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ziplist: better comments, some refactoring.

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antirez 2017-01-27 16:54:20 +01:00
parent 27e29f4fe6
commit 3a7410a8a6
1 changed files with 250 additions and 100 deletions
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src/ziplist.c
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@ -9,78 +9,149 @@
* ----------------------------------------------------------------------------
*
* ZIPLIST OVERALL LAYOUT
* ======================
*
* The general layout of the ziplist is as follows:
*
* <zlbytes> <zltail> <zllen> <entry> <entry> ... <entry> <zlend>
*
* All fields are stored in little endian.
* NOTE: all fields are stored in little endian, if not specified otherwise.
*
* <uint32_t zlbytes> is an unsigned integer to hold the number of bytes that
* the ziplist occupies. This value needs to be stored to be able to resize the
* entire structure without the need to traverse it first.
* the ziplist occupies, including the four bytes of the zlbytes field itself.
* This value needs to be stored to be able to resize the entire structure
* without the need to traverse it first.
*
* <uint32_t zltail> is the offset to the last entry in the list. This allows
* a pop operation on the far side of the list without the need for full
* traversal.
*
* <uint16_t zllen> is the number of entries. When this value is larger
* than 2^16-2, we need to traverse the entire list to know how many items it
* holds.
* <uint16_t zllen> is the number of entries. When there are more than
* 2^16-2 entires, this value is set to 2^16-1 and we need to traverse the
* entire list to know how many items it holds.
*
* <uint8_t zlend> is a single byte special value, equal to 255, which
* indicates the end of the list.
* <uint8_t zlend> is a special entry representing the end of the ziplist.
* Is encoded as a single byte equal to 255. No other normal entry starts
* with a byte set to the value of 255.
*
* ZIPLIST ENTRIES
* ===============
*
* Every entry in the ziplist is prefixed by a header that contains two pieces
* Every entry in the ziplist is prefixed by metadata that contains two pieces
* of information. First, the length of the previous entry is stored to be
* able to traverse the list from back to front. Second, the encoding with an
* optional string length of the entry itself is stored.
* able to traverse the list from back to front. Second, the entry encoding is
* provided. It represents the entry type, integer or string, and in the case
* of strings it also represents the length of the string payload.
* So a complete entry is stored like this:
*
* The length of the previous entry is encoded in the following way:
* If this length is smaller than 254 bytes, it will only consume a single
* byte that takes the length as value. When the length is greater than or
* equal to 254, it will consume 5 bytes. The first byte is set to 254 to
* indicate a larger value is following. The remaining 4 bytes take the
* length of the previous entry as value.
* <prevlen> <encoding> <entry-data>
*
* The other header field of the entry itself depends on the contents of the
* entry. When the entry is a string, the first 2 bits of this header will hold
* the type of encoding used to store the length of the string, followed by the
* actual length of the string. When the entry is an integer the first 2 bits
* are both set to 1. The following 2 bits are used to specify what kind of
* integer will be stored after this header. An overview of the different
* types and encodings is as follows:
* Sometimes the encoding represents the entry itself, like for small integers
* as we'll see later. In such a case the <entry-data> part is missing, and we
* could have just:
*
* <prevlen> <encoding>
*
* The length of the previous entry, <prevlen>, is encoded in the following way:
* If this length is smaller than 255 bytes, it will only consume a single
* byte representing the length as an unsinged 8 bit integer. When the length
* is greater than or equal to 255, it will consume 5 bytes. The first byte is
* set to 255 (FF) to indicate a larger value is following. The remaining 4
* bytes take the length of the previous entry as value.
*
* So practically an entry is encoded in the following way:
*
* <prevlen from 0 to 254> <encoding> <entry>
*
* Or alternatively if the previous entry length is greater than 254 bytes
* the following encoding is used:
*
* 0xFF <4 bytes unsigned little endian prevlen> <encoding> <entry>
*
* The encoding field of the entry depends on the content of the
* entry. When the entry is a string, the first 2 bits of the encoding first
* byte will hold the type of encoding used to store the length of the string,
* followed by the actual length of the string. When the entry is an integer
* the first 2 bits are both set to 1. The following 2 bits are used to specify
* what kind of integer will be stored after this header. An overview of the
* different types and encodings is as follows. The first byte is always enough
* to determine the kind of entry.
*
* |00pppppp| - 1 byte
* String value with length less than or equal to 63 bytes (6 bits).
* "pppppp" represents the unsigned 6 bit length.
