rcube_cache_shared.php
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rcube_cache_shared.php
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	<?php

	/**
	+-----------------------------------------------------------------------+
	\| This file is part of the Roundcube Webmail client \|
	\| Copyright (C) 2011-2013, The Roundcube Dev Team \|
	\| Copyright (C) 2011-2013, Kolab Systems AG \|
	\| \|
	\| Licensed under the GNU General Public License version 3 or \|
	\| any later version with exceptions for skins & plugins. \|
	\| See the README file for a full license statement. \|
	\| \|
	\| PURPOSE: \|
	\| Shared (cross-user) caching engine \|
	+-----------------------------------------------------------------------+
	\| Author: Thomas Bruederli <roundcube@gmail.com> \|
	\| Author: Aleksander Machniak <alec@alec.pl> \|
	+-----------------------------------------------------------------------+
	*/

	/**
	* Interface class for accessing Roundcube shared cache
	*
	* @package Framework
	* @subpackage Cache
	* @author Thomas Bruederli <roundcube@gmail.com>
	* @author Aleksander Machniak <alec@alec.pl>
	*/
	class rcube_cache_shared
	{
	/**
	* Instance of database handler
	*
	* @var rcube_db\|Memcache\|bool
	*/
	private $db;
	private $type;
	private $prefix;
	private $ttl;
	private $packed;
	private $index;
	private $table;
	private $debug;
	private $index_changed = false;
	private $cache = array();
	private $cache_changes = array();
	private $cache_sums = array();
	private $max_packet = -1;


	/**
	* Object constructor.
	*
	* @param string $type Engine type ('db' or 'memcache' or 'apc')
	* @param string $prefix Key name prefix
	* @param string $ttl Expiration time of memcache/apc items
	* @param bool $packed Enables/disabled data serialization.
	* It's possible to disable data serialization if you're sure
	* stored data will be always a safe string
	*/
	function __construct($type, $prefix='', $ttl=0, $packed=true)
	{
	$rcube = rcube::get_instance();
	$type = strtolower($type);

	if ($type == 'memcache') {
	$this->type = 'memcache';
	$this->db = $rcube->get_memcache();
	$this->debug = $rcube->config->get('memcache_debug');
	}
	else if ($type == 'apc') {
	$this->type = 'apc';
	$this->db = function_exists('apc_exists'); // APC 3.1.4 required
	$this->debug = $rcube->config->get('apc_debug');
	}
	else {
	$this->type = 'db';
	$this->db = $rcube->get_dbh();
	$this->table = $this->db->table_name('cache_shared', true);
	}

	// convert ttl string to seconds
	$ttl = get_offset_sec($ttl);
	if ($ttl > 2592000) $ttl = 2592000;

	$this->ttl = $ttl;
	$this->packed = $packed;
	$this->prefix = $prefix;
	}

	/**
	* Returns cached value.
	*
	* @param string $key Cache key name
	*
	* @return mixed Cached value
	*/
	function get($key)
	{
	if (!array_key_exists($key, $this->cache)) {
	return $this->read_record($key);
	}

	return $this->cache[$key];
	}

	/**
	* Sets (add/update) value in cache.
	*
	* @param string $key Cache key name
	* @param mixed $data Cache data
	*/
	function set($key, $data)
	{
	$this->cache[$key] = $data;
	$this->cache_changes[$key] = true;
	}

	/**
	* Returns cached value without storing it in internal memory.
	*
	* @param string $key Cache key name
	*
	* @return mixed Cached value
	*/
	function read($key)
	{
	if (array_key_exists($key, $this->cache)) {
	return $this->cache[$key];
	}

	return $this->read_record($key, true);
	}

	/**
	* Sets (add/update) value in cache and immediately saves
	* it in the backend, no internal memory will be used.
	*
	* @param string $key Cache key name
	* @param mixed $data Cache data
	*
	* @param boolean True on success, False on failure
	*/
	function write($key, $data)
	{
	return $this->write_record($key, $this->serialize($data));
	}

