redis原始碼分析（八）、redis資料結構之壓縮ziplist--------ziplist.c ziplist.h學習筆記
一、介紹ziplist
/* The ziplist is a specially encoded dually linked list that is designed
* to be very memory efficient.
* Ziplist 是為了儘可能節約記憶體而設計相當特許的雙端佇列
*It stores both strings and integer values,where integers are encoded as
*actual integers instead of a series ofcharacters.
*Ziplist 能儲存strings和integer值，整型值被儲存為實際的整型值而不是字元陣列。
*It allows push and pop operations on either side of the list
* in O(1) time. However, because every operation requires a reallocation of
* the memory used by the ziplist, the actual complexity is related to the
* amount of memory used by the ziplist.
*Ziplist 在頭部和尾部的操作時間0（1），ziplist的操作都需要重新分配記憶體，所以
*實際的複雜度和ziplist的使用和記憶體有關。二、ziplist結構
<zlbytes> <zltail> <zllen> <entry> <entry> ...... <entry> <zlend>
|-----ziplist header--------|----------entry---------------|--end--|zlbytes: 4位元組，是一個無符號整數，儲存著 ziplist 使用的記憶體數量。通過這個值，程式可以直接對 ziplist 的記憶體大小進行調整，而無須為了計算ziplist的記憶體大小而遍歷整個列表。
zltail: 4位元組，儲存著到達列表中最後一個節點的偏移量。這個偏移量使得對錶尾的操作可以在無須遍歷整個列表的情況下進行。
zllen: 2位元組，儲存著列表中的節點數量。當 zllen 儲存的值大於 2**16-2時程式需要遍歷整個列表才能知道列表實際包含了多少個節點。
zlend: 1位元組，值為 255 ，標識列表的末尾。
/*
空白 ziplist 示例圖
area |<---- ziplist header ---->|<-- end -->|
size 4 bytes 4 bytes 2 bytes 1 byte
+---------+--------+-------+-----------+
component | zlbytes | zltail | zllen | zlend |
| | | | |
value | 1011 | 1010 | 0 | 1111 1111 |
+---------+--------+-------+-----------+
^
|
ZIPLIST_ENTRY_HEAD
&
address ZIPLIST_ENTRY_TAIL
&
ZIPLIST_ENTRY_END
非空 ziplist 示例圖
area |<---- ziplist header ---->|<----------- entries ------------->|<-end->|
size 4 bytes 4 bytes 2 bytes ? ? ? ? 1 byte
+---------+--------+-------+--------+--------+--------+--------+-------+
component | zlbytes | zltail | zllen | entry1 | entry2 | ... | entryN | zlend |
+---------+--------+-------+--------+--------+--------+--------+-------+
^ ^ ^
address | | |
ZIPLIST_ENTRY_HEAD | ZIPLIST_ENTRY_END
|
ZIPLIST_ENTRY_TAIL
*/ziplist節點定義如下：
/*
* 儲存 ziplist 節點資訊的結構
*/
typedef struct zlentry {
// prevrawlen ：前置節點的長度
// prevrawlensize ：編碼 prevrawlen 所需的位元組大小
unsigned int prevrawlensize, prevrawlen;
// len ：當前節點值的長度
// lensize ：編碼 len 所需的位元組大小
unsigned int lensize, len;
// 當前節點 header 的大小
// 等於 prevrawlensize + lensize
unsigned int headersize;
// 當前節點值所使用的編碼型別
unsigned char encoding;
// 指向當前節點的指標
unsigned char *p;
} zlentry;可以看出zlentry的屬性還是比較多的。實際上，ziplist在儲存節點資訊時，並沒有將zlentry資料結構所有屬性儲存，而是做了簡化：
| prevlen | encode & len | value |
|---|
prevlen： 表示前一個zlentry的長度
encode&len: 本節點的儲存的值是int還是string
value：本節點的值
注意：encode：00 01 10 表示本節點儲存的value是string型別
11表示本節點儲存的value是 int 型別
/*
* 字串編碼型別
*/
#define ZIP_STR_06B (0 << 6)
#define ZIP_STR_14B (1 << 6)
#define ZIP_STR_32B (2 << 6)zlentry為字串的時候encode/len編碼規則如下：
| encoding | 佔用位元組 | 存貯結構encode/len | 字串長度範圍 | len取值 |
|---|---|---|---|---|
| ZIP_STR_06B | 1位元組 | 00XXXXXX | 長度<64 | 後6位 |
| ZIP_STR_14B | 2位元組 | 01XXXXXX XXXXXXXX | 長度<16384 | 後14位 |
| ZIP_STR_32B | 5位元組 | 10000000 XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX | 長度<2^32-1 | 32位 |
prevlen 前置節點的長度
小於254 1 00xxxxxx（用1個位元組表示）
大於或等於254 5 11111110 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx （5個位元組表示）
/*
* ziplist 末端識別符號，以及 5 位元組長長度識別符號
*/
#define ZIP_END 255
#define ZIP_BIGLEN 254由於整型的長度是固定的，因此 只需儲存encoding資訊，length值可根據編碼進行計算得出。
| encoding | 佔用位元組 | 儲存結構 | 取值範圍 |
|---|---|---|---|
| ZIP_INT_XX | 1位元組 | 11 11 0001~11111101 | 0~12 |
| ZIP_INT_8B | 1位元組 | 11 11 1110 | -28~28-1 |
| ZIP_INT_16B | 2位元組 | 11 00 0000 | -216~216-1 |
| ZIP_INT_24B | 3位元組 | 11 11 0000 | -224~224-1 |
| ZIP_INT_32B | 4位元組 | 11 01 0000 | -232~232-1 |
| ZIP_INT_64B | 8位元組 | 11 10 0000 | -264~264-1 |
/*
* 整數編碼型別
*/
#define ZIP_INT_16B (0xc0 | 0<<4) ----> 11 00 0000 -2^16~2^16-1
#define ZIP_INT_32B (0xc0 | 1<<4) ----> 11 01 0000 -2^32~2^32-1
#define ZIP_INT_64B (0xc0 | 2<<4) ----> 11 10 0000 -2^64~2^64-1
#define ZIP_INT_24B (0xc0 | 3<<4) ----> 11 11 0000 -2^24~2^24-1
#define ZIP_INT_8B 0xfe ----> 11 11 1110 -2^8~2^8-1
#define ZIP_INT_IMM_MIN 0xf1 /* 11110001 */
#define ZIP_INT_IMM_MAX 0xfd /* 11111101 */
0-------12 1111xxxx 11110001~11111101
0000 and 1111都被佔用了，不能使用
0xfe -->1110 被用來表示 ZIP_INT_8B 編碼
我想問 13 14 15 是用什麼來表示？被劃分在 ZIP_INT_8B ？emmmm 應該就是這樣解釋如下：
* 如果節點儲存的是整數值，
* 那麼這部分 header 的頭 2 位都將被設定為 1 ，
* 而之後跟著的 2 位則用於標識節點所儲存的整數的型別。
*
* |11000000| - 1 byte
* Integer encoded as int16_t (2 bytes).
* 節點的值為 int16_t 型別的整數，長度為 2 位元組。
* |11010000| - 1 byte
* Integer encoded as int32_t (4 bytes).
* 節點的值為 int32_t 型別的整數，長度為 4 位元組。
* |11100000| - 1 byte
* Integer encoded as int64_t (8 bytes).
* 節點的值為 int64_t 型別的整數，長度為 8 位元組。
* |11110000| - 1 byte
* Integer encoded as 24 bit signed (3 bytes).
* 節點的值為 24 位（3 位元組）長的整數。
* |11111110| - 1 byte
* Integer encoded as 8 bit signed (1 byte).
* 節點的值為 8 位（1 位元組）長的整數。
* |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.
