<?php
class Mutex {
var $writeablePath = '';
var $lockName = '';
var $fileHandle = null;
public function __construct($lockName, $writeablePath = null){
$this->lockName = preg_replace('/[^a-zA-Z0-9]/', '', $lockName);
if($writeablePath == null){
$this->writeablePath = $this->findWriteablePath();
} else {
$this->writeablePath = $writeablePath;
}
}
public function lock($wait = false, $maxTime = 10){
$locked = false;
$timeAsleep = 0;
do{
$locked = $this->attemptLock();
if(!$locked && $wait){
sleep(1);
$timeAsleep +=1;
}
} while(!$locked && $wait && $timeAsleep <= $maxTime);
return $locked;
}
private function attemptLock(){
if (PHP_OS == 'WINNT'){
$lockFilePath = $this->getLockFilePath();
if(file_exists($lockFilePath)){
$unlinked = @unlink($lockFilePath);
if(!$unlinked) return false;
}
}
$fileHandle = $this->getFileHandle();
if(!$fileHandle){
return false;
} else {
return true;
}
}
public function getFileHandle(){
if(!$this->fileHandle){
$this->fileHandle = @fopen($this->getLockFilePath(), 'a+');
if($this->fileHandle){
if (PHP_OS == 'WINNT'){
fwrite($this->fileHandle, "A");
if(flock($this->fileHandle, LOCK_SH)){
rewind($this->fileHandle);
$contents = fread($this->fileHandle, 2);
if($contents != 'A'){
flock($this->fileHandle, LOCK_UN);
fclose($this->fileHandle);
$this->fileHandle = null;
return false;
}
} else {
fclose($this->fileHandle);
return false;
}
} else {
if(flock($this->fileHandle, LOCK_EX | LOCK_NB)){
} else {
fclose($this->fileHandle);
return false;
}
}
}
}
return $this->fileHandle;
}
public function releaseLock(){
flock($this->fileHandle, LOCK_UN);
$success = fclose($this->getFileHandle());
unlink($this->getLockFilePath());
$this->fileHandle = null;
return $success;
}
public function getLockFilePath(){
return $this->writeablePath . DIRECTORY_SEPARATOR . $this->lockName;
}
public function isLocked(){
$lock = $this->attemptLock();
if($lock){
$this->releaseLock();
return false;
}else{
return true;
}
}
public function findWriteablePath(){
$foundPath = false;
//First try the temp directory...
$path = $this->getTempDirPath();
$fileName = $path . DIRECTORY_SEPARATOR . 'test_file';
if($fileHandle = fopen($fileName, "w")){
fclose($fileHandle);
$foundPath = true;
}
//Now try the current directory
if(!$foundPath){
$path = '.';
if($fileHandle = fopen($path . DIRECTORY_SEPARATOR . 'test_file', "w")){
fclose($fileHandle);
$this->writeablePath = $path;
}
}
if(!$foundPath){
throw new Exception("Cannot establish lock on temporary file.");
}
return $path;
}
public function getTempDirPath(){
$fileName = tempnam("/tmp", "MUT");
$path = dirname($fileName);
if ($path == '/') $path = '/tmp';
return $path;
}
}
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