Merge pull request aws#548 from aws/stream-wrapper-cache

Added support for injectable cache to stream wrapper.

src/CacheInterface.php

@@ -0,0 +1,34 @@
+<?php
+namespace Aws;
+
+/**
+ * Represents a simple cache interface.
+ */
+interface CacheInterface
+{
+    /**
+     * Get a cache item by key.
+     *
+     * @param string $key Key to retrieve.
+     *
+     * @return mixed|null Returns the value or null if not found.
+     */
+    public function get($key);
+
+    /**
+     * Set a cache key value.
+     *
+     * @param string $key   Key to set
+     * @param mixed  $value Value to set.
+     * @param int    $ttl   Number of seconds the item is allowed to live. Set
+     *                      to 0 to allow an unlimited lifetime.
+     */
+    public function set($key, $value, $ttl = 0);
+
+    /**
+     * Remove a cache key.
+     *
+     * @param string $key Key to remove.
+     */
+    public function remove($key);
+}

src/LruArrayCache.php

@@ -0,0 +1,74 @@
+<?php
+namespace Aws;
+
+/**
+ * Simple in-memory LRU cache that limits the number of cached entries.
+ *
+ * The LRU cache is implemented using PHP's ordered associative array. When
+ * accessing an element, the element is removed from the hash and re-added to
+ * ensure that recently used items are always at the end of the list while
+ * least recently used are at the beginning. When a value is added to the
+ * cache, if the number of cached items exceeds the allowed number, the first
+ * N number of items are removed from the array.
+ */
+class LruArrayCache implements CacheInterface
+{
+    /** @var int */
+    private $maxItems;
+
+    /** @var array */
+    private $items;
+
+    /**
+     * @param int $maxItems Maximum number of allowed cache items.
+     */
+    public function __construct($maxItems = 1000)
+    {
+        $this->maxItems = $maxItems;
+    }
+
+    public function get($key)
+    {
+        if (!isset($this->items[$key])) {
+            return null;
+        }
+
+        $entry = $this->items[$key];
+
+        // Ensure the item is not expired.
+        if (!$entry[1] || time() < $entry[1]) {
+            // LRU: remove the item and push it to the end of the array.
+            unset($this->items[$key]);
+            $this->items[$key] = $entry;
+            return $entry[0];
+        }
+
+        unset($this->items[$key]);
+        return null;
+    }
+
+    public function set($key, $value, $ttl = 0)
+    {
+        // Only call time() if the TTL is not 0/false/null
+        $ttl = $ttl ? time() + $ttl : 0;
+        $this->items[$key] = [$value, $ttl];
+
+        // Determine if there are more items in the cache than allowed.
+        $diff = count($this->items) - $this->maxItems;
+
+        // Clear out least recently used items.
+        if ($diff > 0) {
+            // Reset to the beginning of the array and begin unsetting.
+            reset($this->items);
+            for ($i = 0; $i < $diff; $i++) {
+                unset($this->items[key($this->items)]);
+                next($this->items);
+            }
+        }
+    }
+
+    public function remove($key)
+    {
+        unset($this->items[$key]);
+    }
+}