* |01pppppp|qqqqqqqq| - 2 bytes
* String value with length less than or equal to 16383 bytes (14 bits).
* |10______|qqqqqqqq|rrrrrrrr|ssssssss|tttttttt| - 5 bytes
* IMPORTANT: The 14 bit number is stored in big endian.
* |10000000|qqqqqqqq|rrrrrrrr|ssssssss|tttttttt| - 5 bytes
* String value with length greater than or equal to 16384 bytes.
* |11000000| - 1 byte
* Only the 4 bytes following the first byte represents the length
* up to 32^2-1. The 6 lower bits of the first byte are not used and
* are set to zero.
* IMPORTANT: The 32 bit number is stored in big endian.
* |11000000| - 3 bytes
* Integer encoded as int16_t (2 bytes).
* |11010000| - 1 byte
* |11010000| - 5 bytes
* Integer encoded as int32_t (4 bytes).
* |11100000| - 1 byte
* |11100000| - 9 bytes
* Integer encoded as int64_t (8 bytes).
* |11110000| - 1 byte
* |11110000| - 4 bytes
* Integer encoded as 24 bit signed (3 bytes).
* |11111110| - 1 byte
* |11111110| - 2 bytes
* Integer encoded as 8 bit signed (1 byte).
* |1111xxxx| - (with xxxx between 0000 and 1101) immediate 4 bit integer.
* Unsigned integer from 0 to 12. The encoded value is actually from
* 1 to 13 because 0000 and 1111 can not be used, so 1 should be
* subtracted from the encoded 4 bit value to obtain the right value.
* |11111111| - End of ziplist.
* |11111111| - End of ziplist special entry.
*
* All the integers are represented in little endian byte order.
* Like for the ziplist header, all the integers are represented in little
* endian byte order, even when this code is compiled in big endian systems.
*
* EXAMPLES OF ACTUAL ZIPLISTS
* ===========================
*
* The following is a ziplist containing the two elements representing
* the strings "2" and "5". It is composed of 15 bytes, that we visually
* split into sections:
*
* [0f 00 00 00] [0c 00 00 00] [02 00] [00 f3] [02 f6] [ff]
* | | | | | |
* zlbytes zltail entries "2" "5" end
*
* The first 4 bytes represent the number 15, that is the number of bytes
* the whole ziplist is composed of. The second 4 bytes are the offset
* at which the last ziplist entry is found, that is 12, in fact the
* last entry, that is "5", is at offset 12 inside the ziplist.
* The next 16 bit integer represents the number of elements inside the
* ziplist, its value is 2 since there are just two elements inside.
* Finally "00 f3" is the first entry representing the number 2. It is
* composed of the previous entry length, which is zero because this is
* our first entry, and the byte F3 which corresponds to the encoding
* |1111xxxx| with xxxx between 0001 and 1101. We need to remove the "F"
* higher order bits 1111, and subtract 1 from the "3", so the entry value
* is "2". The next entry has a prevlen of 02, since the first entry is
* composed of exactly two bytes. The entry itself, F6, is encoded exactly
* like the first entry, and 6-1 = 5, so the value of the entry is 5.
* Finally the special entry FF signals the end of the ziplist.
*
* Adding another element to the above string with the value "Hello World"
* allows us to show how the ziplist encodes small strings. We'll just show
* the hex dump of the entry itself. Imagine the bytes as following the
* entry that stores "5" in the ziplist above:
*
* [02] [0b] [48 65 6c 6c 6f 20 57 6f 72 6c 64]
*
* The first byte, 02, is the length of the previous entry. The next
* byte represents the encoding in the pattern |00pppppp| that means
* that the entry is a string of length <pppppp>, so 0B means that
* an 11 bytes string follows. From the third byte (48) to the last (64)
* there are just the ASCII characters for "Hello World".
