<?php



/**

 * This file is part of the Nette Framework.

 *

 * Copyright (c) 2004, 2010 David Grudl (http://davidgrudl.com)

 *

 * This source file is subject to the "Nette license", and/or

 * GPL license. For more information please see http://nette.org

 */



namespace Nette;



use Nette;







/**

 * Thread safe / atomic file manipulation. Stream safe://

 *

 * <code>

 * file_put_contents('safe://myfile.txt', $content);

 *

 * $content = file_get_contents('safe://myfile.txt');

 *

 * unlink('safe://myfile.txt');

 * </code>

 *

 * @author     David Grudl

 */

final class SafeStream

{

	/**

	 * Name of stream protocol - safe://

	 */

	const PROTOCOL = 'safe';



	/**

	 * Current file handle.

	 */

	private $handle;



	/**

	 * Renaming of temporary file.

	 */

	private $filePath;

	private $tempFile;



	/**

	 * Starting position in file (for appending).

	 */

	private $startPos = 0;



	/**

	 * Write-error detected?

	 */

	private $writeError = FALSE;







	/**

	 * Registers protocol 'safe://'.

	 * @return bool

	 */

	public static function register()

	{

		return stream_wrapper_register(self::PROTOCOL, __CLASS__);

	}







	/**

	 * Opens file.

	 * @param  string    file name with stream protocol

	 * @param  string    mode - see fopen()

	 * @param  int       STREAM_USE_PATH, STREAM_REPORT_ERRORS

	 * @param  string    full path

	 * @return bool      TRUE on success or FALSE on failure

	 */

	public function stream_open($path, $mode, $options, &$opened_path)

	{

		$path = substr($path, strlen(self::PROTOCOL)+3);  // trim protocol safe://



		$flag = trim($mode, 'rwax+');  // text | binary mode

		$mode = trim($mode, 'tb');     // mode

		$use_path = (bool) (STREAM_USE_PATH & $options); // use include_path?



		$append = FALSE;



		switch ($mode) {

		case 'r':

		case 'r+':

			// enter critical section: open and lock EXISTING file for reading/writing

			$handle = @fopen($path, $mode.$flag, $use_path); // intentionally @

			if (!$handle) return FALSE;

			if (flock($handle, $mode == 'r' ? LOCK_SH : LOCK_EX)) {

				$this->handle = $handle;

				return TRUE;

			}

			fclose($handle);

			return FALSE;



		case 'a':

		case 'a+': $append = TRUE;

		case 'w':

		case 'w+':

			// try enter critical section: open and lock EXISTING file for rewriting

			$handle = @fopen($path, 'r+'.$flag, $use_path); // intentionally @



			if ($handle) {

				if (flock($handle, LOCK_EX)) {

					if ($append) {

						fseek($handle, 0, SEEK_END);

						$this->startPos = ftell($handle);

					} else {

						ftruncate($handle, 0);

					}

					$this->handle = $handle;

					return TRUE;

				}

				fclose($handle);

			}

			// file doesn't exists, continue...

			$mode{0} = 'x'; // x || x+



		case 'x':

		case 'x+':

			if (file_exists($path)) return FALSE;



			// create temporary file in the same directory

			$tmp = '~~' . time() . '.tmp';



			// enter critical section: create temporary file

			$handle = @fopen($path . $tmp, $mode . $flag, $use_path); // intentionally @

			if ($handle) {

				if (flock($handle, LOCK_EX)) {

					$this->handle = $handle;

					if (!@rename($path . $tmp, $path)) { // intentionally @

						// rename later - for windows

						$this->tempFile = realpath($path . $tmp);

						$this->filePath = substr($this->tempFile, 0, -strlen($tmp));

					}

					return TRUE;

				}

				fclose($handle);

				unlink($path . $tmp);

			}

			return FALSE;



		default:

			trigger_error("Unsupported mode $mode", E_USER_WARNING);

			return FALSE;

		} // switch



	} // stream_open







	/**

	 * Closes file.

	 * @return void

	 */

	public function stream_close()

	{

		if ($this->writeError) {

			ftruncate($this->handle, $this->startPos);

		}



		flock($this->handle, LOCK_UN);

		fclose($this->handle);



		// are we working with temporary file?

		if ($this->tempFile) {

			// try to rename temp file, otherwise delete temp file

			if (!@rename($this->tempFile, $this->filePath)) { // intentionally @

				unlink($this->tempFile);

			}

		}

	}







	/**

	 * Reads up to length bytes from the file.

	 * @param  int    length

	 * @return string

	 */

	public function stream_read($length)

	{

		return fread($this->handle, $length);

	}







	/**

	 * Writes the string to the file.

	 * @param  string    data to write

	 * @return int      number of bytes that were successfully stored

	 */

	public function stream_write($data)

	{

		$len = strlen($data);

		$res = fwrite($this->handle, $data, $len);



		if ($res !== $len) { // disk full?

			$this->writeError = TRUE;

		}



		return $res;

	}







	/**

	 * Returns the position of the file.

	 * @return int

	 */

	public function stream_tell()

	{

		return ftell($this->handle);

	}







	/**

	 * Returns TRUE if the file pointer is at end-of-file.

	 * @return bool

	 */

	public function stream_eof()

	{

		return feof($this->handle);

	}







	/**

	 * Sets the file position indicator for the file.

	 * @param  int    position

	 * @param  int    see fseek()

	 * @return int   Return TRUE on success

	 */

	public function stream_seek($offset, $whence)

	{

		return fseek($this->handle, $offset, $whence) === 0; // ???

	}







	/**

	 * Gets information about a file referenced by $this->handle.

	 * @return array

	 */

	public function stream_stat()

	{

		return fstat($this->handle);

	}







	/**

	 * Gets information about a file referenced by filename.

	 * @param  string    file name

	 * @param  int       STREAM_URL_STAT_LINK, STREAM_URL_STAT_QUIET

	 * @return array

	 */

	public function url_stat($path, $flags)

	{

		// This is not thread safe

		$path = substr($path, strlen(self::PROTOCOL)+3);

		return ($flags & STREAM_URL_STAT_LINK) ? @lstat($path) : @stat($path); // intentionally @

	}







	/**

	 * Deletes a file.

	 * On Windows unlink is not allowed till file is opened

	 * @param  string    file name with stream protocol

	 * @return bool      TRUE on success or FALSE on failure

	 */

	public function unlink($path)

	{

		$path = substr($path, strlen(self::PROTOCOL)+3);

		return unlink($path);

	}



}