Adding upstream version 5:7.2.4.upstream/5%7.2.4upstream

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

1 files changed, 2660 insertions, 0 deletions

diff --git a/src/listpack.c b/src/listpack.c
new file mode 100644
index 0000000..ecc7e9f
--- /dev/null
+++ b/src/listpack.c
@@ -0,0 +1,2660 @@
+/* Listpack -- A lists of strings serialization format
+ *
+ * This file implements the specification you can find at:
+ *
+ *  https://github.com/antirez/listpack
+ *
+ * Copyright (c) 2017, Salvatore Sanfilippo <antirez at gmail dot com>
+ * Copyright (c) 2020, Redis Labs, 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 Redis 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.
+ */
+
+#include <stdint.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "listpack.h"
+#include "listpack_malloc.h"
+#include "redisassert.h"
+#include "util.h"
+
+#define LP_HDR_SIZE 6       /* 32 bit total len + 16 bit number of elements. */
+#define LP_HDR_NUMELE_UNKNOWN UINT16_MAX
+#define LP_MAX_INT_ENCODING_LEN 9
+#define LP_MAX_BACKLEN_SIZE 5
+#define LP_ENCODING_INT 0
+#define LP_ENCODING_STRING 1
+
+#define LP_ENCODING_7BIT_UINT 0
+#define LP_ENCODING_7BIT_UINT_MASK 0x80
+#define LP_ENCODING_IS_7BIT_UINT(byte) (((byte)&LP_ENCODING_7BIT_UINT_MASK)==LP_ENCODING_7BIT_UINT)
+#define LP_ENCODING_7BIT_UINT_ENTRY_SIZE 2
+
+#define LP_ENCODING_6BIT_STR 0x80
+#define LP_ENCODING_6BIT_STR_MASK 0xC0
+#define LP_ENCODING_IS_6BIT_STR(byte) (((byte)&LP_ENCODING_6BIT_STR_MASK)==LP_ENCODING_6BIT_STR)
+
+#define LP_ENCODING_13BIT_INT 0xC0
+#define LP_ENCODING_13BIT_INT_MASK 0xE0
+#define LP_ENCODING_IS_13BIT_INT(byte) (((byte)&LP_ENCODING_13BIT_INT_MASK)==LP_ENCODING_13BIT_INT)
+#define LP_ENCODING_13BIT_INT_ENTRY_SIZE 3
+
+#define LP_ENCODING_12BIT_STR 0xE0
+#define LP_ENCODING_12BIT_STR_MASK 0xF0
+#define LP_ENCODING_IS_12BIT_STR(byte) (((byte)&LP_ENCODING_12BIT_STR_MASK)==LP_ENCODING_12BIT_STR)
+
+#define LP_ENCODING_16BIT_INT 0xF1
+#define LP_ENCODING_16BIT_INT_MASK 0xFF
+#define LP_ENCODING_IS_16BIT_INT(byte) (((byte)&LP_ENCODING_16BIT_INT_MASK)==LP_ENCODING_16BIT_INT)
+#define LP_ENCODING_16BIT_INT_ENTRY_SIZE 4
+
+#define LP_ENCODING_24BIT_INT 0xF2
+#define LP_ENCODING_24BIT_INT_MASK 0xFF
+#define LP_ENCODING_IS_24BIT_INT(byte) (((byte)&LP_ENCODING_24BIT_INT_MASK)==LP_ENCODING_24BIT_INT)
+#define LP_ENCODING_24BIT_INT_ENTRY_SIZE 5
+
+#define LP_ENCODING_32BIT_INT 0xF3
+#define LP_ENCODING_32BIT_INT_MASK 0xFF
+#define LP_ENCODING_IS_32BIT_INT(byte) (((byte)&LP_ENCODING_32BIT_INT_MASK)==LP_ENCODING_32BIT_INT)
+#define LP_ENCODING_32BIT_INT_ENTRY_SIZE 6
+
+#define LP_ENCODING_64BIT_INT 0xF4
+#define LP_ENCODING_64BIT_INT_MASK 0xFF
+#define LP_ENCODING_IS_64BIT_INT(byte) (((byte)&LP_ENCODING_64BIT_INT_MASK)==LP_ENCODING_64BIT_INT)
+#define LP_ENCODING_64BIT_INT_ENTRY_SIZE 10
+
+#define LP_ENCODING_32BIT_STR 0xF0
+#define LP_ENCODING_32BIT_STR_MASK 0xFF
+#define LP_ENCODING_IS_32BIT_STR(byte) (((byte)&LP_ENCODING_32BIT_STR_MASK)==LP_ENCODING_32BIT_STR)
+
+#define LP_EOF 0xFF
+
+#define LP_ENCODING_6BIT_STR_LEN(p) ((p)[0] & 0x3F)
+#define LP_ENCODING_12BIT_STR_LEN(p) ((((p)[0] & 0xF) << 8) | (p)[1])
+#define LP_ENCODING_32BIT_STR_LEN(p) (((uint32_t)(p)[1]<<0) | \
+                                      ((uint32_t)(p)[2]<<8) | \
+                                      ((uint32_t)(p)[3]<<16) | \
+                                      ((uint32_t)(p)[4]<<24))
+
+#define lpGetTotalBytes(p)           (((uint32_t)(p)[0]<<0) | \
+                                      ((uint32_t)(p)[1]<<8) | \
+                                      ((uint32_t)(p)[2]<<16) | \
+                                      ((uint32_t)(p)[3]<<24))
+
+#define lpGetNumElements(p)          (((uint32_t)(p)[4]<<0) | \
+                                      ((uint32_t)(p)[5]<<8))
+#define lpSetTotalBytes(p,v) do { \
+    (p)[0] = (v)&0xff; \
+    (p)[1] = ((v)>>8)&0xff; \
+    (p)[2] = ((v)>>16)&0xff; \
+    (p)[3] = ((v)>>24)&0xff; \
+} while(0)
+
+#define lpSetNumElements(p,v) do { \
+    (p)[4] = (v)&0xff; \
+    (p)[5] = ((v)>>8)&0xff; \
+} while(0)
+
+/* Validates that 'p' is not outside the listpack.
+ * All function that return a pointer to an element in the listpack will assert
+ * that this element is valid, so it can be freely used.
+ * Generally functions such lpNext and lpDelete assume the input pointer is
+ * already validated (since it's the return value of another function). */
+#define ASSERT_INTEGRITY(lp, p) do { \
+    assert((p) >= (lp)+LP_HDR_SIZE && (p) < (lp)+lpGetTotalBytes((lp))); \
+} while (0)
+
+/* Similar to the above, but validates the entire element length rather than just
+ * it's pointer. */
+#define ASSERT_INTEGRITY_LEN(lp, p, len) do { \
+    assert((p) >= (lp)+LP_HDR_SIZE && (p)+(len) < (lp)+lpGetTotalBytes((lp))); \
+} while (0)
+
+static inline void lpAssertValidEntry(unsigned char* lp, size_t lpbytes, unsigned char *p);
+
+/* Don't let listpacks grow over 1GB in any case, don't wanna risk overflow in
+ * Total Bytes header field */
+#define LISTPACK_MAX_SAFETY_SIZE (1<<30)
+int lpSafeToAdd(unsigned char* lp, size_t add) {
+    size_t len = lp? lpGetTotalBytes(lp): 0;
+    if (len + add > LISTPACK_MAX_SAFETY_SIZE)
+        return 0;
+    return 1;
+}
+
+/* Convert a string into a signed 64 bit integer.
+ * The function returns 1 if the string could be parsed into a (non-overflowing)
+ * signed 64 bit int, 0 otherwise. The 'value' will be set to the parsed value
+ * when the function returns success.
+ *
+ * Note that this function demands that the string strictly represents
+ * a int64 value: no spaces or other characters before or after the string
+ * representing the number are accepted, nor zeroes at the start if not
+ * for the string "0" representing the zero number.
+ *
+ * Because of its strictness, it is safe to use this function to check if
+ * you can convert a string into a long long, and obtain back the string
+ * from the number without any loss in the string representation. *
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * Credits: this function was adapted from the Redis source code, file
+ * "utils.c", function string2ll(), and is copyright:
+ *
+ * Copyright(C) 2011, Pieter Noordhuis
+ * Copyright(C) 2011, Salvatore Sanfilippo
+ *
+ * The function is released under the BSD 3-clause license.
+ */
+int lpStringToInt64(const char *s, unsigned long slen, int64_t *value) {
+    const char *p = s;
+    unsigned long plen = 0;
+    int negative = 0;
+    uint64_t v;
+
+    /* Abort if length indicates this cannot possibly be an int */
+    if (slen == 0 || slen >= LONG_STR_SIZE)
+        return 0;
+
+    /* Special case: first and only digit is 0. */
+    if (slen == 1 && p[0] == '0') {
+        if (value != NULL) *value = 0;
+        return 1;
+    }
+
+    if (p[0] == '-') {
+        negative = 1;
+        p++; plen++;
+
+        /* Abort on only a negative sign. */
+        if (plen == slen)
+            return 0;
+    }
+
+    /* First digit should be 1-9, otherwise the string should just be 0. */
+    if (p[0] >= '1' && p[0] <= '9') {
+        v = p[0]-'0';
+        p++; plen++;
+    } else {
+        return 0;
+    }
+
+    while (plen < slen && p[0] >= '0' && p[0] <= '9') {
+        if (v > (UINT64_MAX / 10)) /* Overflow. */
+            return 0;
+        v *= 10;
+
+        if (v > (UINT64_MAX - (p[0]-'0'))) /* Overflow. */
+            return 0;
+        v += p[0]-'0';
+
+        p++; plen++;
+    }
+
+    /* Return if not all bytes were used. */
+    if (plen < slen)
+        return 0;
+
+    if (negative) {
+        if (v > ((uint64_t)(-(INT64_MIN+1))+1)) /* Overflow. */
+            return 0;
+        if (value != NULL) *value = -v;
+    } else {
+        if (v > INT64_MAX) /* Overflow. */
+            return 0;
+        if (value != NULL) *value = v;
+    }
+    return 1;
+}
+
+/* Create a new, empty listpack.
+ * On success the new listpack is returned, otherwise an error is returned.
+ * Pre-allocate at least `capacity` bytes of memory,
+ * over-allocated memory can be shrunk by `lpShrinkToFit`.
+ * */
+unsigned char *lpNew(size_t capacity) {
+    unsigned char *lp = lp_malloc(capacity > LP_HDR_SIZE+1 ? capacity : LP_HDR_SIZE+1);
+    if (lp == NULL) return NULL;
+    lpSetTotalBytes(lp,LP_HDR_SIZE+1);
+    lpSetNumElements(lp,0);
+    lp[LP_HDR_SIZE] = LP_EOF;
+    return lp;
+}
+
+/* Free the specified listpack. */
+void lpFree(unsigned char *lp) {
+    lp_free(lp);
+}
+
+/* Shrink the memory to fit. */
+unsigned char* lpShrinkToFit(unsigned char *lp) {
+    size_t size = lpGetTotalBytes(lp);
+    if (size < lp_malloc_size(lp)) {
+        return lp_realloc(lp, size);
+    } else {
+        return lp;
+    }
+}
+
+/* Stores the integer encoded representation of 'v' in the 'intenc' buffer. */
+static inline void lpEncodeIntegerGetType(int64_t v, unsigned char *intenc, uint64_t *enclen) {
+    if (v >= 0 && v <= 127) {
+        /* Single byte 0-127 integer. */
+        intenc[0] = v;
+        *enclen = 1;
+    } else if (v >= -4096 && v <= 4095) {
+        /* 13 bit integer. */
+        if (v < 0) v = ((int64_t)1<<13)+v;
+        intenc[0] = (v>>8)|LP_ENCODING_13BIT_INT;
+        intenc[1] = v&0xff;
+        *enclen = 2;
+    } else if (v >= -32768 && v <= 32767) {
+        /* 16 bit integer. */
+        if (v < 0) v = ((int64_t)1<<16)+v;
+        intenc[0] = LP_ENCODING_16BIT_INT;
+        intenc[1] = v&0xff;
+        intenc[2] = v>>8;
+        *enclen = 3;
+    } else if (v >= -8388608 && v <= 8388607) {
+        /* 24 bit integer. */
+        if (v < 0) v = ((int64_t)1<<24)+v;
+        intenc[0] = LP_ENCODING_24BIT_INT;
+        intenc[1] = v&0xff;
+        intenc[2] = (v>>8)&0xff;
+        intenc[3] = v>>16;
+        *enclen = 4;
+    } else if (v >= -2147483648 && v <= 2147483647) {
+        /* 32 bit integer. */
+        if (v < 0) v = ((int64_t)1<<32)+v;
+        intenc[0] = LP_ENCODING_32BIT_INT;
+        intenc[1] = v&0xff;
+        intenc[2] = (v>>8)&0xff;
+        intenc[3] = (v>>16)&0xff;
+        intenc[4] = v>>24;
+        *enclen = 5;
+    } else {
+        /* 64 bit integer. */
+        uint64_t uv = v;
+        intenc[0] = LP_ENCODING_64BIT_INT;
+        intenc[1] = uv&0xff;
+        intenc[2] = (uv>>8)&0xff;
+        intenc[3] = (uv>>16)&0xff;
+        intenc[4] = (uv>>24)&0xff;
+        intenc[5] = (uv>>32)&0xff;
+        intenc[6] = (uv>>40)&0xff;
+        intenc[7] = (uv>>48)&0xff;
+        intenc[8] = uv>>56;
+        *enclen = 9;
+    }
+}
+
+/* Given an element 'ele' of size 'size', determine if the element can be
+ * represented inside the listpack encoded as integer, and returns
+ * LP_ENCODING_INT if so. Otherwise returns LP_ENCODING_STR if no integer
+ * encoding is possible.
+ *
+ * If the LP_ENCODING_INT is returned, the function stores the integer encoded
+ * representation of the element in the 'intenc' buffer.
