Refactor contexts and exiting

examples/fork.php

@@ -1,3 +1,4 @@
+#!/usr/bin/env php
 <?php
 require dirname(__DIR__).'/vendor/autoload.php';
 
@@ -6,12 +7,14 @@ use Icicle\Coroutine;
 use Icicle\Loop;
 
 Coroutine\create(function () {
-    $context = ForkContext::create(function () {
+    $context = new ForkContext(function () {
         print "Child sleeping for 4 seconds...\n";
         sleep(4);
 
         print "Child sleeping for 2 seconds...\n";
         sleep(2);
+
+        return 42;
     });
     $context->start();
 
@@ -22,8 +25,7 @@ Coroutine\create(function () {
     });
 
     try {
-        yield $context->join();
+        printf("Child ended with value %d!\n", (yield $context->join()));
-        print "Context done!\n";
     } catch (Exception $e) {
         print "Error from child!\n";
         print $e."\n";

examples/thread.php

@@ -1,3 +1,4 @@
+#!/usr/bin/env php
 <?php
 require dirname(__DIR__).'/vendor/autoload.php';
 
@@ -5,14 +6,15 @@ use Icicle\Concurrent\Threading\ThreadContext;
 use Icicle\Coroutine;
 use Icicle\Loop;
 
+$timer = Loop\periodic(1, function () {
+    print "Demonstrating how alive the parent is.\n";
+});
+
 Coroutine\create(function () {
     // Create a periodic message in the main thread.
-    $timer = Loop\periodic(1, function () {
-        print "Demonstrating how alive the parent is.\n";
-    });
 
     // Create a new child thread that does some blocking stuff.
-    $test = ThreadContext::create(function () {
+    $test = new ThreadContext(function () {
         print "Sleeping for 5 seconds...\n";
         sleep(5);
         return 42;
@@ -21,8 +23,6 @@ Coroutine\create(function () {
     // Run the thread and wait asynchronously for it to finish.
     $test->start();
     printf("Thread ended with value %d!\n", (yield $test->join()));
-})->done(function () {
+})->done([$timer, 'stop']);
-    Loop\stop();
-});
 
 Loop\run();

src/ContextInterface.php

@@ -6,13 +6,6 @@ namespace Icicle\Concurrent;
  */
 interface ContextInterface extends SynchronizableInterface
 {
-    /**
-     * Creates a new context with a given function to run.
-     *
-     * @return ContextInterface A context instance.
-     */
-    public static function create(callable $function);
-
     /**
      * Checks if the context is running.
      *
@@ -31,12 +24,20 @@ interface ContextInterface extends SynchronizableInterface
     public function kill();
 
     /**
-     * Causes the context to immediately panic.
+     * @return \Generator
      *
-     * @param string $message A panic message.
+     * @resolve mixed
-     * @param int    $code    A panic code.
      */
-    public function panic($message = '', $code = 0);
+    public function receive();
+
+    /**
+     * @param mixed $data
+     *
+     * @return \Generator
+     *
+     * @resolve int
+     */
+    public function send($data);
 
     /**
      * Gets a promise that resolves when the context ends and joins with the

src/Exception/PanicError.php

@@ -4,9 +4,9 @@ namespace Icicle\Concurrent\Exception;
 class PanicError extends Error
 {
     /**
-     * @var array Stack trace of the panic.
+     * @var string Stack trace of the panic.
      */
-    private $panicTrace;
+    private $trace;
 
     /**
      * Creates a new panic error.
@@ -15,39 +15,19 @@ class PanicError extends Error
      * @param int    $code    The panic code.
      * @param array  $trace   The panic stack trace.
      */
-    public function __construct($message = '', $code = 0, array $trace = [])
+    public function __construct($message = '', $code = 0, $trace = '')
     {
         parent::__construct($message, $code);
-        $this->panicTrace = $trace;
+        $this->trace = $trace;
     }
 