	/**
	* Clears the cache.
	*
	* @param string $key Cache key name or pattern
	* @param boolean $prefix_mode Enable it to clear all keys starting
	* with prefix specified in $key
	*/
	function remove($key=null, $prefix_mode=false)
	{
	// Remove all keys
	if ($key === null) {
	$this->cache = array();
	$this->cache_changes = array();
	$this->cache_sums = array();
	}
	// Remove keys by name prefix
	else if ($prefix_mode) {
	foreach (array_keys($this->cache) as $k) {
	if (strpos($k, $key) === 0) {
	$this->cache[$k] = null;
	$this->cache_changes[$k] = false;
	unset($this->cache_sums[$k]);
	}
	}
	}
	// Remove one key by name
	else {
	$this->cache[$key] = null;
	$this->cache_changes[$key] = false;
	unset($this->cache_sums[$key]);
	}

	// Remove record(s) from the backend
	$this->remove_record($key, $prefix_mode);
	}

	/**
	* Remove cache records older than ttl
	*/
	function expunge()
	{
	if ($this->type == 'db' && $this->db && $this->ttl) {
	$this->db->query(
	"DELETE FROM {$this->table}"
	. " WHERE `cache_key` LIKE ?"
	. " AND `expires` < " . $this->db->now(),
	$this->prefix . '.%');
	}
	}

	/**
	* Remove expired records of all caches
	*/
	static function gc()
	{
	$rcube = rcube::get_instance();
	$db = $rcube->get_dbh();

	$db->query("DELETE FROM " . $db->table_name('cache_shared', true) . " WHERE `expires` < " . $db->now());
	}

	/**
	* Writes the cache back to the DB.
	*/
	function close()
	{
	foreach ($this->cache as $key => $data) {
	// The key has been used
	if ($this->cache_changes[$key]) {
	// Make sure we're not going to write unchanged data
	// by comparing current md5 sum with the sum calculated on DB read
	$data = $this->serialize($data);

	if (!$this->cache_sums[$key] \|\| $this->cache_sums[$key] != md5($data)) {
	$this->write_record($key, $data);
	}
	}
	}

	if ($this->index_changed) {
	$this->write_index();
	}

	// reset internal cache index, thanks to this we can force index reload
	$this->index = null;
	$this->index_changed = false;
	$this->cache = array();
	$this->cache_sums = array();
	$this->cache_changes = array();
	}

	/**
	* Reads cache entry.
	*
	* @param string $key Cache key name
	* @param boolean $nostore Enable to skip in-memory store
	*
	* @return mixed Cached value
	*/
	private function read_record($key, $nostore=false)
	{
	if (!$this->db) {
	return null;
	}

	if ($this->type != 'db') {
	$this->load_index();

	// Consistency check (#1490390)
	if (!in_array($key, $this->index)) {
	// we always check if the key exist in the index
	// to have data in consistent state. Keeping the index consistent
	// is needed for keys delete operation when we delete all keys or by prefix.
	}
	else {
	$ckey = $this->ckey($key);

	if ($this->type == 'memcache') {
	$data = $this->db->get($ckey);
	}
	else if ($this->type == 'apc') {
	$data = apc_fetch($ckey);
	}

	if ($this->debug) {
	$this->debug('get', $ckey, $data);
	}
	}

	if ($data !== false) {
	$md5sum = md5($data);
	$data = $this->unserialize($data);

	if ($nostore) {
	return $data;
	}

	$this->cache_sums[$key] = $md5sum;
	$this->cache[$key] = $data;
	}
	else {
	$this->cache[$key] = null;
	}
	}
	else {
	$sql_result = $this->db->query(
	"SELECT `data`, `cache_key` FROM {$this->table}"
	. " WHERE `cache_key` = ?",
	$this->prefix . '.' . $key);

	if ($sql_arr = $this->db->fetch_assoc($sql_result)) {
	if (strlen($sql_arr['data']) > 0) {
	$md5sum = md5($sql_arr['data']);
	$data = $this->unserialize($sql_arr['data']);
	}

	$this->db->reset();

	if ($nostore) {
	return $data;
	}

	$this->cache[$key] = $data;
	$this->cache_sums[$key] = $md5sum;
	}
	else {
	$this->cache[$key] = null;
	}
	}

	return $this->cache[$key];
	}

	/**
	* Writes single cache record into DB.
	*
	* @param string $key Cache key name
	* @param mixed $data Serialized cache data
	*
	* @param boolean True on success, False on failure
	*/
	private function write_record($key, $data)
	{
	if (!$this->db) {
	return false;
	}