+ *
+ * Regardless of the returned encoding, 'enclen' is populated by reference to
+ * the number of bytes that the string or integer encoded element will require
+ * in order to be represented. */
+static inline int lpEncodeGetType(unsigned char *ele, uint32_t size, unsigned char *intenc, uint64_t *enclen) {
+    int64_t v;
+    if (lpStringToInt64((const char*)ele, size, &v)) {
+        lpEncodeIntegerGetType(v, intenc, enclen);
+        return LP_ENCODING_INT;
+    } else {
+        if (size < 64) *enclen = 1+size;
+        else if (size < 4096) *enclen = 2+size;
+        else *enclen = 5+(uint64_t)size;
+        return LP_ENCODING_STRING;
+    }
+}
+
+/* Store a reverse-encoded variable length field, representing the length
+ * of the previous element of size 'l', in the target buffer 'buf'.
+ * The function returns the number of bytes used to encode it, from
+ * 1 to 5. If 'buf' is NULL the function just returns the number of bytes
+ * needed in order to encode the backlen. */
+static inline unsigned long lpEncodeBacklen(unsigned char *buf, uint64_t l) {
+    if (l <= 127) {
+        if (buf) buf[0] = l;
+        return 1;
+    } else if (l < 16383) {
+        if (buf) {
+            buf[0] = l>>7;
+            buf[1] = (l&127)|128;
+        }
+        return 2;
+    } else if (l < 2097151) {
+        if (buf) {
+            buf[0] = l>>14;
+            buf[1] = ((l>>7)&127)|128;
+            buf[2] = (l&127)|128;
+        }
+        return 3;
+    } else if (l < 268435455) {
+        if (buf) {
+            buf[0] = l>>21;
+            buf[1] = ((l>>14)&127)|128;
+            buf[2] = ((l>>7)&127)|128;
+            buf[3] = (l&127)|128;
+        }
+        return 4;
+    } else {
+        if (buf) {
+            buf[0] = l>>28;
+            buf[1] = ((l>>21)&127)|128;
+            buf[2] = ((l>>14)&127)|128;
+            buf[3] = ((l>>7)&127)|128;
+            buf[4] = (l&127)|128;
+        }
+        return 5;
+    }
+}
+
+/* Decode the backlen and returns it. If the encoding looks invalid (more than
+ * 5 bytes are used), UINT64_MAX is returned to report the problem. */
+static inline uint64_t lpDecodeBacklen(unsigned char *p) {
+    uint64_t val = 0;
+    uint64_t shift = 0;
+    do {
+        val |= (uint64_t)(p[0] & 127) << shift;
+        if (!(p[0] & 128)) break;
+        shift += 7;
+        p--;
+        if (shift > 28) return UINT64_MAX;
+    } while(1);
+    return val;
+}
+
+/* Encode the string element pointed by 's' of size 'len' in the target
+ * buffer 's'. The function should be called with 'buf' having always enough
+ * space for encoding the string. This is done by calling lpEncodeGetType()
+ * before calling this function. */
+static inline void lpEncodeString(unsigned char *buf, unsigned char *s, uint32_t len) {
+    if (len < 64) {
+        buf[0] = len | LP_ENCODING_6BIT_STR;
+        memcpy(buf+1,s,len);
+    } else if (len < 4096) {
+        buf[0] = (len >> 8) | LP_ENCODING_12BIT_STR;
+        buf[1] = len & 0xff;
+        memcpy(buf+2,s,len);
+    } else {
+        buf[0] = LP_ENCODING_32BIT_STR;
+        buf[1] = len & 0xff;
+        buf[2] = (len >> 8) & 0xff;
+        buf[3] = (len >> 16) & 0xff;
+        buf[4] = (len >> 24) & 0xff;
+        memcpy(buf+5,s,len);
+    }
+}
+
+/* Return the encoded length of the listpack element pointed by 'p'.
+ * This includes the encoding byte, length bytes, and the element data itself.
+ * If the element encoding is wrong then 0 is returned.
+ * Note that this method may access additional bytes (in case of 12 and 32 bit
+ * str), so should only be called when we know 'p' was already validated by
+ * lpCurrentEncodedSizeBytes or ASSERT_INTEGRITY_LEN (possibly since 'p' is
+ * a return value of another function that validated its return. */
+static inline uint32_t lpCurrentEncodedSizeUnsafe(unsigned char *p) {
+    if (LP_ENCODING_IS_7BIT_UINT(p[0])) return 1;
+    if (LP_ENCODING_IS_6BIT_STR(p[0])) return 1+LP_ENCODING_6BIT_STR_LEN(p);
+    if (LP_ENCODING_IS_13BIT_INT(p[0])) return 2;
+    if (LP_ENCODING_IS_16BIT_INT(p[0])) return 3;
+    if (LP_ENCODING_IS_24BIT_INT(p[0])) return 4;
+    if (LP_ENCODING_IS_32BIT_INT(p[0])) return 5;
+    if (LP_ENCODING_IS_64BIT_INT(p[0])) return 9;
+    if (LP_ENCODING_IS_12BIT_STR(p[0])) return 2+LP_ENCODING_12BIT_STR_LEN(p);
+    if (LP_ENCODING_IS_32BIT_STR(p[0])) return 5+LP_ENCODING_32BIT_STR_LEN(p);
+    if (p[0] == LP_EOF) return 1;
+    return 0;
+}
+
+/* Return bytes needed to encode the length of the listpack element pointed by 'p'.
+ * This includes just the encoding byte, and the bytes needed to encode the length
+ * of the element (excluding the element data itself)
+ * If the element encoding is wrong then 0 is returned. */
+static inline uint32_t lpCurrentEncodedSizeBytes(unsigned char *p) {
+    if (LP_ENCODING_IS_7BIT_UINT(p[0])) return 1;
+    if (LP_ENCODING_IS_6BIT_STR(p[0])) return 1;
+    if (LP_ENCODING_IS_13BIT_INT(p[0])) return 1;
+    if (LP_ENCODING_IS_16BIT_INT(p[0])) return 1;
+    if (LP_ENCODING_IS_24BIT_INT(p[0])) return 1;
+    if (LP_ENCODING_IS_32BIT_INT(p[0])) return 1;
+    if (LP_ENCODING_IS_64BIT_INT(p[0])) return 1;
+    if (LP_ENCODING_IS_12BIT_STR(p[0])) return 2;
+    if (LP_ENCODING_IS_32BIT_STR(p[0])) return 5;
+    if (p[0] == LP_EOF) return 1;
+    return 0;
+}
+
+/* Skip the current entry returning the next. It is invalid to call this
+ * function if the current element is the EOF element at the end of the
+ * listpack, however, while this function is used to implement lpNext(),
+ * it does not return NULL when the EOF element is encountered. */
+unsigned char *lpSkip(unsigned char *p) {
+    unsigned long entrylen = lpCurrentEncodedSizeUnsafe(p);
+    entrylen += lpEncodeBacklen(NULL,entrylen);
+    p += entrylen;
+    return p;
+}
+
+/* If 'p' points to an element of the listpack, calling lpNext() will return
+ * the pointer to the next element (the one on the right), or NULL if 'p'
+ * already pointed to the last element of the listpack. */
+unsigned char *lpNext(unsigned char *lp, unsigned char *p) {
+    assert(p);
+    p = lpSkip(p);
+    if (p[0] == LP_EOF) return NULL;
+    lpAssertValidEntry(lp, lpBytes(lp), p);
+    return p;
+}
+
+/* If 'p' points to an element of the listpack, calling lpPrev() will return
+ * the pointer to the previous element (the one on the left), or NULL if 'p'
+ * already pointed to the first element of the listpack. */
+unsigned char *lpPrev(unsigned char *lp, unsigned char *p) {
+    assert(p);
+    if (p-lp == LP_HDR_SIZE) return NULL;
+    p--; /* Seek the first backlen byte of the last element. */
+    uint64_t prevlen = lpDecodeBacklen(p);
+    prevlen += lpEncodeBacklen(NULL,prevlen);
+    p -= prevlen-1; /* Seek the first byte of the previous entry. */
+    lpAssertValidEntry(lp, lpBytes(lp), p);
+    return p;
+}
+
+/* Return a pointer to the first element of the listpack, or NULL if the
+ * listpack has no elements. */
+unsigned char *lpFirst(unsigned char *lp) {
+    unsigned char *p = lp + LP_HDR_SIZE; /* Skip the header. */
+    if (p[0] == LP_EOF) return NULL;
+    lpAssertValidEntry(lp, lpBytes(lp), p);
+    return p;
+}
+
+/* Return a pointer to the last element of the listpack, or NULL if the
+ * listpack has no elements. */
+unsigned char *lpLast(unsigned char *lp) {
+    unsigned char *p = lp+lpGetTotalBytes(lp)-1; /* Seek EOF element. */
+    return lpPrev(lp,p); /* Will return NULL if EOF is the only element. */
+}
+
+/* Return the number of elements inside the listpack. This function attempts
+ * to use the cached value when within range, otherwise a full scan is
+ * needed. As a side effect of calling this function, the listpack header
+ * could be modified, because if the count is found to be already within
+ * the 'numele' header field range, the new value is set. */
+unsigned long lpLength(unsigned char *lp) {
+    uint32_t numele = lpGetNumElements(lp);
+    if (numele != LP_HDR_NUMELE_UNKNOWN) return numele;
+
+    /* Too many elements inside the listpack. We need to scan in order
+     * to get the total number. */
+    uint32_t count = 0;
+    unsigned char *p = lpFirst(lp);
+    while(p) {
+        count++;
+        p = lpNext(lp,p);
+    }
+
+    /* If the count is again within range of the header numele field,
+     * set it. */
+    if (count < LP_HDR_NUMELE_UNKNOWN) lpSetNumElements(lp,count);
+    return count;
+}
+
+/* Return the listpack element pointed by 'p'.
+ *
+ * The function changes behavior depending on the passed 'intbuf' value.
+ * Specifically, if 'intbuf' is NULL:
+ *
+ * If the element is internally encoded as an integer, the function returns
+ * NULL and populates the integer value by reference in 'count'. Otherwise if
+ * the element is encoded as a string a pointer to the string (pointing inside
+ * the listpack itself) is returned, and 'count' is set to the length of the
+ * string.
+ *
+ * If instead 'intbuf' points to a buffer passed by the caller, that must be
+ * at least LP_INTBUF_SIZE bytes, the function always returns the element as
+ * it was a string (returning the pointer to the string and setting the
+ * 'count' argument to the string length by reference). However if the element
+ * is encoded as an integer, the 'intbuf' buffer is used in order to store
+ * the string representation.
+ *
+ * The user should use one or the other form depending on what the value will
+ * be used for. If there is immediate usage for an integer value returned
+ * by the function, than to pass a buffer (and convert it back to a number)
+ * is of course useless.
+ *
+ * If 'entry_size' is not NULL, *entry_size is set to the entry length of the
+ * listpack element pointed by 'p'. This includes the encoding bytes, length
+ * bytes, the element data itself, and the backlen bytes.
+ *
+ * If the function is called against a badly encoded ziplist, so that there
+ * is no valid way to parse it, the function returns like if there was an
+ * integer encoded with value 12345678900000000 + <unrecognized byte>, this may
+ * be an hint to understand that something is wrong. To crash in this case is
+ * not sensible because of the different requirements of the application using
+ * this lib.
+ *
+ * Similarly, there is no error returned since the listpack normally can be
+ * assumed to be valid, so that would be a very high API cost. */
+static inline unsigned char *lpGetWithSize(unsigned char *p, int64_t *count, unsigned char *intbuf, uint64_t *entry_size) {
+    int64_t val;
+    uint64_t uval, negstart, negmax;
+
+    assert(p); /* assertion for valgrind (avoid NPD) */
+    if (LP_ENCODING_IS_7BIT_UINT(p[0])) {
+        negstart = UINT64_MAX; /* 7 bit ints are always positive. */
+        negmax = 0;
+        uval = p[0] & 0x7f;
+        if (entry_size) *entry_size = LP_ENCODING_7BIT_UINT_ENTRY_SIZE;
+    } else if (LP_ENCODING_IS_6BIT_STR(p[0])) {
+        *count = LP_ENCODING_6BIT_STR_LEN(p);
+        if (entry_size) *entry_size = 1 + *count + lpEncodeBacklen(NULL, *count + 1);
+        return p+1;
+    } else if (LP_ENCODING_IS_13BIT_INT(p[0])) {
+        uval = ((p[0]&0x1f)<<8) | p[1];
+        negstart = (uint64_t)1<<12;
+        negmax = 8191;
+        if (entry_size) *entry_size = LP_ENCODING_13BIT_INT_ENTRY_SIZE;
+    } else if (LP_ENCODING_IS_16BIT_INT(p[0])) {
+        uval = (uint64_t)p[1] |
+               (uint64_t)p[2]<<8;
+        negstart = (uint64_t)1<<15;
+        negmax = UINT16_MAX;
+        if (entry_size) *entry_size = LP_ENCODING_16BIT_INT_ENTRY_SIZE;
+    } else if (LP_ENCODING_IS_24BIT_INT(p[0])) {
+        uval = (uint64_t)p[1] |
+               (uint64_t)p[2]<<8 |
+               (uint64_t)p[3]<<16;
+        negstart = (uint64_t)1<<23;
+        negmax = UINT32_MAX>>8;
+        if (entry_size) *entry_size = LP_ENCODING_24BIT_INT_ENTRY_SIZE;
+    } else if (LP_ENCODING_IS_32BIT_INT(p[0])) {
+        uval = (uint64_t)p[1] |
+               (uint64_t)p[2]<<8 |
+               (uint64_t)p[3]<<16 |
+               (uint64_t)p[4]<<24;
+        negstart = (uint64_t)1<<31;
+        negmax = UINT32_MAX;
+        if (entry_size) *entry_size = LP_ENCODING_32BIT_INT_ENTRY_SIZE;
+    } else if (LP_ENCODING_IS_64BIT_INT(p[0])) {
+        uval = (uint64_t)p[1] |
+               (uint64_t)p[2]<<8 |
+               (uint64_t)p[3]<<16 |
+               (uint64_t)p[4]<<24 |
+               (uint64_t)p[5]<<32 |
+               (uint64_t)p[6]<<40 |
+               (uint64_t)p[7]<<48 |
+               (uint64_t)p[8]<<56;
+        negstart = (uint64_t)1<<63;
+        negmax = UINT64_MAX;
+        if (entry_size) *entry_size = LP_ENCODING_64BIT_INT_ENTRY_SIZE;
+    } else if (LP_ENCODING_IS_12BIT_STR(p[0])) {
+        *count = LP_ENCODING_12BIT_STR_LEN(p);
+        if (entry_size) *entry_size = 2 + *count + lpEncodeBacklen(NULL, *count + 2);
+        return p+2;
+    } else if (LP_ENCODING_IS_32BIT_STR(p[0])) {
+        *count = LP_ENCODING_32BIT_STR_LEN(p);
+        if (entry_size) *entry_size = 5 + *count + lpEncodeBacklen(NULL, *count + 5);
+        return p+5;
+    } else {
+        uval = 12345678900000000ULL + p[0];
+        negstart = UINT64_MAX;
+        negmax = 0;
+    }
+
+    /* We reach this code path only for integer encodings.
