redis.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_H
#define __REDIS_H

#include "fmacros.h"
#include "config.h"

#if defined(__sun)
#include "solarisfixes.h"
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <limits.h>
#include <unistd.h>
#include <errno.h>
#include <inttypes.h>
#include <pthread.h>
#include <syslog.h>
#include <netinet/in.h>
#include <lua.h>
#include <signal.h>

#include "ae.h"      /* Event driven programming library */
#include "sds.h"     /* Dynamic safe strings */
#include "dict.h"    /* Hash tables */
#include "adlist.h"  /* Linked lists */
#include "zmalloc.h" /* total memory usage aware version of malloc/free */
#include "anet.h"    /* Networking the easy way */
#include "ziplist.h" /* Compact list data structure */
#include "intset.h"  /* Compact integer set structure */
#include "version.h" /* Version macro */
#include "util.h"    /* Misc functions useful in many places */

/* Error codes */
// 执行状态代码
#define REDIS_OK                0
#define REDIS_ERR               -1

/* Static server configuration */
/* 服务器默认静态配置 */
// 每秒钟调用时间中断器的次数
#define REDIS_HZ                100     /* Time interrupt calls/sec. */
// 服务器端口
#define REDIS_SERVERPORT        6379    /* TCP port */
// 最大客户端超时时间
#define REDIS_MAXIDLETIME       0       /* default client timeout: infinite */
// 数据库数量
#define REDIS_DEFAULT_DBNUM     16
#define REDIS_CONFIGLINE_MAX    1024
#define REDIS_EXPIRELOOKUPS_PER_CRON    10 /* lookup 10 expires per loop */
#define REDIS_EXPIRELOOKUPS_TIME_PERC   25 /* CPU max % for keys collection */
// 每次事件执行时最大的可写入字节数
// 写入超过这个值的写时间会被中断，等待下次继续写
// 从而避免大回复独占服务器时间
#define REDIS_MAX_WRITE_PER_EVENT (1024*64)
#define REDIS_SHARED_SELECT_CMDS 10
// 最大共享整数数值
#define REDIS_SHARED_INTEGERS 10000
#define REDIS_SHARED_BULKHDR_LEN 32
#define REDIS_MAX_LOGMSG_LEN    1024 /* Default maximum length of syslog messages */
#define REDIS_AOF_REWRITE_PERC  100
#define REDIS_AOF_REWRITE_MIN_SIZE (1024*1024)
#define REDIS_AOF_REWRITE_ITEMS_PER_CMD 64
#define REDIS_SLOWLOG_LOG_SLOWER_THAN 10000
#define REDIS_SLOWLOG_MAX_LEN 128
#define REDIS_MAX_CLIENTS 10000
#define REDIS_AUTHPASS_MAX_LEN 512
#define REDIS_DEFAULT_SLAVE_PRIORITY 100
#define REDIS_REPL_TIMEOUT 60
#define REDIS_REPL_PING_SLAVE_PERIOD 10
#define REDIS_RUN_ID_SIZE 40
#define REDIS_OPS_SEC_SAMPLES 16

/* Protocol and I/O related defines */
#define REDIS_MAX_QUERYBUF_LEN  (1024*1024*1024) /* 1GB max query buffer. */
#define REDIS_IOBUF_LEN         (1024*16)  /* Generic I/O buffer size */
#define REDIS_REPLY_CHUNK_BYTES (16*1024) /* 16k output buffer */
#define REDIS_INLINE_MAX_SIZE   (1024*64) /* Max size of inline reads */
#define REDIS_MBULK_BIG_ARG     (1024*32)

/* Hash table parameters */
#define REDIS_HT_MINFILL        10      /* Minimal hash table fill 10% */

/* Command flags. Please check the command table defined in the redis.c file
 * for more information about the meaning of every flag. */
#define REDIS_CMD_WRITE 1                   /* "w" flag */
#define REDIS_CMD_READONLY 2                /* "r" flag */
#define REDIS_CMD_DENYOOM 4                 /* "m" flag */
#define REDIS_CMD_FORCE_REPLICATION 8       /* "f" flag */
#define REDIS_CMD_ADMIN 16                  /* "a" flag */
#define REDIS_CMD_PUBSUB 32                 /* "p" flag */
#define REDIS_CMD_NOSCRIPT  64              /* "s" flag */
#define REDIS_CMD_RANDOM 128                /* "R" flag */
#define REDIS_CMD_SORT_FOR_SCRIPT 256       /* "S" flag */
#define REDIS_CMD_LOADING 512               /* "l" flag */
#define REDIS_CMD_STALE 1024                /* "t" flag */
#define REDIS_CMD_SKIP_MONITOR 2048         /* "M" flag */

/*
 * 对象类型
 */
#define REDIS_STRING 0
#define REDIS_LIST 1
#define REDIS_SET 2
#define REDIS_ZSET 3
#define REDIS_HASH 4

/*
 * 对象编码
 *
 * 像 String 和 Hash 这样的对象，可以有多种内部表示。
 * 对象的 encoding 属性可以设置为以下域的任意一种。
 */
#define REDIS_ENCODING_RAW 0     /* Raw representation */
#define REDIS_ENCODING_INT 1     /* Encoded as integer */
#define REDIS_ENCODING_HT 2      /* Encoded as hash table */
#define REDIS_ENCODING_ZIPMAP 3  /* Encoded as zipmap */
#define REDIS_ENCODING_LINKEDLIST 4 /* Encoded as regular linked list */
#define REDIS_ENCODING_ZIPLIST 5 /* Encoded as ziplist */
#define REDIS_ENCODING_INTSET 6  /* Encoded as intset */
#define REDIS_ENCODING_SKIPLIST 7  /* Encoded as skiplist */

/* 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:
 *
 * 00|000000 => if the two MSB are 00 the len is the 6 bits of this byte
 * 01|000000 00000000 =>  01, the len is 14 byes, 6 bits + 8 bits of next byte
 * 10|000000 [32 bit integer] => if it's 01, a full 32 bit len will follow
 * 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.
 *
 * 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: */
#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 */

/* AOF states */
#define REDIS_AOF_OFF 0             /* AOF is off */
#define REDIS_AOF_ON 1              /* AOF is on */
#define REDIS_AOF_WAIT_REWRITE 2    /* AOF waits rewrite to start appending */

/* Client flags */
#define REDIS_SLAVE (1<<0)   /* This client is a slave server */
#define REDIS_MASTER (1<<1)  /* This client is a master server */
#define REDIS_MONITOR (1<<2) /* This client is a slave monitor, see MONITOR */
#define REDIS_MULTI (1<<3)   /* This client is in a MULTI context */
#define REDIS_BLOCKED (1<<4) /* The client is waiting in a blocking operation */
#define REDIS_DIRTY_CAS (1<<5) /* Watched keys modified. EXEC will fail. */
#define REDIS_CLOSE_AFTER_REPLY (1<<6) /* Close after writing entire reply. */
#define REDIS_UNBLOCKED (1<<7) /* This client was unblocked and is stored in
                                  server.unblocked_clients */
#define REDIS_LUA_CLIENT (1<<8) /* This is a non connected client used by Lua */
#define REDIS_ASKING (1<<9)     /* Client issued the ASKING command */
#define REDIS_CLOSE_ASAP (1<<10)/* Close this client ASAP */
#define REDIS_UNIX_SOCKET (1<<11) /* Client connected via Unix domain socket */
#define REDIS_DIRTY_EXEC (1<<12)  /* EXEC will fail for errors while queueing */

/* Client request types */
#define REDIS_REQ_INLINE 1
#define REDIS_REQ_MULTIBULK 2

/* Client classes for client limits, currently used only for
 * the max-client-output-buffer limit implementation. */
#define REDIS_CLIENT_LIMIT_CLASS_NORMAL 0
#define REDIS_CLIENT_LIMIT_CLASS_SLAVE 1
#define REDIS_CLIENT_LIMIT_CLASS_PUBSUB 2
#define REDIS_CLIENT_LIMIT_NUM_CLASSES 3

