class BufferedReader {
 public:
    explicit BufferedReader(PackageStream *stream) : _stream(stream) {
        _data = new char[stream->PackageLen()];
        _packageLen = stream->ReadPackage(_data);
    }

    int32_t Read(char *output_buffer, int32_t buffer_len) {
        int32_t actual_len = 0;
        for (; _data_index < _packageLen && actual_len < buffer_len;
               ++_data_index)
            output_buffer[actual_len++] = _data[_data_index];
        while (actual_len < buffer_len && 0 != _packageLen) {
            _packageLen = _stream->ReadPackage(_data);
            _data_index = 0;
            for (; _data_index < _packageLen && actual_len < buffer_len;
                   ++_data_index)
                output_buffer[actual_len++] = _data[_data_index];
        }
        return actual_len;
    }

    ~BufferedReader() {
        delete[] _data;
    }

 private:
    PackageStream *_stream;
    char *_data;
    int32_t _data_index = 0;
    int32_t _packageLen;
};