libthrift0.9.0解析（三）之TProtocol&TTransport

  

以上是transport和protocol的类图和结构图。

transport封装了底层的传输通道，主要有read/write、open/close等基本的读写方法，而且都是对于二进制数据。

protocol则对应了thrift中的各种数据结构的读写，底层调用transport。

TIOStreamTransport封装了inputStream和outputStream，TSocket封装了Socket对象，使用了socket的inputStream和outputStream：

 socket_.connect(new InetSocketAddress(host_, port_), timeout_);
 inputStream_ = new BufferedInputStream(socket_.getInputStream(), 1024);
 outputStream_ = new BufferedOutputStream(socket_.getOutputStream(), 1024);

 TBinaryProtocol以二进制的形式读写数据，举例如下：

// 写入整数
private byte[] i32out = new byte[4];
  public void writeI32(int i32) throws TException {
    i32out[0] = (byte)(0xff & (i32 >> 24));
    i32out[1] = (byte)(0xff & (i32 >> 16));
    i32out[2] = (byte)(0xff & (i32 >> 8));
    i32out[3] = (byte)(0xff & (i32));
    trans_.write(i32out, 0, 4);
  }

// 读取整数
private byte[] i32rd = new byte[4];
  public int readI32() throws TException {
    byte[] buf = i32rd;
    int off = 0;

    if (trans_.getBytesRemainingInBuffer() >= 4) {
      buf = trans_.getBuffer();
      off = trans_.getBufferPosition();
      trans_.consumeBuffer(4);
    } else {
      readAll(i32rd, 0, 4);
    }
    return
      ((buf[off] & 0xff) << 24) |
      ((buf[off+1] & 0xff) << 16) |
      ((buf[off+2] & 0xff) <<  8) |
      ((buf[off+3] & 0xff));
  }

 其中的TMessage类型数据代表了包头，name成员描述了函数名称，type成员描述了消息类型，seqid应该是此次对话的唯一id。