/* Slave replication state - slave side 
 *
 * 附属节点角度的同步状态
 */
#define REDIS_REPL_NONE 0 /* No active replication */
#define REDIS_REPL_CONNECT 1 /* Must connect to master */
#define REDIS_REPL_CONNECTING 2 /* Connecting to master */
#define REDIS_REPL_RECEIVE_PONG 3 /* Wait for PING reply */
#define REDIS_REPL_TRANSFER 4 /* Receiving .rdb from master */
#define REDIS_REPL_CONNECTED 5 /* Connected to master */

/* Synchronous read timeout - slave side */
#define REDIS_REPL_SYNCIO_TIMEOUT 5

/* Slave replication state - from the point of view of master
 *
 * 主节点角度的同步状态
 *
 * Note that in SEND_BULK and ONLINE state the slave receives new updates
 * in its output queue. In the WAIT_BGSAVE state instead the server is waiting
 * to start the next background saving in order to send updates to it. */
#define REDIS_REPL_WAIT_BGSAVE_START 3 /* master waits bgsave to start feeding it */
#define REDIS_REPL_WAIT_BGSAVE_END 4 /* master waits bgsave to start bulk DB transmission */
#define REDIS_REPL_SEND_BULK 5 /* master is sending the bulk DB */
#define REDIS_REPL_ONLINE 6 /* bulk DB already transmitted, receive updates */

/* List related stuff 
 *
 * 列表头/尾
 */
#define REDIS_HEAD 0
#define REDIS_TAIL 1

/* Sort operations 
 *
 * 排序操作
 */
#define REDIS_SORT_GET 0
#define REDIS_SORT_ASC 1
#define REDIS_SORT_DESC 2
#define REDIS_SORTKEY_MAX 1024

/* Log levels 
 *
 * 日志 level
 */
#define REDIS_DEBUG 0
#define REDIS_VERBOSE 1
#define REDIS_NOTICE 2
#define REDIS_WARNING 3
#define REDIS_LOG_RAW (1<<10) /* Modifier to log without timestamp */

/* Anti-warning macro... */
#define REDIS_NOTUSED(V) ((void) V)

#define ZSKIPLIST_MAXLEVEL 32 /* Should be enough for 2^32 elements */
#define ZSKIPLIST_P 0.25      /* Skiplist P = 1/4 */

/* Append only defines 
 *
 * AOF 的保存频率
 */
#define AOF_FSYNC_NO 0
#define AOF_FSYNC_ALWAYS 1
#define AOF_FSYNC_EVERYSEC 2

/* Zip structure related defaults 
 *
 * 压缩结构的相关默认值
 */
#define REDIS_HASH_MAX_ZIPLIST_ENTRIES 512
#define REDIS_HASH_MAX_ZIPLIST_VALUE 64
#define REDIS_LIST_MAX_ZIPLIST_ENTRIES 512
#define REDIS_LIST_MAX_ZIPLIST_VALUE 64
#define REDIS_SET_MAX_INTSET_ENTRIES 512
#define REDIS_ZSET_MAX_ZIPLIST_ENTRIES 128
#define REDIS_ZSET_MAX_ZIPLIST_VALUE 64

/* Sets operations codes 
 *
 * 集合操作代号
 */
#define REDIS_OP_UNION 0
#define REDIS_OP_DIFF 1
#define REDIS_OP_INTER 2

/* Redis maxmemory strategies */
#define REDIS_MAXMEMORY_VOLATILE_LRU 0
#define REDIS_MAXMEMORY_VOLATILE_TTL 1
#define REDIS_MAXMEMORY_VOLATILE_RANDOM 2
#define REDIS_MAXMEMORY_ALLKEYS_LRU 3
#define REDIS_MAXMEMORY_ALLKEYS_RANDOM 4
#define REDIS_MAXMEMORY_NO_EVICTION 5

/* Scripting */
#define REDIS_LUA_TIME_LIMIT 5000 /* milliseconds */

/* Units */
// 过期时间的单位
#define UNIT_SECONDS 0          // 秒
#define UNIT_MILLISECONDS 1     // 毫秒

/* SHUTDOWN flags */
#define REDIS_SHUTDOWN_SAVE 1       /* Force SAVE on SHUTDOWN even if no save
                                       points are configured. */
#define REDIS_SHUTDOWN_NOSAVE 2     /* Don't SAVE on SHUTDOWN. */

/* Command call flags, see call() function */
#define REDIS_CALL_NONE 0
#define REDIS_CALL_SLOWLOG 1
#define REDIS_CALL_STATS 2
#define REDIS_CALL_PROPAGATE 4
#define REDIS_CALL_FULL (REDIS_CALL_SLOWLOG | REDIS_CALL_STATS | REDIS_CALL_PROPAGATE)

/* Command propagation flags, see propagate() function */
#define REDIS_PROPAGATE_NONE 0
#define REDIS_PROPAGATE_AOF 1
#define REDIS_PROPAGATE_REPL 2

/* Using the following macro you can run code inside serverCron() with the
 * specified period, specified in milliseconds.
 * The actual resolution depends on REDIS_HZ. */
// 在 serverCron() 中，按指定的毫秒周期执行代码
#define run_with_period(_ms_) if (!(server.cronloops%((_ms_)/(1000/REDIS_HZ))))

/* We can print the stacktrace, so our assert is defined this way: */
#define redisAssertWithInfo(_c,_o,_e) ((_e)?(void)0 : (_redisAssertWithInfo(_c,_o,#_e,__FILE__,__LINE__),_exit(1)))
#define redisAssert(_e) ((_e)?(void)0 : (_redisAssert(#_e,__FILE__,__LINE__),_exit(1)))
#define redisPanic(_e) _redisPanic(#_e,__FILE__,__LINE__),_exit(1)

/*-----------------------------------------------------------------------------
 * Data types
 *----------------------------------------------------------------------------*/

/* A redis object, that is a type able to hold a string / list / set */

/* The actual Redis Object */
#define REDIS_LRU_CLOCK_MAX ((1<<21)-1) /* Max value of obj->lru */
#define REDIS_LRU_CLOCK_RESOLUTION 10 /* LRU clock resolution in seconds */
/*
 * Redis 对象
 */
typedef struct redisObject {

    // 类型
    unsigned type:4;        

    // 不使用(对齐位)
    unsigned notused:2;

    // 编码方式
    unsigned encoding:4;

    // LRU 时间（相对于 server.lruclock）
    unsigned lru:22;

    // 引用计数
    int refcount;

    // 指向对象的值
    void *ptr;

} robj;

/* Macro used to initalize a Redis object allocated on the stack.
 * Note that this macro is taken near the structure definition to make sure
 * we'll update it when the structure is changed, to avoid bugs like
 * bug #85 introduced exactly in this way. */
/*
 * 初始化一个从栈上分配的 Redis Object
 */
#define initStaticStringObject(_var,_ptr) do { \
    _var.refcount = 1; \
    _var.type = REDIS_STRING; \
    _var.encoding = REDIS_ENCODING_RAW; \
    _var.ptr = _ptr; \
} while(0);

/*
 * 数据库结构
 */
typedef struct redisDb {
    // key space，包括键值对象
    dict *dict;                 /* The keyspace for this DB */
    // 保存 key 的过期时间
    dict *expires;              /* Timeout of keys with a timeout set */
    // 正因为某个/某些 key 而被阻塞的客户端
    dict *blocking_keys;        /* Keys with clients waiting for data (BLPOP) */
    // 某个/某些接收到 PUSH 命令的阻塞 key
    dict *ready_keys;           /* Blocked keys that received a PUSH */
    // 正在监视某个/某些 key 的所有客户端
    dict *watched_keys;         /* WATCHED keys for MULTI/EXEC CAS */
    // 数据库的号码
    int id;
} redisDb;

/* Client MULTI/EXEC state */
/*
 * 事务命令结构
 */
typedef struct multiCmd {
    // 执行命令的所有 key 对象
    robj **argv;
    // 参数的数量
    int argc;
    // 被执行的命令
    struct redisCommand *cmd;
} multiCmd;

