PHP operates shared memory shmop class and simple usage test (code)

SimpleSHM 是一个较小的抽象层，用于使用 PHP 操作共享内存，支持以一种面向对象的方式轻松操作内存段。在编写使用共享内存进行存储的小型应用程序时，这个库可帮助创建非常简洁的代码。可以使用 3 个方法进行处理：读、写和删除。从该类中简单地实例化一个对象，可以控制打开的共享内存段。

类对象和测试代码

id = $this->generateID(); } else { $this->id = $id; } if($this->exists($this->id)) { $this->shmid = shmop_open($this->id, "w", 0, 0); } } /** * Generates a random ID for a shared memory block * * @access protected * @return int System V IPC key generated from pathname and a project identifier */ protected function generateID() { $id = ftok(__FILE__, "b"); return $id; } /** * Checks if a shared memory block with the provided id exists or not * * In order to check for shared memory existance, we have to open it with * reading access. If it doesn't exist, warnings will be cast, therefore we * suppress those with the @ operator. * * @access public * @param string $id ID of the shared memory block you want to check * @return boolean True if the block exists, false if it doesn't */ public function exists($id) { $status = @shmop_open($id, "a", 0, 0); return $status; } /** * Writes on a shared memory block * * First we check for the block existance, and if it doesn't, we'll create it. Now, if the * block already exists, we need to delete it and create it again with a new byte allocation that * matches the size of the data that we want to write there. We mark for deletion, close the semaphore * and create it again. * * @access public * @param string $data The data that you wan't to write into the shared memory block */ public function write($data) { $size = mb_strlen($data, 'UTF-8'); if($this->exists($this->id)) { shmop_delete($this->shmid); shmop_close($this->shmid); $this->shmid = shmop_open($this->id, "c", $this->perms, $size); shmop_write($this->shmid, $data, 0); } else { $this->shmid = shmop_open($this->id, "c", $this->perms, $size); shmop_write($this->shmid, $data, 0); } } /** * Reads from a shared memory block * * @access public * @return string The data read from the shared memory block */ public function read() { $size = shmop_size($this->shmid); $data = shmop_read($this->shmid, 0, $size); return $data; } /** * Mark a shared memory block for deletion * * @access public */ public function delete() { shmop_delete($this->shmid); } /** * Gets the current shared memory block id * * @access public */ public function getId() { return $this->id; } /** * Gets the current shared memory block permissions * * @access public */ public function getPermissions() { return $this->perms; } /** * Sets the default permission (octal) that will be used in created memory blocks * * @access public * @param string $perms Permissions, in octal form */ public function setPermissions($perms) { $this->perms = $perms; } /** * Closes the shared memory block and stops manipulation * * @access public */ public function __destruct() { shmop_close($this->shmid); } }

assertInstanceOf('Simple\\SHM\\Block', $memory); $memory->write('Sample'); $data = $memory->read(); $this->assertEquals('Sample', $data); } public function testIsCreatingNewBlockWithId() { $memory = new Block(897); $this->assertInstanceOf('Simple\\SHM\\Block', $memory); $this->assertEquals(897, $memory->getId()); $memory->write('Sample 2'); $data = $memory->read(); $this->assertEquals('Sample 2', $data); } public function testIsMarkingBlockForDeletion() { $memory = new Block(897); $memory->delete(); $data = $memory->read(); $this->assertEquals('Sample 2', $data); } public function testIsPersistingNewBlockWithoutId() { $memory = new Block; $this->assertInstanceOf('Simple\\SHM\\Block', $memory); $memory->write('Sample 3'); unset($memory); $memory = new Block; $data = $memory->read(); $this->assertEquals('Sample 3', $data); } }

额外说明

write('Sample'); echo $memory->read(); ?>

请注意，上面代码里没有为该类传递一个 ID。如果没有传递 ID，它将随机选择一个编号并打开该编号的新内存段。我们可以以参数的形式传递一个编号，供构造函数打开现有的内存段，或者创建一个具有特定 ID 的内存段，如下

write('Sample'); echo $new->read(); ?>

神奇的方法 __destructor 负责在该内存段上调用 shmop_close 来取消设置对象，以与该内存段分离。我们将这称为 “SimpleSHM 101”。现在让我们将此方法用于更高级的用途：使用共享内存作为存储。存储数据集需要序列化，因为数组或对象无法存储在内存中。尽管这里使用了 JSON 来序列化，但任何其他方法（比如 XML 或内置的 PHP 序列化功能）也已足够。如下

 'John', 'password' => '123456', 'posts' => array('My name is John', 'My name is not John') ); $data = json_encode($results); $memory = new SimpleSHM; $memory->write($data); $storedarray = json_decode($memory->read()); print_r($storedarray); ?>

我们成功地将一个数组序列化为一个 JSON 字符串，将它存储在共享内存块中，从中读取数据，去序列化 JSON 字符串，并显示存储的数组。这看起来很简单，但请想象一下这个代码片段带来的可能性。您可以使用它存储 Web 服务请求、数据库查询或者甚至模板引擎缓存的结果。在内存中读取和写入将带来比在磁盘中读取和写入更高的性能。

使用此存储技术不仅对缓存有用，也对应用程序之间的数据交换也有用，只要数据以两端都可读的格式存储。不要低估共享内存在 Web 应用程序中的力量。可采用许多不同的方式来巧妙地实现这种存储，惟一的限制是开发人员的创造力和技能。

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