C语言Hash Table的实现
|
调用函数hash_create()之后创建一个Hash Table
------------------------------------------------------ hashtable |---------------| | gethash() -| lh_strhash() | compare() -| equal_str() | hashsize -| size | count -| 0 | **hashlist -|------>|------------------| |---------------| --|struct hashentry *| NULL |------------------| | | |------------------| | | |------------------| | | |------------------| | | |------------------| |struct hashentry *| NULL |------------------| 调用函数hash_insert()时如果出现冲突，则形成hashentry队列 ------------------------------------------------------ hashtable |-------------| | gethash() | lh_strhash() | compare() | equal_str() | hashsize | size | count | 2 | **hashlist -|---->|------------------| |-------------| |struct hashentry *| NULL |------------------| | | |------------------| hashentry hashentry | |-->|---------| |---------| |------------------| | *key -| | *key -| | | | *data --| | *data --| |------------------| | *next --|-->| *next --| NULL | | |---------| |---------| |------------------| |struct hashentry *| NULL |------------------| hash.h -------------------------------------- #ifndef _LINUX_GHASH_H_ #define _LINUX_GHASH_H_ #include <string.h> #ifndef __USE_ISOC99 #define inline #endif #define create_hashtable(hsize) \ hash_create(lh_strhash, equal_str, hsize) unsigned int lh_strhash(void *src); int equal_str(void *k1, void *k2); struct hashentry; struct _hashtable; typedef struct _hashtable hashtable; hashtable *hash_create(unsigned int (*keyfunc)(void *), int (*comparefunc)(void *,void *), int size); void hash_free(hashtable *tab); void hash_insert(void *key, void *data, hashtable *tab); void hash_remove(void *key, hashtable *tab); void *hash_value(void *key, hashtable *tab); void hash_for_each_do(hashtable *tab, int (cb)(void *, void *)); int hash_count(hashtable *tab); #endif hash.c -------------------------------------- #include <string.h> #ifdef DMALLOC #include <dmalloc.h> #else #include <stdlib.h> #endif #include "hash.h" #ifndef __USE_ISOC99 #define inline #endif struct hashentry { void *key; void *data; struct hashentry *next; }; struct _hashtable { unsigned int (*gethash)(void *); int (*compare)(void *, void *); int hashsize; int count; struct hashentry **hashlist; }; #define hashindex(key, tab) ((tab->gethash)(key) % (tab->hashsize -1)) unsigned int lh_strhash(void *src) { int i, l; unsigned long ret = 0; unsigned short *s; char *str = (char *)src; if (str == NULL) return(0); l = (strlen(str) + 1) / 2; s = (unsigned short *)str; for (i = 0; i < l; i++) ret ^= s[i]<<(i&0x0f); return(ret); } int equal_str(void *k1, void *k2) { return (0 == strcmp((char *)k1, (char *)k2)); } inline struct hashentry *hashentry_new(void *key, void *data) { struct hashentry *new = malloc(sizeof(struct hashentry)); new->key = key; new->data = data; new->next = NULL; return new; } void hlist_append(struct hashentry **root, void *key, void *data) { struct hashentry *l, *pos; l = hashentry_new(key, data); if (*root == NULL) { *root = l; } else { for(pos = *root; pos->next != NULL; pos = pos->next); pos->next = l; } } int hlist_update(struct hashentry *root, void *key, void *data, int (*compare)(void *, void *)) { struct hashentry *pos; for(pos = root; pos != NULL; pos = pos->next ) { if ( compare(key, pos->key) ) { free(pos->data); pos->data = data; free(key); return 0; } } return -1; } inline struct hashentry *hashentry_free(struct hashentry *h) { struct hashentry *next = h->next; free(h->key); free(h->data); free(h); h = NULL; return (next); } int hlist_remove(struct hashentry **root, void *key, int (*compare)(void *,void *)) { struct