Replace all usage of ziplist with listpack for t_hash (#8887)

Part one of implementing #8702 (taking hashes first before other types)

## Description of the feature
1. Change ziplist encoded hash objects to listpack encoding.
2. Convert existing ziplists on RDB loading time. an O(n) operation.

## Rdb format changes
1. Add RDB_TYPE_HASH_LISTPACK rdb type.
2. Bump RDB_VERSION to 10

## Interface changes
1. New `hash-max-listpack-entries` config is an alias for `hash-max-ziplist-entries` (same with `hash-max-listpack-value`)
2. OBJECT ENCODING will return `listpack` instead of `ziplist`

## Listpack improvements:
1. Support direct insert, replace integer element (rather than convert back and forth from string)
3. Add more listpack capabilities to match the ziplist ones (like `lpFind`, `lpRandomPairs` and such)
4. Optimize element length fetching, avoid multiple calculations
5. Use inline to avoid function call overhead.

## Tests
1. Add a new test to the RDB load time conversion
2. Adding the listpack unit tests. (based on the one in ziplist.c)
3. Add a few "corrupt payload: fuzzer findings" tests, and slightly modify existing ones.

Co-authored-by: Oran Agra <oran@redislabs.com>

1 files changed, 1090 insertions, 92 deletions

diff --git a/src/listpack.c b/src/listpack.c
index 8672f63c8..9bb1c8c95 100644
--- a/src/listpack.c
+++ b/src/listpack.c
@@ -55,6 +55,7 @@
 #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
@@ -63,6 +64,7 @@
 #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
@@ -71,18 +73,22 @@
 #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
@@ -246,6 +252,58 @@ unsigned char* lpShrinkToFit(unsigned char *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
@@ -257,57 +315,10 @@ unsigned char* lpShrinkToFit(unsigned char *lp) {
  * 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. */
-int lpEncodeGetType(unsigned char *ele, uint32_t size, unsigned char *intenc, uint64_t *enclen) {
+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)) {
-        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;
-        }
+        lpEncodeIntegerGetType(v, intenc, enclen);
         return LP_ENCODING_INT;
     } else {
         if (size < 64) *enclen = 1+size;
@@ -322,7 +333,7 @@ int lpEncodeGetType(unsigned char *ele, uint32_t size, unsigned char *intenc, ui
  * 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. */
-unsigned long lpEncodeBacklen(unsigned char *buf, uint64_t l) {
+static inline unsigned long lpEncodeBacklen(unsigned char *buf, uint64_t l) {
     if (l <= 127) {
         if (buf) buf[0] = l;
         return 1;
@@ -361,7 +372,7 @@ unsigned long lpEncodeBacklen(unsigned char *buf, uint64_t l) {
 
 /* 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. */
-uint64_t lpDecodeBacklen(unsigned char *p) {
+static inline uint64_t lpDecodeBacklen(unsigned char *p) {
     uint64_t val = 0;
     uint64_t shift = 0;
     do {
@@ -378,7 +389,7 @@ uint64_t lpDecodeBacklen(unsigned char *p) {
  * 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. */
-void lpEncodeString(unsigned char *buf, unsigned char *s, uint32_t len) {
+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);
@@ -403,7 +414,7 @@ void lpEncodeString(unsigned char *buf, unsigned char *s, uint32_t len) {
  * 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. */
-uint32_t lpCurrentEncodedSizeUnsafe(unsigned char *p) {
+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;
@@ -421,7 +432,7 @@ uint32_t lpCurrentEncodedSizeUnsafe(unsigned char *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. */
-uint32_t lpCurrentEncodedSizeBytes(unsigned char *p) {
+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;
@@ -492,7 +503,7 @@ unsigned char *lpLast(unsigned char *lp) {
  * 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. */
-uint32_t lpLength(unsigned char *lp) {
+unsigned long lpLength(unsigned char *lp) {
     uint32_t numele = lpGetNumElements(lp);
     if (numele != LP_HDR_NUMELE_UNKNOWN) return numele;
 