* 節點的值為介於 0 至 12 之間的無符號整數。
* 因為 0000 和 1111 都不能使用，所以位的實際值將是 1 至 13 。
* 程式在取得這 4 個位的值之後，還需要減去 1 ，才能計算出正確的值。
* 比如說，如果位的值為 0001 = 1 ，那麼程式返回的值將是 1 - 1 = 0 。/* 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)
很清楚意思就是計算valued是否為11 因為string的型別編碼不可能是11，所以其意思就是計算value的型別是否為string/* Utility macros.*/
/* Return total bytes a ziplist is composed of. */
// 定位到 ziplist 的 bytes 屬性，該屬性記錄了整個 ziplist 所佔用的記憶體位元組數
// 用於取出 bytes 屬性的現有值，或者為 bytes 屬性賦予新值
#define ZIPLIST_BYTES(zl) (*((uint32_t*)(zl))) //zlbytes
/* Return the offset of the last item inside the ziplist. */
// 定位到 ziplist 的 offset 屬性，該屬性記錄了到達表尾節點的偏移量
// 用於取出 offset 屬性的現有值，或者為 offset 屬性賦予新值
#define ZIPLIST_TAIL_OFFSET(zl) (*((uint32_t*)((zl)+sizeof(uint32_t)))) //zltail
/* Return the length of a ziplist, or UINT16_MAX if the length cannot be
* determined without scanning the whole ziplist. */
// 定位到 ziplist 的 length 屬性，該屬性記錄了 ziplist 包含的節點數量
// 用於取出 length 屬性的現有值，或者為 length 屬性賦予新值
#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. */
// 返回 ziplist 表頭的大小
#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. */
// 返回指向 ziplist 第一個節點（的起始位置）的指標
#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. */
// 返回指向 ziplist 最後一個節點（的起始位置）的指標
#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. */
// 返回指向 ziplist 末端 ZIP_END （的起始位置）的指標
#define ZIPLIST_ENTRY_END(zl) ((zl)+intrev32ifbe(ZIPLIST_BYTES(zl))-1)增加 ziplist 的節點數 T = O(1)
#define ZIPLIST_INCR_LENGTH(zl,incr) { \
if (ZIPLIST_LENGTH(zl) < UINT16_MAX) \
ZIPLIST_LENGTH(zl) = intrev16ifbe(intrev16ifbe(ZIPLIST_LENGTH(zl))+incr); \
}/* Extract the encoding from the byte pointed by 'ptr' and set it into
* 'encoding'.
*
* 從 ptr 中取出節點值的編碼型別，並將它儲存到 encoding 變數中。
*
* T = O(1)
*/
#define ZIP_ENTRY_ENCODING(ptr, encoding) do { \
(encoding) = (ptr[0]); \
if ((encoding) < ZIP_STR_MASK) (encoding) &= ZIP_STR_MASK; \
} while(0)/* Return bytes needed to store integer encoded by 'encoding'
*
* 返回儲存 encoding 編碼的值所需的位元組數量
*
* T = O(1)
*/
static unsigned int zipIntSize(unsigned char encoding) {
switch(encoding) {
case ZIP_INT_8B: return 1;
case ZIP_INT_16B: return 2;
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);
return 0;
}/* The ziplist is a specially encoded dually linked list that is designed
* to be very memory efficient.
* Ziplist 是為了儘可能節約記憶體而設計雙端佇列
*It stores both strings and integer values,where integers are encoded as
*actual integers instead of a series ofcharacters.
*Ziplist 能儲存strings和integer值，整型值被儲存為實際的整型值而不是字元陣列。
*It allows push and pop operations on either side of the list
* in O(1) time. However, because every operation requires a reallocation of
* the memory used by the ziplist, the actual complexity is related to the
* amount of memory used by the ziplist.
*Ziplist 在頭部和尾部的操作時間0（1），ziplist的操作都需要重新分配記憶體，所以
*實際的複雜度和ziplist的使用記憶體有關。
* ----------------------------------------------------------------------------
*
* ZIPLIST OVERALL LAYOUT
* ======================
*
* The general layout of the ziplist is as follows:
*
* <zlbytes> <zltail> <zllen> <entry> <entry> ...... <entry><zlend>
* |-----ziplist header--------|----------entry---------------|--end--|
*
* zlbytes: 4位元組，是一個無符號整數，儲存著 ziplist 使用的記憶體數量。
*
* zltail: 4位元組，儲存著到達列表中最後一個節點的偏移量。
* 這個偏移量使得對錶尾的 pop 操作可以在無須遍歷整個列表的情況下進行。
*
* zllen: 2位元組，儲存著列表中的節點數量。當 zllen 儲存的值大於 2**16-2 時，
* 程式需要遍歷整個列表才能知道列表實際包含了多少個節點。
*
* zlend: 1位元組，值為 255 ，標識列表的末尾。
* 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, 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 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 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 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 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:
*
* <prevlen> <encoding> <entry-data>
*
* 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).
* 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.
* 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| - 5 bytes
* Integer encoded as int32_t (4 bytes).
* |11100000| - 9 bytes
* Integer encoded as int64_t (8 bytes).
* |11110000| - 4 bytes
* Integer encoded as 24 bit signed (3 bytes).
* |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 special entry.
*
* 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) 2009-2017, Salvatore Sanfilippo <antirez at gmail dot com>
* 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <limits.h>
#include "zmalloc.h"
#include "util.h"
#include "ziplist.h"
#include "endianconv.h"
#include "redisassert.h"
#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
#define ZIP_INT_MASK 0x30
#define ZIP_STR_06B (0 << 6)
#define ZIP_STR_14B (1 << 6)
#define ZIP_STR_32B (2 << 6)
#define ZIP_INT_16B (0xc0 | 0<<4)
#define ZIP_INT_32B (0xc0 | 1<<4)
#define ZIP_INT_64B (0xc0 | 2<<4)
#define ZIP_INT_24B (0xc0 | 3<<4)
#define ZIP_INT_8B 0xfe
/* 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 INT24_MAX 0x7fffff
#define INT24_MIN (-INT24_MAX - 1)
/* 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.*/
/* Return total bytes a ziplist is composed of. */
// 定位到 ziplist 的 bytes 屬性，該屬性記錄了整個 ziplist 所佔用的記憶體位元組數
// 用於取出 bytes 屬性的現有值，或者為 bytes 屬性賦予新值
#define ZIPLIST_BYTES(zl) (*((uint32_t*)(zl))) //zlbytes
/* Return the offset of the last item inside the ziplist. */
// 定位到 ziplist 的 offset 屬性，該屬性記錄了到達表尾節點的偏移量
// 用於取出 offset 屬性的現有值，或者為 offset 屬性賦予新值
#define ZIPLIST_TAIL_OFFSET(zl) (*((uint32_t*)((zl)+sizeof(uint32_t)))) //zltail
/* Return the length of a ziplist, or UINT16_MAX if the length cannot be
* determined without scanning the whole ziplist. */
// 定位到 ziplist 的 length 屬性，該屬性記錄了 ziplist 包含的節點數量
// 用於取出 length 屬性的現有值，或者為 length 屬性賦予新值
#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. */
// 返回 ziplist 表頭的大小
#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. */
// 返回指向 ziplist 第一個節點（的起始位置）的指標
#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. */
// 返回指向 ziplist 最後一個節點（的起始位置）的指標
#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. */
// 返回指向 ziplist 末端 ZIP_END （的起始位置）的指標
#define ZIPLIST_ENTRY_END(zl) ((zl)+intrev32ifbe(ZIPLIST_BYTES(zl))-1)
/* 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.
* 增加 ziplist 的節點數
*
* T = O(1)
*/
#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; /* 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) { \
(zle)->prevrawlensize = (zle)->prevrawlen = 0; \
(zle)->lensize = (zle)->len = (zle)->headersize = 0; \
(zle)->encoding = 0; \
(zle)->p = NULL; \
}
/* Extract the encoding from the byte pointed by 'ptr' and set it into
* 'encoding' field of the zlentry structure.
從指標ptr中取出編碼的值儲存到encding中去
*/
#define ZIP_ENTRY_ENCODING(ptr, encoding) do { \
(encoding) = (ptr[0]); \
if ((encoding) < ZIP_STR_MASK) (encoding) &= ZIP_STR_MASK; \
} while(0)
/* Return bytes needed to store integer encoded by 'encoding'.
value是int的時候 取出int佔用的位元組數
*/
unsigned int zipIntSize(unsigned char encoding) {
switch(encoding) {
case ZIP_INT_8B: return 1;
case ZIP_INT_16B: return 2;
case ZIP_INT_24B: return 3;
case ZIP_INT_32B: return 4;
case ZIP_INT_64B: return 8;
}
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;
}
/* 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'.
* 編碼節點長度值 l ，並將它寫入到 p 中，然後返回編碼 l 所需的位元組數量。
*
* 如果 p 為 NULL ，那麼僅返回編碼 l 所需的位元組數量，不進行寫入。
*
* T = O(1)
*/
//這個函式實際上就是求encode/len的值並返回編碼len的位元組數
unsigned int zipStoreEntryEncoding(unsigned char *p, unsigned char encoding, unsigned int rawlen) {
unsigned char len = 1, buf[5];
//字串編碼
if (ZIP_IS_STR(encoding)) {
/* Although encoding is given it may not be set for strings,
* so we determine it here using the raw length. */
if (rawlen <= 0x3f) { //0x3f = 63
if (!p) return len;
buf[0] = ZIP_STR_06B | rawlen;
} else if (rawlen <= 0x3fff) { //0x3fff = 16383
len += 1;
if (!p) return len;
buf[0] = ZIP_STR_14B | ((rawlen >> 8) & 0x3f);
buf[1] = rawlen & 0xff;
} else { //
len += 4;
if (!p) return len;
buf[0] = ZIP_STR_32B;
buf[1] = (rawlen >> 24) & 0xff;
buf[2] = (rawlen >> 16) & 0xff;
buf[3] = (rawlen >> 8) & 0xff;
buf[4] = rawlen & 0xff;
}
} else {
/* Implies integer encoding, so length is always 1. */
if (!p) return len;
buf[0] = encoding;
}
/* Store this length at p. */
memcpy(p,buf,len);
return len;
}
/* 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.