+     * Convert the unsigned value to the signed one using two's complement
+     * rule. */
+    if (uval >= negstart) {
+        /* This three steps conversion should avoid undefined behaviors
+         * in the unsigned -> signed conversion. */
+        uval = negmax-uval;
+        val = uval;
+        val = -val-1;
+    } else {
+        val = uval;
+    }
+
+    /* Return the string representation of the integer or the value itself
+     * depending on intbuf being NULL or not. */
+    if (intbuf) {
+        *count = ll2string((char*)intbuf,LP_INTBUF_SIZE,(long long)val);
+        return intbuf;
+    } else {
+        *count = val;
+        return NULL;
+    }
+}
+
+unsigned char *lpGet(unsigned char *p, int64_t *count, unsigned char *intbuf) {
+    return lpGetWithSize(p, count, intbuf, NULL);
+}
+
+/* This is just a wrapper to lpGet() that is able to get entry value directly.
+ * When the function returns NULL, it populates the integer value by reference in 'lval'.
+ * Otherwise if the element is encoded as a string a pointer to the string (pointing
+ * inside the listpack itself) is returned, and 'slen' is set to the length of the
+ * string. */
+unsigned char *lpGetValue(unsigned char *p, unsigned int *slen, long long *lval) {
+    unsigned char *vstr;
+    int64_t ele_len;
+
+    vstr = lpGet(p, &ele_len, NULL);
+    if (vstr) {
+        *slen = ele_len;
+    } else {
+        *lval = ele_len;
+    }
+    return vstr;
+}
+
+/* Find pointer to the entry equal to the specified entry. Skip 'skip' entries
+ * between every comparison. Returns NULL when the field could not be found. */
+unsigned char *lpFind(unsigned char *lp, unsigned char *p, unsigned char *s, 
+                      uint32_t slen, unsigned int skip) {
+    int skipcnt = 0;
+    unsigned char vencoding = 0;
+    unsigned char *value;
+    int64_t ll, vll;
+    uint64_t entry_size = 123456789; /* initialized to avoid warning. */
+    uint32_t lp_bytes = lpBytes(lp);
+
+    assert(p);
+    while (p) {
+        if (skipcnt == 0) {
+            value = lpGetWithSize(p, &ll, NULL, &entry_size);
+            if (value) {
+                /* check the value doesn't reach outside the listpack before accessing it */
+                assert(p >= lp + LP_HDR_SIZE && p + entry_size < lp + lp_bytes);
+                if (slen == ll && memcmp(value, s, slen) == 0) {
+                    return p;
+                }
+            } else {
+                /* Find out if the searched field can be encoded. Note that
+                 * we do it only the first time, once done vencoding is set
+                 * to non-zero and vll is set to the integer value. */
+                if (vencoding == 0) {
+                    /* If the entry can be encoded as integer we set it to
+                     * 1, else set it to UCHAR_MAX, so that we don't retry
+                     * again the next time. */
+                    if (slen >= 32 || slen == 0 || !lpStringToInt64((const char*)s, slen, &vll)) {
+                        vencoding = UCHAR_MAX;
+                    } else {
+                        vencoding = 1;
+                    }
+                }
+
+                /* Compare current entry with specified entry, do it only
+                 * if vencoding != UCHAR_MAX because if there is no encoding
+                 * possible for the field it can't be a valid integer. */
+                if (vencoding != UCHAR_MAX && ll == vll) {
+                    return p;
+                }
+            }
+
+            /* Reset skip count */
+            skipcnt = skip;
+            p += entry_size;
+        } else {
+            /* Skip entry */
+            skipcnt--;
+
+            /* Move to next entry, avoid use `lpNext` due to `lpAssertValidEntry` in
+            * `lpNext` will call `lpBytes`, will cause performance degradation */
+            p = lpSkip(p);
+        }
+
+        /* The next call to lpGetWithSize could read at most 8 bytes past `p`
+         * We use the slower validation call only when necessary. */
+        if (p + 8 >= lp + lp_bytes)
+            lpAssertValidEntry(lp, lp_bytes, p);
+        else
+            assert(p >= lp + LP_HDR_SIZE && p < lp + lp_bytes);
+        if (p[0] == LP_EOF) break;
+    }
+
+    return NULL;
+}
+
+/* Insert, delete or replace the specified string element 'elestr' of length
+ * 'size' or integer element 'eleint' at the specified position 'p', with 'p'
+ * being a listpack element pointer obtained with lpFirst(), lpLast(), lpNext(),
+ * lpPrev() or lpSeek().
+ *
+ * The element is inserted before, after, or replaces the element pointed
+ * by 'p' depending on the 'where' argument, that can be LP_BEFORE, LP_AFTER
+ * or LP_REPLACE.
+ * 
+ * If both 'elestr' and `eleint` are NULL, the function removes the element
+ * pointed by 'p' instead of inserting one.
+ * If `eleint` is non-NULL, 'size' is the length of 'eleint', the function insert
+ * or replace with a 64 bit integer, which is stored in the 'eleint' buffer.
+ * If 'elestr` is non-NULL, 'size' is the length of 'elestr', the function insert
+ * or replace with a string, which is stored in the 'elestr' buffer.
+ * 
+ * Returns NULL on out of memory or when the listpack total length would exceed
+ * the max allowed size of 2^32-1, otherwise the new pointer to the listpack
+ * holding the new element is returned (and the old pointer passed is no longer
+ * considered valid)
+ *
+ * If 'newp' is not NULL, at the end of a successful call '*newp' will be set
+ * to the address of the element just added, so that it will be possible to
+ * continue an interaction with lpNext() and lpPrev().
+ *
+ * For deletion operations (both 'elestr' and 'eleint' set to NULL) 'newp' is
+ * set to the next element, on the right of the deleted one, or to NULL if the
+ * deleted element was the last one. */
+unsigned char *lpInsert(unsigned char *lp, unsigned char *elestr, unsigned char *eleint,
+                        uint32_t size, unsigned char *p, int where, unsigned char **newp)
+{
+    unsigned char intenc[LP_MAX_INT_ENCODING_LEN];
+    unsigned char backlen[LP_MAX_BACKLEN_SIZE];
+
+    uint64_t enclen; /* The length of the encoded element. */
+    int delete = (elestr == NULL && eleint == NULL);
+
+    /* when deletion, it is conceptually replacing the element with a
+     * zero-length element. So whatever we get passed as 'where', set
+     * it to LP_REPLACE. */
+    if (delete) where = LP_REPLACE;
+
+    /* If we need to insert after the current element, we just jump to the
+     * next element (that could be the EOF one) and handle the case of
+     * inserting before. So the function will actually deal with just two
+     * cases: LP_BEFORE and LP_REPLACE. */
+    if (where == LP_AFTER) {
+        p = lpSkip(p);
+        where = LP_BEFORE;
+        ASSERT_INTEGRITY(lp, p);
+    }
+
+    /* Store the offset of the element 'p', so that we can obtain its
+     * address again after a reallocation. */
+    unsigned long poff = p-lp;
+
+    int enctype;
+    if (elestr) {
+        /* Calling lpEncodeGetType() results into the encoded version of the
+        * element to be stored into 'intenc' in case it is representable as
+        * an integer: in that case, the function returns LP_ENCODING_INT.
+        * Otherwise if LP_ENCODING_STR is returned, we'll have to call
+        * lpEncodeString() to actually write the encoded string on place later.
+        *
+        * Whatever the returned encoding is, 'enclen' is populated with the
+        * length of the encoded element. */
+        enctype = lpEncodeGetType(elestr,size,intenc,&enclen);
+        if (enctype == LP_ENCODING_INT) eleint = intenc;
+    } else if (eleint) {
+        enctype = LP_ENCODING_INT;
+        enclen = size; /* 'size' is the length of the encoded integer element. */
+    } else {
+        enctype = -1;
+        enclen = 0;
+    }
+
+    /* We need to also encode the backward-parsable length of the element
+     * and append it to the end: this allows to traverse the listpack from
+     * the end to the start. */
+    unsigned long backlen_size = (!delete) ? lpEncodeBacklen(backlen,enclen) : 0;
+    uint64_t old_listpack_bytes = lpGetTotalBytes(lp);
+    uint32_t replaced_len  = 0;
+    if (where == LP_REPLACE) {
+        replaced_len = lpCurrentEncodedSizeUnsafe(p);
+        replaced_len += lpEncodeBacklen(NULL,replaced_len);
+        ASSERT_INTEGRITY_LEN(lp, p, replaced_len);
+    }
+
+    uint64_t new_listpack_bytes = old_listpack_bytes + enclen + backlen_size
+                                  - replaced_len;
+    if (new_listpack_bytes > UINT32_MAX) return NULL;
+
+    /* We now need to reallocate in order to make space or shrink the
+     * allocation (in case 'when' value is LP_REPLACE and the new element is
+     * smaller). However we do that before memmoving the memory to
+     * make room for the new element if the final allocation will get
+     * larger, or we do it after if the final allocation will get smaller. */
+
+    unsigned char *dst = lp + poff; /* May be updated after reallocation. */
+
+    /* Realloc before: we need more room. */
+    if (new_listpack_bytes > old_listpack_bytes &&
+        new_listpack_bytes > lp_malloc_size(lp)) {
+        if ((lp = lp_realloc(lp,new_listpack_bytes)) == NULL) return NULL;
+        dst = lp + poff;
+    }
+
+    /* Setup the listpack relocating the elements to make the exact room
+     * we need to store the new one. */
+    if (where == LP_BEFORE) {
+        memmove(dst+enclen+backlen_size,dst,old_listpack_bytes-poff);
+    } else { /* LP_REPLACE. */
+        memmove(dst+enclen+backlen_size,
+                dst+replaced_len,
+                old_listpack_bytes-poff-replaced_len);
+    }
+
+    /* Realloc after: we need to free space. */
+    if (new_listpack_bytes < old_listpack_bytes) {
+        if ((lp = lp_realloc(lp,new_listpack_bytes)) == NULL) return NULL;
+        dst = lp + poff;
+    }
+
+    /* Store the entry. */
+    if (newp) {
+        *newp = dst;
+        /* In case of deletion, set 'newp' to NULL if the next element is
+         * the EOF element. */
+        if (delete && dst[0] == LP_EOF) *newp = NULL;
+    }
+    if (!delete) {
+        if (enctype == LP_ENCODING_INT) {
+            memcpy(dst,eleint,enclen);
+        } else if (elestr) {
+            lpEncodeString(dst,elestr,size);
+        } else {
+            redis_unreachable();
+        }
+        dst += enclen;
+        memcpy(dst,backlen,backlen_size);
+        dst += backlen_size;
+    }
+
+    /* Update header. */
+    if (where != LP_REPLACE || delete) {
+        uint32_t num_elements = lpGetNumElements(lp);
+        if (num_elements != LP_HDR_NUMELE_UNKNOWN) {
+            if (!delete)
+                lpSetNumElements(lp,num_elements+1);
+            else
+                lpSetNumElements(lp,num_elements-1);
+        }
+    }
+    lpSetTotalBytes(lp,new_listpack_bytes);
+
+#if 0
+    /* This code path is normally disabled: what it does is to force listpack
+     * to return *always* a new pointer after performing some modification to
+     * the listpack, even if the previous allocation was enough. This is useful
+     * in order to spot bugs in code using listpacks: by doing so we can find
+     * if the caller forgets to set the new pointer where the listpack reference
+     * is stored, after an update. */
+    unsigned char *oldlp = lp;
+    lp = lp_malloc(new_listpack_bytes);
+    memcpy(lp,oldlp,new_listpack_bytes);
+    if (newp) {
+        unsigned long offset = (*newp)-oldlp;
+        *newp = lp + offset;
+    }
+    /* Make sure the old allocation contains garbage. */
+    memset(oldlp,'A',new_listpack_bytes);
+    lp_free(oldlp);
+#endif
+
+    return lp;
+}
+
+/* This is just a wrapper for lpInsert() to directly use a string. */
+unsigned char *lpInsertString(unsigned char *lp, unsigned char *s, uint32_t slen,
+                              unsigned char *p, int where, unsigned char **newp)
+{
+    return lpInsert(lp, s, NULL, slen, p, where, newp);
+}
+
+/* This is just a wrapper for lpInsert() to directly use a 64 bit integer
+ * instead of a string. */
+unsigned char *lpInsertInteger(unsigned char *lp, long long lval, unsigned char *p, int where, unsigned char **newp) {
+    uint64_t enclen; /* The length of the encoded element. */
+    unsigned char intenc[LP_MAX_INT_ENCODING_LEN];
+
+    lpEncodeIntegerGetType(lval, intenc, &enclen);
+    return lpInsert(lp, NULL, intenc, enclen, p, where, newp);
+}
+
+/* Append the specified element 's' of length 'slen' at the head of the listpack. */
+unsigned char *lpPrepend(unsigned char *lp, unsigned char *s, uint32_t slen) {
+    unsigned char *p = lpFirst(lp);
+    if (!p) return lpAppend(lp, s, slen);
+    return lpInsert(lp, s, NULL, slen, p, LP_BEFORE, NULL);
+}
+
+/* Append the specified integer element 'lval' at the head of the listpack. */
+unsigned char *lpPrependInteger(unsigned char *lp, long long lval) {
+    unsigned char *p = lpFirst(lp);
+    if (!p) return lpAppendInteger(lp, lval);
+    return lpInsertInteger(lp, lval, p, LP_BEFORE, NULL);
+}
+
+/* Append the specified element 'ele' of length 'size' at the end of the
+ * listpack. It is implemented in terms of lpInsert(), so the return value is
+ * the same as lpInsert(). */
+unsigned char *lpAppend(unsigned char *lp, unsigned char *ele, uint32_t size) {
+    uint64_t listpack_bytes = lpGetTotalBytes(lp);
+    unsigned char *eofptr = lp + listpack_bytes - 1;
+    return lpInsert(lp,ele,NULL,size,eofptr,LP_BEFORE,NULL);
+}
+
+/* Append the specified integer element 'lval' at the end of the listpack. */
+unsigned char *lpAppendInteger(unsigned char *lp, long long lval) {
+    uint64_t listpack_bytes = lpGetTotalBytes(lp);
+    unsigned char *eofptr = lp + listpack_bytes - 1;
+    return lpInsertInteger(lp, lval, eofptr, LP_BEFORE, NULL);
+}
+
+/* This is just a wrapper for lpInsert() to directly use a string to replace
+ * the current element. The function returns the new listpack as return
+ * value, and also updates the current cursor by updating '*p'. */
+unsigned char *lpReplace(unsigned char *lp, unsigned char **p, unsigned char *s, uint32_t slen) {
+    return lpInsert(lp, s, NULL, slen, *p, LP_REPLACE, p);
+}
+
+/* This is just a wrapper for lpInsertInteger() to directly use a 64 bit integer
+ * instead of a string to replace the current element. The function returns
+ * the new listpack as return value, and also updates the current cursor
+ * by updating '*p'. */
+unsigned char *lpReplaceInteger(unsigned char *lp, unsigned char **p, long long lval) {
+    return lpInsertInteger(lp, lval, *p, LP_REPLACE, p);
+}
+
+/* Remove the element pointed by 'p', and return the resulting listpack.
