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File: mutex.php

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  Classes of Joey Novak  >  Mutex  >  mutex.php  >  Download  
File: mutex.php
Role: Class source
Content type: text/plain
Description: Mutex PHP Class
Class: Mutex
Assure exclusive to resources using file locks
Author: By
Last change: LOTS of updates since our first release.
Date: 2 years ago
Size: 3,955 bytes
 

Contents

Class file image Download
<?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;
    }
}