redis源码解析（五）字典结构体

以你之姓@ 2022-04-22 00:08 138阅读 0赞

### 1. 前言 ###

字典结构是redis中的核心结构之一，主要由dictEntry, dictType, dictht和dict组成，详细源码和介绍如下。

### 2. 源码分析 ###

1. dictEntry  
   dictEntry是典型的哈希表项结构：由键值对组成，并且有链表指针next，用于同键下的遍历搜寻等操作。

/*字典（哈希表）的键值对，由key，v，和指针next组成，是拉链式哈希表的实际存储位置*/
    typedef struct dictEntry { 
        void *key;
        union { 
            void *val;
            uint64_t u64;
            int64_t s64;
            double d;
        } v;
        struct dictEntry *next;
    } dictEntry;

2. dictType  
  dictType是字典类型的指针函数集合，存储了哈希函数、赋值、遍历、析构操作。

/*函数指针结构体*/
    typedef struct dictType { 
        uint64_t (*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;

3. dictht  
  dictht是哈希表，管理了众多的表项dictEntry。

/* 哈希表，用于管理众多表项table[]，每一项均是一个链表 * This is our hash table structure. Every dictionary has two of this as we * implement incremental rehashing, for the old to the new table. */
    typedef struct dictht { 
        dictEntry **table;
        unsigned long size;
        unsigned long sizemask;
        unsigned long used;
    } dictht;

4. dict  
  dict是字典结构体，包含了字典函数指针结构体dictType，数据privdata，两个哈希表dictht以及标记和迭代。

/*封装的字典结构，包括dictType和两个哈希表*/
    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;

5. dictIterator  
  dictIterator是字典迭代器，包括字典dict，当前位置和下个dictEntry，标记位table和safe以及一个fingerprint：指纹数，类似于SHA1\_HASH，即哈希标记。

/* 字典迭代器 * If safe is set to 1 this is a safe iterator, that means, you can call * dictAdd, dictFind, and other functions against the dictionary even while * iterating. Otherwise it is a non safe iterator, and only dictNext() * should be called while iterating. */
    typedef struct dictIterator { 
        dict *d;
        long index;
        int table, safe;
        dictEntry *entry, *nextEntry;
        /* unsafe iterator fingerprint for misuse detection. */
        long long fingerprint;
    } dictIterator;