<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Process;

use Symfony\Component\Process\Exception\RuntimeException;

/**
 * Process is a thin wrapper around proc_* functions to ease
 * start independent PHP processes.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 *
 * @api
 */
class Process
{
    const ERR = 'err';
    const OUT = 'out';

    const STATUS_READY = 'ready';
    const STATUS_STARTED = 'started';
    const STATUS_TERMINATED = 'terminated';

    const STDIN = 0;
    const STDOUT = 1;
    const STDERR = 2;

    // Timeout Precision in seconds.
    const TIMEOUT_PRECISION = 0.2;

    private $commandline;
    private $cwd;
    private $env;
    private $stdin;
    private $starttime;
    private $timeout;
    private $options;
    private $exitcode;
    private $fallbackExitcode;
    private $processInformation;
    private $stdout;
    private $stderr;
    private $enhanceWindowsCompatibility;
    private $enhanceSigchildCompatibility;
    private $pipes;
    private $process;
    private $status = self::STATUS_READY;

    private $fileHandles;
    private $readBytes;

    private static $sigchild;

    /**
     * Exit codes translation table.
     *
     * User-defined errors must use exit codes in the 64-113 range.
     *
     * @var array
     */
    public static $exitCodes = array(
        0 => 'OK',
        1 => 'General error',
        2 => 'Misuse of shell builtins',

        126 => 'Invoked command cannot execute',
        127 => 'Command not found',
        128 => 'Invalid exit argument',

        // signals
        129 => 'Hangup',
        130 => 'Interrupt',
        131 => 'Quit and dump core',
        132 => 'Illegal instruction',
        133 => 'Trace/breakpoint trap',
        134 => 'Process aborted',
        135 => 'Bus error: "access to undefined portion of memory object"',
        136 => 'Floating point exception: "erroneous arithmetic operation"',
        137 => 'Kill (terminate immediately)',
        138 => 'User-defined 1',
        139 => 'Segmentation violation',
        140 => 'User-defined 2',
        141 => 'Write to pipe with no one reading',
        142 => 'Signal raised by alarm',
        143 => 'Termination (request to terminate)',
        // 144 - not defined
        145 => 'Child process terminated, stopped (or continued*)',
        146 => 'Continue if stopped',
        147 => 'Stop executing temporarily',
        148 => 'Terminal stop signal',
        149 => 'Background process attempting to read from tty ("in")',
        150 => 'Background process attempting to write to tty ("out")',
        151 => 'Urgent data available on socket',
        152 => 'CPU time limit exceeded',
        153 => 'File size limit exceeded',
        154 => 'Signal raised by timer counting virtual time: "virtual timer expired"',
        155 => 'Profiling timer expired',
        // 156 - not defined
        157 => 'Pollable event',
        // 158 - not defined
        159 => 'Bad syscall',
    );

    /**
     * Constructor.
     *
     * @param string  $commandline The command line to run
     * @param string  $cwd         The working directory
     * @param array   $env         The environment variables or null to inherit
     * @param string  $stdin       The STDIN content
     * @param integer $timeout     The timeout in seconds
     * @param array   $options     An array of options for proc_open
     *
     * @throws \RuntimeException When proc_open is not installed
     *
     * @api
     */
    public function __construct($commandline, $cwd = null, array $env = null, $stdin = null, $timeout = 60, array $options = array())
    {
        if (!function_exists('proc_open')) {
            throw new \RuntimeException('The Process class relies on proc_open, which is not available on your PHP installation.');
        }

        $this->commandline = $commandline;
        $this->cwd = $cwd;

        // on windows, if the cwd changed via chdir(), proc_open defaults to the dir where php was started
        // on gnu/linux, PHP builds with --enable-maintainer-zts are also affected
        // @see : https://bugs.php.net/bug.php?id=51800
        // @see : https://bugs.php.net/bug.php?id=50524

        if (null === $this->cwd && (defined('ZEND_THREAD_SAFE') || defined('PHP_WINDOWS_VERSION_BUILD'))) {
            $this->cwd = getcwd();
        }
        if (null !== $env) {
            $this->env = array();
            foreach ($env as $key => $value) {
                $this->env[(binary) $key] = (binary) $value;
            }
        } else {
            $this->env = null;
        }
        $this->stdin = $stdin;
        $this->setTimeout($timeout);
        $this->enhanceWindowsCompatibility = true;
        $this->enhanceSigchildCompatibility = !defined('PHP_WINDOWS_VERSION_BUILD') && $this->isSigchildEnabled();
        $this->options = array_replace(array('suppress_errors' => true, 'binary_pipes' => true), $options);
    }

    public function __destruct()
    {
        // stop() will check if we have a process running.
        $this->stop();
    }

