */
+	while (n-- != 0 && *d != '\0')
+		d++;
+	dlen = d - dst;
+	n = siz - dlen;
+
+	if (n == 0)
+		return(dlen + strlen(s));
+	while (*s != '\0') {
+		if (n != 1) {
+			*d++ = *s;
+			n--;
+		}
+		s++;
+	}
+	*d = '\0';
+
+	return(dlen + (s - src));	/* count does not include NUL */
+}
diff --git a/src/contrib/openbsd/strlcat.h b/src/contrib/openbsd/strlcat.h
new file mode 100644
index 0000000..7016069
--- /dev/null
+++ b/src/contrib/openbsd/strlcat.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#pragma once
+
+#ifndef HAVE_STRLCAT
+#define strlcat(dst, src, size) knot_strlcat(dst, src, size)
+#endif
+
+/*
+ * Appends src to string dst of size siz (unlike strncat, siz is the
+ * full size of dst, not space left).  At most siz-1 characters
+ * will be copied.  Always NUL terminates (unless siz <= strlen(dst)).
+ * Returns strlen(src) + MIN(siz, strlen(initial dst)).
+ * If retval >= siz, truncation occurred.
+ */
+size_t
+knot_strlcat(char *dst, const char *src, size_t siz);
diff --git a/src/contrib/openbsd/strlcpy.c b/src/contrib/openbsd/strlcpy.c
new file mode 100644
index 0000000..eafc0e4
--- /dev/null
+++ b/src/contrib/openbsd/strlcpy.c
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <string.h>
+
+#include "contrib/openbsd/strlcpy.h"
+
+size_t
+knot_strlcpy(char *dst, const char *src, size_t siz)
+{
+	char *d = dst;
+	const char *s = src;
+	size_t n = siz;
+
+	/* Copy as many bytes as will fit */
+	if (n != 0) {
+		while (--n != 0) {
+			if ((*d++ = *s++) == '\0')
+				break;
+		}
+	}
+
+	/* Not enough room in dst, add NUL and traverse rest of src */
+	if (n == 0) {
+		if (siz != 0)
+			*d = '\0';		/* NUL-terminate dst */
+		while (*s++)
+			;
+	}
+
+	return(s - src - 1);	/* count does not include NUL */
+}
diff --git a/src/contrib/openbsd/strlcpy.h b/src/contrib/openbsd/strlcpy.h
new file mode 100644
index 0000000..6421068
--- /dev/null
+++ b/src/contrib/openbsd/strlcpy.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#pragma once
+
+#ifndef HAVE_STRLCPY
+#define strlcpy(dst, src, size) knot_strlcpy(dst, src, size)
+#endif
+
+/*
+ * Copy src to string dst of size siz.  At most siz-1 characters
+ * will be copied.  Always NUL terminates (unless siz == 0).
+ * Returns strlen(src); if retval >= siz, truncation occurred.
+ */
+size_t
+knot_strlcpy(char *dst, const char *src, size_t siz);
diff --git a/src/contrib/qp-trie/trie.c b/src/contrib/qp-trie/trie.c
new file mode 100644
index 0000000..10f9919
--- /dev/null
+++ b/src/contrib/qp-trie/trie.c
@@ -0,0 +1,835 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+    The code originated from https://github.com/fanf2/qp/blob/master/qp.c
+    at revision 5f6d93753.
+ */
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "contrib/qp-trie/trie.h"
+#include "contrib/macros.h"
+#include "contrib/mempattern.h"
+#include "libknot/errcode.h"
+
+#if defined(__i386) || defined(__x86_64) || defined(_M_IX86) \
+	|| (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN) \
+		&& __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+
+	/*!
+	 * \brief Use a pointer alignment hack to save memory.
+	 *
+	 * When on, isbranch() relies on the fact that in leaf_t the first pointer
+	 * is aligned on multiple of 4 bytes and that the flags bitfield is
+	 * overlaid over the lowest two bits of that pointer.
+	 * Neither is really guaranteed by the C standards; the second part should
+	 * be OK with x86_64 ABI and most likely any other little-endian platform.
+	 * It would be possible to manipulate the right bits portably, but it would
+	 * complicate the code nontrivially. C++ doesn't even guarantee type-punning.
+	 * In debug mode we check this works OK when creating a new trie instance.
+	 */
+	#define FLAGS_HACK 1
+#else
+	#define FLAGS_HACK 0
+#endif
+
+typedef unsigned char byte;
+typedef unsigned int uint;
+typedef uint bitmap_t; /*! Bit-maps, using the range of 1<<0 to 1<<16 (inclusive). */
+
+typedef struct {
+	uint32_t len; // 32 bits are enough for key lengths; probably even 16 bits would be.
+	char chars[];
+} tkey_t;
+
+/*! \brief Leaf of trie. */
+typedef struct {
+	#if !FLAGS_HACK
+		byte flags;
+	#endif
+	tkey_t *key; /*!< The pointer must be aligned to 4-byte multiples! */
+	trie_val_t val;
+} leaf_t;
+
+/*! \brief A trie node is either leaf_t or branch_t. */
+typedef union node node_t;
+
+/*!
+ * \brief Branch node of trie.
+ *
+ * - The flags distinguish whether the node is a leaf_t (0), or a branch
+ *   testing the more-important nibble (1) or the less-important one (2).
+ * - It stores the index of the byte that the node tests.  The combined
+ *   value (index*4 + flags) increases in branch nodes as you go deeper
+ *   into the trie.  All the keys below a branch are identical up to the
+ *   nibble identified by the branch.  Indices have to be stored because
+ *   we skip any branch nodes that would have a single child.
+ *   (Consequently, the skipped parts of key have to be validated in a leaf.)
+ * - The bitmap indicates which subtries are present.  The present child nodes
+ *   are stored in the twigs array (with no holes between them).
+ * - To simplify storing keys that are prefixes of each other, the end-of-string
+ *   position is treated as another nibble value, ordered before all others.
+ *   That affects the bitmap and twigs fields.
+ *
+ * \note The branch nodes are never allocated individually, but they are
+ *   always part of either the root node or the twigs array of the parent.
+ */
+typedef struct {
+	#if FLAGS_HACK
+		uint32_t flags  : 2,
+		         bitmap : 17; /*!< The first bitmap bit is for end-of-string child. */
+	#else
+		byte flags;
+		uint32_t bitmap;
+	#endif
+	uint32_t index;
+	node_t *twigs;
+} branch_t;
+
+union node {
+	leaf_t leaf;
+	branch_t branch;
+};
+
+struct trie {
+	node_t root; // undefined when weight == 0, see empty_root()
+	size_t weight;
+	knot_mm_t mm;
+};
+
+/*! \brief Make the root node empty (debug-only). */
+static inline void empty_root(node_t *root) {
+#ifndef NDEBUG
+	*root = (node_t){ .branch = {
+		.flags = 3, // invalid value that fits
+		.bitmap = 0,
+		.index = -1,
+		.twigs = NULL
+	} };
+#endif
+}
+
+/*! \brief Check that unportable code works OK (debug-only). */
+static void assert_portability(void) {
+#if FLAGS_HACK
+	assert(((union node){ .leaf = {
+			.key = ((void *)NULL) + 1,
+			.val = NULL
+		} }).branch.flags == 1);
+#endif
+}
+
+/*! \brief Propagate error codes. */
+#define ERR_RETURN(x) \
+	do { \
+		int err_code_ = x; \
+		if (unlikely(err_code_ != KNOT_EOK)) \
+			return err_code_; \
+	} while (false)
+
+/*!
+ * \brief Count the number of set bits.
+ *
+ * \TODO This implementation may be relatively slow on some HW.
+ */
+static uint bitmap_weight(bitmap_t w)
+{
+	assert((w & ~((1 << 17) - 1)) == 0); // using the least-important 17 bits
+	return __builtin_popcount(w);
+}
+
+/*! \brief Test flags to determine type of this node. */
+static bool isbranch(const node_t *t)
+{
+	uint f = t->branch.flags;
+	assert(f <= 2);
+	return f != 0;
+}
+
+/*! \brief Make a bitmask for testing a branch bitmap. */
+static bitmap_t nibbit(byte k, uint flags)
+{
+	uint shift = (2 - flags) << 2;
+	uint nibble = (k >> shift) & 0xf;
+	return 1 << (nibble + 1/*because of prefix keys*/);
+}
+
+/*! \brief Extract a nibble from a key and turn it into a bitmask. */
+static bitmap_t twigbit(node_t *t, const char *key, uint32_t len)
+{
+	assert(isbranch(t));
+	uint i = t->branch.index;
+
+	if (i >= len)
+		return 1 << 0; // leaf position
+
+	return nibbit((byte)key[i], t->branch.flags);
+}
+
+/*! \brief Test if a branch node has a child indicated by a bitmask. */
+static bool hastwig(node_t *t, bitmap_t bit)
+{
+	assert(isbranch(t));
+	return t->branch.bitmap & bit;
+}
+
+/*! \brief Compute offset of an existing child in a branch node. */
+static uint twigoff(node_t *t, bitmap_t b)
+{
+	assert(isbranch(t));
+	return bitmap_weight(t->branch.bitmap & (b - 1));
+}
+
+/*! \brief Get pointer to a particular child of a branch node. */
+static node_t* twig(node_t *t, uint i)
+{
+	assert(isbranch(t));
+	return &t->branch.twigs[i];
+}
+
+/*!
+ * \brief For a branch nod, compute offset of a child and child count.
+ *
+ * Having this separate might be meaningful for performance optimization.
+ */
+#define TWIGOFFMAX(off, max, t, b) do {			\
+		off = twigoff(t, b);			\
+		max = bitmap_weight(t->branch.bitmap);	\
+	} while(0)
+
+/*! \brief Simple string comparator. */
+static int key_cmp(const char *k1, uint32_t k1_len, const char *k2, uint32_t k2_len)
+{
+	int ret = memcmp(k1, k2, MIN(k1_len, k2_len));
+	if (ret != 0) {
+		return ret;
+	}
+
+	/* Key string is equal, compare lengths. */
+	if (k1_len == k2_len) {
+		return 0;
+	} else if (k1_len < k2_len) {
+		return -1;
+	} else {
+		return 1;
+	}
+}
+
+trie_t* trie_create(knot_mm_t *mm)
+{
+	assert_portability();
+	trie_t *trie = mm_alloc(mm, sizeof(trie_t));
+	if (trie != NULL) {
+		empty_root(&trie->root);
+		trie->weight = 0;
+		if (mm != NULL)
+			trie->mm = *mm;
+		else
+			mm_ctx_init(&trie->mm);
+	}
+	return trie;
+}
+
+/*! \brief Free anything under the trie node, except for the passed pointer itself. */
+static void clear_trie(node_t *trie, knot_mm_t *mm)
+{
+	if (!isbranch(trie)) {
+		mm_free(mm, trie->leaf.key);
+	} else {
+		branch_t *b = &trie->branch;
+		int len = bitmap_weight(b->bitmap);
+		for (int i = 0; i < len; ++i)
+			clear_trie(b->twigs + i, mm);
+		mm_free(mm, b->twigs);
+	}
+}
+
+void trie_free(trie_t *tbl)
+{
+	if (tbl == NULL)
+		return;
+	if (tbl->weight)
+		clear_trie(&tbl->root, &tbl->mm);
+	mm_free(&tbl->mm, tbl);
+}
+
+void trie_clear(trie_t *tbl)
+{
+	assert(tbl);
+	if (!tbl->weight)
+		return;
+	clear_trie(&tbl->root, &tbl->mm);
+	empty_root(&tbl->root);
+	tbl->weight = 0;
+}
+
+size_t trie_weight(const trie_t *tbl)
+{
+	assert(tbl);
+	return tbl->weight;
+}
+
+trie_val_t* trie_get_try(trie_t *tbl, const char *key, uint32_t len)
+{
+	assert(tbl);
+	if (!tbl->weight)
+		return NULL;
+	node_t *t = &tbl->root;
+	while (isbranch(t)) {
+		__builtin_prefetch(t->branch.twigs);
+		bitmap_t b = twigbit(t, key, len);
+		if (!hastwig(t, b))
+			return NULL;
+		t = twig(t, twigoff(t, b));
+	}
+	if (key_cmp(key, len, t->leaf.key->chars, t->leaf.key->len) != 0)
+		return NULL;
+	return &t->leaf.val;
+}
+
+int trie_del(trie_t *tbl, const char *key, uint32_t len, trie_val_t *val)
+{
+	assert(tbl);
+	if (!tbl->weight)
+		return KNOT_ENOENT;
+	node_t *t = &tbl->root; // current and parent node
+	branch_t *p = NULL;
+	bitmap_t b = 0;
+	while (isbranch(t)) {
+		__builtin_prefetch(t->branch.twigs);
+		b = twigbit(t, key, len);
+		if (!hastwig(t, b))
+			return KNOT_ENOENT;
+		p = &t->branch;
+		t = twig(t, twigoff(t, b));
+	}
+	if (key_cmp(key, len, t->leaf.key->chars, t->leaf.key->len) != 0)
+		return KNOT_ENOENT;
+	mm_free(&tbl->mm, t->leaf.key);
+	if (val != NULL)
+		*val = t->leaf.val; // we return trie_val_t directly when deleting
+	--tbl->weight;
+	if (unlikely(!p)) { // whole trie was a single leaf
+		assert(tbl->weight == 0);
+		empty_root(&tbl->root);
+		return KNOT_EOK;
+	}
+	// remove leaf t as child of p
+	int ci = t - p->twigs, // child index via pointer arithmetic
+	    cc = bitmap_weight(p->bitmap); // child count
+	assert(ci >= 0 && ci < cc);
+
+	if (cc == 2) { // collapse binary node p: move the other child to this node
+		node_t *twigs = p->twigs;
+		(*(node_t *)p) = twigs[1 - ci]; // it might be a leaf or branch
+		mm_free(&tbl->mm, twigs);
+		return KNOT_EOK;
+	}
+	memmove(p->twigs + ci, p->twigs + ci + 1, sizeof(node_t) * (cc - ci - 1));
+	p->bitmap &= ~b;
+	node_t *twigs = mm_realloc(&tbl->mm, p->twigs, sizeof(node_t) * (cc - 1),
+	                           sizeof(node_t) * cc);
+	if (likely(twigs != NULL))
+		p->twigs = twigs;
+		/* We can ignore mm_realloc failure, only beware that next time
+		 * the prev_size passed to it wouldn't be correct; TODO? */
+	return KNOT_EOK;
+}
+
+/*!
+ * \brief Stack of nodes, storing a path down a trie.
+ *
+ * The structure also serves directly as the public trie_it_t type,
+ * in which case it always points to the current leaf, unless we've finished
+ * (i.e. it->len == 0).
+ */
+typedef struct trie_it {
+	node_t* *stack; /*!< The stack; malloc is used directly instead of mm. */
+	uint32_t len;   /*!< Current length of the stack. */
+	uint32_t alen;  /*!< Allocated/available length of the stack. */
+	/*! \brief Initial storage for \a stack; it should fit in most use cases. */
+	node_t* stack_init[2000 / sizeof(node_t *)];
+} nstack_t;
+
+/*! \brief Create a node stack containing just the root (or empty). */
+static void ns_init(nstack_t *ns, trie_t *tbl)
+{
+	assert(tbl);
+	ns->stack = ns->stack_init;
+	ns->alen = sizeof(ns->stack_init) / sizeof(ns->stack_init[0]);
+	if (tbl->weight) {
+		ns->len = 1;
+		ns->stack[0] = &tbl->root;
+	} else {
+		ns->len = 0;
+	}
+}
+
+/*! \brief Free inside of the stack, i.e. not the passed pointer itself. */
+static void ns_cleanup(nstack_t *ns)
+{
+	assert(ns && ns->stack);
+	if (likely(ns->stack == ns->stack_init))
+		return;
+	free(ns->stack);
+	#ifndef NDEBUG
+		ns->stack = NULL;
+		ns->alen = 0;
+	#endif
+}
+
+/*! \brief Allocate more space for the stack. */
+static int ns_longer_alloc(nstack_t *ns)
+{
+	ns->alen *= 2;
+	size_t new_size = sizeof(nstack_t) + ns->alen * sizeof(node_t *);
+	node_t **st;
+	if (ns->stack == ns->stack_init) {
+		st = malloc(new_size);
+		if (st != NULL)
+			memcpy(st, ns->stack, ns->len * sizeof(node_t *));
+	} else {
+		st = realloc(ns->stack, new_size);
+	}
+	if (st == NULL)
+		return KNOT_ENOMEM;
+	ns->stack = st;
+	return KNOT_EOK;
+}
+
+/*! \brief Ensure the node stack can be extended by one. */
+static inline int ns_longer(nstack_t *ns)
+{
+	// get a longer stack if needed
+	if (likely(ns->len < ns->alen))
+		return KNOT_EOK;
+	return ns_longer_alloc(ns); // hand-split the part suitable for inlining
+}
+
+/*!
