muduo库阅读（37）——Net部分：压缩数据流ZlibOutputStream

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/* * 压缩数据流 * 输入是普通数据流，输出是压缩数据流 */class ZlibOutputStream : boost::noncopyable{public:// 初始化explicit ZlibOutputStream(Buffer* output): output_(output),  zerror_(Z_OK),  bufferSize_(1024){bzero(&zstream_, sizeof zstream_);// 初始化压缩数据流zerror_ = deflateInit(&zstream_, Z_DEFAULT_COMPRESSION);}~ZlibOutputStream(){finish();}// 返回错误信息const char* zlibErrorMessage() const { return zstream_.msg; }// 返回错误码int zlibErrorCode() const { return zerror_; }// 返回输入流的字节数int64_t inputBytes() const { return zstream_.total_in; }// 返回输出流的字节数int64_t outputBytes() const { return zstream_.total_out; }// 内部缓冲区的大小int internalOutputBufferSize() const { return bufferSize_; }// 写入数据，然后进行压缩bool write(StringPiece buf){if (zerror_ != Z_OK)return false;assert(zstream_.next_in == NULL && zstream_.avail_in == 0);void* in = const_cast<char*>(buf.data());// 设置压缩数据起始位置和长度zstream_.next_in = static_cast<Bytef*>(in);zstream_.avail_in = buf.size();// 压缩while (zstream_.avail_in > 0 && zerror_ == Z_OK){zerror_ = compress(Z_NO_FLUSH);}if (zstream_.avail_in == 0){assert(static_cast<const void*>(zstream_.next_in) == buf.end());zstream_.next_in = NULL;}return zerror_ == Z_OK;}// 输入数据并进行压缩bool write(Buffer* input){if (zerror_ != Z_OK)return false;void* in = const_cast<char*>(input->peek());zstream_.next_in = static_cast<Bytef*>(in);zstream_.avail_in = static_cast<int>(input->readableBytes());// 压缩if (zstream_.avail_in > 0 && zerror_ == Z_OK){zerror_ = compress(Z_NO_FLUSH);}input->retrieve(input->readableBytes() - zstream_.avail_in);return zerror_ == Z_OK;}// 刷新bool finish(){if (zerror_ != Z_OK)return false;while (zerror_ == Z_OK){// 冲刷zerror_ = compress(Z_FINISH);}zerror_ = deflateEnd(&zstream_);bool ok = zerror_ == Z_OK;zerror_ = Z_STREAM_END;return ok;}private:// 压缩int compress(int flush){output_->ensureWritableBytes(bufferSize_);zstream_.next_out = reinterpret_cast<Bytef*>(output_->beginWrite());zstream_.avail_out = static_cast<int>(output_->writableBytes());// 压缩数据int error = ::deflate(&zstream_, flush);output_->hasWritten(output_->writableBytes() - zstream_.avail_out);if (output_->writableBytes() == 0 && bufferSize_ < 65536){bufferSize_ *= 2;}return error;}// 输出缓冲区Buffer* output_;// 压缩的数据流z_stream zstream_;// 错误码int zerror_;// 缓冲区的大小int bufferSize_;};
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