Java：替代DataInputStream的字节序问题解决方案

Question

Java：替代DataInputStream的字节序问题解决方案

javaendianness

10

以下是替换DataInputStream以包装InputStream的代码示例，但提供了额外的方法来读取小端数据类型，而不仅仅是读取大端类型的常规方法。如果您需要，请随意使用。

我有一些保留意见，请注意不会更改功能的方法（读取大端类型的函数）。是否有办法将DataInputStream实现为基类并使用其方法（例如read()，readInt()，readChar()等）？

我的类层次结构似乎有点奇怪。这样做合适吗？

这些其他类型，如readUTF()或readLine()，是否需要小端版本？还是针对特定程序而言？

Java如何存储布尔类型？这也与字节序有关吗？

感谢解答我的疑问 :)

import java.io.*;

/**
 * Replacement for a DataInputStream that provides both little and big endian reading capabilities for convenience without need to implement a ByteBuffer
 * @author Bill (unspecified.specification@gmail.com)
 */
public class EndianInputStream extends InputStream implements DataInput {
    private DataInputStream dataInStream;
    private InputStream inStream;
    private byte byteBuffer[];

    /**
     * Constructor to wrap InputStream for little and big endian data
     * @param refInStream Inputstream to wrap
     */
    public EndianInputStream(InputStream refInStream) {
        inStream = refInStream;
        dataInStream = new DataInputStream(inStream);
        byteBuffer = new byte[8]; // Largest data type is 64-bits (8 bytes)
    }

    @Override
    public int available() throws IOException {
        return dataInStream.available();
    }

    @Override
    public final int read(byte refBuffer[], int offset, int readLen) throws IOException {
        return inStream.read(refBuffer, offset, readLen);
    }

    @Override
    public int read() throws IOException {
        return inStream.read();
    }

    @Override
    public final int readUnsignedByte() throws IOException {
        return dataInStream.readUnsignedByte();
    }

    @Deprecated
    @Override
    public final String readLine() throws IOException {
        return dataInStream.readLine();
    }

    @Override
    public final String readUTF() throws IOException {
        return dataInStream.readUTF();
    }

    @Override
    public final void close() throws IOException {
        dataInStream.close();
    }

    @Override
    public final void readFully(byte refBuffer[]) throws IOException {
        dataInStream.readFully(refBuffer, 0, refBuffer.length);
    }

    @Override
    public final void readFully(byte refBuffer[], int offset, int readLen) throws IOException {
        dataInStream.readFully(refBuffer, offset, readLen);
    }

    @Override
    public final int skipBytes(int n) throws IOException {
        return dataInStream.skipBytes(n);
    }

    @Override
    public final boolean readBoolean() throws IOException {
        return dataInStream.readBoolean();
    }

    @Override
    public final byte readByte() throws IOException {
        return dataInStream.readByte();
    }

    @Override
    public final float readFloat() throws IOException {
        return Float.intBitsToFloat(readInt());
    }

    @Override
    public final double readDouble() throws IOException {
        return Double.longBitsToDouble(readLong());
    }

    @Override
    public final short readShort() throws IOException {
        return dataInStream.readShort();
    }

    @Override
    public final int readUnsignedShort() throws IOException {
        return dataInStream.readUnsignedShort();
    }

    @Override
    public final long readLong() throws IOException {
        return dataInStream.readLong();
    }

    @Override
    public final char readChar() throws IOException {
        return dataInStream.readChar();
    }

    @Override
    public final int readInt() throws IOException {
        return dataInStream.readInt();
    }

    /**
     * Reads floating point type stored in little endian (see readFloat() for big endian)
     * @return float value translated from little endian
     * @throws IOException if an IO error occurs
     */
    public final float readLittleFloat() throws IOException {
        return Float.intBitsToFloat(readLittleInt());
    }    

    /**
     * Reads double precision floating point type stored in little endian (see readDouble() for big endian)
     * @return double precision float value translated from little endian
     * @throws IOException if an IO error occurs
     */    
    public final double readLittleDouble() throws IOException {
        return Double.longBitsToDouble(readLittleLong());
    }

    /**
     * Reads short type stored in little endian (see readShort() for big endian)
     * @return short value translated from little endian
     * @throws IOException if an IO error occurs
     */    
    public final short readLittleShort() throws IOException {
    dataInStream.readFully(byteBuffer, 0, 2);
    return (short)((byteBuffer[1] & 0xff) << 8 | (byteBuffer[0] & 0xff));
    }

    /**
     * Reads char (16-bits) type stored in little endian (see readChar() for big endian)
     * @return char value translated from little endian
     * @throws IOException if an IO error occurs
     */    
    public final char readLittleChar() throws IOException {
        dataInStream.readFully(byteBuffer, 0, 2);
        return (char)((byteBuffer[1] & 0xff) << 8 | (byteBuffer[0] & 0xff));
    }    

    /**
     * Reads integer type stored in little endian (see readInt() for big endian)
     * @return integer value translated from little endian
     * @throws IOException if an IO error occurs
     */        
    public final int readLittleInt() throws IOException {
        dataInStream.readFully(byteBuffer, 0, 4);
        return (byteBuffer[3]) << 24 | (byteBuffer[2] & 0xff) << 16 |
            (byteBuffer[1] & 0xff) << 8 | (byteBuffer[0] & 0xff);
    }

    /**
     * Reads long type stored in little endian (see readLong() for big endian)
     * @return long value translated from little endian
     * @throws IOException if an IO error occurs
     */        
    public final long readLittleLong() throws IOException {
        dataInStream.readFully(byteBuffer, 0, 8);
        return (long)(byteBuffer[7]) << 56 | (long)(byteBuffer[6]&0xff) << 48 |
            (long)(byteBuffer[5] & 0xff) << 40 | (long)(byteBuffer[4] & 0xff) << 32 |
            (long)(byteBuffer[3] & 0xff) << 24 | (long)(byteBuffer[2] & 0xff) << 16 |
            (long)(byteBuffer[1] & 0xff) <<  8 | (long)(byteBuffer[0] & 0xff);
    }

    /**
     * Reads unsigned short type stored in little endian (see readUnsignedShort() for big endian)
     * @return integer value representing unsigned short value translated from little endian
     * @throws IOException if an IO error occurs
     */        
    public final int readLittleUnsignedShort() throws IOException {
        dataInStream.readFully(byteBuffer, 0, 2);
        return ((byteBuffer[1] & 0xff) << 8 | (byteBuffer[0] & 0xff));
    }
}

- William the Coderer

1个回答

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- McDowell · Accepted Answer

readBoolean() 读取一个字节。 readLine() 读取单个字节，并将每个字节转换为char。

readUTF() 读取修改后的UTF-8（其代码单元大小为一个八位字节）。UTF-8没有{{link4:字节序}}。

这些方法没有字节序问题。

关于设计，需要考虑类型是否需要是InputStream，以及ByteBuffer是否有用。如果您不使用mark/reset和Closeable等功能，则可能不会公开新类型：

public class Bytes {
  public static DataInput littleEndian(final DataInput decorated) {
    class LittleInput implements DataInput {
      private ByteBuffer buffer = ByteBuffer.allocate(8);

      public int readInt() throws IOException {
        buffer.clear();
        buffer.order(ByteOrder.BIG_ENDIAN)
            .putInt(decorated.readInt())
            .flip();
        return buffer.order(ByteOrder.LITTLE_ENDIAN)
            .getInt();
      }

      //TODO: other methods    
    }

    return new LittleInput();
  }

}

我注意到流行的Guava库已经有了LittleEndianDataInputStream。