     /**
      * Gets the stack trace at the point the panic occurred.
      *
-     * @return array
+     * @return string
      */
     public function getPanicTrace()
     {
-        return $this->panicTrace;
+        return $this->trace;
-    }
-
-    /**
-     * Gets the panic stack trace as a string.
-     *
-     * @return string
-     */
-    public function getPanicTraceAsString()
-    {
-        foreach ($this->panicTrace as $id => $scope) {
-            $string .= sprintf("%d# %s(%d): %s%s%s()\n",
-                $id,
-                $scope['file'],
-                $scope['line'],
-                isset($scope['class']) ? $scope['class'] : '',
-                isset($scope['type']) ? $scope['type'] : '',
-                $scope['function']);
-        }
-
-        return $string;
     }
 }

src/Exception/SynchronizationError.php

@@ -0,0 +1,6 @@
+<?php
+namespace Icicle\Concurrent\Exception;
+
+class SynchronizationError extends Error
+{
+}

src/Forking/ForkContext.php

@@ -2,11 +2,14 @@
 namespace Icicle\Concurrent\Forking;
 
 use Icicle\Concurrent\ContextInterface;
-use Icicle\Concurrent\Exception\PanicError;
+use Icicle\Concurrent\Exception\SynchronizationError;
 use Icicle\Concurrent\Sync\Channel;
+use Icicle\Concurrent\Sync\ExitFailure;
+use Icicle\Concurrent\Sync\ExitInterface;
+use Icicle\Concurrent\Sync\ExitSuccess;
 use Icicle\Coroutine\Coroutine;
 use Icicle\Loop;
-use Icicle\Promise\Deferred;
+use Icicle\Promise;
 
 /**
  * Implements a UNIX-compatible context using forked processes.
@@ -16,28 +19,26 @@ class ForkContext extends Synchronized implements ContextInterface
     const MSG_DONE = 1;
     const MSG_ERROR = 2;
 
-    private $parentSocket;
+    /**
-    private $childSocket;
+     * @var \Icicle\Concurrent\Sync\Channel A channel for communicating with the child.
-    private $pid = 0;
+     */
-    private $isChild = false;
+    private $channel;
-    private $deferred;
-    private $function;
 
     /**
-     * Creates a new fork context.
+     * @var int
-     *
-     * @param callable $function The function to run in the context.
      */
-    public static function create(callable $function)
+    private $pid = 0;
+
+    /**
+     * @var callable
+     */
+    private $function;
+
+    public function __construct(callable $function)
     {
-        $instance = new static();
+        parent::__construct();
 
-        $instance->function = $function;
+        $this->function = $function;
-        $instance->deferred = new Deferred(function (\Exception $exception) use ($instance) {
-            $instance->stop();
-        });
-
-        return $instance;
     }
 
     /**
@@ -55,11 +56,6 @@ class ForkContext extends Synchronized implements ContextInterface
      */
     public function isRunning()
     {
-        // If we are the child process, then we must be running, don't you think?
-        if ($this->isChild) {
-            return true;
-        }
-
         return posix_getpgid($this->pid) !== false;
     }
 
@@ -68,37 +64,24 @@ class ForkContext extends Synchronized implements ContextInterface
      */
     public function start()
     {
-        $channels = Channel::create();
+        list($parent, $child) = Channel::createSocketPair();
 
-        $this->parentSocket = $channels[0];
-        $this->childSocket = $channels[1];
-
-        $parentPid = getmypid();
         if (($pid = pcntl_fork()) === -1) {
             throw new \Exception();
         }
 
         // We are the parent inside this block.
         if ($pid !== 0) {
-            $this->pid = $pid;
+            $this->channel = new Channel($parent);
+            fclose($child);
 
-            // Wait for the child process to send us a byte over the socket pair
+            $this->pid = $pid;
-            // to discover immediately when the process has completed.
-            // @TODO error checking, check message type received
-            $receive = new Coroutine($this->parentSocket->receive());
-            $receive->then(function ($data) {
-                $this->deferred->resolve();
-            }, function (\Exception $exception) {
-                $this->deferred->reject($exception);
-            });
 
             return;
         }
 
-        // We are the child, so close the parent socket and initialize child values.
+        $channel = new Channel($child);
-        $this->isChild = true;
+        fclose($parent);
-        $this->pid = getmypid();
-        $this->parentSocket->close();
 