    /**
     * Runs the process.
     *
     * The callback receives the type of output (out or err) and
     * some bytes from the output in real-time. It allows to have feedback
     * from the independent process during execution.
     *
     * The STDOUT and STDERR are also available after the process is finished
     * via the getOutput() and getErrorOutput() methods.
     *
     * @param callback|null $callback A PHP callback to run whenever there is some
     *                                output available on STDOUT or STDERR
     *
     * @return integer The exit status code
     *
     * @throws \RuntimeException When process can't be launch or is stopped
     *
     * @api
     */
    public function run($callback = null)
    {
        $this->start($callback);

        return $this->wait($callback);
    }

    /**
     * Starts the process and returns after sending the STDIN.
     *
     * This method blocks until all STDIN data is sent to the process then it
     * returns while the process runs in the background.
     *
     * The termination of the process can be awaited with wait().
     *
     * The callback receives the type of output (out or err) and some bytes from
     * the output in real-time while writing the standard input to the process.
     * It allows to have feedback from the independent process during execution.
     * If there is no callback passed, the wait() method can be called
     * with true as a second parameter then the callback will get all data occurred
     * in (and since) the start call.
     *
     * @param callback|null $callback A PHP callback to run whenever there is some
     *                                output available on STDOUT or STDERR
     *
     * @throws \RuntimeException When process can't be launch or is stopped
     * @throws \RuntimeException When process is already running
     */
    public function start($callback = null)
    {
        if ($this->isRunning()) {
            throw new \RuntimeException('Process is already running');
        }

        $this->starttime = microtime(true);
        $this->stdout = '';
        $this->stderr = '';
        $callback = $this->buildCallback($callback);

        //Fix for PHP bug #51800: reading from STDOUT pipe hangs forever on Windows if the output is too big.
        //Workaround for this problem is to use temporary files instead of pipes on Windows platform.
        //@see https://bugs.php.net/bug.php?id=51800
        if (defined('PHP_WINDOWS_VERSION_BUILD')) {
            $this->fileHandles = array(
                self::STDOUT => tmpfile(),
            );
            if (false === $this->fileHandles[self::STDOUT]) {
                throw new RuntimeException('A temporary file could not be opened to write the process output to, verify that your TEMP environment variable is writable');
            }
            $this->readBytes = array(
                self::STDOUT => 0,
            );
            $descriptors = array(array('pipe', 'r'), $this->fileHandles[self::STDOUT], array('pipe', 'w'));
        } else {
            $descriptors = array(
                array('pipe', 'r'), // stdin
                array('pipe', 'w'), // stdout
                array('pipe', 'w'), // stderr
            );

            if ($this->enhanceSigchildCompatibility && $this->isSigchildEnabled()) {
                // last exit code is output on the fourth pipe and caught to work around --enable-sigchild
                $descriptors = array_merge($descriptors, array(array('pipe', 'w')));

                $this->commandline = '('.$this->commandline.') 3>/dev/null; code=$?; echo $code >&3; exit $code';
            }
        }

        $commandline = $this->commandline;

        if (defined('PHP_WINDOWS_VERSION_BUILD') && $this->enhanceWindowsCompatibility) {
            $commandline = 'cmd /V:ON /E:ON /C "'.$commandline.'"';
            if (!isset($this->options['bypass_shell'])) {
                $this->options['bypass_shell'] = true;
            }
        }

        $this->process = proc_open($commandline, $descriptors, $this->pipes, $this->cwd, $this->env, $this->options);

        if (!is_resource($this->process)) {
            throw new \RuntimeException('Unable to launch a new process.');
        }
        $this->status = self::STATUS_STARTED;

        foreach ($this->pipes as $pipe) {
            stream_set_blocking($pipe, false);
        }

        if (null === $this->stdin) {
            fclose($this->pipes[0]);
            unset($this->pipes[0]);

            return;
        }

        $writePipes = array($this->pipes[0]);
        unset($this->pipes[0]);
        $stdinLen = strlen($this->stdin);
        $stdinOffset = 0;

        while ($writePipes) {
            if (defined('PHP_WINDOWS_VERSION_BUILD')) {
                $this->processFileHandles($callback);
            }