+ * If 'newp' is not NULL, the next element pointer (to the right of the
+ * deleted one) is returned by reference. If the deleted element was the
+ * last one, '*newp' is set to NULL. */
+unsigned char *lpDelete(unsigned char *lp, unsigned char *p, unsigned char **newp) {
+    return lpInsert(lp,NULL,NULL,0,p,LP_REPLACE,newp);
+}
+
+/* Delete a range of entries from the listpack start with the element pointed by 'p'. */
+unsigned char *lpDeleteRangeWithEntry(unsigned char *lp, unsigned char **p, unsigned long num) {
+    size_t bytes = lpBytes(lp);
+    unsigned long deleted = 0;
+    unsigned char *eofptr = lp + bytes - 1;
+    unsigned char *first, *tail;
+    first = tail = *p;
+
+    if (num == 0) return lp;  /* Nothing to delete, return ASAP. */
+
+    /* Find the next entry to the last entry that needs to be deleted.
+     * lpLength may be unreliable due to corrupt data, so we cannot
+     * treat 'num' as the number of elements to be deleted. */
+    while (num--) {
+        deleted++;
+        tail = lpSkip(tail);
+        if (tail[0] == LP_EOF) break;
+        lpAssertValidEntry(lp, bytes, tail);
+    }
+
+    /* Store the offset of the element 'first', so that we can obtain its
+     * address again after a reallocation. */
+    unsigned long poff = first-lp;
+
+    /* Move tail to the front of the listpack */
+    memmove(first, tail, eofptr - tail + 1);
+    lpSetTotalBytes(lp, bytes - (tail - first));
+    uint32_t numele = lpGetNumElements(lp);
+    if (numele != LP_HDR_NUMELE_UNKNOWN)
+        lpSetNumElements(lp, numele-deleted);
+    lp = lpShrinkToFit(lp);
+
+    /* Store the entry. */
+    *p = lp+poff;
+    if ((*p)[0] == LP_EOF) *p = NULL;
+
+    return lp;
+}
+
+/* Delete a range of entries from the listpack. */
+unsigned char *lpDeleteRange(unsigned char *lp, long index, unsigned long num) {
+    unsigned char *p;
+    uint32_t numele = lpGetNumElements(lp);
+
+    if (num == 0) return lp; /* Nothing to delete, return ASAP. */
+    if ((p = lpSeek(lp, index)) == NULL) return lp;
+
+    /* If we know we're gonna delete beyond the end of the listpack, we can just move
+     * the EOF marker, and there's no need to iterate through the entries,
+     * but if we can't be sure how many entries there are, we rather avoid calling lpLength
+     * since that means an additional iteration on all elements.
+     *
+     * Note that index could overflow, but we use the value after seek, so when we
+     * use it no overflow happens. */
+    if (numele != LP_HDR_NUMELE_UNKNOWN && index < 0) index = (long)numele + index;
+    if (numele != LP_HDR_NUMELE_UNKNOWN && (numele - (unsigned long)index) <= num) {
+        p[0] = LP_EOF;
+        lpSetTotalBytes(lp, p - lp + 1);
+        lpSetNumElements(lp, index);
+        lp = lpShrinkToFit(lp);
+    } else {
+        lp = lpDeleteRangeWithEntry(lp, &p, num);
+    }
+
+    return lp;
+}
+
+/* Delete the elements 'ps' passed as an array of 'count' element pointers and
+ * return the resulting listpack. The elements must be given in the same order
+ * as they apper in the listpack. */
+unsigned char *lpBatchDelete(unsigned char *lp, unsigned char **ps, unsigned long count) {
+    if (count == 0) return lp;
+    unsigned char *dst = ps[0];
+    size_t total_bytes = lpGetTotalBytes(lp);
+    unsigned char *lp_end = lp + total_bytes; /* After the EOF element. */
+    assert(lp_end[-1] == LP_EOF);
+    /*
+     * ----+--------+-----------+--------+---------+-----+---+
+     * ... | Delete | Keep      | Delete | Keep    | ... |EOF|
+     * ... |xxxxxxxx|           |xxxxxxxx|         | ... |   |
+     * ----+--------+-----------+--------+---------+-----+---+
+     *     ^        ^           ^                            ^
+     *     |        |           |                            |
+     *     ps[i]    |           ps[i+1]                      |
+     *     skip     keep_start  keep_end                     lp_end
+     *
+     * The loop memmoves the bytes between keep_start and keep_end to dst.
+     */
+    for (unsigned long i = 0; i < count; i++) {
+        unsigned char *skip = ps[i];
+        assert(skip != NULL && skip[0] != LP_EOF);
+        unsigned char *keep_start = lpSkip(skip);
+        unsigned char *keep_end;
+        if (i + 1 < count) {
+            keep_end = ps[i + 1];
+            /* Deleting consecutive elements. Nothing to keep between them. */
+            if (keep_start == keep_end) continue;
+        } else {
+            /* Keep the rest of the listpack including the EOF marker. */
+            keep_end = lp_end;
+        }
+        assert(keep_end > keep_start);
+        size_t bytes_to_keep = keep_end - keep_start;
+        memmove(dst, keep_start, bytes_to_keep);
+        dst += bytes_to_keep;
+    }
+    /* Update total size and num elements. */
+    size_t deleted_bytes = lp_end - dst;
+    total_bytes -= deleted_bytes;
+    assert(lp[total_bytes - 1] == LP_EOF);
+    lpSetTotalBytes(lp, total_bytes);
+    uint32_t numele = lpGetNumElements(lp);
+    if (numele != LP_HDR_NUMELE_UNKNOWN) lpSetNumElements(lp, numele - count);
+    return lpShrinkToFit(lp);
+}
+
+/* Merge listpacks 'first' and 'second' by appending 'second' to 'first'.
+ *
+ * NOTE: The larger listpack is reallocated to contain the new merged listpack.
+ * Either 'first' or 'second' can be used for the result.  The parameter not
+ * used will be free'd and set to NULL.
+ *
+ * After calling this function, the input parameters are no longer valid since
+ * they are changed and free'd in-place.
+ *
+ * The result listpack is the contents of 'first' followed by 'second'.
+ *
+ * On failure: returns NULL if the merge is impossible.
+ * On success: returns the merged listpack (which is expanded version of either
+ * 'first' or 'second', also frees the other unused input listpack, and sets the
+ * input listpack argument equal to newly reallocated listpack return value. */
+unsigned char *lpMerge(unsigned char **first, unsigned char **second) {
+    /* If any params are null, we can't merge, so NULL. */
+    if (first == NULL || *first == NULL || second == NULL || *second == NULL)
+        return NULL;
+
+    /* Can't merge same list into itself. */
+    if (*first == *second)
+        return NULL;
+
+    size_t first_bytes = lpBytes(*first);
+    unsigned long first_len = lpLength(*first);
+
+    size_t second_bytes = lpBytes(*second);
+    unsigned long second_len = lpLength(*second);
+
+    int append;
+    unsigned char *source, *target;
+    size_t target_bytes, source_bytes;
+    /* Pick the largest listpack so we can resize easily in-place.
+     * We must also track if we are now appending or prepending to
+     * the target listpack. */
+    if (first_bytes >= second_bytes) {
+        /* retain first, append second to first. */
+        target = *first;
+        target_bytes = first_bytes;
+        source = *second;
+        source_bytes = second_bytes;
+        append = 1;
+    } else {
+        /* else, retain second, prepend first to second. */
+        target = *second;
+        target_bytes = second_bytes;
+        source = *first;
+        source_bytes = first_bytes;
+        append = 0;
+    }
+
+    /* Calculate final bytes (subtract one pair of metadata) */
+    unsigned long long lpbytes = (unsigned long long)first_bytes + second_bytes - LP_HDR_SIZE - 1;
+    assert(lpbytes < UINT32_MAX); /* larger values can't be stored */
+    unsigned long lplength = first_len + second_len;
+
+    /* Combined lp length should be limited within UINT16_MAX */
+    lplength = lplength < UINT16_MAX ? lplength : UINT16_MAX;
+
+    /* Extend target to new lpbytes then append or prepend source. */
+    target = lp_realloc(target, lpbytes);
+    if (append) {
+        /* append == appending to target */
+        /* Copy source after target (copying over original [END]):
+         *   [TARGET - END, SOURCE - HEADER] */
+        memcpy(target + target_bytes - 1,
+               source + LP_HDR_SIZE,
+               source_bytes - LP_HDR_SIZE);
+    } else {
+        /* !append == prepending to target */
+        /* Move target *contents* exactly size of (source - [END]),
+         * then copy source into vacated space (source - [END]):
+         *   [SOURCE - END, TARGET - HEADER] */
+        memmove(target + source_bytes - 1,
+                target + LP_HDR_SIZE,
+                target_bytes - LP_HDR_SIZE);
+        memcpy(target, source, source_bytes - 1);
+    }
+
+    lpSetNumElements(target, lplength);
+    lpSetTotalBytes(target, lpbytes);
+
+    /* Now free and NULL out what we didn't realloc */
+    if (append) {
+        lp_free(*second);
+        *second = NULL;
+        *first = target;
+    } else {
+        lp_free(*first);
+        *first = NULL;
+        *second = target;
+    }
+
+    return target;
+}
+
+unsigned char *lpDup(unsigned char *lp) {
+    size_t lpbytes = lpBytes(lp);
+    unsigned char *newlp = lp_malloc(lpbytes);
+    memcpy(newlp, lp, lpbytes);
+    return newlp;
+}
+
+/* Return the total number of bytes the listpack is composed of. */
+size_t lpBytes(unsigned char *lp) {
+    return lpGetTotalBytes(lp);
+}
+
+/* Returns the size of a listpack consisting of an integer repeated 'rep' times. */
+size_t lpEstimateBytesRepeatedInteger(long long lval, unsigned long rep) {
+    uint64_t enclen;
+    unsigned char intenc[LP_MAX_INT_ENCODING_LEN];
+    lpEncodeIntegerGetType(lval, intenc, &enclen);
+    unsigned long backlen = lpEncodeBacklen(NULL, enclen);
+    return LP_HDR_SIZE + (enclen + backlen) * rep + 1;
+}
+
+/* Seek the specified element and returns the pointer to the seeked element.
+ * Positive indexes specify the zero-based element to seek from the head to
+ * the tail, negative indexes specify elements starting from the tail, where
+ * -1 means the last element, -2 the penultimate and so forth. If the index
+ * is out of range, NULL is returned. */
+unsigned char *lpSeek(unsigned char *lp, long index) {
+    int forward = 1; /* Seek forward by default. */
+
+    /* We want to seek from left to right or the other way around
+     * depending on the listpack length and the element position.
+     * However if the listpack length cannot be obtained in constant time,
+     * we always seek from left to right. */
+    uint32_t numele = lpGetNumElements(lp);
+    if (numele != LP_HDR_NUMELE_UNKNOWN) {
+        if (index < 0) index = (long)numele+index;
+        if (index < 0) return NULL; /* Index still < 0 means out of range. */
+        if (index >= (long)numele) return NULL; /* Out of range the other side. */
+        /* We want to scan right-to-left if the element we are looking for
+         * is past the half of the listpack. */
+        if (index > (long)numele/2) {
+            forward = 0;
+            /* Right to left scanning always expects a negative index. Convert
+             * our index to negative form. */
+            index -= numele;
+        }
+    } else {
+        /* If the listpack length is unspecified, for negative indexes we
+         * want to always scan right-to-left. */
+        if (index < 0) forward = 0;
+    }
+
+    /* Forward and backward scanning is trivially based on lpNext()/lpPrev(). */
+    if (forward) {
+        unsigned char *ele = lpFirst(lp);
+        while (index > 0 && ele) {
+            ele = lpNext(lp,ele);
+            index--;
+        }
+        return ele;
+    } else {
+        unsigned char *ele = lpLast(lp);
+        while (index < -1 && ele) {
+            ele = lpPrev(lp,ele);
+            index++;
+        }
+        return ele;
+    }
+}
+
+/* Same as lpFirst but without validation assert, to be used right before lpValidateNext. */
+unsigned char *lpValidateFirst(unsigned char *lp) {
+    unsigned char *p = lp + LP_HDR_SIZE; /* Skip the header. */
+    if (p[0] == LP_EOF) return NULL;
+    return p;
+}
+
+/* Validate the integrity of a single listpack entry and move to the next one.