@@ -534,6 +545,10 @@ uint32_t lpLength(unsigned char *lp) {
  * 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
@@ -545,7 +560,7 @@ uint32_t lpLength(unsigned char *lp) {
  * assumed to be valid, so that would be a very high API cost. However a function
  * in order to check the integrity of the listpack at load time is provided,
  * check lpIsValid(). */
-unsigned char *lpGet(unsigned char *p, int64_t *count, unsigned char *intbuf) {
+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;
 
@@ -554,24 +569,29 @@ unsigned char *lpGet(unsigned char *p, int64_t *count, unsigned char *intbuf) {
         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 |
@@ -579,6 +599,7 @@ unsigned char *lpGet(unsigned char *p, int64_t *count, unsigned char *intbuf) {
                (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 |
@@ -590,11 +611,14 @@ unsigned char *lpGet(unsigned char *p, int64_t *count, unsigned char *intbuf) {
                (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];
@@ -626,17 +650,105 @@ unsigned char *lpGet(unsigned char *p, int64_t *count, unsigned char *intbuf) {
     }
 }
 
-/* Insert, delete or replace the specified element 'ele' of length 'len' at
- * the specified position 'p', with 'p' being a listpack element pointer
- * obtained with lpFirst(), lpLast(), lpNext(), lpPrev() or lpSeek().
+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) {
+                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 `ASSERT_INTEGRITY` in
+            * `lpNext` will call `lpBytes`, will cause performance degradation */
+            p = lpSkip(p);
+        }
+
+        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 'ele' is set to NULL, the function removes the element pointed by 'p'
- * instead of inserting one.
- *
+ * 
+ * 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
@@ -646,19 +758,22 @@ unsigned char *lpGet(unsigned char *p, int64_t *count, unsigned char *intbuf) {
  * 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 ('ele' 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 *ele, uint32_t size, unsigned char *p, int where, unsigned char **newp) {
+ * 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);
 
-    /* An element pointer set to NULL means deletion, which is conceptually
-     * replacing the element with a zero-length element. So whatever we
-     * get passed as 'where', set it to LP_REPLACE. */
-    if (ele == NULL) where = LP_REPLACE;
+    /* 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
@@ -674,17 +789,21 @@ unsigned char *lpInsert(unsigned char *lp, unsigned char *ele, uint32_t size, un
      * address again after a reallocation. */
     unsigned long poff = p-lp;
 
-    /* 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. */
     int enctype;
-    if (ele) {
-        enctype = lpEncodeGetType(ele,size,intenc,&enclen);
+    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;
@@ -693,7 +812,7 @@ unsigned char *lpInsert(unsigned char *lp, unsigned char *ele, uint32_t size, un
     /* 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 = ele ? lpEncodeBacklen(backlen,enclen) : 0;
+    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) {
@@ -743,13 +862,13 @@ unsigned char *lpInsert(unsigned char *lp, unsigned char *ele, uint32_t size, un
         *newp = dst;
         /* In case of deletion, set 'newp' to NULL if the next element is
          * the EOF element. */
-        if (!ele && dst[0] == LP_EOF) *newp = NULL;
+        if (delete && dst[0] == LP_EOF) *newp = NULL;
     }
-    if (ele) {
+    if (!delete) {
         if (enctype == LP_ENCODING_INT) {
-            memcpy(dst,intenc,enclen);
+            memcpy(dst,eleint,enclen);
         } else {
-            lpEncodeString(dst,ele,size);
+            lpEncodeString(dst,elestr,size);
         }
         dst += enclen;
         memcpy(dst,backlen,backlen_size);
@@ -757,10 +876,10 @@ unsigned char *lpInsert(unsigned char *lp, unsigned char *ele, uint32_t size, un
     }
 