            $r = $this->pipes;
            $w = $writePipes;
            $e = null;

            $n = @stream_select($r, $w, $e, 0, ceil(static::TIMEOUT_PRECISION * 1E6));

            if (false === $n) {
                break;
            }
            if ($n === 0) {
                proc_terminate($this->process);

                throw new \RuntimeException('The process timed out.');
            }

            if ($w) {
                $written = fwrite($writePipes[0], (binary) substr($this->stdin, $stdinOffset), 8192);
                if (false !== $written) {
                    $stdinOffset += $written;
                }
                if ($stdinOffset >= $stdinLen) {
                    fclose($writePipes[0]);
                    $writePipes = null;
                }
            }

            foreach ($r as $pipe) {
                $type = array_search($pipe, $this->pipes);
                $data = fread($pipe, 8192);
                if (strlen($data) > 0) {
                    call_user_func($callback, $type == 1 ? self::OUT : self::ERR, $data);
                }
                if (false === $data || feof($pipe)) {
                    fclose($pipe);
                    unset($this->pipes[$type]);
                }
            }

            $this->checkTimeout();
        }

        $this->updateStatus();
    }

    /**
     * Waits for the process to terminate.
     *
     * The callback receives the type of output (out or err) and some bytes
     * from the output in real-time while writing the standard input to the process.
     * It allows to have feedback from the independent process during execution.
     *
     * @param callback|null $callback A valid PHP callback
     *
     * @return integer The exitcode of the process
     *
     * @throws \RuntimeException When process timed out
     * @throws \RuntimeException When process stopped after receiving signal
     */
    public function wait($callback = null)
    {
        $this->updateStatus();
        $callback = $this->buildCallback($callback);
        while ($this->pipes || (defined('PHP_WINDOWS_VERSION_BUILD') && $this->fileHandles)) {
            if (defined('PHP_WINDOWS_VERSION_BUILD') && $this->fileHandles) {
                $this->processFileHandles($callback, !$this->pipes);
            }
            $this->checkTimeout();

            if ($this->pipes) {
                $r = $this->pipes;
                $w = null;
                $e = null;

                // let's have a look if something changed in streams
                if (false === $n = @stream_select($r, $w, $e, 0, ceil(static::TIMEOUT_PRECISION * 1E6))) {
                    $lastError = error_get_last();

                    // stream_select returns false when the `select` system call is interrupted by an incoming signal
                    if (isset($lastError['message']) && false === stripos($lastError['message'], 'interrupted system call')) {
                        $this->pipes = array();
                    }

                    continue;
                }


                // nothing has changed
                if (0 === $n) {
                    continue;
                }

                foreach ($r as $pipe) {
                    $type = array_search($pipe, $this->pipes);
                    $data = fread($pipe, 8192);

                    if (strlen($data) > 0) {
                        // last exit code is output and caught to work around --enable-sigchild
                        if (3 == $type) {
                            $this->fallbackExitcode = (int) $data;
                        } else {
                            call_user_func($callback, $type == 1 ? self::OUT : self::ERR, $data);
                        }
                    }
                    if (false === $data || feof($pipe)) {
                        fclose($pipe);
                        unset($this->pipes[$type]);
                    }
                }
            }
        }
        $this->updateStatus();
        if ($this->processInformation['signaled']) {
            if ($this->isSigchildEnabled()) {
                throw new RuntimeException('The process has been signaled.');
            }
            throw new RuntimeException(sprintf('The process has been signaled with signal "%s".', $this->processInformation['termsig']));
        }

        $time = 0;
        while ($this->isRunning() && $time < 1000000) {
            $time += 1000;
            usleep(1000);
        }

        $exitcode = proc_close($this->process);

        if ($this->processInformation['signaled']) {
            if ($this->isSigchildEnabled()) {
                throw new RuntimeException('The process has been signaled.');
            }
            throw new RuntimeException(sprintf('The process has been signaled with signal "%s".', $this->processInformation['termsig']));
        }