+ * The input argument 'pp' is a reference to the current record and is advanced on exit.
+ * Returns 1 if valid, 0 if invalid. */
+int lpValidateNext(unsigned char *lp, unsigned char **pp, size_t lpbytes) {
+#define OUT_OF_RANGE(p) ( \
+        (p) < lp + LP_HDR_SIZE || \
+        (p) > lp + lpbytes - 1)
+    unsigned char *p = *pp;
+    if (!p)
+        return 0;
+
+    /* Before accessing p, make sure it's valid. */
+    if (OUT_OF_RANGE(p))
+        return 0;
+
+    if (*p == LP_EOF) {
+        *pp = NULL;
+        return 1;
+    }
+
+    /* check that we can read the encoded size */
+    uint32_t lenbytes = lpCurrentEncodedSizeBytes(p);
+    if (!lenbytes)
+        return 0;
+
+    /* make sure the encoded entry length doesn't reach outside the edge of the listpack */
+    if (OUT_OF_RANGE(p + lenbytes))
+        return 0;
+
+    /* get the entry length and encoded backlen. */
+    unsigned long entrylen = lpCurrentEncodedSizeUnsafe(p);
+    unsigned long encodedBacklen = lpEncodeBacklen(NULL,entrylen);
+    entrylen += encodedBacklen;
+
+    /* make sure the entry doesn't reach outside the edge of the listpack */
+    if (OUT_OF_RANGE(p + entrylen))
+        return 0;
+
+    /* move to the next entry */
+    p += entrylen;
+
+    /* make sure the encoded length at the end patches the one at the beginning. */
+    uint64_t prevlen = lpDecodeBacklen(p-1);
+    if (prevlen + encodedBacklen != entrylen)
+        return 0;
+
+    *pp = p;
+    return 1;
+#undef OUT_OF_RANGE
+}
+
+/* Validate that the entry doesn't reach outside the listpack allocation. */
+static inline void lpAssertValidEntry(unsigned char* lp, size_t lpbytes, unsigned char *p) {
+    assert(lpValidateNext(lp, &p, lpbytes));
+}
+
+/* Validate the integrity of the data structure.
+ * when `deep` is 0, only the integrity of the header is validated.
+ * when `deep` is 1, we scan all the entries one by one. */
+int lpValidateIntegrity(unsigned char *lp, size_t size, int deep, 
+                        listpackValidateEntryCB entry_cb, void *cb_userdata) {
+    /* Check that we can actually read the header. (and EOF) */
+    if (size < LP_HDR_SIZE + 1)
+        return 0;
+
+    /* Check that the encoded size in the header must match the allocated size. */
+    size_t bytes = lpGetTotalBytes(lp);
+    if (bytes != size)
+        return 0;
+
+    /* The last byte must be the terminator. */
+    if (lp[size-1] != LP_EOF)
+        return 0;
+
+    if (!deep)
+        return 1;
+
+    /* Validate the individual entries. */
+    uint32_t count = 0;
+    uint32_t numele = lpGetNumElements(lp);
+    unsigned char *p = lp + LP_HDR_SIZE;
+    while(p && p[0] != LP_EOF) {
+        unsigned char *prev = p;
+
+        /* Validate this entry and move to the next entry in advance
+         * to avoid callback crash due to corrupt listpack. */
+        if (!lpValidateNext(lp, &p, bytes))
+            return 0;
+
+        /* Optionally let the caller validate the entry too. */
+        if (entry_cb && !entry_cb(prev, numele, cb_userdata))
+            return 0;
+
+        count++;
+    }
+
+    /* Make sure 'p' really does point to the end of the listpack. */
+    if (p != lp + size - 1)
+        return 0;
+
+    /* Check that the count in the header is correct */
+    if (numele != LP_HDR_NUMELE_UNKNOWN && numele != count)
+        return 0;
+
+    return 1;
+}
+
+/* Compare entry pointer to by 'p' with string 's' of length 'slen'.
+ * Return 1 if equal. */
+unsigned int lpCompare(unsigned char *p, unsigned char *s, uint32_t slen) {
+    unsigned char *value;
+    int64_t sz;
+    if (p[0] == LP_EOF) return 0;
+
+    value = lpGet(p, &sz, NULL);
+    if (value) {
+        return (slen == sz) && memcmp(value,s,slen) == 0;
+    } else {
+        /* We use lpStringToInt64() to get an integer representation of the
+         * string 's' and compare it to 'sval', it's much faster than convert
+         * integer to string and comparing. */
+        int64_t sval;
+        if (lpStringToInt64((const char*)s, slen, &sval))
+            return sz == sval;
+    }
+
+    return 0;
+}
+
+/* uint compare for qsort */
+static int uintCompare(const void *a, const void *b) {
+    return (*(unsigned int *) a - *(unsigned int *) b);
+}
+
+/* Helper method to store a string into from val or lval into dest */
+static inline void lpSaveValue(unsigned char *val, unsigned int len, int64_t lval, listpackEntry *dest) {
+    dest->sval = val;
+    dest->slen = len;
+    dest->lval = lval;
+}
+
+/* Randomly select a pair of key and value.
+ * total_count is a pre-computed length/2 of the listpack (to avoid calls to lpLength)
+ * 'key' and 'val' are used to store the result key value pair.
+ * 'val' can be NULL if the value is not needed. */
+void lpRandomPair(unsigned char *lp, unsigned long total_count, listpackEntry *key, listpackEntry *val) {
+    unsigned char *p;
+
+    /* Avoid div by zero on corrupt listpack */
+    assert(total_count);
+
+    /* Generate even numbers, because listpack saved K-V pair */
+    int r = (rand() % total_count) * 2;
+    assert((p = lpSeek(lp, r)));
+    key->sval = lpGetValue(p, &(key->slen), &(key->lval));
+
+    if (!val)
+        return;
+    assert((p = lpNext(lp, p)));
+    val->sval = lpGetValue(p, &(val->slen), &(val->lval));
+}
+
+/* Randomly select 'count' entries and store them in the 'entries' array, which
+ * needs to have space for 'count' listpackEntry structs. The order is random
+ * and duplicates are possible. */
+void lpRandomEntries(unsigned char *lp, unsigned int count, listpackEntry *entries) {
+    struct pick {
+        unsigned int index;
+        unsigned int order;
+    } *picks = lp_malloc(count * sizeof(struct pick));
+    unsigned int total_size = lpLength(lp);
+    assert(total_size);
+    for (unsigned int i = 0; i < count; i++) {
+        picks[i].index = rand() % total_size;
+        picks[i].order = i;
+    }
+
+    /* Sort by index. */
+    qsort(picks, count, sizeof(struct pick), uintCompare);
+
+    /* Iterate over listpack in index order and store the values in the entries
+     * array respecting the original order. */
+    unsigned char *p = lpFirst(lp);
+    unsigned int j = 0; /* index in listpack */
+    for (unsigned int i = 0; i < count; i++) {
+        /* Advance listpack pointer to until we reach 'index' listpack. */
+        while (j < picks[i].index) {
+            p = lpNext(lp, p);
+            j++;
+        }
+        int storeorder = picks[i].order;
+        unsigned int len = 0;
+        long long llval = 0;
+        unsigned char *str = lpGetValue(p, &len, &llval);
+        lpSaveValue(str, len, llval, &entries[storeorder]);
+    }
+    lp_free(picks);
+}
+
+/* Randomly select count of key value pairs and store into 'keys' and
+ * 'vals' args. The order of the picked entries is random, and the selections
+ * are non-unique (repetitions are possible).
+ * The 'vals' arg can be NULL in which case we skip these. */
+void lpRandomPairs(unsigned char *lp, unsigned int count, listpackEntry *keys, listpackEntry *vals) {
+    unsigned char *p, *key, *value;
+    unsigned int klen = 0, vlen = 0;
+    long long klval = 0, vlval = 0;
+
+    /* Notice: the index member must be first due to the use in uintCompare */
+    typedef struct {
+        unsigned int index;
+        unsigned int order;
+    } rand_pick;
+    rand_pick *picks = lp_malloc(sizeof(rand_pick)*count);
+    unsigned int total_size = lpLength(lp)/2;
+
+    /* Avoid div by zero on corrupt listpack */
+    assert(total_size);
+
+    /* create a pool of random indexes (some may be duplicate). */
+    for (unsigned int i = 0; i < count; i++) {
+        picks[i].index = (rand() % total_size) * 2; /* Generate even indexes */
+        /* keep track of the order we picked them */
+        picks[i].order = i;
+    }
+
+    /* sort by indexes. */
+    qsort(picks, count, sizeof(rand_pick), uintCompare);
+
+    /* fetch the elements form the listpack into a output array respecting the original order. */
+    unsigned int lpindex = picks[0].index, pickindex = 0;
+    p = lpSeek(lp, lpindex);
+    while (p && pickindex < count) {
+        key = lpGetValue(p, &klen, &klval);
+        assert((p = lpNext(lp, p)));
+        value = lpGetValue(p, &vlen, &vlval);
+        while (pickindex < count && lpindex == picks[pickindex].index) {
+            int storeorder = picks[pickindex].order;
+            lpSaveValue(key, klen, klval, &keys[storeorder]);
+            if (vals)
+                lpSaveValue(value, vlen, vlval, &vals[storeorder]);
+             pickindex++;
+        }
+        lpindex += 2;
+        p = lpNext(lp, p);
+    }
+
+    lp_free(picks);
+}
+
+/* Randomly select count of key value pairs and store into 'keys' and
+ * 'vals' args. The selections are unique (no repetitions), and the order of
+ * the picked entries is NOT-random.
+ * The 'vals' arg can be NULL in which case we skip these.
+ * The return value is the number of items picked which can be lower than the
+ * requested count if the listpack doesn't hold enough pairs. */
+unsigned int lpRandomPairsUnique(unsigned char *lp, unsigned int count, listpackEntry *keys, listpackEntry *vals) {
+    unsigned char *p, *key;
+    unsigned int klen = 0;
+    long long klval = 0;
+    unsigned int total_size = lpLength(lp)/2;
+    unsigned int index = 0;
+    if (count > total_size)
+        count = total_size;
+
+    p = lpFirst(lp);
+    unsigned int picked = 0, remaining = count;
+    while (picked < count && p) {
+        assert((p = lpNextRandom(lp, p, &index, remaining, 1)));
+        key = lpGetValue(p, &klen, &klval);
+        lpSaveValue(key, klen, klval, &keys[picked]);
+        assert((p = lpNext(lp, p)));
+        index++;
+        if (vals) {
+            key = lpGetValue(p, &klen, &klval);
+            lpSaveValue(key, klen, klval, &vals[picked]);
+        }
+        p = lpNext(lp, p);
+        remaining--;
+        picked++;
+        index++;
+    }
+    return picked;
+}
+
+/* Iterates forward to the "next random" element, given we are yet to pick
+ * 'remaining' unique elements between the starting element 'p' (inclusive) and
+ * the end of the list. The 'index' needs to be initialized according to the
+ * current zero-based index matching the position of the starting element 'p'
+ * and is updated to match the returned element's zero-based index. If
+ * 'even_only' is nonzero, an element with an even index is picked, which is
+ * useful if the listpack represents a key-value pair sequence.
+ *
+ * Note that this function can return p. In order to skip the previously
+ * returned element, you need to call lpNext() or lpDelete() after each call to
+ * lpNextRandom(). Idea:
+ *
+ *     assert(remaining <= lpLength(lp));
+ *     p = lpFirst(lp);
+ *     i = 0;
+ *     while (remaining > 0) {
+ *         p = lpNextRandom(lp, p, &i, remaining--, 0);
+ *
+ *         // ... Do stuff with p ...
