redis源码之dict

typedef struct redisDb {
    dict *dict;                /* The keyspace for this DB   字典数据结构，非常重要*/
    dict *expires;             /* Timeout of keys with a timeout set   过期时间*/
    dict *blocking_keys;       /* Keys with clients waiting for data (BLPOP)  list一些数据结构中用到的阻塞api*/
    dict *ready_keys;          /* Blocked keys that received a PUSH */
    dict *watched_keys;        /* WATCHED keys for MULTI/EXEC CAS  事务相关处理 */
    int id;                    /* Database ID */
    long long avg_ttl;         /* Average TTL, just for stats */
    unsigned long expires_cursor; /* Cursor of the active expire cycle. */
    list *defrag_later;        /* List of key names to attempt to defrag one by one, gradually. */
} redisDb;

typedef struct dict {
    dictType *type;  //
    void *privdata;  
    dictht ht[2];   //hashtable,每个dict都有两个这样的数据结构，主要用于hash扩容
    long rehashidx; /* rehashing not in progress if rehashidx == -1  rehash的作用  防止链表无限增长*/
    unsigned long iterators;/* number of iterators currently running   遍历记录的一些字段*/
} dict;

typedef struct dictType {
    uint64_t (*hashFunction)(const void *key);
    void *(*keyDup)(void *privdata, const void *key); //key用于数据类型的复制
    void *(*valDup)(void *privdata, const void *obj); //value用于数据类型的复制
    int (*keyCompare)(void *privdata, const void *key1, const void *key2);//hash冲突的时候需要在冲突的值里面一个一个的对比
    void (*keyDestructor)(void *privdata, void *key);
    void (*valDestructor)(void *privdata, void *obj);
} dictType;

typedef struct dictht {
    dictEntry **table; //指向数组的首地址  是健值对的核心结构
    unsigned long size; //数组的长度
    unsigned long sizemask;//恒等于size-1
    unsigned long used;
} dictht;

typedef struct  {
    void *key; //指向SDS的数据结构
    union { //联合体表示value类型,只会用到一个字段
        void *val;   //指向redis对象 redisObject
        uint64_t u64;
        int64_t s64;
        double d;  
    } v;
    struct dictEntry *next;  //头插法解决hash冲突
} dictEntry;

typedef struct redisObject {
    unsigned type:4; //当前对象类型 list  string hash set zset等
    unsigned encoding:4;//redis做的底层优化(编码)
    unsigned lru:LRU_BITS;/* LRU time (relative to global lru_clock) or
                           * LFU data (least significant 8 bits frequency
                           * and most significant 16 bits access time). */
    int refcount;
    void *ptr;
} robj;

127.0.0.1:6379> set type-int 12345
OK
127.0.0.1:6379> object encoding type-int
"int"
//返回的encoding类型是int
127.0.0.1:6379> set type-int-long 12345678901234567890
OK
127.0.0.1:6379> object encoding type-int-long
"embstr"
//返回的encoding类型是embstr

if (len <= 20 && string2l(s, len, &value))

127.0.0.1:6379> set type-str-short xxx
OK
127.0.0.1:6379> object encoding type-str-short
"embstr"




127.0.0.1:6379> set type-str-long xxxxxxxxxx-xxxxxxxxxx-xxxxxxxxxx-xxxxxxxxxx-x
//字符串长度45
127.0.0.1:6379> object encoding type-str-long
"raw"



127.0.0.1:6379> set type-str-long2 xxxxxxxxxx-xxxxxxxxxx-xxxxxxxxxx-xxxxxxxxxx-
//字符串长度44
127.0.0.1:6379> object encoding type-str-long2
"embstr"

typedef struct redisObject {
    unsigned type:4;  //4bit
    unsigned encoding:4; //4bit
    unsigned lru:LRU_BITS; //24bit
    int refcount;   //4byte
    void *ptr;   //8byte
} robj;