PHP 缓存实现代码及详细注释

复制代码 代码如下:
class CacheException extends Exception {}

abstract class Cache_Abstract {

abstract public function fetch($key);


abstract public function store($key, $value);


abstract public function delete($key);


abstract public function clear();


abstract public function lock($key);

abstract public function unlock($key);

abstract public function isLocked($key);

public function checkLock($key) {
if (!$this->isLocked($key)) {
return $this;
}

$tries = 10;
$count = 0;
do {
usleep(200);
$count ++;
} while ($count <= $tries && $this->isLocked($key)); // 最多做十次睡眠等待解锁，超时则跳过并解锁
$this->isLocked($key) && $this->unlock($key);

return $this;
}
}


class Cache_Apc extends Cache_Abstract {

protected $_prefix = 'cache.mjie.net';

public function __construct() {
if (!function_exists('apc_cache_info')) {
throw new CacheException('apc extension didn't installed');
}
}


public function store($key, $value) {
return apc_store($this->_storageKey($key), $value);
}


public function fetch($key) {
return apc_fetch($this->_storageKey($key));
}


public function clear() {
apc_clear_cache();
return $this;
}


public function delete($key) {
apc_delete($this->_storageKey($key));
return $this;
}


public function isLocked($key) {
if ((apc_fetch($this->_storageKey($key) . '.lock')) === false) {
return false;
}

return true;
}


public function lock($key) {
apc_store($this->_storageKey($key) . '.lock', '', 5);
return $this;
}


public function unlock($key) {
apc_delete($this->_storageKey($key) . '.lock');
return $this;
}


private function _storageKey($key) {
return $this->_prefix . '_' . $key;
}
}

class Cache_File extends Cache_Abstract {

protected $_cachesDir = 'cache';

public function __construct() {
if (defined('DATA_DIR')) {
$this->_setCacheDir(DATA_DIR . '/cache');
}
}


protected function _getCacheFile($key) {
return $this->_cachesDir . '/' . substr($key, 0, 2) . '/' . $key . '.php';
}

public function fetch($key) {
$cacheFile = self::_getCacheFile($key);
if (file_exists($cacheFile) && is_readable($cacheFile)) {
return unserialize(@file_get_contents($cacheFile, false, NULL, 13));
}
return false;
}

public function store($key, $value) {
$cacheFile = self::_getCacheFile($key);
$cacheDir = dirname($cacheFile);
if(!is_dir($cacheDir)) {
if(mkdir($cacheDir" target="_blank">!@mkdir($cacheDir, 0755, true)) {
throw new CacheException("Could not make cache directory");
}
}
return @file_put_contents($cacheFile, '' . serialize($value));
}

public function delete($key) {
if(emptyempty($key)) {
throw new CacheException("Missing argument 1 for Cache_File::delete()");
}

$cacheFile = self::_getCacheFile($key);
if($cacheFile" target="_blank">!@unlink($cacheFile)) {
throw new CacheException("Cache file could not be deleted");
}
return $this;
}

public function isLocked($key) {
$cacheFile = self::_getCacheFile($key);
clearstatcache();
return file_exists($cacheFile . '.lock');
}

public function lock($key) {
$cacheFile = self::_getCacheFile($key);
$cacheDir = dirname($cacheFile);
if(!is_dir($cacheDir)) {
if(mkdir($cacheDir" target="_blank">!@mkdir($cacheDir, 0755, true)) {
if(!is_dir($cacheDir)) {
throw new CacheException("Could not make cache directory");
}
}
}
// 设定缓存锁文件的访问和修改时间
@touch($cacheFile . '.lock');
return $this;
}


public function unlock($key) {
$cacheFile = self::_getCacheFile($key);
@unlink($cacheFile . '.lock');
return $this;
}

protected function _setCacheDir($dir) {
$this->_cachesDir = rtrim(str_replace('\', '/', trim($dir)), '/');
clearstatcache();
if(!is_dir($this->_cachesDir)) {
mkdir($this->_cachesDir, 0755, true);
}
//
return $this;
}


public function clear() {
// 遍历目录清除缓存
$cacheDir = $this->_cachesDir;
$d = dir($cacheDir);
while(false !== ($entry = $d->read())) {
if('.' == $entry[0]) {
continue;
}

$cacheEntry = $cacheDir . '/' . $entry;
if(is_file($cacheEntry)) {
@unlink($cacheEntry);
} elseif(is_dir($cacheEntry)) {
// 缓存文件夹有两级
$d2 = dir($cacheEntry);
while(false !== ($entry = $d2->read())) {
if('.' == $entry[0]) {
continue;
}

$cacheEntry .= '/' . $entry;
if(is_file($cacheEntry)) {
@unlink($cacheEntry);
}
}
$d2->close();
}
}
$d->close();

return $this;
}
}

final class Cache {

private $_expire = 3600;

private $_storage = null;

static public function createCache($cacheClass = 'Cache_File') {
return new self($cacheClass);
}
private function __construct($cacheClass) {
$this->_storage = new $cacheClass();
}

public function set($key, $value, $expire = false) {
if (!$expire) {
$expire = $this->_expire;
}

$this->_storage->checkLock($key);

$data = array('time' => time(), 'expire' => $expire, 'valid' => true, 'data' => $value);
$this->_storage->lock($key);

try {
$this->_storage->store($key, $data);
$this->_storage->unlock($key);
} catch (CacheException $e) {
$this->_storage->unlock($key);
throw $e;
}
}

public function get($key) {
$data = $this->fetch($key);
if ($data && $data['valid'] && !$data['isExpired']) {
return $data['data'];
}

return false;
}

public function fetch($key) {
$this->_storage->checkLock($key);
$data = $this->_storage->fetch($key);
if ($data) {
$data['isExpired'] = (time() - $data['time']) > $data['expire'] ? true : false;
return $data;
}

return false;
}

public function delete($key) {
$this->_storage->checkLock($key)
->lock($key)
->delete($key)
->unlock($key);
}

public function clear() {
$this->_storage->clear();
}

public function setInvalidate($key) {
$this->_storage->checkLock($key)
->lock($key);
try {
$data = $this->_storage->fetch($key);
if ($data) {
$data['valid'] = false;
$this->_storage->store($key, $data);
}
$this->_storage->unlock($key);
} catch (CacheException $e) {
$this->_storage->unlock($key);
throw $e;
}
}


public function setExpire($expire) {
$this->_expire = (int) $expire;
return $this;
}
}