+ *
+ *         p = lpNext(lp, p);
+ *         i++;
+ *     }
+ */
+unsigned char *lpNextRandom(unsigned char *lp, unsigned char *p, unsigned int *index,
+                            unsigned int remaining, int even_only)
+{
+    /* To only iterate once, every time we try to pick a member, the probability
+     * we pick it is the quotient of the count left we want to pick and the
+     * count still we haven't visited. This way, we could make every member be
+     * equally likely to be picked. */
+    unsigned int i = *index;
+    unsigned int total_size = lpLength(lp);
+    while (i < total_size && p != NULL) {
+        if (even_only && i % 2 != 0) {
+            p = lpNext(lp, p);
+            i++;
+            continue;
+        }
+
+        /* Do we pick this element? */
+        unsigned int available = total_size - i;
+        if (even_only) available /= 2;
+        double randomDouble = ((double)rand()) / RAND_MAX;
+        double threshold = ((double)remaining) / available;
+        if (randomDouble <= threshold) {
+            *index = i;
+            return p;
+        }
+
+        p = lpNext(lp, p);
+        i++;
+    }
+
+    return NULL;
+}
+
+/* Print info of listpack which is used in debugCommand */
+void lpRepr(unsigned char *lp) {
+    unsigned char *p, *vstr;
+    int64_t vlen;
+    unsigned char intbuf[LP_INTBUF_SIZE];
+    int index = 0;
+
+    printf("{total bytes %zu} {num entries %lu}\n", lpBytes(lp), lpLength(lp));
+        
+    p = lpFirst(lp);
+    while(p) {
+        uint32_t encoded_size_bytes = lpCurrentEncodedSizeBytes(p);
+        uint32_t encoded_size = lpCurrentEncodedSizeUnsafe(p);
+        unsigned long back_len = lpEncodeBacklen(NULL, encoded_size);
+        printf(
+            "{\n"
+                "\taddr: 0x%08lx,\n"
+                "\tindex: %2d,\n"
+                "\toffset: %1lu,\n"
+                "\thdr+entrylen+backlen: %2lu,\n"
+                "\thdrlen: %3u,\n"
+                "\tbacklen: %2lu,\n"
+                "\tpayload: %1u\n",
+            (long unsigned)p,
+            index,
+            (unsigned long) (p-lp),
+            encoded_size + back_len,
+            encoded_size_bytes,
+            back_len,
+            encoded_size - encoded_size_bytes);
+        printf("\tbytes: ");
+        for (unsigned int i = 0; i < (encoded_size + back_len); i++) {
+            printf("%02x|",p[i]);
+        }
+        printf("\n");
+
+        vstr = lpGet(p, &vlen, intbuf);
+        printf("\t[str]");
+        if (vlen > 40) {
+            if (fwrite(vstr, 40, 1, stdout) == 0) perror("fwrite");
+            printf("...");
+        } else {
+            if (fwrite(vstr, vlen, 1, stdout) == 0) perror("fwrite");
+        }
+        printf("\n}\n");
+        index++;
+        p = lpNext(lp, p);
+    }
+    printf("{end}\n\n");
+}
+
+#ifdef REDIS_TEST
+
+#include <sys/time.h>
+#include "adlist.h"
+#include "sds.h"
+#include "testhelp.h"
+
+#define UNUSED(x) (void)(x)
+#define TEST(name) printf("test — %s\n", name);
+
+char *mixlist[] = {"hello", "foo", "quux", "1024"};
+char *intlist[] = {"4294967296", "-100", "100", "128000", 
+                   "non integer", "much much longer non integer"};
+
+static unsigned char *createList(void) {
+    unsigned char *lp = lpNew(0);
+    lp = lpAppend(lp, (unsigned char*)mixlist[1], strlen(mixlist[1]));
+    lp = lpAppend(lp, (unsigned char*)mixlist[2], strlen(mixlist[2]));
+    lp = lpPrepend(lp, (unsigned char*)mixlist[0], strlen(mixlist[0]));
+    lp = lpAppend(lp, (unsigned char*)mixlist[3], strlen(mixlist[3]));
+    return lp;
+}
+
+static unsigned char *createIntList(void) {
+    unsigned char *lp = lpNew(0);
+    lp = lpAppend(lp, (unsigned char*)intlist[2], strlen(intlist[2]));
+    lp = lpAppend(lp, (unsigned char*)intlist[3], strlen(intlist[3]));
+    lp = lpPrepend(lp, (unsigned char*)intlist[1], strlen(intlist[1]));
+    lp = lpPrepend(lp, (unsigned char*)intlist[0], strlen(intlist[0]));
+    lp = lpAppend(lp, (unsigned char*)intlist[4], strlen(intlist[4]));
+    lp = lpAppend(lp, (unsigned char*)intlist[5], strlen(intlist[5]));
+    return lp;
+}
+
+static long long usec(void) {
+    struct timeval tv;
+    gettimeofday(&tv, NULL);
+    return (((long long)tv.tv_sec)*1000000)+tv.tv_usec;
+}
+
+static void stress(int pos, int num, int maxsize, int dnum) {
+    int i, j, k;
+    unsigned char *lp;
+    char posstr[2][5] = { "HEAD", "TAIL" };
+    long long start;
+    for (i = 0; i < maxsize; i+=dnum) {
+        lp = lpNew(0);
+        for (j = 0; j < i; j++) {
+            lp = lpAppend(lp, (unsigned char*)"quux", 4);
+        }
+
+        /* Do num times a push+pop from pos */
+        start = usec();
+        for (k = 0; k < num; k++) {
+            if (pos == 0) {
+                lp = lpPrepend(lp, (unsigned char*)"quux", 4);
+            } else {
+                lp = lpAppend(lp, (unsigned char*)"quux", 4);
+
+            }
+            lp = lpDelete(lp, lpFirst(lp), NULL);
+        }
+        printf("List size: %8d, bytes: %8zu, %dx push+pop (%s): %6lld usec\n",
+               i, lpBytes(lp), num, posstr[pos], usec()-start);
+        lpFree(lp);
+    }
+}
+
+static unsigned char *pop(unsigned char *lp, int where) {
+    unsigned char *p, *vstr;
+    int64_t vlen;
+
+    p = lpSeek(lp, where == 0 ? 0 : -1);
+    vstr = lpGet(p, &vlen, NULL);
+    if (where == 0)
+        printf("Pop head: ");
+    else
+        printf("Pop tail: ");
+
+    if (vstr) {
+        if (vlen && fwrite(vstr, vlen, 1, stdout) == 0) perror("fwrite");
+    } else {
+        printf("%lld", (long long)vlen);
+    }
+
+    printf("\n");
+    return lpDelete(lp, p, &p);
+}
+
+static int randstring(char *target, unsigned int min, unsigned int max) {
+    int p = 0;
+    int len = min+rand()%(max-min+1);
+    int minval, maxval;
+    switch(rand() % 3) {
+    case 0:
+        minval = 0;
+        maxval = 255;
+    break;
+    case 1:
+        minval = 48;
+        maxval = 122;
+    break;
+    case 2:
+        minval = 48;
+        maxval = 52;
+    break;
+    default:
+        assert(NULL);
+    }
+
+    while(p < len)
+        target[p++] = minval+rand()%(maxval-minval+1);
+    return len;
+}
+
+static void verifyEntry(unsigned char *p, unsigned char *s, size_t slen) {
+    assert(lpCompare(p, s, slen));
+}
+
+static int lpValidation(unsigned char *p, unsigned int head_count, void *userdata) {
+    UNUSED(p);
+    UNUSED(head_count);
+
+    int ret;
+    long *count = userdata;
+    ret = lpCompare(p, (unsigned char *)mixlist[*count], strlen(mixlist[*count]));
+    (*count)++;
+    return ret;
+}
+
+int listpackTest(int argc, char *argv[], int flags) {
+    UNUSED(argc);
+    UNUSED(argv);
+
+    int i;
+    unsigned char *lp, *p, *vstr;
+    int64_t vlen;
+    unsigned char intbuf[LP_INTBUF_SIZE];
+    int accurate = (flags & REDIS_TEST_ACCURATE);
+
+    TEST("Create int list") {
+        lp = createIntList();
+        assert(lpLength(lp) == 6);
+        lpFree(lp);
+    }
+
+    TEST("Create list") {
+        lp = createList();
+        assert(lpLength(lp) == 4);
+        lpFree(lp);
+    }
+
+    TEST("Test lpPrepend") {
+        lp = lpNew(0);
+        lp = lpPrepend(lp, (unsigned char*)"abc", 3);
+        lp = lpPrepend(lp, (unsigned char*)"1024", 4);
+        verifyEntry(lpSeek(lp, 0), (unsigned char*)"1024", 4);
+        verifyEntry(lpSeek(lp, 1), (unsigned char*)"abc", 3);
+        lpFree(lp);
+    }
+
+    TEST("Test lpPrependInteger") {
+        lp = lpNew(0);
+        lp = lpPrependInteger(lp, 127);
+        lp = lpPrependInteger(lp, 4095);
+        lp = lpPrependInteger(lp, 32767);
+        lp = lpPrependInteger(lp, 8388607);
+        lp = lpPrependInteger(lp, 2147483647);
+        lp = lpPrependInteger(lp, 9223372036854775807);
+        verifyEntry(lpSeek(lp, 0), (unsigned char*)"9223372036854775807", 19);
+        verifyEntry(lpSeek(lp, -1), (unsigned char*)"127", 3);
+        lpFree(lp);
+    }
+
+    TEST("Get element at index") {
+        lp = createList();
+        verifyEntry(lpSeek(lp, 0), (unsigned char*)"hello", 5);
+        verifyEntry(lpSeek(lp, 3), (unsigned char*)"1024", 4);
+        verifyEntry(lpSeek(lp, -1), (unsigned char*)"1024", 4);
+        verifyEntry(lpSeek(lp, -4), (unsigned char*)"hello", 5);
+        assert(lpSeek(lp, 4) == NULL);
+        assert(lpSeek(lp, -5) == NULL);
+        lpFree(lp);
+    }
+    
+    TEST("Pop list") {
+        lp = createList();
+        lp = pop(lp, 1);
+        lp = pop(lp, 0);
+        lp = pop(lp, 1);
+        lp = pop(lp, 1);
+        lpFree(lp);
+    }
+
+    TEST("Get element at index") {
+        lp = createList();
+        verifyEntry(lpSeek(lp, 0), (unsigned char*)"hello", 5);
+        verifyEntry(lpSeek(lp, 3), (unsigned char*)"1024", 4);
+        verifyEntry(lpSeek(lp, -1), (unsigned char*)"1024", 4);
+        verifyEntry(lpSeek(lp, -4), (unsigned char*)"hello", 5);
+        assert(lpSeek(lp, 4) == NULL);
+        assert(lpSeek(lp, -5) == NULL);
+        lpFree(lp);
+    }
+
+    TEST("Iterate list from 0 to end") {
+        lp = createList();
+        p = lpFirst(lp);
+        i = 0;
+        while (p) {
+            verifyEntry(p, (unsigned char*)mixlist[i], strlen(mixlist[i]));
+            p = lpNext(lp, p);
+            i++;
+        }
+        lpFree(lp);
+    }
+    
+    TEST("Iterate list from 1 to end") {
+        lp = createList();
+        i = 1;
+        p = lpSeek(lp, i);
+        while (p) {
+            verifyEntry(p, (unsigned char*)mixlist[i], strlen(mixlist[i]));
+            p = lpNext(lp, p);
+            i++;
+        }
+        lpFree(lp);
+    }
+    
+    TEST("Iterate list from 2 to end") {
+        lp = createList();
+        i = 2;
+        p = lpSeek(lp, i);
+        while (p) {
+            verifyEntry(p, (unsigned char*)mixlist[i], strlen(mixlist[i]));
+            p = lpNext(lp, p);
+            i++;
+        }
+        lpFree(lp);
+    }
+    
+    TEST("Iterate from back to front") {
+        lp = createList();
+        p = lpLast(lp);
+        i = 3;
+        while (p) {
+            verifyEntry(p, (unsigned char*)mixlist[i], strlen(mixlist[i]));
+            p = lpPrev(lp, p);
+            i--;
+        }
+        lpFree(lp);
+    }
+    
+    TEST("Iterate from back to front, deleting all items") {
+        lp = createList();
+        p = lpLast(lp);
+        i = 3;
+        while ((p = lpLast(lp))) {
+            verifyEntry(p, (unsigned char*)mixlist[i], strlen(mixlist[i]));
+            lp = lpDelete(lp, p, &p);
+            assert(p == NULL);
+            i--;
+        }
+        lpFree(lp);
+    }
+
+    TEST("Delete whole listpack when num == -1");
+    {
+        lp = createList();
+        lp = lpDeleteRange(lp, 0, -1);
+        assert(lpLength(lp) == 0);
+        assert(lp[LP_HDR_SIZE] == LP_EOF);
+        assert(lpBytes(lp) == (LP_HDR_SIZE + 1));
+        zfree(lp);
+
+        lp = createList();
+        unsigned char *ptr = lpFirst(lp);
+        lp = lpDeleteRangeWithEntry(lp, &ptr, -1);
+        assert(lpLength(lp) == 0);
+        assert(lp[LP_HDR_SIZE] == LP_EOF);
+        assert(lpBytes(lp) == (LP_HDR_SIZE + 1));
+        zfree(lp);
+    }
+
+    TEST("Delete whole listpack with negative index");
+    {
+        lp = createList();
+        lp = lpDeleteRange(lp, -4, 4);
+        assert(lpLength(lp) == 0);
+        assert(lp[LP_HDR_SIZE] == LP_EOF);
+        assert(lpBytes(lp) == (LP_HDR_SIZE + 1));
+        zfree(lp);
+
+        lp = createList();
+        unsigned char *ptr = lpSeek(lp, -4);
+        lp = lpDeleteRangeWithEntry(lp, &ptr, 4);
+        assert(lpLength(lp) == 0);
+        assert(lp[LP_HDR_SIZE] == LP_EOF);
+        assert(lpBytes(lp) == (LP_HDR_SIZE + 1));
+        zfree(lp);
+    }
+
+    TEST("Delete inclusive range 0,0");
+    {
+        lp = createList();
+        lp = lpDeleteRange(lp, 0, 1);
+        assert(lpLength(lp) == 3);
+        assert(lpSkip(lpLast(lp))[0] == LP_EOF); /* check set LP_EOF correctly */
+        zfree(lp);
+
+        lp = createList();
+        unsigned char *ptr = lpFirst(lp);
+        lp = lpDeleteRangeWithEntry(lp, &ptr, 1);
+        assert(lpLength(lp) == 3);
+        assert(lpSkip(lpLast(lp))[0] == LP_EOF); /* check set LP_EOF correctly */
+        zfree(lp);
+    }
+
+    TEST("Delete inclusive range 0,1");