        $this->exitcode = $this->processInformation['running'] ? $exitcode : $this->processInformation['exitcode'];

        if (-1 == $this->exitcode && null !== $this->fallbackExitcode) {
            $this->exitcode = $this->fallbackExitcode;
        }

        return $this->exitcode;
    }

    /**
     * Returns the current output of the process (STDOUT).
     *
     * @return string The process output
     *
     * @api
     */
    public function getOutput()
    {
        $this->updateOutput();

        return $this->stdout;
    }

    /**
     * Returns the current error output of the process (STDERR).
     *
     * @return string The process error output
     *
     * @api
     */
    public function getErrorOutput()
    {
        $this->updateErrorOutput();

        return $this->stderr;
    }

    /**
     * Returns the exit code returned by the process.
     *
     * @return integer The exit status code
     *
     * @throws RuntimeException In case --enable-sigchild is activated and the sigchild compatibility mode is disabled
     *
     * @api
     */
    public function getExitCode()
    {
        if ($this->isSigchildEnabled() && !$this->enhanceSigchildCompatibility) {
            throw new RuntimeException('This PHP has been compiled with --enable-sigchild. You must use setEnhanceSigchildCompatibility() to use this method');
        }

        $this->updateStatus();

        return $this->exitcode;
    }

    /**
     * Returns a string representation for the exit code returned by the process.
     *
     * This method relies on the Unix exit code status standardization
     * and might not be relevant for other operating systems.
     *
     * @return string A string representation for the exit status code
     *
     * @see http://tldp.org/LDP/abs/html/exitcodes.html
     * @see http://en.wikipedia.org/wiki/Unix_signal
     */
    public function getExitCodeText()
    {
        $exitcode = $this->getExitCode();

        return isset(self::$exitCodes[$exitcode]) ? self::$exitCodes[$exitcode] : 'Unknown error';
    }

    /**
     * Checks if the process ended successfully.
     *
     * @return Boolean true if the process ended successfully, false otherwise
     *
     * @api
     */
    public function isSuccessful()
    {
        return 0 == $this->getExitCode();
    }

    /**
     * Returns true if the child process has been terminated by an uncaught signal.
     *
     * It always returns false on Windows.
     *
     * @return Boolean
     *
     * @throws RuntimeException In case --enable-sigchild is activated
     *
     * @api
     */
    public function hasBeenSignaled()
    {
        if ($this->isSigchildEnabled()) {
            throw new RuntimeException('This PHP has been compiled with --enable-sigchild. Term signal can not be retrieved');
        }

        $this->updateStatus();

        return $this->processInformation['signaled'];
    }

    /**
     * Returns the number of the signal that caused the child process to terminate its execution.
     *
     * It is only meaningful if hasBeenSignaled() returns true.
     *
     * @return integer
     *
     * @throws RuntimeException In case --enable-sigchild is activated
     *
     * @api
     */
    public function getTermSignal()
    {
        if ($this->isSigchildEnabled()) {
            throw new RuntimeException('This PHP has been compiled with --enable-sigchild. Term signal can not be retrieved');
        }

        $this->updateStatus();

        return $this->processInformation['termsig'];
    }

    /**
     * Returns true if the child process has been stopped by a signal.
     *
     * It always returns false on Windows.
     *
     * @return Boolean
     *
     * @api
     */
    public function hasBeenStopped()
    {
        $this->updateStatus();

        return $this->processInformation['stopped'];
    }

    /**
     * Returns the number of the signal that caused the child process to stop its execution.
     *
     * It is only meaningful if hasBeenStopped() returns true.
     *
     * @return integer
     *
     * @api
     */
    public function getStopSignal()
    {
        $this->updateStatus();

        return $this->processInformation['stopsig'];
    }

    /**
     * Checks if the process is currently running.
     *
     * @return Boolean true if the process is currently running, false otherwise
     */
    public function isRunning()
    {
        if (self::STATUS_STARTED !== $this->status) {
            return false;
        }

        $this->updateStatus();

        return $this->processInformation['running'];
    }

    /**
     * Stops the process.
     *
     * @param integer|float $timeout The timeout in seconds
     *
     * @return integer The exit-code of the process
     */
    public function stop($timeout=10)
    {
        $timeoutMicro = (int) $timeout*1E6;
        if ($this->isRunning()) {
            proc_terminate($this->process);
            $time = 0;
            while (1 == $this->isRunning() && $time < $timeoutMicro) {
                $time += 1000;
                usleep(1000);
            }

            if (!defined('PHP_WINDOWS_VERSION_BUILD') && $this->isRunning()) {
                proc_terminate($this->process, SIGKILL);
            }

            foreach ($this->pipes as $pipe) {
                fclose($pipe);
            }
            $this->pipes = array();