     /* Update header. */
-    if (where != LP_REPLACE || ele == NULL) {
+    if (where != LP_REPLACE || delete) {
         uint32_t num_elements = lpGetNumElements(lp);
         if (num_elements != LP_HDR_NUMELE_UNKNOWN) {
-            if (ele)
+            if (!delete)
                 lpSetNumElements(lp,num_elements+1);
             else
                 lpSetNumElements(lp,num_elements-1);
@@ -790,13 +909,59 @@ unsigned char *lpInsert(unsigned char *lp, unsigned char *ele, uint32_t size, un
     return lp;
 }
 
+/* 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 'len' 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,size,eofptr,LP_BEFORE,NULL);
+    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.
@@ -804,11 +969,11 @@ unsigned char *lpAppend(unsigned char *lp, unsigned char *ele, uint32_t size) {
  * 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,0,p,LP_REPLACE,newp);
+    return lpInsert(lp,NULL,NULL,0,p,LP_REPLACE,newp);
 }
 
 /* Return the total number of bytes the listpack is composed of. */
-uint32_t lpBytes(unsigned char *lp) {
+size_t lpBytes(unsigned char *lp) {
     return lpGetTotalBytes(lp);
 }
 
@@ -927,7 +1092,8 @@ static inline void lpAssertValidEntry(unsigned char* lp, size_t lpbytes, unsigne
 /* 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){
+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;
@@ -948,8 +1114,17 @@ int lpValidateIntegrity(unsigned char *lp, size_t size, int deep){
     uint32_t count = 0;
     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, cb_userdata))
+            return 0;
+
         count++;
     }
 
@@ -960,3 +1135,826 @@ int lpValidateIntegrity(unsigned char *lp, size_t size, int deep){
 
     return 1;
 }
+
+unsigned int lpCompare(unsigned char *p, unsigned char *s, uint32_t slen) {
+    unsigned char buf[LP_INTBUF_SIZE];
+    unsigned char *value;
+    int64_t sz;
+
+    if (p[0] == LP_EOF) return 0;
+    value = lpGet(p, &sz, buf);
+    return (slen == sz) && memcmp(value,s,slen) == 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 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 = zmalloc(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);
+    }
+
+    zfree(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;
+
+    /* 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 in the dict, this way, we could make every
+     * member be equally picked.*/
+    p = lpFirst(lp);
+    unsigned int picked = 0, remaining = count;
+    while (picked < count && p) {
+        double randomDouble = ((double)rand()) / RAND_MAX;
+        double threshold = ((double)remaining) / (total_size - index);
+        if (randomDouble <= threshold) {
+            key = lpGetValue(p, &klen, &klval);
+            lpSaveValue(key, klen, klval, &keys[picked]);
+            assert((p = lpNext(lp, p)));
+            if (vals) {
+                key = lpGetValue(p, &klen, &klval);
+                lpSaveValue(key, klen, klval, &vals[picked]);
+            }
+            remaining--;
+            picked++;
+        } else {
+            assert((p = lpNext(lp, p)));
+        }
+        p = lpNext(lp, p);
+        index++;
+    }
+    return picked;
+}
+
+#ifdef REDIS_TEST
+
+#include <sys/time.h>
+#include "adlist.h"
+#include "sds.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() {
+    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() {
+    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, void *userdata) {
+    UNUSED(p);
+
+    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 accurate) {
+    UNUSED(argc);
+    UNUSED(argv);
+    UNUSED(accurate);
+
+    int i;
+    unsigned char *lp, *p, *vstr;
+    int64_t vlen;
+    unsigned char intbuf[LP_INTBUF_SIZE];
+
+    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 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 = sprintf(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("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("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 = sprintf(buf,"%lld",(0LL + rand()) >> 20);
+                        break;
+                    case 1:
+                        buflen = sprintf(buf,"%lld",(0LL + rand()));
+                        break;
+                    case 2:
+                        buflen = sprintf(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);
+        }
+
+        lpFree(lp);
+    }
+
+    return 0;
+}
+
+#endif