+ * \brief Find the "branching point" as if searching for a key.
+ *
+ *  The whole path to the point is kept on the passed stack;
+ *  always at least the root will remain on the top of it.
+ *  Beware: the precise semantics of this function is rather tricky.
+ *  The top of the stack will contain: the corresponding leaf if exact match is found;
+ *  or the immediate node below a branching-point-on-edge or the branching-point itself.
+ *
+ *  \param info   Set position of the point of first mismatch (in index and flags).
+ *  \param first  Set the value of the first non-matching character (from trie),
+ *                optionally; end-of-string character has value -256 (that's why it's int).
+ *                Note: the character is converted to *unsigned* char (i.e. 0..255),
+ *                as that's the ordering used in the trie.
+ *
+ *  \return KNOT_EOK or KNOT_ENOMEM.
+ */
+static int ns_find_branch(nstack_t *ns, const char *key, uint32_t len,
+                          branch_t *info, int *first)
+{
+	assert(ns && ns->len && info);
+	// First find some leaf with longest matching prefix.
+	while (isbranch(ns->stack[ns->len - 1])) {
+		ERR_RETURN(ns_longer(ns));
+		node_t *t = ns->stack[ns->len - 1];
+		__builtin_prefetch(t->branch.twigs);
+		bitmap_t b = twigbit(t, key, len);
+		// Even if our key is missing from this branch we need to
+		// keep iterating down to a leaf. It doesn't matter which
+		// twig we choose since the keys are all the same up to this
+		// index. Note that blindly using twigoff(t, b) can cause
+		// an out-of-bounds index if it equals twigmax(t).
+		uint i = hastwig(t, b) ? twigoff(t, b) : 0;
+		ns->stack[ns->len++] = twig(t, i);
+	}
+	tkey_t *lkey = ns->stack[ns->len-1]->leaf.key;
+	// Find index of the first char that differs.
+	uint32_t index = 0;
+	while (index < MIN(len,lkey->len)) {
+		if (key[index] != lkey->chars[index])
+			break;
+		else
+			++index;
+	}
+	info->index = index;
+	if (first)
+		*first = lkey->len > index ? (unsigned char)lkey->chars[index] : -256;
+	// Find flags: which half-byte has matched.
+	uint flags;
+	if (index == len && len == lkey->len) { // found equivalent key
+		info->flags = flags = 0;
+		goto success;
+	}
+	if (likely(index < MIN(len,lkey->len))) {
+		byte k2 = (byte)lkey->chars[index];
+		byte k1 = (byte)key[index];
+		flags = ((k1 ^ k2) & 0xf0) ? 1 : 2;
+	} else { // one is prefix of another
+		flags = 1;
+	}
+	info->flags = flags;
+	// now go up the trie from the current leaf
+	branch_t *t;
+	do {
+		if (unlikely(ns->len == 1))
+			goto success; // only the root stays on the stack
+		t = (branch_t*)ns->stack[ns->len - 2];
+		if (t->index < index || (t->index == index && t->flags < flags))
+			goto success;
+		--ns->len;
+	} while (true);
+success:
+	#ifndef NDEBUG // invariants on successful return
+		assert(ns->len);
+		if (isbranch(ns->stack[ns->len - 1])) {
+			t = &ns->stack[ns->len - 1]->branch;
+			assert(t->index > index || (t->index == index && t->flags >= flags));
+		}
+		if (ns->len > 1) {
+			t = &ns->stack[ns->len - 2]->branch;
+			assert(t->index < index || (t->index == index
+			       && (t->flags < flags || (t->flags == 1 && flags == 0))));
+		}
+	#endif
+	return KNOT_EOK;
+}
+
+/*!
+ * \brief Advance the node stack to the last leaf in the subtree.
+ *
+ * \return KNOT_EOK or KNOT_ENOMEM.
+ */
+static int ns_last_leaf(nstack_t *ns)
+{
+	assert(ns);
+	do {
+		ERR_RETURN(ns_longer(ns));
+		node_t *t = ns->stack[ns->len - 1];
+		if (!isbranch(t))
+			return KNOT_EOK;
+		int lasti = bitmap_weight(t->branch.bitmap) - 1;
+		assert(lasti >= 0);
+		ns->stack[ns->len++] = twig(t, lasti);
+	} while (true);
+}
+
+/*!
+ * \brief Advance the node stack to the first leaf in the subtree.
+ *
+ * \return KNOT_EOK or KNOT_ENOMEM.
+ */
+static int ns_first_leaf(nstack_t *ns)
+{
+	assert(ns && ns->len);
+	do {
+		ERR_RETURN(ns_longer(ns));
+		node_t *t = ns->stack[ns->len - 1];
+		if (!isbranch(t))
+			return KNOT_EOK;
+		ns->stack[ns->len++] = twig(t, 0);
+	} while (true);
+}
+
+/*!
+ * \brief Advance the node stack to the leaf that is previous to the current node.
+ *
+ * \note Prefix leaf under the current node DOES count (if present; perhaps questionable).
+ * \return KNOT_EOK on success, KNOT_ENOENT on not-found, or possibly KNOT_ENOMEM.
+ */
+static int ns_prev_leaf(nstack_t *ns)
+{
+	assert(ns && ns->len > 0);
+
+	node_t *t = ns->stack[ns->len - 1];
+	if (hastwig(t, 1 << 0)) { // the prefix leaf
+		t = twig(t, 0);
+		ERR_RETURN(ns_longer(ns));
+		ns->stack[ns->len++] = t;
+		return KNOT_EOK;
+	}
+
+	do {
+		if (ns->len < 2)
+			return KNOT_ENOENT; // root without empty key has no previous leaf
+		t = ns->stack[ns->len - 1];
+		node_t *p = ns->stack[ns->len - 2];
+		int pindex = t - p->branch.twigs; // index in parent via pointer arithmetic
+		assert(pindex >= 0 && pindex <= 16);
+		if (pindex > 0) { // t isn't the first child -> go down the previous one
+			ns->stack[ns->len - 1] = twig(p, pindex - 1);
+			return ns_last_leaf(ns);
+		}
+		// we've got to go up again
+		--ns->len;
+	} while (true);
+}
+
+/*!
+ * \brief Advance the node stack to the leaf that is successor to the current node.
+ *
+ * \note Prefix leaf or anything else under the current node DOES count.
+ * \return KNOT_EOK on success, KNOT_ENOENT on not-found, or possibly KNOT_ENOMEM.
+ */
+static int ns_next_leaf(nstack_t *ns)
+{
+	assert(ns && ns->len > 0);
+
+	node_t *t = ns->stack[ns->len - 1];
+	if (isbranch(t))
+		return ns_first_leaf(ns);
+	do {
+		if (ns->len < 2)
+			return KNOT_ENOENT; // not found, as no more parent is available
+		t = ns->stack[ns->len - 1];
+		node_t *p = ns->stack[ns->len - 2];
+		int pindex = t - p->branch.twigs; // index in parent via pointer arithmetic
+		assert(pindex >= 0 && pindex <= 16);
+		int pcount = bitmap_weight(p->branch.bitmap);
+		if (pindex + 1 < pcount) { // t isn't the last child -> go down the next one
+			ns->stack[ns->len - 1] = twig(p, pindex + 1);
+			return ns_first_leaf(ns);
+		}
+		// we've got to go up again
+		--ns->len;
+	} while (true);
+}
+
+int trie_get_leq(trie_t *tbl, const char *key, uint32_t len, trie_val_t **val)
+{
+	assert(tbl && val);
+	*val = NULL; // so on failure we can just return;
+	if (tbl->weight == 0)
+		return KNOT_ENOENT;
+	{ // Intentionally un-indented; until end of function, to bound cleanup attr.
+	// First find a key with longest-matching prefix
+	__attribute__((cleanup(ns_cleanup)))
+		nstack_t ns_local;
+	ns_init(&ns_local, tbl);
+	nstack_t *ns = &ns_local;
+	branch_t bp;
+	int un_leaf; // first unmatched character in the leaf
+	ERR_RETURN(ns_find_branch(ns, key, len, &bp, &un_leaf));
+	int un_key = bp.index < len ? (unsigned char)key[bp.index] : -256;
+	node_t *t = ns->stack[ns->len - 1];
+	if (bp.flags == 0) { // found exact match
+		*val = &t->leaf.val;
+		return KNOT_EOK;
+	}
+	// Get t: the last node on matching path
+	if (isbranch(t) && t->branch.index == bp.index && t->branch.flags == bp.flags) {
+		// t is OK
+	} else {
+		// the top of the stack was the first unmatched node -> step up
+		if (ns->len == 1) {
+			// root was unmatched already
+			if (un_key < un_leaf)
+				return KNOT_ENOENT;
+			ERR_RETURN(ns_last_leaf(ns));
+			goto success;
+		}
+		--ns->len;
+		t = ns->stack[ns->len - 1];
+	}
+	// Now we re-do the first "non-matching" step in the trie
+	// but try the previous child if key was less (it may not exist)
+	bitmap_t b = twigbit(t, key, len);
+	int i = hastwig(t, b)
+		? twigoff(t, b) - (un_key < un_leaf)
+		: twigoff(t, b) - 1 /*twigoff returns successor when !hastwig*/;
+	if (i >= 0) {
+		ERR_RETURN(ns_longer(ns));
+		ns->stack[ns->len++] = twig(t, i);
+		ERR_RETURN(ns_last_leaf(ns));
+	} else {
+		ERR_RETURN(ns_prev_leaf(ns));
+	}
+success:
+	assert(!isbranch(ns->stack[ns->len - 1]));
+	*val = &ns->stack[ns->len - 1]->leaf.val;
+	return 1;
+	}
+}
+
+/*! \brief Initialize a new leaf, copying the key, and returning failure code. */
+static int mk_leaf(node_t *leaf, const char *key, uint32_t len, knot_mm_t *mm)
+{
+	tkey_t *k = mm_alloc(mm, sizeof(tkey_t) + len);
+	#if FLAGS_HACK
+		assert(((uintptr_t)k) % 4 == 0); // we need an aligned pointer
+	#endif
+	if (unlikely(!k))
+		return KNOT_ENOMEM;
+	k->len = len;
+	memcpy(k->chars, key, len);
+	leaf->leaf = (leaf_t){
+		#if !FLAGS_HACK
+			.flags = 0,
+		#endif
+		.val = NULL,
+		.key = k
+	};
+	return KNOT_EOK;
+}
+
+trie_val_t* trie_get_ins(trie_t *tbl, const char *key, uint32_t len)
+{
+	assert(tbl);
+	// First leaf in an empty tbl?
+	if (unlikely(!tbl->weight)) {
+		if (unlikely(mk_leaf(&tbl->root, key, len, &tbl->mm)))
+			return NULL;
+		++tbl->weight;
+		return &tbl->root.leaf.val;
+	}
+	{ // Intentionally un-indented; until end of function, to bound cleanup attr.
+	// Find the branching-point
+	__attribute__((cleanup(ns_cleanup)))
+		nstack_t ns_local;
+	ns_init(&ns_local, tbl);
+	nstack_t *ns = &ns_local;
+	branch_t bp; // branch-point: index and flags signifying the longest common prefix
+	int k2; // the first unmatched character in the leaf
+	if (unlikely(ns_find_branch(ns, key, len, &bp, &k2)))
+		return NULL;
+	node_t *t = ns->stack[ns->len - 1];
+	if (bp.flags == 0) // the same key was already present
+		return &t->leaf.val;
+	node_t leaf;
+	if (unlikely(mk_leaf(&leaf, key, len, &tbl->mm)))
+		return NULL;
+
+	if (isbranch(t) && bp.index == t->branch.index && bp.flags == t->branch.flags) {
+		// The node t needs a new leaf child.
+		bitmap_t b1 = twigbit(t, key, len);
+		assert(!hastwig(t, b1));
+		uint s, m; TWIGOFFMAX(s, m, t, b1); // new child position and original child count
+		node_t *twigs = mm_realloc(&tbl->mm, t->branch.twigs,
+				sizeof(node_t) * (m + 1), sizeof(node_t) * m);
+		if (unlikely(!twigs))
+			goto err_leaf;
+		memmove(twigs + s + 1, twigs + s, sizeof(node_t) * (m - s));
+		twigs[s] = leaf;
+		t->branch.twigs = twigs;
+		t->branch.bitmap |= b1;
+		++tbl->weight;
+		return &twigs[s].leaf.val;
+	} else {
+		// We need to insert a new binary branch with leaf at *t.
+		// Note: it works the same for the case where we insert above root t.
+		#ifndef NDEBUG
+			if (ns->len > 1) {
+				node_t *pt = ns->stack[ns->len - 2];
+				assert(hastwig(pt, twigbit(pt, key, len)));
+			}
+		#endif
+		node_t *twigs = mm_alloc(&tbl->mm, sizeof(node_t) * 2);
+		if (unlikely(!twigs))
+			goto err_leaf;
+		node_t t2 = *t; // Save before overwriting t.
+		t->branch.flags = bp.flags;
+		t->branch.index = bp.index;
+		t->branch.twigs = twigs;
+		bitmap_t b1 = twigbit(t, key, len);
+		bitmap_t b2 = unlikely(k2 == -256) ? (1 << 0) : nibbit(k2, bp.flags);
+		t->branch.bitmap = b1 | b2;
+		*twig(t, twigoff(t, b1)) = leaf;
+		*twig(t, twigoff(t, b2)) = t2;
+		++tbl->weight;
+		return &twig(t, twigoff(t, b1))->leaf.val;
+	};
+err_leaf:
+	mm_free(&tbl->mm, leaf.leaf.key);
+	return NULL;
+	}
+}
+
+/*! \brief Apply a function to every trie_val_t*, in order; a recursive solution. */
+static int apply_trie(node_t *t, int (*f)(trie_val_t *, void *), void *d)
+{
+	assert(t);
+	if (!isbranch(t))
+		return f(&t->leaf.val, d);
+	int child_count = bitmap_weight(t->branch.bitmap);
+	for (int i = 0; i < child_count; ++i)
+		ERR_RETURN(apply_trie(twig(t, i), f, d));
+	return KNOT_EOK;
+}
+
+int trie_apply(trie_t *tbl, int (*f)(trie_val_t *, void *), void *d)
+{
+	assert(tbl && f);
+	if (!tbl->weight)
+		return KNOT_EOK;
+	return apply_trie(&tbl->root, f, d);
+}
+
+/* These are all thin wrappers around static Tns* functions. */
+trie_it_t* trie_it_begin(trie_t *tbl)
+{
+	assert(tbl);
+	trie_it_t *it = malloc(sizeof(nstack_t));
+	if (!it)
+		return NULL;
+	ns_init(it, tbl);
+	if (it->len == 0) // empty tbl
+		return it;
+	if (ns_first_leaf(it)) {
+		ns_cleanup(it);
+		free(it);
+		return NULL;
+	}
+	return it;
+}
+
+void trie_it_next(trie_it_t *it)
+{
+	assert(it && it->len);
+	if (ns_next_leaf(it) != KNOT_EOK)
+		it->len = 0;
+}
+
+bool trie_it_finished(trie_it_t *it)
+{
+	assert(it);
+	return it->len == 0;
+}
+
+void trie_it_free(trie_it_t *it)
+{
+	if (!it)
+		return;
+	ns_cleanup(it);
+	free(it);
+}
+
+const char* trie_it_key(trie_it_t *it, size_t *len)
+{
+	assert(it && it->len);
+	node_t *t = it->stack[it->len - 1];
+	assert(!isbranch(t));
+	tkey_t *key = t->leaf.key;
+	if (len)
+		*len = key->len;
+	return key->chars;
+}
+
+trie_val_t* trie_it_val(trie_it_t *it)
+{
+	assert(it && it->len);
+	node_t *t = it->stack[it->len - 1];
+	assert(!isbranch(t));
+	return &t->leaf.val;
+}
diff --git a/src/contrib/qp-trie/trie.h b/src/contrib/qp-trie/trie.h
new file mode 100644
index 0000000..28ea571
--- /dev/null
+++ b/src/contrib/qp-trie/trie.h
@@ -0,0 +1,112 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "libknot/mm_ctx.h"
+
+/*!
