protected function readChunked($bufferSize)
    {
        // at start of the next chunk?
        if (0 == $this->chunkLength) {
            $line = $this->socket->readLine($bufferSize);
            if (!preg_match('/^([0-9a-f]+)/i', $line, $matches)) {
                throw new HTTP_Request2_MessageException(
                    "Cannot decode chunked response, invalid chunk length '{$line}'",
                    HTTP_Request2_Exception::DECODE_ERROR
                );
            } else {
                $this->chunkLength = hexdec($matches[1]);
                // Chunk with zero length indicates the end
                if (0 == $this->chunkLength) {
                    $this->socket->readLine($bufferSize);
                    return '';
                }
            }
        }
        $data = $this->socket->read(min($this->chunkLength, $bufferSize));
        $this->chunkLength -= strlen($data);
        if (0 == $this->chunkLength) {
            $this->socket->readLine($bufferSize); // Trailing CRLF
        }
        return $data;
    }