thrift-TBinaryProtocol

TBinaryProtocol 工廠類。

 public static class Factory implements TProtocolFactory {
    protected long stringLengthLimit_;
    protected long containerLengthLimit_;
    protected boolean strictRead_;
    protected boolean strictWrite_;

    public Factory() {
      this(false, true);
    }

    public Factory(boolean strictRead, boolean strictWrite) {
      this(strictRead, strictWrite, NO_LENGTH_LIMIT, NO_LENGTH_LIMIT);
    }

    public Factory(boolean strictRead, boolean strictWrite, long stringLengthLimit, long containerLengthLimit) {
      stringLengthLimit_ = stringLengthLimit;
      containerLengthLimit_ = containerLengthLimit;
      strictRead_ = strictRead;
      strictWrite_ = strictWrite;
    }

    public TProtocol getProtocol(TTransport trans) {
      return new TBinaryProtocol(trans, stringLengthLimit_, containerLengthLimit_, strictRead_, strictWrite_);
    }
  }

構造方法：

public TBinaryProtocol(TTransport trans) {
    this(trans, false, true);
  }

  public TBinaryProtocol(TTransport trans, boolean strictRead, boolean strictWrite) {
    this(trans, NO_LENGTH_LIMIT, NO_LENGTH_LIMIT, strictRead, strictWrite);
  }

  public TBinaryProtocol(TTransport trans, long stringLengthLimit, long containerLengthLimit, boolean strictRead, boolean strictWrite) {
    super(trans);
    stringLengthLimit_ = stringLengthLimit;
    containerLengthLimit_ = containerLengthLimit;
    strictRead_ = strictRead;
    strictWrite_ = strictWrite;
  }

public class TBinaryProtocol extends TProtocol {
  private static final TStruct ANONYMOUS_STRUCT = new TStruct();
  private static final long NO_LENGTH_LIMIT = -1;

  protected static final int VERSION_MASK = 0xffff0000;
  protected static final int VERSION_1 = 0x80010000;

  /**
   * The maximum number of bytes to read from the transport for
   * variable-length fields (such as strings or binary) or {@link #NO_LENGTH_LIMIT} for
   * unlimited.
   */
  private final long stringLengthLimit_;

  /**
   * The maximum number of elements to read from the network for
   * containers (maps, sets, lists), or {@link #NO_LENGTH_LIMIT} for unlimited.
   */
  private final long containerLengthLimit_;

  protected boolean strictRead_;
  protected boolean strictWrite_;


  public void writeMessageBegin(TMessage message) throws TException {
    if (strictWrite_) {
      int version = VERSION_1 | message.type;
      writeI32(version);
      writeString(message.name);
      writeI32(message.seqid);
    } else {
      writeString(message.name);
      writeByte(message.type);
      writeI32(message.seqid);
    }
  }
  
  public TMessage readMessageBegin() throws TException {
    int size = readI32();
    if (size < 0) {
      int version = size & VERSION_MASK;
      if (version != VERSION_1) {
        throw new TProtocolException(TProtocolException.BAD_VERSION, "Bad version in readMessageBegin");
      }
      return new TMessage(readString(), (byte)(size & 0x000000ff), readI32());
    } else {
      if (strictRead_) {
        throw new TProtocolException(TProtocolException.BAD_VERSION, "Missing version in readMessageBegin, old client?");
      }
      return new TMessage(readStringBody(size), readByte(), readI32());
    }
  }
  
  // 寫了１個字節的數據類型，和2個字節的順序號
  public void writeFieldBegin(TField field) throws TException {
    writeByte(field.type);
    writeI16(field.id);
  }
  