+ * \brief Native API of QP-tries:
+ *
+ * - keys are char strings, not necessarily zero-terminated,
+ *   the structure copies the contents of the passed keys
+ * - values are void* pointers, typically you get an ephemeral pointer to it
+ * - key lengths are limited by 2^32-1 ATM
+ */
+
+/*! \brief Element value. */
+typedef void* trie_val_t;
+
+/*! \brief Opaque structure holding a QP-trie. */
+typedef struct trie trie_t;
+
+/*! \brief Opaque type for holding a QP-trie iterator. */
+typedef struct trie_it trie_it_t;
+
+/*! \brief Create a trie instance. */
+trie_t* trie_create(knot_mm_t *mm);
+
+/*! \brief Free a trie instance. */
+void trie_free(trie_t *tbl);
+
+/*! \brief Clear a trie instance (make it empty). */
+void trie_clear(trie_t *tbl);
+
+/*! \brief Return the number of keys in the trie. */
+size_t trie_weight(const trie_t *tbl);
+
+/*! \brief Search the trie, returning NULL on failure. */
+trie_val_t* trie_get_try(trie_t *tbl, const char *key, uint32_t len);
+
+/*! \brief Search the trie, inserting NULL trie_val_t on failure. */
+trie_val_t* trie_get_ins(trie_t *tbl, const char *key, uint32_t len);
+
+/*!
+ * \brief Search for less-or-equal element.
+ *
+ * \param tbl  Trie.
+ * \param key  Searched key.
+ * \param len  Key length.
+ * \param val  Must be valid; it will be set to NULL if not found or errored.
+ * \return KNOT_EOK for exact match, 1 for previous, KNOT_ENOENT for not-found,
+ *         or KNOT_E*.
+ */
+int trie_get_leq(trie_t *tbl, const char *key, uint32_t len, trie_val_t **val);
+
+/*!
+ * \brief Apply a function to every trie_val_t, in order.
+ *
+ * \return KNOT_EOK if success or KNOT_E* if error.
+ */
+int trie_apply(trie_t *tbl, int (*f)(trie_val_t *, void *), void *d);
+
+/*!
+ * \brief Remove an item, returning KNOT_EOK if succeeded or KNOT_ENOENT if not found.
+ *
+ * If val!=NULL and deletion succeeded, the deleted value is set.
+ */
+int trie_del(trie_t *tbl, const char *key, uint32_t len, trie_val_t *val);
+
+/*! \brief Create a new iterator pointing to the first element (if any). */
+trie_it_t* trie_it_begin(trie_t *tbl);
+
+/*!
+ * \brief Advance the iterator to the next element.
+ *
+ * Iteration is in ascending lexicographical order.
+ * In particular, the empty string would be considered as the very first.
+ */
+void trie_it_next(trie_it_t *it);
+
+/*! \brief Test if the iterator has gone past the last element. */
+bool trie_it_finished(trie_it_t *it);
+
+/*! \brief Free any resources of the iterator. It's OK to call it on NULL. */
+void trie_it_free(trie_it_t *it);
+
+/*!
+ * \brief Return pointer to the key of the current element.
+ *
+ * \note The len is uint32_t internally but size_t is better for our usage
+ *       as it is without an additional type conversion.
+ */
+const char* trie_it_key(trie_it_t *it, size_t *len);
+
+/*! \brief Return pointer to the value of the current element (writable). */
+trie_val_t* trie_it_val(trie_it_t *it);
diff --git a/src/contrib/sockaddr.c b/src/contrib/sockaddr.c
new file mode 100644
index 0000000..d569292
--- /dev/null
+++ b/src/contrib/sockaddr.c
@@ -0,0 +1,351 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <netdb.h>
+
+#include "libknot/consts.h"
+#include "libknot/errcode.h"
+#include "contrib/sockaddr.h"
+#include "contrib/openbsd/strlcpy.h"
+#include "contrib/macros.h"
+
+int sockaddr_len(const struct sockaddr *sa)
+{
+	if (sa == NULL) {
+		return 0;
+	}
+
+	switch(sa->sa_family) {
+	case AF_INET:
+		return sizeof(struct sockaddr_in);
+	case AF_INET6:
+		return sizeof(struct sockaddr_in6);
+	case AF_UNIX:
+		return sizeof(struct sockaddr_un);
+	default:
+		return 0;
+	}
+}
+
+static int cmp_ipv4(const struct sockaddr_in *a, const struct sockaddr_in *b)
+{
+	if (a->sin_addr.s_addr < b->sin_addr.s_addr) {
+		return -1;
+	} else if (a->sin_addr.s_addr > b->sin_addr.s_addr) {
+		return 1;
+	} else {
+		return a->sin_port - b->sin_port;
+	}
+}
+
+static int cmp_ipv6(const struct sockaddr_in6 *a, const struct sockaddr_in6 *b)
+{
+	int ret = memcmp(&a->sin6_addr, &b->sin6_addr, sizeof(struct in6_addr));
+	if (ret == 0) {
+		ret = a->sin6_port - b->sin6_port;
+	}
+
+	return ret;
+}
+
+static int cmp_unix(const struct sockaddr_un *a, const struct sockaddr_un *b)
+{
+	int len_a = strnlen(a->sun_path, sizeof(a->sun_path));
+	int len_b = strnlen(b->sun_path, sizeof(b->sun_path));
+	int len_min = len_a <= len_b ? len_a : len_b;
+
+	int ret = strncmp(a->sun_path, b->sun_path, len_min);
+	if (ret == 0) {
+		ret = len_a - len_b;
+	}
+
+	return ret;
+}
+
+int sockaddr_cmp(const struct sockaddr *a, const struct sockaddr *b)
+{
+	if (a->sa_family != b->sa_family) {
+		return (int)a->sa_family - (int)b->sa_family;
+	}
+
+	switch (a->sa_family) {
+	case AF_UNSPEC:
+		return 0;
+	case AF_INET:
+		return cmp_ipv4((struct sockaddr_in *)a, (struct sockaddr_in *)b);
+	case AF_INET6:
+		return cmp_ipv6((struct sockaddr_in6 *)a, (struct sockaddr_in6 *)b);
+	case AF_UNIX:
+		return cmp_unix((struct sockaddr_un *)a, (struct sockaddr_un *)b);
+	default:
+		return 1;
+	}
+}
+
+int sockaddr_set(struct sockaddr_storage *ss, int family, const char *straddr, int port)
+{
+	if (ss == NULL || straddr == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	/* Set family and port. */
+	memset(ss, 0, sizeof(*ss));
+	ss->ss_family = family;
+	sockaddr_port_set((struct sockaddr *)ss, port);
+
+	/* Initialize address depending on address family. */
+	if (family == AF_INET6) {
+		struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)ss;
+		if (inet_pton(family, straddr, &ipv6->sin6_addr) < 1) {
+			return KNOT_ERROR;
+		}
+		return KNOT_EOK;
+	} else if (family == AF_INET) {
+		struct sockaddr_in *ipv4 = (struct sockaddr_in *)ss;
+		if (inet_pton(family, straddr, &ipv4->sin_addr) < 1) {
+			return KNOT_ERROR;
+		}
+		return KNOT_EOK;
+	} else if (family == AF_UNIX) {
+		struct sockaddr_un *un = (struct sockaddr_un *)ss;
+		size_t ret = strlcpy(un->sun_path, straddr, sizeof(un->sun_path));
+		if (ret >= sizeof(un->sun_path)) {
+			return KNOT_ESPACE;
+		}
+		return KNOT_EOK;
+	}
+
+	return KNOT_EINVAL;
+}
+
+void *sockaddr_raw(const struct sockaddr *sa, size_t *addr_size)
+{
+	if (sa == NULL || addr_size == NULL) {
+		return NULL;
+	}
+
+	if (sa->sa_family == AF_INET) {
+		struct sockaddr_in *ipv4 = (struct sockaddr_in *)sa;
+		*addr_size = sizeof(ipv4->sin_addr);
+		return &ipv4->sin_addr;
+	} else if (sa->sa_family == AF_INET6) {
+		struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)sa;
+		*addr_size = sizeof(ipv6->sin6_addr);
+		return &ipv6->sin6_addr;
+	} else {
+		return NULL;
+	}
+}
+
+int sockaddr_set_raw(struct sockaddr_storage *ss, int family,
+                     const uint8_t *raw_addr, size_t raw_addr_size)
+{
+	if (ss == NULL || raw_addr == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	memset(ss, 0, sizeof(*ss));
+	ss->ss_family = family;
+
+	size_t sa_size = 0;
+	void *sa_data = sockaddr_raw((struct sockaddr *)ss, &sa_size);
+	if (sa_data == NULL || sa_size != raw_addr_size) {
+		return KNOT_EINVAL;
+	}
+
+	memcpy(sa_data, raw_addr, sa_size);
+
+	return KNOT_EOK;
+}
+
+int sockaddr_tostr(char *buf, size_t maxlen, const struct sockaddr *sa)
+{
+	if (sa == NULL || buf == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	const char *out = NULL;
+
+	/* Convert network address string. */
+	if (sa->sa_family == AF_INET6) {
+		const struct sockaddr_in6 *s = (const struct sockaddr_in6 *)sa;
+		out = inet_ntop(sa->sa_family, &s->sin6_addr, buf, maxlen);
+	} else if (sa->sa_family == AF_INET) {
+		const struct sockaddr_in *s = (const struct sockaddr_in *)sa;
+		out = inet_ntop(sa->sa_family, &s->sin_addr, buf, maxlen);
+	} else if (sa->sa_family == AF_UNIX) {
+		const struct sockaddr_un *s = (const struct sockaddr_un *)sa;
+		size_t ret = strlcpy(buf, s->sun_path, maxlen);
+		out = (ret < maxlen) ? buf : NULL;
+	} else {
+		return KNOT_EINVAL;
+	}
+
+	if (out == NULL) {
+		*buf = '\0';
+		return KNOT_ESPACE;
+	}
+
+	/* Write separator and port. */
+	int written = strlen(buf);
+	int port = sockaddr_port(sa);
+	if (port > 0) {
+		int ret = snprintf(&buf[written], maxlen - written, "@%d", port);
+		if (ret <= 0 || (size_t)ret >= maxlen - written) {
+			*buf = '\0';
+			return KNOT_ESPACE;
+		}
+
+		written += ret;
+	}
+
+	return written;
+}
+
+int sockaddr_port(const struct sockaddr *sa)
+{
+	if (sa == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	if (sa->sa_family == AF_INET6) {
+		return ntohs(((struct sockaddr_in6 *)sa)->sin6_port);
+	} else if (sa->sa_family == AF_INET) {
+		return ntohs(((struct sockaddr_in *)sa)->sin_port);
+	} else {
+		return KNOT_EINVAL;
+	}
+}
+
+void sockaddr_port_set(struct sockaddr *sa, uint16_t port)
+{
+	if (sa == NULL) {
+		return;
+	}
+
+	if (sa->sa_family == AF_INET6) {
+		((struct sockaddr_in6 *)sa)->sin6_port = htons(port);
+	} else if (sa->sa_family == AF_INET) {
+		((struct sockaddr_in *)sa)->sin_port = htons(port);
+	}
+}
+
+char *sockaddr_hostname(void)
+{
+	/* Fetch hostname. */
+	char host[KNOT_DNAME_MAXLEN + 1] = { '\0' };
+	if (gethostname(host, sizeof(host)) != 0) {
+		return NULL;
+	}
+	/* Just to be sure. */
+	host[sizeof(host) - 1] = '\0';
+
+	/* Fetch canonical name for this address/DNS. */
+	struct addrinfo hints, *info = NULL;
+	memset(&hints, 0, sizeof hints);
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = SOCK_DGRAM;
+	hints.ai_flags = AI_CANONNAME;
+	if (getaddrinfo(host, "domain", &hints, &info) != 0) {
+		return NULL;
+	}
+
+	/* Fetch first valid hostname. */
+	char *hname = NULL;
+	struct addrinfo *p = NULL;
+	for (p = info; p != NULL; p = p->ai_next) {
+		if (p->ai_canonname) {
+			hname = strdup(p->ai_canonname);
+			break;
+		}
+	}
+
+	/* No valid hostname found, resort to gethostname() result */
+	if (hname == NULL) {
+		hname = strdup(host);
+	}
+
+	freeaddrinfo(info);
+	return hname;
+}
+
+bool sockaddr_is_any(const struct sockaddr *sa)
+{
+	if (sa == NULL) {
+		return false;
+	}
+
+	if (sa->sa_family == AF_INET) {
+		const struct sockaddr_in *ipv4 = (struct sockaddr_in *)sa;
+		return ipv4->sin_addr.s_addr == INADDR_ANY;
+	}
+
+	if (sa->sa_family == AF_INET6) {
+		const struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)sa;
+		return memcmp(&ipv6->sin6_addr, &in6addr_any, sizeof(ipv6->sin6_addr)) == 0;
+	}
+
+	return false;
+}
+
+bool sockaddr_net_match(const struct sockaddr *ss1,
+                        const struct sockaddr *ss2,
+                        unsigned prefix)
+{
+	if (ss1 == NULL || ss2 == NULL) {
+		return false;
+	}
+
+	if (ss1->sa_family != ss2->sa_family) {
+		return false;
+	}
+
+	size_t raw_len = 0;
+	const uint8_t *raw_1 = sockaddr_raw(ss1, &raw_len);
+	const uint8_t *raw_2 = sockaddr_raw(ss2, &raw_len);
+
+	prefix = MIN(prefix, raw_len * 8);
+	unsigned bytes = prefix / 8;
+	unsigned bits = prefix % 8;
+
+	/* Compare full bytes. */
+	if (memcmp(raw_1, raw_2, bytes) != 0) {
+		return false;
+	}
+
+	/* Compare last partial byte. */
+	return bits == 0 ||
+	       (raw_1[bytes] >> (8 - bits) == raw_2[bytes] >> (8 - bits));
+}
+
+bool sockaddr_range_match(const struct sockaddr *sa,
+                          const struct sockaddr *ss_min,
+                          const struct sockaddr *ss_max)
+{
+	if (sa == NULL || ss_min == NULL || ss_max == NULL) {
+		return false;
+	}
+
+	if (ss_min->sa_family != ss_max->sa_family ||
+	    ss_min->sa_family != sa->sa_family) {
+		return false;
+	}
+
+	return sockaddr_cmp(sa, ss_min) >= 0 && sockaddr_cmp(sa, ss_max) <= 0;
+}
diff --git a/src/contrib/sockaddr.h b/src/contrib/sockaddr.h
new file mode 100644
index 0000000..0fbf1ab
--- /dev/null
+++ b/src/contrib/sockaddr.h
@@ -0,0 +1,160 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+/* BSD IPv6 */
+#ifndef __POSIX_VISIBLE
+#define __POSIX_VISIBLE 200112
+#endif
+
+#include <stdbool.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <stdint.h>
+#include <unistd.h>
+
+/* Subnet maximum prefix length. */
+#define IPV4_PREFIXLEN 32
+#define IPV6_PREFIXLEN 128
+
+/* Address string "address[@port]" maximum length. */
+#define SOCKADDR_STRLEN_EXT (1 + 6) /* '@', 5 digits number, \0 */
+#define SOCKADDR_STRLEN (sizeof(struct sockaddr_un) + SOCKADDR_STRLEN_EXT)
+
+/*!
+ * \brief Calculate current structure length based on address family.
+ *
+ * \param sa  Socket address.
+ *
+ * \return Number of bytes or error code.
+ */
+int sockaddr_len(const struct sockaddr *sa);
+
+/*!
+ * \brief Compare addresses.
+ *
+ * \return like memcmp(3)
+ */
+int sockaddr_cmp(const struct sockaddr *k1, const struct sockaddr *k2);
+
+/*!
+ * \brief Set address and port.
+ *
+ * \param ss       Socket address.
+ * \param family   Address family.
+ * \param straddr  IP address in string format.
+ * \param port     Port.
