Protobuf\Binary\StreamWriter::writeStream PHP Method

    public function writeStream(Stream $stream, Stream $value, $length = null)
    {
        if ($length === null) {
            $length = $value->getSize();
        }
        $stream->writeStream($value, $length);
    }

 public function testWriteStream()
 {
     $source = Stream::create();
     $target = Stream::create();
     $writer = new StreamWriter($this->config);
     $writer->writeVarint($source, WireFormat::getFieldKey(1, WireFormat::WIRE_FIXED64));
     $writer->writeDouble($source, 123456789.12345);
     $source->seek(0);
     $writer->writeStream($target, $source);
     $this->assertEquals((string) $source, (string) $target);
 }