rdb.h

/*
 * 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. */
/*
 * RDB 的版本，当新版本不向就版本兼容时，增一
 */
#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:
 *
 * 通过读取第一字节的最高 2 位来判断长度
 *
 * 00|000000 => if the two MSB are 00 the len is the 6 bits of this byte
 *              长度编码在这一字节的其余 6 位中
 * 01|000000 00000000 =>  01, the len is 14 byes, 6 bits + 8 bits of next byte
 *                        长度为 14 位，当前字节 6 位，加上下个字节 8 位
 * 10|000000 [32 bit integer] => if it's 01, a full 32 bit len will follow
 *                               长度由后跟的 32 位保存
 * 11|000000 this means: specially encoded object will follow. The six bits
 *           number specify the kind of object that follows.
 *           See the REDIS_RDB_ENC_* defines.
 *           后跟一个特殊编码的对象。字节中的 6 位指定对象的类型。
 *           查看 REDIS_RDB_ENC_* 定义获得更多消息
 *
 * Lenghts up to 63 are stored using a single byte, most DB keys, and may
 * values, will fit inside. */
#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:
 *
 * 最高位 2 位之后的 2 位指定了对象的特殊编码
 */
#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?).
 *
 * 对象类型在 RDB 文件中的类型
 */
#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. */
/*
 * 编码对象的方式
 */
#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. */
/*
 * 检查给定类型是否对象
 */
#define rdbIsObjectType(t) ((t >= 0 && t <= 4) || (t >= 9 && t <= 13))

/* Special RDB opcodes (saved/loaded with rdbSaveType/rdbLoadType). */
/*
 * 特殊标识符
 */
#define REDIS_RDB_OPCODE_EXPIRETIME_MS 252  // 以 MS 计算的过期时间
#define REDIS_RDB_OPCODE_EXPIRETIME 253     // 以秒计算的过期时间
#define REDIS_RDB_OPCODE_SELECTDB   254     // 选择数据库
#define REDIS_RDB_OPCODE_EOF        255     // 结尾

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);
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