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rdb.h
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/*
* Copyright (c) 2009-2012, 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.
*/
#ifndef __REDIS_RDB_H
#define __REDIS_RDB_H
#include <stdio.h>
#include "rio.h"
/* TBD: include only necessary headers. */
#include "redis.h"
/* The current RDB version. When the format changes in a way that is no longer
* backward compatible this number gets incremented. */
/* 当前的RDB版本，如果rdb的格式改变而不兼容前面的版本时，该数字加1。*/
#define REDIS_RDB_VERSION 6
/* Defines related to the dump file format. To store 32 bits lengths for short
* keys requires a lot of space, so we check the most significant 2 bits of
* the first byte to interpreter the length:
* 对于一些较短的key，如果使用32bit的整数来存储长度信息会造成较大的空间浪费，
* 所以我们通过检查第一个字节的前两个bit来判断长度
*
* 00|000000 => if the two MSB are 00 the len is the 6 bits of this byte
* 如果前两个bit是00，则长度信息在该字节的其余6个bit上
* 01|000000 00000000 => 01, the len is 14 byes, 6 bits + 8 bits of next byte
* 如果前两个bit是01，则长度信息为当前字节的6个bit加上下一个字节的8个bit
* 10|000000 [32 bit integer] => if it's 01, a full 32 bit len will follow
* 如果前两个bit是10，则长度信息为随后的四个字节（32bit）
* 11|000000 this means: specially encoded object will follow. The six bits
* number specify the kind of object that follows.
* 如果前两个bit是11，则后边跟一个特殊编码的对象，当前字节的后6bit指定了对象的类型。
* See the REDIS_RDB_ENC_* defines.
*
* Lengths up to 63 are stored using a single byte, most DB keys, and may
* values, will fit inside.
* 一个字节的后6bit可以保存的最大长度为63，对于大多数key和value来说已经足够了。
*/
#define REDIS_RDB_6BITLEN 0
#define REDIS_RDB_14BITLEN 1
#define REDIS_RDB_32BITLEN 2
#define REDIS_RDB_ENCVAL 3
#define REDIS_RDB_LENERR UINT_MAX
/* When a length of a string object stored on disk has the first two bits
* set, the remaining two bits specify a special encoding for the object
* accordingly to the following defines: */
/* 当一个字符串对象的长度信息保存在磁盘中时，最高两个bit（这两个bit为11）之后的两个bit（即第3个bit和第4个bit）指明了
其编码方式，规则如下： */
#define REDIS_RDB_ENC_INT8 0 /* 8 bit signed integer */
#define REDIS_RDB_ENC_INT16 1 /* 16 bit signed integer */
#define REDIS_RDB_ENC_INT32 2 /* 32 bit signed integer */
#define REDIS_RDB_ENC_LZF 3 /* string compressed with FASTLZ */
/* Dup object types to RDB object types. Only reason is readability (are we
* dealing with RDB types or with in-memory object types?). */
/* Redis五种数据类型所对应的RDB对象类型 */
#define REDIS_RDB_TYPE_STRING 0
#define REDIS_RDB_TYPE_LIST 1
#define REDIS_RDB_TYPE_SET 2
#define REDIS_RDB_TYPE_ZSET 3
#define REDIS_RDB_TYPE_HASH 4
/* Object types for encoded objects. */
/* 编码对象的类型 */
#define REDIS_RDB_TYPE_HASH_ZIPMAP 9
#define REDIS_RDB_TYPE_LIST_ZIPLIST 10
#define REDIS_RDB_TYPE_SET_INTSET 11
#define REDIS_RDB_TYPE_ZSET_ZIPLIST 12
#define REDIS_RDB_TYPE_HASH_ZIPLIST 13
/* Test if a type is an object type. */
/* 检查给定的类型是否为Redis的对象类型。*/
#define rdbIsObjectType(t) ((t >= 0 && t <= 4) || (t >= 9 && t <= 13))
/* Special RDB opcodes (saved/loaded with rdbSaveType/rdbLoadType). */
/* 特殊的RDB操作吗 */
// 以毫秒为单位的过期时间
#define REDIS_RDB_OPCODE_EXPIRETIME_MS 252
// 以秒为单位的过期时间
#define REDIS_RDB_OPCODE_EXPIRETIME 253
// 选择数据库，对应的值是Redis db的编号
#define REDIS_RDB_OPCODE_SELECTDB 254
// 结尾符
#define REDIS_RDB_OPCODE_EOF 255
int rdbSaveType(rio *rdb, unsigned char type);
int rdbLoadType(rio *rdb);
int rdbSaveTime(rio *rdb, time_t t);
time_t rdbLoadTime(rio *rdb);
int rdbSaveLen(rio *rdb, uint32_t len);
uint32_t rdbLoadLen(rio *rdb, int *isencoded);
int rdbSaveObjectType(rio *rdb, robj *o);
int rdbLoadObjectType(rio *rdb);
int rdbLoad(char *filename);
int rdbSaveBackground(char *filename);
int rdbSaveToSlavesSockets(void);
void rdbRemoveTempFile(pid_t childpid);
int rdbSave(char *filename);
int rdbSaveObject(rio *rdb, robj *o);
off_t rdbSavedObjectLen(robj *o);
off_t rdbSavedObjectPages(robj *o);
robj *rdbLoadObject(int type, rio *rdb);
void backgroundSaveDoneHandler(int exitcode, int bysignal);
int rdbSaveKeyValuePair(rio *rdb, robj *key, robj *val, long long expiretime, long long now);
robj *rdbLoadStringObject(rio *rdb);
#endif