Add better socket checking and error handling

Also update send() to return a generator.

src/Sync/Channel.php

@@ -8,6 +8,10 @@ use Icicle\Socket\Stream\DuplexStream;
  * An asynchronous channel for sending data between threads and processes.
  *
  * Supports full duplex read and write.
+ *
+ * Note that the sockets are lazily bound to enable temporary thread safety. A
+ * channel object can be safely transferred between threads up until the point
+ * that the channel is used.
  */
 class Channel
 {
@@ -51,28 +55,38 @@ class Channel
      *
      * @param mixed $data The data to send.
      *
-     * @return PromiseInterface
+     * @return Generator
      */
     public function send($data)
     {
-        $serialized = serialize($data);
+        // Serialize the data to send into the channel.
+        try {
+            $serialized = serialize($data);
+        } catch (\Exception $exception) {
+            throw new ChannelException('The given data is not sendable because it is not serializable.',
+                0, $exception);
+        }
         $length = strlen($serialized);
 
         $header = pack('CL', self::MESSAGE_DATA, $length);
         $message = $header.$serialized;
 
-        return $this->getSocket()->write($message);
+        yield $this->getSocket()->write($message);
     }
 
     /**
      * Waits asynchronously for a message from the peer.
      *
-     * @return PromiseInterface
+     * @return Generator
      */
     public function receive()
     {
         // Read the message header first and extract its contents.
-        $header = unpack('Ctype/Llength', (yield $this->getSocket()->read(5)));
+        $buffer = '';
+        while (strlen($buffer) < 5) {
+            $buffer .= (yield $this->getSocket()->read(5));
+        }
+        $header = unpack('Ctype/Llength', $buffer);
 
         // If the message type is MESSAGE_DONE, the peer was closed and the channel
         // is done.
@@ -83,8 +97,17 @@ class Channel
 
         // Read the serialized data from the socket.
         if ($header['type'] === self::MESSAGE_DATA) {
-            $serialized = (yield $this->socket->read($header['length']));
-            $data = unserialize($serialized);
+            $buffer = '';
+            while (strlen($buffer) < $header['length']) {
+                $buffer .= (yield $this->socket->read($header['length']));
+            }
+
+            // Attempt to unserialize the received data.
+            try {
+                $data = unserialize($buffer);
+            } catch (\Exception $exception) {
+                throw new ChannelException('Received corrupt data from peer.', 0, $exception);
+            }
 
             yield $data;
             return;

tests/Sync/ChannelTest.php

@@ -31,11 +31,11 @@ class ChannelTest extends \PHPUnit_Framework_TestCase
 
     public function testSendReceive()
     {
-        list($a, $b) = Channel::create();
+        Coroutine\create(function () {
+            list($a, $b) = Channel::create();
 
-        $a->send('hello')->then(function () use ($b) {
-            return new Coroutine\Coroutine($b->receive());
-        })->done(function ($data) {
+            yield $a->send('hello');
+            $data = (yield $b->receive());
             $this->assertEquals('hello', $data);
         });