  // 先讀1個字節的數據類型，再讀2個字節的順序號
  public TField readFieldBegin() throws TException {
    byte type = readByte();
    short id = type == TType.STOP ? 0 : readI16();
    return new TField("", type, id);
  }

  public void writeMapBegin(TMap map) throws TException {
    writeByte(map.keyType);
    writeByte(map.valueType);
    writeI32(map.size);
  }
  
 	public TMap readMapBegin() throws TException {
    TMap map = new TMap(readByte(), readByte(), readI32());
    checkContainerReadLength(map.size);
    return map;
  }

  public void writeListBegin(TList list) throws TException {
    writeByte(list.elemType);
    writeI32(list.size);
  }
  
  public TList readListBegin() throws TException {
    TList list = new TList(readByte(), readI32());
    checkContainerReadLength(list.size);
    return list;
  }

  public void writeSetBegin(TSet set) throws TException {
    writeByte(set.elemType);
    writeI32(set.size);
  }

  public TSet readSetBegin() throws TException {
    TSet set = new TSet(readByte(), readI32());
    checkContainerReadLength(set.size);
    return set;
  }

  public void writeBool(boolean b) throws TException {
    writeByte(b ? (byte)1 : (byte)0);
  }

  public boolean readBool() throws TException {
    return (readByte() == 1);
  }  
  
  private byte [] bout = new byte[1];
  public void writeByte(byte b) throws TException {
    bout[0] = b;
    trans_.write(bout, 0, 1);
  }

  private byte[] bin = new byte[1];
  public byte readByte() throws TException {
    if (trans_.getBytesRemainingInBuffer() >= 1) {
      byte b = trans_.getBuffer()[trans_.getBufferPosition()];
      trans_.consumeBuffer(1);
      return b;
    }
    readAll(bin, 0, 1);
    return bin[0];
  }

  private byte[] i16out = new byte[2];
  public void writeI16(short i16) throws TException {
    i16out[0] = (byte)(0xff & (i16 >> 8));
    i16out[1] = (byte)(0xff & (i16));
    trans_.write(i16out, 0, 2);
  }
  
  private byte[] i16rd = new byte[2];
  public short readI16() throws TException {
    byte[] buf = i16rd;
    int off = 0;

    if (trans_.getBytesRemainingInBuffer() >= 2) {
      buf = trans_.getBuffer();
      off = trans_.getBufferPosition();
      trans_.consumeBuffer(2);
    } else {
      readAll(i16rd, 0, 2);
    }

    return
      (short)
      (((buf[off] & 0xff) << 8) |
       ((buf[off+1] & 0xff)));
  }

  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);
  }
  
  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));
  }

  private byte[] i64out = new byte[8];
  public void writeI64(long i64) throws TException {
    i64out[0] = (byte)(0xff & (i64 >> 56));
    i64out[1] = (byte)(0xff & (i64 >> 48));
    i64out[2] = (byte)(0xff & (i64 >> 40));
    i64out[3] = (byte)(0xff & (i64 >> 32));
    i64out[4] = (byte)(0xff & (i64 >> 24));
    i64out[5] = (byte)(0xff & (i64 >> 16));
    i64out[6] = (byte)(0xff & (i64 >> 8));
    i64out[7] = (byte)(0xff & (i64));
    trans_.write(i64out, 0, 8);
  }
 
   private byte[] i64rd = new byte[8];
  public long readI64() throws TException {
    byte[] buf = i64rd;
    int off = 0;

    if (trans_.getBytesRemainingInBuffer() >= 8) {
      buf = trans_.getBuffer();
      off = trans_.getBufferPosition();
      trans_.consumeBuffer(8);
    } else {
      readAll(i64rd, 0, 8);
    }

    return
      ((long)(buf[off]   & 0xff) << 56) |
      ((long)(buf[off+1] & 0xff) << 48) |
      ((long)(buf[off+2] & 0xff) << 40) |
      ((long)(buf[off+3] & 0xff) << 32) |
      ((long)(buf[off+4] & 0xff) << 24) |
      ((long)(buf[off+5] & 0xff) << 16) |
      ((long)(buf[off+6] & 0xff) <<  8) |
      ((long)(buf[off+7] & 0xff));
  }

  public void writeDouble(double dub) throws TException {
    writeI64(Double.doubleToLongBits(dub));
  }
  
   public double readDouble() throws TException {
    return Double.longBitsToDouble(readI64());
  }