            $exitcode = proc_close($this->process);
            $this->exitcode = -1 === $this->processInformation['exitcode'] ? $exitcode : $this->processInformation['exitcode'];

            if (defined('PHP_WINDOWS_VERSION_BUILD')) {
                foreach ($this->fileHandles as $fileHandle) {
                    fclose($fileHandle);
                }
                $this->fileHandles = array();
            }
        }
        $this->status = self::STATUS_TERMINATED;

        return $this->exitcode;
    }

    /**
     * Adds a line to the STDOUT stream.
     *
     * @param string $line The line to append
     */
    public function addOutput($line)
    {
        $this->stdout .= $line;
    }

    /**
     * Adds a line to the STDERR stream.
     *
     * @param string $line The line to append
     */
    public function addErrorOutput($line)
    {
        $this->stderr .= $line;
    }

    /**
     * Gets the command line to be executed.
     *
     * @return string The command to execute
     */
    public function getCommandLine()
    {
        return $this->commandline;
    }

    /**
     * Sets the command line to be executed.
     *
     * @param string $commandline The command to execute
     */
    public function setCommandLine($commandline)
    {
        $this->commandline = $commandline;
    }

    /**
     * Gets the process timeout.
     *
     * @return integer|null The timeout in seconds or null if it's disabled
     */
    public function getTimeout()
    {
        return $this->timeout;
    }

    /**
     * Sets the process timeout.
     *
     * To disable the timeout, set this value to null.
     *
     * @param float|null $timeout The timeout in seconds
     *
     * @throws \InvalidArgumentException if the timeout is negative
     */
    public function setTimeout($timeout)
    {
        if (null === $timeout) {
            $this->timeout = null;

            return;
        }

        $timeout = (float) $timeout;

        if ($timeout < 0) {
            throw new \InvalidArgumentException('The timeout value must be a valid positive integer or float number.');
        }

        $this->timeout = $timeout;
    }

    /**
     * Gets the working directory.
     *
     * @return string The current working directory
     */
    public function getWorkingDirectory()
    {
        // This is for BC only
        if (null === $this->cwd) {
            // getcwd() will return false if any one of the parent directories does not have
            // the readable or search mode set, even if the current directory does
            return getcwd() ?: null;
        }

        return $this->cwd;
    }

    /**
     * Sets the current working directory.
     *
     * @param string $cwd The new working directory
     */
    public function setWorkingDirectory($cwd)
    {
        $this->cwd = $cwd;
    }

    /**
     * Gets the environment variables.
     *
     * @return array The current environment variables
     */
    public function getEnv()
    {
        return $this->env;
    }

    /**
     * Sets the environment variables.
     *
     * @param array $env The new environment variables
     */
    public function setEnv(array $env)
    {
        $this->env = $env;
    }

    /**
     * Gets the contents of STDIN.
     *
     * @return string The current contents
     */
    public function getStdin()
    {
        return $this->stdin;
    }

    /**
     * Sets the contents of STDIN.
     *
     * @param string $stdin The new contents
     */
    public function setStdin($stdin)
    {
        $this->stdin = $stdin;
    }

    /**
     * Gets the options for proc_open.
     *
     * @return array The current options
     */
    public function getOptions()
    {
        return $this->options;
    }

    /**
     * Sets the options for proc_open.
     *
     * @param array $options The new options
     */
    public function setOptions(array $options)
    {
        $this->options = $options;
    }

    /**
     * Gets whether or not Windows compatibility is enabled
     *
     * This is true by default.
     *
     * @return Boolean
     */
    public function getEnhanceWindowsCompatibility()
    {
        return $this->enhanceWindowsCompatibility;
    }

    /**
     * Sets whether or not Windows compatibility is enabled
     *
     * @param Boolean $enhance
     */
    public function setEnhanceWindowsCompatibility($enhance)
    {
        $this->enhanceWindowsCompatibility = (Boolean) $enhance;
    }

    /**
     * Return whether sigchild compatibility mode is activated or not
     *
     * @return Boolean
     */
    public function getEnhanceSigchildCompatibility()
    {
        return $this->enhanceSigchildCompatibility;
    }

