Cache add() method added for all Cache engines.

lib/Cake/Cache/Cache.php

@@ -578,4 +578,41 @@ public static function remember($key, $callable, $config = 'default') {
 		return $results;
 	}
 
+/**
+ * Write data for key into a cache engine if it doesn't exist already.
+ *
+ * ### Usage:
+ *
+ * Writing to the active cache config:
+ *
+ * `Cache::add('cached_data', $data);`
+ *
+ * Writing to a specific cache config:
+ *
+ * `Cache::add('cached_data', $data, 'long_term');`
+ *
+ * @param string $key Identifier for the data.
+ * @param mixed $value Data to be cached - anything except a resource.
+ * @param string $config Optional string configuration name to write to. Defaults to 'default'.
+ * @return bool True if the data was successfully cached, false on failure.
+ */
+	public static function add($key, $value, $config = 'default') {
+		$settings = self::settings($config);
+
+		if (empty($settings)) {
+			return false;
+		}
+		if (!self::isInitialized($config)) {
+			return false;
+		}
+		$key = self::$_engines[$config]->key($key);
+
+		if (!$key || is_resource($value)) {
+			return false;
+		}
+
+		$success = self::$_engines[$config]->add($settings['prefix'] . $key, $value, $settings['duration']);
+		self::set(null, $config);
+		return $success;
+	}
 }

lib/Cake/Cache/CacheEngine.php

@@ -83,6 +83,17 @@ public function gc($expires = null) {
  */
 	abstract public function write($key, $value, $duration);
 
+/**
+ * Write value for a key into cache if it doesn't already exist
+ *
+ * @param string $key Identifier for the data
+ * @param mixed $value Data to be cached
+ * @param int $duration How long to cache for.
+ * @return bool True if the data was successfully cached, false on failure
+ */
+	public function add($key, $value, $duration) {
+	}
+
 /**
  * Read a key from the cache
  *
@@ -176,5 +187,4 @@ public function key($key) {
 		$key = preg_replace('/[\s]+/', '_', strtolower(trim(str_replace(array(DS, '/', '.'), '_', strval($key)))));
 		return $prefix . $key;
 	}
-
 }

lib/Cake/Cache/Engine/ApcEngine.php

@@ -188,4 +188,22 @@ public function clearGroup($group) {
 		return $success;
 	}
 
+/**
+ * Write data for key into cache if it doesn't exist already. 
+ * If it already exists, it fails and returns false.
+ *
+ * @param string $key Identifier for the data.
+ * @param mixed $value Data to be cached.
+ * @param int $duration How long to cache the data, in seconds.
+ * @return bool True if the data was successfully cached, false on failure.
+ * @link http://php.net/manual/en/function.apc-add.php
+ */
+	public function add($key, $value, $duration) {
+		$expires = 0;
+		if ($duration) {
+			$expires = time() + $duration;
+		}
+		apc_add($key . '_expires', $expires, $duration);
+		return apc_add($key, $value, $duration);
+	}
 }

lib/Cake/Cache/Engine/FileEngine.php

@@ -429,4 +429,21 @@ public function clearGroup($group) {
 		}
 		return true;
 	}
+
+/**
+ * Write data for key into cache if it doesn't exist already.
+ * If it already exists, it fails and returns false.
+ *
+ * @param string $key Identifier for the data.
+ * @param mixed $value Data to be cached.
+ * @param int $duration How long to cache the data, in seconds.
+ * @return bool True if the data was successfully cached, false on failure.
+ */
+	public function add($key, $value, $duration) {
+		$cachedValue = $this->read($key);
+		if ($cachedValue === false) {
+			return $this->write($key, $value, $duration);
+		}
+		return false;
+	}
 }

lib/Cake/Cache/Engine/MemcacheEngine.php

@@ -289,4 +289,24 @@ public function groups() {
 	public function clearGroup($group) {
 		return (bool)$this->_Memcache->increment($this->settings['prefix'] . $group);
 	}
+
+/**
+ * Write data for key into cache if it doesn't exist already. When using memcached as your cache engine
+ * remember that the Memcached pecl extension does not support cache expiry times greater
+ * than 30 days in the future. Any duration greater than 30 days will be treated as never expiring.
+ * If it already exists, it fails and returns false.
+ *
+ * @param string $key Identifier for the data.
+ * @param mixed $value Data to be cached.
+ * @param int $duration How long to cache the data, in seconds.
+ * @return bool True if the data was successfully cached, false on failure.
+ * @link http://php.net/manual/en/memcache.add.php
+ */
+	public function add($key, $value, $duration) {
+		if ($duration > 30 * DAY) {
+			$duration = 0;
+		}
+
+		return $this->_Memcache->add($key, $value, $this->settings['compress'], $duration);
+	}
 }

