Adding upstream version 1.44.3.upstream/1.44.3

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

1 files changed, 1699 insertions, 0 deletions

diff --git a/fluent-bit/lib/snappy-fef67ac/snappy.c b/fluent-bit/lib/snappy-fef67ac/snappy.c
new file mode 100644
index 000000000..8c24b9711
--- /dev/null
+++ b/fluent-bit/lib/snappy-fef67ac/snappy.c
@@ -0,0 +1,1699 @@
+/*
+ * C port of the snappy compressor from Google.
+ * This is a very fast compressor with comparable compression to lzo.
+ * Works best on 64bit little-endian, but should be good on others too.
+ * Ported by Andi Kleen.
+ * Uptodate with snappy 1.1.0
+ */
+
+/*
+ * Copyright 2005 Google Inc. All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of Google Inc. 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
+ * OWNER 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.
+ */
+
+#ifdef __KERNEL__
+#include <linux/kernel.h>
+#ifdef SG
+#include <linux/uio.h>
+#endif
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/snappy.h>
+#include <linux/vmalloc.h>
+#include <asm/unaligned.h>
+#else
+#include "snappy.h"
+#include "compat.h"
+#endif
+
+static inline void put_unaligned16(u16 v, u16 *x)
+{
+	memcpy(x, &v, sizeof(u16));
+}
+
+static inline u16 get_unaligned16(u16 *x)
+{
+	u16 _ret;
+	memcpy(&_ret, x, sizeof(u16));
+	return _ret;
+}
+
+static inline void put_unaligned32(u32 v, u32 *x)
+{
+	memcpy(x, &v, sizeof(u32));
+}
+
+static inline u32 get_unaligned32(u32 *x)
+{
+	u32 _ret;
+	memcpy(&_ret, x, sizeof(u32));
+	return _ret;
+}
+
+static inline void put_unaligned64(u64 v, u64 *x)
+{
+	memcpy(x, &v, sizeof(u64));
+}
+
+static inline u64 get_unaligned64(u64 *x)
+{
+	u64 _ret;
+	memcpy(&_ret, x, sizeof(u64));
+	return _ret;
+}
+
+#define get_unaligned_le32(x) (le32toh(get_unaligned32((u32 *)(x))))
+#define put_unaligned_le16(v,x) (put_unaligned16(htole16(v), (u16 *)(x)))
+
+#define CRASH_UNLESS(x) BUG_ON(!(x))
+#define CHECK(cond) CRASH_UNLESS(cond)
+#define CHECK_LE(a, b) CRASH_UNLESS((a) <= (b))
+#define CHECK_GE(a, b) CRASH_UNLESS((a) >= (b))
+#define CHECK_EQ(a, b) CRASH_UNLESS((a) == (b))
+#define CHECK_NE(a, b) CRASH_UNLESS((a) != (b))
+#define CHECK_LT(a, b) CRASH_UNLESS((a) < (b))
+#define CHECK_GT(a, b) CRASH_UNLESS((a) > (b))
+
+#define UNALIGNED_LOAD16(_p) get_unaligned16((u16 *)(_p))
+#define UNALIGNED_LOAD32(_p) get_unaligned32((u32 *)(_p))
+#define UNALIGNED_LOAD64(_p) get_unaligned64((u64 *)(_p))
+
+#define UNALIGNED_STORE16(_p, _val) put_unaligned16(_val, (u16 *)(_p))
+#define UNALIGNED_STORE32(_p, _val) put_unaligned32(_val, (u32 *)(_p))
+#define UNALIGNED_STORE64(_p, _val) put_unaligned64(_val, (u64 *)(_p))
+
+/*
+ * This can be more efficient than UNALIGNED_LOAD64 + UNALIGNED_STORE64
+ * on some platforms, in particular ARM.
+ */
+static inline void unaligned_copy64(const void *src, void *dst)
+{
+	if (sizeof(void *) == 8) {
+		UNALIGNED_STORE64(dst, UNALIGNED_LOAD64(src));
+	} else {
+		const char *src_char = (const char *)(src);
+		char *dst_char = (char *)(dst);
+
+		UNALIGNED_STORE32(dst_char, UNALIGNED_LOAD32(src_char));
+		UNALIGNED_STORE32(dst_char + 4, UNALIGNED_LOAD32(src_char + 4));
+	}
+}
+
+#ifdef NDEBUG
+
+#define DCHECK(cond) do {} while(0)
+#define DCHECK_LE(a, b) do {} while(0)
+#define DCHECK_GE(a, b) do {} while(0)
+#define DCHECK_EQ(a, b) do {} while(0)
+#define DCHECK_NE(a, b) do {} while(0)
+#define DCHECK_LT(a, b) do {} while(0)
+#define DCHECK_GT(a, b) do {} while(0)
+
+#else
+
+#define DCHECK(cond) CHECK(cond)
+#define DCHECK_LE(a, b) CHECK_LE(a, b)
+#define DCHECK_GE(a, b) CHECK_GE(a, b)
+#define DCHECK_EQ(a, b) CHECK_EQ(a, b)
+#define DCHECK_NE(a, b) CHECK_NE(a, b)
+#define DCHECK_LT(a, b) CHECK_LT(a, b)
+#define DCHECK_GT(a, b) CHECK_GT(a, b)
+
+#endif
+
+/* This snipped is based on the following file
+ * https://github.com/edenhill/librdkafka/blob/7230a1aa327b55ace54579d019e9484af96886c6/src/snappy.c
+ */
+#if !defined(__WIN32__)
+#	define snappy_clz(n)   __builtin_clz(n)
+#	define snappy_ctz(n)   __builtin_ctz(n)
+#	define snappy_ctz64(n) __builtin_ctzll(n)
+#else
+#include <intrin.h>
+static int inline snappy_clz(u32 x) {
+	int r = 0;
+	if (_BitScanForward(&r, x))
+		return 31 - r;
+	else
+		return 32;
+}
+
+static int inline snappy_ctz(u32 x) {
+	int r = 0;
+	if (_BitScanForward(&r, x))
+		return r;
+	else
+		return 32;
+}
+
+static int inline snappy_ctz64(u64 x) {
+#ifdef _M_X64
+	int r = 0;
+	if (_BitScanReverse64(&r, x))
+		return r;
+	else
+		return 64;
+#else
+	int r;
+	if ((r = snappy_ctz(x & 0xffffffff)) < 32)
+		return r;
+	return 32 + snappy_ctz(x >> 32);
+#endif
+}
+#endif
+
+static inline bool is_little_endian(void)
+{
+#ifdef __LITTLE_ENDIAN__
+	return true;
+#endif
+	return false;
+}
+
+static inline int log2_floor(u32 n)
+{
+	return n == 0 ? -1 : 31 ^ snappy_clz(n);
+}
+
+static inline int find_lsb_set_non_zero(u32 n)
+{
+	return snappy_ctz(n);
+}
+
+static inline int find_lsb_set_non_zero64(u64 n)
+{
+	return snappy_ctz64(n);
+}
+
+#define kmax32 5
+
+/*
+ * Attempts to parse a varint32 from a prefix of the bytes in [ptr,limit-1].
+ *  Never reads a character at or beyond limit.  If a valid/terminated varint32
+ * was found in the range, stores it in *OUTPUT and returns a pointer just
+ * past the last byte of the varint32. Else returns NULL.  On success,
+ * "result <= limit".