    /**
     * Activate sigchild compatibility mode
     *
     * Sigchild compatibility mode is required to get the exit code and
     * determine the success of a process when PHP has been compiled with
     * the --enable-sigchild option
     *
     * @param Boolean $enhance
     */
    public function setEnhanceSigchildCompatibility($enhance)
    {
        $this->enhanceSigchildCompatibility = (Boolean) $enhance;
    }

    /**
     * Performs a check between the timeout definition and the time the process
     * started
     *
     * In case you run a background process (with the start method), you should
     * trigger this method regularly to ensure the process timeout
     *
     * @throws RuntimeException In case the timeout was reached
     */
    public function checkTimeout()
    {
        if (0 < $this->timeout && $this->timeout < microtime(true) - $this->starttime) {
            $this->stop(0);

            throw new RuntimeException('The process timed-out.');
        }
    }

    /**
     * Builds up the callback used by wait().
     *
     * The callbacks adds all occurred output to the specific buffer and calls
     * the user callback (if present) with the received output.
     *
     * @param callback|null $callback The user defined PHP callback
     *
     * @return callback A PHP callable
     */
    protected function buildCallback($callback)
    {
        $that = $this;
        $out = self::OUT;
        $err = self::ERR;
        $callback = function ($type, $data) use ($that, $callback, $out, $err) {
            if ($out == $type) {
                $that->addOutput($data);
            } else {
                $that->addErrorOutput($data);
            }

            if (null !== $callback) {
                call_user_func($callback, $type, $data);
            }
        };

        return $callback;
    }

    /**
     * Updates the status of the process.
     */
    protected function updateStatus()
    {
        if (self::STATUS_STARTED !== $this->status) {
            return;
        }

        $this->processInformation = proc_get_status($this->process);
        if (!$this->processInformation['running']) {
            $this->status = self::STATUS_TERMINATED;
            if (-1 !== $this->processInformation['exitcode']) {
                $this->exitcode = $this->processInformation['exitcode'];
            }
        }
    }

    /**
     * Updates the current error output of the process (STDERR).
     */
    protected function updateErrorOutput()
    {
        if (isset($this->pipes[self::STDERR]) && is_resource($this->pipes[self::STDERR])) {
            $this->addErrorOutput(stream_get_contents($this->pipes[self::STDERR]));
        }
    }

    /**
     * Updates the current output of the process (STDOUT).
     */
    protected function updateOutput()
    {
        if (defined('PHP_WINDOWS_VERSION_BUILD') && isset($this->fileHandles[self::STDOUT]) && is_resource($this->fileHandles[self::STDOUT])) {
            fseek($this->fileHandles[self::STDOUT], $this->readBytes[self::STDOUT]);
            $this->addOutput(stream_get_contents($this->fileHandles[self::STDOUT]));
        } elseif (isset($this->pipes[self::STDOUT]) && is_resource($this->pipes[self::STDOUT])) {
            $this->addOutput(stream_get_contents($this->pipes[self::STDOUT]));
        }
    }

    /**
     * Return whether PHP has been compiled with the '--enable-sigchild' option or not
     *
     * @return Boolean
     */
    protected function isSigchildEnabled()
    {
        if (null !== self::$sigchild) {
            return self::$sigchild;
        }

        ob_start();
        phpinfo(INFO_GENERAL);

        return self::$sigchild = false !== strpos(ob_get_clean(), '--enable-sigchild');
    }

    /**
     * Handles the windows file handles fallbacks
     *
     * @param mixed $callback A valid PHP callback
     * @param Boolean $closeEmptyHandles if true, handles that are empty will be assumed closed
     */
    private function processFileHandles($callback, $closeEmptyHandles = false)
    {
        $fh = $this->fileHandles;
        foreach ($fh as $type => $fileHandle) {
            fseek($fileHandle, $this->readBytes[$type]);
            $data = fread($fileHandle, 8192);
            if (strlen($data) > 0) {
                $this->readBytes[$type] += strlen($data);
                call_user_func($callback, $type == 1 ? self::OUT : self::ERR, $data);
            }
            if (false === $data || ($closeEmptyHandles && '' === $data && feof($fileHandle))) {
                fclose($fileHandle);
                unset($this->fileHandles[$type]);
            }
        }
    }
}