+    {
+        lp = createList();
+        lp = lpDeleteRange(lp, 0, 2);
+        assert(lpLength(lp) == 2);
+        verifyEntry(lpFirst(lp), (unsigned char*)mixlist[2], strlen(mixlist[2]));
+        zfree(lp);
+
+        lp = createList();
+        unsigned char *ptr = lpFirst(lp);
+        lp = lpDeleteRangeWithEntry(lp, &ptr, 2);
+        assert(lpLength(lp) == 2);
+        verifyEntry(lpFirst(lp), (unsigned char*)mixlist[2], strlen(mixlist[2]));
+        zfree(lp);
+    }
+
+    TEST("Delete inclusive range 1,2");
+    {
+        lp = createList();
+        lp = lpDeleteRange(lp, 1, 2);
+        assert(lpLength(lp) == 2);
+        verifyEntry(lpFirst(lp), (unsigned char*)mixlist[0], strlen(mixlist[0]));
+        zfree(lp);
+
+        lp = createList();
+        unsigned char *ptr = lpSeek(lp, 1);
+        lp = lpDeleteRangeWithEntry(lp, &ptr, 2);
+        assert(lpLength(lp) == 2);
+        verifyEntry(lpFirst(lp), (unsigned char*)mixlist[0], strlen(mixlist[0]));
+        zfree(lp);
+    }
+    
+    TEST("Delete with start index out of range");
+    {
+        lp = createList();
+        lp = lpDeleteRange(lp, 5, 1);
+        assert(lpLength(lp) == 4);
+        zfree(lp);
+    }
+
+    TEST("Delete with num overflow");
+    {
+        lp = createList();
+        lp = lpDeleteRange(lp, 1, 5);
+        assert(lpLength(lp) == 1);
+        verifyEntry(lpFirst(lp), (unsigned char*)mixlist[0], strlen(mixlist[0]));
+        zfree(lp);
+
+        lp = createList();
+        unsigned char *ptr = lpSeek(lp, 1);
+        lp = lpDeleteRangeWithEntry(lp, &ptr, 5);
+        assert(lpLength(lp) == 1);
+        verifyEntry(lpFirst(lp), (unsigned char*)mixlist[0], strlen(mixlist[0]));
+        zfree(lp);
+    }
+
+    TEST("Batch delete") {
+        unsigned char *lp = createList(); /* char *mixlist[] = {"hello", "foo", "quux", "1024"} */
+        assert(lpLength(lp) == 4); /* Pre-condition */
+        unsigned char *p0 = lpFirst(lp),
+            *p1 = lpNext(lp, p0),
+            *p2 = lpNext(lp, p1),
+            *p3 = lpNext(lp, p2);
+        unsigned char *ps[] = {p0, p1, p3};
+        lp = lpBatchDelete(lp, ps, 3);
+        assert(lpLength(lp) == 1);
+        verifyEntry(lpFirst(lp), (unsigned char*)mixlist[2], strlen(mixlist[2]));
+        assert(lpValidateIntegrity(lp, lpBytes(lp), 1, NULL, NULL) == 1);
+        lpFree(lp);
+    }
+
+    TEST("Delete foo while iterating") {
+        lp = createList();
+        p = lpFirst(lp);
+        while (p) {
+            if (lpCompare(p, (unsigned char*)"foo", 3)) {
+                lp = lpDelete(lp, p, &p);
+            } else {
+                p = lpNext(lp, p);
+            }
+        }
+        lpFree(lp);
+    }
+
+    TEST("Replace with same size") {
+        lp = createList(); /* "hello", "foo", "quux", "1024" */
+        unsigned char *orig_lp = lp;
+        p = lpSeek(lp, 0);
+        lp = lpReplace(lp, &p, (unsigned char*)"zoink", 5);
+        p = lpSeek(lp, 3);
+        lp = lpReplace(lp, &p, (unsigned char*)"y", 1);
+        p = lpSeek(lp, 1);
+        lp = lpReplace(lp, &p, (unsigned char*)"65536", 5);
+        p = lpSeek(lp, 0);
+        assert(!memcmp((char*)p,
+                       "\x85zoink\x06"
+                       "\xf2\x00\x00\x01\x04" /* 65536 as int24 */
+                       "\x84quux\05" "\x81y\x02" "\xff",
+                       22));
+        assert(lp == orig_lp); /* no reallocations have happened */
+        lpFree(lp);
+    }
+
+    TEST("Replace with different size") {
+        lp = createList(); /* "hello", "foo", "quux", "1024" */
+        p = lpSeek(lp, 1);
+        lp = lpReplace(lp, &p, (unsigned char*)"squirrel", 8);
+        p = lpSeek(lp, 0);
+        assert(!strncmp((char*)p,
+                        "\x85hello\x06" "\x88squirrel\x09" "\x84quux\x05"
+                        "\xc4\x00\x02" "\xff",
+                        27));
+        lpFree(lp);
+    }
+
+    TEST("Regression test for >255 byte strings") {
+        char v1[257] = {0}, v2[257] = {0};
+        memset(v1,'x',256);
+        memset(v2,'y',256);
+        lp = lpNew(0);
+        lp = lpAppend(lp, (unsigned char*)v1 ,strlen(v1));
+        lp = lpAppend(lp, (unsigned char*)v2 ,strlen(v2));
+
+        /* Pop values again and compare their value. */
+        p = lpFirst(lp);
+        vstr = lpGet(p, &vlen, NULL);
+        assert(strncmp(v1, (char*)vstr, vlen) == 0);
+        p = lpSeek(lp, 1);
+        vstr = lpGet(p, &vlen, NULL);
+        assert(strncmp(v2, (char*)vstr, vlen) == 0);
+        lpFree(lp);
+    }
+
+    TEST("Create long list and check indices") {
+        lp = lpNew(0);
+        char buf[32];
+        int i,len;
+        for (i = 0; i < 1000; i++) {
+            len = snprintf(buf, sizeof(buf), "%d", i);
+            lp = lpAppend(lp, (unsigned char*)buf, len);
+        }
+        for (i = 0; i < 1000; i++) {
+            p = lpSeek(lp, i);
+            vstr = lpGet(p, &vlen, NULL);
+            assert(i == vlen);
+
+            p = lpSeek(lp, -i-1);
+            vstr = lpGet(p, &vlen, NULL);
+            assert(999-i == vlen);
+        }
+        lpFree(lp);
+    }
+
+    TEST("Compare strings with listpack entries") {
+        lp = createList();
+        p = lpSeek(lp,0);
+        assert(lpCompare(p,(unsigned char*)"hello",5));
+        assert(!lpCompare(p,(unsigned char*)"hella",5));
+
+        p = lpSeek(lp,3);
+        assert(lpCompare(p,(unsigned char*)"1024",4));
+        assert(!lpCompare(p,(unsigned char*)"1025",4));
+        lpFree(lp);
+    }
+
+    TEST("lpMerge two empty listpacks") {
+        unsigned char *lp1 = lpNew(0);
+        unsigned char *lp2 = lpNew(0);
+
+        /* Merge two empty listpacks, get empty result back. */
+        lp1 = lpMerge(&lp1, &lp2);
+        assert(lpLength(lp1) == 0);
+        zfree(lp1);
+    }
+
+    TEST("lpMerge two listpacks - first larger than second") {
+        unsigned char *lp1 = createIntList();
+        unsigned char *lp2 = createList();
+
+        size_t lp1_bytes = lpBytes(lp1);
+        size_t lp2_bytes = lpBytes(lp2);
+        unsigned long lp1_len = lpLength(lp1);
+        unsigned long lp2_len = lpLength(lp2);
+
+        unsigned char *lp3 = lpMerge(&lp1, &lp2);
+        assert(lp3 == lp1);
+        assert(lp2 == NULL);
+        assert(lpLength(lp3) == (lp1_len + lp2_len));
+        assert(lpBytes(lp3) == (lp1_bytes + lp2_bytes - LP_HDR_SIZE - 1));
+        verifyEntry(lpSeek(lp3, 0), (unsigned char*)"4294967296", 10);
+        verifyEntry(lpSeek(lp3, 5), (unsigned char*)"much much longer non integer", 28);
+        verifyEntry(lpSeek(lp3, 6), (unsigned char*)"hello", 5);
+        verifyEntry(lpSeek(lp3, -1), (unsigned char*)"1024", 4);
+        zfree(lp3);
+    }
+
+    TEST("lpMerge two listpacks - second larger than first") {
+        unsigned char *lp1 = createList();
+        unsigned char *lp2 = createIntList();
+
+        size_t lp1_bytes = lpBytes(lp1);
+        size_t lp2_bytes = lpBytes(lp2);
+        unsigned long lp1_len = lpLength(lp1);
+        unsigned long lp2_len = lpLength(lp2);
+
+        unsigned char *lp3 = lpMerge(&lp1, &lp2);
+        assert(lp3 == lp2);
+        assert(lp1 == NULL);
+        assert(lpLength(lp3) == (lp1_len + lp2_len));
+        assert(lpBytes(lp3) == (lp1_bytes + lp2_bytes - LP_HDR_SIZE - 1));
+        verifyEntry(lpSeek(lp3, 0), (unsigned char*)"hello", 5);
+        verifyEntry(lpSeek(lp3, 3), (unsigned char*)"1024", 4);
+        verifyEntry(lpSeek(lp3, 4), (unsigned char*)"4294967296", 10);
+        verifyEntry(lpSeek(lp3, -1), (unsigned char*)"much much longer non integer", 28);
+        zfree(lp3);
+    }
+
+    TEST("lpNextRandom normal usage") {
+        /* Create some data */
+        unsigned char *lp = lpNew(0);
+        unsigned char buf[100] = "asdf";
+        unsigned int size = 100;
+        for (size_t i = 0; i < size; i++) {
+            lp = lpAppend(lp, buf, i);
+        }
+        assert(lpLength(lp) == size);
+
+        /* Pick a subset of the elements of every possible subset size */
+        for (unsigned int count = 0; count <= size; count++) {
+            unsigned int remaining = count;
+            unsigned char *p = lpFirst(lp);
+            unsigned char *prev = NULL;
+            unsigned index = 0;
+            while (remaining > 0) {
+                assert(p != NULL);
+                p = lpNextRandom(lp, p, &index, remaining--, 0);
+                assert(p != NULL);
+                assert(p != prev);
+                prev = p;
+                p = lpNext(lp, p);
+                index++;
+            }
+        }
+        lpFree(lp);
+    }
+
+    TEST("lpNextRandom corner cases") {
+        unsigned char *lp = lpNew(0);
+        unsigned i = 0;
+
+        /* Pick from empty listpack returns NULL. */
+        assert(lpNextRandom(lp, NULL, &i, 2, 0) == NULL);
+
+        /* Add some elements and find their pointers within the listpack. */
+        lp = lpAppend(lp, (unsigned char *)"abc", 3);
+        lp = lpAppend(lp, (unsigned char *)"def", 3);
+        lp = lpAppend(lp, (unsigned char *)"ghi", 3);
+        assert(lpLength(lp) == 3);
+        unsigned char *p0 = lpFirst(lp);
+        unsigned char *p1 = lpNext(lp, p0);
+        unsigned char *p2 = lpNext(lp, p1);
+        assert(lpNext(lp, p2) == NULL);
+
+        /* Pick zero elements returns NULL. */
+        i = 0; assert(lpNextRandom(lp, lpFirst(lp), &i, 0, 0) == NULL);
+
+        /* Pick all returns all. */
+        i = 0; assert(lpNextRandom(lp, p0, &i, 3, 0) == p0 && i == 0);
+        i = 1; assert(lpNextRandom(lp, p1, &i, 2, 0) == p1 && i == 1);
+        i = 2; assert(lpNextRandom(lp, p2, &i, 1, 0) == p2 && i == 2);
+
+        /* Pick more than one when there's only one left returns the last one. */
+        i = 2; assert(lpNextRandom(lp, p2, &i, 42, 0) == p2 && i == 2);
+
+        /* Pick all even elements returns p0 and p2. */
+        i = 0; assert(lpNextRandom(lp, p0, &i, 10, 1) == p0 && i == 0);
+        i = 1; assert(lpNextRandom(lp, p1, &i, 10, 1) == p2 && i == 2);
+
+        /* Don't crash even for bad index. */
+        for (int j = 0; j < 100; j++) {
+            unsigned char *p;
+            switch (j % 4) {
+            case 0: p = p0; break;
+            case 1: p = p1; break;
+            case 2: p = p2; break;
+            case 3: p = NULL; break;
+            }
+            i = j % 7;
+            unsigned int remaining = j % 5;
+            p = lpNextRandom(lp, p, &i, remaining, 0);
+            assert(p == p0 || p == p1 || p == p2 || p == NULL);
+        }
+        lpFree(lp);
+    }
+
+    TEST("Random pair with one element") {
+        listpackEntry key, val;
+        unsigned char *lp = lpNew(0);
+        lp = lpAppend(lp, (unsigned char*)"abc", 3);
+        lp = lpAppend(lp, (unsigned char*)"123", 3);
+        lpRandomPair(lp, 1, &key, &val);
+        assert(memcmp(key.sval, "abc", key.slen) == 0);
+        assert(val.lval == 123);
+        lpFree(lp);
+    }
+
+    TEST("Random pair with many elements") {
+        listpackEntry key, val;
+        unsigned char *lp = lpNew(0);
+        lp = lpAppend(lp, (unsigned char*)"abc", 3);
+        lp = lpAppend(lp, (unsigned char*)"123", 3);
+        lp = lpAppend(lp, (unsigned char*)"456", 3);
+        lp = lpAppend(lp, (unsigned char*)"def", 3);
+        lpRandomPair(lp, 2, &key, &val);
+        if (key.sval) {
+            assert(!memcmp(key.sval, "abc", key.slen));
+            assert(key.slen == 3);
+            assert(val.lval == 123);
+        }
+        if (!key.sval) {
+            assert(key.lval == 456);
+            assert(!memcmp(val.sval, "def", val.slen));
+        }
+        lpFree(lp);
+    }
+
+    TEST("Random pairs with one element") {
+        int count = 5;
+        unsigned char *lp = lpNew(0);
+        listpackEntry *keys = zmalloc(sizeof(listpackEntry) * count);
+        listpackEntry *vals = zmalloc(sizeof(listpackEntry) * count);
+
+        lp = lpAppend(lp, (unsigned char*)"abc", 3);
+        lp = lpAppend(lp, (unsigned char*)"123", 3);
+        lpRandomPairs(lp, count, keys, vals);
+        assert(memcmp(keys[4].sval, "abc", keys[4].slen) == 0);
+        assert(vals[4].lval == 123);
+        zfree(keys);
+        zfree(vals);
+        lpFree(lp);
+    }
+
+    TEST("Random pairs with many elements") {