* 解碼 ptr 指標，取出列表節點的相關資訊，並將它們儲存在以下變數中：
*
* - encoding 儲存節點值的編碼型別。
*
* - lensize 儲存編碼節點長度所需的位元組數。
*
* - len 儲存節點的長度。
*
* T = O(1)
*/
// 整形的只需要encode 而不是encode/len 所以知道encode的值就能知道編碼value需要的位元組數
// 所以整形的時候lensize是固定的值1 因為encode的編碼只需要一個位元組
// 所以zipIntSize 根據encode計算編碼value需要的位元組數
#define ZIP_DECODE_LENGTH(ptr, encoding, lensize, len) do { \
ZIP_ENTRY_ENCODING((ptr), (encoding)); \
if ((encoding) < ZIP_STR_MASK) { \
if ((encoding) == ZIP_STR_06B) { \
(lensize) = 1; \
(len) = (ptr)[0] & 0x3f; \
} else if ((encoding) == ZIP_STR_14B) { \
(lensize) = 2; \
(len) = (((ptr)[0] & 0x3f) << 8) | (ptr)[1]; \
} else if ((encoding) == ZIP_STR_32B) { \
(lensize) = 5; \
(len) = ((ptr)[1] << 24) | \
((ptr)[2] << 16) | \
((ptr)[3] << 8) | \
((ptr)[4]); \
} else { \
panic("Invalid string encoding 0x%02X", (encoding)); \
} \
} else { \
(lensize) = 1; \
(len) = zipIntSize(encoding); \
} \
} while(0);
/* Encode the length of the previous entry and write it to "p". This only
* uses the larger encoding (required in __ziplistCascadeUpdate).
將原本只需要 1 個位元組來儲存的前置節點長度 len 編碼至一個 5 位元組長的 header 中。
*/
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.
* 對前置節點的長度 len 進行編碼，並將它寫入到 p 中，
* 然後返回編碼 len 所需的位元組數量。
*
* 如果 p 為 NULL ，那麼不進行寫入，僅返回編碼 len 所需的位元組數量。
*
* T = O(1)
*
*/
unsigned int zipStorePrevEntryLength(unsigned char *p, unsigned int len) {
if (p == NULL) {
return (len < ZIP_BIG_PREVLEN) ? 1 : sizeof(len)+1; //2的8次方 = 256 len<256的時候編碼len只需要一個位元組
} else {
if (len < ZIP_BIG_PREVLEN) {
p[0] = len;
return 1;
} else {
return zipStorePrevEntryLengthLarge(p,len);
}
}
}
/* Return the number of bytes used to encode the length of the previous
* entry. The length is returned by setting the var 'prevlensize'.
* 解碼 ptr 指標，
* 取出編碼前置節點長度所需的位元組數，並將它儲存到 prevlensize 變數中。
*
* T = O(1)
*/
#define ZIP_DECODE_PREVLENSIZE(ptr, prevlensize) do { \
if ((ptr)[0] < ZIP_BIG_PREVLEN) { \
(prevlensize) = 1; \
} else { \
(prevlensize) = 5; \
} \
} while(0);
/* 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'.
從ptr中取出prevlensize，就是prelen編碼需要的位元組數，儲存到prevlensize。
prelen = ptr[0] 前一個節點的長度
巨集的作用是把上一value的len賦值到下一節點的prelen
*/
#define ZIP_DECODE_PREVLEN(ptr, prevlensize, prevlen) do { \
ZIP_DECODE_PREVLENSIZE(ptr, prevlensize); \
if ((prevlensize) == 1) { \
(prevlen) = (ptr)[0]; \
} else if ((prevlensize) == 5) { \
assert(sizeof((prevlensize)) == 4); \
memcpy(&(prevlen), ((char*)(ptr)) + 1, 4); \
memrev32ifbe(&prevlen); \
} \
} while(0);
/* 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.
* 計算編碼新的前置節點長度 len 所需的位元組數，
* 減去編碼 p 原來的前置節點長度所需的位元組數之差。
*
*/
int zipPrevLenByteDiff(unsigned char *p, unsigned int len) {
unsigned int prevlensize;
ZIP_DECODE_PREVLENSIZE(p, prevlensize); //計算前置節點編碼需要位元組數
return zipStorePrevEntryLength(NULL, len) - prevlensize;
}
/* Return the total number of bytes used by the entry pointed to by 'p'.
* 返回指標 p 所指向的節點佔用的位元組數總和。
*/
unsigned int zipRawEntryLength(unsigned char *p) {
unsigned int prevlensize, encoding, lensize, len;
ZIP_DECODE_PREVLENSIZE(p, prevlensize);
ZIP_DECODE_LENGTH(p + prevlensize, encoding, lensize, len);
return prevlensize + lensize + len;
}
/* Check if string pointed to by 'entry' can be encoded as an integer.
* Stores the integer value in 'v' and its encoding in 'encoding'.
* 檢查 entry 中指向的字串能否被編碼為整數。
*
* 如果可以的話，
* 將編碼後的整數儲存在指標 v 的值中，並將編碼的方式儲存在指標 encoding 的值中。
*
* 注意，這裡的 entry 和前面代表節點的 entry 不是一個意思。
*/
int zipTryEncoding(unsigned char *entry, unsigned int entrylen, long long *v, unsigned char *encoding) {
long long value;
if (entrylen >= 32 || entrylen == 0) return 0;
if (string2ll((char*)entry,entrylen,&value)) {
/* Great, the string can be encoded. Check what's the smallest
* of our encoding types that can hold this value. */
if (value >= 0 && value <= 12) {
*encoding = ZIP_INT_IMM_MIN+value;
} else if (value >= INT8_MIN && value <= INT8_MAX) {
*encoding = ZIP_INT_8B;
} else if (value >= INT16_MIN && value <= INT16_MAX) {
*encoding = ZIP_INT_16B;
} else if (value >= INT24_MIN && value <= INT24_MAX) {
*encoding = ZIP_INT_24B;
} else if (value >= INT32_MIN && value <= INT32_MAX) {
*encoding = ZIP_INT_32B;
} else {
*encoding = ZIP_INT_64B;
}
*v = value;
return 1;
}
return 0;
}
/* Store integer 'value' at 'p', encoded as 'encoding' */
// 根據encoding 把value儲存到p中
void zipSaveInteger(unsigned char *p, int64_t value, unsigned char encoding) {
int16_t i16;
int32_t i32;
int64_t i64;
if (encoding == ZIP_INT_8B) {
((int8_t*)p)[0] = (int8_t)value;
} else if (encoding == ZIP_INT_16B) {
i16 = value;
memcpy(p,&i16,sizeof(i16));
memrev16ifbe(p);
} else if (encoding == ZIP_INT_24B) {
i32 = value<<8;
memrev32ifbe(&i32);
memcpy(p,((uint8_t*)&i32)+1,sizeof(i32)-sizeof(uint8_t));
} else if (encoding == ZIP_INT_32B) {
i32 = value;
memcpy(p,&i32,sizeof(i32));
memrev32ifbe(p);
} else if (encoding == ZIP_INT_64B) {
i64 = value;
memcpy(p,&i64,sizeof(i64));
memrev64ifbe(p);
} else if (encoding >= ZIP_INT_IMM_MIN && encoding <= ZIP_INT_IMM_MAX) {
/* Nothing to do, the value is stored in the encoding itself. */
} else {
assert(NULL);
}
}
/* Read integer encoded as 'encoding' from 'p' */
//根據encoding值讀取value值到p中
int64_t zipLoadInteger(unsigned char *p, unsigned char encoding) {
int16_t i16;
int32_t i32;
int64_t i64, ret = 0;
if (encoding == ZIP_INT_8B) {
ret = ((int8_t*)p)[0];
} else if (encoding == ZIP_INT_16B) {
memcpy(&i16,p,sizeof(i16));
memrev16ifbe(&i16);
ret = i16;
} else if (encoding == ZIP_INT_32B) {
memcpy(&i32,p,sizeof(i32));
memrev32ifbe(&i32);
ret = i32;
} else if (encoding == ZIP_INT_24B) {
i32 = 0;
memcpy(((uint8_t*)&i32)+1,p,sizeof(i32)-sizeof(uint8_t));
memrev32ifbe(&i32);
ret = i32>>8;
} else if (encoding == ZIP_INT_64B) {
memcpy(&i64,p,sizeof(i64));
memrev64ifbe(&i64);
ret = i64;
} else if (encoding >= ZIP_INT_IMM_MIN && encoding <= ZIP_INT_IMM_MAX) {
ret = (encoding & ZIP_INT_IMM_MASK)-1;
} else {
assert(NULL);
}
return ret;
}
/* Return a struct with all information about an entry. */
//將 p 所指向的列表節點的資訊全部儲存到 zlentry 中，並返回該 zlentry 。
void zipEntry(unsigned char *p, zlentry *e) {
ZIP_DECODE_PREVLEN(p, e->prevrawlensize, e->prevrawlen);
ZIP_DECODE_LENGTH(p + e->prevrawlensize, e->encoding, e->lensize, e->len);
e->headersize = e->prevrawlensize + e->lensize;
e->p = p;
}
/* Create a new empty ziplist. */
//建立並返回一個新的 ziplist
unsigned char *ziplistNew(void) {
unsigned int bytes = ZIPLIST_HEADER_SIZE+1;
unsigned char *zl = zmalloc(bytes);
ZIPLIST_BYTES(zl) = intrev32ifbe(bytes);
ZIPLIST_TAIL_OFFSET(zl) = intrev32ifbe(ZIPLIST_HEADER_SIZE);
ZIPLIST_LENGTH(zl) = 0;
zl[bytes-1] = ZIP_END;
return zl;
}
/* Resize the ziplist.
