Redis基础数据结构篇之dict

Redis源码学习

本系列文章基于redis6.0.6版本，详见官网https://redis.io。

根据前人分享，结合源码，本系列将分为11个部分, 详见Redis源码学习，文章为记录个人理解，能力受限，如有偏颇之处请指正。

前言

Redis基础数据结构篇之dict: 

The implements in-memory hash tables with insert/del/replace/find/ get-random-element operations. Hash tables will auto-resize if needed tables of power of two in size are used, collisions are handled by  chaining.

---

一、图示

adlist结构定义如下:

typedef struct dictEntry {
    void *key;
    union {
        void *val;
        uint64_t u64;
        int64_t s64;
        double d;
    } v;
    struct dictEntry *next; //hash冲突解决方式: 单链表
} dictEntry;

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;

/* 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; // 动态分配的哈希桶 二级指针指向dicEntry*类型的entry
    PORT_ULONG size;
    PORT_ULONG sizemask; // 使用sizemask代替散列后的求余操作，a % b = a & (b-1)其中(b=2^n)
    PORT_ULONG used;
} dictht;

typedef struct dict {
    dictType *type;
    void *privdata;
    dictht ht[2];  //ht[0] 实际存储entry, ht[1] rehash时使用
    PORT_LONG rehashidx; /* rehashing not in progress if rehashidx == -1 */
    int iterators; /* number of iterators currently running */ //安全迭代器的计数， 在rehash前检测改标识，若有安全迭代器则不会进行rehash操作
} dict;

/* 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;
    PORT_LONG index;    //当前迭代器所处的位置
    int table, safe;    // table: 记录当前在ht[0]还是ht[1]； safe：标识当前是安全迭代器还是非安全迭代器
    dictEntry *entry, *nextEntry; // 记录下一个节点，安全迭代器的当前节点可能被调用者删除
    /* unsafe iterator fingerprint for misuse detection. */
    PORT_LONGLONG fingerprint; // 指纹：当前非安全迭代器开始迭代时对dict进行一个状态记录，使用Tomas Wang's 64 bit integer hash计算，
                               // 退出时同样计算一次，进行对比，若两次fingerprint相同则说明非安全迭代器在执行期间未做改变dict的操作
} dictIterator;

结构体图示如下：

二、源码理解

1.dict.h

/* Hash Tables Implementation.
 *
 * This file implements in-memory hash tables with insert/del/replace/find/
 * get-random-element operations. Hash tables will auto-resize if needed
 * tables of power of two in size are used, collisions are handled by
 * chaining. See the source code for more information... :)
 *
 * Copyright (c) 2006-2012, 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.
 */

#include <stdint.h>
#ifdef _WIN32
#include "Win32_Interop/win32_types.h"
#endif

#ifndef __DICT_H
#define __DICT_H

#define DICT_OK 0
#define DICT_ERR 1

/* Unused arguments generate annoying warnings... */
#define DICT_NOTUSED(V) ((void) V)

typedef struct dictEntry {
    void *key;
    union {
        void *val;
        uint64_t u64;
        int64_t s64;
        double d;
    } v;
    struct dictEntry *next; //hash冲突解决方式: 单链表
} dictEntry;

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;

/* 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; // 动态分配的哈希桶 二级指针指向dicEntry*类型的entry
    PORT_ULONG size;
    PORT_ULONG sizemask; // 使用sizemask代替散列后的求余操作，a % b = a & (b-1)其中(b=2^n)
    PORT_ULONG used;
} dictht;

typedef struct dict {
    dictType *type;
    void *privdata;
    dictht ht[2];  //ht[0] 实际存储entry, ht[1] rehash时使用
    PORT_LONG rehashidx; /* rehashing not in progress if rehashidx == -1 */
    int iterators; /* number of iterators currently running */ //安全迭代器的计数， 在rehash前检测改标识，若有安全迭代器则不会进行rehash操作
} dict;

/* 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;
    PORT_LONG index;    //当前迭代器所处的位置
    int table, safe;    // table: 记录当前在ht[0]还是ht[1]； safe：标识当前是安全迭代器还是非安全迭代器
    dictEntry *entry, *nextEntry; // 记录下一个节点，安全迭代器的当前节点可能被调用者删除
    /* unsafe iterator fingerprint for misuse detection. */
    PORT_LONGLONG fingerprint; // 指纹：当前非安全迭代器开始迭代时对dict进行一个状态记录，使用Tomas Wang's 64 bit integer hash计算，
                               // 退出时同样计算一次，进行对比，若两次fingerprint相同则说明非安全迭代器在执行期间未做改变dict的操作
} dictIterator;

typedef void(dictScanFunction)(void *privdata, const dictEntry *de); // dictScan遍历时使用，将hash桶de里的单个链表节点重新组织到privdata指向的单链中