/*
 * 事务状态结构
 */
typedef struct multiState {
    // 数组，保存着所有在事务队列中的命令
    multiCmd *commands;     /* Array of MULTI commands */
    // 队列中命令的数量
    int count;              /* Total number of MULTI commands */
} multiState;

/*
 * 记录客户端的阻塞状态
 */
typedef struct blockingState {
    // 阻塞客户端的任意多个 key
    dict *keys;             /* The keys we are waiting to terminate a blocking
                             * operation such as BLPOP. Otherwise NULL. */
    // 超时时间
    // 如果 UNIX 的当前时间大于等于这个值的话，
    // 那么取消对客户端的阻塞
    time_t timeout;         /* Blocking operation timeout. If UNIX current time
                             * is >= timeout then the operation timed out. */
    // 在阻塞被取消时接受元素的 key
    // 只用于 BRPOPLPUSH 命令
    robj *target;           /* The key that should receive the element,
                             * for BRPOPLPUSH. */
} blockingState;

/* The following structure represents a node in the server.ready_keys list,
 * where we accumulate all the keys that had clients blocked with a blocking
 * operation such as B[LR]POP, but received new data in the context of the
 * last executed command.
 *
 * After the execution of every command or script, we run this list to check
 * if as a result we should serve data to clients blocked, unblocking them.
 * Note that server.ready_keys will not have duplicates as there dictionary
 * also called ready_keys in every structure representing a Redis database,
 * where we make sure to remember if a given key was already added in the
 * server.ready_keys list. */
/*
 * 记录了已就绪 key 和它对应的 db
 */
typedef struct readyList {
    redisDb *db;
    robj *key;
} readyList;

/* With multiplexing we need to take per-clinet state.
 * Clients are taken in a liked list. */
/*
 * 客户端结构
 *
 * 为每个连接到服务器的客户端保存维持一个该结构的映射，
 * 从而实现多路复用。
 */
typedef struct redisClient {

    // socket 文件描述符
    int fd;

    // 指向当前目标数据库的指针
    redisDb *db;

    // 当前目标数据库的号码
    int dictid;

    // 查询缓存
    sds querybuf;
    size_t querybuf_peak;   /* Recent (100ms or more) peak of querybuf size */

    // 参数的个数
    int argc;

    // 字符串表示的命令，以及命令的参数
    robj **argv;

    // 命令，以及上个命令
    struct redisCommand *cmd, *lastcmd;

    // 回复类型
    int reqtype;
    int multibulklen;       /* number of multi bulk arguments left to read */
    long bulklen;           /* length of bulk argument in multi bulk request */

    // 保存回复的链表
    list *reply;
    // 链表中保存的所有回复的总字节大小
    unsigned long reply_bytes; /* Tot bytes of objects in reply list */

    // 统计数据
    int sentlen;
    time_t ctime;           /* Client creation time */
    time_t lastinteraction; /* time of the last interaction, used for timeout */
    time_t obuf_soft_limit_reached_time;
    int flags;              /* REDIS_SLAVE | REDIS_MONITOR | REDIS_MULTI ... */

    // 复制功能相关
    int slaveseldb;         /* slave selected db, if this client is a slave */
    int authenticated;      /* when requirepass is non-NULL */
    // 客户端当前的同步状态
    int replstate;          /* replication state if this is a slave */
    // 同步数据库的文件描述符
    int repldbfd;           /* replication DB file descriptor */
    // 同步数据库文件的偏移量
    long repldboff;         /* replication DB file offset */
    // 同步数据库文件的大小
    off_t repldbsize;       /* replication DB file size */
    int slave_listening_port; /* As configured with: SLAVECONF listening-port */

    // 事务实现
    multiState mstate;      /* MULTI/EXEC state */

    // 阻塞状态
    blockingState bpop;   /* blocking state */
    list *io_keys;          /* Keys this client is waiting to be loaded from the
                             * swap file in order to continue. */

    // 被监视的 KEY
    list *watched_keys;     /* Keys WATCHED for MULTI/EXEC CAS */

    // 订阅与发布
    dict *pubsub_channels;  /* channels a client is interested in (SUBSCRIBE) */
    list *pubsub_patterns;  /* patterns a client is interested in (SUBSCRIBE) */

    /* Response buffer */
    // 回复缓存的当前缓存
    int bufpos;
    // 回复缓存，可以保存多个回复
    char buf[REDIS_REPLY_CHUNK_BYTES];
} redisClient;

struct saveparam {
    time_t seconds;
    int changes;
};

/*
 * 共享对象
 */
struct sharedObjectsStruct {
    robj *crlf, *ok, *err, *emptybulk, *czero, *cone, *cnegone, *pong, *space,
    *colon, *nullbulk, *nullmultibulk, *queued,
    *emptymultibulk, *wrongtypeerr, *nokeyerr, *syntaxerr, *sameobjecterr,
    *outofrangeerr, *noscripterr, *loadingerr, *slowscripterr, *bgsaveerr,
    *masterdownerr, *roslaveerr, *execaborterr,
    *oomerr, *plus, *messagebulk, *pmessagebulk, *subscribebulk,
    *unsubscribebulk, *psubscribebulk, *punsubscribebulk, *del, *rpop, *lpop,
    *lpush,
    *select[REDIS_SHARED_SELECT_CMDS],
    *integers[REDIS_SHARED_INTEGERS],
    *mbulkhdr[REDIS_SHARED_BULKHDR_LEN], /* "*<value>\r\n" */
    *bulkhdr[REDIS_SHARED_BULKHDR_LEN];  /* "$<value>\r\n" */
};

/* ZSETs use a specialized version of Skiplists */
/*
 * 跳跃表节点
 */
typedef struct zskiplistNode {
    // member 对象
    robj *obj;
    // 分值
    double score;
    // 后退指针
    struct zskiplistNode *backward;
    // 层
    struct zskiplistLevel {
        // 前进指针
        struct zskiplistNode *forward;
        // 这个层跨越的节点数量
        unsigned int span;
    } level[];
} zskiplistNode;

/*
 * 跳跃表
 */
typedef struct zskiplist {
    // 头节点，尾节点
    struct zskiplistNode *header, *tail;
    // 节点数量
    unsigned long length;
    // 目前表内节点的最大层数
    int level;
} zskiplist;

/*
 * 有序集
 */
typedef struct zset {
    // 字典
    dict *dict;
    // 跳跃表
    zskiplist *zsl;
} zset;

typedef struct clientBufferLimitsConfig {
    unsigned long long hard_limit_bytes;
    unsigned long long soft_limit_bytes;
    time_t soft_limit_seconds;
} clientBufferLimitsConfig;

/* The redisOp structure defines a Redis Operation, that is an instance of
 * a command with an argument vector, database ID, propagation target
 * (REDIS_PROPAGATE_*), and command pointer.
 *
 * Currently only used to additionally propagate more commands to AOF/Replication
 * after the propagation of the executed command. */
typedef struct redisOp {
    robj **argv;
    int argc, dbid, target;
    struct redisCommand *cmd;
} redisOp;

/* Defines an array of Redis operations. There is an API to add to this
 * structure in a easy way.
 *
 * redisOpArrayInit();
 * redisOpArrayAppend();
 * redisOpArrayFree();
 */
typedef struct redisOpArray {
    redisOp *ops;
    int numops;
} redisOpArray;

/*-----------------------------------------------------------------------------
 * Redis cluster data structures
 *----------------------------------------------------------------------------*/

#define REDIS_CLUSTER_SLOTS 4096
#define REDIS_CLUSTER_OK 0          /* Everything looks ok */
#define REDIS_CLUSTER_FAIL 1        /* The cluster can't work */
#define REDIS_CLUSTER_NEEDHELP 2    /* The cluster works, but needs some help */
#define REDIS_CLUSTER_NAMELEN 40    /* sha1 hex length */
#define REDIS_CLUSTER_PORT_INCR 10000 /* Cluster port = baseport + PORT_INCR */

struct clusterNode;

/* clusterLink encapsulates everything needed to talk with a remote node. */
typedef struct clusterLink {
    int fd;                     /* TCP socket file descriptor */
    sds sndbuf;                 /* Packet send buffer */
    sds rcvbuf;                 /* Packet reception buffer */
    struct clusterNode *node;   /* Node related to this link if any, or NULL */
} clusterLink;