+        int count = 5;
+        lp = lpNew(0);
+        listpackEntry *keys = zmalloc(sizeof(listpackEntry) * count);
+        listpackEntry *vals = zmalloc(sizeof(listpackEntry) * count);
+
+        lp = lpAppend(lp, (unsigned char*)"abc", 3);
+        lp = lpAppend(lp, (unsigned char*)"123", 3);
+        lp = lpAppend(lp, (unsigned char*)"456", 3);
+        lp = lpAppend(lp, (unsigned char*)"def", 3);
+        lpRandomPairs(lp, count, keys, vals);
+        for (int i = 0; i < count; i++) {
+            if (keys[i].sval) {
+                assert(!memcmp(keys[i].sval, "abc", keys[i].slen));
+                assert(keys[i].slen == 3);
+                assert(vals[i].lval == 123);
+            }
+            if (!keys[i].sval) {
+                assert(keys[i].lval == 456);
+                assert(!memcmp(vals[i].sval, "def", vals[i].slen));
+            }
+        }
+        zfree(keys);
+        zfree(vals);
+        lpFree(lp);
+    }
+
+    TEST("Random pairs unique with one element") {
+        unsigned picked;
+        int count = 5;
+        lp = lpNew(0);
+        listpackEntry *keys = zmalloc(sizeof(listpackEntry) * count);
+        listpackEntry *vals = zmalloc(sizeof(listpackEntry) * count);
+
+        lp = lpAppend(lp, (unsigned char*)"abc", 3);
+        lp = lpAppend(lp, (unsigned char*)"123", 3);
+        picked = lpRandomPairsUnique(lp, count, keys, vals);
+        assert(picked == 1);
+        assert(memcmp(keys[0].sval, "abc", keys[0].slen) == 0);
+        assert(vals[0].lval == 123);
+        zfree(keys);
+        zfree(vals);
+        lpFree(lp);
+    }
+
+    TEST("Random pairs unique with many elements") {
+        unsigned picked;
+        int count = 5;
+        lp = lpNew(0);
+        listpackEntry *keys = zmalloc(sizeof(listpackEntry) * count);
+        listpackEntry *vals = zmalloc(sizeof(listpackEntry) * count);
+
+        lp = lpAppend(lp, (unsigned char*)"abc", 3);
+        lp = lpAppend(lp, (unsigned char*)"123", 3);
+        lp = lpAppend(lp, (unsigned char*)"456", 3);
+        lp = lpAppend(lp, (unsigned char*)"def", 3);
+        picked = lpRandomPairsUnique(lp, count, keys, vals);
+        assert(picked == 2);
+        for (int i = 0; i < 2; i++) {
+            if (keys[i].sval) {
+                assert(!memcmp(keys[i].sval, "abc", keys[i].slen));
+                assert(keys[i].slen == 3);
+                assert(vals[i].lval == 123);
+            }
+            if (!keys[i].sval) {
+                assert(keys[i].lval == 456);
+                assert(!memcmp(vals[i].sval, "def", vals[i].slen));
+            }
+        }
+        zfree(keys);
+        zfree(vals);
+        lpFree(lp);
+    }
+
+    TEST("push various encodings") {
+        lp = lpNew(0);
+
+        /* Push integer encode element using lpAppend */
+        lp = lpAppend(lp, (unsigned char*)"127", 3);
+        assert(LP_ENCODING_IS_7BIT_UINT(lpLast(lp)[0]));
+        lp = lpAppend(lp, (unsigned char*)"4095", 4);
+        assert(LP_ENCODING_IS_13BIT_INT(lpLast(lp)[0]));
+        lp = lpAppend(lp, (unsigned char*)"32767", 5);
+        assert(LP_ENCODING_IS_16BIT_INT(lpLast(lp)[0]));
+        lp = lpAppend(lp, (unsigned char*)"8388607", 7);
+        assert(LP_ENCODING_IS_24BIT_INT(lpLast(lp)[0]));
+        lp = lpAppend(lp, (unsigned char*)"2147483647", 10);
+        assert(LP_ENCODING_IS_32BIT_INT(lpLast(lp)[0]));
+        lp = lpAppend(lp, (unsigned char*)"9223372036854775807", 19);
+        assert(LP_ENCODING_IS_64BIT_INT(lpLast(lp)[0]));
+
+        /* Push integer encode element using lpAppendInteger */
+        lp = lpAppendInteger(lp, 127);
+        assert(LP_ENCODING_IS_7BIT_UINT(lpLast(lp)[0]));
+        verifyEntry(lpLast(lp), (unsigned char*)"127", 3);
+        lp = lpAppendInteger(lp, 4095);
+        verifyEntry(lpLast(lp), (unsigned char*)"4095", 4);
+        assert(LP_ENCODING_IS_13BIT_INT(lpLast(lp)[0]));
+        lp = lpAppendInteger(lp, 32767);
+        verifyEntry(lpLast(lp), (unsigned char*)"32767", 5);
+        assert(LP_ENCODING_IS_16BIT_INT(lpLast(lp)[0]));
+        lp = lpAppendInteger(lp, 8388607);
+        verifyEntry(lpLast(lp), (unsigned char*)"8388607", 7);
+        assert(LP_ENCODING_IS_24BIT_INT(lpLast(lp)[0]));
+        lp = lpAppendInteger(lp, 2147483647);
+        verifyEntry(lpLast(lp), (unsigned char*)"2147483647", 10);
+        assert(LP_ENCODING_IS_32BIT_INT(lpLast(lp)[0]));
+        lp = lpAppendInteger(lp, 9223372036854775807);
+        verifyEntry(lpLast(lp), (unsigned char*)"9223372036854775807", 19);
+        assert(LP_ENCODING_IS_64BIT_INT(lpLast(lp)[0]));
+
+        /* string encode */
+        unsigned char *str = zmalloc(65535);
+        memset(str, 0, 65535);
+        lp = lpAppend(lp, (unsigned char*)str, 63);
+        assert(LP_ENCODING_IS_6BIT_STR(lpLast(lp)[0]));
+        lp = lpAppend(lp, (unsigned char*)str, 4095);
+        assert(LP_ENCODING_IS_12BIT_STR(lpLast(lp)[0]));
+        lp = lpAppend(lp, (unsigned char*)str, 65535);
+        assert(LP_ENCODING_IS_32BIT_STR(lpLast(lp)[0]));
+        zfree(str);
+        lpFree(lp);
+    }
+
+    TEST("Test lpFind") {
+        lp = createList();
+        assert(lpFind(lp, lpFirst(lp), (unsigned char*)"abc", 3, 0) == NULL);
+        verifyEntry(lpFind(lp, lpFirst(lp), (unsigned char*)"hello", 5, 0), (unsigned char*)"hello", 5);
+        verifyEntry(lpFind(lp, lpFirst(lp), (unsigned char*)"1024", 4, 0), (unsigned char*)"1024", 4);
+        lpFree(lp);
+    }
+
+    TEST("Test lpValidateIntegrity") {
+        lp = createList();
+        long count = 0;
+        assert(lpValidateIntegrity(lp, lpBytes(lp), 1, lpValidation, &count) == 1);
+        lpFree(lp);
+    }
+
+    TEST("Test number of elements exceeds LP_HDR_NUMELE_UNKNOWN") {
+        lp = lpNew(0);
+        for (int i = 0; i < LP_HDR_NUMELE_UNKNOWN + 1; i++)
+            lp = lpAppend(lp, (unsigned char*)"1", 1);
+
+        assert(lpGetNumElements(lp) == LP_HDR_NUMELE_UNKNOWN);
+        assert(lpLength(lp) == LP_HDR_NUMELE_UNKNOWN+1);
+
+        lp = lpDeleteRange(lp, -2, 2);
+        assert(lpGetNumElements(lp) == LP_HDR_NUMELE_UNKNOWN);
+        assert(lpLength(lp) == LP_HDR_NUMELE_UNKNOWN-1);
+        assert(lpGetNumElements(lp) == LP_HDR_NUMELE_UNKNOWN-1); /* update length after lpLength */
+        lpFree(lp);
+    }
+
+    TEST("Stress with random payloads of different encoding") {
+        unsigned long long start = usec();
+        int i,j,len,where;
+        unsigned char *p;
+        char buf[1024];
+        int buflen;
+        list *ref;
+        listNode *refnode;
+
+        int iteration = accurate ? 20000 : 20;
+        for (i = 0; i < iteration; i++) {
+            lp = lpNew(0);
+            ref = listCreate();
+            listSetFreeMethod(ref,(void (*)(void*))sdsfree);
+            len = rand() % 256;
+
+            /* Create lists */
+            for (j = 0; j < len; j++) {
+                where = (rand() & 1) ? 0 : 1;
+                if (rand() % 2) {
+                    buflen = randstring(buf,1,sizeof(buf)-1);
+                } else {
+                    switch(rand() % 3) {
+                    case 0:
+                        buflen = snprintf(buf,sizeof(buf),"%lld",(0LL + rand()) >> 20);
+                        break;
+                    case 1:
+                        buflen = snprintf(buf,sizeof(buf),"%lld",(0LL + rand()));
+                        break;
+                    case 2:
+                        buflen = snprintf(buf,sizeof(buf),"%lld",(0LL + rand()) << 20);
+                        break;
+                    default:
+                        assert(NULL);
+                    }
+                }
+
+                /* Add to listpack */
+                if (where == 0) {
+                    lp = lpPrepend(lp, (unsigned char*)buf, buflen);
+                } else {
+                    lp = lpAppend(lp, (unsigned char*)buf, buflen);
+                }
+
+                /* Add to reference list */
+                if (where == 0) {
+                    listAddNodeHead(ref,sdsnewlen(buf, buflen));
+                } else if (where == 1) {
+                    listAddNodeTail(ref,sdsnewlen(buf, buflen));
+                } else {
+                    assert(NULL);
+                }
+            }
+
+            assert(listLength(ref) == lpLength(lp));
+            for (j = 0; j < len; j++) {
+                /* Naive way to get elements, but similar to the stresser
+                 * executed from the Tcl test suite. */
+                p = lpSeek(lp,j);
+                refnode = listIndex(ref,j);
+
+                vstr = lpGet(p, &vlen, intbuf);
+                assert(memcmp(vstr,listNodeValue(refnode),vlen) == 0);
+            }
+            lpFree(lp);
+            listRelease(ref);
+        }
+        printf("Done. usec=%lld\n\n", usec()-start);
+    }
+
+    TEST("Stress with variable listpack size") {
+        unsigned long long start = usec();
+        int maxsize = accurate ? 16384 : 16;
+        stress(0,100000,maxsize,256);
+        stress(1,100000,maxsize,256);
+        printf("Done. usec=%lld\n\n", usec()-start);
+    }
+
+    /* Benchmarks */
+    {
+        int iteration = accurate ? 100000 : 100;
+        lp = lpNew(0);
+        TEST("Benchmark lpAppend") {
+            unsigned long long start = usec();
+            for (int i=0; i<iteration; i++) {
+                char buf[4096] = "asdf";
+                lp = lpAppend(lp, (unsigned char*)buf, 4);
+                lp = lpAppend(lp, (unsigned char*)buf, 40);
+                lp = lpAppend(lp, (unsigned char*)buf, 400);
+                lp = lpAppend(lp, (unsigned char*)buf, 4000);
+                lp = lpAppend(lp, (unsigned char*)"1", 1);
+                lp = lpAppend(lp, (unsigned char*)"10", 2);
+                lp = lpAppend(lp, (unsigned char*)"100", 3);
+                lp = lpAppend(lp, (unsigned char*)"1000", 4);
+                lp = lpAppend(lp, (unsigned char*)"10000", 5);
+                lp = lpAppend(lp, (unsigned char*)"100000", 6);
+            }
+            printf("Done. usec=%lld\n", usec()-start);
+        }
+
+        TEST("Benchmark lpFind string") {
+            unsigned long long start = usec();
+            for (int i = 0; i < 2000; i++) {
+                unsigned char *fptr = lpFirst(lp);
+                fptr = lpFind(lp, fptr, (unsigned char*)"nothing", 7, 1);
+            }
+            printf("Done. usec=%lld\n", usec()-start);
+        }
+
+        TEST("Benchmark lpFind number") {
+            unsigned long long start = usec();
+            for (int i = 0; i < 2000; i++) {
+                unsigned char *fptr = lpFirst(lp);
+                fptr = lpFind(lp, fptr, (unsigned char*)"99999", 5, 1);
+            }
+            printf("Done. usec=%lld\n", usec()-start);
+        }
+
+        TEST("Benchmark lpSeek") {
+            unsigned long long start = usec();
+            for (int i = 0; i < 2000; i++) {
+                lpSeek(lp, 99999);
+            }
+            printf("Done. usec=%lld\n", usec()-start);
+        }
+
+        TEST("Benchmark lpValidateIntegrity") {
+            unsigned long long start = usec();
+            for (int i = 0; i < 2000; i++) {
+                lpValidateIntegrity(lp, lpBytes(lp), 1, NULL, NULL);
+            }
+            printf("Done. usec=%lld\n", usec()-start);
+        }
+
+        TEST("Benchmark lpCompare with string") {
+            unsigned long long start = usec();
+            for (int i = 0; i < 2000; i++) {
+                unsigned char *eptr = lpSeek(lp,0);
+                while (eptr != NULL) {
+                    lpCompare(eptr,(unsigned char*)"nothing",7);
+                    eptr = lpNext(lp,eptr);
+                }
+            }
+            printf("Done. usec=%lld\n", usec()-start);
+        }
+
+        TEST("Benchmark lpCompare with number") {
+            unsigned long long start = usec();
+            for (int i = 0; i < 2000; i++) {
+                unsigned char *eptr = lpSeek(lp,0);
+                while (eptr != NULL) {
+                    lpCompare(lp, (unsigned char*)"99999", 5);
+                    eptr = lpNext(lp,eptr);
+                }
+            }
+            printf("Done. usec=%lld\n", usec()-start);
+        }
+
+        lpFree(lp);
+    }
+
+    return 0;
+}
+
+#endif