+ *
+ * \return KNOT_EOK on success or an error code.
+ */
+int sockaddr_set(struct sockaddr_storage *ss, int family, const char *straddr, int port);
+
+/*!
+ * \brief Return raw network address in network byte order.
+ *
+ * \param[in]  sa        Socket address.
+ * \param[out] addr_size Address length.
+ *
+ * \return Pointer to binary buffer of size addr_size.
+ */
+void *sockaddr_raw(const struct sockaddr *sa, size_t *addr_size);
+
+/*!
+ * \brief Set raw address.
+ *
+ * \param ss             Socket address.
+ * \param family         Address family.
+ * \param raw_addr       IP address in binary format.
+ * \param raw_addr_size  Size of the binary address.
+ *
+ * \return KNOT_EOK on success or an error code.
+ */
+int sockaddr_set_raw(struct sockaddr_storage *ss, int family,
+                     const uint8_t *raw_addr, size_t raw_addr_size);
+
+/*!
+ * \brief Return string representation of socket address.
+ *
+ * \note String format: \<address>[@<port>], f.e. '127.0.0.1@53'
+ *
+ * \param buf     Destination for string representation.
+ * \param maxlen  Maximum number of written bytes.
+ * \param sa      Socket address.
+ *
+ * \return Number of bytes written on success, error code on failure.
+ */
+int sockaddr_tostr(char *buf, size_t maxlen, const struct sockaddr *sa);
+
+/*!
+ * \brief Return port number from address.
+ *
+ * \param sa  Socket address.
+ *
+ * \return Port number or error code.
+ */
+int sockaddr_port(const struct sockaddr *sa);
+
+/*!
+ * \brief Set port number.
+ *
+ * \param sa    Socket address.
+ * \param port  Port to set.
+ */
+void sockaddr_port_set(struct sockaddr *sa, uint16_t port);
+
+/*!
+ * \brief Get host FQDN address.
+ *
+ * \return Hostname string or NULL.
+ */
+char *sockaddr_hostname(void);
+
+/*!
+ * \brief Check if address is ANY address.
+ *
+ * \param sa  Socket address.
+ */
+bool sockaddr_is_any(const struct sockaddr *sa);
+
+/*!
+ * \brief Check if two addresses match the given network prefix.
+ *
+ * \param sa1     First address.
+ * \param sa2     Second address.
+ * \param prefix  Prefix length.
+ *
+ * \return True on match.
+ */
+bool sockaddr_net_match(const struct sockaddr *sa1,
+                        const struct sockaddr *sa2,
+                        unsigned prefix);
+
+/*!
+ * \brief Check if the address is within the given address range (inclusive).
+ *
+ * \param sa      Address to check.
+ * \param sa_min  Minimum address.
+ * \param sa_max  Maximum address.
+ *
+ * \return True on match.
+ */
+bool sockaddr_range_match(const struct sockaddr *sa,
+                          const struct sockaddr *sa_min,
+                          const struct sockaddr *sa_max);
diff --git a/src/contrib/string.c b/src/contrib/string.c
new file mode 100644
index 0000000..6e0eea9
--- /dev/null
+++ b/src/contrib/string.c
@@ -0,0 +1,112 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "contrib/string.h"
+#include "contrib/ctype.h"
+
+uint8_t *memdup(const uint8_t *data, size_t data_size)
+{
+	uint8_t *result = (uint8_t *)malloc(data_size);
+	if (!result) {
+		return NULL;
+	}
+
+	return memcpy(result, data, data_size);
+}
+
+char *sprintf_alloc(const char *fmt, ...)
+{
+	char *strp = NULL;
+	va_list ap;
+
+	va_start(ap, fmt);
+	int ret = vasprintf(&strp, fmt, ap);
+	va_end(ap);
+
+	if (ret < 0) {
+		return NULL;
+	}
+	return strp;
+}
+
+char *strcdup(const char *s1, const char *s2)
+{
+	if (!s1 || !s2) {
+		return NULL;
+	}
+
+	size_t s1len = strlen(s1);
+	size_t s2len = strlen(s2);
+	size_t nlen = s1len + s2len + 1;
+
+	char* dst = malloc(nlen);
+	if (dst == NULL) {
+		return NULL;
+	}
+
+	memcpy(dst, s1, s1len);
+	memcpy(dst + s1len, s2, s2len + 1);
+	return dst;
+}
+
+char *strstrip(const char *str)
+{
+	// leading white-spaces
+	const char *scan = str;
+	while (is_space(scan[0])) {
+		scan += 1;
+	}
+
+	// trailing white-spaces
+	size_t len = strlen(scan);
+	while (len > 0 && is_space(scan[len - 1])) {
+		len -= 1;
+	}
+
+	char *trimmed = malloc(len + 1);
+	if (!trimmed) {
+		return NULL;
+	}
+
+	memcpy(trimmed, scan, len);
+	trimmed[len] = '\0';
+
+	return trimmed;
+}
+
+int const_time_memcmp(const void *s1, const void *s2, size_t n)
+{
+	volatile uint8_t equal = 0;
+
+	for (size_t i = 0; i < n; i++) {
+		equal |= ((uint8_t *)s1)[i] ^ ((uint8_t *)s2)[i];
+	}
+
+	return equal;
+}
+
+typedef void *(*memset_t)(void *, int, size_t);
+static volatile memset_t volatile_memset = memset;
+
+void *memzero(void *s, size_t n)
+{
+	return volatile_memset(s, 0, n);
+}
diff --git a/src/contrib/string.h b/src/contrib/string.h
new file mode 100644
index 0000000..19c74c7
--- /dev/null
+++ b/src/contrib/string.h
@@ -0,0 +1,82 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief String manipulations.
+ */
+
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+/*!
+ * \brief Create a copy of a binary buffer.
+ *
+ * Like \c strdup, but for binary data.
+ */
+uint8_t *memdup(const uint8_t *data, size_t data_size);
+
+/*!
+ * \brief Format string and take care of allocating memory.
+ *
+ * \note sprintf(3) manual page reference implementation.
+ *
+ * \param fmt Message format.
+ * \return formatted message or NULL.
+ */
+char *sprintf_alloc(const char *fmt, ...);
+
+/*!
+ * \brief Create new string from a concatenation of s1 and s2.
+ *
+ * \param s1 First string.
+ * \param s2 Second string.
+ *
+ * \retval Newly allocated string on success.
+ * \retval NULL on error.
+ */
+char *strcdup(const char *s1, const char *s2);
+
+/*!
+ * \brief Create a copy of a string skipping leading and trailing white spaces.
+ *
+ * \return Newly allocated string, NULL in case of error.
+ */
+char *strstrip(const char *str);
+
+/*!
+ * \brief Compare data in time based on string length.
+ *        This function just checks for (in)equality not for relation
+ *
+ * \param s1 The first address to compare.
+ * \param s2 The second address to compare.
+ * \param n The size of memory to compare.
+ *
+ * \return Non zero on difference and zero if the buffers are identical.
+ */
+int const_time_memcmp(const void *s1, const void *s2, size_t n);
+
+/*!
+ * \brief Fill memory with zeroes.
+ *
+ * Inspired by OPENSSL_cleanse. Such a memset shouldn't be optimized out.
+ *
+ * \param s The address to fill.
+ * \param n The size of memory to fill.
+ *
+ * \return Pointer to the memory.
+ */
+void *memzero(void *s, size_t n);
diff --git a/src/contrib/strtonum.h b/src/contrib/strtonum.h
new file mode 100644
index 0000000..6cfe8bb
--- /dev/null
+++ b/src/contrib/strtonum.h
@@ -0,0 +1,120 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include <assert.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "libknot/errcode.h"
+#include "contrib/ctype.h"
+
+inline static int intmax_from_str(const char *src, intmax_t *dst,
+                                  intmax_t min, intmax_t max)
+{
+	if (!is_digit(*src) && *src != '-' && *src != '+') {
+		return KNOT_EINVAL;
+	}
+
+	errno = 0;
+	char *end = NULL;
+	intmax_t result = strtoimax(src, &end, 10);
+
+	if (errno == ERANGE) {
+		return KNOT_ERANGE;
+	}
+
+	if (src == end || *end != '\0') {
+		return KNOT_EINVAL;
+	}
+
+	if (result < min || result > max) {
+		return KNOT_ERANGE;
+	}
+
+	*dst = result;
+	return KNOT_EOK;
+}
+
+inline static int uintmax_from_str(const char *src, uintmax_t *dst,
+                                   uintmax_t min, uintmax_t max)
+{
+	if (!is_digit(*src) && *src != '+') {
+		return KNOT_EINVAL;
+	}
+
+	errno = 0;
+	char *end = NULL;
+	uintmax_t result = strtoumax(src, &end, 10);
+
+	if (errno == ERANGE) {
+		return KNOT_ERANGE;
+	}
+
+	if (src == end || *end != '\0') {
+		return KNOT_EINVAL;
+	}
+
+	if (result < min || result > max) {
+		return KNOT_ERANGE;
+	}
+
+	*dst = result;
+	return KNOT_EOK;
+}
+
+#define CONVERT(prefix, type, min, max, src, dst)                 \
+{                                                                 \
+	assert(src && dst);                                       \
+	prefix##max_t value;                                      \
+	int result = prefix##max_from_str(src, &value, min, max); \
+	if (result != KNOT_EOK) {                                 \
+		return result;                                    \
+	}                                                         \
+	*dst = (type)value;                                       \
+	return KNOT_EOK;                                          \
+}
+
+inline static int str_to_int(const char *src, int *dst, int min, int max)
+{
+	CONVERT(int, int, min, max, src, dst);
+}
+
+inline static int str_to_u8(const char *src, uint8_t *dst)
+{
+	CONVERT(uint, uint8_t, 0, UINT8_MAX, src, dst);
+}
+
+inline static int str_to_u16(const char *src, uint16_t *dst)
+{
+	CONVERT(uint, uint16_t, 0, UINT16_MAX, src, dst);
+}
+
+inline static int str_to_u32(const char *src, uint32_t *dst)
+{
+	CONVERT(uint, uint32_t, 0, UINT32_MAX, src, dst);
+}
+
+inline static int str_to_size(const char *src, size_t *dst, size_t min, size_t max)
+{
+	CONVERT(uint, size_t, min, max, src, dst);
+}
+
+#undef CONVERT
diff --git a/src/contrib/time.c b/src/contrib/time.c
new file mode 100644
index 0000000..8c32c2d
--- /dev/null
+++ b/src/contrib/time.c
@@ -0,0 +1,405 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <assert.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "contrib/time.h"
+#include "contrib/ctype.h"
+#ifndef HAVE_CLOCK_GETTIME
+	#include <sys/time.h>
+#endif
+
+struct timespec time_now(void)
+{
+	struct timespec result = { 0 };
+
+#ifdef HAVE_CLOCK_GETTIME
+	clock_gettime(CLOCK_MONOTONIC, &result);
+#else // OS X < Sierra fallback.
+	struct timeval tmp = { 0 };
+	gettimeofday(&tmp, NULL);
+	result.tv_sec = tmp.tv_sec;
+	result.tv_nsec = 1000 * tmp.tv_usec;
+#endif
+
+	return result;
+}
+
+struct timespec time_diff(const struct timespec *begin, const struct timespec *end)
+{
+	struct timespec result = { 0 };
+
+	if (end->tv_nsec >= begin->tv_nsec) {
+		result.tv_sec  = end->tv_sec - begin->tv_sec;
+		result.tv_nsec = end->tv_nsec - begin->tv_nsec;
+	} else {
+		result.tv_sec  = end->tv_sec - begin->tv_sec - 1;
+		result.tv_nsec = 1000000000 - begin->tv_nsec + end->tv_nsec;
+	}
+
+	return result;
+}
+
+double time_diff_ms(const struct timespec *begin, const struct timespec *end)
+{
+	struct timespec result = time_diff(begin, end);
+
+	return (result.tv_sec * 1e3) + (result.tv_nsec / 1e6);
+}
+
+typedef struct {
+	const char *format;
+	const char *timespec;
+	const char *parsed;
+	knot_timediff_t offset;
+	char offset_sign;
+	char offset_unit;
+	struct tm calendar;
+	int error;
+} time_ctx_t;
+
+// After casting (struct tm) to (int []), we can use indexes...