         // We will have a cloned event loop from the parent after forking. The
         // child context by default is synchronous and uses the parent event
@@ -109,9 +92,33 @@ class ForkContext extends Synchronized implements ContextInterface
         Loop\clear();
 
         // Execute the context runnable and send the parent context the result.
-        $this->run();
+        Promise\wait(new Coroutine($this->execute($channel)));
+
+        exit(0);
     }
 
+    /**
+     * @param Channel $channel
+     *
+     * @return \Generator
+     */
+    private function execute(Channel $channel)
+    {
+        try {
+            $function = $this->function;
+            $result = new ExitSuccess(yield $function($channel));
+        } catch (\Exception $exception) {
+            $result = new ExitFailure($exception);
+        }
+
+        yield $channel->send($result);
+
+        $channel->close();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
     public function kill()
     {
         if ($this->isRunning()) {
@@ -125,50 +132,38 @@ class ForkContext extends Synchronized implements ContextInterface
      */
     public function join()
     {
-        if ($this->isChild) {
+        try {
-            throw new \Exception();
+            $response = (yield $this->channel->receive());
-        }
 
-        return $this->deferred->getPromise();
+            if (!$response instanceof ExitInterface) {
+                throw new SynchronizationError('Did not receive an exit status from fork.');
+            }
+
+            yield $response->getResult();
+        } finally {
+            $this->kill();
+        }
     }
 
     /**
      * {@inheritdoc}
      */
-    public function panic($message = '', $code = 0)
+    public function receive()
     {
-        if ($this->isThread) {
+        $data = (yield $this->channel->receive());
-            throw new PanicError($message, $code);
+
+        if ($data instanceof ExitInterface) {
+            throw new SynchronizationError(sprintf('Fork exited with result of type: %s', $data->getResult()));
         }
+
+        yield $data;
     }
 
-    public function __destruct()
+    /**
+     * {@inheritdoc}
+     */
+    public function send($data)
     {
-        parent::__destruct();
+        return $this->channel->send($data);
-
-        // The parent process outlives the child process, so don't destroy the
-        // semaphore until the parent exits.
-        if (!$this->isChild) {
-            //$this->semaphore->destroy();
-        }
-    }
-
-    private function run()
-    {
-        try {
-            $generator = call_user_func($this->function);
-            if ($generator instanceof \Generator) {
-                $coroutine = new Coroutine($generator);
-            }
-            Loop\run();
-        /*} catch (\Exception $exception) {
-            fwrite($this->childSocket, chr(self::MSG_ERROR));
-            $serialized = serialize($exception);
-            $length = strlen($serialized);
-            fwrite($this->childSocket, pack('S', $length).$serialized);*/
-        } finally {
-            $this->childSocket->close();
-            exit(0);
-        }
     }
 }

src/Sync/Channel.php

@@ -21,14 +21,19 @@ class Channel
     const HEADER_LENGTH = 5;
 
     /**
-     * @var DuplexStream An asynchronous socket stream.
+     * @var \Icicle\Socket\Stream\DuplexStream An asynchronous socket stream.
      */
-    private $socket;
+    private $stream;
 
     /**
-     * @var resource A synchronous socket stream.
+     * Creates a new channel instance.
+     *
+     * @param resource $socket
      */
-    private $socketResource;
+    public function __construct($socket)
+    {
+        $this->stream = new DuplexStream($socket);
+    }
 