*
* 調整 ziplist 的大小為 len 位元組。
*
* 當 ziplist 原有的大小小於 len 時，擴充套件 ziplist 不會改變 ziplist 原有的元素。
*
*/
unsigned char *ziplistResize(unsigned char *zl, unsigned int len) {
zl = zrealloc(zl,len);
ZIPLIST_BYTES(zl) = intrev32ifbe(len);
zl[len-1] = ZIP_END;
return zl;
}
/* When an entry is inserted, we need to set the prevlen field of the next
* entry to equal the length of the inserted entry. It can occur that this
* length cannot be encoded in 1 byte and the next entry needs to be grow
* a bit larger to hold the 5-byte encoded prevlen. This can be done for free,
* because this only happens when an entry is already being inserted (which
* 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_BIG_PREVLEN, so we need to check that the prevlen can be encoded in
* every consecutive entry.
*
* 當將一個新節點新增到某個節點之前的時候，
* 如果原節點的 header 空間不足以儲存新節點的長度，
* 那麼就需要對原節點的 header 空間進行擴充套件（從 1 位元組擴充套件到 5 位元組）。
*
* 但是，當對原節點進行擴充套件之後，原節點的下一個節點的 prevlen 可能出現空間不足，
* 這種情況在多個連續節點的長度都接近 ZIP_BIGLEN 時可能發生。
*
* 這個函式就用於檢查並修復後續節點的空間問題。
* 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,
* because it can cause a "flapping" effect where a chain prevlen fields is
* first grown and then shrunk again after consecutive inserts. Rather, the
* field is allowed to stay larger than necessary, because a large prevlen
* field implies the ziplist is holding large entries anyway.
*
* The pointer "p" points to the first entry that does NOT need to be
* updated, i.e. consecutive fields MAY need an update.
* 注意，程式的檢查是針對 p 的後續節點，而不是 p 所指向的節點。
* 因為節點 p 在傳入之前已經完成了所需的空間擴充套件工作
*/
unsigned char *__ziplistCascadeUpdate(unsigned char *zl, unsigned char *p) {
size_t curlen = intrev32ifbe(ZIPLIST_BYTES(zl)), rawlen, rawlensize;
size_t offset, noffset, extra;
unsigned char *np;
zlentry cur, next;
while (p[0] != ZIP_END) {
zipEntry(p, &cur);
rawlen = cur.headersize + cur.len;
rawlensize = zipStorePrevEntryLength(NULL,rawlen);
/* Abort if there is no next entry. */
if (p[rawlen] == ZIP_END) break;
zipEntry(p+rawlen, &next);
/* Abort when "prevlen" has not changed. */
if (next.prevrawlen == rawlen) break;
if (next.prevrawlensize < rawlensize) {
/* The "prevlen" field of "next" needs more bytes to hold
* the raw length of "cur". */
offset = p-zl;
extra = rawlensize-next.prevrawlensize;
zl = ziplistResize(zl,curlen+extra);
p = zl+offset;
/* Current pointer and offset for next element. */
np = p+rawlen;
noffset = np-zl;
/* Update tail offset when next element is not the tail element. */
if ((zl+intrev32ifbe(ZIPLIST_TAIL_OFFSET(zl))) != np) {
ZIPLIST_TAIL_OFFSET(zl) =
intrev32ifbe(intrev32ifbe(ZIPLIST_TAIL_OFFSET(zl))+extra);
}
/* Move the tail to the back. */
memmove(np+rawlensize,
np+next.prevrawlensize,
curlen-noffset-next.prevrawlensize-1);
zipStorePrevEntryLength(np,rawlen);
/* Advance the cursor */
p += rawlen;
curlen += extra;
} else {
if (next.prevrawlensize > rawlensize) {
/* This would result in shrinking, which we want to avoid.
* So, set "rawlen" in the available bytes. */
zipStorePrevEntryLengthLarge(p+rawlen,rawlen);
} else {
zipStorePrevEntryLength(p+rawlen,rawlen);
}
/* Stop here, as the raw length of "next" has not changed. */
break;
}
}
return zl;
}
/* Delete "num" entries, starting at "p". Returns pointer to the ziplist.
* 從位置 p 開始，連續刪除 num 個節點。
*
* 函式的返回值為處理刪除操作之後的 ziplist 。
*/
unsigned char *__ziplistDelete(unsigned char *zl, unsigned char *p, unsigned int num) {
unsigned int i, totlen, deleted = 0;
size_t offset;
int nextdiff = 0;
zlentry first, tail;
zipEntry(p, &first);
for (i = 0; p[0] != ZIP_END && i < num; i++) {
p += zipRawEntryLength(p);
deleted++;
}
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
* number of bytes required compare to the current `prevrawlen`.
* 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;
zipStorePrevEntryLength(p,first.prevrawlen);
/* Update offset for tail */
ZIPLIST_TAIL_OFFSET(zl) =
intrev32ifbe(intrev32ifbe(ZIPLIST_TAIL_OFFSET(zl))-totlen);
/* When the tail contains more than one entry, we need to take
* "nextdiff" in account as well. Otherwise, a change in the
* size of prevlen doesn't have an effect on the *tail* offset. */
zipEntry(p, &tail);
if (p[tail.headersize+tail.len] != ZIP_END) {
ZIPLIST_TAIL_OFFSET(zl) =
intrev32ifbe(intrev32ifbe(ZIPLIST_TAIL_OFFSET(zl))+nextdiff);
}
/* Move tail to the front of the ziplist */
memmove(first.p,p,
intrev32ifbe(ZIPLIST_BYTES(zl))-(p-zl)-1);
} else {
/* The entire tail was deleted. No need to move memory. */
ZIPLIST_TAIL_OFFSET(zl) =
intrev32ifbe((first.p-zl)-first.prevrawlen);
}
/* Resize and update length */
offset = first.p-zl;
zl = ziplistResize(zl, intrev32ifbe(ZIPLIST_BYTES(zl))-totlen+nextdiff);
ZIPLIST_INCR_LENGTH(zl,-deleted);
p = zl+offset;
/* When nextdiff != 0, the raw length of the next entry has changed, so
* we need to cascade the update throughout the ziplist */
if (nextdiff != 0)
zl = __ziplistCascadeUpdate(zl,p);
}
return zl;
}
/* Insert item at "p".