hashentry *pos ,*prev; if (NULL == *root) return -1; if (compare((*root)->key, key)) { *root = hashentry_free(*root); return 0; } prev = *root; for (pos = prev->next; NULL != pos; pos = pos->next) { if (compare(pos->key, key)) { prev->next = hashentry_free(pos); return 0; } prev = pos; } return -1; } hashtable *hash_create(unsigned int (*keyfunc)(void *), int (*comparefunc)(void *, void *), int size) { int len = sizeof(struct hashentry *) * size; int i; hashtable *tab = malloc( sizeof(hashtable) ); memset(tab, 0, sizeof(hashtable)); tab->hashlist = malloc(len); if (tab->hashlist == NULL) { free(tab); return NULL; } memset(tab->hashlist, 0, len ); for (i = 0; i < size; i++) tab->hashlist[i] = NULL ; tab->compare = comparefunc; tab->gethash = keyfunc; tab->hashsize = size; tab->count = 0; return tab; } void hash_free(hashtable *tab) { int i; struct hashentry *pos; for (i = 0; i < tab->hashsize; i++) for (pos = tab->hashlist[i]; NULL != pos; pos = hashentry_free(pos)); free(tab->hashlist); free(tab); tab =NULL; } void hash_insert(void *key, void *data, hashtable *tab) { unsigned int index = hashindex(key, tab); struct hashentry *root = tab->hashlist[index]; if ( hlist_update(root, key, data, tab->compare ) != 0 ) { //(1) hlist_append(&(tab->hashlist[index]), key, data ); tab->count++; } } //(1) 查看Hash Table中是否存在键值为key的项，如果有则替换该键值所对应的value，否则调用hlist_append为key, data生成新的hashentry并插入相应的队列中。 void hash_remove(void *key, hashtable *tab) { unsigned int index = hashindex(key, tab); if (hlist_remove(&(tab->hashlist[index]), key, tab->compare) == 0) { tab->count--; } } void *hash_value(void *key, hashtable *tab) { struct hashentry *pos; unsigned int index = hashindex(key, tab); for (pos = tab->hashlist[index]; NULL != pos; pos = pos->next) { if (tab->compare(key, pos->key)) { return (pos->data); } } return NULL; } void hash_for_each_do(hashtable *tab, int(cb)(void *, void *)) { int i = 0; struct hashentry *pos; for (i = 0; i < tab->hashsize; i++) { for (pos = tab->hashlist[i]; NULL != pos; pos = pos->next ) { cb(pos->key, pos->data); } } } inline int hash_count(hashtable *tab) { return tab->count; } test.c -------------------------------------- #ifdef DMALLOC #include <dmalloc.h> #else #include <stdlib.h> #endif #include <stdio.h> #include <unistd.h> #include "hash.h" #define maxhash 10 int work(void *key, void *data) { printf("%s->%s\n",(char *)key, (char *)data); return 0; } int main(int argc, char *argv[]) { int i; char key[20]; char data[20]; memset(key, 0, 20); memset(data, 0, 20); hashtable *tab = create_hashtable(10); for (i = 0; i < maxhash; i++) { sprintf(key, "key%d", i); sprintf(data, "the line no: %d", i); hash_insert((void *)strdup(key), (void *)strdup(data), tab); } printf("remove key4\n"); hash_remove("key4", tab); printf("key -> value\n"); for (i = 0; i < maxhash; i++) { sprintf(key, "key%d", i); printf("%s->%s\n", key, (char *)hash_value(key, tab)); } printf("\n"); printf("%s->%s\n", "this is ", (char *)hash_value("this is ", tab)); printf("\n"); hash_for_each_do(tab, work); printf("size %d\n", hash_count(tab)); hash_free(tab); exit(0); } 编译运行 -------------------------------------- $ gcc test.c hash.c $ ./a.out remove key4 key -> value key0->the line no: 0 key1->the line no: 1 key2->the line no: 2 key3->the line no: 3 key4->(null) key5->the line no: 5 key6->the line no: 6 key7->the line no: 7 key8->the line no: 8 key9->the line no: 9 this is ->(null) key6->the line no: 6 key1->the line no: 1 key0->the line no: 0 key9->the line no: 9 key3->the line no: 3 key8->the line no: 8 key2->the line no: 2 key5->the line no: 5 key7->the line no: 7 size 9 |
