Split cache manager and file cache driver

Set up CacheManager as a Singleton.

qa-include/Q2A/Storage/CacheManager.php

@@ -25,32 +25,73 @@
  */
 class Q2A_Storage_CacheManager
 {
+	private static $instance;
 	private $enabled = false;
-	private $error = '';
-	private $dir;
+	private $cacheDriver;
 
 	/**
-	 * Creates a new CacheManager instance and checks it's set up properly.
+	 * Creates a new CacheManager instance and sets up the cache driver.
 	 */
-	public function __construct()
+	private function __construct()
 	{
 		$optEnabled = qa_opt('caching_enabled') == 1;
 
-		if (defined('QA_CACHE_DIRECTORY')) {
-			// expand symlinks so we compare true paths
-			$this->dir = realpath(QA_CACHE_DIRECTORY);
-			$baseDir = realpath(QA_BASE_DIR);
+		$config = array(
+			'dir' => defined('QA_CACHE_DIRECTORY') ? QA_CACHE_DIRECTORY : null,
+		);
 
-			if (!is_writable($this->dir)) {
-				$this->error = qa_lang_html_sub('admin/caching_dir_error', QA_CACHE_DIRECTORY);
-			} elseif (strpos($this->dir, $baseDir) === 0) {
-				$this->error = qa_lang_html_sub('admin/caching_dir_public', QA_CACHE_DIRECTORY);
+		$this->cacheDriver = new Q2A_Storage_FileCache($config);
+		$this->enabled = $optEnabled && $this->cacheDriver->isEnabled();
+	}
+
+	/**
+	 * Initializes the class and returns the singleton.
+	 * @return Q2A_Storage_CacheManager
+	 */
+	public static function getInstance()
+	{
+		if (!isset(self::$instance)) {
+			self::$instance = new self();
+		}
+
+		return self::$instance;
+	}
+
+	/**
+	 * Get the cached data for the supplied key.
+	 * @param string $key The unique cache identifier
+	 * @return mixed The cached data, or null otherwise.
+	 */
+	public function get($key)
+	{
+		if ($this->enabled) {
+			$encData = $this->cacheDriver->get($key);
+
+			// retrieve data, ignoring any notices
+			$data = @unserialize($encData);
+			if ($data !== false) {
+				return $data;
 			}
+		}
+
+		return null;
+	}
 
-			$this->enabled = empty($this->error) && $optEnabled;
-		} elseif ($optEnabled) {
-			$this->error = qa_lang_html('admin/caching_dir_missing');
+	/**
+	 * Serialize some data and store it in the cache.
+	 * @param string $key The unique cache identifier
+	 * @param mixed $data The data to cache - must be scalar values (i.e. string, int, array).
+	 * @param int $ttl Number of minutes for which to cache the data.
+	 * @return bool Whether the data was successfully cached.
+	 */
+	public function set($key, $data, $ttl)
+	{
+		if ($this->enabled) {
+			$encData = serialize($data);
+			return $this->cacheDriver->set($key, $encData, $ttl);
 		}
+
+		return false;
 	}
 
 	/**
@@ -68,6 +109,6 @@ class Q2A_Storage_CacheManager
 	 */
 	public function getError()
 	{
-		return $this->error;
+		return isset($this->cacheDriver) ? $this->cacheDriver->getError() : '';
 	}
 }

qa-include/Q2A/Storage/FileCache.php

+<?php
+/*
+	Question2Answer by Gideon Greenspan and contributors
+	http://www.question2answer.org/
+
+	File: qa-include/Q2A/Storage/FileCache.php
+	Description: File-based driver for caching system.
+
+
+	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 2
+	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.
+
+	More about this license: http://www.question2answer.org/license.php
+*/
+
+/**
+ * Caches data (typically from database queries) to the filesystem.
+ */
+class Q2A_Storage_FileCache
+{
+	private $enabled = false;
+	private $error;
+	private $cacheDir;
+
+	/**
+	 * Creates a new FileCache instance and checks we can write to the cache directory.
+	 * @param array $config Configuration data, including cache storage directory.
+	 */
+	public function __construct($config)
+	{
+		if (!isset($config['dir']))
+			return;
+
+		$this->cacheDir = realpath($config['dir']);
+
+		if (!is_writable($this->cacheDir)) {
+			$this->error = qa_lang_html_sub('admin/caching_dir_error', $this->cacheDir);
+		} elseif (strpos($this->cacheDir, realpath($_SERVER['DOCUMENT_ROOT'])) === 0 || strpos($this->cacheDir, realpath(QA_BASE_DIR)) === 0) {
+			// check the folder is outside the public root - checks against server root and Q2A root, in order to handle symbolic links
+			$this->error = qa_lang_html_sub('admin/caching_dir_public', $this->cacheDir);
+		}
+
+		$this->enabled = empty($this->error);
+	}
+
+	/**
+	 * Get the cached data for the supplied key.
+	 * @param string $key The unique cache identifier.
+	 * @return string The cached data, or null otherwise.
+	 */
+	public function get($key)
+	{
+		$file = $this->getFilename($key);
+
+		if (is_readable($file)) {
+			$lines = file($file, FILE_IGNORE_NEW_LINES);
+			$actualKey = array_shift($lines);
+
+			// double check this is the correct data
+			if ($key === $actualKey) {
+				$expiry = array_shift($lines);
+
+				if (is_numeric($expiry) && time() < $expiry) {
+					return implode("\n", $lines);
+				}
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * Store a string (usually serialized data) in the cache along with the key and expiry time.
+	 * @param string $key The unique cache identifier.
+	 * @param string $str The data to cache (usually a serialized string).
+	 * @param int $ttl Number of minutes for which to cache the data.
+	 * @return bool Whether the file was successfully cached.
+	 */
+	public function set($key, $str, $ttl)
+	{
+		$success = false;
+
+		if ($this->enabled) {
+			$file = $this->getFilename($key);
+			$dir = dirname($file);
+			$expiry = time() + ($ttl * 60);
+			$cache = $key . "\n" . $expiry . "\n" . $str;
+
+			if (is_dir($dir) || mkdir($dir, 0777, true)) {
+				$success = file_put_contents($file, $cache) !== false;
+			}
+		}
+
+		return $success;
+	}
+
+	/**
+	 * Whether caching is available.
+	 * @return bool
+	 */
+	public function isEnabled()
+	{
+		return $this->enabled;
+	}
+
+	/**
+	 * Get the last error.
+	 * @return string
+	 */
+	public function getError()
+	{
+		return $this->error;
+	}
+
+	/**
+	 * Generates filename for cache key, of the form `1/23/123abc`
+	 * @param string $key The unique cache key.
+	 * @return string
+	 */
+	private function getFilename($key)
+	{
+		$filename = sha1($key);
+		return $this->cacheDir . '/' . substr($filename, 0, 1) . '/' . substr($filename, 1, 2) . '/' . $filename;
+	}
+}

qa-include/pages/admin/admin-default.php

@@ -1781,12 +1781,9 @@
 			break;
 
 		case 'caching':
-			$cacheManager = new Q2A_Storage_CacheManager;
-			if (!$cacheManager->isEnabled()) {
-				$cacheError = $cacheManager->getError();
-				if ($cacheError)
-					$qa_content['error'] = $cacheError;
-			}
+			$cacheManager = Q2A_Storage_CacheManager::getInstance();
+			$qa_content['error'] = $cacheManager->getError();
+
 			break;
 	}