* 根據指標 p 所指定的位置，將長度為 slen 的字串 s 插入到 zl 中。
*
* 函式的返回值為完成插入操作之後的 ziplist
*/
unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, unsigned char *s, unsigned int slen) {
size_t curlen = intrev32ifbe(ZIPLIST_BYTES(zl)), reqlen;
unsigned int prevlensize, prevlen = 0;
size_t offset;
int nextdiff = 0;
unsigned char encoding = 0;
long long value = 123456789; /* initialized to avoid warning. Using a value
that is easy to see if for some reason
we use it uninitialized. */
zlentry tail;
/* Find out prevlen for the entry that is inserted. */
if (p[0] != ZIP_END) {
ZIP_DECODE_PREVLEN(p, prevlensize, prevlen);
} else {
unsigned char *ptail = ZIPLIST_ENTRY_TAIL(zl);
if (ptail[0] != ZIP_END) {
prevlen = zipRawEntryLength(ptail);
}
}
/* See if the entry can be encoded */
if (zipTryEncoding(s,slen,&value,&encoding)) {
/* 'encoding' is set to the appropriate integer encoding */
reqlen = zipIntSize(encoding);
} else {
/* '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 += 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
* its prevlen field. */
int forcelarge = 0;
nextdiff = (p[0] != ZIP_END) ? zipPrevLenByteDiff(p,reqlen) : 0;
if (nextdiff == -4 && reqlen < 4) {
nextdiff = 0;
forcelarge = 1;
}
/* Store offset because a realloc may change the address of zl. */
offset = p-zl;
zl = ziplistResize(zl,curlen+reqlen+nextdiff);
p = zl+offset;
/* Apply memory move when necessary and update tail offset. */
if (p[0] != ZIP_END) {
/* Subtract one because of the ZIP_END bytes */
memmove(p+reqlen,p-nextdiff,curlen-offset-1+nextdiff);
/* Encode this entry's raw length in the next entry. */
if (forcelarge)
zipStorePrevEntryLengthLarge(p+reqlen,reqlen);
else
zipStorePrevEntryLength(p+reqlen,reqlen);
/* Update offset for tail */
ZIPLIST_TAIL_OFFSET(zl) =
intrev32ifbe(intrev32ifbe(ZIPLIST_TAIL_OFFSET(zl))+reqlen);
/* When the tail contains more than one entry, we need to take
* "nextdiff" in account as well. Otherwise, a change in the
* size of prevlen doesn't have an effect on the *tail* offset. */
zipEntry(p+reqlen, &tail);
if (p[reqlen+tail.headersize+tail.len] != ZIP_END) {
ZIPLIST_TAIL_OFFSET(zl) =
intrev32ifbe(intrev32ifbe(ZIPLIST_TAIL_OFFSET(zl))+nextdiff);
}
} else {
/* This element will be the new tail. */
ZIPLIST_TAIL_OFFSET(zl) = intrev32ifbe(p-zl);
}
/* When nextdiff != 0, the raw length of the next entry has changed, so
* we need to cascade the update throughout the ziplist */
if (nextdiff != 0) {
offset = p-zl;
zl = __ziplistCascadeUpdate(zl,p+reqlen);
p = zl+offset;
}
/* Write the entry */
p += zipStorePrevEntryLength(p,prevlen);
p += zipStoreEntryEncoding(p,encoding,slen);
if (ZIP_IS_STR(encoding)) {
memcpy(p,s,slen);
} else {
zipSaveInteger(p,value,encoding);
}
ZIPLIST_INCR_LENGTH(zl,1);
return zl;
}
/* Merge ziplists 'first' and 'second' by appending 'second' to 'first'.
*
* NOTE: The larger ziplist is reallocated to contain the new merged ziplist.
* 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 ziplist is the contents of 'first' followed by 'second'.
*
* On failure: returns NULL if the merge is impossible.
* On success: returns the merged ziplist (which is expanded version of either
* 'first' or 'second', also frees the other unused input ziplist, and sets the
* input ziplist argument equal to newly reallocated ziplist return value. */
unsigned char *ziplistMerge(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 = intrev32ifbe(ZIPLIST_BYTES(*first));
size_t first_len = intrev16ifbe(ZIPLIST_LENGTH(*first));
size_t second_bytes = intrev32ifbe(ZIPLIST_BYTES(*second));
size_t second_len = intrev16ifbe(ZIPLIST_LENGTH(*second));
int append;
unsigned char *source, *target;
size_t target_bytes, source_bytes;
/* Pick the largest ziplist so we can resize easily in-place.
* We must also track if we are now appending or prepending to
* the target ziplist. */
if (first_len >= second_len) {
/* 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) */
size_t zlbytes = first_bytes + second_bytes -
ZIPLIST_HEADER_SIZE - ZIPLIST_END_SIZE;
size_t zllength = first_len + second_len;
/* Combined zl length should be limited within UINT16_MAX */
zllength = zllength < UINT16_MAX ? zllength : UINT16_MAX;
/* Save offset positions before we start ripping memory apart. */
size_t first_offset = intrev32ifbe(ZIPLIST_TAIL_OFFSET(*first));
size_t second_offset = intrev32ifbe(ZIPLIST_TAIL_OFFSET(*second));
/* Extend target to new zlbytes then append or prepend source. */
target = zrealloc(target, zlbytes);
if (append) {
/* append == appending to target */
/* Copy source after target (copying over original [END]):
* [TARGET - END, SOURCE - HEADER] */
memcpy(target + target_bytes - ZIPLIST_END_SIZE,
source + ZIPLIST_HEADER_SIZE,
source_bytes - ZIPLIST_HEADER_SIZE);
} else {
/* !append == prepending to target */
/* Move target *contents* exactly size of (source - [END]),
* then copy source into vacataed space (source - [END]):
* [SOURCE - END, TARGET - HEADER] */
memmove(target + source_bytes - ZIPLIST_END_SIZE,
target + ZIPLIST_HEADER_SIZE,
target_bytes - ZIPLIST_HEADER_SIZE);
memcpy(target, source, source_bytes - ZIPLIST_END_SIZE);
}
/* Update header metadata. */
ZIPLIST_BYTES(target) = intrev32ifbe(zlbytes);
ZIPLIST_LENGTH(target) = intrev16ifbe(zllength);
/* New tail offset is:
* + N bytes of first ziplist
* - 1 byte for [END] of first ziplist
* + M bytes for the offset of the original tail of the second ziplist
* - J bytes for HEADER because second_offset keeps no header. */
ZIPLIST_TAIL_OFFSET(target) = intrev32ifbe(
(first_bytes - ZIPLIST_END_SIZE) +
(second_offset - ZIPLIST_HEADER_SIZE));
/* __ziplistCascadeUpdate just fixes the prev length values until it finds a
* correct prev length value (then it assumes the rest of the list is okay).
* We tell CascadeUpdate to start at the first ziplist's tail element to fix
* the merge seam. */
target = __ziplistCascadeUpdate(target, target+first_offset);
/* Now free and NULL out what we didn't realloc */
if (append) {
zfree(*second);
*second = NULL;
*first = target;
} else {
zfree(*first);
*first = NULL;
*second = target;
}
return target;
}
unsigned char *ziplistPush(unsigned char *zl, unsigned char *s, unsigned int slen, int where) {
unsigned char *p;
p = (where == ZIPLIST_HEAD) ? ZIPLIST_ENTRY_HEAD(zl) : ZIPLIST_ENTRY_END(zl);
return __ziplistInsert(zl,p,s,slen);
}
/* Returns an offset to use for iterating with ziplistNext. When the given
* index is negative, the list is traversed back to front. When the list
* doesn't contain an element at the provided index, NULL is returned. */
unsigned char *ziplistIndex(unsigned char *zl, int index) {
unsigned char *p;
unsigned int prevlensize, prevlen = 0;
if (index < 0) {
index = (-index)-1;
p = ZIPLIST_ENTRY_TAIL(zl);
if (p[0] != ZIP_END) {
ZIP_DECODE_PREVLEN(p, prevlensize, prevlen);
while (prevlen > 0 && index--) {
p -= prevlen;
ZIP_DECODE_PREVLEN(p, prevlensize, prevlen);
}
}
} else {
p = ZIPLIST_ENTRY_HEAD(zl);
while (p[0] != ZIP_END && index--) {
p += zipRawEntryLength(p);
}
}
return (p[0] == ZIP_END || index > 0) ? NULL : p;
}
/* Return pointer to next entry in ziplist.
*
* zl is the pointer to the ziplist
* p is the pointer to the current element
*
* The element after 'p' is returned, otherwise NULL if we are at the end. */
unsigned char *ziplistNext(unsigned char *zl, unsigned char *p) {
((void) zl);
/* "p" could be equal to ZIP_END, caused by ziplistDelete,
* and we should return NULL. Otherwise, we should return NULL
* when the *next* element is ZIP_END (there is no next entry). */
if (p[0] == ZIP_END) {
return NULL;
}
p += zipRawEntryLength(p);
if (p[0] == ZIP_END) {
return NULL;
}
return p;
}
/* Return pointer to previous entry in ziplist. */
unsigned char *ziplistPrev(unsigned char *zl, unsigned char *p) {
unsigned int prevlensize, prevlen = 0;
/* Iterating backwards from ZIP_END should return the tail. When "p" is
* equal to the first element of the list, we're already at the head,
* and should return NULL. */
if (p[0] == ZIP_END) {
p = ZIPLIST_ENTRY_TAIL(zl);
return (p[0] == ZIP_END) ? NULL : p;
} else if (p == ZIPLIST_ENTRY_HEAD(zl)) {
return NULL;
} else {
ZIP_DECODE_PREVLEN(p, prevlensize, prevlen);
assert(prevlen > 0);
return p-prevlen;
}
}
/* Get entry pointed to by 'p' and store in either '*sstr' or 'sval' depending
* on the encoding of the entry. '*sstr' is always set to NULL to be able
* to find out whether the string pointer or the integer value was set.