     /**
      * Creates a new channel and returns a pair of connections.
@@ -37,9 +42,11 @@ class Channel
      * channel. Each connection is a peer and interacts with the other, even
      * across threads or processes.
      *
-     * @return [Channel, Channel] A pair of channels.
+     * @return resource[] Pair of socket resources.
+     *
+     * @throws \Icicle\Concurrent\Exception\ChannelException
      */
-    public static function create()
+    public static function createSocketPair()
     {
         // Create a socket pair.
         if (($sockets = stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, STREAM_IPPROTO_IP)) === false) {
@@ -54,7 +61,7 @@ class Channel
      *
      * @param mixed $data The data to send.
      *
-     * @return Generator
+     * @return \Generator
      */
     public function send($data)
     {
@@ -68,15 +75,15 @@ class Channel
         $length = strlen($serialized);
 
         $header = pack('CL', self::MESSAGE_DATA, $length);
-        $message = $header.$serialized;
+        $message = $header . $serialized;
 
-        yield $this->getSocket()->write($message);
+        yield $this->stream->write($message);
     }
 
     /**
      * Waits asynchronously for a message from the peer.
      *
-     * @return Generator
+     * @return \Generator
      */
     public function receive()
     {
@@ -84,7 +91,7 @@ class Channel
         $buffer = '';
         $length = self::HEADER_LENGTH;
         do {
-            $buffer .= (yield $this->getSocket()->read($length));
+            $buffer .= (yield $this->stream->read($length));
         } while (($length -= strlen($buffer)) > 0);
 
         $header = unpack('Ctype/Llength', $buffer);
@@ -92,7 +99,7 @@ class Channel
         // If the message type is MESSAGE_CLOSE, the peer was closed and the channel
         // is done.
         if ($header['type'] === self::MESSAGE_CLOSE) {
-            $this->getSocket()->close();
+            $this->stream->close();
             yield null;
             return;
         }
@@ -102,7 +109,7 @@ class Channel
             $buffer = '';
             $length = $header['length'];
             do {
-                $buffer .= (yield $this->getSocket()->read($length));
+                $buffer .= (yield $this->stream->read($length));
             } while (($length -= strlen($buffer)) > 0);
 
             // Attempt to unserialize the received data.
@@ -120,14 +127,14 @@ class Channel
      * This method closes the connection to the peer and sends a message to the
      * peer notifying that the connection has been closed.
      *
-     * @return PromiseInterface
+     * @return \Icicle\Promise\PromiseInterface
      */
     public function close()
     {
         // Create a message with just a DONE header and zero data.
         $message = pack('Cx4', self::MESSAGE_CLOSE);
 
-        return $this->getSocket()->end($message);
+        return $this->stream->end($message);
     }
 
     /**
@@ -137,30 +144,6 @@ class Channel
      */
     public function isOpen()
     {
-        return $this->getSocket()->isOpen();
+        return $this->stream->isOpen();
-    }
-
-    /**
-     * Creates a new channel instance.
-     *
-     * @param resource $socketResource
-     */
-    public function __construct($socketResource)
-    {
-        $this->socketResource = $socketResource;
-    }
-
-    /**
-     * Gets an asynchronous socket instance.
-     *
-     * @return DuplexStream
-     */
-    private function getSocket()
-    {
-        if ($this->socket === null) {
-            $this->socket = new DuplexStream($this->socketResource);
-        }
-
-        return $this->socket;
     }
 }

src/Sync/ExitFailure.php

@@ -0,0 +1,47 @@
+<?php
+namespace Icicle\Concurrent\Sync;
+
+use Icicle\Concurrent\Exception\PanicError;
+
+class ExitFailure implements ExitInterface
+{
+    /**
+     * @var string
+     */
+    private $type;
+
+    /**
+     * @var string
+     */
+    private $message;
+
+    /**
+     * @var int
+     */
+    private $code;
+
+    /**
+     * @var array
+     */
+    private $trace;
+
+    public function __construct(\Exception $exception)
+    {
+        $this->type = get_class($exception);
+        $this->message = $exception->getMessage();
+        $this->code = $exception->getCode();
+        $this->trace = $exception->getTraceAsString();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getResult()
+    {
+        throw new PanicError(
+            sprintf('Uncaught exception in context of type "%s" with message "%s"', $this->type, $this->message),
+            $this->code,
+            $this->trace
+        );
+    }
+}