+ */
+static inline const char *varint_parse32_with_limit(const char *p,
+						    const char *l,
+						    u32 * OUTPUT)
+{
+	const unsigned char *ptr = (const unsigned char *)(p);
+	const unsigned char *limit = (const unsigned char *)(l);
+	u32 b, result;
+
+	if (ptr >= limit)
+		return NULL;
+	b = *(ptr++);
+	result = b & 127;
+	if (b < 128)
+		goto done;
+	if (ptr >= limit)
+		return NULL;
+	b = *(ptr++);
+	result |= (b & 127) << 7;
+	if (b < 128)
+		goto done;
+	if (ptr >= limit)
+		return NULL;
+	b = *(ptr++);
+	result |= (b & 127) << 14;
+	if (b < 128)
+		goto done;
+	if (ptr >= limit)
+		return NULL;
+	b = *(ptr++);
+	result |= (b & 127) << 21;
+	if (b < 128)
+		goto done;
+	if (ptr >= limit)
+		return NULL;
+	b = *(ptr++);
+	result |= (b & 127) << 28;
+	if (b < 16)
+		goto done;
+	return NULL;		/* Value is too long to be a varint32 */
+done:
+	*OUTPUT = result;
+	return (const char *)(ptr);
+}
+
+/*
+ * REQUIRES   "ptr" points to a buffer of length sufficient to hold "v".
+ *  EFFECTS    Encodes "v" into "ptr" and returns a pointer to the
+ *            byte just past the last encoded byte.
+ */
+static inline char *varint_encode32(char *sptr, u32 v)
+{
+	/* Operate on characters as unsigneds */
+	unsigned char *ptr = (unsigned char *)(sptr);
+	static const int B = 128;
+
+	if (v < (1 << 7)) {
+		*(ptr++) = v;
+	} else if (v < (1 << 14)) {
+		*(ptr++) = v | B;
+		*(ptr++) = v >> 7;
+	} else if (v < (1 << 21)) {
+		*(ptr++) = v | B;
+		*(ptr++) = (v >> 7) | B;
+		*(ptr++) = v >> 14;
+	} else if (v < (1 << 28)) {
+		*(ptr++) = v | B;
+		*(ptr++) = (v >> 7) | B;
+		*(ptr++) = (v >> 14) | B;
+		*(ptr++) = v >> 21;
+	} else {
+		*(ptr++) = v | B;
+		*(ptr++) = (v >> 7) | B;
+		*(ptr++) = (v >> 14) | B;
+		*(ptr++) = (v >> 21) | B;
+		*(ptr++) = v >> 28;
+	}
+	return (char *)(ptr);
+}
+
+#ifdef SG
+
+static inline void *n_bytes_after_addr(void *addr, size_t n_bytes)
+{
+    return (void *) ((char *)addr + n_bytes);
+}
+
+struct source {
+	struct iovec *iov;
+	int iovlen;
+	int curvec;
+	int curoff;
+	size_t total;
+};
+
+/* Only valid at beginning when nothing is consumed */
+static inline int available(struct source *s)
+{
+	return s->total;
+}
+
+static inline const char *peek(struct source *s, size_t *len)
+{
+	if (likely(s->curvec < s->iovlen)) {
+		struct iovec *iv = &s->iov[s->curvec];
+		if (s->curoff < iv->iov_len) { 
+			*len = iv->iov_len - s->curoff;
+			return n_bytes_after_addr(iv->iov_base, s->curoff);
+		}
+	}
+	*len = 0;
+	return NULL;
+}
+
+static inline void skip(struct source *s, size_t n)
+{
+	struct iovec *iv = &s->iov[s->curvec];
+	s->curoff += n;
+	DCHECK_LE(s->curoff, iv->iov_len);
+	if (s->curoff >= iv->iov_len && s->curvec + 1 < s->iovlen) {
+		s->curoff = 0;
+		s->curvec++;
+	}
+}
+
+struct sink {
+	struct iovec *iov;
+	int iovlen;
+	unsigned curvec;
+	unsigned curoff;
+	unsigned written;
+};
+
+static inline void append(struct sink *s, const char *data, size_t n)
+{
+	struct iovec *iov = &s->iov[s->curvec];
+	char *dst = n_bytes_after_addr(iov->iov_base, s->curoff);
+	size_t nlen = min_t(size_t, iov->iov_len - s->curoff, n);
+	if (data != dst)
+		memcpy(dst, data, nlen);
+	s->written += n;
+	s->curoff += nlen;
+	while ((n -= nlen) > 0) {
+		data += nlen;
+		s->curvec++;
+		DCHECK_LT(s->curvec, s->iovlen);
+		iov++;
+		nlen = min_t(size_t, iov->iov_len, n);
+		memcpy(iov->iov_base, data, nlen);
+		s->curoff = nlen;
+	}
+}
+
+static inline void *sink_peek(struct sink *s, size_t n)
+{
+	struct iovec *iov = &s->iov[s->curvec];
+	if (s->curvec < iov->iov_len && iov->iov_len - s->curoff >= n)
+		return n_bytes_after_addr(iov->iov_base, s->curoff);
+	return NULL;
+}
+
+#else
+
+struct source {
+	const char *ptr;
+	size_t left;
+};
+
+static inline int available(struct source *s)
+{
+	return s->left;
+}
+
+static inline const char *peek(struct source *s, size_t * len)
+{
+	*len = s->left;
+	return s->ptr;
+}
+
+static inline void skip(struct source *s, size_t n)
+{
+	s->left -= n;
+	s->ptr += n;
+}
+
+struct sink {
+	char *dest;
+};
+
+static inline void append(struct sink *s, const char *data, size_t n)
+{
+	if (data != s->dest)
+		memcpy(s->dest, data, n);
+	s->dest += n;
+}
+
+#define sink_peek(s, n) sink_peek_no_sg(s)
+
+static inline void *sink_peek_no_sg(const struct sink *s)
+{
+	return s->dest;
+}
+
+#endif
+
+struct writer {
+	char *base;
+	char *op;
+	char *op_limit;
+};
+
+/* Called before decompression */
+static inline void writer_set_expected_length(struct writer *w, size_t len)
+{
+	w->op_limit = w->op + len;
+}
+
+/* Called after decompression */
+static inline bool writer_check_length(struct writer *w)
+{
+	return w->op == w->op_limit;
+}
+
+/*
+ * Copy "len" bytes from "src" to "op", one byte at a time.  Used for
+ *  handling COPY operations where the input and output regions may
+ * overlap.  For example, suppose:
+ *    src    == "ab"
+ *    op     == src + 2
+ *    len    == 20
+ * After IncrementalCopy(src, op, len), the result will have
+ * eleven copies of "ab"
+ *    ababababababababababab
+ * Note that this does not match the semantics of either memcpy()
+ * or memmove().
+ */
+static inline void incremental_copy(const char *src, char *op, ssize_t len)
+{
+	DCHECK_GT(len, 0);
+	do {
+		*op++ = *src++;
+	} while (--len > 0);
+}
+
+/*
+ * Equivalent to IncrementalCopy except that it can write up to ten extra
+ *  bytes after the end of the copy, and that it is faster.