*
* ----------------------------------------------------------------------------
*
* Copyright (c) 2009-2012, Pieter Noordhuis <pcnoordhuis at gmail dot com>
* Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
* Copyright (c) 2009-2017, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -119,8 +190,13 @@
#include "endianconv.h"
#include "redisassert.h"
#define ZIP_END 255
#define ZIP_BIGLEN 254
#define ZIP_END 255 /* Special "end of ziplist" entry. */
#define ZIP_BIG_PREVLEN 254 /* Max number of bytes of the previous entry, for
the "prevlen" field prefixing each entry, to be
represented with just a single byte. Otherwise
it is represented as FF AA BB CC DD, where
AA BB CC DD are a 4 bytes unsigned integer
representing the previous entry len. */
/* Different encoding/length possibilities */
#define ZIP_STR_MASK 0xc0
@ -133,41 +209,83 @@
#define ZIP_INT_64B (0xc0 | 2<<4)
#define ZIP_INT_24B (0xc0 | 3<<4)
#define ZIP_INT_8B 0xfe
/* 4 bit integer immediate encoding */
#define ZIP_INT_IMM_MASK 0x0f
/* 4 bit integer immediate encoding |1111xxxx| with xxxx between
* 0001 and 1101. */
#define ZIP_INT_IMM_MASK 0x0f /* Mask to extract the 4 bits value. To add
one is needed to reconstruct the value. */
#define ZIP_INT_IMM_MIN 0xf1 /* 11110001 */
#define ZIP_INT_IMM_MAX 0xfd /* 11111101 */
#define ZIP_INT_IMM_VAL(v) (v & ZIP_INT_IMM_MASK)
#define INT24_MAX 0x7fffff
#define INT24_MIN (-INT24_MAX - 1)
/* Macro to determine type */
/* Macro to determine if the entry is a string. String entries never start
* with "11" as most significant bits of the first byte. */
#define ZIP_IS_STR(enc) (((enc) & ZIP_STR_MASK) < ZIP_STR_MASK)
/* Utility macros */
/* Utility macros.*/
/* Return total bytes a ziplist is composed of. */
#define ZIPLIST_BYTES(zl) (*((uint32_t*)(zl)))
/* Return the offset of the last item inside the ziplist. */
#define ZIPLIST_TAIL_OFFSET(zl) (*((uint32_t*)((zl)+sizeof(uint32_t))))
/* Return the length of a ziplist, or UINT16_MAX if the length cannot be
* determined without scanning the whole ziplist. */
#define ZIPLIST_LENGTH(zl) (*((uint16_t*)((zl)+sizeof(uint32_t)*2)))
/* The size of a ziplist header: two 32 bit integers for the total
* bytes count and last item offset. One 16 bit integer for the number
* of items field. */
#define ZIPLIST_HEADER_SIZE (sizeof(uint32_t)*2+sizeof(uint16_t))
/* Size of the "end of ziplist" entry. Just one byte. */
#define ZIPLIST_END_SIZE (sizeof(uint8_t))
/* Return the pointer to the first entry of a ziplist. */
#define ZIPLIST_ENTRY_HEAD(zl) ((zl)+ZIPLIST_HEADER_SIZE)
/* Return the pointer to the last entry of a ziplist, using the
* last entry offset inside the ziplist header. */
#define ZIPLIST_ENTRY_TAIL(zl) ((zl)+intrev32ifbe(ZIPLIST_TAIL_OFFSET(zl)))
/* Return the pointer to the last byte of a ziplist, which is, the
* end of ziplist FF entry. */
#define ZIPLIST_ENTRY_END(zl) ((zl)+intrev32ifbe(ZIPLIST_BYTES(zl))-1)
/* We know a positive increment can only be 1 because entries can only be
* pushed one at a time. */
/* Increment the number of items field in the ziplist header. Note that this
* macro should never overflow the unsigned 16 bit integer, since entires are
* always pushed one at a time. When UINT16_MAX is reached we want the count
* to stay there to signal that a full scan is needed to get the number of
* items inside the ziplist. */
#define ZIPLIST_INCR_LENGTH(zl,incr) { \
if (ZIPLIST_LENGTH(zl) < UINT16_MAX) \
ZIPLIST_LENGTH(zl) = intrev16ifbe(intrev16ifbe(ZIPLIST_LENGTH(zl))+incr); \
}
/* We use this function to receive information about a ziplist entry.
* Note that this is not how the data is actually encoded, is just what we
* get filled by a function in order to operate more easily. */
typedef struct zlentry {
unsigned int prevrawlensize, prevrawlen;
unsigned int lensize, len;
unsigned int headersize;
unsigned char encoding;
unsigned char *p;
unsigned int prevrawlensize; /* Bytes used to encode the previos entry len*/
unsigned int prevrawlen; /* Previous entry len. */
unsigned int lensize; /* Bytes used to encode this entry type/len.
For example strings have a 1, 2 or 5 bytes
header. Integers always use a single byte.*/
unsigned int len; /* Bytes used to represent the actual entry.