src/Sync/ExitInterface.php

@@ -0,0 +1,12 @@
+<?php
+namespace Icicle\Concurrent\Sync;
+
+interface ExitInterface
+{
+    /**
+     * @return mixed Return value of the callable given to the execution context.
+     *
+     * @throws \Icicle\Concurrent\Exception\PanicError If the context exited with an uncaught exception.
+     */
+    public function getResult();
+}

src/Sync/ExitSuccess.php

@@ -0,0 +1,23 @@
+<?php
+namespace Icicle\Concurrent\Sync;
+
+class ExitSuccess implements ExitInterface
+{
+    /**
+     * @var mixed
+     */
+    private $result;
+
+    public function __construct($result)
+    {
+        $this->result = $result;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getResult()
+    {
+        return $this->result;
+    }
+}

src/Threading/Thread.php

@@ -2,8 +2,10 @@
 namespace Icicle\Concurrent\Threading;
 
 use Icicle\Concurrent\Sync\Channel;
+use Icicle\Concurrent\Sync\ExitFailure;
+use Icicle\Concurrent\Sync\ExitSuccess;
 use Icicle\Coroutine\Coroutine;
-use Icicle\Loop;
+use Icicle\Promise;
 
 /**
  * An internal thread that executes a given function concurrently.
@@ -11,12 +13,7 @@ use Icicle\Loop;
 class Thread extends \Thread
 {
     /**
-     * @var ThreadContext An instance of the context local to this thread.
+     * @var string Path to an autoloader to include.
-     */
-    public $context;
-
-    /**
-     * @var string|null Path to an autoloader to include.
      */
     public $autoloaderPath;
 
@@ -25,10 +22,12 @@ class Thread extends \Thread
      */
     private $function;
 
-    public $prepared = false;
+    private $prepared = false;
-    public $initialized = false;
+    private $initialized = false;
 
-    private $channel;
+    /**
+     * @var resource
+     */
     private $socket;
 
     /**
@@ -36,9 +35,9 @@ class Thread extends \Thread
      *
      * @param callable $function The function to execute in the thread.
      */
-    public function __construct(callable $function)
+    public function __construct(callable $function, $autoloaderPath = '')
     {
-        $this->context = new ThreadContext($this);
+        $this->autoloaderPath = $autoloaderPath;
         $this->function = $function;
     }
 
@@ -53,6 +52,16 @@ class Thread extends \Thread
         $this->initialized = true;
     }
 
+    /**
+     * Determines if the thread has successfully been prepared.
+     *
+     * @return bool
+     */
+    public function isPrepared()
+    {
+        return $this->prepared;
+    }
+
     /**
      * Runs the thread code and the initialized function.
      */
@@ -68,13 +77,10 @@ class Thread extends \Thread
         // don't do this first, objects we receive from other threads will just
         // be garbage data and unserializable values (like resources) will be
         // lost. This happens even with thread-safe objects.
-        if (file_exists($this->autoloaderPath)) {
+        if ('' !== $this->autoloaderPath && file_exists($this->autoloaderPath)) {
             require $this->autoloaderPath;
         }
 
-        // Initialize the thread-local global event loop.
-        Loop\loop();
-
         // Register a shutdown handler to deal with errors smoothly.
         //register_shutdown_function([$this, 'handleShutdown']);
 
@@ -94,73 +100,27 @@ class Thread extends \Thread
         // At this point, the thread environment has been prepared, and the
         // parent has finished injecting values into our memory, so begin using
         // the channel.
-        $this->channel = new LocalObject(new Channel($this->socket));
+        $channel = new Channel($this->socket);
 