/* This is the initial size of every hash table */
#define DICT_HT_INITIAL_SIZE     4

/* ------------------------------- Macros ------------------------------------*/
#define dictFreeVal(d, entry) \
    if ((d)->type->valDestructor) \
        (d)->type->valDestructor((d)->privdata, (entry)->v.val)

#define dictSetVal(d, entry, _val_) do { \
    if ((d)->type->valDup) \
        entry->v.val = (d)->type->valDup((d)->privdata, _val_); \
    else \
        entry->v.val = (_val_); \
} while(0)

#define dictSetSignedIntegerVal(entry, _val_) \
    do { entry->v.s64 = _val_; } while(0)

#define dictSetUnsignedIntegerVal(entry, _val_) \
    do { entry->v.u64 = _val_; } while(0)

#define dictSetDoubleVal(entry, _val_) \
    do { entry->v.d = _val_; } while(0)

#define dictFreeKey(d, entry) \
    if ((d)->type->keyDestructor) \
        (d)->type->keyDestructor((d)->privdata, (entry)->key)

#define dictSetKey(d, entry, _key_) do { \
    if ((d)->type->keyDup) \
        entry->key = (d)->type->keyDup((d)->privdata, _key_); \
    else \
        entry->key = (_key_); \
} while(0)

#define dictCompareKeys(d, key1, key2) \
    (((d)->type->keyCompare) ? \
        (d)->type->keyCompare((d)->privdata, key1, key2) : \
        (key1) == (key2))

#define dictHashKey(d, key) (d)->type->hashFunction(key)
#define dictGetKey(he) ((he)->key)
#define dictGetVal(he) ((he)->v.val)
#define dictGetSignedIntegerVal(he) ((he)->v.s64)
#define dictGetUnsignedIntegerVal(he) ((he)->v.u64)
#define dictGetDoubleVal(he) ((he)->v.d)
#define dictSlots(d) ((d)->ht[0].size+(d)->ht[1].size)
#define dictSize(d) ((d)->ht[0].used+(d)->ht[1].used)
#define dictIsRehashing(d) ((d)->rehashidx != -1)

/* API */
dict *dictCreate(dictType *type, void *privDataPtr);
int dictExpand(dict *d, PORT_ULONG size);
int dictAdd(dict *d, void *key, void *val);
dictEntry *dictAddRaw(dict *d, void *key);
int dictReplace(dict *d, void *key, void *val);
dictEntry *dictReplaceRaw(dict *d, void *key);
int dictDelete(dict *d, const void *key);
int dictDeleteNoFree(dict *d, const void *key);
void dictRelease(dict *d);
dictEntry * dictFind(dict *d, const void *key);
void *dictFetchValue(dict *d, const void *key);
int dictResize(dict *d);
dictIterator *dictGetIterator(dict *d);
dictIterator *dictGetSafeIterator(dict *d);
dictEntry *dictNext(dictIterator *iter);
void dictReleaseIterator(dictIterator *iter);
dictEntry *dictGetRandomKey(dict *d);
unsigned int dictGetSomeKeys(dict *d, dictEntry **des, unsigned int count);
void dictPrintStats(dict *d);
unsigned int dictGenHashFunction(const void *key, int len);
unsigned int dictGenCaseHashFunction(const unsigned char *buf, int len);
void dictEmpty(dict *d, void(callback)(void*));
void dictEnableResize(void);
void dictDisableResize(void);
int dictRehash(dict *d, int n);
int dictRehashMilliseconds(dict *d, int ms);
void dictSetHashFunctionSeed(unsigned int initval);
unsigned int dictGetHashFunctionSeed(void);
PORT_ULONG dictScan(dict *d, PORT_ULONG v, dictScanFunction *fn, void *privdata);

/* Hash table types */
extern dictType dictTypeHeapStringCopyKey;
extern dictType dictTypeHeapStrings;
extern dictType dictTypeHeapStringCopyKeyValue;

#endif /* __DICT_H */

 

2.dict.c

/* Hash Tables Implementation.
 *
 * This file implements in memory hash tables with insert/del/replace/find/
 * get-random-element operations. Hash tables will auto resize if needed
 * tables of power of two in size are used, collisions are handled by
 * chaining. See the source code for more information... :)
 *
 * Copyright (c) 2006-2012, 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