For strings this is just the string length
while for integers it is 1, 2, 3, 4, 8 or
0 (for 4 bit immediate) depending on the
number range. */
unsigned int headersize; /* prevrawlensize + lensize. */
unsigned char encoding; /* Set to ZIP_STR_* or ZIP_INT_* depending on
the entry encoding. However for 4 bits
immediate integers this can assume a range
of values and must be range-checked. */
unsigned char *p; /* Pointer to the very start of the entry, that
is, this points to prev-entry-len field. */
} zlentry;
#define ZIPLIST_ENTRY_ZERO(zle) { \
@ -178,15 +296,13 @@ typedef struct zlentry {
}
/* Extract the encoding from the byte pointed by 'ptr' and set it into
* 'encoding'. */
* 'encoding' field of the zlentry structure. */
#define ZIP_ENTRY_ENCODING(ptr, encoding) do { \
(encoding) = (ptr[0]); \
if ((encoding) < ZIP_STR_MASK) (encoding) &= ZIP_STR_MASK; \
} while(0)
void ziplistRepr(unsigned char *zl);
/* Return bytes needed to store integer encoded by 'encoding' */
/* Return bytes needed to store integer encoded by 'encoding'. */
unsigned int zipIntSize(unsigned char encoding) {
switch(encoding) {
case ZIP_INT_8B: return 1;
@ -194,15 +310,26 @@ unsigned int zipIntSize(unsigned char encoding) {
case ZIP_INT_24B: return 3;
case ZIP_INT_32B: return 4;
case ZIP_INT_64B: return 8;
default: return 0; /* 4 bit immediate */
}
assert(NULL);
if (encoding >= ZIP_INT_IMM_MIN && encoding <= ZIP_INT_IMM_MAX)
return 0; /* 4 bit immediate */
panic("Invalid integer encoding 0x%02X", encoding);
return 0;
}
/* Encode the length 'rawlen' writing it in 'p'. If p is NULL it just returns
* the amount of bytes required to encode such a length. */
unsigned int zipEncodeLength(unsigned char *p, unsigned char encoding, unsigned int rawlen) {
/* Write the encoidng header of the entry in 'p'. If p is NULL it just returns
* the amount of bytes required to encode such a length. Arguments:
*
* 'encoding' is the encoding we are using for the entry. It could be
* ZIP_INT_* or ZIP_STR_* or between ZIP_INT_IMM_MIN and ZIP_INT_IMM_MAX
* for single-byte small immediate integers.
*
* 'rawlen' is only used for ZIP_STR_* encodings and is the length of the
* srting that this entry represents.
*
* The function returns the number of bytes used by the encoding/length
* header stored in 'p'. */
unsigned int zipStoreEntryEncoding(unsigned char *p, unsigned char encoding, unsigned int rawlen) {
unsigned char len = 1, buf[5];
if (ZIP_IS_STR(encoding)) {
@ -231,15 +358,16 @@ unsigned int zipEncodeLength(unsigned char *p, unsigned char encoding, unsigned
buf[0] = encoding;
}
/* Store this length at p */
/* Store this length at p. */
memcpy(p,buf,len);
return len;
}
/* Decode the length encoded in 'ptr'. The 'encoding' variable will hold the
* entries encoding, the 'lensize' variable will hold the number of bytes
* required to encode the entries length, and the 'len' variable will hold the
* entries length. */
/* Decode the entry encoding type and data length (string length for strings,
* number of bytes used for the integer for integer entries) encoded in 'ptr'.