-        // Now that everything is finally ready, invoke the function, closure,
+        Promise\wait(new Coroutine($this->execute($channel)));
-        // or coroutine passed in from the user.
+    }
+
+    /**
+     * @param Channel $channel
+     *
+     * @return \Generator
+     */
+    private function execute(Channel $channel)
+    {
         try {
-            if ($this->function instanceof \Closure) {
+            $function = $this->function;
-                $generator = $this->function->bindTo($this->context)->__invoke();
+            $result = new ExitSuccess(yield $function($channel));
-            } else {
-                $generator = call_user_func($this->function);
-            }
-
-            if ($generator instanceof \Generator) {
-                $coroutine = new Coroutine($generator);
-            } else {
-                $returnValue = $generator;
-            }
-
-            // Send the return value back to the parent thread.
-            $response = [
-                'ok' => true,
-                'value' => $returnValue,
-            ];
-            new Coroutine($this->channel->deref()->send($response));
-
-            Loop\run();
         } catch (\Exception $exception) {
-            // If normal execution failed and caused an error, catch it and send
+            $result = new ExitFailure($exception);
-            // it to the parent context so the error can bubble up.
-            $response = [
-                'ok' => false,
-                'panic' => [
-                    'message' => $exception->getMessage(),
-                    'code' => $exception->getCode(),
-                    'trace' => array_map([$this, 'removeTraceArgs'], $exception->getTrace()),
-                ],
-            ];
-
-            new Coroutine($this->channel->deref()->send($response));
-        } finally {
-            $this->channel->deref()->close();
         }
 
-        // We don't really need to do this, but let's be explicit about freeing
+        yield $channel->send($result);
-        // our resources.
-        $this->channel->free();
-    }
 
-    public function handleShutdown()
+        $channel->close();
-    {
-        if ($error = error_get_last()) {
-            $panic = [
-                'message' => $error['message'],
-                'code' => 0,
-                'trace' => array_map([$this, 'removeTraceArgs'], debug_backtrace()),
-            ];
-
-            $this->sendMessage(self::MSG_ERROR);
-            $serialized = serialize($panic);
-            $length = strlen($serialized);
-            fwrite($this->socket, pack('S', $length).$serialized);
-            fclose($this->socket);
-        }
-    }
-
-    public function removeTraceArgs($trace)
-    {
-        unset($trace['args']);
-        return $trace;
     }
 }

src/Threading/ThreadContext.php

@@ -2,8 +2,9 @@
 namespace Icicle\Concurrent\Threading;
 
 use Icicle\Concurrent\ContextInterface;
-use Icicle\Concurrent\Exception\PanicError;
+use Icicle\Concurrent\Exception\SynchronizationError;
 use Icicle\Concurrent\Sync\Channel;
+use Icicle\Concurrent\Sync\ExitInterface;
 use Icicle\Promise;
 
 /**
@@ -16,45 +17,23 @@ use Icicle\Promise;
 class ThreadContext implements ContextInterface
 {
     /**
-     * @var Thread A thread instance.
+     * @var \Icicle\Concurrent\Threading\Thread A thread instance.
      */
-    public $thread;
+    private $thread;
 
     /**
-     * @var Channel A channel for communicating with the thread.
+     * @var \Icicle\Concurrent\Sync\Channel A channel for communicating with the thread.
      */
     private $channel;
 
-    /**
-     * @var bool Indicates if this context instance belongs to the thread.
-     */
-    private $isThread = true;
-
-    /**
-     * {@inheritdoc}
-     */
-    public static function create(callable $function)
-    {
-        $thread = new Thread($function);
-        $thread->autoloaderPath = static::getComposerAutoloader();
-
-        $context = new static($thread);
-        $context->isThread = false;
-        $context->deferredJoin = new Promise\Deferred(function () use ($context) {
-            $context->kill();
-        });
-
-        return $context;
-    }
-
     /**
      * Creates a new thread context from a thread.
      *
-     * @param Thread $thread The thread object.
+     * @param callable $function
      */
-    public function __construct(Thread $thread)
+    public function __construct(callable $function)
     {
-        $this->thread = $thread;
+        $this->thread = new Thread($function, $this->getComposerAutoloader());
     }
 