+static int calendar_index(char ind)
+{
+	switch (ind) {
+	case 'Y': return 5;
+	case 'M': return 4;
+	case 'D': return 3;
+	case 'h': return 2;
+	case 'm': return 1;
+	case 's': return 0;
+	default: assert(0); return 6;
+	}
+}
+
+static size_t calendar_digits(int index)
+{
+	return index == 5 ? 4 : 2;
+}
+
+static size_t unit_value(char unit)
+{
+	size_t val = 1;
+	switch (unit) {
+	case 'M':
+		return 3600 * 24 * 30;
+	case 'Y':
+		val *= 365;
+		// FALLTHROUGH
+	case 'D':
+		val *= 24;
+		// FALLTHROUGH
+	case 'h':
+		val *= 60;
+		// FALLTHROUGH
+	case 'm':
+		val *= 60;
+		// FALLTHROUGH
+	case 's':
+	default:
+		return val;
+	}
+}
+
+static knot_time_t time_ctx_finalize(time_ctx_t *ctx)
+{
+	if (ctx->offset_sign) {
+		ctx->offset *= unit_value(ctx->offset_unit);
+		return knot_time_add(knot_time(), (ctx->offset_sign == '-' ? -1 : 1) * ctx->offset);
+	} else if (ctx->offset) {
+		return (knot_time_t)ctx->offset;
+	} else if (ctx->calendar.tm_year != 0) {
+		ctx->calendar.tm_isdst = -1;
+		ctx->calendar.tm_year -= 1900;
+		ctx->calendar.tm_mon -= 1;
+		// Set UTC timezone before using mktime
+		putenv("TZ=UTC");
+		tzset();
+		return (knot_time_t)mktime(&ctx->calendar);
+	} else {
+		return (knot_time_t)0;
+	}
+}
+
+static void time_ctx_reset(time_ctx_t *ctx)
+{
+	ctx->parsed = ctx->timespec;
+	ctx->offset = 0;
+	ctx->offset_sign = 0;
+	memset(&ctx->calendar, 0, sizeof(ctx->calendar));
+	ctx->error = 0;
+}
+
+static void parse_quote(time_ctx_t *ctx)
+{
+	while (*ctx->format != '|' && *ctx->format != '\0') {
+		if (*ctx->format == '\'') {
+			ctx->format++;
+			return;
+		}
+		if (*ctx->format++ != *ctx->parsed++) {
+			ctx->error = -1;
+			return;
+		}
+	}
+	ctx->error = -2;
+	return;
+}
+
+static void parse_offset(time_ctx_t *ctx)
+{
+	ctx->offset = 0;
+	ctx->error = -1;
+	while (is_digit(*ctx->parsed)) {
+		ctx->offset *= 10;
+		ctx->offset += *ctx->parsed++ - '0';
+		ctx->error = 0;
+	}
+}
+
+static void parse_calendar(time_ctx_t *ctx, int index)
+{
+	int *cal_arr = (int *)&ctx->calendar;
+	cal_arr[index] = 0;
+	for (size_t i = 0; i < calendar_digits(index); i++) {
+		if (!is_digit(*ctx->parsed)) {
+			ctx->error = -1;
+			return;
+		}
+		cal_arr[index] *= 10;
+		cal_arr[index] += *ctx->parsed++ - '0';
+	}
+}
+
+static void parse_sign(time_ctx_t *ctx)
+{
+	char sign1 = *(ctx->format - 1), sign2 = *ctx->format;
+
+	bool use_sign2 = (sign2 == '+' || sign2 == '-');
+
+	bool allow_plus = (sign1 == '+' || (sign1 == '-' && sign2 == '+'));
+	bool allow_minus = (sign1 == '-' || (sign1 == '+' && sign2 == '-'));
+	assert(sign1 == '+' || sign1 == '-');
+
+	if ((*ctx->parsed == '+' && allow_plus) || (*ctx->parsed == '-' && allow_minus)) {
+		ctx->offset_sign = *ctx->parsed++;
+		ctx->format += (use_sign2 ? 1 : 0);
+	} else {
+		ctx->error = -11;
+	}
+}
+
+static void parse_unit1(time_ctx_t *ctx)
+{
+	char u = *ctx->parsed++;
+	switch (u) {
+	case 'Y':
+	case 'M':
+	case 'D':
+	case 'h':
+	case 'm':
+	case 's':
+		ctx->offset_unit = u;
+		break;
+	default:
+		ctx->error = -1;
+	}
+}
+
+static void parse_unit2(time_ctx_t *ctx)
+{
+	char u = *ctx->parsed++;
+	switch (u) {
+	case 'y':
+	case 'd':
+		ctx->offset_unit = toupper((unsigned char)u);
+		break;
+	case 'h':
+	case 's':
+		ctx->offset_unit = u;
+		break;
+	case 'm':
+		switch (*ctx->parsed++) {
+		case 'o':
+			ctx->offset_unit = 'M';
+			break;
+		case 'i':
+			ctx->offset_unit = 'm';
+			break;
+		default:
+			ctx->error = -1;
+		}
+		break;
+	default:
+		ctx->error = -1;
+	}
+}
+
+int knot_time_parse(const char *format, const char *timespec, knot_time_t *time)
+{
+	if (format == NULL || timespec == NULL || time == NULL) {
+		return -1;
+	}
+
+	time_ctx_t ctx = {
+		.format = format,
+		.timespec = timespec,
+		.parsed = timespec,
+		.offset = 0,
+		.offset_sign = 0,
+		// we hope that .calendar is zeroed by default
+		.error = 0,
+	};
+
+	while (ctx.error == 0 && *ctx.format != '\0') {
+		switch (*ctx.format++) {
+		case '|':
+			if (*ctx.parsed == '\0') {
+				*time = time_ctx_finalize(&ctx);
+				return 0;
+			} else {
+				time_ctx_reset(&ctx);
+			}
+			break;
+		case '\'':
+			parse_quote(&ctx);
+			break;
+		case '#':
+			parse_offset(&ctx);
+			break;
+		case 'Y':
+		case 'M':
+		case 'D':
+		case 'h':
+		case 'm':
+		case 's':
+			parse_calendar(&ctx, calendar_index(*(ctx.format - 1)));
+			break;
+		case '+':
+		case '-':
+			parse_sign(&ctx);
+			break;
+		case 'U':
+			parse_unit1(&ctx);
+			break;
+		case 'u':
+			parse_unit2(&ctx);
+			break;
+		default:
+			return -1;
+		}
+
+		if (ctx.error < 0) {
+			while (*ctx.format != '|' && *ctx.format != '\0') {
+				ctx.format++;
+			}
+			time_ctx_reset(&ctx);
+			ctx.error = (*ctx.format == '\0' ? -1 : 0);
+		}
+	}
+
+	if (ctx.error == 0 && *ctx.parsed == '\0') {
+		*time = time_ctx_finalize(&ctx);
+		return 0;
+	}
+	return -1;
+}
+
+static char *unit_names_mixed[] = { "Y", "M", "D", "h", "m", "s" };
+static char *unit_names_lower[] = { "y", "mo", "d", "h", "mi", "s" };
+static size_t unit_sizes[] = { 3600*24*365, 3600*24*30, 3600*24, 3600, 60, 1 };
+static const size_t unit_count = 6;
+
+static int print_unit(char *dst, size_t dst_len, char *unit_names[unit_count],
+                      size_t max_units, knot_time_t time)
+{
+	int ret;
+	if (time == 0) {
+		ret = snprintf(dst, dst_len, "0");
+		return (ret < 0 || ret >= dst_len ? -1 : 0);
+	}
+	knot_timediff_t diff = knot_time_diff(time, knot_time());
+	if (dst_len-- < 1) {
+		return -1;
+	}
+	*dst++ = (diff < 0 ? '-' : '+');
+	if (diff < 0) {
+		diff = -diff;
+	} else if (diff == 0) {
+		ret = snprintf(dst, dst_len, "0%s", unit_names[unit_count - 1]);
+		return (ret < 0 || ret >= dst_len ? -1 : 0);
+	}
+	size_t curr_unit = 0, used_units = 0;
+	while (curr_unit < unit_count && used_units < max_units) {
+		if (diff >= unit_sizes[curr_unit]) {
+			ret = snprintf(dst, dst_len, "%"KNOT_TIMEDIFF_PRINTF"%s",
+			               diff / unit_sizes[curr_unit],
+			               unit_names[curr_unit]);
+			if (ret < 0 || ret >= dst_len) {
+				return -1;
+			}
+			dst += ret;
+			dst_len -= ret;
+			used_units++;
+			diff %= unit_sizes[curr_unit];
+		}
+		curr_unit++;
+	}
+	return 0;
+}
+
+int knot_time_print(knot_time_print_t format, knot_time_t time, char *dst, size_t dst_len)
+{
+	if (dst == NULL) {
+		return -1;
+	}
+
+	int ret;
+	switch (format) {
+	case TIME_PRINT_UNIX:
+		ret = snprintf(dst, dst_len, "%"KNOT_TIME_PRINTF, time);
+		return ((ret >= 0 && ret < dst_len) ? 0 : -1);
+	case TIME_PRINT_ISO8601:
+		if (time > LONG_MAX) {
+			return -1;
+		}
+
+		// Set timezone to UTC before using timezone dependent functions
+		putenv("TZ=UTC");
+		tzset();
+
+		struct tm lt;
+		time_t tt = (time_t)time;
+		ret = (localtime_r(&tt, &lt) == NULL ? -1 :
+		       strftime(dst, dst_len, "%Y-%m-%dT%H:%M:%SZ", &lt));
+		return (ret > 0 ? 0 : -1);
+	case TIME_PRINT_RELSEC:
+		ret = snprintf(dst, dst_len, "%+"KNOT_TIMEDIFF_PRINTF,
+		               knot_time_diff(time, knot_time()));
+		return ((ret >= 0 && ret < dst_len) ? 0 : -1);
+	case TIME_PRINT_HUMAN_MIXED:
+		return print_unit(dst, dst_len, unit_names_mixed, unit_count, time);
+	case TIME_PRINT_HUMAN_LOWER:
+		return print_unit(dst, dst_len, unit_names_lower, unit_count, time);
+	default:
+		return -1;
+	}
+}
diff --git a/src/contrib/time.h b/src/contrib/time.h
new file mode 100644
index 0000000..55b8727
--- /dev/null
+++ b/src/contrib/time.h
@@ -0,0 +1,171 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <time.h>
+#include <inttypes.h>
+
+/*!
+ * \brief Specify output format for knot_time_print().
+ */
+typedef enum {
+	TIME_PRINT_UNIX,	// numeric UNIX time
+	TIME_PRINT_ISO8601,	// 2016-12-31T23:59:00
+	TIME_PRINT_RELSEC,	// relative +6523
+	TIME_PRINT_HUMAN_MIXED,	// relative with mixed-case units
+	TIME_PRINT_HUMAN_LOWER,	// relative with lower-case units
+} knot_time_print_t;
+
+/*!
+ * \brief Get current time.
+ */
+struct timespec time_now(void);
+
+/*!
+ * \brief Get time elapsed between two events.
+ */
+struct timespec time_diff(const struct timespec *begin, const struct timespec *end);
+
+/*!
+ * \brief Get time elapsed between two events in miliseconds.
+ */
+double time_diff_ms(const struct timespec *begin, const struct timespec *end);
+
+/*!
+ * \brief Data type for keeping UNIX timestamps.
+ *
+ * This is because time_t can be 32-bit on some systems, which is bad.
+ * Zero value represents infinity.
+ */
+typedef uint64_t knot_time_t;
+
+/*!
+ * \brief Data type for keeping time differences.
+ */
+typedef int64_t knot_timediff_t;
+
+#define KNOT_TIMEDIFF_MIN INT64_MIN
+#define KNOT_TIMEDIFF_MAX INT64_MAX
+
+#define KNOT_TIME_PRINTF PRIu64
+#define KNOT_TIMEDIFF_PRINTF PRId64
+
+/*!
+ * \brief Returns current time sice epoch.
+ */
+inline static knot_time_t knot_time(void)
+{
+	return (knot_time_t)time(NULL);
+}
+
+/*!
+ * \brief Compare two timestamps.
+ *
+ * \return 0 if equal, -1 if the former is smaller (=earlier), 1 else.
+ */
+inline static int knot_time_cmp(knot_time_t a, knot_time_t b)
+{
+	return (a == b ? 0 : 1) * ((a && b) == 0 ? -1 : 1) * (a < b ? -1 : 1);
+}
+
+/*!
+ * \brief Return the smaller (=earlier) from given two timestamps.
+ */
+inline static knot_time_t knot_time_min(knot_time_t a, knot_time_t b)
+{
+	if ((a && b) == 0) {
+		return a + b;
+	} else {
+		return (a < b ? a : b);
+	}
+}
+
+/*!
+ * \brief Return the difference between two timestamps (to "minus" from).
+ *
+ * \note If both are zero (=infinity), KNOT_TIMEDIFF_MAX is returned.
+ */
+inline static knot_timediff_t knot_time_diff(knot_time_t to, knot_time_t from)
+{
+	if ((to && from) == 0) {
+		return (to > from ? KNOT_TIMEDIFF_MIN : KNOT_TIMEDIFF_MAX);
+	} else {
+		return (knot_timediff_t)to - (knot_timediff_t)from;
+	}
+}
+
+/*!
+ * \brief Add a time difference to timestamp.
+ */
+inline static knot_time_t knot_time_add(knot_time_t since, knot_timediff_t howlong)
+{
+	return (since != 0 ? since + howlong : since);
+}
+
+/*!
+ * \brief Convert uint32_t-encoded timestamp to knot_time_t.
+ *
+ * In RRSIG rdata, there are inception and expiration timestamps in uint32_t format.
+ * One shall use 'serial arithmetics' to decode them.
+ *
+ * \todo However it needs time(now) context which is slow to obtain, so we don't do it
+ *       for now. Please fix this in next 100 years.
+ */
+inline static knot_time_t knot_time_from_u32(uint32_t u32time)
+{
+	return (knot_time_t)u32time;
+}
+
+/*!
+ * \brief Parse a text-formatted timestamp to knot_time_t using format specification.
+ *
+ * \param format    The timestamp text format specification.
+ * \param timespec  Text-formatted timestamp.
+ * \param time      The parsed timestamp.
+ *
+ * The format specification basics:
+ * <format 1>|<format 2> - The pipe sign separates two time format specifications. Leftmost
+ *                         specification matching the timespec is used.
+ * '<a string>'          - Matches exactly <a string> (not containing apostrophes) in timespec.
+ * #                     - Hashtag matches for a number in timespec, stands for either a UNIX timestamp,
+ *                         or, within a context of an unit, as a number of such units.
+ * Y, M, D, h, m, s      - Matches a number, stands for a number of years, months, days, hours,
+ *                         minutes and seconds, respectively.
+ * +, -                  - The + and - signs declaring that following timespec is relative to "now".
+ *                         A single sign can be used to limit the timestamp being in future or in past,
+ *                         or both +- allow the timestamp to select any (just one) of them.
+ * U                     - Matches one of Y, M, D, h, m, s in the timespec standing for a time unit.
+ * u                     - Like U, but the unit in the timestamp is from: y, mo, d, h, mi, s.
+ *
+ * \retval -1  An error occurred, out_time has no sense.
+ * \return  0  OK, timestamp parsed successfully.
+ */
+int knot_time_parse(const char *format, const char *timespec, knot_time_t *time);
+
+/*!
+ * \brief Print the timestamp in specified format into a string buffer.
+ *
+ * \param format   The timestamp text format specification.
+ * \param time     The timestamp to be printed.
+ * \param dst      The destination buffer pointer with text-formatted timestamp.
+ * \param dst_len  The destination buffer length.
+ *
+ * \retval -1 An error occurred, the buffer may be filled with nonsense.
+ * \return  0 OK, timestamp printed successfully.
+ */
+int knot_time_print(knot_time_print_t format, knot_time_t time, char *dst, size_t dst_len);
diff --git a/src/contrib/tolower.h b/src/contrib/tolower.h
new file mode 100644
index 0000000..8f55182
--- /dev/null
+++ b/src/contrib/tolower.h
@@ -0,0 +1,51 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \brief Table for converting ASCII characters to lowercase.
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+/*!
+ * \brief Converts binary character to lowercase.
+ *
+ * \param c  Character code.
+ *
+ * \return \a c converted to lowercase (or \a c if not applicable).
+ */
+static inline uint8_t knot_tolower(uint8_t c) {
+	const uint8_t *tolower_table = (uint8_t *)
+	"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F"
+	"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F"
+	"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2A\x2B\x2C\x2D\x2E\x2F"
+	"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3A\x3B\x3C\x3D\x3E\x3F"
+	"\x40\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6A\x6B\x6C\x6D\x6E\x6F"
+	"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7A\x5B\x5C\x5D\x5E\x5F"
+	"\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6A\x6B\x6C\x6D\x6E\x6F"
+	"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7A\x7B\x7C\x7D\x7E\x7F"
+	"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8A\x8B\x8C\x8D\x8E\x8F"
+	"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9A\x9B\x9C\x9D\x9E\x9F"
+	"\xA0\xA1\xA2\xA3\xA4\xA5\xA6\xA7\xA8\xA9\xAA\xAB\xAC\xAD\xAE\xAF"
+	"\xB0\xB1\xB2\xB3\xB4\xB5\xB6\xB7\xB8\xB9\xBA\xBB\xBC\xBD\xBE\xBF"
+	"\xC0\xC1\xC2\xC3\xC4\xC5\xC6\xC7\xC8\xC9\xCA\xCB\xCC\xCD\xCE\xCF"
+	"\xD0\xD1\xD2\xD3\xD4\xD5\xD6\xD7\xD8\xD9\xDA\xDB\xDC\xDD\xDE\xDF"
+	"\xE0\xE1\xE2\xE3\xE4\xE5\xE6\xE7\xE8\xE9\xEA\xEB\xEC\xED\xEE\xEF"
+	"\xF0\xF1\xF2\xF3\xF4\xF5\xF6\xF7\xF8\xF9\xFA\xFB\xFC\xFD\xFE\xFF";
+
+	return tolower_table[c];
+}
diff --git a/src/contrib/trim.h b/src/contrib/trim.h
new file mode 100644
index 0000000..c1b83fa
--- /dev/null
+++ b/src/contrib/trim.h
@@ -0,0 +1,35 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/*!
+ * \brief Heap memory trimmer.
+ */
+
+#pragma once
+
+#ifdef HAVE_MALLOC_TRIM
+#include <malloc.h>
+#endif
+
+/*!
+ * \brief Trim excess heap memory.
+ */
+static inline void mem_trim(void)
+{
+#ifdef HAVE_MALLOC_TRIM
+	malloc_trim(0);
+#endif
+	return;
+}
diff --git a/src/contrib/ucw/LICENSE b/src/contrib/ucw/LICENSE
new file mode 100644
index 0000000..b463d57
--- /dev/null
+++ b/src/contrib/ucw/LICENSE
@@ -0,0 +1 @@
+../licenses/LGPL-2.0
\ No newline at end of file
diff --git a/src/contrib/ucw/array-sort.h b/src/contrib/ucw/array-sort.h
new file mode 100644
index 0000000..1ff1377
--- /dev/null
+++ b/src/contrib/ucw/array-sort.h
@@ -0,0 +1,195 @@
+/*
+ *	UCW Library -- Universal Simple Array Sorter
+ *
+ *	(c) 2003--2008 Martin Mares <mj@ucw.cz>
+ *
+ *	This software may be freely distributed and used according to the terms
+ *	of the GNU Lesser General Public License.
+ */
+
+#pragma once
+
+#include "contrib/macros.h"
+
+/*
+ *  This is not a normal header file, it's a generator of sorting
+ *  routines.  Each time you include it with parameters set in the
+ *  corresponding preprocessor macros, it generates an array sorter
+ *  with the parameters given.
+ *
+ *  You might wonder why the heck do we implement our own array sorter
+ *  instead of using qsort(). The primary reason is that qsort handles
+ *  only continuous arrays, but we need to sort array-like data structures
+ *  where the only way to access elements is by using an indexing macro.
+ *  Besides that, we are more than 2 times faster.