+ *
+ * The main part of this loop is a simple copy of eight bytes at a time until
+ * we've copied (at least) the requested amount of bytes.  However, if op and
+ * src are less than eight bytes apart (indicating a repeating pattern of
+ * length < 8), we first need to expand the pattern in order to get the correct
+ * results. For instance, if the buffer looks like this, with the eight-byte
+ * <src> and <op> patterns marked as intervals:
+ *
+ *    abxxxxxxxxxxxx
+ *    [------]           src
+ *      [------]         op
+ *
+ * a single eight-byte copy from <src> to <op> will repeat the pattern once,
+ * after which we can move <op> two bytes without moving <src>:
+ *
+ *    ababxxxxxxxxxx
+ *    [------]           src
+ *        [------]       op
+ *
+ * and repeat the exercise until the two no longer overlap.
+ *
+ * This allows us to do very well in the special case of one single byte
+ * repeated many times, without taking a big hit for more general cases.
+ *
+ * The worst case of extra writing past the end of the match occurs when
+ * op - src == 1 and len == 1; the last copy will read from byte positions
+ * [0..7] and write to [4..11], whereas it was only supposed to write to
+ * position 1. Thus, ten excess bytes.
+ */
+
+#define kmax_increment_copy_overflow  10
+
+static inline void incremental_copy_fast_path(const char *src, char *op,
+					      ssize_t len)
+{
+	while (op - src < 8) {
+		unaligned_copy64(src, op);
+		len -= op - src;
+		op += op - src;
+	}
+	while (len > 0) {
+		unaligned_copy64(src, op);
+		src += 8;
+		op += 8;
+		len -= 8;
+	}
+}
+
+static inline bool writer_append_from_self(struct writer *w, u32 offset,
+					   u32 len)
+{
+	char *const op = w->op;
+	CHECK_LE(op, w->op_limit);
+	const u32 space_left = w->op_limit - op;
+
+	if (op - w->base <= offset - 1u)	/* -1u catches offset==0 */
+		return false;
+	if (len <= 16 && offset >= 8 && space_left >= 16) {
+		/* Fast path, used for the majority (70-80%) of dynamic
+		 * invocations. */
+		unaligned_copy64(op - offset, op);
+		unaligned_copy64(op - offset + 8, op + 8);
+	} else {
+		if (space_left >= len + kmax_increment_copy_overflow) {
+			incremental_copy_fast_path(op - offset, op, len);
+		} else {
+			if (space_left < len) {
+				return false;
+			}
+			incremental_copy(op - offset, op, len);
+		}
+	}
+
+	w->op = op + len;
+	return true;
+}
+
+static inline bool writer_append(struct writer *w, const char *ip, u32 len)
+{
+	char *const op = w->op;
+	CHECK_LE(op, w->op_limit);
+	const u32 space_left = w->op_limit - op;
+	if (space_left < len)
+		return false;
+	memcpy(op, ip, len);
+	w->op = op + len;
+	return true;
+}
+
+static inline bool writer_try_fast_append(struct writer *w, const char *ip, 
+					  u32 available_bytes, u32 len)
+{
+	char *const op = w->op;
+	const int space_left = w->op_limit - op;
+	if (len <= 16 && available_bytes >= 16 && space_left >= 16) {
+		/* Fast path, used for the majority (~95%) of invocations */
+		unaligned_copy64(ip, op);
+		unaligned_copy64(ip + 8, op + 8);
+		w->op = op + len;
+		return true;
+	}
+	return false;
+}
+
+/*
+ * Any hash function will produce a valid compressed bitstream, but a good
+ * hash function reduces the number of collisions and thus yields better
+ * compression for compressible input, and more speed for incompressible
+ * input. Of course, it doesn't hurt if the hash function is reasonably fast
+ * either, as it gets called a lot.
+ */
+static inline u32 hash_bytes(u32 bytes, int shift)
+{
+	u32 kmul = 0x1e35a7bd;
+	return (bytes * kmul) >> shift;
+}
+
+static inline u32 hash(const char *p, int shift)
+{
+	return hash_bytes(UNALIGNED_LOAD32(p), shift);
+}
+
+/*
+ * Compressed data can be defined as:
+ *    compressed := item* literal*
+ *    item       := literal* copy
+ *
+ * The trailing literal sequence has a space blowup of at most 62/60
+ * since a literal of length 60 needs one tag byte + one extra byte
+ * for length information.
+ *
+ * Item blowup is trickier to measure.  Suppose the "copy" op copies
+ * 4 bytes of data.  Because of a special check in the encoding code,
+ * we produce a 4-byte copy only if the offset is < 65536.  Therefore
+ * the copy op takes 3 bytes to encode, and this type of item leads
+ * to at most the 62/60 blowup for representing literals.
+ *
+ * Suppose the "copy" op copies 5 bytes of data.  If the offset is big
+ * enough, it will take 5 bytes to encode the copy op.  Therefore the
+ * worst case here is a one-byte literal followed by a five-byte copy.
+ * I.e., 6 bytes of input turn into 7 bytes of "compressed" data.
+ *
+ * This last factor dominates the blowup, so the final estimate is:
+ */
+size_t snappy_max_compressed_length(size_t source_len)
+{
+	return 32 + source_len + source_len / 6;
+}
+EXPORT_SYMBOL(snappy_max_compressed_length);
+
+enum {
+	LITERAL = 0,
+	COPY_1_BYTE_OFFSET = 1,	/* 3 bit length + 3 bits of offset in opcode */
+	COPY_2_BYTE_OFFSET = 2,
+	COPY_4_BYTE_OFFSET = 3
+};
+
+static inline char *emit_literal(char *op,
+				 const char *literal,
+				 int len, bool allow_fast_path)
+{
+	int n = len - 1;	/* Zero-length literals are disallowed */
+
+	if (n < 60) {
+		/* Fits in tag byte */
+		*op++ = LITERAL | (n << 2);
+
+/*
+ * The vast majority of copies are below 16 bytes, for which a
+ * call to memcpy is overkill. This fast path can sometimes
+ * copy up to 15 bytes too much, but that is okay in the
+ * main loop, since we have a bit to go on for both sides:
+ *
+ *   - The input will always have kInputMarginBytes = 15 extra
+ *     available bytes, as long as we're in the main loop, and
+ *     if not, allow_fast_path = false.
+ *   - The output will always have 32 spare bytes (see
+ *     MaxCompressedLength).
+ */
+		if (allow_fast_path && len <= 16) {
+			unaligned_copy64(literal, op);
+			unaligned_copy64(literal + 8, op + 8);
+			return op + len;
+		}
+	} else {
+		/* Encode in upcoming bytes */
+		char *base = op;
+		int count = 0;
+		op++;
+		while (n > 0) {
+			*op++ = n & 0xff;
+			n >>= 8;
+			count++;
+		}
+		DCHECK(count >= 1);
+		DCHECK(count <= 4);
+		*base = LITERAL | ((59 + count) << 2);
+	}
+	memcpy(op, literal, len);
+	return op + len;
+}
+
+static inline char *emit_copy_less_than64(char *op, int offset, int len)
+{
+	DCHECK_LE(len, 64);
+	DCHECK_GE(len, 4);
+	DCHECK_LT(offset, 65536);
+
+	if ((len < 12) && (offset < 2048)) {
+		int len_minus_4 = len - 4;
+		DCHECK(len_minus_4 < 8);	/* Must fit in 3 bits */
+		*op++ =
+		    COPY_1_BYTE_OFFSET + ((len_minus_4) << 2) + ((offset >> 8)
+								 << 5);
+		*op++ = offset & 0xff;
+	} else {
+		*op++ = COPY_2_BYTE_OFFSET + ((len - 1) << 2);
+		put_unaligned_le16(offset, op);
+		op += 2;
+	}
+	return op;
+}
+
+static inline char *emit_copy(char *op, int offset, int len)
+{
+	/*
+	 * Emit 64 byte copies but make sure to keep at least four bytes
+	 * reserved
+	 */
+	while (len >= 68) {
+		op = emit_copy_less_than64(op, offset, 64);
+		len -= 64;
+	}
+
+	/*
+	 * Emit an extra 60 byte copy if have too much data to fit in
+	 * one copy
+	 */
+	if (len > 64) {
+		op = emit_copy_less_than64(op, offset, 60);
+		len -= 60;
+	}
+
+	/* Emit remainder */
+	op = emit_copy_less_than64(op, offset, len);
+	return op;
+}
+
+/**
+ * snappy_uncompressed_length - return length of uncompressed output.