/* Node flags */
#define REDIS_NODE_MASTER 1     /* The node is a master */
#define REDIS_NODE_SLAVE 2      /* The node is a slave */
#define REDIS_NODE_PFAIL 4      /* Failure? Need acknowledge */
#define REDIS_NODE_FAIL 8       /* The node is believed to be malfunctioning */
#define REDIS_NODE_MYSELF 16    /* This node is myself */
#define REDIS_NODE_HANDSHAKE 32 /* We have still to exchange the first ping */
#define REDIS_NODE_NOADDR   64  /* We don't know the address of this node */
#define REDIS_NODE_MEET 128     /* Send a MEET message to this node */
#define REDIS_NODE_NULL_NAME "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"

struct clusterNode {
    char name[REDIS_CLUSTER_NAMELEN]; /* Node name, hex string, sha1-size */
    int flags;      /* REDIS_NODE_... */
    unsigned char slots[REDIS_CLUSTER_SLOTS/8]; /* slots handled by this node */
    int numslaves;  /* Number of slave nodes, if this is a master */
    struct clusterNode **slaves; /* pointers to slave nodes */
    struct clusterNode *slaveof; /* pointer to the master node */
    time_t ping_sent;       /* Unix time we sent latest ping */
    time_t pong_received;   /* Unix time we received the pong */
    char *configdigest;         /* Configuration digest of this node */
    time_t configdigest_ts;     /* Configuration digest timestamp */
    char ip[16];                /* Latest known IP address of this node */
    int port;                   /* Latest known port of this node */
    clusterLink *link;          /* TCP/IP link with this node */
};
typedef struct clusterNode clusterNode;

typedef struct {
    char *configfile;
    clusterNode *myself;  /* This node */
    int state;            /* REDIS_CLUSTER_OK, REDIS_CLUSTER_FAIL, ... */
    int node_timeout;
    dict *nodes;          /* Hash table of name -> clusterNode structures */
    clusterNode *migrating_slots_to[REDIS_CLUSTER_SLOTS];
    clusterNode *importing_slots_from[REDIS_CLUSTER_SLOTS];
    clusterNode *slots[REDIS_CLUSTER_SLOTS];
    zskiplist *slots_to_keys;
} clusterState;

/* Redis cluster messages header */

/* Note that the PING, PONG and MEET messages are actually the same exact
 * kind of packet. PONG is the reply to ping, in the extact format as a PING,
 * while MEET is a special PING that forces the receiver to add the sender
 * as a node (if it is not already in the list). */
#define CLUSTERMSG_TYPE_PING 0          /* Ping */
#define CLUSTERMSG_TYPE_PONG 1          /* Pong (reply to Ping) */
#define CLUSTERMSG_TYPE_MEET 2          /* Meet "let's join" message */
#define CLUSTERMSG_TYPE_FAIL 3          /* Mark node xxx as failing */
#define CLUSTERMSG_TYPE_PUBLISH 4       /* Pub/Sub Publish propatagion */

/* Initially we don't know our "name", but we'll find it once we connect
 * to the first node, using the getsockname() function. Then we'll use this
 * address for all the next messages. */
typedef struct {
    char nodename[REDIS_CLUSTER_NAMELEN];
    uint32_t ping_sent;
    uint32_t pong_received;
    char ip[16];    /* IP address last time it was seen */
    uint16_t port;  /* port last time it was seen */
    uint16_t flags;
    uint32_t notused; /* for 64 bit alignment */
} clusterMsgDataGossip;

typedef struct {
    char nodename[REDIS_CLUSTER_NAMELEN];
} clusterMsgDataFail;

typedef struct {
    uint32_t channel_len;
    uint32_t message_len;
    unsigned char bulk_data[8]; /* defined as 8 just for alignment concerns. */
} clusterMsgDataPublish;

union clusterMsgData {
    /* PING, MEET and PONG */
    struct {
        /* Array of N clusterMsgDataGossip structures */
        clusterMsgDataGossip gossip[1];
    } ping;

    /* FAIL */
    struct {
        clusterMsgDataFail about;
    } fail;

    /* PUBLISH */
    struct {
        clusterMsgDataPublish msg;
    } publish;
};

typedef struct {
    uint32_t totlen;    /* Total length of this message */
    uint16_t type;      /* Message type */
    uint16_t count;     /* Only used for some kind of messages. */
    char sender[REDIS_CLUSTER_NAMELEN]; /* Name of the sender node */
    unsigned char myslots[REDIS_CLUSTER_SLOTS/8];
    char slaveof[REDIS_CLUSTER_NAMELEN];
    char configdigest[32];
    uint16_t port;      /* Sender TCP base port */
    unsigned char state; /* Cluster state from the POV of the sender */
    unsigned char notused[5]; /* Reserved for future use. For alignment. */
    union clusterMsgData data;
} clusterMsg;

/*-----------------------------------------------------------------------------
 * Global server state
 *----------------------------------------------------------------------------*/

struct redisServer {
    /* General */

    // 数据库数组
    redisDb *db;

    // 命令表
    dict *commands;             /* Command table hash table */

    // 事件状态结构
    aeEventLoop *el;

    // LRU
    unsigned lruclock:22;       /* Clock incrementing every minute, for LRU */
    unsigned lruclock_padding:10;

    // 关闭标志
    int shutdown_asap;          /* SHUTDOWN needed ASAP */

    // 主动 rehash
    int activerehashing;        /* Incremental rehash in serverCron() */

    // 密码
    char *requirepass;          /* Pass for AUTH command, or NULL */

    // PID 文件路径
    char *pidfile;              /* PID file path */

    // 宿主架构字长
    int arch_bits;              /* 32 or 64 depending on sizeof(long) */

    // CRON 函数调用的次数
    int cronloops;              /* Number of times the cron function run */

    // 每次调用 exec 时都创建新 ID
    char runid[REDIS_RUN_ID_SIZE+1];  /* ID always different at every exec. */

    // 如果服务器为 SENTINEL ，那么为真
    int sentinel_mode;          /* True if this instance is a Sentinel. */

    /* Networking */
    // 监听端口
    int port;                   /* TCP listening port */
    // 绑定地址
    char *bindaddr;             /* Bind address or NULL */
    // 套接字路径
    char *unixsocket;           /* UNIX socket path */
    // 套接字权限
    mode_t unixsocketperm;      /* UNIX socket permission */
    int ipfd;                   /* TCP socket file descriptor */
    int sofd;                   /* Unix socket file descriptor */
    int cfd;                    /* Cluster bus lisetning socket */

    /* 客户端 */
    // 所有当前活动的客户端
    list *clients;              /* List of active clients */
    // 所有等待关闭的客户端
    list *clients_to_close;     /* Clients to close asynchronously */
    // 所有附属节点和 MONITOR
    list *slaves, *monitors;    /* List of slaves and MONITORs */
    // 当前客户端，只在创建崩溃报告时使用
    redisClient *current_client; /* Current client, only used on crash report */

    char neterr[ANET_ERR_LEN];   /* Error buffer for anet.c */
    dict *migrate_cached_sockets;/* MIGRATE cached sockets */

    /* RDB / AOF loading information */
    int loading;                /* We are loading data from disk if true */
    off_t loading_total_bytes;
    off_t loading_loaded_bytes;
    time_t loading_start_time;

    /* Fast pointers to often looked up command */
    struct redisCommand *delCommand, *multiCommand, *lpushCommand, *lpopCommand,
                        *rpopCommand;

    /* Fields used only for stats */
    time_t stat_starttime;          /* Server start time */
    long long stat_numcommands;     /* Number of processed commands */
    long long stat_numconnections;  /* Number of connections received */
    long long stat_expiredkeys;     /* Number of expired keys */
    long long stat_evictedkeys;     /* Number of evicted keys (maxmemory) */
    long long stat_keyspace_hits;   /* Number of successful lookups of keys */
    long long stat_keyspace_misses; /* Number of failed lookups of keys */
    size_t stat_peak_memory;        /* Max used memory record */
    long long stat_fork_time;       /* Time needed to perform latets fork() */
    long long stat_rejected_conn;   /* Clients rejected because of maxclients */