     /**
@@ -70,20 +49,20 @@ class ThreadContext implements ContextInterface
      */
     public function start()
     {
-        $channels = Channel::create();
+        list($threadSocket, $parentSocket) = Channel::createSocketPair();
-        $this->channel = new Channel($channels[1]);
+        $this->channel = new Channel($parentSocket);
 
         // Start the thread first. The thread will prepare the autoloader and
         // the event loop, and then notify us when the thread environment is
         // ready. If we don't do this first, objects will break when passed
         // to the thread, since the classes are not yet defined.
-        $this->thread->start(PTHREADS_INHERIT_INI | PTHREADS_ALLOW_GLOBALS);
+        $this->thread->start(PTHREADS_INHERIT_INI);
 
         // The thread must prepare itself first, so wait until the thread has
         // done so. We need to unlock ourselves while waiting to prevent
         // deadlocks if we somehow acquired the lock before the thread did.
         $this->thread->synchronized(function () {
-            if (!$this->thread->prepared) {
+            if (!$this->thread->isPrepared()) {
                 $this->thread->wait();
             }
         });
@@ -91,8 +70,8 @@ class ThreadContext implements ContextInterface
         // At this stage, the thread environment has been prepared, and we kept
         // the lock from above, so initialize the thread with the necessary
         // values to be copied over.
-        $this->thread->synchronized(function () use ($channels) {
+        $this->thread->synchronized(function () use ($threadSocket) {
-            $this->thread->init($channels[0]);
+            $this->thread->init($threadSocket);
             $this->thread->notify();
         });
     }
@@ -105,35 +84,23 @@ class ThreadContext implements ContextInterface
         $this->thread->kill();
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function panic($message = '', $code = 0)
-    {
-        if ($this->isThread) {
-            throw new PanicError($message, $code);
-        } else {
-            $this->kill();
-        }
-    }
-
     /**
      * {@inheritdoc}
      */
     public function join()
     {
-        // Get an array of completion data from the thread when it finishes.
+        try {
-        $response = (yield $this->channel->receive());
+            $response = (yield $this->channel->receive());
 
-        // If the status is not OK, bubble the problem up.
+            if (!$response instanceof ExitInterface) {
-        if (!$response['ok']) {
+                throw new SynchronizationError('Did not receive an exit status from thread.');
-            throw new PanicError($response['panic']['message'], $response['panic']['code'], $response['panic']['trace']);
+            }
+
+            yield $response->getResult();
+        } finally {
+            $this->channel->close();
+            $this->thread->join();
         }
-
-        $this->channel->close();
-        $this->thread->join();
-
-        yield $response['value'];
     }
 
     /**
@@ -168,32 +135,43 @@ class ThreadContext implements ContextInterface
         return $returnValue;
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function receive()
+    {
+        $data = (yield $this->channel->receive());
+
+        if ($data instanceof ExitInterface) {
+            throw new SynchronizationError(sprintf('Thread exited with result of type: %s', $data->getResult()));
+        }
+
+        yield $data;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function send($data)
+    {
+        return $this->channel->send($data);
+    }
+
     /**
      * Gets the full path to the Composer autoloader.
      *
      * If no Composer autoloader is being used, `null` is returned.
      *
-     * @return \Composer\Autoload\ClassLoader|null
+     * @return string
      */
-    private static function getComposerAutoloader()
+    private function getComposerAutoloader()
     {
         foreach (get_included_files() as $path) {
-            if (strpos($path, 'vendor/autoload.php') !== false) {
+            if (preg_match('/vendor\/autoload.php$/i', $path)) {
-                $source = file_get_contents($path);
+                return $path;
-                if (strpos($source, '@generated by Composer') !== false) {
-                    return $path;
-                }
             }
         }
 
-        // Find the Composer autoloader initializer class, and use it to fetch
+        return '';
-        // the autoloader instance.
-        /*foreach (get_declared_classes() as $name) {
-        if (strpos($name, 'ComposerAutoloaderInit') === 0) {
-        return $name::getLoader();
-        }
-        }*/
-
-        return;
     }
 }