+ * @start: compressed buffer
+ * @n: length of compressed buffer.
+ * @result: Write the length of the uncompressed output here.
+ *
+ * Returns true when successfull, otherwise false.
+ */
+bool snappy_uncompressed_length(const char *start, size_t n, size_t * result)
+{
+	u32 v = 0;
+	const char *limit = start + n;
+	if (varint_parse32_with_limit(start, limit, &v) != NULL) {
+		*result = v;
+		return true;
+	} else {
+		return false;
+	}
+}
+EXPORT_SYMBOL(snappy_uncompressed_length);
+
+/*
+ * The size of a compression block. Note that many parts of the compression
+ * code assumes that kBlockSize <= 65536; in particular, the hash table
+ * can only store 16-bit offsets, and EmitCopy() also assumes the offset
+ * is 65535 bytes or less. Note also that if you change this, it will
+ * affect the framing format
+ * Note that there might be older data around that is compressed with larger
+ * block sizes, so the decompression code should not rely on the
+ * non-existence of long backreferences.
+ */
+#define kblock_log 16
+#define kblock_size (1 << kblock_log)
+
+/* 
+ * This value could be halfed or quartered to save memory 
+ * at the cost of slightly worse compression.
+ */
+#define kmax_hash_table_bits 14
+#define kmax_hash_table_size (1U << kmax_hash_table_bits)
+
+/*
+ * Use smaller hash table when input.size() is smaller, since we
+ * fill the table, incurring O(hash table size) overhead for
+ * compression, and if the input is short, we won't need that
+ * many hash table entries anyway.
+ */
+static u16 *get_hash_table(struct snappy_env *env, size_t input_size,
+			      int *table_size)
+{
+	unsigned htsize = 256;
+
+	DCHECK(kmax_hash_table_size >= 256);
+	while (htsize < kmax_hash_table_size && htsize < input_size)
+		htsize <<= 1;
+	CHECK_EQ(0, htsize & (htsize - 1));
+	CHECK_LE(htsize, kmax_hash_table_size);
+
+	u16 *table;
+	table = env->hash_table;
+
+	*table_size = htsize;
+	memset(table, 0, htsize * sizeof(*table));
+	return table;
+}
+
+/*
+ * Return the largest n such that
+ *
+ *   s1[0,n-1] == s2[0,n-1]
+ *   and n <= (s2_limit - s2).
+ *
+ * Does not read *s2_limit or beyond.
+ * Does not read *(s1 + (s2_limit - s2)) or beyond.
+ * Requires that s2_limit >= s2.
+ *
+ * Separate implementation for x86_64, for speed.  Uses the fact that
+ * x86_64 is little endian.
+ */
+#if defined(__LITTLE_ENDIAN__) && BITS_PER_LONG == 64
+static inline int find_match_length(const char *s1,
+				    const char *s2, const char *s2_limit)
+{
+	int matched = 0;
+
+	DCHECK_GE(s2_limit, s2);
+	/*
+	 * Find out how long the match is. We loop over the data 64 bits at a
+	 * time until we find a 64-bit block that doesn't match; then we find
+	 * the first non-matching bit and use that to calculate the total
+	 * length of the match.
+	 */
+	while (likely(s2 <= s2_limit - 8)) {
+		if (unlikely
+		    (UNALIGNED_LOAD64(s2) == UNALIGNED_LOAD64(s1 + matched))) {
+			s2 += 8;
+			matched += 8;
+		} else {
+			/*
+			 * On current (mid-2008) Opteron models there
+			 * is a 3% more efficient code sequence to
+			 * find the first non-matching byte.  However,
+			 * what follows is ~10% better on Intel Core 2
+			 * and newer, and we expect AMD's bsf
+			 * instruction to improve.
+			 */
+			u64 x =
+			    UNALIGNED_LOAD64(s2) ^ UNALIGNED_LOAD64(s1 +
+								    matched);
+			int matching_bits = find_lsb_set_non_zero64(x);
+			matched += matching_bits >> 3;
+			return matched;
+		}
+	}
+	while (likely(s2 < s2_limit)) {
+		if (likely(s1[matched] == *s2)) {
+			++s2;
+			++matched;
+		} else {
+			return matched;
+		}
+	}
+	return matched;
+}
+#else
+static inline int find_match_length(const char *s1,
+				    const char *s2, const char *s2_limit)
+{
+	/* Implementation based on the x86-64 version, above. */
+	DCHECK_GE(s2_limit, s2);
+	int matched = 0;
+
+	while (s2 <= s2_limit - 4 &&
+	       UNALIGNED_LOAD32(s2) == UNALIGNED_LOAD32(s1 + matched)) {
+		s2 += 4;
+		matched += 4;
+	}
+	if (is_little_endian() && s2 <= s2_limit - 4) {
+		u32 x =
+		    UNALIGNED_LOAD32(s2) ^ UNALIGNED_LOAD32(s1 + matched);
+		int matching_bits = find_lsb_set_non_zero(x);
+		matched += matching_bits >> 3;
+	} else {
+		while ((s2 < s2_limit) && (s1[matched] == *s2)) {
+			++s2;
+			++matched;
+		}
+	}
+	return matched;
+}
+#endif
+
+/*
+ * For 0 <= offset <= 4, GetU32AtOffset(GetEightBytesAt(p), offset) will
+ *  equal UNALIGNED_LOAD32(p + offset).  Motivation: On x86-64 hardware we have
+ * empirically found that overlapping loads such as
+ *  UNALIGNED_LOAD32(p) ... UNALIGNED_LOAD32(p+1) ... UNALIGNED_LOAD32(p+2)
+ * are slower than UNALIGNED_LOAD64(p) followed by shifts and casts to u32.
+ *
+ * We have different versions for 64- and 32-bit; ideally we would avoid the
+ * two functions and just inline the UNALIGNED_LOAD64 call into
+ * GetUint32AtOffset, but GCC (at least not as of 4.6) is seemingly not clever
+ * enough to avoid loading the value multiple times then. For 64-bit, the load
+ * is done when GetEightBytesAt() is called, whereas for 32-bit, the load is
+ * done at GetUint32AtOffset() time.
