Implement BufferedSink which resembles a promise-based async stream_g…

…et_contents()

BufferedSink.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace React\Stream;
+
+use React\Promise\Deferred;
+use React\Promise\PromisorInterface;
+use React\Stream\WritableStream;
+
+class BufferedSink extends WritableStream implements PromisorInterface
+{
+    private $buffer = '';
+    private $deferred;
+
+    public function __construct()
+    {
+        $this->deferred = new Deferred();
+
+        $this->on('pipe', array($this, 'handlePipeEvent'));
+        $this->on('error', array($this, 'handleErrorEvent'));
+    }
+
+    public function handlePipeEvent($source)
+    {
+        Util::forwardEvents($source, $this, array('error'));
+    }
+
+    public function handleErrorEvent($e)
+    {
+        $this->deferred->reject($e);
+    }
+
+    public function write($data)
+    {
+        $this->buffer .= $data;
+    }
+
+    public function close()
+    {
+        if ($this->closed) {
+            return;
+        }
+
+        parent::close();
+        $this->deferred->resolve($this->buffer);
+    }
+
+    public function promise()
+    {
+        return $this->deferred->promise();
+    }
+}