<?php
	// THIS IS NOT SAFE - there is a major bug - DO NOT USE IT

	/**
	 * Thread safe cache for PHP5
	 *
	 * @author Jan "johno" Suchal <johno@jsmf.net>
	 */

	class SafeCache {
		private $file;
		private $sleepDelay;
		private $spinLimit;
		
		public function __construct($file, $sleepDelay = 1000, $spinLimit = 1000) {
			$this->file = $file;
			$this->sleepDelay = $sleepDelay;
			$this->spinLimit = $spinLimit;
		}
		
		public function get() {
			$handle = @fopen($this->file, 'r');
			if($handle === false || !$this->acquireLock($handle, LOCK_SH)) return false;
			$data = $this->getFileContents($handle);
			$this->releaseLock($handle);
			fclose($handle);
			return $data;
		}
		
		public function save($data) {
			$handle = @fopen($this->file, 'a');
			if($handle === false || !$this->acquireLock($handle, LOCK_EX)) return false;
			ftruncate($handle, 0);
			fwrite($handle, $data);
			$this->releaseLock($handle);
			fclose($handle);
			return true;
		}
		
		private function acquireLock($handle, $type) {
			$hasLock = false;
			$counter = 0;
			while(!$hasLock) {
				$hasLock = flock($handle, $type + LOCK_NB);
				if($counter++ > $this->spinLimit) {
					fclose($handle);
					return false;
				}
				usleep($this->sleepDelay);
			}
			return true;
		}
		
		private function releaseLock($handle) {
			flock($handle, LOCK_UN);
		}
	
		private function getFileContents($handle) {
			$data = '';
			while (!feof($handle)) {
				$data .= fread($handle, 8192);
			}
			return $data;
		}
	}
?>