* Return 0 if 'p' points to the end of the ziplist, 1 otherwise. */
unsigned int ziplistGet(unsigned char *p, unsigned char **sstr, unsigned int *slen, long long *sval) {
zlentry entry;
if (p == NULL || p[0] == ZIP_END) return 0;
if (sstr) *sstr = NULL;
zipEntry(p, &entry);
if (ZIP_IS_STR(entry.encoding)) {
if (sstr) {
*slen = entry.len;
*sstr = p+entry.headersize;
}
} else {
if (sval) {
*sval = zipLoadInteger(p+entry.headersize,entry.encoding);
}
}
return 1;
}
/* Insert an entry at "p". */
unsigned char *ziplistInsert(unsigned char *zl, unsigned char *p, unsigned char *s, unsigned int slen) {
return __ziplistInsert(zl,p,s,slen);
}
/* Delete a single entry from the ziplist, pointed to by *p.
* Also update *p in place, to be able to iterate over the
* ziplist, while deleting entries. */
unsigned char *ziplistDelete(unsigned char *zl, unsigned char **p) {
size_t offset = *p-zl;
zl = __ziplistDelete(zl,*p,1);
/* Store pointer to current element in p, because ziplistDelete will
* do a realloc which might result in a different "zl"-pointer.
* When the delete direction is back to front, we might delete the last
* entry and end up with "p" pointing to ZIP_END, so check this. */
*p = zl+offset;
return zl;
}
/* Delete a range of entries from the ziplist. */
unsigned char *ziplistDeleteRange(unsigned char *zl, int index, unsigned int num) {
unsigned char *p = ziplistIndex(zl,index);
return (p == NULL) ? zl : __ziplistDelete(zl,p,num);
}
/* Compare entry pointer to by 'p' with 'sstr' of length 'slen'. */
/* Return 1 if equal. */
unsigned int ziplistCompare(unsigned char *p, unsigned char *sstr, unsigned int slen) {
zlentry entry;
unsigned char sencoding;
long long zval, sval;
if (p[0] == ZIP_END) return 0;
zipEntry(p, &entry);
if (ZIP_IS_STR(entry.encoding)) {
/* Raw compare */
if (entry.len == slen) {
return memcmp(p+entry.headersize,sstr,slen) == 0;
} else {
return 0;
}
} else {
/* Try to compare encoded values. Don't compare encoding because
* different implementations may encoded integers differently. */
if (zipTryEncoding(sstr,slen,&sval,&sencoding)) {
zval = zipLoadInteger(p+entry.headersize,entry.encoding);
return zval == sval;
}
}
return 0;
}
/* 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 *ziplistFind(unsigned char *p, unsigned char *vstr, unsigned int vlen, unsigned int skip) {
int skipcnt = 0;
unsigned char vencoding = 0;
long long vll = 0;
while (p[0] != ZIP_END) {
unsigned int prevlensize, encoding, lensize, len;
unsigned char *q;
ZIP_DECODE_PREVLENSIZE(p, prevlensize);
ZIP_DECODE_LENGTH(p + prevlensize, encoding, lensize, len);
q = p + prevlensize + lensize;
if (skipcnt == 0) {
/* Compare current entry with specified entry */
if (ZIP_IS_STR(encoding)) {
if (len == vlen && memcmp(q, vstr, vlen) == 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 (!zipTryEncoding(vstr, vlen, &vll, &vencoding)) {
/* If the entry can't be encoded we set it to
* UCHAR_MAX so that we don't retry again the next
* time. */
vencoding = UCHAR_MAX;
}
/* Must be non-zero by now */
assert(vencoding);
}
/* 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) {
long long ll = zipLoadInteger(q, encoding);
if (ll == vll) {
return p;
}
}
}
/* Reset skip count */
skipcnt = skip;
} else {
/* Skip entry */
skipcnt--;
}
/* Move to next entry */
p = q + len;
}
return NULL;
}
/* Return length of ziplist. */
unsigned int ziplistLen(unsigned char *zl) {
unsigned int len = 0;
if (intrev16ifbe(ZIPLIST_LENGTH(zl)) < UINT16_MAX) {
len = intrev16ifbe(ZIPLIST_LENGTH(zl));
} else {
unsigned char *p = zl+ZIPLIST_HEADER_SIZE;
while (*p != ZIP_END) {
p += zipRawEntryLength(p);
len++;
}
/* Re-store length if small enough */
if (len < UINT16_MAX) ZIPLIST_LENGTH(zl) = intrev16ifbe(len);
}
return len;
}
/* Return ziplist blob size in bytes. */
size_t ziplistBlobLen(unsigned char *zl) {
return intrev32ifbe(ZIPLIST_BYTES(zl));
}
void ziplistRepr(unsigned char *zl) {
unsigned char *p;
int index = 0;
zlentry entry;
printf(
"{total bytes %d} "
"{num entries %u}\n"
"{tail offset %u}\n",
intrev32ifbe(ZIPLIST_BYTES(zl)),
intrev16ifbe(ZIPLIST_LENGTH(zl)),
intrev32ifbe(ZIPLIST_TAIL_OFFSET(zl)));
p = ZIPLIST_ENTRY_HEAD(zl);
while(*p != ZIP_END) {
zipEntry(p, &entry);
printf(
"{\n"
"\taddr 0x%08lx,\n"
"\tindex %2d,\n"
"\toffset %5ld,\n"
"\thdr+entry len: %5u,\n"
"\thdr len%2u,\n"
"\tprevrawlen: %5u,\n"
"\tprevrawlensize: %2u,\n"
"\tpayload %5u\n",
(long unsigned)p,
index,
(unsigned long) (p-zl),
entry.headersize+entry.len,
entry.headersize,
entry.prevrawlen,
entry.prevrawlensize,
entry.len);
printf("\tbytes: ");
for (unsigned int i = 0; i < entry.headersize+entry.len; i++) {
printf("%02x|",p[i]);
}
printf("\n");
p += entry.headersize;
if (ZIP_IS_STR(entry.encoding)) {
printf("\t[str]");
if (entry.len > 40) {
if (fwrite(p,40,1,stdout) == 0) perror("fwrite");
printf("...");
} else {
if (entry.len &&
fwrite(p,entry.len,1,stdout) == 0) perror("fwrite");
}
} else {
printf("\t[int]%lld", (long long) zipLoadInteger(p,entry.encoding));
}
printf("\n}\n");
p += entry.len;
index++;
}
printf("{end}\n\n");
}
#ifdef REDIS_TEST
#include <sys/time.h>
#include "adlist.h"
#include "sds.h"
#define debug(f, ...) { if (DEBUG) printf(f, __VA_ARGS__); }
static unsigned char *createList() {
unsigned char *zl = ziplistNew();
zl = ziplistPush(zl, (unsigned char*)"foo", 3, ZIPLIST_TAIL);
zl = ziplistPush(zl, (unsigned char*)"quux", 4, ZIPLIST_TAIL);
zl = ziplistPush(zl, (unsigned char*)"hello", 5, ZIPLIST_HEAD);
zl = ziplistPush(zl, (unsigned char*)"1024", 4, ZIPLIST_TAIL);
return zl;
}
static unsigned char *createIntList() {
unsigned char *zl = ziplistNew();
char buf[32];
sprintf(buf, "100");
zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_TAIL);
sprintf(buf, "128000");
zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_TAIL);
sprintf(buf, "-100");
zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_HEAD);
sprintf(buf, "4294967296");
zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_HEAD);
sprintf(buf, "non integer");
zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_TAIL);
sprintf(buf, "much much longer non integer");
zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_TAIL);
return zl;
}
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 *zl;
char posstr[2][5] = { "HEAD", "TAIL" };
long long start;
for (i = 0; i < maxsize; i+=dnum) {
zl = ziplistNew();
for (j = 0; j < i; j++) {
zl = ziplistPush(zl,(unsigned char*)"quux",4,ZIPLIST_TAIL);
}
/* Do num times a push+pop from pos */
start = usec();
for (k = 0; k < num; k++) {
zl = ziplistPush(zl,(unsigned char*)"quux",4,pos);
