哈希表

static unsigned int hash(const char *s)
{
    unsigned int hash = 0;

    while(*s)
    {
        hash = 31 * hash + *s++;
    }

    return hash;
}

char *_ram_get(const char *name)
{
    unsigned int i;
    struct ram_tuple *t;
    char *value;

    if(name == NULL)
        return NULL;

    i = hash(name) % ARRAYSIZE(ram_hash);

    for(t=ram_hash[i]; t && strcmp(t->name, name); t=t->next);
    value = t ? t->value : NULL;

    return value;
}

void _ram_free(void)
{
    unsigned int i;
    struct ram_tuple *t, *next;

    for(i = 0; i < ARRAYSIZE(ram_hash); i++)
    {
        for(t= ram_hash[i]; t; t=next)
        {   
            next = t->next;
            free(t->name);
            free(t->value);
            free(t);
        }   
        ram_hash[i] = NULL;
    }   
}

int _ram_set(const char *name, const char *value)
{
    unsigned int i;
    struct ram_tuple *t, *u, **prev;

    i = hash(name) % ARRAYSIZE(ram_hash);

    for(prev = &ram_hash[i], t = *prev;        t && strcmp(t->name, name);         prev = &(t->next), t = *prev);

    if( (u = _ram_realloc(t, name, value)) == NULL)
    {
        return -12; /* -ENOMEM*/
    }

    if(t && t == u)
    {
        return 0;
    }

    u->next = ram_hash[i];
    ram_hash[i] = u;

    return 0;
}