* The 'encoding' variable will hold the entry encoding, the 'lensize'
* variable will hold the number of bytes required to encode the entry
* length, and the 'len' variable will hold the entry length. */
#define ZIP_DECODE_LENGTH(ptr, encoding, lensize, len) do { \
ZIP_ENTRY_ENCODING((ptr), (encoding)); \
if ((encoding) < ZIP_STR_MASK) { \
@ -256,7 +384,7 @@ unsigned int zipEncodeLength(unsigned char *p, unsigned char encoding, unsigned
((ptr)[3] << 8) | \
((ptr)[4]); \
} else { \
assert(NULL); \
panic("Invalid string encoding 0x%02X", (encoding)); \
} \
} else { \
(lensize) = 1; \
@ -264,45 +392,49 @@ unsigned int zipEncodeLength(unsigned char *p, unsigned char encoding, unsigned
} \
} while(0);
/* Encode the length of the previous entry and write it to "p". This only
* uses the larger encoding (required in __ziplistCascadeUpdate). */
int zipStorePrevEntryLengthLarge(unsigned char *p, unsigned int len) {
if (p != NULL) {
p[0] = ZIP_BIG_PREVLEN;
memcpy(p+1,&len,sizeof(len));
memrev32ifbe(p+1);
}
return 1+sizeof(len);
}
/* Encode the length of the previous entry and write it to "p". Return the
* number of bytes needed to encode this length if "p" is NULL. */
unsigned int zipPrevEncodeLength(unsigned char *p, unsigned int len) {
unsigned int zipStorePrevEntryLength(unsigned char *p, unsigned int len) {
if (p == NULL) {
return (len < ZIP_BIGLEN) ? 1 : sizeof(len)+1;
return (len < ZIP_BIG_PREVLEN) ? 1 : sizeof(len)+1;
} else {
if (len < ZIP_BIGLEN) {
if (len < ZIP_BIG_PREVLEN) {
p[0] = len;
return 1;
} else {
p[0] = ZIP_BIGLEN;
memcpy(p+1,&len,sizeof(len));
memrev32ifbe(p+1);
return 1+sizeof(len);
return zipStorePrevEntryLengthLarge(p,len);
}
}
}
/* Encode the length of the previous entry and write it to "p". This only
* uses the larger encoding (required in __ziplistCascadeUpdate). */
void zipPrevEncodeLengthForceLarge(unsigned char *p, unsigned int len) {
if (p == NULL) return;
p[0] = ZIP_BIGLEN;
memcpy(p+1,&len,sizeof(len));
memrev32ifbe(p+1);
}
/* Decode the number of bytes required to store the length of the previous
* element, from the perspective of the entry pointed to by 'ptr'. */
/* Return the number of bytes used to encode the length of the previous
* entry. The length is returned by setting the var 'prevlensize'. */
#define ZIP_DECODE_PREVLENSIZE(ptr, prevlensize) do { \
if ((ptr)[0] < ZIP_BIGLEN) { \
if ((ptr)[0] < ZIP_BIG_PREVLEN) { \
(prevlensize) = 1; \
} else { \
(prevlensize) = 5; \
} \
} while(0);
/* Decode the length of the previous element, from the perspective of the entry
* pointed to by 'ptr'. */
/* Return the length of the previous element, and the number of bytes that
* are used in order to encode the previous element length.
* 'ptr' must point to the prevlen prefix of an entry (that encodes the
* length of the previos entry in order to navigate the elements backward).
* The length of the previous entry is stored in 'prevlen', the number of
* bytes needed to encode the previous entry length are stored in
* 'prevlensize'. */
#define ZIP_DECODE_PREVLEN(ptr, prevlensize, prevlen) do { \
ZIP_DECODE_PREVLENSIZE(ptr, prevlensize); \
if ((prevlensize) == 1) { \
@ -314,12 +446,25 @@ void zipPrevEncodeLengthForceLarge(unsigned char *p, unsigned int len) {
} \
} while(0);
/* Return the difference in number of bytes needed to store the length of the
* previous element 'len', in the entry pointed to by 'p'. */
/* Given a pointer 'p' to the prevlen info that prefixes an entry, this
* function returns the difference in number of bytes needed to encode
* the prevlen if the previous entry changes of size.
*
* So if A is the number of bytes used right now to encode the 'prevlen'
* field.
*
* And B is the number of bytes that are needed in order to encode the
* 'prevlen' if the previous element will be updated to one of size 'len'.
*
* Then the function returns B - A
*
* So the function returns a positive number if more space is needed,
* a negative number if less space is needed, or zero if the same space
* is needed. */
int zipPrevLenByteDiff(unsigned char *p, unsigned int len) {
unsigned int prevlensize;
ZIP_DECODE_PREVLENSIZE(p, prevlensize);
return zipPrevEncodeLength(NULL, len) - prevlensize;
return zipStorePrevEntryLength(NULL, len) - prevlensize;
}
/* Return the total number of bytes used by the entry pointed to by 'p'. */
@ -456,8 +601,8 @@ unsigned char *ziplistResize(unsigned char *zl, unsigned int len) {
* causes a realloc and memmove). However, encoding the prevlen may require
* that this entry is grown as well. This effect may cascade throughout
* the ziplist when there are consecutive entries with a size close to
* ZIP_BIGLEN, so we need to check that the prevlen can be encoded in every
* consecutive entry.
* ZIP_BIG_PREVLEN, so we need to check that the prevlen can be encoded in
* every consecutive entry.