  // 先寫４字節的字符串長度，再寫 UTF-8 編碼的字符串
  public void writeString(String str) throws TException {
    try {
      byte[] dat = str.getBytes("UTF-8");
      writeI32(dat.length);
      trans_.write(dat, 0, dat.length);
    } catch (UnsupportedEncodingException uex) {
      throw new TException("JVM DOES NOT SUPPORT UTF-8");
    }
  }
  
  public String readString() throws TException {
    int size = readI32();

    checkStringReadLength(size);
    if (stringLengthLimit_ > 0 && size > stringLengthLimit_) {
      throw new TProtocolException(TProtocolException.SIZE_LIMIT,
                                   "String field exceeded string size limit");
    }

    if (trans_.getBytesRemainingInBuffer() >= size) {
      try {
        String s = new String(trans_.getBuffer(), trans_.getBufferPosition(), size, "UTF-8");
        trans_.consumeBuffer(size);
        return s;
      } catch (UnsupportedEncodingException e) {
        throw new TException("JVM DOES NOT SUPPORT UTF-8");
      }
    }
    return readStringBody(size);
  }

  public String readStringBody(int size) throws TException {
    try {
      byte[] buf = new byte[size];
      trans_.readAll(buf, 0, size);
      return new String(buf, "UTF-8");
    } catch (UnsupportedEncodingException uex) {
      throw new TException("JVM DOES NOT SUPPORT UTF-8");
    }
  }
  
  public void writeBinary(ByteBuffer bin) throws TException {
    int length = bin.limit() - bin.position();
    writeI32(length);
    trans_.write(bin.array(), bin.position() + bin.arrayOffset(), length);
  }
  
  public ByteBuffer readBinary() throws TException {
    int size = readI32();

    if (stringLengthLimit_ > 0 && size > stringLengthLimit_) {
      throw new TProtocolException(TProtocolException.SIZE_LIMIT,
                                   "Binary field exceeded string size limit");
    }

    if (trans_.getBytesRemainingInBuffer() >= size) {
      ByteBuffer bb = ByteBuffer.wrap(trans_.getBuffer(), trans_.getBufferPosition(), size);
      trans_.consumeBuffer(size);
      return bb;
    }

    byte[] buf = new byte[size];
    trans_.readAll(buf, 0, size);
    return ByteBuffer.wrap(buf);
  }

  // 
  private void checkStringReadLength(int length) throws TProtocolException {
    if (length < 0) {
      throw new TProtocolException(TProtocolException.NEGATIVE_SIZE, "Negative length: " + length);
    }
    if (stringLengthLimit_ != NO_LENGTH_LIMIT && length > stringLengthLimit_) {
      throw new TProtocolException(TProtocolException.SIZE_LIMIT, "Length exceeded max allowed: " + length);
    }
  }

  // 
  private void checkContainerReadLength(int length) throws TProtocolException {
    if (length < 0) {
      throw new TProtocolException(TProtocolException.NEGATIVE_SIZE, "Negative length: " + length);
    }
    if (containerLengthLimit_ != NO_LENGTH_LIMIT && length > containerLengthLimit_) {
      throw new TProtocolException(TProtocolException.SIZE_LIMIT, "Length exceeded max allowed: " + length);
    }
  }

  private int readAll(byte[] buf, int off, int len) throws TException {
    return trans_.readAll(buf, off, len);
  }
}

所謂的嚴格的讀/寫，就是是否讀取和寫入版本號。

針對 thrift 0.9.3

版本號 VERSION_1 爲 0x80010000（10000000000000010000000000000000）

其實版本號只用了兩個字節標識，剩下的最後一個字節表示消息類型 message.type[ CALL(1), REPLY(2), EXCEPTION(3), ONEWAY(4)]。