lib/Cake/Cache/Engine/MemcachedEngine.php

@@ -335,4 +335,24 @@ public function groups() {
 	public function clearGroup($group) {
 		return (bool)$this->_Memcached->increment($this->settings['prefix'] . $group);
 	}
+
+/**
+ * Write data for key into cache if it doesn't exist already. When using memcached as your cache engine
+ * remember that the Memcached pecl extension does not support cache expiry times greater
+ * than 30 days in the future. Any duration greater than 30 days will be treated as never expiring.
+ * If it already exists, it fails and returns false.
+ *
+ * @param string $key Identifier for the data.
+ * @param mixed $value Data to be cached.
+ * @param int $duration How long to cache the data, in seconds.
+ * @return bool True if the data was successfully cached, false on failure.
+ * @link http://php.net/manual/en/memcached.add.php
+ */
+	public function add($key, $value, $duration) {
+		if ($duration > 30 * DAY) {
+			$duration = 0;
+		}
+
+		return $this->_Memcached->add($key, $value, $duration);
+	}
 }

lib/Cake/Cache/Engine/RedisEngine.php

@@ -227,4 +227,23 @@ public function __destruct() {
 			$this->_Redis->close();
 		}
 	}
+
+/**
+ * Write data for key into cache if it doesn't exist already. 
+ * If it already exists, it fails and returns false.
+ *
+ * @param string $key Identifier for the data.
+ * @param mixed $value Data to be cached.
+ * @param int $duration How long to cache the data, in seconds.
+ * @return bool True if the data was successfully cached, false on failure.
+ * @link https://github.com/phpredis/phpredis#setnx
+ */
+	public function add($key, $value, $duration) {
+		$result = $this->_Redis->setnx($key, $value);
+		// setnx() doesn't have an expiry option, so overwrite the key with one
+		if ($result) {
+			return $this->_Redis->setex($key, $value, $duration);
+		}
+		return false;
+	}
 }

lib/Cake/Cache/Engine/WincacheEngine.php

@@ -188,4 +188,20 @@ public function clearGroup($group) {
 		return $success;
 	}
 
+/**
+ * Write data for key into cache if it doesn't exist already.
+ * If it already exists, it fails and returns false.
+ *
+ * @param string $key Identifier for the data.
+ * @param mixed $value Data to be cached.
+ * @param int $duration How long to cache the data, in seconds.
+ * @return bool True if the data was successfully cached, false on failure.
+ */
+	public function add($key, $value, $duration) {
+		$cachedValue = $this->read($key);
+		if ($cachedValue === false) {
+			return $this->write($key, $value, $duration);
+		}
+		return false;
+	}
 }

lib/Cake/Cache/Engine/XcacheEngine.php

@@ -207,4 +207,21 @@ protected function _auth($reverse = false) {
 			}
 		}
 	}
+
+/**
+ * Write data for key into cache if it doesn't exist already.
+ * If it already exists, it fails and returns false.
+ *
+ * @param string $key Identifier for the data.
+ * @param mixed $value Data to be cached.
+ * @param int $duration How long to cache the data, in seconds.
+ * @return bool True if the data was successfully cached, false on failure.
+ */
+	public function add($key, $value, $duration) {
+		$cachedValue = $this->read($key);
+		if ($cachedValue === false) {
+			return $this->write($key, $value, $duration);
+		}
+		return false;
+	}
 }

lib/Cake/Test/Case/Cache/CacheTest.php

@@ -519,4 +519,23 @@ public function testRemember() {
 	public function cacher() {
 		return 'This is some data ' . $this->_count;
 	}
+
+/**
+ * Test add method.
+ *
+ * @return void
+ */
+	public function testAdd() {
+		Cache::delete('test_add_key', 'default');
+
+		$result = Cache::add('test_add_key', 'test data', 'default');
+		$this->assertTrue($result);
+
+		$expected = 'test data';
+		$result = Cache::read('test_add_key', 'default');
+		$this->assertEquals($expected, $result);
+
+		$result = Cache::add('test_add_key', 'test data 2', 'default');
+		$this->assertFalse($result);
+	}
 }

