Implement GzipOutputStream, closes #5

lib/GzipOutputStream.php

@@ -0,0 +1,68 @@
+<?php
+
+namespace Amp\ByteStream;
+
+use Amp\Promise;
+
+class GzipOutputStream implements OutputStream {
+    private $destination;
+    private $resource;
+
+    public function __construct(OutputStream $destination) {
+        $this->destination = $destination;
+        $this->resource = \deflate_init(\ZLIB_ENCODING_GZIP);
+
+        if ($this->resource === false) {
+            throw new StreamException("Failed initializing deflate context");
+        }
+    }
+
+    public function write(string $data): Promise {
+        if ($this->resource === null) {
+            throw new ClosedException("The stream has already been closed");
+        }
+
+        $compressed = \deflate_add($this->resource, $data, \ZLIB_SYNC_FLUSH);
+
+        if ($compressed === false) {
+            throw new StreamException("Failed adding data to deflate context");
+        }
+
+        $promise = $this->destination->write($compressed);
+        $promise->onResolve(function ($error) {
+            if ($error) {
+                $this->close();
+            }
+        });
+
+        return $promise;
+    }
+
+    public function end(string $finalData = ""): Promise {
+        if ($this->resource === null) {
+            throw new ClosedException("The stream has already been closed");
+        }
+
+        $compressed = \deflate_add($this->resource, $finalData, \ZLIB_FINISH);
+
+        if ($compressed === false) {
+            throw new StreamException("Failed adding data to deflate context");
+        }
+
+        $promise = $this->destination->write($compressed);
+        $promise->onResolve(function ($error) {
+            if ($error) {
+                $this->close();
+            }
+        });
+
+        return $promise;
+    }
+
+    public function close() {
+        $this->resource = null;
+        $this->destination = null;
+
+        $this->destination->close();
+    }
+}