/*
Copyright (C) 2017 Paweł Redman

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 3
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
*/

#include "shared.h"

#define HASH_MAX 4095

static size_t cache_hash(uint32_t ipv4)
{
	// FIXME: Use an academically acclaimed hashing algorithm.
	return (((ipv4 >> 16) ^ ipv4) * 3137) & HASH_MAX;
}

static cache_entry_t *cache_ht[HASH_MAX];
static pthread_mutex_t cache_mutex = PTHREAD_MUTEX_INITIALIZER;

// Returns an entry with its mutex locked.
cache_entry_t *cache_find(uint32_t ipv4)
{
	cache_entry_t *entry;
	size_t hash;

	hash = cache_hash(ipv4);

	pthread_mutex_lock(&cache_mutex);
	eli_for (entry, cache_ht[hash], ht_list)
		if (entry->ipv4 == ipv4)
			break;

	if (!entry) {
		entry = calloc(1, sizeof(cache_entry_t));
		entry->ipv4 = ipv4;
		pthread_mutex_init(&entry->mutex, NULL);
		eli_append(cache_ht + hash, entry, ht_list);
	}

	pthread_mutex_lock(&entry->mutex);
	pthread_mutex_unlock(&cache_mutex);

	return entry;
}

void cache_destroy(void)
{
	size_t i;
	cache_entry_t *entry, *next;

	for (i = 0; i < HASH_MAX; i++) {
		for (entry = cache_ht[i]; entry; entry = next) {
			next = entry->ht_list.next;

			free(entry->revdns);
			free(entry->whois);
			free(entry);
		}

		cache_ht[i] = NULL;
	}
}