Added a simple cache implementation

HandBrakeCluster/Cache.class.php

@@ -0,0 +1,60 @@
+<?php
+
+class HandBrakeCluster_Cache {
+    
+    protected $config;
+    protected $cache_dir;
+    
+    public function __construct(HandBrakeCluster_Config $config) {
+        $this->config = $config;
+        $this->cache_dir = $config->get('cache.base_dir');
+        
+        if (is_dir($cache_dir)) {
+            if ( ! is_writeable($cache_dir)) {
+                throw new HandBrakeCluster_Exception_InvalidCacheDir();
+            }
+        } else {
+            if ( ! HandBrakeCluster_Main::mkdir_recursive($this->cache_dir)) {
+                throw new HandBrakeCluster_Exception_InvalidCacheDir();
+            }
+        }
+    }
+    
+    protected function cacheFilename($source_filename) {
+        return $this->cache_dir . sha1($source_filename);
+    }
+    
+    public function exists($source_filename, $ttl = 3600) {
+        $cache_filename = $this->cacheFilename($source_filename);
+        
+        // Check to see if the file is cached
+        if (!file_exists($cache_filename)) {
+            return false;
+        }
+        
+        // Check to see if the cache has expired
+        if (filemtime($cache_filename) + $ttl < time()) {
+            return false;
+        }
+        
+        return true;
+    }
+    
+    public function store($source_filename, $content) {
+        $cache_filename = $this->cacheFilename($source_filename);
+        return file_put_contents($cache_filename, $content);
+    }
+    
+    public function fetch($source_filename, $ttl = 3600) {
+        $cache_filename = $this->cacheFilename($source_filename);
+        
+        if (!$this->exists($source_filename)) {
+            throw new HandBrakeCluster_Exception_CacheObjectNotFound($source_filename);
+        }
+        
+        return file_get_contents($cache_filename);
+    }
+    
+};
+
+?>