+ *
+ *  So much for advocacy, there are the parameters (those marked with [*]
+ *  are mandatory):
+ *
+ *  ASORT_PREFIX(x) [*]	add a name prefix (used on all global names
+ *			defined by the sorter)
+ *  ASORT_KEY_TYPE  [*]	data type of a single array entry key
+ *  ASORT_ELT(i)	returns the key of i-th element; if this macro is not
+ *			defined, the function gets a pointer to an array to be sorted
+ *  ASORT_LT(x,y)	x < y for ASORT_KEY_TYPE (default: "x<y")
+ *  ASORT_SWAP(i,j)	swap i-th and j-th element (default: assume _ELT
+ *			is an l-value and swap just the keys)
+ *  ASORT_THRESHOLD	threshold for switching between quicksort and insertsort
+ *  ASORT_EXTRA_ARGS	extra arguments for the sort function (they are always
+ *			visible in all the macros supplied above), starts with comma
+ *
+ *  After including this file, a function ASORT_PREFIX(sort)(unsigned array_size)
+ *  or ASORT_PREFIX(sort)(ASORT_KEY_TYPE *array, unsigned array_size) [if ASORT_ELT
+ *  is not defined] is declared and all parameter macros are automatically
+ *  undef'd.
+ */
+
+#ifndef ASORT_LT
+#define ASORT_LT(x,y) ((x) < (y))
+#endif
+
+#ifndef ASORT_SWAP
+#define ASORT_SWAP(i,j) do { ASORT_KEY_TYPE tmp = ASORT_ELT(i); ASORT_ELT(i)=ASORT_ELT(j); ASORT_ELT(j)=tmp; } while (0)
+#endif
+
+#ifndef ASORT_THRESHOLD
+#define ASORT_THRESHOLD 8		/* Guesswork and experimentation */
+#endif
+
+#ifndef ASORT_EXTRA_ARGS
+#define ASORT_EXTRA_ARGS
+#endif
+
+#ifndef ASORT_ELT
+#define ASORT_ARRAY_ARG ASORT_KEY_TYPE *array,
+#define ASORT_ELT(i) array[i]
+#else
+#define ASORT_ARRAY_ARG
+#endif
+
+/**
+ * The generated sorting function. If `ASORT_ELT` macro is not provided, the
+ * @ASORT_ARRAY_ARG is equal to `ASORT_KEY_TYPE *array` and is the array to be
+ * sorted. If the macro is provided, this parameter is omitted. In that case,
+ * you can sort global variables or pass your structure by @ASORT_EXTRA_ARGS.
+ **/
+static void ASORT_PREFIX(sort)(ASORT_ARRAY_ARG unsigned array_size ASORT_EXTRA_ARGS)
+{
+  struct stk { int l, r; } stack[8*sizeof(unsigned)];
+  int l, r, left, right, m;
+  unsigned sp = 0;
+  ASORT_KEY_TYPE pivot;
+
+  if (array_size <= 1)
+    return;
+
+  /* QuickSort with optimizations a'la Sedgewick, but stop at ASORT_THRESHOLD */
+
+  left = 0;
+  right = array_size - 1;
+  for(;;)
+    {
+      l = left;
+      r = right;
+      m = (l+r)/2;
+      if (ASORT_LT(ASORT_ELT(m), ASORT_ELT(l)))
+	ASORT_SWAP(l,m);
+      if (ASORT_LT(ASORT_ELT(r), ASORT_ELT(m)))
+	{
+	  ASORT_SWAP(m,r);
+	  if (ASORT_LT(ASORT_ELT(m), ASORT_ELT(l)))
+	    ASORT_SWAP(l,m);
+	}
+      pivot = ASORT_ELT(m);
+      do
+	{
+	  while (ASORT_LT(ASORT_ELT(l), pivot))
+	    l++;
+	  while (ASORT_LT(pivot, ASORT_ELT(r)))
+	    r--;
+	  if (l < r)
+	    {
+	      ASORT_SWAP(l,r);
+	      l++;
+	      r--;
+	    }
+	  else if (l == r)
+	    {
+	      l++;
+	      r--;
+	    }
+	}
+      while (l <= r);
+      if ((r - left) >= ASORT_THRESHOLD && (right - l) >= ASORT_THRESHOLD)
+	{
+	  /* Both partitions ok => push the larger one */
+	  if ((r - left) > (right - l))
+	    {
+	      stack[sp].l = left;
+	      stack[sp].r = r;
+	      left = l;
+	    }
+	  else
+	    {
+	      stack[sp].l = l;
+	      stack[sp].r = right;
+	      right = r;
+	    }
+	  sp++;
+	}
+      else if ((r - left) >= ASORT_THRESHOLD)
+	{
+	  /* Left partition OK, right undersize */
+	  right = r;
+	}
+      else if ((right - l) >= ASORT_THRESHOLD)
+	{
+	  /* Right partition OK, left undersize */
+	  left = l;
+	}
+      else
+	{
+	  /* Both partitions undersize => pop */
+	  if (!sp)
+	    break;
+	  sp--;
+	  left = stack[sp].l;
+	  right = stack[sp].r;
+	}
+    }
+
+  /*
+   * We have a partially sorted array, finish by insertsort. Inspired
+   * by qsort() in GNU libc.
+   */
+
+  /* Find minimal element which will serve as a barrier */
+  r = MIN(array_size, ASORT_THRESHOLD);
+  m = 0;
+  for (l=1; l<r; l++)
+    if (ASORT_LT(ASORT_ELT(l),ASORT_ELT(m)))
+      m = l;
+  ASORT_SWAP(0,m);
+
+  /* Insertion sort */
+  for (m=1; m<(int)array_size; m++)
+    {
+      l=m;
+      while (ASORT_LT(ASORT_ELT(m),ASORT_ELT(l-1)))
+	l--;
+      while (l < m)
+	{
+	  ASORT_SWAP(l,m);
+	  l++;
+	}
+    }
+}
+
+#undef ASORT_PREFIX
+#undef ASORT_KEY_TYPE
+#undef ASORT_ELT
+#undef ASORT_LT
+#undef ASORT_SWAP
+#undef ASORT_THRESHOLD
+#undef ASORT_EXTRA_ARGS
+#undef ASORT_ARRAY_ARG
diff --git a/src/contrib/ucw/binsearch.h b/src/contrib/ucw/binsearch.h
new file mode 100644
index 0000000..b791d39
--- /dev/null
+++ b/src/contrib/ucw/binsearch.h
@@ -0,0 +1,50 @@
+/*
+ *	UCW Library -- Generic Binary Search
+ *
+ *	(c) 2005 Martin Mares <mj@ucw.cz>
+ *
+ *	This software may be freely distributed and used according to the terms
+ *	of the GNU Lesser General Public License.
+ */
+
+#pragma once
+
+/***
+ * [[defs]]
+ * Definitions
+ * -----------
+ ***/
+
+/**
+ * Find the first element not lower than \p x in the sorted array \p ary of \p N elements (non-decreasing order).
+ * Returns the index of the found element or \p N if no exists. Uses `ary_lt_x(ary,i,x)` to compare the i'th element with \p x.
+ * The time complexity is `O(log(N))`.
+ **/
+#define BIN_SEARCH_FIRST_GE_CMP(ary, N, ary_lt_x, x, ...)  ({	\
+  unsigned l = 0, r = (N);						\
+  while (l < r)							\
+    {								\
+      unsigned m = (l+r)/2;						\
+      if (ary_lt_x(ary, m, x, __VA_ARGS__))			\
+        l = m+1;						\
+      else							\
+        r = m;							\
+    }								\
+  l;								\
+})
+
+/**
+ * The default comparison macro for \ref BIN_SEARCH_FIRST_GE_CMP().
+ **/
+#define ARY_LT_NUM(ary,i,x) (ary)[i] < (x)
+
+/**
+ * Same as \ref BIN_SEARCH_FIRST_GE_CMP(), but uses the default `<` operator for comparisons.
+ **/
+#define BIN_SEARCH_FIRST_GE(ary,N,x) BIN_SEARCH_FIRST_GE_CMP(ary,N,ARY_LT_NUM,x)
+
+/**
+ * Search the sorted array \p ary of \p N elements (non-decreasing) for the first occurrence of \p x.
+ * Returns the index or -1 if no such element exists. Uses the `<` operator for comparisons.
+ **/
+#define BIN_SEARCH_EQ(ary,N,x) ({ int i = BIN_SEARCH_FIRST_GE(ary,N,x); if (i >= (N) || (ary)[i] != (x)) i=-1; i; })
diff --git a/src/contrib/ucw/heap.c b/src/contrib/ucw/heap.c
new file mode 100644
index 0000000..d7ed18e
--- /dev/null
+++ b/src/contrib/ucw/heap.c
@@ -0,0 +1,166 @@
+/*
+ *	Binary heap
+ *
+ *	(c) 2012 Ondrej Filip <feela@network.cz>
+ *
+ *	This software may be freely distributed and used according to the terms
+ *	of the GNU Lesser General Public License.
+ */
+
+/***
+ * Introduction
+ * ------------
+ *
+ * Binary heap is a simple data structure, which for example supports efficient insertions, deletions
+ * and access to the minimal inserted item. We define several macros for such operations.
+ * Note that because of simplicity of heaps, we have decided to define direct macros instead
+ * of a <<generic:,macro generator>> as for several other data structures in the Libucw.
+ *
+ * A heap is represented by a number of elements and by an array of values. Beware that we
+ * index this array from one, not from zero as do the standard C arrays.
+ *
+ * Most macros use these parameters:
+ *
+ * - @num - a variable (signed or unsigned integer) with the number of elements
+ * - @heap - a C array of type @type; the heap is stored in `heap[1] .. heap[num]`; `heap[0]` is unused
+ *
+ * A valid heap must follow these rules:
+ *
+ * - `num >= 0`
+ * - `heap[i] >= heap[i / 2]` for each `i` in `[2, num]`
+ *
+ * The first element `heap[1]` is always lower or equal to all other elements.
+ ***/
+
+#include <string.h>
+#include <stdlib.h>
+#include "contrib/ucw/heap.h"
+
+static inline void heap_swap(heap_val_t **e1, heap_val_t **e2)
+{
+	if (e1 == e2) return; /* Stack tmp should be faster than tmpelem. */
+	heap_val_t *tmp = *e1; /* Even faster than 2-XOR nowadays. */
+	*e1 = *e2;
+	*e2 = tmp;
+	int pos = (*e1)->pos;
+	(*e1)->pos = (*e2)->pos;
+	(*e2)->pos = pos;
+}
+
+int heap_init(struct heap *h, int (*cmp)(void *, void *), int init_size)
+{
+	int isize = init_size ? init_size : INITIAL_HEAP_SIZE;
+
+	h->num = 0;
+	h->max_size = isize;
+	h->cmp = cmp;
+	h->data = malloc((isize + 1) * sizeof(heap_val_t*)); /* Temp element unused. */
+
+	return h->data ? 1 : 0;
+}
+
+void heap_deinit(struct heap *h)
+{
+	free(h->data);
+	memset(h, 0, sizeof(*h));
+}
+
+static inline void _heap_bubble_down(struct heap *h, int e)
+{
+	int e1;
+	for (;;)
+	{
+		e1 = 2*e;
+		if(e1 > h->num) break;
+		if((h->cmp(*HELEMENT(h, e),*HELEMENT(h,e1)) < 0) && (e1 == h->num || (h->cmp(*HELEMENT(h, e),*HELEMENT(h,e1+1)) < 0))) break;
+		if((e1 != h->num) && (h->cmp(*HELEMENT(h, e1+1), *HELEMENT(h,e1)) < 0)) e1++;
+		heap_swap(HELEMENT(h,e),HELEMENT(h,e1));
+		e = e1;
+	}
+}
+
+static inline void _heap_bubble_up(struct heap *h, int e)
+{
+	int e1;
+	while (e > 1)
+	{
+		e1 = e/2;
+		if(h->cmp(*HELEMENT(h, e1),*HELEMENT(h,e)) < 0) break;
+		heap_swap(HELEMENT(h,e),HELEMENT(h,e1));
+		e = e1;
+	}
+
+}
+
+static void heap_increase(struct heap *h, int pos, heap_val_t *e)
+{
+	*HELEMENT(h, pos) = e;
+	e->pos = pos;
+	_heap_bubble_down(h, pos);
+}
+
+static void heap_decrease(struct heap *h, int pos, heap_val_t *e)
+{
+	*HELEMENT(h, pos) = e;
+	e->pos = pos;
+	_heap_bubble_up(h, pos);
+}
+
+void heap_replace(struct heap *h, int pos, heap_val_t *e)
+{
+	if (h->cmp(*HELEMENT(h, pos),e) < 0) {
+		heap_increase(h, pos, e);
+	} else {
+		heap_decrease(h, pos, e);
+	}
+}
+
+void heap_delmin(struct heap *h)
+{
+	if(h->num == 0) return;
+	if(h->num > 1)
+	{
+		heap_swap(HHEAD(h),HELEMENT(h,h->num));
+	}
+	(*HELEMENT(h, h->num))->pos = 0;
+	--h->num;
+	_heap_bubble_down(h, 1);
+}
+
+int heap_insert(struct heap *h, heap_val_t *e)
+{
+	if(h->num == h->max_size)
+	{
+		h->max_size = h->max_size * HEAP_INCREASE_STEP;
+		h->data = realloc(h->data, (h->max_size + 1) * sizeof(heap_val_t*));
+		if (!h->data) {
+			return 0;
+		}
+	}
+
+	h->num++;
+	*HELEMENT(h,h->num) = e;
+	e->pos = h->num;
+	_heap_bubble_up(h,h->num);
+	return 1;
+}
+
+int heap_find(struct heap *h, heap_val_t *elm)
+{
+	return ((struct heap_val *) elm)->pos;
+}
+
+void heap_delete(struct heap *h, int e)
+{
+	heap_swap(HELEMENT(h, e), HELEMENT(h, h->num));
+	(*HELEMENT(h, h->num))->pos = 0;
+	h->num--;
+	if(h->cmp(*HELEMENT(h, e), *HELEMENT(h, h->num + 1)) < 0) _heap_bubble_up(h, e);
+	else _heap_bubble_down(h, e);
+
+	if ((h->num > INITIAL_HEAP_SIZE) && (h->num < h->max_size / HEAP_DECREASE_THRESHOLD))
+	{
+		h->max_size = h->max_size / HEAP_INCREASE_STEP;
+		h->data = realloc(h->data, (h->max_size + 1) * sizeof(heap_val_t*));
+	}
+}
diff --git a/src/contrib/ucw/heap.h b/src/contrib/ucw/heap.h
new file mode 100644
index 0000000..7419b34
--- /dev/null
+++ b/src/contrib/ucw/heap.h
@@ -0,0 +1,46 @@
+/*  Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+struct heap_val {
+	int pos;
+};
+
+typedef struct heap_val heap_val_t;
+
+struct heap {
+   int num;		/* Number of elements */
+   int max_size;	/* Size of allocated memory */
+   int (*cmp)(void *, void *);
+   heap_val_t **data;
+};		/* Array follows */
+
+#define INITIAL_HEAP_SIZE	512 /* initial heap size */
+#define HEAP_INCREASE_STEP	2 /* multiplier for each inflation, keep conservative */
+#define HEAP_DECREASE_THRESHOLD	2 /* threshold for deflation, keep conservative */
+#define HELEMENT(h,num) 	((h)->data + (num))
+#define HHEAD(h) 		HELEMENT((h), 1)
+#define EMPTY_HEAP(h) 		((h)->num == 0) /* h->num == 0 */
+
+int heap_init(struct heap *, int (*cmp)(void *, void *), int);
+void heap_deinit(struct heap *);
+
+void heap_delmin(struct heap *);
+int heap_insert(struct heap *, heap_val_t *);
+int heap_find(struct heap *, heap_val_t *);
+void heap_delete(struct heap *, int);
+void heap_replace(struct heap *h, int pos, heap_val_t *);
diff --git a/src/contrib/ucw/lists.c b/src/contrib/ucw/lists.c
new file mode 100644
index 0000000..8a9fa96
--- /dev/null
+++ b/src/contrib/ucw/lists.c
@@ -0,0 +1,235 @@
+/*
+ *	BIRD Library -- Linked Lists
+ *
+ *	(c) 1998 Martin Mares <mj@ucw.cz>
+ *	(c) 2015, 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+/**
+ * DOC: Linked lists
+ *
+ * The BIRD library provides a set of functions for operating on linked
+ * lists. The lists are internally represented as standard doubly linked
+ * lists with synthetic head and tail which makes all the basic operations
+ * run in constant time and contain no extra end-of-list checks. Each list
+ * is described by a &list structure, nodes can have any format as long
+ * as they start with a &node structure. If you want your nodes to belong
+ * to multiple lists at once, you can embed multiple &node structures in them
+ * and use the SKIP_BACK() macro to calculate a pointer to the start of the
+ * structure from a &node pointer, but beware of obscurity.