zl = ziplistDeleteRange(zl,0,1);
}
printf("List size: %8d, bytes: %8d, %dx push+pop (%s): %6lld usec\n",
i,intrev32ifbe(ZIPLIST_BYTES(zl)),num,posstr[pos],usec()-start);
zfree(zl);
}
}
static unsigned char *pop(unsigned char *zl, int where) {
unsigned char *p, *vstr;
unsigned int vlen;
long long vlong;
p = ziplistIndex(zl,where == ZIPLIST_HEAD ? 0 : -1);
if (ziplistGet(p,&vstr,&vlen,&vlong)) {
if (where == ZIPLIST_HEAD)
printf("Pop head: ");
else
printf("Pop tail: ");
if (vstr) {
if (vlen && fwrite(vstr,vlen,1,stdout) == 0) perror("fwrite");
}
else {
printf("%lld", vlong);
}
printf("\n");
return ziplistDelete(zl,&p);
} else {
printf("ERROR: Could not pop\n");
exit(1);
}
}
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 verify(unsigned char *zl, zlentry *e) {
int len = ziplistLen(zl);
zlentry _e;
ZIPLIST_ENTRY_ZERO(&_e);
for (int i = 0; i < len; i++) {
memset(&e[i], 0, sizeof(zlentry));
zipEntry(ziplistIndex(zl, i), &e[i]);
memset(&_e, 0, sizeof(zlentry));
zipEntry(ziplistIndex(zl, -len+i), &_e);
assert(memcmp(&e[i], &_e, sizeof(zlentry)) == 0);
}
}
int ziplistTest(int argc, char **argv) {
unsigned char *zl, *p;
unsigned char *entry;
unsigned int elen;
long long value;
/* If an argument is given, use it as the random seed. */
if (argc == 2)
srand(atoi(argv[1]));
zl = createIntList();
ziplistRepr(zl);
zfree(zl);
zl = createList();
ziplistRepr(zl);
zl = pop(zl,ZIPLIST_TAIL);
ziplistRepr(zl);
zl = pop(zl,ZIPLIST_HEAD);
ziplistRepr(zl);
zl = pop(zl,ZIPLIST_TAIL);
ziplistRepr(zl);
zl = pop(zl,ZIPLIST_TAIL);
ziplistRepr(zl);
zfree(zl);
printf("Get element at index 3:\n");
{
zl = createList();
p = ziplistIndex(zl, 3);
if (!ziplistGet(p, &entry, &elen, &value)) {
printf("ERROR: Could not access index 3\n");
return 1;
}
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0) perror("fwrite");
printf("\n");
} else {
printf("%lld\n", value);
}
printf("\n");
zfree(zl);
}
printf("Get element at index 4 (out of range):\n");
{
zl = createList();
p = ziplistIndex(zl, 4);
if (p == NULL) {
printf("No entry\n");
} else {
printf("ERROR: Out of range index should return NULL, returned offset: %ld\n", p-zl);
return 1;
}
printf("\n");
zfree(zl);
}
printf("Get element at index -1 (last element):\n");
{
zl = createList();
p = ziplistIndex(zl, -1);
if (!ziplistGet(p, &entry, &elen, &value)) {
printf("ERROR: Could not access index -1\n");
return 1;
}
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0) perror("fwrite");
printf("\n");
} else {
printf("%lld\n", value);
}
printf("\n");
zfree(zl);
}
printf("Get element at index -4 (first element):\n");
{
zl = createList();
p = ziplistIndex(zl, -4);
if (!ziplistGet(p, &entry, &elen, &value)) {
printf("ERROR: Could not access index -4\n");
return 1;
}
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0) perror("fwrite");
printf("\n");
} else {
printf("%lld\n", value);
}
printf("\n");
zfree(zl);
}
printf("Get element at index -5 (reverse out of range):\n");
{
zl = createList();
p = ziplistIndex(zl, -5);
if (p == NULL) {
printf("No entry\n");
} else {
printf("ERROR: Out of range index should return NULL, returned offset: %ld\n", p-zl);
return 1;
}
printf("\n");
zfree(zl);
}
printf("Iterate list from 0 to end:\n");
{
zl = createList();
p = ziplistIndex(zl, 0);
while (ziplistGet(p, &entry, &elen, &value)) {
printf("Entry: ");
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0) perror("fwrite");
} else {
printf("%lld", value);
}
p = ziplistNext(zl,p);
printf("\n");
}
printf("\n");
zfree(zl);
}
printf("Iterate list from 1 to end:\n");
{
zl = createList();
p = ziplistIndex(zl, 1);
while (ziplistGet(p, &entry, &elen, &value)) {
printf("Entry: ");
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0) perror("fwrite");
} else {
printf("%lld", value);
}
p = ziplistNext(zl,p);
printf("\n");
}
printf("\n");
zfree(zl);
}
printf("Iterate list from 2 to end:\n");
{
zl = createList();
p = ziplistIndex(zl, 2);
while (ziplistGet(p, &entry, &elen, &value)) {
printf("Entry: ");
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0) perror("fwrite");
} else {
printf("%lld", value);
}
p = ziplistNext(zl,p);
printf("\n");
}
printf("\n");
zfree(zl);
}
printf("Iterate starting out of range:\n");
{
zl = createList();
p = ziplistIndex(zl, 4);
if (!ziplistGet(p, &entry, &elen, &value)) {
printf("No entry\n");
} else {
printf("ERROR\n");
}
printf("\n");
zfree(zl);
}
printf("Iterate from back to front:\n");
{
zl = createList();
p = ziplistIndex(zl, -1);
while (ziplistGet(p, &entry, &elen, &value)) {
printf("Entry: ");
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0) perror("fwrite");
} else {
printf("%lld", value);
}
p = ziplistPrev(zl,p);
printf("\n");
}
printf("\n");
zfree(zl);
}
printf("Iterate from back to front, deleting all items:\n");
{
zl = createList();
p = ziplistIndex(zl, -1);
while (ziplistGet(p, &entry, &elen, &value)) {
printf("Entry: ");
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0) perror("fwrite");
} else {
printf("%lld", value);
}
zl = ziplistDelete(zl,&p);
p = ziplistPrev(zl,p);
printf("\n");
}
printf("\n");
zfree(zl);
}
printf("Delete inclusive range 0,0:\n");
{
zl = createList();
zl = ziplistDeleteRange(zl, 0, 1);
ziplistRepr(zl);
zfree(zl);
}
printf("Delete inclusive range 0,1:\n");
{
zl = createList();
zl = ziplistDeleteRange(zl, 0, 2);
ziplistRepr(zl);
zfree(zl);
}
printf("Delete inclusive range 1,2:\n");
{
zl = createList();
zl = ziplistDeleteRange(zl, 1, 2);
ziplistRepr(zl);
zfree(zl);
}
printf("Delete with start index out of range:\n");
{
zl = createList();
zl = ziplistDeleteRange(zl, 5, 1);
ziplistRepr(zl);
zfree(zl);
}
printf("Delete with num overflow:\n");
{
zl = createList();
zl = ziplistDeleteRange(zl, 1, 5);
ziplistRepr(zl);
zfree(zl);
}
printf("Delete foo while iterating:\n");
{
zl = createList();
p = ziplistIndex(zl,0);
while (ziplistGet(p,&entry,&elen,&value)) {
if (entry && strncmp("foo",(char*)entry,elen) == 0) {
printf("Delete foo\n");
zl = ziplistDelete(zl,&p);
} else {
printf("Entry: ");
if (entry) {
if (elen && fwrite(entry,elen,1,stdout) == 0)
perror("fwrite");
} else {
printf("%lld",value);
}
p = ziplistNext(zl,p);
printf("\n");
}
}
printf("\n");
ziplistRepr(zl);
zfree(zl);
}
printf("Regression test for >255 byte strings:\n");
{
char v1[257] = {0}, v2[257] = {0};
memset(v1,'x',256);
memset(v2,'y',256);
zl = ziplistNew();
zl = ziplistPush(zl,(unsigned char*)v1,strlen(v1),ZIPLIST_TAIL);
zl = ziplistPush(zl,(unsigned char*)v2,strlen(v2),ZIPLIST_TAIL);
/* Pop values again and compare their value. */
p = ziplistIndex(zl,0);
assert(ziplistGet(p,&entry,&elen,&value));
