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lib/pkp/classes/cache/GenericCache.php

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+<?php
+
+/**
+ * @file classes/cache/GenericCache.php
+ *
+ * Copyright (c) 2014-2021 Simon Fraser University
+ * Copyright (c) 2000-2021 John Willinsky
+ * Distributed under the GNU GPL v3. For full terms see the file docs/COPYING.
+ *
+ * @class generic_cache_miss
+ *
+ * @ingroup cache
+ *
+ * @brief Provides implementation-independent caching. Although this class is intended
+ * to be overridden with a more specific implementation, it can be used as the
+ * null cache.
+ */
+
+namespace PKP\cache;
+
+// Pseudotype to represent a cache miss
+class generic_cache_miss
+{
+}
+
+class GenericCache
+{
+    /**
+     * The unique string identifying the context of this cache.
+     * Must be suitable for a filename.
+     */
+    public $context;
+
+    /**
+     * The ID of this particular cache within the context
+     */
+    public $cacheId;
+
+    public $cacheMiss;
+
+    /**
+     * The getter fallback callback (for a cache miss)
+     * This function is called with two parameters:
+     *  1. The cache object that is suffering a miss
+     *  2. The id of the value to fetch
+     * The function is responsible for loading data into the
+     * cache, using setEntireCache or setCache.
+     */
+    public $fallback;
+
+    /**
+     * Instantiate a cache.
+     */
+    public function __construct($context, $cacheId, $fallback)
+    {
+        $this->context = $context;
+        $this->cacheId = $cacheId;
+        $this->fallback = $fallback;
+        $this->cacheMiss = new generic_cache_miss();
+    }
+
+    /**
+     * Get an object from cache, using the fallback if necessary.
+     */
+    public function get($id)
+    {
+        $result = $this->getCache($id);
+        if (is_object($result) && $result instanceof generic_cache_miss) {
+            $result = call_user_func_array($this->fallback, [$this, $id]);
+        }
+        return $result;
+    }
+
+    /**
+     * Set an object in the cache. This function should be overridden
+     * by subclasses.
+     */
+    public function set($id, $value)
+    {
+        return $this->setCache($id, $value);
+    }
+
+    /**
+     * Flush the cache.
+     */
+    public function flush()
+    {
+    }
+
+    /**
+     * Set the entire contents of the cache. May (should) be overridden
+     * by subclasses.
+     */
+    public function setEntireCache($contents)
+    {
+        $this->flush();
+        foreach ($contents as $id => $value) {
+            $this->setCache($id, $value);
+        }
+    }
+
+    /**
+     * Get an object from the cache. This function should be overridden
+     * by subclasses.
+     *
+     * @param string $id
+     */
+    public function getCache($id)
+    {
+        return $this->cacheMiss;
+    }
+
+    /**
+     * Set an object in the cache. This function should be overridden
+     * by subclasses.
+     *
+     * @param string $id
+     */
+    public function setCache($id, $value)
+    {
+    }
+
+    /**
+     * Close the cache. (Optionally overridden by subclasses.)
+     */
+    public function close()
+    {
+    }
+
+    /**
+     * Get the context.
+     */
+    public function getContext()
+    {
+        return $this->context;
+    }
+
+    /**
+     * Get the cache ID within its context
+     */
+    public function getCacheId()
+    {
+        return $this->cacheId;
+    }
+
+    /**
+     * Get the time at which the data was cached.
+     */
+    public function getCacheTime()
+    {
+        // Since it's not really cached, we'll consider it to have been cached just now.
+        return time();
+    }
+}