故寫入的是（VERSION_1 | message.type）。

讀取的時候將其與 11111111111111110000000000000000 做與操作就得到了真正的版本號。與 0x000000ff 做與操作得到了 message.type。


消息頭最開始的 1 標誌了是新/舊版本的協議。

而計算機中整數是使用補碼存在的，故可以通過 readI32 判斷新舊編碼。

測試

public class T1 {
    @Test
    public void write() throws IOException, TException {
        Pair pair = new Pair();
        pair.setKey("name").setValue("lgh");
        FileOutputStream fos = new FileOutputStream(new File("pair.txt"));
        pair.write(new TBinaryProtocol(new TIOStreamTransport(fos)));
        fos.close();
    }

    @Test
    public void read() throws TException, IOException {
        Pair pair = new Pair();
        FileInputStream fis = new FileInputStream(new File("pair.txt"));
        pair.read(new TBinaryProtocol(new TIOStreamTransport(fis)));
        System.out.println("key => " + pair.getKey());
        System.out.println("value => " + pair.getValue());
        fis.close();
    }
}

namespace java com.meituan.model

struct Pair {
        1: required string key
        2: required string value
}

// pair.write 
public void write(org.apache.thrift.protocol.TProtocol oprot) throws org.apache.thrift.TException {   
     schemes.get(oprot.getScheme()).getScheme().write(oprot, this);                                    
 }
// Pair.PairStandardScheme#write
public void write(org.apache.thrift.protocol.TProtocol oprot, Pair struct) throws org.apache.thrift.TException {
    struct.validate();                                                                                          
                                                                                                                
    oprot.writeStructBegin(STRUCT_DESC); // TBinaryProtocol#writeStructBegin 無操作                                                                     
    if (struct.key != null) {                                                                                   
        oprot.writeFieldBegin(KEY_FIELD_DESC); // 寫1個字節參數類型，2個字節參數編號，如 key 爲1，value 爲2                                                              
        oprot.writeString(struct.key); // 寫4字節 Pair.key 對應的長度，和其對應的 UTF-8 編碼字節序列                                                                       
        oprot.writeFieldEnd(); // TBinaryProtocol#writeFieldEnd 無操作                                                                                  
    }                                                                                                           
    if (struct.value != null) {                                                                                 
        oprot.writeFieldBegin(VALUE_FIELD_DESC);                                                                
        oprot.writeString(struct.value);                                                                        
        oprot.writeFieldEnd();                                                                                  
    }                                                                                                           
    oprot.writeFieldStop(); // 寫入1字節0                                                                                   
    oprot.writeStructEnd(); // TBinaryProtocol#writeStructEnd 無操作                                                                                
}                                                                                                               

參數類型對應的值

public final class TType {
    public static final byte STOP   = 0;   // 數據讀寫完成
    public static final byte VOID   = 1;   // 空值
    public static final byte BOOL   = 2;   // 布爾值
    public static final byte BYTE   = 3;   // 字節
    public static final byte DOUBLE = 4;   // 雙精度浮點型
    public static final byte I16    = 6;   // 短整型
    public static final byte I32    = 8;   // 整型
    public static final byte I64    = 10;  // 長整型
    public static final byte STRING = 11;  // 字符串類型
    public static final byte STRUCT = 12;  // 引用類型
    public static final byte MAP    = 13;  // Map
    public static final byte SET    = 14;  // 集合
    public static final byte LIST   = 15;  // 列表
    public static final byte ENUM   = 16;  // 枚舉
}

數據的寫入規則：

→ hexdump -C pair.txt
00000000  0b 00 01 00 00 00 04 6e  61 6d 65 0b 00 02 00 00  |.......name.....|
00000010  00 03 6c 67 68 00                                 |..lgh.|
00000016

可以看到對於參數名稱，thrift 是無感知的。

參考：

https://juejin.im/post/5b290e58518825748c1c6bfc

https://blog.csdn.net/ITer_ZC/article/details/39497863

https://andrewpqc.github.io/2019/02/24/thrift/