redis源码阅读笔记----dict.c

dict是redis中的基本数据结构，源码中是通过hash表来实现的。项目将挑选几个主要函数和大家分享下redis源码的简洁。

对外提供增删改查的接口，如下

/* API */
static unsigned int dictGenHashFunction(const unsigned char *buf, int len);
static dict *dictCreate(dictType *type, void *privDataPtr);
static int dictExpand(dict *ht, unsigned long size);
static int dictAdd(dict *ht, void *key, void *val);
static int dictReplace(dict *ht, void *key, void *val);
static int dictDelete(dict *ht, const void *key);
static void dictRelease(dict *ht);
static dictEntry * dictFind(dict *ht, const void *key);
static dictIterator *dictGetIterator(dict *ht);
static dictEntry *dictNext(dictIterator *iter);
static void dictReleaseIterator(dictIterator *iter);

下面就着源码和大家分享下redis源码的理解

先看dict的数据结构如下

typedef struct dictType {
    unsigned int (*hashFunction)(const void *key);
    void *(*keyDup)(void *privdata, const void *key);
    void *(*valDup)(void *privdata, const void *obj);
    int (*keyCompare)(void *privdata, const void *key1, const void *key2);
    void (*keyDestructor)(void *privdata, void *key);
    void (*valDestructor)(void *privdata, void *obj);
} dictType;


typedef struct dictht {
    dictEntry **table;
    unsigned long size;
    unsigned long sizemask;
    unsigned long used;
} dictht;


typedef struct dict {
    dictType *type;
    void *privdata;
    dictht ht[2];
    long rehashidx; /* rehashing not in progress if rehashidx == -1 */
    unsigned long iterators; /* number of iterators currently running */
} dict;

 

type是hash表的内置函数，包括计算hash key，比较hash key等等。
ht[2]中的每个元素表示一张hash表。