+ */
+
+#if BITS_PER_LONG == 64
+
+typedef u64 eight_bytes_reference;
+
+static inline eight_bytes_reference get_eight_bytes_at(const char* ptr)
+{
+	return UNALIGNED_LOAD64(ptr);
+}
+
+static inline u32 get_u32_at_offset(u64 v, int offset)
+{
+	DCHECK_GE(offset, 0);
+	DCHECK_LE(offset, 4);
+	return v >> (is_little_endian()? 8 * offset : 32 - 8 * offset);
+}
+
+#else
+
+typedef const char *eight_bytes_reference;
+
+static inline eight_bytes_reference get_eight_bytes_at(const char* ptr) 
+{
+	return ptr;
+}
+
+static inline u32 get_u32_at_offset(const char *v, int offset) 
+{
+	DCHECK_GE(offset, 0);
+	DCHECK_LE(offset, 4);
+	return UNALIGNED_LOAD32(v + offset);
+}
+#endif
+
+/*
+ * Flat array compression that does not emit the "uncompressed length"
+ *  prefix. Compresses "input" string to the "*op" buffer.
+ *
+ * REQUIRES: "input" is at most "kBlockSize" bytes long.
+ * REQUIRES: "op" points to an array of memory that is at least
+ * "MaxCompressedLength(input.size())" in size.
+ * REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
+ * REQUIRES: "table_size" is a power of two
+ *
+ * Returns an "end" pointer into "op" buffer.
+ * "end - op" is the compressed size of "input".
+ */
+
+static char *compress_fragment(const char *const input,
+			       const size_t input_size,
+			       char *op, u16 * table, const unsigned table_size)
+{
+	/* "ip" is the input pointer, and "op" is the output pointer. */
+	const char *ip = input;
+	CHECK_LE(input_size, kblock_size);
+	CHECK_EQ(table_size & (table_size - 1), 0);
+	const int shift = 32 - log2_floor(table_size);
+	DCHECK_EQ(UINT_MAX >> shift, table_size - 1);
+	const char *ip_end = input + input_size;
+	const char *baseip = ip;
+	/*
+	 * Bytes in [next_emit, ip) will be emitted as literal bytes.  Or
+	 *  [next_emit, ip_end) after the main loop.
+	 */
+	const char *next_emit = ip;
+
+	const unsigned kinput_margin_bytes = 15;
+
+	if (likely(input_size >= kinput_margin_bytes)) {
+		const char *const ip_limit = input + input_size -
+			kinput_margin_bytes;
+
+		u32 next_hash;
+		for (next_hash = hash(++ip, shift);;) {
+			DCHECK_LT(next_emit, ip);
+/*
+ * The body of this loop calls EmitLiteral once and then EmitCopy one or
+ * more times.  (The exception is that when we're close to exhausting
+ * the input we goto emit_remainder.)
+ *
+ * In the first iteration of this loop we're just starting, so
+ * there's nothing to copy, so calling EmitLiteral once is
+ * necessary.  And we only start a new iteration when the
+ * current iteration has determined that a call to EmitLiteral will
+ * precede the next call to EmitCopy (if any).
+ *
+ * Step 1: Scan forward in the input looking for a 4-byte-long match.
+ * If we get close to exhausting the input then goto emit_remainder.
+ *
+ * Heuristic match skipping: If 32 bytes are scanned with no matches
+ * found, start looking only at every other byte. If 32 more bytes are
+ * scanned, look at every third byte, etc.. When a match is found,
+ * immediately go back to looking at every byte. This is a small loss
+ * (~5% performance, ~0.1% density) for lcompressible data due to more
+ * bookkeeping, but for non-compressible data (such as JPEG) it's a huge
+ * win since the compressor quickly "realizes" the data is incompressible
+ * and doesn't bother looking for matches everywhere.
+ *
+ * The "skip" variable keeps track of how many bytes there are since the
+ * last match; dividing it by 32 (ie. right-shifting by five) gives the
+ * number of bytes to move ahead for each iteration.
+ */
+			u32 skip_bytes = 32;
+
+			const char *next_ip = ip;
+			const char *candidate;
+			do {
+				ip = next_ip;
+				u32 hval = next_hash;
+				DCHECK_EQ(hval, hash(ip, shift));
+				u32 bytes_between_hash_lookups = skip_bytes++ >> 5;
+				next_ip = ip + bytes_between_hash_lookups;
+				if (unlikely(next_ip > ip_limit)) {
+					goto emit_remainder;
+				}
+				next_hash = hash(next_ip, shift);
+				candidate = baseip + table[hval];
+				DCHECK_GE(candidate, baseip);
+				DCHECK_LT(candidate, ip);
+
+				table[hval] = ip - baseip;
+			} while (likely(UNALIGNED_LOAD32(ip) !=
+					UNALIGNED_LOAD32(candidate)));
+
+/*
+ * Step 2: A 4-byte match has been found.  We'll later see if more
+ * than 4 bytes match.  But, prior to the match, input
+ * bytes [next_emit, ip) are unmatched.  Emit them as "literal bytes."
+ */
+			DCHECK_LE(next_emit + 16, ip_end);
+			op = emit_literal(op, next_emit, ip - next_emit, true);
+
+/*
+ * Step 3: Call EmitCopy, and then see if another EmitCopy could
+ * be our next move.  Repeat until we find no match for the
+ * input immediately after what was consumed by the last EmitCopy call.
+ *
+ * If we exit this loop normally then we need to call EmitLiteral next,
+ * though we don't yet know how big the literal will be.  We handle that
+ * by proceeding to the next iteration of the main loop.  We also can exit
+ * this loop via goto if we get close to exhausting the input.
+ */
+			eight_bytes_reference input_bytes;
+			u32 candidate_bytes = 0;
+
+			do {
+/*
+ * We have a 4-byte match at ip, and no need to emit any
+ *  "literal bytes" prior to ip.
+ */
+				const char *base = ip;
+				int matched = 4 +
+				    find_match_length(candidate + 4, ip + 4,
+						      ip_end);
+				ip += matched;
+				int offset = base - candidate;
+				DCHECK_EQ(0, memcmp(base, candidate, matched));
+				op = emit_copy(op, offset, matched);
+/*
+ * We could immediately start working at ip now, but to improve
+ * compression we first update table[Hash(ip - 1, ...)].
+ */
+				const char *insert_tail = ip - 1;
+				next_emit = ip;
+				if (unlikely(ip >= ip_limit)) {
+					goto emit_remainder;
+				}
+				input_bytes = get_eight_bytes_at(insert_tail);
+				u32 prev_hash =
+				    hash_bytes(get_u32_at_offset
+					       (input_bytes, 0), shift);
+				table[prev_hash] = ip - baseip - 1;
+				u32 cur_hash =
+				    hash_bytes(get_u32_at_offset
+					       (input_bytes, 1), shift);
+				candidate = baseip + table[cur_hash];
+				candidate_bytes = UNALIGNED_LOAD32(candidate);
+				table[cur_hash] = ip - baseip;
+			} while (get_u32_at_offset(input_bytes, 1) ==
+				 candidate_bytes);
+
+			next_hash =
+			    hash_bytes(get_u32_at_offset(input_bytes, 2),
+				       shift);
+			++ip;
+		}
+	}
+
+emit_remainder:
+	/* Emit the remaining bytes as a literal */
+	if (next_emit < ip_end)
+		op = emit_literal(op, next_emit, ip_end - next_emit, false);
+
+	return op;
+}
+
+/*
+ * -----------------------------------------------------------------------
+ *  Lookup table for decompression code.  Generated by ComputeTable() below.