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

@@ -273,4 +273,23 @@ public function testGroupClear() {
 		$this->assertTrue(Cache::clearGroup('group_b', 'apc_groups'));
 		$this->assertFalse(Cache::read('test_groups', 'apc_groups'));
 	}
+
+/**
+ * Test that failed add write return false.
+ *
+ * @return void
+ */
+	public function testAdd() {
+		Cache::delete('test_add_key', 'apc');
+
+		$result = Cache::add('test_add_key', 'test data', 'apc');
+		$this->assertTrue($result);
+
+		$expected = 'test data';
+		$result = Cache::read('test_add_key', 'apc');
+		$this->assertEquals($expected, $result);
+
+		$result = Cache::add('test_add_key', 'test data 2', 'apc');
+		$this->assertFalse($result);
+	}
 }

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

@@ -550,4 +550,22 @@ public function testGroupClearNoPrefix() {
 		$this->assertFalse(Cache::read('key_2', 'file_groups'), 'Did not delete');
 	}
 
+/**
+ * Test that failed add write return false.
+ *
+ * @return void
+ */
+	public function testAdd() {
+		Cache::delete('test_add_key', 'file_test');
+
+		$result = Cache::add('test_add_key', 'test data', 'file_test');
+		$this->assertTrue($result);
+
+		$expected = 'test data';
+		$result = Cache::read('test_add_key', 'file_test');
+		$this->assertEquals($expected, $result);
+
+		$result = Cache::add('test_add_key', 'test data 2', 'file_test');
+		$this->assertFalse($result);
+	}
 }

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

@@ -490,4 +490,23 @@ public function testGroupClear() {
 		$this->assertTrue(Cache::clearGroup('group_b', 'memcache_groups'));
 		$this->assertFalse(Cache::read('test_groups', 'memcache_groups'));
 	}
+
+/**
+ * Test that failed add write return false.
+ *
+ * @return void
+ */
+	public function testAdd() {
+		Cache::delete('test_add_key', 'memcache');
+
+		$result = Cache::add('test_add_key', 'test data', 'memcache');
+		$this->assertTrue($result);
+
+		$expected = 'test data';
+		$result = Cache::read('test_add_key', 'memcache');
+		$this->assertEquals($expected, $result);
+
+		$result = Cache::add('test_add_key', 'test data 2', 'memcache');
+		$this->assertFalse($result);
+	}
 }

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

@@ -797,4 +797,24 @@ public function testGroupClear() {
 		$this->assertTrue(Cache::clearGroup('group_b', 'memcached_groups'));
 		$this->assertFalse(Cache::read('test_groups', 'memcached_groups'));
 	}
+
+/**
+ * Test that failed add write return false.
+ *
+ * @return void
+ */
+	public function testAdd() {
+		Cache::set(array('duration' => 1), null, 'memcached');
+		Cache::delete('test_add_key', 'default');
+
+		$result = Cache::add('test_add_key', 'test data', 'default');
+		$this->assertTrue($result);
+
+		$expected = 'test data';
+		$result = Cache::read('test_add_key', 'default');
+		$this->assertEquals($expected, $result);
+
+		$result = Cache::add('test_add_key', 'test data 2', 'default');
+		$this->assertFalse($result);
+	}
 }

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

@@ -381,4 +381,22 @@ public function testGroupClear() {
 		$this->assertFalse(Cache::read('test_groups', 'redis_groups'));
 	}
 
+/**
+ * Test that failed add write return false.
+ *
+ * @return void
+ */
+	public function testAdd() {
+		Cache::delete('test_add_key', 'redis');
+
+		$result = Cache::add('test_add_key', 'test data', 'redis');
+		$this->assertTrue($result);
+
+		$expected = 'test data';
+		$result = Cache::read('test_add_key', 'redis');
+		$this->assertEquals($expected, $result);
+
+		$result = Cache::add('test_add_key', 'test data 2', 'redis');
+		$this->assertFalse($result);
+	}
 }

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

@@ -259,4 +259,23 @@ public function testGroupClear() {
 		$this->assertTrue(Cache::clearGroup('group_b', 'wincache_groups'));
 		$this->assertFalse(Cache::read('test_groups', 'wincache_groups'));
 	}
+
+/**
+ * Test that failed add write return false.
+ *
+ * @return void
+ */
+	public function testAdd() {
+		Cache::delete('test_add_key', 'wincache');
+
+		$result = Cache::add('test_add_key', 'test data', 'wincache');
+		$this->assertTrue($result);
+
+		$expected = 'test data';
+		$result = Cache::read('test_add_key', 'wincache');
+		$this->assertEquals($expected, $result);
+
+		$result = Cache::add('test_add_key', 'test data 2', 'wincache');
+		$this->assertFalse($result);
+	}
 }