Redis 数据类型 #

typedef struct redisObject {
    unsigned type:4;      // 表示字符串、列表、集合、有序集合和哈希表类型
    unsigned encoding:4;  // 某一种类型的对象，在不同情况下可能采用不同的数据结构存储
    /*
     * LRU: 如果数据最近被访问过，那么将来被访问的几率也更高，此时lru字段存储的是对象访问时间
     * LFU: 如果数据过去被访问多次，那么将来被访问的频率也更高，此时lru字段存储的是上次访问时间与访问次数
     */
    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; // 当前对象的引用次数
    void *ptr;    // 指向实际存储的某一种数据结构
} robj;

#define OBJ_STRING 0    /* String object. */
#define OBJ_LIST 1      /* List object. */
#define OBJ_SET 2       /* Set object. */
#define OBJ_ZSET 3      /* Sorted set object. */
#define OBJ_HASH 4      /* Hash object. */
#define OBJ_MODULE 5    /* Module object. */
#define OBJ_STREAM 6    /* Stream object. */

#define OBJ_ENCODING_RAW 0     /* Raw representation */
#define OBJ_ENCODING_INT 1     /* Encoded as integer */
#define OBJ_ENCODING_HT 2      /* Encoded as hash table */
#define OBJ_ENCODING_ZIPMAP 3  /* No longer used: old hash encoding. */
#define OBJ_ENCODING_LINKEDLIST 4 /* No longer used: old list encoding. */
#define OBJ_ENCODING_ZIPLIST 5 /* No longer used: old list/hash/zset encoding. */
#define OBJ_ENCODING_INTSET 6  /* Encoded as intset */
#define OBJ_ENCODING_SKIPLIST 7  /* Encoded as skiplist */
#define OBJ_ENCODING_EMBSTR 8  /* Embedded sds string encoding */
#define OBJ_ENCODING_QUICKLIST 9 /* Encoded as linked list of listpacks */
#define OBJ_ENCODING_STREAM 10 /* Encoded as a radix tree of listpacks */
#define OBJ_ENCODING_LISTPACK 11 /* Encoded as a listpack */