    // 保存慢查询日志的链表
    list *slowlog;                  /* SLOWLOG list of commands */

    // 慢查询日志的当前 id 值
    long long slowlog_entry_id;     /* SLOWLOG current entry ID */
    // 慢查询时间限制
    long long slowlog_log_slower_than; /* SLOWLOG time limit (to get logged) */
    // 慢查询日志的最大条目数量
    unsigned long slowlog_max_len;     /* SLOWLOG max number of items logged */

    /* The following two are used to track instantaneous "load" in terms
     * of operations per second. */
    long long ops_sec_last_sample_time; /* Timestamp of last sample (in ms) */
    long long ops_sec_last_sample_ops;  /* numcommands in last sample */
    long long ops_sec_samples[REDIS_OPS_SEC_SAMPLES];
    int ops_sec_idx;

    /* Configuration */
    int verbosity;                  /* Loglevel in redis.conf */
    int maxidletime;                /* Client timeout in seconds */
    size_t client_max_querybuf_len; /* Limit for client query buffer length */
    int dbnum;                      /* Total number of configured DBs */
    int daemonize;                  /* True if running as a daemon */
    clientBufferLimitsConfig client_obuf_limits[REDIS_CLIENT_LIMIT_NUM_CLASSES];

    /* AOF persistence */
    int aof_state;                  /* REDIS_AOF_(ON|OFF|WAIT_REWRITE) */
    int aof_fsync;                  /* Kind of fsync() policy */
    char *aof_filename;             /* Name of the AOF file */
    int aof_no_fsync_on_rewrite;    /* Don't fsync if a rewrite is in prog. */
    int aof_rewrite_perc;           /* Rewrite AOF if % growth is > M and... */
    off_t aof_rewrite_min_size;     /* the AOF file is at least N bytes. */
    off_t aof_rewrite_base_size;    /* AOF size on latest startup or rewrite. */
    off_t aof_current_size;         /* AOF current size. */
    int aof_rewrite_scheduled;      /* Rewrite once BGSAVE terminates. */
    pid_t aof_child_pid;            /* PID if rewriting process */
    list *aof_rewrite_buf_blocks;   /* Hold changes during an AOF rewrite. */
    sds aof_buf;      /* AOF buffer, written before entering the event loop */
    int aof_fd;       /* File descriptor of currently selected AOF file */
    int aof_selected_db; /* Currently selected DB in AOF */
    time_t aof_flush_postponed_start; /* UNIX time of postponed AOF flush */
    time_t aof_last_fsync;            /* UNIX time of last fsync() */
    time_t aof_rewrite_time_last;   /* Time used by last AOF rewrite run. */
    time_t aof_rewrite_time_start;  /* Current AOF rewrite start time. */
    int aof_lastbgrewrite_status;   /* REDIS_OK or REDIS_ERR */
    unsigned long aof_delayed_fsync;  /* delayed AOF fsync() counter */

    /* RDB persistence */
    long long dirty;                /* Changes to DB from the last save */
    long long dirty_before_bgsave;  /* Used to restore dirty on failed BGSAVE */
    pid_t rdb_child_pid;            /* PID of RDB saving child */
    struct saveparam *saveparams;   /* Save points array for RDB */
    int saveparamslen;              /* Number of saving points */
    char *rdb_filename;             /* Name of RDB file */
    int rdb_compression;            /* Use compression in RDB? */
    int rdb_checksum;               /* Use RDB checksum? */
    time_t lastsave;                /* Unix time of last save succeeede */
    time_t rdb_save_time_last;      /* Time used by last RDB save run. */
    time_t rdb_save_time_start;     /* Current RDB save start time. */
    int lastbgsave_status;          /* REDIS_OK or REDIS_ERR */
    int stop_writes_on_bgsave_err;  /* Don't allow writes if can't BGSAVE */

    /* Propagation of commands in AOF / replication */
    redisOpArray also_propagate;    /* Additional command to propagate. */
    /* Logging */
    char *logfile;                  /* Path of log file */
    int syslog_enabled;             /* Is syslog enabled? */
    char *syslog_ident;             /* Syslog ident */
    int syslog_facility;            /* Syslog facility */

    /* Slave specific fields */
    char *masterauth;               /* AUTH with this password with master */
    char *masterhost;               /* Hostname of master */
    int masterport;                 /* Port of master */
    int repl_ping_slave_period;     /* Master pings the slave every N seconds */
    int repl_timeout;               /* Timeout after N seconds of master idle */
    redisClient *master;     /* Client that is master for this slave */
    int repl_syncio_timeout; /* Timeout for synchronous I/O calls */
    int repl_state;          /* Replication status if the instance is a slave */
    off_t repl_transfer_size; /* Size of RDB to read from master during sync. */
    off_t repl_transfer_read; /* Amount of RDB read from master during sync. */
    off_t repl_transfer_last_fsync_off; /* Offset when we fsync-ed last time. */
    int repl_transfer_s;     /* Slave -> Master SYNC socket */
    int repl_transfer_fd;    /* Slave -> Master SYNC temp file descriptor */
    char *repl_transfer_tmpfile; /* Slave-> master SYNC temp file name */
    time_t repl_transfer_lastio; /* Unix time of the latest read, for timeout */
    int repl_serve_stale_data; /* Serve stale data when link is down? */
    int repl_slave_ro;          /* Slave is read only? */
    time_t repl_down_since; /* Unix time at which link with master went down */
    int slave_priority;             /* Reported in INFO and used by Sentinel. */

    /* Limits */
    unsigned int maxclients;        /* Max number of simultaneous clients */
    unsigned long long maxmemory;   /* Max number of memory bytes to use */
    int maxmemory_policy;           /* Policy for key evition */
    int maxmemory_samples;          /* Pricision of random sampling */

    /* Blocked clients */
    unsigned int bpop_blocked_clients; /* Number of clients blocked by lists */
    // 要在下一次事件 lopp 前取消阻塞的所有客户端
    list *unblocked_clients; /* list of clients to unblock before next loop */
    list *ready_keys;        /* List of readyList structures for BLPOP & co */

    /* Sort parameters - qsort_r() is only available under BSD so we
     * have to take this state global, in order to pass it to sortCompare() */
    int sort_desc;
    int sort_alpha;
    int sort_bypattern;

    /* Zip structure config, see redis.conf for more information  */
    size_t hash_max_ziplist_entries;
    size_t hash_max_ziplist_value;
    size_t list_max_ziplist_entries;
    size_t list_max_ziplist_value;
    size_t set_max_intset_entries;
    size_t zset_max_ziplist_entries;
    size_t zset_max_ziplist_value;
    time_t unixtime;        /* Unix time sampled every second. */

    /* Pubsub */
    // 频道
    dict *pubsub_channels;  /* Map channels to list of subscribed clients */
    // 模式
    list *pubsub_patterns;  /* A list of pubsub_patterns */

    /* Cluster */
    int cluster_enabled;    /* Is cluster enabled? */
    clusterState cluster;   /* State of the cluster */

    /* Scripting */
    lua_State *lua; /* The Lua interpreter. We use just one for all clients */
    redisClient *lua_client;   /* The "fake client" to query Redis from Lua */
    redisClient *lua_caller;   /* The client running EVAL right now, or NULL */
    dict *lua_scripts;         /* A dictionary of SHA1 -> Lua scripts */
    long long lua_time_limit;  /* Script timeout in seconds */
    long long lua_time_start;  /* Start time of script */
    int lua_write_dirty;  /* True if a write command was called during the
                             execution of the current script. */
    int lua_random_dirty; /* True if a random command was called during the
                             execution of the current script. */
    int lua_timedout;     /* True if we reached the time limit for script
                             execution. */
    int lua_kill;         /* Kill the script if true. */

    /* Assert & bug reportign */
    char *assert_failed;
    char *assert_file;
    int assert_line;
    int bug_report_start; /* True if bug report header was already logged. */
    int watchdog_period;  /* Software watchdog period in ms. 0 = off */
};