*
* Note that this effect can also happen in reverse, where the bytes required
* to encode the prevlen field can shrink. This effect is deliberately ignored,
@ -477,7 +622,7 @@ unsigned char *__ziplistCascadeUpdate(unsigned char *zl, unsigned char *p) {
while (p[0] != ZIP_END) {
zipEntry(p, &cur);
rawlen = cur.headersize + cur.len;
rawlensize = zipPrevEncodeLength(NULL,rawlen);
rawlensize = zipStorePrevEntryLength(NULL,rawlen);
/* Abort if there is no next entry. */
if (p[rawlen] == ZIP_END) break;
@ -508,7 +653,7 @@ unsigned char *__ziplistCascadeUpdate(unsigned char *zl, unsigned char *p) {
memmove(np+rawlensize,
np+next.prevrawlensize,
curlen-noffset-next.prevrawlensize-1);
zipPrevEncodeLength(np,rawlen);
zipStorePrevEntryLength(np,rawlen);
/* Advance the cursor */
p += rawlen;
@ -517,9 +662,9 @@ unsigned char *__ziplistCascadeUpdate(unsigned char *zl, unsigned char *p) {
if (next.prevrawlensize > rawlensize) {
/* This would result in shrinking, which we want to avoid.
* So, set "rawlen" in the available bytes. */
zipPrevEncodeLengthForceLarge(p+rawlen,rawlen);
zipStorePrevEntryLengthLarge(p+rawlen,rawlen);
} else {
zipPrevEncodeLength(p+rawlen,rawlen);
zipStorePrevEntryLength(p+rawlen,rawlen);
}
/* Stop here, as the raw length of "next" has not changed. */
@ -542,7 +687,7 @@ unsigned char *__ziplistDelete(unsigned char *zl, unsigned char *p, unsigned int
deleted++;
}
totlen = p-first.p;
totlen = p-first.p; /* Bytes taken by the element(s) to delete. */
if (totlen > 0) {
if (p[0] != ZIP_END) {
/* Storing `prevrawlen` in this entry may increase or decrease the
@ -550,8 +695,13 @@ unsigned char *__ziplistDelete(unsigned char *zl, unsigned char *p, unsigned int
* There always is room to store this, because it was previously
* stored by an entry that is now being deleted. */
nextdiff = zipPrevLenByteDiff(p,first.prevrawlen);
/* Note that there is always space when p jumps backward: if
* the new previous entry is large, one of the deleted elements
* had a 5 bytes prevlen header, so there is for sure at least
* 5 bytes free and we need just 4. */
p -= nextdiff;
zipPrevEncodeLength(p,first.prevrawlen);
zipStorePrevEntryLength(p,first.prevrawlen);
/* Update offset for tail */
ZIPLIST_TAIL_OFFSET(zl) =
@ -616,14 +766,14 @@ unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, unsigned cha
/* 'encoding' is set to the appropriate integer encoding */
reqlen = zipIntSize(encoding);
} else {
/* 'encoding' is untouched, however zipEncodeLength will use the
/* 'encoding' is untouched, however zipStoreEntryEncoding will use the
* string length to figure out how to encode it. */
reqlen = slen;
}
/* We need space for both the length of the previous entry and
* the length of the payload. */
reqlen += zipPrevEncodeLength(NULL,prevlen);
reqlen += zipEncodeLength(NULL,encoding,slen);
reqlen += zipStorePrevEntryLength(NULL,prevlen);
reqlen += zipStoreEntryEncoding(NULL,encoding,slen);
/* When the insert position is not equal to the tail, we need to
* make sure that the next entry can hold this entry's length in
@ -641,7 +791,7 @@ unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, unsigned cha
memmove(p+reqlen,p-nextdiff,curlen-offset-1+nextdiff);
/* Encode this entry's raw length in the next entry. */
zipPrevEncodeLength(p+reqlen,reqlen);
zipStorePrevEntryLength(p+reqlen,reqlen);
/* Update offset for tail */
ZIPLIST_TAIL_OFFSET(zl) =
@ -669,8 +819,8 @@ unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, unsigned cha
}
/* Write the entry */
p += zipPrevEncodeLength(p,prevlen);
p += zipEncodeLength(p,encoding,slen);
p += zipStorePrevEntryLength(p,prevlen);
p += zipStoreEntryEncoding(p,encoding,slen);
if (ZIP_IS_STR(encoding)) {
memcpy(p,s,slen);
} else {