memcacheq的hashtable

阅读memcacheq的hashtable实现的时候，发现在创建一个存储链表的数组时，使用void **的方法建立数组，即数组里存放的是链表指针，这样在删除元素时，只需要用一个指针的指针（保存当前链表实体的地址），这样删除就方便多了

struct entry
{
    void *k, *v;
    unsigned int h;
    struct entry *next;
};

struct hashtable {
    unsigned int tablelength;
    struct entry **table;
    unsigned int entrycount;
    unsigned int loadlimit;
    unsigned int primeindex;
    unsigned int (*hashfn) (void *k);
    int (*eqfn) (void *k1, void *k2);
};

void * hashtable_remove(struct hashtable *h, void *k)
{
    /* TODO: consider compacting the table when the load factor drops enough,
     *       or provide a 'compact' method. */

    struct entry *e;
    struct entry **pE;
    void *v;
    unsigned int hashvalue, index;

    hashvalue = hash(h,k);
    index = indexFor(h->tablelength,hash(h,k));
    pE = &(h->table[index]);
    e = *pE;
    while (NULL != e)
    {
        /* Check hash value to short circuit heavier comparison */
        if ((hashvalue == e->h) && (h->eqfn(k, e->k)))
        {
            *pE = e->next;
            h->entrycount--;
            v = e->v;
            freekey(e->k);
            free(e);
            return v;
        }
        pE = &(e->next);
        e = e->next;
    }
    return NULL;
}