+ *
+ * There also exist safe linked lists (&slist, &snode and all functions
+ * being prefixed with |s_|) which support asynchronous walking very
+ * similar to that used in the &fib structure.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include "contrib/ucw/lists.h"
+#include "contrib/mempattern.h"
+
+/**
+ * add_tail - append a node to a list
+ * \p l: linked list
+ * \p n: list node
+ *
+ * add_tail() takes a node \p n and appends it at the end of the list \p l.
+ */
+void
+add_tail(list_t *l, node_t *n)
+{
+  node_t *z = l->tail;
+
+  n->next = (node_t *) &l->null;
+  n->prev = z;
+  z->next = n;
+  l->tail = n;
+}
+
+/**
+ * add_head - prepend a node to a list
+ * \p l: linked list
+ * \p n: list node
+ *
+ * add_head() takes a node \p n and prepends it at the start of the list \p l.
+ */
+void
+add_head(list_t *l, node_t *n)
+{
+  node_t *z = l->head;
+
+  n->next = z;
+  n->prev = (node_t *) &l->head;
+  z->prev = n;
+  l->head = n;
+}
+
+/**
+ * insert_node - insert a node to a list
+ * \p n: a new list node
+ * \p after: a node of a list
+ *
+ * Inserts a node \p n to a linked list after an already inserted
+ * node \p after.
+ */
+void
+insert_node(node_t *n, node_t *after)
+{
+  node_t *z = after->next;
+
+  n->next = z;
+  n->prev = after;
+  after->next = n;
+  z->prev = n;
+}
+
+/**
+ * rem_node - remove a node from a list
+ * \p n: node to be removed
+ *
+ * Removes a node \p n from the list it's linked in.
+ */
+void
+rem_node(node_t *n)
+{
+  node_t *z = n->prev;
+  node_t *x = n->next;
+
+  z->next = x;
+  x->prev = z;
+  n->prev = 0;
+  n->next = 0;
+}
+
+/**
+ * init_list - create an empty list
+ * \p l: list
+ *
+ * init_list() takes a &list structure and initializes its
+ * fields, so that it represents an empty list.
+ */
+void
+init_list(list_t *l)
+{
+  l->head = (node_t *) &l->null;
+  l->null = NULL;
+  l->tail = (node_t *) &l->head;
+}
+
+/**
+ * add_tail_list - concatenate two lists
+ * \p to: destination list
+ * \p l: source list
+ *
+ * This function appends all elements of the list \p l to
+ * the list \p to in constant time.
+ */
+void
+add_tail_list(list_t *to, list_t *l)
+{
+  node_t *p = to->tail;
+  node_t *q = l->head;
+
+  p->next = q;
+  q->prev = p;
+  q = l->tail;
+  q->next = (node_t *) &to->null;
+  to->tail = q;
+}
+
+/**
+ * list_dup - duplicate list
+ * \p to: destination list
+ * \p l: source list
+ *
+ * This function duplicates all elements of the list \p l to
+ * the list \p to in linear time.
+ *
+ * This function only works with a homogenous item size.
+ */
+void list_dup(list_t *dst, list_t *src, size_t itemsz)
+{
+	node_t *n = 0;
+	WALK_LIST(n, *src) {
+		node_t *i = malloc(itemsz);
+		memcpy(i, n, itemsz);
+		add_tail(dst, i);
+	}
+}
+
+/**
+ * list_size - gets number of nodes
+ * \p l: list
+ *
+ * This function counts nodes in list \p l and returns this number.
+ */
+size_t list_size(const list_t *l)
+{
+	size_t count = 0;
+
+	node_t *n = 0;
+	WALK_LIST(n, *l) {
+		count++;
+	}
+
+	return count;
+}
+
+/**
+ * ptrlist_add - add pointer to pointer list
+ * \p to: destination list
+ * \p val: added pointer
+ * \p mm: memory context
+ */
+ptrnode_t *ptrlist_add(list_t *to, void *val, knot_mm_t *mm)
+{
+	ptrnode_t *node = mm_alloc(mm , sizeof(ptrnode_t));
+	if (node == NULL) {
+		return NULL;
+	} else {
+		node->d = val;
+	}
+	add_tail(to, &node->n);
+	return node;
+}
+
+/**
+ * ptrlist_free - free all nodes in pointer list
+ * \p list: list nodes
+ * \p mm: memory context
+ */
+void ptrlist_free(list_t *list, knot_mm_t *mm)
+{
+	node_t *n = NULL, *nxt = NULL;
+	WALK_LIST_DELSAFE(n, nxt, *list) {
+		mm_free(mm, n);
+	}
+	init_list(list);
+}
+
+/**
+ * ptrlist_rem - remove pointer node
+ * \p val: pointer to remove
+ * \p mm: memory context
+ */
+void ptrlist_rem(ptrnode_t *node, knot_mm_t *mm)
+{
+	rem_node(&node->n);
+	mm_free(mm, node);
+}
+
+/**
+ * ptrlist_deep_free - free all nodes incl referenced data
+ * \p list: list nodes
+ * \p mm: memory context
+ */
+void ptrlist_deep_free(list_t *l, knot_mm_t *mm)
+{
+	ptrnode_t *n;
+	WALK_LIST(n, *l) {
+		mm_free(mm, n->d);
+	}
+	ptrlist_free(l, mm);
+}
diff --git a/src/contrib/ucw/lists.h b/src/contrib/ucw/lists.h
new file mode 100644
index 0000000..922e152
--- /dev/null
+++ b/src/contrib/ucw/lists.h
@@ -0,0 +1,84 @@
+/*
+ *	BIRD Library -- Linked Lists
+ *
+ *	(c) 1998 Martin Mares <mj@ucw.cz>
+ *	(c) 2015, 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+#pragma once
+
+/*
+ * I admit the list structure is very tricky and also somewhat awkward,
+ * but it's both efficient and easy to manipulate once one understands the
+ * basic trick: The list head always contains two synthetic nodes which are
+ * always present in the list: the head and the tail. But as the `next'
+ * entry of the tail and the `prev' entry of the head are both NULL, the
+ * nodes can overlap each other:
+ *
+ *     head    head_node.next
+ *     null    head_node.prev  tail_node.next
+ *     tail                    tail_node.prev
+ */
+
+#include <string.h>
+#include "libknot/mm_ctx.h"
+
+typedef struct node {
+  struct node *next, *prev;
+} node_t;
+
+typedef struct list {			/* In fact two overlayed nodes */
+  struct node *head, *null, *tail;
+} list_t;
+
+#define NODE (node_t *)
+#define HEAD(list) ((void *)((list).head))
+#define TAIL(list) ((void *)((list).tail))
+#define WALK_LIST(n,list) for(n=HEAD(list);(NODE (n))->next; \
+				n=(void *)((NODE (n))->next))
+#define WALK_LIST_DELSAFE(n,nxt,list) \
+     for(n=HEAD(list); (nxt=(void *)((NODE (n))->next)); n=(void *) nxt)
+/* WALK_LIST_FIRST supposes that called code removes each processed node */
+#define WALK_LIST_FIRST(n,list) \
+     while(n=HEAD(list), (NODE (n))->next)
+#define WALK_LIST_BACKWARDS(n,list) for(n=TAIL(list);(NODE (n))->prev; \
+				n=(void *)((NODE (n))->prev))
+#define WALK_LIST_BACKWARDS_DELSAFE(n,prv,list) \
+     for(n=TAIL(list); prv=(void *)((NODE (n))->prev); n=(void *) prv)
+
+#define EMPTY_LIST(list) (!(list).head->next)
+
+/*! \brief Free every node in the list. */
+#define WALK_LIST_FREE(list) \
+	do { \
+	node_t *n=0,*nxt=0;  \
+	WALK_LIST_DELSAFE(n,nxt,list) { \
+	    free(n); \
+	} \
+	init_list(&list); \
+	} while(0)
+
+void add_tail(list_t *, node_t *);
+void add_head(list_t *, node_t *);
+void rem_node(node_t *);
+void add_tail_list(list_t *, list_t *);
+void init_list(list_t *);
+void insert_node(node_t *, node_t *);
+void list_dup(list_t *dst, list_t *src, size_t itemsz);
+size_t list_size(const list_t *);
+
+/*!
+ * \brief Generic pointer list implementation.
+ */
+typedef struct ptrnode {
+	node_t n;
+	void *d;
+} ptrnode_t;
+
+ptrnode_t *ptrlist_add(list_t *, void *, knot_mm_t *);
+void ptrlist_free(list_t *, knot_mm_t *);
+void ptrlist_rem(ptrnode_t *node, knot_mm_t *mm);
+void ptrlist_deep_free(list_t *, knot_mm_t *);
+
diff --git a/src/contrib/ucw/mempool.c b/src/contrib/ucw/mempool.c
new file mode 100644
index 0000000..bc41345
--- /dev/null
+++ b/src/contrib/ucw/mempool.c
@@ -0,0 +1,322 @@
+/*
+ *	UCW Library -- Memory Pools (One-Time Allocation)
+ *
+ *	(c) 1997--2001 Martin Mares <mj@ucw.cz>
+ *	(c) 2007 Pavel Charvat <pchar@ucw.cz>
+ *	(c) 2015, 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+ *
+ *	This software may be freely distributed and used according to the terms
+ *	of the GNU Lesser General Public License.
+ */
+
+#undef LOCAL_DEBUG
+
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <assert.h>
+#include "contrib/asan.h"
+#include "contrib/macros.h"
+#include "contrib/ucw/mempool.h"
+
+/** \todo This shouldn't be precalculated, but computed on load. */
+#define CPU_PAGE_SIZE 4096
+
+/** Align an integer \p s to the nearest higher multiple of \p a (which should be a power of two) **/
+#define ALIGN_TO(s, a) (((s)+a-1)&~(a-1))
+#define MP_CHUNK_TAIL ALIGN_TO(sizeof(struct mempool_chunk), CPU_STRUCT_ALIGN)
+#define MP_SIZE_MAX (~0U - MP_CHUNK_TAIL - CPU_PAGE_SIZE)
+#define DBG(s, ...)
+
+/** \note Imported MMAP backend from bigalloc.c */
+#define CONFIG_UCW_POOL_IS_MMAP
+#ifdef CONFIG_UCW_POOL_IS_MMAP
+#include <sys/mman.h>
+static void *
+page_alloc(uint64_t len)
+{
+	if (!len) {
+		return NULL;
+	}
+	if (len > SIZE_MAX) {
+		return NULL;
+	}
+	assert(!(len & (CPU_PAGE_SIZE-1)));
+	uint8_t *p = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+	if (p == (uint8_t*) MAP_FAILED) {
+		return NULL;
+	}
+	return p;
+}
+
+static void
+page_free(void *start, uint64_t len)
+{
+	assert(!(len & (CPU_PAGE_SIZE-1)));
+	assert(!((uintptr_t) start & (CPU_PAGE_SIZE-1)));
+	munmap(start, len);
+}
+#endif
+
+struct mempool_chunk {
+	struct mempool_chunk *next;
+	unsigned size;
+};
+
+static unsigned
+mp_align_size(unsigned size)
+{
+#ifdef CONFIG_UCW_POOL_IS_MMAP
+	return ALIGN_TO(size + MP_CHUNK_TAIL, CPU_PAGE_SIZE) - MP_CHUNK_TAIL;
+#else
+	return ALIGN_TO(size, CPU_STRUCT_ALIGN);
+#endif
+}
+
+void
+mp_init(struct mempool *pool, unsigned chunk_size)
+{
+	chunk_size = mp_align_size(MAX(sizeof(struct mempool), chunk_size));
+	*pool = (struct mempool) {
+		.chunk_size = chunk_size,
+		.threshold = chunk_size >> 1,
+		.last_big = &pool->last_big
+	};
+}
+
+static void *
+mp_new_big_chunk(unsigned size)
+{
+	uint8_t *data = malloc(size + MP_CHUNK_TAIL);
+	if (!data) {
+		return NULL;
+	}
+	ASAN_POISON_MEMORY_REGION(data, size);
+	struct mempool_chunk *chunk = (struct mempool_chunk *)(data + size);
+	chunk->size = size;
+	return chunk;
+}
+
+static void
+mp_free_big_chunk(struct mempool_chunk *chunk)
+{
+	void *ptr = (uint8_t *)chunk - chunk->size;
+	ASAN_UNPOISON_MEMORY_REGION(ptr, chunk->size);
+	free(ptr);
+}
+
+static void *
+mp_new_chunk(unsigned size)
+{
+#ifdef CONFIG_UCW_POOL_IS_MMAP
+	uint8_t *data = page_alloc(size + MP_CHUNK_TAIL);
+	if (!data) {
+		return NULL;
+	}
+	ASAN_POISON_MEMORY_REGION(data, size);
+	struct mempool_chunk *chunk = (struct mempool_chunk *)(data + size);
+	chunk->size = size;
+	return chunk;
+#else
+	return mp_new_big_chunk(size);
+#endif
+}
+
+static void
+mp_free_chunk(struct mempool_chunk *chunk)
+{
+#ifdef CONFIG_UCW_POOL_IS_MMAP
+	uint8_t *data = (uint8_t *)chunk - chunk->size;
+	ASAN_UNPOISON_MEMORY_REGION(data, chunk->size);
+	page_free(data, chunk->size + MP_CHUNK_TAIL);
+#else
+	mp_free_big_chunk(chunk);
+#endif
+}
+
+struct mempool *
+mp_new(unsigned chunk_size)
+{
+	chunk_size = mp_align_size(MAX(sizeof(struct mempool), chunk_size));
+	struct mempool_chunk *chunk = mp_new_chunk(chunk_size);
+	struct mempool *pool = (void *)chunk - chunk_size;
+	ASAN_UNPOISON_MEMORY_REGION(pool, sizeof(*pool));
+	DBG("Creating mempool %p with %u bytes long chunks", pool, chunk_size);
+	chunk->next = NULL;
+	ASAN_POISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+	*pool = (struct mempool) {
+		.state = { .free = { chunk_size - sizeof(*pool) }, .last = { chunk } },
+		.chunk_size = chunk_size,
+		.threshold = chunk_size >> 1,
+		.last_big = &pool->last_big
+	};
+	return pool;
+}
+
+static void
+mp_free_chain(struct mempool_chunk *chunk)
+{
+	while (chunk) {
+		ASAN_UNPOISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+		struct mempool_chunk *next = chunk->next;
+		mp_free_chunk(chunk);
+		chunk = next;
+	}
+}
+
+static void
+mp_free_big_chain(struct mempool_chunk *chunk)
+{
+	while (chunk) {
+		ASAN_UNPOISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+		struct mempool_chunk *next = chunk->next;
+		mp_free_big_chunk(chunk);
+		chunk = next;
+	}
+}
+
+void
+mp_delete(struct mempool *pool)
+{
+	if (pool == NULL) {
+		return;
+	}
+	DBG("Deleting mempool %p", pool);
+	mp_free_big_chain(pool->state.last[1]);
+	mp_free_chain(pool->unused);
+	mp_free_chain(pool->state.last[0]); // can contain the mempool structure
+}
+
+void
+mp_flush(struct mempool *pool)
+{
+	mp_free_big_chain(pool->state.last[1]);
+	struct mempool_chunk *chunk = pool->state.last[0], *next;
+	while (chunk) {
+		ASAN_UNPOISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+		if ((uint8_t *)chunk - chunk->size == (uint8_t *)pool) {
+			break;
+		}
+		next = chunk->next;
+		chunk->next = pool->unused;
+		ASAN_POISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+		pool->unused = chunk;
+		chunk = next;
+	}
+	pool->state.last[0] = chunk;
+	if (chunk) {
+		pool->state.free[0] = chunk->size - sizeof(*pool);
+		ASAN_POISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+	} else {
+		pool->state.free[0] = 0;
+	}
+	pool->state.last[1] = NULL;
+	pool->state.free[1] = 0;
+	pool->last_big = &pool->last_big;
+}
+
+static void
+mp_stats_chain(struct mempool_chunk *chunk, struct mempool_stats *stats, unsigned idx)
+{
+	struct mempool_chunk *next;
+	while (chunk) {
+		ASAN_UNPOISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+		stats->chain_size[idx] += chunk->size + sizeof(*chunk);
+		stats->chain_count[idx]++;
+		next = chunk->next;
+		ASAN_POISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+		chunk = next;
+	}
+	stats->total_size += stats->chain_size[idx];
+}
+
+void
+mp_stats(struct mempool *pool, struct mempool_stats *stats)
+{
+	bzero(stats, sizeof(*stats));
+	mp_stats_chain(pool->state.last[0], stats, 0);
+	mp_stats_chain(pool->state.last[1], stats, 1);
+	mp_stats_chain(pool->unused, stats, 2);
+}
+
+uint64_t
+mp_total_size(struct mempool *pool)
+{
+	struct mempool_stats stats;
+	mp_stats(pool, &stats);
+	return stats.total_size;
+}
+
+static void *
+mp_alloc_internal(struct mempool *pool, unsigned size)
+{
+	struct mempool_chunk *chunk;
+	if (size <= pool->threshold) {
+		pool->idx = 0;
+		if (pool->unused) {
+			chunk = pool->unused;
+			ASAN_UNPOISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+			pool->unused = chunk->next;
+		} else {
+			chunk = mp_new_chunk(pool->chunk_size);
+		}
+		chunk->next = pool->state.last[0];
+		ASAN_POISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+		pool->state.last[0] = chunk;
+		pool->state.free[0] = pool->chunk_size - size;
+		return (uint8_t *)chunk - pool->chunk_size;
+	} else if (size <= MP_SIZE_MAX) {
+		pool->idx = 1;
+		unsigned aligned = ALIGN_TO(size, CPU_STRUCT_ALIGN);
+		chunk = mp_new_big_chunk(aligned);
+		if (!chunk) {
+			return NULL;
+		}
+		chunk->next = pool->state.last[1];
+		ASAN_POISON_MEMORY_REGION(chunk, sizeof(struct mempool_chunk));
+		pool->state.last[1] = chunk;
+		pool->state.free[1] = aligned - size;
+		return pool->last_big = (uint8_t *)chunk - aligned;
+	} else {
+		fprintf(stderr, "Cannot allocate %u bytes from a mempool", size);
+		assert(0);
+		return NULL;
+	}
+}
+
+void *
+mp_alloc(struct mempool *pool, unsigned size)
+{
+	unsigned avail = pool->state.free[0] & ~(CPU_STRUCT_ALIGN - 1);
+	void *ptr = NULL;
+	if (size <= avail) {
+		pool->state.free[0] = avail - size;
+		ptr = (uint8_t*)pool->state.last[0] - avail;
+	} else {
+		ptr = mp_alloc_internal(pool, size);
+	}
+	ASAN_UNPOISON_MEMORY_REGION(ptr, size);
+	return ptr;
+}
+
+void *
+mp_alloc_noalign(struct mempool *pool, unsigned size)
+{
+	void *ptr = NULL;
+	if (size <= pool->state.free[0]) {
+		ptr = (uint8_t*)pool->state.last[0] - pool->state.free[0];
+		pool->state.free[0] -= size;
+	} else {
+		ptr = mp_alloc_internal(pool, size);
+	}
+	ASAN_UNPOISON_MEMORY_REGION(ptr, size);
+	return ptr;
+}
+
+void *
+mp_alloc_zero(struct mempool *pool, unsigned size)
+{
+	void *ptr = mp_alloc(pool, size);
+	bzero(ptr, size);
+	return ptr;
+}
diff --git a/src/contrib/ucw/mempool.h b/src/contrib/ucw/mempool.h
new file mode 100644
index 0000000..c5a4fa8
--- /dev/null
+++ b/src/contrib/ucw/mempool.h
@@ -0,0 +1,124 @@
+/*
+ *	UCW Library -- Memory Pools
+ *
+ *	(c) 1997--2005 Martin Mares <mj@ucw.cz>
+ *	(c) 2007 Pavel Charvat <pchar@ucw.cz>
+ *	(c) 2015, 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+ *
+ *	This software may be freely distributed and used according to the terms
+ *	of the GNU Lesser General Public License.