/*
 * 订阅模式
 */
typedef struct pubsubPattern {
    // 订阅模式的客户端
    redisClient *client;
    // 订阅的模式
    robj *pattern;
} pubsubPattern;

typedef void redisCommandProc(redisClient *c);
typedef int *redisGetKeysProc(struct redisCommand *cmd, robj **argv, int argc, int *numkeys, int flags);
struct redisCommand {
    // 命令的名字
    char *name;
    // 命令的实现函数
    redisCommandProc *proc;
    // 命令所需的参数数量
    int arity;
    // 字符形式表示的 FLAG 值
    char *sflags; /* Flags as string represenation, one char per flag. */
    // 实际的 FLAG 值，由 sflags 计算得出
    int flags;    /* The actual flags, obtained from the 'sflags' field. */
    /* Use a function to determine keys arguments in a command line.
     * Used for Redis Cluster redirect. */
    // 可选，在以下三个参数不足以决定命令的 key 参数时使用
    redisGetKeysProc *getkeys_proc;
    /* What keys should be loaded in background when calling this command? */
    // 第一个 key 的位置
    int firstkey; /* The first argument that's a key (0 = no keys) */
    // 第二个 key 的位置
    int lastkey;  /* THe last argument that's a key */
    // 两个 key 之间的空隔
    int keystep;  /* The step between first and last key */
    // 这个命令被执行所耗费的总毫秒数
    long long microseconds;
    // 这个命令被调用的总次数
    long long calls;
};

struct redisFunctionSym {
    char *name;
    unsigned long pointer;
};

typedef struct _redisSortObject {
    robj *obj;
    union {
        double score;
        robj *cmpobj;
    } u;
} redisSortObject;

typedef struct _redisSortOperation {
    int type;
    robj *pattern;
} redisSortOperation;

/* Structure to hold list iteration abstraction. */
typedef struct {
    robj *subject;
    unsigned char encoding;
    unsigned char direction; /* Iteration direction */
    unsigned char *zi;
    listNode *ln;
} listTypeIterator;

/* Structure for an entry while iterating over a list. */
typedef struct {
    listTypeIterator *li;
    unsigned char *zi;  /* Entry in ziplist */
    listNode *ln;       /* Entry in linked list */
} listTypeEntry;

/* Structure to hold set iteration abstraction. */
typedef struct {
    robj *subject;
    int encoding;
    int ii; /* intset iterator */
    dictIterator *di;
} setTypeIterator;

/* Structure to hold hash iteration abstration. Note that iteration over
 * hashes involves both fields and values. Because it is possible that
 * not both are required, store pointers in the iterator to avoid
 * unnecessary memory allocation for fields/values. */
/*
 * 哈希类型对象的迭代器
 */
typedef struct {
    robj *subject;
    int encoding;

    // 用于遍历 ziplist
    unsigned char *fptr, *vptr;

    // 用于遍历字典
    dictIterator *di;
    dictEntry *de;
} hashTypeIterator;

#define REDIS_HASH_KEY 1
#define REDIS_HASH_VALUE 2

/*-----------------------------------------------------------------------------
 * Extern declarations
 *----------------------------------------------------------------------------*/

extern struct redisServer server;
extern struct sharedObjectsStruct shared;
extern dictType setDictType;
extern dictType zsetDictType;
extern dictType clusterNodesDictType;
extern dictType dbDictType;
extern dictType shaScriptObjectDictType;
extern double R_Zero, R_PosInf, R_NegInf, R_Nan;
extern dictType hashDictType;

/*-----------------------------------------------------------------------------
 * Functions prototypes
 *----------------------------------------------------------------------------*/

/* Utils */
long long ustime(void);
long long mstime(void);
void getRandomHexChars(char *p, unsigned int len);
uint64_t crc64(uint64_t crc, const unsigned char *s, uint64_t l);
void exitFromChild(int retcode);

/* networking.c -- Networking and Client related operations */
redisClient *createClient(int fd);
void closeTimedoutClients(void);
void freeClient(redisClient *c);
void resetClient(redisClient *c);
void sendReplyToClient(aeEventLoop *el, int fd, void *privdata, int mask);
void addReply(redisClient *c, robj *obj);
void *addDeferredMultiBulkLength(redisClient *c);
void setDeferredMultiBulkLength(redisClient *c, void *node, long length);
void addReplySds(redisClient *c, sds s);
void processInputBuffer(redisClient *c);
void acceptTcpHandler(aeEventLoop *el, int fd, void *privdata, int mask);
void acceptUnixHandler(aeEventLoop *el, int fd, void *privdata, int mask);
void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask);
void addReplyBulk(redisClient *c, robj *obj);
void addReplyBulkCString(redisClient *c, char *s);
void addReplyBulkCBuffer(redisClient *c, void *p, size_t len);
void addReplyBulkLongLong(redisClient *c, long long ll);
void acceptHandler(aeEventLoop *el, int fd, void *privdata, int mask);
void addReply(redisClient *c, robj *obj);
void addReplySds(redisClient *c, sds s);
void addReplyError(redisClient *c, char *err);
void addReplyStatus(redisClient *c, char *status);
void addReplyDouble(redisClient *c, double d);
void addReplyLongLong(redisClient *c, long long ll);
void addReplyMultiBulkLen(redisClient *c, long length);
void copyClientOutputBuffer(redisClient *dst, redisClient *src);
void *dupClientReplyValue(void *o);
void getClientsMaxBuffers(unsigned long *longest_output_list,
                          unsigned long *biggest_input_buffer);
sds getClientInfoString(redisClient *client);
sds getAllClientsInfoString(void);
void rewriteClientCommandVector(redisClient *c, int argc, ...);
void rewriteClientCommandArgument(redisClient *c, int i, robj *newval);
unsigned long getClientOutputBufferMemoryUsage(redisClient *c);
void freeClientsInAsyncFreeQueue(void);
void asyncCloseClientOnOutputBufferLimitReached(redisClient *c);
int getClientLimitClassByName(char *name);
char *getClientLimitClassName(int class);
void flushSlavesOutputBuffers(void);
void disconnectSlaves(void);

#ifdef __GNUC__
void addReplyErrorFormat(redisClient *c, const char *fmt, ...)
    __attribute__((format(printf, 2, 3)));
void addReplyStatusFormat(redisClient *c, const char *fmt, ...)
    __attribute__((format(printf, 2, 3)));
#else
void addReplyErrorFormat(redisClient *c, const char *fmt, ...);
void addReplyStatusFormat(redisClient *c, const char *fmt, ...);
#endif

/* List data type */
void listTypeTryConversion(robj *subject, robj *value);
void listTypePush(robj *subject, robj *value, int where);
robj *listTypePop(robj *subject, int where);
unsigned long listTypeLength(robj *subject);
listTypeIterator *listTypeInitIterator(robj *subject, long index, unsigned char direction);
void listTypeReleaseIterator(listTypeIterator *li);
int listTypeNext(listTypeIterator *li, listTypeEntry *entry);
robj *listTypeGet(listTypeEntry *entry);
void listTypeInsert(listTypeEntry *entry, robj *value, int where);
int listTypeEqual(listTypeEntry *entry, robj *o);
void listTypeDelete(listTypeEntry *entry);
void listTypeConvert(robj *subject, int enc);
void unblockClientWaitingData(redisClient *c);
void handleClientsBlockedOnLists(void);
void popGenericCommand(redisClient *c, int where);

/* MULTI/EXEC/WATCH... */
void unwatchAllKeys(redisClient *c);
void initClientMultiState(redisClient *c);
void freeClientMultiState(redisClient *c);
void queueMultiCommand(redisClient *c);
void touchWatchedKey(redisDb *db, robj *key);
void touchWatchedKeysOnFlush(int dbid);
void discardTransaction(redisClient *c);
void flagTransaction(redisClient *c);