+ * -----------------------------------------------------------------------
+ */
+
+/* Mapping from i in range [0,4] to a mask to extract the bottom 8*i bits */
+static const u32 wordmask[] = {
+	0u, 0xffu, 0xffffu, 0xffffffu, 0xffffffffu
+};
+
+/*
+ * Data stored per entry in lookup table:
+ *       Range   Bits-used       Description
+ *      ------------------------------------
+ *      1..64   0..7            Literal/copy length encoded in opcode byte
+ *      0..7    8..10           Copy offset encoded in opcode byte / 256
+ *      0..4    11..13          Extra bytes after opcode
+ *
+ * We use eight bits for the length even though 7 would have sufficed
+ * because of efficiency reasons:
+ *      (1) Extracting a byte is faster than a bit-field
+ *      (2) It properly aligns copy offset so we do not need a <<8
+ */
+static const u16 char_table[256] = {
+	0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,
+	0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,
+	0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,
+	0x0007, 0x080a, 0x1007, 0x2007, 0x0008, 0x080b, 0x1008, 0x2008,
+	0x0009, 0x0904, 0x1009, 0x2009, 0x000a, 0x0905, 0x100a, 0x200a,
+	0x000b, 0x0906, 0x100b, 0x200b, 0x000c, 0x0907, 0x100c, 0x200c,
+	0x000d, 0x0908, 0x100d, 0x200d, 0x000e, 0x0909, 0x100e, 0x200e,
+	0x000f, 0x090a, 0x100f, 0x200f, 0x0010, 0x090b, 0x1010, 0x2010,
+	0x0011, 0x0a04, 0x1011, 0x2011, 0x0012, 0x0a05, 0x1012, 0x2012,
+	0x0013, 0x0a06, 0x1013, 0x2013, 0x0014, 0x0a07, 0x1014, 0x2014,
+	0x0015, 0x0a08, 0x1015, 0x2015, 0x0016, 0x0a09, 0x1016, 0x2016,
+	0x0017, 0x0a0a, 0x1017, 0x2017, 0x0018, 0x0a0b, 0x1018, 0x2018,
+	0x0019, 0x0b04, 0x1019, 0x2019, 0x001a, 0x0b05, 0x101a, 0x201a,
+	0x001b, 0x0b06, 0x101b, 0x201b, 0x001c, 0x0b07, 0x101c, 0x201c,
+	0x001d, 0x0b08, 0x101d, 0x201d, 0x001e, 0x0b09, 0x101e, 0x201e,
+	0x001f, 0x0b0a, 0x101f, 0x201f, 0x0020, 0x0b0b, 0x1020, 0x2020,
+	0x0021, 0x0c04, 0x1021, 0x2021, 0x0022, 0x0c05, 0x1022, 0x2022,
+	0x0023, 0x0c06, 0x1023, 0x2023, 0x0024, 0x0c07, 0x1024, 0x2024,
+	0x0025, 0x0c08, 0x1025, 0x2025, 0x0026, 0x0c09, 0x1026, 0x2026,
+	0x0027, 0x0c0a, 0x1027, 0x2027, 0x0028, 0x0c0b, 0x1028, 0x2028,
+	0x0029, 0x0d04, 0x1029, 0x2029, 0x002a, 0x0d05, 0x102a, 0x202a,
+	0x002b, 0x0d06, 0x102b, 0x202b, 0x002c, 0x0d07, 0x102c, 0x202c,
+	0x002d, 0x0d08, 0x102d, 0x202d, 0x002e, 0x0d09, 0x102e, 0x202e,
+	0x002f, 0x0d0a, 0x102f, 0x202f, 0x0030, 0x0d0b, 0x1030, 0x2030,
+	0x0031, 0x0e04, 0x1031, 0x2031, 0x0032, 0x0e05, 0x1032, 0x2032,
+	0x0033, 0x0e06, 0x1033, 0x2033, 0x0034, 0x0e07, 0x1034, 0x2034,
+	0x0035, 0x0e08, 0x1035, 0x2035, 0x0036, 0x0e09, 0x1036, 0x2036,
+	0x0037, 0x0e0a, 0x1037, 0x2037, 0x0038, 0x0e0b, 0x1038, 0x2038,
+	0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,
+	0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,
+	0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,
+	0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040
+};
+
+struct snappy_decompressor {
+	struct source *reader;	/* Underlying source of bytes to decompress */
+	const char *ip;		/* Points to next buffered byte */
+	const char *ip_limit;	/* Points just past buffered bytes */
+	u32 peeked;		/* Bytes peeked from reader (need to skip) */
+	bool eof;		/* Hit end of input without an error? */
+	char scratch[5];	/* Temporary buffer for peekfast boundaries */
+};
+
+static void
+init_snappy_decompressor(struct snappy_decompressor *d, struct source *reader)
+{
+	d->reader = reader;
+	d->ip = NULL;
+	d->ip_limit = NULL;
+	d->peeked = 0;
+	d->eof = false;
+}
+
+static void exit_snappy_decompressor(struct snappy_decompressor *d)
+{
+	skip(d->reader, d->peeked);
+}
+
+/*
+ * Read the uncompressed length stored at the start of the compressed data.
+ * On succcess, stores the length in *result and returns true.
+ * On failure, returns false.
+ */
+static bool read_uncompressed_length(struct snappy_decompressor *d,
+				     u32 * result)
+{
+	DCHECK(d->ip == NULL);	/*
+				 * Must not have read anything yet
+				 * Length is encoded in 1..5 bytes
+				 */
+	*result = 0;
+	u32 shift = 0;
+	while (true) {
+		if (shift >= 32)
+			return false;
+		size_t n;
+		const char *ip = peek(d->reader, &n);
+		if (n == 0)
+			return false;
+		const unsigned char c = *(const unsigned char *)(ip);
+		skip(d->reader, 1);
+		*result |= (u32) (c & 0x7f) << shift;
+		if (c < 128) {
+			break;
+		}
+		shift += 7;
+	}
+	return true;
+}
+
+static bool refill_tag(struct snappy_decompressor *d);
+
+/*
+ * Process the next item found in the input.
+ * Returns true if successful, false on error or end of input.
+ */
+static void decompress_all_tags(struct snappy_decompressor *d,
+				struct writer *writer)
+{
+	const char *ip = d->ip;
+
+	/*
+	 * We could have put this refill fragment only at the beginning of the loop.
+	 * However, duplicating it at the end of each branch gives the compiler more
+	 * scope to optimize the <ip_limit_ - ip> expression based on the local
+	 * context, which overall increases speed.