assert(strncmp(v1,(char*)entry,elen) == 0);
p = ziplistIndex(zl,1);
assert(ziplistGet(p,&entry,&elen,&value));
assert(strncmp(v2,(char*)entry,elen) == 0);
printf("SUCCESS\n\n");
zfree(zl);
}
printf("Regression test deleting next to last entries:\n");
{
char v[3][257] = {{0}};
zlentry e[3] = {{.prevrawlensize = 0, .prevrawlen = 0, .lensize = 0,
.len = 0, .headersize = 0, .encoding = 0, .p = NULL}};
size_t i;
for (i = 0; i < (sizeof(v)/sizeof(v[0])); i++) {
memset(v[i], 'a' + i, sizeof(v[0]));
}
v[0][256] = '\0';
v[1][ 1] = '\0';
v[2][256] = '\0';
zl = ziplistNew();
for (i = 0; i < (sizeof(v)/sizeof(v[0])); i++) {
zl = ziplistPush(zl, (unsigned char *) v[i], strlen(v[i]), ZIPLIST_TAIL);
}
verify(zl, e);
assert(e[0].prevrawlensize == 1);
assert(e[1].prevrawlensize == 5);
assert(e[2].prevrawlensize == 1);
/* Deleting entry 1 will increase `prevrawlensize` for entry 2 */
unsigned char *p = e[1].p;
zl = ziplistDelete(zl, &p);
verify(zl, e);
assert(e[0].prevrawlensize == 1);
assert(e[1].prevrawlensize == 5);
printf("SUCCESS\n\n");
zfree(zl);
}
printf("Create long list and check indices:\n");
{
zl = ziplistNew();
char buf[32];
int i,len;
for (i = 0; i < 1000; i++) {
len = sprintf(buf,"%d",i);
zl = ziplistPush(zl,(unsigned char*)buf,len,ZIPLIST_TAIL);
}
for (i = 0; i < 1000; i++) {
p = ziplistIndex(zl,i);
assert(ziplistGet(p,NULL,NULL,&value));
assert(i == value);
p = ziplistIndex(zl,-i-1);
assert(ziplistGet(p,NULL,NULL,&value));
assert(999-i == value);
}
printf("SUCCESS\n\n");
zfree(zl);
}
printf("Compare strings with ziplist entries:\n");
{
zl = createList();
p = ziplistIndex(zl,0);
if (!ziplistCompare(p,(unsigned char*)"hello",5)) {
printf("ERROR: not \"hello\"\n");
return 1;
}
if (ziplistCompare(p,(unsigned char*)"hella",5)) {
printf("ERROR: \"hella\"\n");
return 1;
}
p = ziplistIndex(zl,3);
if (!ziplistCompare(p,(unsigned char*)"1024",4)) {
printf("ERROR: not \"1024\"\n");
return 1;
}
if (ziplistCompare(p,(unsigned char*)"1025",4)) {
printf("ERROR: \"1025\"\n");
return 1;
}
printf("SUCCESS\n\n");
zfree(zl);
}
printf("Merge test:\n");
{
/* create list gives us: [hello, foo, quux, 1024] */
zl = createList();
unsigned char *zl2 = createList();
unsigned char *zl3 = ziplistNew();
unsigned char *zl4 = ziplistNew();
if (ziplistMerge(&zl4, &zl4)) {
printf("ERROR: Allowed merging of one ziplist into itself.\n");
return 1;
}
/* Merge two empty ziplists, get empty result back. */
zl4 = ziplistMerge(&zl3, &zl4);
ziplistRepr(zl4);
if (ziplistLen(zl4)) {
printf("ERROR: Merging two empty ziplists created entries.\n");
return 1;
}
zfree(zl4);
zl2 = ziplistMerge(&zl, &zl2);
/* merge gives us: [hello, foo, quux, 1024, hello, foo, quux, 1024] */
ziplistRepr(zl2);
if (ziplistLen(zl2) != 8) {
printf("ERROR: Merged length not 8, but: %u\n", ziplistLen(zl2));
return 1;
}
p = ziplistIndex(zl2,0);
if (!ziplistCompare(p,(unsigned char*)"hello",5)) {
printf("ERROR: not \"hello\"\n");
return 1;
}
if (ziplistCompare(p,(unsigned char*)"hella",5)) {
printf("ERROR: \"hella\"\n");
return 1;
}
p = ziplistIndex(zl2,3);
if (!ziplistCompare(p,(unsigned char*)"1024",4)) {
printf("ERROR: not \"1024\"\n");
return 1;
}
if (ziplistCompare(p,(unsigned char*)"1025",4)) {
printf("ERROR: \"1025\"\n");
return 1;
}
p = ziplistIndex(zl2,4);
if (!ziplistCompare(p,(unsigned char*)"hello",5)) {
printf("ERROR: not \"hello\"\n");
return 1;
}
if (ziplistCompare(p,(unsigned char*)"hella",5)) {
printf("ERROR: \"hella\"\n");
return 1;
}
p = ziplistIndex(zl2,7);
if (!ziplistCompare(p,(unsigned char*)"1024",4)) {
printf("ERROR: not \"1024\"\n");
return 1;
}
if (ziplistCompare(p,(unsigned char*)"1025",4)) {
printf("ERROR: \"1025\"\n");
return 1;
}
printf("SUCCESS\n\n");
zfree(zl);
}
printf("Stress with random payloads of different encoding:\n");
{
int i,j,len,where;
unsigned char *p;
char buf[1024];
int buflen;
list *ref;
listNode *refnode;
/* Hold temp vars from ziplist */
unsigned char *sstr;
unsigned int slen;
long long sval;
for (i = 0; i < 20000; i++) {
zl = ziplistNew();
ref = listCreate();
listSetFreeMethod(ref,(void (*)(void*))sdsfree);
len = rand() % 256;
/* Create lists */
for (j = 0; j < len; j++) {
where = (rand() & 1) ? ZIPLIST_HEAD : ZIPLIST_TAIL;
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 ziplist */
zl = ziplistPush(zl, (unsigned char*)buf, buflen, where);
/* Add to reference list */
if (where == ZIPLIST_HEAD) {
listAddNodeHead(ref,sdsnewlen(buf, buflen));
} else if (where == ZIPLIST_TAIL) {
listAddNodeTail(ref,sdsnewlen(buf, buflen));
} else {
assert(NULL);
}
}
assert(listLength(ref) == ziplistLen(zl));
for (j = 0; j < len; j++) {
/* Naive way to get elements, but similar to the stresser
* executed from the Tcl test suite. */
p = ziplistIndex(zl,j);
refnode = listIndex(ref,j);
assert(ziplistGet(p,&sstr,&slen,&sval));
if (sstr == NULL) {
buflen = sprintf(buf,"%lld",sval);
} else {
buflen = slen;
memcpy(buf,sstr,buflen);
buf[buflen] = '\0';
}
assert(memcmp(buf,listNodeValue(refnode),buflen) == 0);
}
zfree(zl);
listRelease(ref);
}
printf("SUCCESS\n\n");
}
printf("Stress with variable ziplist size:\n");
{
stress(ZIPLIST_HEAD,100000,16384,256);
stress(ZIPLIST_TAIL,100000,16384,256);
}
return 0;
}
#endif相關文章
- Redis資料結構三之壓縮列表Redis資料結構
- Redis學習筆記（二）redis 底層資料結構Redis筆記資料結構
- Redis原始碼學習——基礎資料結構之SDSRedis原始碼資料結構
- 圖解Redis之資料結構篇——壓縮列表圖解Redis資料結構
- Redis底層資料結構——壓縮列表Redis資料結構
- Redis資料結構概覽（原始碼分析）Redis資料結構原始碼
- 深入剖析Redis系列(八) - Redis資料結構之集合Redis資料結構
- redis原始碼分析（六）、redis命令學習總結—Redis 集合(Set)Redis原始碼
- 【筆記】-《Redis實戰》- 01 Redis資料結構筆記Redis資料結構
- Redis資料結構—整數集合與壓縮列表Redis資料結構
- Redis學習筆記（二）——Redis資料型別Redis筆記資料型別
- Redis原始碼分析-底層資料結構盤點Redis原始碼資料結構
- redis原始碼分析（四）、redis命令學習總結—連結串列ListRedis原始碼
- Redis學習筆記八：叢集模式Redis筆記模式
- redis原始碼分析（七）、redis命令學習總結—Redis 有序集合(sorted set)Redis原始碼
- redis原始碼分析（三）redis命令學習總結—string字串Redis原始碼字串
- redis原始碼分析（五）、redis命令學習總結—雜湊HashRedis原始碼
- Redis學習筆記（七） 資料庫Redis筆記資料庫
- redis個人原始碼分析筆記3---redis的事件驅動原始碼分析Redis原始碼筆記事件
- redis原始碼分析（二）、redis原始碼分析之sds字串Redis原始碼字串
- [Redis 系列]redis 學習三，redis 資料結構之 string 和 list 基本使用及熟悉Redis資料結構
- 【Redis 系列】redis 學習三，redis 資料結構之 string 和 list 基本使用及熟悉Redis資料結構
- redis----第二天學習筆記（資料結構：快速的redis有哪些慢操作？）Redis筆記資料結構
- redis原始碼學習之slowlogRedis原始碼
- Redis學習筆記--Redis持久化Redis筆記持久化
- Redis 學習-資料結構基本簡介Redis資料結構
- redis學習筆記Redis筆記
- Redis 學習筆記Redis筆記
- Redis 資料結構 之 SDSRedis資料結構
- Redis深入之資料結構Redis資料結構
- redis原始碼學習Redis原始碼
- redis原始碼分析（9）redis原始碼連結串列學習總結 adlist.h adlist.cRedis原始碼
- redis redis中的hash結構【八】Redis
- 【Redis 系列】redis 學習十六，redis 字典(map) 及其核心編碼結構Redis
- Redis學習筆記【01】 - 安裝RedisRedis筆記
- Redis學習筆記（一）——初識RedisRedis筆記
- redis學習筆記(三)–Redis的功能Redis筆記
- （Redis學習筆記）：Redis解決方案Redis筆記