	// don't attempt to write too big data sets
	if (strlen($data) > $this->max_packet_size()) {
	trigger_error("rcube_cache: max_packet_size ($this->max_packet) exceeded for key $key. Tried to write " . strlen($data) . " bytes", E_USER_WARNING);
	return false;
	}

	if ($this->type == 'memcache' \|\| $this->type == 'apc') {
	$result = $this->add_record($this->ckey($key), $data);

	// make sure index will be updated
	if ($result) {
	if (!array_key_exists($key, $this->cache_sums)) {
	$this->cache_sums[$key] = true;
	}

	$this->load_index();

	if (!$this->index_changed && !in_array($key, $this->index)) {
	$this->index_changed = true;
	}
	}

	return $result;
	}

	$db_key = $this->prefix . '.' . $key;

	// Remove NULL rows (here we don't need to check if the record exist)
	if ($data == 'N;') {
	$result = $this->db->query("DELETE FROM {$this->table} WHERE `cache_key` = ?", $db_key);

	return !$this->db->is_error($result);
	}

	$key_exists = array_key_exists($key, $this->cache_sums);
	$expires = $this->ttl ? $this->db->now($this->ttl) : 'NULL';

	if (!$key_exists) {
	// Try INSERT temporarily ignoring "duplicate key" errors
	$this->db->set_option('ignore_key_errors', true);

	$result = $this->db->query(
	"INSERT INTO {$this->table} (`expires`, `cache_key`, `data`)"
	. " VALUES ($expires, ?, ?)",
	$db_key, $data);

	$this->db->set_option('ignore_key_errors', false);
	}

	// otherwise try UPDATE
	if (!isset($result) \|\| !($count = $this->db->affected_rows($result))) {
	$result = $this->db->query(
	"UPDATE {$this->table} SET `expires` = $expires, `data` = ?"
	. " WHERE `cache_key` = ?",
	$data, $db_key);

	$count = $this->db->affected_rows($result);
	}

	return $count > 0;
	}

	/**
	* Deletes the cache record(s).
	*
	* @param string $key Cache key name or pattern
	* @param boolean $prefix_mode Enable it to clear all keys starting
	* with prefix specified in $key
	*/
	private function remove_record($key=null, $prefix_mode=false)
	{
	if (!$this->db) {
	return;
	}

	if ($this->type != 'db') {
	$this->load_index();

	// Remove all keys
	if ($key === null) {
	foreach ($this->index as $key) {
	$this->delete_record($this->ckey($key));
	}

	$this->index = array();
	}
	// Remove keys by name prefix
	else if ($prefix_mode) {
	foreach ($this->index as $idx => $k) {
	if (strpos($k, $key) === 0) {
	$this->delete_record($this->ckey($k));
	unset($this->index[$idx]);
	}
	}
	}
	// Remove one key by name
	else {
	$this->delete_record($this->ckey($key));
	if (($idx = array_search($key, $this->index)) !== false) {
	unset($this->index[$idx]);
	}
	}

	$this->index_changed = true;

	return;
	}

	// Remove all keys (in specified cache)
	if ($key === null) {
	$where = " WHERE `cache_key` LIKE " . $this->db->quote($this->prefix.'.%');
	}
	// Remove keys by name prefix
	else if ($prefix_mode) {
	$where = " WHERE `cache_key` LIKE " . $this->db->quote($this->prefix.'.'.$key.'%');
	}
	// Remove one key by name
	else {
	$where = " WHERE `cache_key` = " . $this->db->quote($this->prefix.'.'.$key);
	}

