一个简单的HashMap C语言实现

http://blog.csdn.net/cheungmine/article/details/1894219

一个简单的HashMap C语言实现

cheungmine 

用C语言实现一个简单实用的hashmap，具有一定的实际意义。尤其我们不想使用STL里面的map<...>类的时候。我实现的这个hashmap，用来做key---value的映射，key必须是有效的字符串，value是调用者分配的任意类型的数据。这个hashmap适合在一些简单的场合下，消耗极少的资源。

首先定义头文件如下：

/* * hashmap.h *        Generic hash map: key(string)-value(any type). *        cheungmine  *      Sep. 22, 2007.  All rights reserved. */#ifndef HASHMAP_H_INCLUDED#define HASHMAP_H_INCLUDED#include "unistd.h"/* You should always use 1024 */#define     HASHMAP_SIZE    1024/* Opaque struct pointer to _hash_map_t */typedef struct    _hash_map_t*        hash_map;typedef void(*pfcb_hmap_value_free)(void* value);/* An example of free value function implemented by caller:void my_hmap_free_value(void* pv){    free(pv);}*//* Create before use. eg: * hash_map  hm; * hmap_create (&hm, HASHMAP_SIZE); * assert (hm);     // out of memory if hm==NULL  * void* mydata=malloc(n); * hmap_insert(hm, "shanghai", -1, mydata);   ... * hmap_destroy(hm, my_hmap_free_value); */extern void hmap_create(hash_map *hmap, int size);/* Destroy after use */extern void hmap_destroy(hash_map hmap, pfcb_hmap_value_free);/* Insert a key-value into hash map. value is a pointer to callee-allocated memory */extern void hmap_insert(hash_map hmap, const char* key, int key_len/* -1 for strlen to be called */, void* value);/* Search a hash map for value of given key string */extern void*  hmap_search(hash_map hmap, const char  *key);#endif  /* HASHMAP_H_INCLUDED */

实现文件如下：

/* * hashmap.c *        Generic hashmap implementation.  *      a map for pair of key-value. key must be a null-end string, value is any type of data. *        cheungmine  *      Sep. 22, 2007.  All rights reserved. */#include "hashmap.h"#include "list.h"typedef struct _hash_map_t{    size_t            size;    listnode_t**    key;    listnode_t**    value;}hash_map_t;/* Hash a string, return a hash key */static ulong  hash_string(const char  *s, int len){    ulong h = 0;    int   i = 0;    assert (s);    if (len < 0)        len = (s? (int)strlen(s): 0);    while(i++ < len) { h = 17*h + *s++; }    return h;    }static void _free_map_key(listnode_t* node){    listnode_t    *old;    while(node)    {                old = node;        node = node->next;                free(old->data);                free (old);    }}static void _free_map_value(listnode_t* node, pfcb_hmap_value_free pfunc){    listnode_t    *old;    while(node)    {                old = node;        node = node->next;                if (pfunc)            (*pfunc)(old->data);                free (old);    }}/*=============================================================================                            Public Functions=============================================================================*//* Create before use */void hmap_create(hash_map *hmap, int size){    (*hmap) = (hash_map_t*) malloc(sizeof(hash_map_t));    (*hmap)->size = size;    (*hmap)->key = (listnode_t**) calloc(size, sizeof(listnode_t*));    (*hmap)->value = (listnode_t**) calloc(size, sizeof(listnode_t*));}/* Destroy after use */extern void hmap_destroy(hash_map hmap, pfcb_hmap_value_free pfunc){    size_t i;    for(i=0; i<hmap->size; i++){        _free_map_key(hmap->key[i]);        _free_map_value(hmap->value[i], pfunc);    }        free(hmap->key);    free(hmap->value);    free(hmap);}/* Insert a key-value into hash map. value is a pointer to callee-allocated memory */void hmap_insert(hash_map hmap, const char* key, int key_len, void* value){    listnode_t    *node_key, *node_val;    ulong        h;    char        *s;    assert (key);    if (key_len<0) key_len = (int) strlen (key);    s = (char*) malloc (key_len+1);    assert(s);#pragma warning(push)    /* C4996 */#pragma warning( disable : 4996 )    strncpy (s, key, key_len);#pragma warning(pop)    /* C4996 */    s[key_len] = 0;        node_key = list_node_create ( (void*)s );    node_val = list_node_create ( value );    assert(node_key && node_val);    h = hash_string (s, key_len) % hmap->size;    node_key->next = hmap->key[h];    hmap->key[h] = node_key;        node_val->next = hmap->value[h];    hmap->value[h] = node_val;}/* Search a hash map for value of given key string */void*  hmap_search(hash_map hmap, const char *key){    ulong        h    = hash_string (key, -1) % hmap->size;    listnode_t  *pk = hmap->key[h];    listnode_t  *pv = hmap->value[h];    while (pk)    {        if (strcmp(key, pk->str) == 0)            return pv->data;                pk = pk->next;        pv = pv->next;    }    return NULL;}