/* Redis object implementation */
void decrRefCount(void *o);
void incrRefCount(robj *o);
robj *resetRefCount(robj *obj);
void freeStringObject(robj *o);
void freeListObject(robj *o);
void freeSetObject(robj *o);
void freeZsetObject(robj *o);
void freeHashObject(robj *o);
robj *createObject(int type, void *ptr);
robj *createStringObject(char *ptr, size_t len);
robj *dupStringObject(robj *o);
int isObjectRepresentableAsLongLong(robj *o, long long *llongval);
robj *tryObjectEncoding(robj *o);
robj *getDecodedObject(robj *o);
size_t stringObjectLen(robj *o);
robj *createStringObjectFromLongLong(long long value);
robj *createStringObjectFromLongDouble(long double value);
robj *createListObject(void);
robj *createZiplistObject(void);
robj *createSetObject(void);
robj *createIntsetObject(void);
robj *createHashObject(void);
robj *createZsetObject(void);
robj *createZsetZiplistObject(void);
int getLongFromObjectOrReply(redisClient *c, robj *o, long *target, const char *msg);
int checkType(redisClient *c, robj *o, int type);
int getLongLongFromObjectOrReply(redisClient *c, robj *o, long long *target, const char *msg);
int getDoubleFromObjectOrReply(redisClient *c, robj *o, double *target, const char *msg);
int getLongLongFromObject(robj *o, long long *target);
int getLongDoubleFromObject(robj *o, long double *target);
int getLongDoubleFromObjectOrReply(redisClient *c, robj *o, long double *target, const char *msg);
char *strEncoding(int encoding);
int compareStringObjects(robj *a, robj *b);
int equalStringObjects(robj *a, robj *b);
unsigned long estimateObjectIdleTime(robj *o);

/* Synchronous I/O with timeout */
ssize_t syncWrite(int fd, char *ptr, ssize_t size, long long timeout);
ssize_t syncRead(int fd, char *ptr, ssize_t size, long long timeout);
ssize_t syncReadLine(int fd, char *ptr, ssize_t size, long long timeout);

/* Replication */
void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc);
void replicationFeedMonitors(redisClient *c, list *monitors, int dictid, robj **argv, int argc);
void updateSlavesWaitingBgsave(int bgsaveerr);
void replicationCron(void);

/* Generic persistence functions */
void startLoading(FILE *fp);
void loadingProgress(off_t pos);
void stopLoading(void);

/* RDB persistence */
#include "rdb.h"

/* AOF persistence */
void flushAppendOnlyFile(int force);
void feedAppendOnlyFile(struct redisCommand *cmd, int dictid, robj **argv, int argc);
void aofRemoveTempFile(pid_t childpid);
int rewriteAppendOnlyFileBackground(void);
int loadAppendOnlyFile(char *filename);
void stopAppendOnly(void);
int startAppendOnly(void);
void backgroundRewriteDoneHandler(int exitcode, int bysignal);
void aofRewriteBufferReset(void);
unsigned long aofRewriteBufferSize(void);

/* Sorted sets data type */

/* Struct to hold a inclusive/exclusive range spec. */
/*
 * 用于保存范围值的结构
 */
typedef struct {
    double min, max;
    // min 和 max 是否包括在内？
    int minex, maxex; /* are min or max exclusive? */
} zrangespec;

zskiplist *zslCreate(void);
void zslFree(zskiplist *zsl);
zskiplistNode *zslInsert(zskiplist *zsl, double score, robj *obj);
unsigned char *zzlInsert(unsigned char *zl, robj *ele, double score);
int zslDelete(zskiplist *zsl, double score, robj *obj);
zskiplistNode *zslFirstInRange(zskiplist *zsl, zrangespec range);
double zzlGetScore(unsigned char *sptr);
void zzlNext(unsigned char *zl, unsigned char **eptr, unsigned char **sptr);
void zzlPrev(unsigned char *zl, unsigned char **eptr, unsigned char **sptr);
unsigned int zsetLength(robj *zobj);
void zsetConvert(robj *zobj, int encoding);

/* Core functions */
int freeMemoryIfNeeded(void);
int processCommand(redisClient *c);
void setupSignalHandlers(void);
struct redisCommand *lookupCommand(sds name);
struct redisCommand *lookupCommandByCString(char *s);
void call(redisClient *c, int flags);
void propagate(struct redisCommand *cmd, int dbid, robj **argv, int argc, int flags);
void alsoPropagate(struct redisCommand *cmd, int dbid, robj **argv, int argc, int target);
int prepareForShutdown();
void redisLog(int level, const char *fmt, ...);
void redisLogRaw(int level, const char *msg);
void redisLogFromHandler(int level, const char *msg);
void usage();
void updateDictResizePolicy(void);
int htNeedsResize(dict *dict);
void oom(const char *msg);
void populateCommandTable(void);
void resetCommandTableStats(void);

/* Set data type */
robj *setTypeCreate(robj *value);
int setTypeAdd(robj *subject, robj *value);
int setTypeRemove(robj *subject, robj *value);
int setTypeIsMember(robj *subject, robj *value);
setTypeIterator *setTypeInitIterator(robj *subject);
void setTypeReleaseIterator(setTypeIterator *si);
int setTypeNext(setTypeIterator *si, robj **objele, int64_t *llele);
robj *setTypeNextObject(setTypeIterator *si);
int setTypeRandomElement(robj *setobj, robj **objele, int64_t *llele);
unsigned long setTypeSize(robj *subject);
void setTypeConvert(robj *subject, int enc);

/* Hash data type */
void hashTypeConvert(robj *o, int enc);
void hashTypeTryConversion(robj *subject, robj **argv, int start, int end);
void hashTypeTryObjectEncoding(robj *subject, robj **o1, robj **o2);
robj *hashTypeGetObject(robj *o, robj *key);
int hashTypeExists(robj *o, robj *key);
int hashTypeSet(robj *o, robj *key, robj *value);
int hashTypeDelete(robj *o, robj *key);
unsigned long hashTypeLength(robj *o);
hashTypeIterator *hashTypeInitIterator(robj *subject);
void hashTypeReleaseIterator(hashTypeIterator *hi);
int hashTypeNext(hashTypeIterator *hi);
void hashTypeCurrentFromZiplist(hashTypeIterator *hi, int what,
                                unsigned char **vstr,
                                unsigned int *vlen,
                                long long *vll);
void hashTypeCurrentFromHashTable(hashTypeIterator *hi, int what, robj **dst);
robj *hashTypeCurrentObject(hashTypeIterator *hi, int what);
robj *hashTypeLookupWriteOrCreate(redisClient *c, robj *key);

/* Pub / Sub */
int pubsubUnsubscribeAllChannels(redisClient *c, int notify);
int pubsubUnsubscribeAllPatterns(redisClient *c, int notify);
void freePubsubPattern(void *p);
int listMatchPubsubPattern(void *a, void *b);
int pubsubPublishMessage(robj *channel, robj *message);

/* Configuration */
void loadServerConfig(char *filename, char *options);
void appendServerSaveParams(time_t seconds, int changes);
void resetServerSaveParams();

/* db.c -- Keyspace access API */
int removeExpire(redisDb *db, robj *key);
void propagateExpire(redisDb *db, robj *key);
int expireIfNeeded(redisDb *db, robj *key);
long long getExpire(redisDb *db, robj *key);
void setExpire(redisDb *db, robj *key, long long when);
robj *lookupKey(redisDb *db, robj *key);
robj *lookupKeyRead(redisDb *db, robj *key);
robj *lookupKeyWrite(redisDb *db, robj *key);
robj *lookupKeyReadOrReply(redisClient *c, robj *key, robj *reply);
robj *lookupKeyWriteOrReply(redisClient *c, robj *key, robj *reply);
void dbAdd(redisDb *db, robj *key, robj *val);
void dbOverwrite(redisDb *db, robj *key, robj *val);
void setKey(redisDb *db, robj *key, robj *val);
int dbExists(redisDb *db, robj *key);
robj *dbRandomKey(redisDb *db);
int dbDelete(redisDb *db, robj *key);
long long emptyDb();
int selectDb(redisClient *c, int id);
void signalModifiedKey(redisDb *db, robj *key);
void signalFlushedDb(int dbid);
unsigned int GetKeysInSlot(unsigned int hashslot, robj **keys, unsigned int count);

