C语言标准库缺失了一种常用且重要的数据结构，这就是哈希表。没有动态的vector，我们可以使用数组来凑合用，但没有哈希表，确实很难办，期待“C1x”标准能够带来更加丰富标准库。APR的Hash Table模块提供了很好用的哈希表的实现，编程示例如下：

#include <stdio.h>
#include <apr.h>
#include <apr_pools.h>
#include <apr_errno.h>
#include <apr_strings.h>
#include <apr_time.h>
#include <apr_hash.h>

void apr_err(const char *s, apr_status_t rv)
{
    char buf[120];
    fprintf(stderr, "%s: %s (%d)\n", s, 
            apr_strerror(rv, buf, sizeof buf), rv);
}

int main(int argc,char **argv) {
    apr_initialize();
    apr_pool_t *pool;
    apr_pool_create(&pool,NULL);
    apr_status_t st;

    apr_hash_t *ht;
    ht=apr_hash_make(pool);
    char *key;
    char *value;

    key="laomeng";
    value="laomeng188@163.com";
    apr_hash_set(ht,key,strlen(key),value);
    key="laozhang";
    value="laozhang250@163.com";
    apr_hash_set(ht,key,strlen(key),value);
    
    char *getvalue=apr_hash_get(ht,key,strlen(key));
    printf("getvalue : %s\n",getvalue);
    printf("total items: %u\n",apr_hash_count(ht));

    apr_hash_index_t *idx;
    char *k=NULL;
    char *v=NULL;
    for(idx=apr_hash_first(pool,ht);idx != NULL;idx=apr_hash_next(idx)) {
        apr_hash_this(idx,(const void **)&k,(apr_ssize_t *)NULL,(void **)&v);
        printf("%s => %s\n",k,v);
    }

    apr_hash_set(ht,key,strlen(key),NULL);
    printf("total items: %u\n",apr_hash_count(ht));

    apr_hash_clear(ht);
    printf("total items: %u\n",apr_hash_count(ht));
    getvalue=apr_hash_get(ht,key,strlen(key));
    printf("getvalue : %s\n",getvalue);


    apr_pool_destroy(pool);
    apr_terminate();
    return 0;
}

参考资料：

http://apr.apache.org/docs/apr/1.3/group__apr__hash.html