Here's a very simple and naive one
- Fixed bucket size
- No delete operation
- inserts replaces the key and value, and can optionally free them
:
#include <string.h>
#include <stdlib.h>
#define NR_BUCKETS 1024
struct StrHashNode {
char *key;
void *value;
struct StrHashNode *next;
};
struct StrHashTable {
struct StrHashNode *buckets[NR_BUCKETS];
void (*free_key)(char *);
void (*free_value)(void*);
unsigned int (*hash)(const char *key);
int (*cmp)(const char *first,const char *second);
};
void *get(struct StrHashTable *table,const char *key)
{
unsigned int bucket = table->hash(key)%NR_BUCKETS;
struct StrHashNode *node;
node = table->buckets[bucket];
while(node) {
if(table->cmp(key,node->key) == 0)
return node->value;
node = node->next;
}
return NULL;
}
int insert(struct StrHashTable *table,char *key,void *value)
{
unsigned int bucket = table->hash(key)%NR_BUCKETS;
struct StrHashNode **tmp;
struct StrHashNode *node ;
tmp = &table->buckets[bucket];
while(*tmp) {
if(table->cmp(key,(*tmp)->key) == 0)
break;
tmp = &(*tmp)->next;
}
if(*tmp) {
if(table->free_key != NULL)
table->free_key((*tmp)->key);
if(table->free_value != NULL)
table->free_value((*tmp)->value);
node = *tmp;
} else {
node = malloc(sizeof *node);
if(node == NULL)
return -1;
node->next = NULL;
*tmp = node;
}
node->key = key;
node->value = value;
return 0;
}
unsigned int foo_strhash(const char *str)
{
unsigned int hash = 0;
for(; *str; str++)
hash = 31*hash + *str;
return hash;
}
#include <stdio.h>
int main(int argc,char *argv[])
{
struct StrHashTable tbl = {{0},NULL,NULL,foo_strhash,strcmp};
insert(&tbl,"Test","TestValue");
insert(&tbl,"Test2","TestValue2");
puts(get(&tbl,"Test"));
insert(&tbl,"Test","TestValueReplaced");
puts(get(&tbl,"Test"));
return 0;
}