/* API to get key arguments from commands */
#define REDIS_GETKEYS_ALL 0
#define REDIS_GETKEYS_PRELOAD 1
int *getKeysFromCommand(struct redisCommand *cmd, robj **argv, int argc, int *numkeys, int flags);
void getKeysFreeResult(int *result);
int *noPreloadGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *numkeys, int flags);
int *renameGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *numkeys, int flags);
int *zunionInterGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *numkeys, int flags);

/* Cluster */
void clusterInit(void);
unsigned short crc16(const char *buf, int len);
unsigned int keyHashSlot(char *key, int keylen);
clusterNode *createClusterNode(char *nodename, int flags);
int clusterAddNode(clusterNode *node);
void clusterCron(void);
clusterNode *getNodeByQuery(redisClient *c, struct redisCommand *cmd, robj **argv, int argc, int *hashslot, int *ask);
void clusterPropagatePublish(robj *channel, robj *message);
void migrateCloseTimedoutSockets(void);

/* Sentinel */
void initSentinelConfig(void);
void initSentinel(void);
void sentinelTimer(void);
char *sentinelHandleConfiguration(char **argv, int argc);

/* Scripting */
void scriptingInit(void);

/* Git SHA1 */
char *redisGitSHA1(void);
char *redisGitDirty(void);
uint64_t redisBuildId(void);

/* Commands prototypes */
void authCommand(redisClient *c);
void pingCommand(redisClient *c);
void echoCommand(redisClient *c);
void setCommand(redisClient *c);
void setnxCommand(redisClient *c);
void setexCommand(redisClient *c);
void psetexCommand(redisClient *c);
void getCommand(redisClient *c);
void delCommand(redisClient *c);
void existsCommand(redisClient *c);
void setbitCommand(redisClient *c);
void getbitCommand(redisClient *c);
void setrangeCommand(redisClient *c);
void getrangeCommand(redisClient *c);
void incrCommand(redisClient *c);
void decrCommand(redisClient *c);
void incrbyCommand(redisClient *c);
void decrbyCommand(redisClient *c);
void incrbyfloatCommand(redisClient *c);
void selectCommand(redisClient *c);
void randomkeyCommand(redisClient *c);
void keysCommand(redisClient *c);
void dbsizeCommand(redisClient *c);
void lastsaveCommand(redisClient *c);
void saveCommand(redisClient *c);
void bgsaveCommand(redisClient *c);
void bgrewriteaofCommand(redisClient *c);
void shutdownCommand(redisClient *c);
void moveCommand(redisClient *c);
void renameCommand(redisClient *c);
void renamenxCommand(redisClient *c);
void lpushCommand(redisClient *c);
void rpushCommand(redisClient *c);
void lpushxCommand(redisClient *c);
void rpushxCommand(redisClient *c);
void linsertCommand(redisClient *c);
void lpopCommand(redisClient *c);
void rpopCommand(redisClient *c);
void llenCommand(redisClient *c);
void lindexCommand(redisClient *c);
void lrangeCommand(redisClient *c);
void ltrimCommand(redisClient *c);
void typeCommand(redisClient *c);
void lsetCommand(redisClient *c);
void saddCommand(redisClient *c);
void sremCommand(redisClient *c);
void smoveCommand(redisClient *c);
void sismemberCommand(redisClient *c);
void scardCommand(redisClient *c);
void spopCommand(redisClient *c);
void srandmemberCommand(redisClient *c);
void sinterCommand(redisClient *c);
void sinterstoreCommand(redisClient *c);
void sunionCommand(redisClient *c);
void sunionstoreCommand(redisClient *c);
void sdiffCommand(redisClient *c);
void sdiffstoreCommand(redisClient *c);
void syncCommand(redisClient *c);
void flushdbCommand(redisClient *c);
void flushallCommand(redisClient *c);
void sortCommand(redisClient *c);
void lremCommand(redisClient *c);
void rpoplpushCommand(redisClient *c);
void infoCommand(redisClient *c);
void mgetCommand(redisClient *c);
void monitorCommand(redisClient *c);
void expireCommand(redisClient *c);
void expireatCommand(redisClient *c);
void pexpireCommand(redisClient *c);
void pexpireatCommand(redisClient *c);
void getsetCommand(redisClient *c);
void ttlCommand(redisClient *c);
void pttlCommand(redisClient *c);
void persistCommand(redisClient *c);
void slaveofCommand(redisClient *c);
void debugCommand(redisClient *c);
void msetCommand(redisClient *c);
void msetnxCommand(redisClient *c);
void zaddCommand(redisClient *c);
void zincrbyCommand(redisClient *c);
void zrangeCommand(redisClient *c);
void zrangebyscoreCommand(redisClient *c);
void zrevrangebyscoreCommand(redisClient *c);
void zcountCommand(redisClient *c);
void zrevrangeCommand(redisClient *c);
void zcardCommand(redisClient *c);
void zremCommand(redisClient *c);
void zscoreCommand(redisClient *c);
void zremrangebyscoreCommand(redisClient *c);
void multiCommand(redisClient *c);
void execCommand(redisClient *c);
void discardCommand(redisClient *c);
void blpopCommand(redisClient *c);
void brpopCommand(redisClient *c);
void brpoplpushCommand(redisClient *c);
void appendCommand(redisClient *c);
void strlenCommand(redisClient *c);
void zrankCommand(redisClient *c);
void zrevrankCommand(redisClient *c);
void hsetCommand(redisClient *c);
void hsetnxCommand(redisClient *c);
void hgetCommand(redisClient *c);
void hmsetCommand(redisClient *c);
void hmgetCommand(redisClient *c);
void hdelCommand(redisClient *c);
void hlenCommand(redisClient *c);
void zremrangebyrankCommand(redisClient *c);
void zunionstoreCommand(redisClient *c);
void zinterstoreCommand(redisClient *c);
void hkeysCommand(redisClient *c);
void hvalsCommand(redisClient *c);
void hgetallCommand(redisClient *c);
void hexistsCommand(redisClient *c);
void configCommand(redisClient *c);
void hincrbyCommand(redisClient *c);
void hincrbyfloatCommand(redisClient *c);
void subscribeCommand(redisClient *c);
void unsubscribeCommand(redisClient *c);
void psubscribeCommand(redisClient *c);
void punsubscribeCommand(redisClient *c);
void publishCommand(redisClient *c);
void watchCommand(redisClient *c);
void unwatchCommand(redisClient *c);
void clusterCommand(redisClient *c);
void restoreCommand(redisClient *c);
void migrateCommand(redisClient *c);
void askingCommand(redisClient *c);
void dumpCommand(redisClient *c);
void objectCommand(redisClient *c);
void clientCommand(redisClient *c);
void evalCommand(redisClient *c);
void evalShaCommand(redisClient *c);
void scriptCommand(redisClient *c);
void timeCommand(redisClient *c);
void bitopCommand(redisClient *c);
void bitcountCommand(redisClient *c);
void replconfCommand(redisClient *c);

#if defined(__GNUC__)
void *calloc(size_t count, size_t size) __attribute__ ((deprecated));
void free(void *ptr) __attribute__ ((deprecated));
void *malloc(size_t size) __attribute__ ((deprecated));
void *realloc(void *ptr, size_t size) __attribute__ ((deprecated));
#endif

/* Debugging stuff */
void _redisAssertWithInfo(redisClient *c, robj *o, char *estr, char *file, int line);
void _redisAssert(char *estr, char *file, int line);
void _redisPanic(char *msg, char *file, int line);
void bugReportStart(void);
void redisLogObjectDebugInfo(robj *o);
void sigsegvHandler(int sig, siginfo_t *info, void *secret);
sds genRedisInfoString(char *section);
void enableWatchdog(int period);
void disableWatchdog(void);
void watchdogScheduleSignal(int period);
void redisLogHexDump(int level, char *descr, void *value, size_t len);

#define redisDebug(fmt, ...) \
    printf("DEBUG %s:%d > " fmt "\n", __FILE__, __LINE__, __VA_ARGS__)
#define redisDebugMark() \
    printf("-- MARK %s:%d --\n", __FILE__, __LINE__)

#endif