	$this->db->query("DELETE FROM " . $this->table . $where);
	}

	/**
	* Adds entry into memcache/apc DB.
	*
	* @param string $key Cache internal key name
	* @param mixed $data Serialized cache data
	*
	* @param boolean True on success, False on failure
	*/
	private function add_record($key, $data)
	{
	if ($this->type == 'memcache') {
	$result = $this->db->replace($key, $data, MEMCACHE_COMPRESSED, $this->ttl);

	if (!$result) {
	$result = $this->db->set($key, $data, MEMCACHE_COMPRESSED, $this->ttl);
	}
	}
	else if ($this->type == 'apc') {
	if (apc_exists($key)) {
	apc_delete($key);
	}

	$result = apc_store($key, $data, $this->ttl);
	}

	if ($this->debug) {
	$this->debug('set', $key, $data, $result);
	}

	return $result;
	}

	/**
	* Deletes entry from memcache/apc DB.
	*
	* @param string $key Cache internal key name
	*
	* @param boolean True on success, False on failure
	*/
	private function delete_record($key)
	{
	if ($this->type == 'memcache') {
	// #1488592: use 2nd argument
	$result = $this->db->delete($key, 0);
	}
	else {
	$result = apc_delete($key);
	}

	if ($this->debug) {
	$this->debug('delete', $key, null, $result);
	}

	return $result;
	}

	/**
	* Writes the index entry into memcache/apc DB.
	*/
	private function write_index()
	{
	if (!$this->db \|\| $this->type == 'db') {
	return;
	}

	$this->load_index();

	// Make sure index contains new keys
	foreach ($this->cache as $key => $value) {
	if ($value !== null && !in_array($key, $this->index)) {
	$this->index[] = $key;
	}
	}

	// new keys added using self::write()
	foreach ($this->cache_sums as $key => $value) {
	if ($value === true && !in_array($key, $this->index)) {
	$this->index[] = $key;
	}
	}

	$data = serialize($this->index);
	$this->add_record($this->ikey(), $data);
	}

	/**
	* Gets the index entry from memcache/apc DB.
	*/
	private function load_index()
	{
	if (!$this->db \|\| $this->type == 'db') {
	return;
	}

	if ($this->index !== null) {
	return;
	}

	$index_key = $this->ikey();

	if ($this->type == 'memcache') {
	$data = $this->db->get($index_key);
	}
	else if ($this->type == 'apc') {
	$data = apc_fetch($index_key);
	}

	if ($this->debug) {
	$this->debug('get', $index_key, $data);
	}

	$this->index = $data ? unserialize($data) : array();
	}

	/**
	* Creates cache key name (for memcache and apc)
	*
	* @param string $key Cache key name
	*
	* @return string Cache key
	*/
	private function ckey($key)
	{
	return $this->prefix . ':' . $key;
	}

	/**
	* Creates index cache key name (for memcache and apc)
	*
	* @return string Cache key
	*/
	private function ikey()
	{
	// This way each cache will have its own index
	return $this->prefix . 'INDEX';
	}

	/**
	* Serializes data for storing
	*/
	private function serialize($data)
	{
	if ($this->type == 'db') {
	return $this->db->encode($data, $this->packed);
	}

	return $this->packed ? serialize($data) : $data;
	}

	/**
	* Unserializes serialized data
	*/
	private function unserialize($data)
	{
	if ($this->type == 'db') {
	return $this->db->decode($data, $this->packed);
	}

	return $this->packed ? @unserialize($data) : $data;
	}

	/**
	* Determine the maximum size for cache data to be written
	*/
	private function max_packet_size()
	{
	if ($this->max_packet < 0) {
	$this->max_packet = 2097152; // default/max is 2 MB

	if ($this->type == 'db') {
	if ($value = $this->db->get_variable('max_allowed_packet', $this->max_packet)) {
	$this->max_packet = $value;
	}
	$this->max_packet -= 2000;
	}
	else {
	$max_packet = rcube::get_instance()->config->get($this->type . '_max_allowed_packet');
	$this->max_packet = parse_bytes($max_packet) ?: $this->max_packet;
	}
	}

	return $this->max_packet;
	}

	/**
	* Write memcache/apc debug info to the log
	*/
	private function debug($type, $key, $data = null, $result = null)
	{
	$line = strtoupper($type) . ' ' . $key;

	if ($data !== null) {
	$line .= ' ' . ($this->packed ? $data : serialize($data));
	}

	rcube::debug($this->type, $line, $result);
	}
	}

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