+	 */
+#define MAYBE_REFILL() \
+        if (d->ip_limit - ip < 5) {		\
+		d->ip = ip;			\
+		if (!refill_tag(d)) return;	\
+		ip = d->ip;			\
+        }
+
+
+	MAYBE_REFILL();
+	for (;;) {
+		if (d->ip_limit - ip < 5) {
+			d->ip = ip;
+			if (!refill_tag(d))
+				return;
+			ip = d->ip;
+		}
+
+		const unsigned char c = *(const unsigned char *)(ip++);
+
+		if ((c & 0x3) == LITERAL) {
+			u32 literal_length = (c >> 2) + 1;
+			if (writer_try_fast_append(writer, ip, d->ip_limit - ip, 
+						   literal_length)) {
+				DCHECK_LT(literal_length, 61);
+				ip += literal_length;
+				MAYBE_REFILL();
+				continue;
+			}
+			if (unlikely(literal_length >= 61)) {
+				/* Long literal */
+				const u32 literal_ll = literal_length - 60;
+				literal_length = (get_unaligned_le32(ip) &
+						  wordmask[literal_ll]) + 1;
+				ip += literal_ll;
+			}
+
+			u32 avail = d->ip_limit - ip;
+			while (avail < literal_length) {
+				if (!writer_append(writer, ip, avail))
+					return;
+				literal_length -= avail;
+				skip(d->reader, d->peeked);
+				size_t n;
+				ip = peek(d->reader, &n);
+				avail = n;
+				d->peeked = avail;
+				if (avail == 0)
+					return;	/* Premature end of input */
+				d->ip_limit = ip + avail;
+			}
+			if (!writer_append(writer, ip, literal_length))
+				return;
+			ip += literal_length;
+			MAYBE_REFILL();
+		} else {
+			const u32 entry = char_table[c];
+			const u32 trailer = get_unaligned_le32(ip) &
+				wordmask[entry >> 11];
+			const u32 length = entry & 0xff;
+			ip += entry >> 11;
+
+			/*
+			 * copy_offset/256 is encoded in bits 8..10.
+			 * By just fetching those bits, we get
+			 * copy_offset (since the bit-field starts at
+			 * bit 8).
+			 */
+			const u32 copy_offset = entry & 0x700;
+			if (!writer_append_from_self(writer,
+						     copy_offset + trailer,
+						     length))
+				return;
+			MAYBE_REFILL();
+		}
+	}
+}
+
+#undef MAYBE_REFILL
+
+static bool refill_tag(struct snappy_decompressor *d)
+{
+	const char *ip = d->ip;
+
+	if (ip == d->ip_limit) {
+		size_t n;
+		/* Fetch a new fragment from the reader */
+		skip(d->reader, d->peeked); /* All peeked bytes are used up */
+		ip = peek(d->reader, &n);
+		d->peeked = n;
+		if (n == 0) {
+			d->eof = true;
+			return false;
+		}
+		d->ip_limit = ip + n;
+	}
+
+	/* Read the tag character */
+	DCHECK_LT(ip, d->ip_limit);
+	const unsigned char c = *(const unsigned char *)(ip);
+	const u32 entry = char_table[c];
+	const u32 needed = (entry >> 11) + 1;	/* +1 byte for 'c' */
+	DCHECK_LE(needed, sizeof(d->scratch));
+
+	/* Read more bytes from reader if needed */
+	u32 nbuf = d->ip_limit - ip;
+
+	if (nbuf < needed) {
+		/*
+		 * Stitch together bytes from ip and reader to form the word
+		 * contents.  We store the needed bytes in "scratch".  They
+		 * will be consumed immediately by the caller since we do not
+		 * read more than we need.
+		 */
+		memmove(d->scratch, ip, nbuf);
+		skip(d->reader, d->peeked); /* All peeked bytes are used up */
+		d->peeked = 0;
+		while (nbuf < needed) {
+			size_t length;
+			const char *src = peek(d->reader, &length);
+			if (length == 0)
+				return false;
+			u32 to_add = min_t(u32, needed - nbuf, length);
+			memcpy(d->scratch + nbuf, src, to_add);
+			nbuf += to_add;
+			skip(d->reader, to_add);
+		}
+		DCHECK_EQ(nbuf, needed);
+		d->ip = d->scratch;
+		d->ip_limit = d->scratch + needed;
+	} else if (nbuf < 5) {
+		/*
+		 * Have enough bytes, but move into scratch so that we do not
+		 * read past end of input
+		 */
+		memmove(d->scratch, ip, nbuf);
+		skip(d->reader, d->peeked); /* All peeked bytes are used up */
+		d->peeked = 0;
+		d->ip = d->scratch;
+		d->ip_limit = d->scratch + nbuf;
+	} else {
+		/* Pass pointer to buffer returned by reader. */
+		d->ip = ip;
+	}
+	return true;
+}
+
+static int internal_uncompress(struct source *r,
+			       struct writer *writer, u32 max_len)
+{
+	struct snappy_decompressor decompressor;
+	u32 uncompressed_len = 0;
+
+	init_snappy_decompressor(&decompressor, r);
+
+	if (!read_uncompressed_length(&decompressor, &uncompressed_len))
+		return -EIO;
+	/* Protect against possible DoS attack */
+	if ((u64) (uncompressed_len) > max_len)
+		return -EIO;
+
+	writer_set_expected_length(writer, uncompressed_len);
+
+	/* Process the entire input */
+	decompress_all_tags(&decompressor, writer);
+
+	exit_snappy_decompressor(&decompressor);
+	if (decompressor.eof && writer_check_length(writer))
+		return 0;
+	return -EIO;
+}
+
+static inline int compress(struct snappy_env *env, struct source *reader,
+			   struct sink *writer)
+{
+	int err;
+	size_t written = 0;
+	int N = available(reader);
+	char ulength[kmax32];
+	char *p = varint_encode32(ulength, N);
+
+	append(writer, ulength, p - ulength);
+	written += (p - ulength);
+
+	while (N > 0) {
+		/* Get next block to compress (without copying if possible) */
+		size_t fragment_size;
+		const char *fragment = peek(reader, &fragment_size);
+		if (fragment_size == 0) {
+			err = -EIO;
+			goto out;
+		}
+		const unsigned num_to_read = min_t(int, N, kblock_size);
+		size_t bytes_read = fragment_size;
+
+		int pending_advance = 0;
+		if (bytes_read >= num_to_read) {
+			/* Buffer returned by reader is large enough */
+			pending_advance = num_to_read;
+			fragment_size = num_to_read;
+		}
+		else {
+			memcpy(env->scratch, fragment, bytes_read);
+			skip(reader, bytes_read);
+
+			while (bytes_read < num_to_read) {
+				fragment = peek(reader, &fragment_size);
+				size_t n =
+				    min_t(size_t, fragment_size,
+					  num_to_read - bytes_read);
+				memcpy((char *)(env->scratch) + bytes_read, fragment, n);
+				bytes_read += n;
+				skip(reader, n);
+			}
+			DCHECK_EQ(bytes_read, num_to_read);
+			fragment = env->scratch;
+			fragment_size = num_to_read;
+		}
+		if (fragment_size < num_to_read)
+			return -EIO;
+
+		/* Get encoding table for compression */
+		int table_size;
+		u16 *table = get_hash_table(env, num_to_read, &table_size);
+
+		/* Compress input_fragment and append to dest */
+		char *dest;
+		dest = sink_peek(writer, snappy_max_compressed_length(num_to_read));
+		if (!dest) {
+			/*
+			 * Need a scratch buffer for the output,
+			 * because the byte sink doesn't have enough
+			 * in one piece.
