thrift-transport

org.apache.thrift.transport.TTransport

传输组件抽象描述。​

---

public abstract class TTransport implements Closeable {
  public abstract boolean isOpen();

  public boolean peek() { return isOpen(); }

  public abstract void open() throws TTransportException;
  
  public abstract void close();

  public abstract int read(byte[] buf, int off, int len) throws TTransportException;

  public int readAll(byte[] buf, int off, int len)
    throws TTransportException {
    int got = 0;
    int ret = 0;
    while (got < len) {
      ret = read(buf, off+got, len-got);
      if (ret <= 0) {
        throw new TTransportException(
            "Cannot read. Remote side has closed. Tried to read "
                + len
                + " bytes, but only got "
                + got
                + " bytes. (This is often indicative of an internal error on the server side. Please check your server logs.)");
      }
      got += ret;
    }
    return got;
  }

  public void write(byte[] buf) throws TTransportException {
    write(buf, 0, buf.length);
  }

  public abstract void write(byte[] buf, int off, int len) throws TTransportException;

  public void flush() throws TTransportException {}

  public byte[] getBuffer() { return null; }

  public int getBufferPosition() { return 0; }

  public int getBytesRemainingInBuffer() { return -1; }

  public void consumeBuffer(int len) {}
}

TIOStreamTransport

基于 IO 流的传输组件。

public class TIOStreamTransport extends TTransport {
  protected InputStream inputStream_ = null;
	protected OutputStream outputStream_ = null;

  public int read(byte[] buf, int off, int len) throws TTransportException {
    if (inputStream_ == null) {
      throw new TTransportException(TTransportException.NOT_OPEN, "Cannot read from null inputStream");
    }
    int bytesRead;
    try {
      bytesRead = inputStream_.read(buf, off, len);
    } catch (IOException iox) {
      throw new TTransportException(TTransportException.UNKNOWN, iox);
    }
    if (bytesRead < 0) {
      throw new TTransportException(TTransportException.END_OF_FILE);
    }
    return bytesRead;
  }

  public void write(byte[] buf, int off, int len) throws TTransportException {
    if (outputStream_ == null) {
      throw new TTransportException(TTransportException.NOT_OPEN, "Cannot write to null outputStream");
    }
    try {
      outputStream_.write(buf, off, len);
    } catch (IOException iox) {
      throw new TTransportException(TTransportException.UNKNOWN, iox);
    }
  }

TMemoryInputTransport

封装了一个字节数组byte[]来做输入流的封装

public final class TMemoryInputTransport extends TTransport {

  // 共有 endPos_ - pos_ 个元素
  private byte[] buf_;
  // 开始读位置
  private int pos_;
  private int endPos_;
  public TMemoryInputTransport() {
  }
  public TMemoryInputTransport(byte[] buf) {
    reset(buf);
  }
  public TMemoryInputTransport(byte[] buf, int offset, int length) {
    reset(buf, offset, length);
  }
  public void reset(byte[] buf) {
    reset(buf, 0, buf.length);
  }
  public void reset(byte[] buf, int offset, int length) {
    buf_ = buf;
    pos_ = offset;
    endPos_ = offset + length;
  }
  public void clear() {
    buf_ = null;
  }
  @Override
  public void close() {}
  @Override
  public boolean isOpen() {
    return true;
  }
  @Override
  public void open() throws TTransportException {}
  @Override
  public int read(byte[] buf, int off, int len) throws TTransportException {
    int bytesRemaining = getBytesRemainingInBuffer();
    int amtToRead = (len > bytesRemaining ? bytesRemaining : len);
    if (amtToRead > 0) {
      System.arraycopy(buf_, pos_, buf, off, amtToRead);
      consumeBuffer(amtToRead);
    }
    return amtToRead;
  }
  @Override
  public void write(byte[] buf, int off, int len) throws TTransportException {
    throw new UnsupportedOperationException("No writing allowed!");
  }
  @Override
  public byte[] getBuffer() {
    return buf_;
  }
  public int getBufferPosition() {
    return pos_;
  }
  public int getBytesRemainingInBuffer() {
    return endPos_ - pos_;
  }
  public void consumeBuffer(int len) {
    pos_ += len;
  }
}

与 Java NIO 中的 Buffer 类似。

TMemoryBuffer

使用字节数组输出流ByteArrayOutputStream做输出流的封装

public class TMemoryBuffer extends TTransport {
  /**
   * Create a TMemoryBuffer with an initial buffer size of <i>size</i>. The
   * internal buffer will grow as necessary to accommodate the size of the data
   * being written to it.
   */
  public TMemoryBuffer(int size) {
    arr_ = new TByteArrayOutputStream(size);
  }

  @Override
  public boolean isOpen() {
    return true;
  }

  @Override
  public void open() {
    /* Do nothing */
  }

  @Override
  public void close() {
    /* Do nothing */
  }

  @Override
  public int read(byte[] buf, int off, int len) {
    byte[] src = arr_.get();
    int amtToRead = (len > arr_.len() - pos_ ? arr_.len() - pos_ : len);
    if (amtToRead > 0) {
      System.arraycopy(src, pos_, buf, off, amtToRead);
      pos_ += amtToRead;
    }
    return amtToRead;
  }

  @Override
  public void write(byte[] buf, int off, int len) {
    arr_.write(buf, off, len);
  }

  /**
   * Output the contents of the memory buffer as a String, using the supplied
   * encoding
   * @param enc  the encoding to use
   * @return the contents of the memory buffer as a String
   */
  public String toString(String enc) throws UnsupportedEncodingException {
    return arr_.toString(enc);
  }

  public String inspect() {
    StringBuilder buf = new StringBuilder();
    byte[] bytes = arr_.toByteArray();
    for (int i = 0; i < bytes.length; i++) {
      buf.append(pos_ == i ? "==>" : "" ).append(Integer.toHexString(bytes[i] & 0xff)).append(" ");
    }
    return buf.toString();
  }

  // The contents of the buffer
  private TByteArrayOutputStream arr_;

  // Position to read next byte from
  private int pos_;

  public int length() {
    return arr_.size();
  }

  public byte[] getArray() {
    return arr_.get();
  }
}

AutoExpandingBufferReadTransport

AutoExpandingBufferWriteTransport

内部使用可正常的直接数组
AutoExpandingBuffer

AutoExpandingBufferReadTransport
AutoExpandingBufferWriteTransport
TMemoryInputTransport
TByteArrayOutputStream
TMemoryBuffer
内部都是采用直接数组的形式。