Implemented group read/write support for the ApcEngine

lib/Cake/Cache/Cache.php

@@ -91,6 +91,8 @@ class Cache {
  * The following keys are used in core cache engines:
  *
  * - `duration` Specify how long items in this cache configuration last.
+ * - `groups` List of groups or 'tags' associated to every key stored in this config.
+ *    handy for deleting a complete group from cache.
  * - `prefix` Prefix appended to all entries. Good for when you need to share a keyspace
  *    with either another cache config or another application.
  * - `probability` Probability of hitting a cache gc cleanup.  Setting to 0 will disable

lib/Cake/Cache/CacheEngine.php

@@ -27,6 +27,14 @@ abstract class CacheEngine {
  */
 	public $settings = array();
 
+/**
+ * Contains the compiled string with all groups
+ * prefixes to be prepeded to every key in this cache engine
+ *
+ * @var string
+ **/
+	protected $groupPrefix = null;
+
 /**
  * Initialize the cache engine
  *
@@ -37,10 +45,14 @@ abstract class CacheEngine {
  */
 	public function init($settings = array()) {
 		$this->settings = array_merge(
-			array('prefix' => 'cake_', 'duration' => 3600, 'probability' => 100),
+			array('prefix' => 'cake_', 'duration' => 3600, 'probability' => 100, 'groups' => array()),
 			$this->settings,
 			$settings
 		);
+		if (!empty($this->settings['groups'])) {
+			sort($this->settings['groups']);
+			$this->groupPrefix = str_repeat('%s_', count($this->settings['groups']));
+		}
 		if (!is_numeric($this->settings['duration'])) {
 			$this->settings['duration'] = strtotime($this->settings['duration']) - time();
 		}
@@ -108,6 +120,17 @@ abstract public function delete($key);
  */
 	abstract public function clear($check);
 
+/**
+ * Does whatever initialization for each group is required
+ * and returns the `group value` for each of them, this is
+ * the token representing each group in the cache key
+ *
+ * @return array
+ **/
+ 	public function groups() {
+ 		return $this->settings['groups'];
+ 	}
+
 /**
  * Cache Engine settings
  *
@@ -127,8 +150,14 @@ public function key($key) {
 		if (empty($key)) {
 			return false;
 		}
+
+		$prefix = '';
+		if (!empty($this->groupPrefix)) {
+			$prefix = vsprintf($this->groupPrefix, $this->groups());
+		}
+
 		$key = Inflector::underscore(str_replace(array(DS, '/', '.'), '_', strval($key)));
-		return $key;
+		return $prefix . $key;
 	}
 
 }

lib/Cake/Cache/Engine/ApcEngine.php

@@ -127,4 +127,30 @@ public function clear($check) {
 		return true;
 	}
 
+/**
+ * Returns the `group value` for each of the configured groups
+ * If the group initial value was not found, then it initializes
+ * the group accordingly.
+ *
+ * @return array
+ **/
+	public function groups() {
+		$groups = apc_fetch($this->settings['groups']);
+
+		if (count($groups) !== count($this->settings['groups'])) {
+			foreach ($this->settings['groups'] as $group) {
+				if (!isset($groups[$group])) {
+					apc_store($group, 1);
+					$groups[$group] = 1;
+				}
+			}
+			ksort($groups);
+		}
+
+		$result = array();
+		foreach ($groups as $group => $value) {
+			$result[] = $group . $value;
+		}
+		return $result;
+	}
 }

lib/Cake/Test/Case/Cache/Engine/ApcEngineTest.php

@@ -47,6 +47,7 @@ public function setUp() {
 	public function tearDown() {
 		Configure::write('Cache.disable', $this->_cacheDisable);
 		Cache::drop('apc');
+		Cache::drop('apc_groups');
 		Cache::config('default');
 	}
 
@@ -198,4 +199,27 @@ public function testClear() {
 		$this->assertEquals('survive', apc_fetch('not_cake'));
 		apc_delete('not_cake');
 	}
+
+/**
+ * Tests that configuring groups for stored keys return the correct values when read/written
+ * Shows that altering the group value is equivalent to deleting all keys under the same
+ * group
+ *
+ * @return void
+ */
+	public function testGroupsReadWrite() {
+		Cache::config('apc_groups', array('engine' => 'Apc', 'duration' => 0, 'groups' => array('group_a', 'group_b')));
+		$this->assertTrue(Cache::write('test_groups', 'value', 'apc_groups'));
+		$this->assertEquals('value', Cache::read('test_groups', 'apc_groups'));
+
+		apc_inc('group_a');
+		$this->assertFalse(Cache::read('test_groups', 'apc_groups'));
+		$this->assertTrue(Cache::write('test_groups', 'value2', 'apc_groups'));
+		$this->assertEquals('value2', Cache::read('test_groups', 'apc_groups'));
+
+		apc_inc('group_b');
+		$this->assertFalse(Cache::read('test_groups', 'apc_groups'));
+		$this->assertTrue(Cache::write('test_groups', 'value3', 'apc_groups'));
+		$this->assertEquals('value3', Cache::read('test_groups', 'apc_groups'));
+	}
 }