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 程式師世界 >> 編程語言 >> C語言 >> C++ >> 關於C++ >> c說話完成的hashtable分享

c說話完成的hashtable分享

編輯:關於C++

c說話完成的hashtable分享。本站提示廣大學習愛好者:(c說話完成的hashtable分享)文章只能為提供參考,不一定能成為您想要的結果。以下是c說話完成的hashtable分享正文


頭文件 hashtable.h


typedef struct _Bucket
{
    char *key;
    void *value;
    struct _Bucket *next;
} Bucket;

typedef struct _HashTable
{
    int size;
    int total;
    struct _Bucket *buckets;
} HashTable;

int hash_init(HashTable **ht);
int hash_find(HashTable *ht, char *key, void **result);
int hash_insert(HashTable *ht, char *key, void *value);
int hash_remove(HashTable *ht, char *key);
int hash_loop(HashTable *ht, void **result);
//int hash_index(HashTable *ht, char *key);
static unsigned int ELFHash(char *str, unsigned int length);

hashtable.c


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "hashtable.h"
#include "mempool.h"
#include "log.h"

#define SUCCESS 1
#define FAILED 0
#define HASH_LEN 5

int hash_init(HashTable **ht) {
    (*ht) = (HashTable *)malloc(sizeof(HashTable));
    if (NULL == ht) {
        write_log("HashTable init error");
        exit(1);
    }
    (*ht)->size = 0;
    (*ht)->total = HASH_LEN;
    Bucket *bucket = (Bucket *)malloc(sizeof(Bucket) * HASH_LEN);
    memset(bucket, 0, sizeof(sizeof(Bucket) * HASH_LEN));
    (*ht)->buckets = bucket;
    return SUCCESS;
}

int hash_insert(HashTable *ht, char *key, void *value) {
    if (ht->size >= ht->total) {
        ht->buckets = (Bucket *)realloc(ht->buckets, sizeof(Bucket) * (ht->size + HASH_LEN));
        ht->total = ht->size + HASH_LEN;
    }
    int index = hash_index(ht, key);
    Bucket *bucket = &ht->buckets[index];
    int _tmpindex;
    char _tmpindexstr[20];
    while (NULL != bucket->value) {

        while (NULL != bucket->next) {
            if (strcmp(key, bucket->key) == 0) {
                memset(bucket->value, 0, sizeof(bucket->value));
                memcpy(bucket->value, value, sizeof(value));
                return SUCCESS;
            }
            bucket = bucket->next;
        }

        do {
            _tmpindex = abs(rand() - index);
            sprintf(_tmpindexstr, "%d", _tmpindex);
            _tmpindex = hash_index(ht, _tmpindexstr);
        } while (_tmpindex == index || ht->buckets[_tmpindex].value != NULL);

        index = _tmpindex;
        bucket->next = &ht->buckets[index];
        bucket = bucket->next;
    }

    bucket->key = (char *)malloc(sizeof(key));
    bucket->value = (void *)malloc(sizeof(value));
    memcpy(bucket->key, key, sizeof(key));
    memcpy(bucket->value, value, sizeof(value));
    bucket->next = NULL;
    ht->size ++;

    return SUCCESS;
}

int hash_find(HashTable *ht, char *key, void **result) {
    int index = hash_index(ht, key);
    Bucket *bucket = &ht->buckets[index];
    if (NULL == bucket->value) {
        return FAILED;
    }

    while (strcmp(key, bucket->key)) {
        if (NULL != bucket->next) {
            bucket = bucket->next;
        } else {
            break;
        }
    }
    if (NULL == bucket->value || strcmp(key, bucket->key)) {
        return FAILED;
    }

    *result = bucket->value;
    return SUCCESS;

}

int hash_delete(HashTable *ht, char *key) {
    int index = hash_index(ht, key);
    Bucket *bucket = &ht->buckets[index];
    if (NULL == bucket->value) {
        return FAILED;
    }

    while (strcmp(key, bucket->key)) {
        if (NULL != bucket->next) {
            bucket = bucket->next;
        } else {
            break;
        }
    }

    if (NULL == bucket->value || strcmp(key, bucket->key)) {
        return FAILED;
    }

    memset(bucket, 0, sizeof(Bucket));
    ht->size --;
    return SUCCESS;
}

void hash_status(HashTable *ht) {
    printf("Total Size:\t\t%d\n", ht->total);
    printf("Current Size:\t\t%d\n", ht->size);
}

int hash_index(HashTable *ht, char *key) {
    return ELFHash(key, ht->total);
}

// ELF Hash Function
static unsigned int ELFHash(char *str, unsigned int length){
    unsigned int hash = 0;
    unsigned int x = 0;

    while (*str)
    {
        hash = (hash << 4) + (*str++);//hash左移4位,把以後字符ASCII存入hash低四位。
        if ((x = hash & 0xF0000000L) != 0)
        {
            //假如最高的四位不為0,則解釋字符過剩7個,如今正在存第8個字符,假如不處置,再加下一個字符時,第一個字符會被移出,是以要有以下處置。
            //該處置,假如關於字符串(a-z 或許A-Z)就會僅僅影響5-8位,不然會影響5-31位,由於C說話應用的算數移位
            //由於1-4位方才存儲了新參加到字符,所以不克不及>>28
            hash ^= (x >> 24);
            //下面這行代碼其實不會對X有影響,自己X和hash的高4位雷同,上面這行代碼&~即對28-31(高4位)位清零。
            hash &= ~x;
        }
    }
    //前往一個符號位為0的數,即拋棄最高位,以避免函數外發生影響。(我們可以斟酌,假如只要字符,符號位弗成能為負)
    return (hash & 0x7FFFFFFF) % length;
}

個中key的映照應用的是 ELFHash 算法

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