+ */
+
+#pragma once
+
+#include <string.h>
+#include <stdint.h>
+
+#define CPU_STRUCT_ALIGN (sizeof(void*))
+
+/***
+ * [[defs]]
+ * Definitions
+ * -----------
+ ***/
+
+/**
+ * Memory pool state (see mp_push(), ...).
+ * You should use this one as an opaque handle only, the insides are internal.
+ **/
+struct mempool_state {
+	unsigned free[2];
+	void *last[2];
+};
+
+/**
+ * Memory pool.
+ * You should use this one as an opaque handle only, the insides are internal.
+ **/
+struct mempool {
+	struct mempool_state state;
+	void *unused, *last_big;
+	unsigned chunk_size, threshold, idx;
+};
+
+struct mempool_stats {			/** Mempool statistics. See mp_stats(). **/
+	uint64_t total_size;		/** Real allocated size in bytes. */
+	unsigned chain_count[3];	/** Number of allocated chunks in small/big/unused chains. */
+	unsigned chain_size[3];		/** Size of allocated chunks in small/big/unused chains. */
+};
+
+/***
+ * [[basic]]
+ * Basic manipulation
+ * ------------------
+ ***/
+
+/**
+ * Initialize a given mempool structure.
+ * \p chunk_size must be in the interval `[1, UINT_MAX / 2]`.
+ * It will allocate memory by this large chunks and take
+ * memory to satisfy requests from them.
+ *
+ * Memory pools can be treated as <<trans:respools,resources>>, see <<trans:res_mempool()>>.
+ **/
+void mp_init(struct mempool *pool, unsigned chunk_size);
+
+/**
+ * Allocate and initialize a new memory pool.
+ * See \ref mp_init() for \p chunk_size limitations.
+ *
+ * The new mempool structure is allocated on the new mempool.
+ *
+ * Memory pools can be treated as <<trans:respools,resources>>, see <<trans:res_mempool()>>.
+ **/
+struct mempool *mp_new(unsigned chunk_size);
+
+/**
+ * Cleanup mempool initialized by mp_init or mp_new.
+ * Frees all the memory allocated by this mempool and,
+ * if created by \ref mp_new(), the \p pool itself.
+ **/
+void mp_delete(struct mempool *pool);
+
+/**
+ * Frees all data on a memory pool, but leaves it working.
+ * It can keep some of the chunks allocated to serve
+ * further allocation requests. Leaves the \p pool alive,
+ * even if it was created with \ref mp_new().
+ **/
+void mp_flush(struct mempool *pool);
+
+/**
+ * Compute some statistics for debug purposes.
+ * See the definition of the <<struct_mempool_stats,mempool_stats structure>>.
+ **/
+void mp_stats(struct mempool *pool, struct mempool_stats *stats);
+uint64_t mp_total_size(struct mempool *pool);	/** How many bytes were allocated by the pool. **/
+
+/***
+ * [[alloc]]
+ * Allocation routines
+ * -------------------
+ ***/
+
+/**
+ * The function allocates new \p size bytes on a given memory pool.
+ * If the \p size is zero, the resulting pointer is undefined,
+ * but it may be safely reallocated or used as the parameter
+ * to other functions below.
+ *
+ * The resulting pointer is always aligned to a multiple of
+ * `CPU_STRUCT_ALIGN` bytes and this condition remains true also
+ * after future reallocations.
+ **/
+void *mp_alloc(struct mempool *pool, unsigned size);
+
+/**
+ * The same as \ref mp_alloc(), but the result may be unaligned.
+ **/
+void *mp_alloc_noalign(struct mempool *pool, unsigned size);
+
+/**
+ * The same as \ref mp_alloc(), but fills the newly allocated memory with zeroes.
+ **/
+void *mp_alloc_zero(struct mempool *pool, unsigned size);
diff --git a/src/contrib/wire_ctx.h b/src/contrib/wire_ctx.h
new file mode 100644
index 0000000..25ff143
--- /dev/null
+++ b/src/contrib/wire_ctx.h
@@ -0,0 +1,361 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include "libknot/endian.h"
+#include "libknot/errcode.h"
+
+/*!
+ * \brief Struct to keep the wire context.
+ */
+typedef struct wire_ctx {
+	size_t size;
+	uint8_t *wire;
+	uint8_t *position;
+	int error;
+	bool readonly;
+} wire_ctx_t;
+
+/*!
+ * \brief Initialize wire context.
+ */
+static inline wire_ctx_t wire_ctx_init(uint8_t *data, size_t size)
+{
+	assert(data);
+
+	wire_ctx_t result = {
+		.size = size,
+		.wire = data,
+		.position = data,
+		.error = KNOT_EOK,
+		.readonly = false
+	};
+
+	return result;
+}
+
+/*!
+ * \brief Initialize read only wire context.
+ *
+ * \note No write is performed, and error is set to KNOT_EACCES.
+ *
+ */
+static inline wire_ctx_t wire_ctx_init_const(const uint8_t *data, size_t size)
+{
+	assert(data);
+
+	wire_ctx_t result = wire_ctx_init((uint8_t *)data, size);
+	result.readonly = true;
+
+	return result;
+}
+
+/*!
+ * \brief Gets actual position.
+ *
+ * \return position from the begin.
+ */
+static inline size_t wire_ctx_offset(wire_ctx_t *ctx)
+{
+	assert(ctx);
+
+	return ctx->position - ctx->wire;
+}
+
+/*!
+ * \brief Set position offset from the begin.
+ *
+ * \param offset Wire offset (starts from 0).
+ *
+ * \note Noop if previous error.
+ */
+static inline void wire_ctx_set_offset(wire_ctx_t *ctx, size_t offset)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return;
+	}
+
+	if (offset > ctx->size) {
+		ctx->error = KNOT_ERANGE;
+		return;
+	}
+
+	ctx->position = ctx->wire + offset;
+}
+
+/*!
+ * \brief Gets available bytes.
+ *
+ * \return Number of bytes to end.
+ */
+static inline size_t wire_ctx_available(wire_ctx_t *ctx)
+{
+	assert(ctx);
+
+	return ctx->size - wire_ctx_offset(ctx);
+}
+
+/*!
+ * \brief Add offset to the current position.
+ *
+ * \note Noop if previous error.
+ */
+static inline void wire_ctx_skip(wire_ctx_t *ctx, ssize_t offset)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return;
+	}
+
+	// Check for out of scope skip.
+	if (offset >= 0) {
+		if (offset > wire_ctx_available(ctx)) {
+			ctx->error = KNOT_ERANGE;
+			return;
+		}
+	} else {
+		if (-offset > wire_ctx_offset(ctx)) {
+			ctx->error = KNOT_ERANGE;
+			return;
+		}
+	}
+
+	ctx->position += offset;
+}
+
+/*!
+ * \brief Check the context if reading is possible.
+ */
+static inline int wire_ctx_can_read(wire_ctx_t *ctx, size_t size)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return ctx->error;
+	}
+
+	if (wire_ctx_available(ctx) < size) {
+		return KNOT_EFEWDATA;
+	}
+
+	return KNOT_EOK;
+}
+
+/*!
+ * \brief Check the context if writing is possible.
+ */
+static inline int wire_ctx_can_write(wire_ctx_t *ctx, size_t size)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return ctx->error;
+	}
+
+	if (ctx->readonly) {
+		return KNOT_EACCES;
+	}
+
+	if (wire_ctx_available(ctx) < size) {
+		return KNOT_ESPACE;
+	}
+
+	return KNOT_EOK;
+}
+
+
+static inline void wire_ctx_read(wire_ctx_t *ctx, void *data, size_t size)
+{
+	assert(ctx);
+	assert(data);
+
+	if (ctx->error != KNOT_EOK) {
+		/* Avoid leaving data uninitialized. */
+		memset(data, 0, size);
+		return;
+	}
+
+	int ret = wire_ctx_can_read(ctx, size);
+	if (ret != KNOT_EOK) {
+		ctx->error = ret;
+		memset(data, 0, size);
+		return;
+	}
+
+	memcpy(data, ctx->position, size);
+	ctx->position += size;
+}
+
+static inline uint8_t wire_ctx_read_u8(wire_ctx_t *ctx)
+{
+	uint8_t result;
+	wire_ctx_read(ctx, &result, sizeof(result));
+
+	return result;
+}
+
+static inline uint16_t wire_ctx_read_u16(wire_ctx_t *ctx)
+{
+	uint16_t result;
+	wire_ctx_read(ctx, &result, sizeof(result));
+
+	return be16toh(result);
+}
+
+static inline uint32_t wire_ctx_read_u32(wire_ctx_t *ctx)
+{
+	uint32_t result;
+	wire_ctx_read(ctx, &result, sizeof(result));
+
+	return be32toh(result);
+}
+
+static inline uint64_t wire_ctx_read_u48(wire_ctx_t *ctx)
+{
+	/* This case is slightly tricky. */
+	uint64_t result = 0;
+	wire_ctx_read(ctx, (uint8_t *)&result + 1, 6);
+
+	return be64toh(result) >> 8;
+}
+
+static inline uint64_t wire_ctx_read_u64(wire_ctx_t *ctx)
+{
+	uint64_t result;
+	wire_ctx_read(ctx, &result, sizeof(result));
+
+	return be64toh(result);
+}
+
+
+static inline void wire_ctx_write(wire_ctx_t *ctx, const void *data, size_t size)
+{
+	assert(ctx);
+
+	if (ctx->error != KNOT_EOK) {
+		return;
+	}
+
+	if (size == 0) {
+		return;
+	}
+
+	assert(data);
+
+	int ret = wire_ctx_can_write(ctx, size);
+	if (ret != KNOT_EOK) {
+		ctx->error = ret;
+		return;
+	}
+
+	memcpy(ctx->position, data, size);
+	ctx->position += size;
+}
+
+static inline void wire_ctx_write_u8(wire_ctx_t *ctx, uint8_t value)
+{
+	wire_ctx_write(ctx, &value, sizeof(value));
+}
+
+static inline void wire_ctx_write_u16(wire_ctx_t *ctx, uint16_t value)
+{
+	uint16_t beval = htobe16(value);
+	wire_ctx_write(ctx, &beval, sizeof(beval));
+}
+
+static inline void wire_ctx_write_u32(wire_ctx_t *ctx, uint32_t value)
+{
+	uint32_t beval = htobe32(value);
+	wire_ctx_write(ctx, &beval, sizeof(beval));
+}
+
+static inline void wire_ctx_write_u48(wire_ctx_t *ctx, uint64_t value)
+{
+	/* This case is slightly tricky. */
+	uint64_t swapped = htobe64(value << 8);
+	wire_ctx_write(ctx, (uint8_t *)&swapped + 1, 6);
+}
+
+static inline void wire_ctx_write_u64(wire_ctx_t *ctx, uint64_t value)
+{
+	uint64_t beval = htobe64(value);
+	wire_ctx_write(ctx, &beval, sizeof(beval));
+}
+
+
+static inline void wire_ctx_memset(wire_ctx_t *dst, int value, size_t size)
+{
+	assert(dst);
+
+	if (dst->error != KNOT_EOK) {
+		return;
+	}
+
+	if (size == 0) {
+		return;
+	}
+
+	int ret = wire_ctx_can_write(dst, size);
+	if (ret != KNOT_EOK) {
+		dst->error = ret;
+		return;
+	}
+
+	memset(dst->position, value, size);
+	dst->position += size;
+}
+
+static inline void wire_ctx_clear(wire_ctx_t *ctx, size_t size)
+{
+	wire_ctx_memset(ctx, 0, size);
+}
+
+static inline void wire_ctx_copy(wire_ctx_t *dst, wire_ctx_t *src, size_t size)
+{
+	assert(dst);
+	assert(src);
+
+	if (size == 0 || dst->error != KNOT_EOK) {
+		return;
+	}
+
+	if (wire_ctx_can_read(src, size) != KNOT_EOK) {
+		dst->error = KNOT_EFEWDATA;
+		return;
+	}
+
+	int ret = wire_ctx_can_write(dst, size);
+	if (ret != KNOT_EOK) {
+		dst->error = ret;
+		return;
+	}
+
+	memcpy(dst->position, src->position, size);
+	dst->position += size;
+	src->position += size;
+}
+