+			 */
+			dest = env->scratch_output;
+		}
+		char *end = compress_fragment(fragment, fragment_size,
+					      dest, table, table_size);
+		append(writer, dest, end - dest);
+		written += (end - dest);
+
+		N -= num_to_read;
+		skip(reader, pending_advance);
+	}
+
+	err = 0;
+out:
+	return err;
+}
+
+#ifdef SG
+
+int snappy_compress_iov(struct snappy_env *env,
+			struct iovec *iov_in,
+			int iov_in_len,
+			size_t input_length,
+			struct iovec *iov_out,
+			int *iov_out_len,
+			size_t *compressed_length)
+{
+	struct source reader = {
+		.iov = iov_in,
+		.iovlen = iov_in_len,
+		.total = input_length
+	};
+	struct sink writer = {
+		.iov = iov_out,
+		.iovlen = *iov_out_len,
+	};
+	int err = compress(env, &reader, &writer);
+
+	*iov_out_len = writer.curvec + 1;
+
+	/* Compute how many bytes were added */
+	*compressed_length = writer.written;
+	return err;
+}
+EXPORT_SYMBOL(snappy_compress_iov);
+
+/**
+ * snappy_compress - Compress a buffer using the snappy compressor.
+ * @env: Preallocated environment
+ * @input: Input buffer
+ * @input_length: Length of input_buffer
+ * @compressed: Output buffer for compressed data
+ * @compressed_length: The real length of the output written here.
+ *
+ * Return 0 on success, otherwise an negative error code.
+ *
+ * The output buffer must be at least
+ * snappy_max_compressed_length(input_length) bytes long.
+ *
+ * Requires a preallocated environment from snappy_init_env.
+ * The environment does not keep state over individual calls
+ * of this function, just preallocates the memory.
+ */
+int snappy_compress(struct snappy_env *env,
+		    const char *input,
+		    size_t input_length,
+		    char *compressed, size_t *compressed_length)
+{
+	struct iovec iov_in = {
+		.iov_base = (char *)input,
+		.iov_len = input_length,
+	};
+	struct iovec iov_out = {
+		.iov_base = compressed,
+		.iov_len = 0xffffffff,
+	};
+	int out = 1;
+	return snappy_compress_iov(env, 
+				   &iov_in, 1, input_length, 
+				   &iov_out, &out, compressed_length);
+}
+EXPORT_SYMBOL(snappy_compress);
+
+int snappy_uncompress_iov(struct iovec *iov_in, int iov_in_len,
+			   size_t input_len, char *uncompressed)
+{
+	struct source reader = {
+		.iov = iov_in,
+		.iovlen = iov_in_len,
+		.total = input_len
+	};
+	struct writer output = {
+		.base = uncompressed,
+		.op = uncompressed
+	};
+	return internal_uncompress(&reader, &output, 0xffffffff);
+}
+EXPORT_SYMBOL(snappy_uncompress_iov);
+
+/**
+ * snappy_uncompress - Uncompress a snappy compressed buffer
+ * @compressed: Input buffer with compressed data
+ * @n: length of compressed buffer
+ * @uncompressed: buffer for uncompressed data
+ *
+ * The uncompressed data buffer must be at least
+ * snappy_uncompressed_length(compressed) bytes long.
+ *
+ * Return 0 on success, otherwise an negative error code.
+ */
+int snappy_uncompress(const char *compressed, size_t n, char *uncompressed)
+{
+	struct iovec iov = {
+		.iov_base = (char *)compressed,
+		.iov_len = n
+	};
+	return snappy_uncompress_iov(&iov, 1, n, uncompressed);
+}
+EXPORT_SYMBOL(snappy_uncompress);
+
+#else
+/**
+ * snappy_compress - Compress a buffer using the snappy compressor.
+ * @env: Preallocated environment
+ * @input: Input buffer
+ * @input_length: Length of input_buffer
+ * @compressed: Output buffer for compressed data
+ * @compressed_length: The real length of the output written here.
+ *
+ * Return 0 on success, otherwise an negative error code.
+ *
+ * The output buffer must be at least
+ * snappy_max_compressed_length(input_length) bytes long.
+ *
+ * Requires a preallocated environment from snappy_init_env.
+ * The environment does not keep state over individual calls
+ * of this function, just preallocates the memory.
+ */
+int snappy_compress(struct snappy_env *env,
+		    const char *input,
+		    size_t input_length,
+		    char *compressed, size_t *compressed_length)
+{
+	struct source reader = {
+		.ptr = input,
+		.left = input_length
+	};
+	struct sink writer = {
+		.dest = compressed,
+	};
+	int err = compress(env, &reader, &writer);
+
+	/* Compute how many bytes were added */
+	*compressed_length = (writer.dest - compressed);
+	return err;
+}
+EXPORT_SYMBOL(snappy_compress);
+
+/**
+ * snappy_uncompress - Uncompress a snappy compressed buffer
+ * @compressed: Input buffer with compressed data
+ * @n: length of compressed buffer
+ * @uncompressed: buffer for uncompressed data
+ *
+ * The uncompressed data buffer must be at least
+ * snappy_uncompressed_length(compressed) bytes long.
+ *
+ * Return 0 on success, otherwise an negative error code.
+ */
+int snappy_uncompress(const char *compressed, size_t n, char *uncompressed)
+{
+	struct source reader = {
+		.ptr = compressed,
+		.left = n
+	};
+	struct writer output = {
+		.base = uncompressed,
+		.op = uncompressed
+	};
+	return internal_uncompress(&reader, &output, 0xffffffff);
+}
+EXPORT_SYMBOL(snappy_uncompress);
+#endif
+
+static inline void clear_env(struct snappy_env *env)
+{
+    memset(env, 0, sizeof(*env));
+}
+
+#ifdef SG
+/**
+ * snappy_init_env_sg - Allocate snappy compression environment
+ * @env: Environment to preallocate
+ * @sg: Input environment ever does scather gather
+ *
+ * If false is passed to sg then multiple entries in an iovec
+ * are not legal.
+ * Returns 0 on success, otherwise negative errno.
+ * Must run in process context.
+ */
+int snappy_init_env_sg(struct snappy_env *env, bool sg)
+{
+	if (snappy_init_env(env) < 0)
+		goto error;
+
+	if (sg) {
+		env->scratch = vmalloc(kblock_size);
+		if (!env->scratch)
+			goto error;
+		env->scratch_output =
+			vmalloc(snappy_max_compressed_length(kblock_size));
+		if (!env->scratch_output)
+			goto error;
+	}
+	return 0;
+error:
+	snappy_free_env(env);
+	return -ENOMEM;
+}
+EXPORT_SYMBOL(snappy_init_env_sg);
+#endif
+
+/**
+ * snappy_init_env - Allocate snappy compression environment
+ * @env: Environment to preallocate
+ *
+ * Passing multiple entries in an iovec is not allowed
+ * on the environment allocated here.
+ * Returns 0 on success, otherwise negative errno.
+ * Must run in process context.
+ */
+int snappy_init_env(struct snappy_env *env)
+{
+    clear_env(env);
+	env->hash_table = vmalloc(sizeof(u16) * kmax_hash_table_size);
+	if (!env->hash_table)
+		return -ENOMEM;
+	return 0;
+}
+EXPORT_SYMBOL(snappy_init_env);
+
+/**
+ * snappy_free_env - Free an snappy compression environment
+ * @env: Environment to free.
+ *
+ * Must run in process context.
+ */
+void snappy_free_env(struct snappy_env *env)
+{
+	vfree(env->hash_table);
+#ifdef SG
+	vfree(env->scratch);
+	vfree(env->scratch_output);
+#endif
+	clear_env(env);
+}
+EXPORT_SYMBOL(snappy_free_env);