netty ByteOrder大小端

 ByteOrder直译的意思就是字节序。

在计算机网络二进制传输的过程中，字节存在两种序列化顺序：高位字节序和低位字节序。

高位字节序：高位字节在前，低位字节在后(内存地址低位在前，高位地址在后)。低位字节序：低位字节在前，高位字节在后(内存地址低位在前，高位地址在后)。

netty中默认字节序是大端字节序，即字节高位在前，低位在后，符合人类的书写习惯。

ByteOrder类也比较简单，只存在返回高位还是低位的ByteOrder和描述ByteOrder的name字段。

 public final class ByteOrder {
​
    private String name;
​
    private ByteOrder(String name) {
        this.name = name;
    }
​
    /**
     * Constant denoting big-endian byte order.  In this order, the bytes of a
     * multibyte value are ordered from most significant to least significant.
     */
    public static final ByteOrder BIG_ENDIAN
        = new ByteOrder("BIG_ENDIAN");
​
    /**
     * Constant denoting little-endian byte order.  In this order, the bytes of
     * a multibyte value are ordered from least significant to most
     * significant.
     */
    public static final ByteOrder LITTLE_ENDIAN
        = new ByteOrder("LITTLE_ENDIAN");
​
    /**
     * Retrieves the native byte order of the underlying platform.
     *
     * <p> This method is defined so that performance-sensitive Java code can
     * allocate direct buffers with the same byte order as the hardware.
     * Native code libraries are often more efficient when such buffers are
     * used.  </p>
     *
     * @return  The native byte order of the hardware upon which this Java
     *          virtual machine is running
     */
    public static ByteOrder nativeOrder() {
        return Bits.byteOrder();
    }
​
    /**
     * Constructs a string describing this object.
     *
     * <p> This method returns the string <tt>"BIG_ENDIAN"</tt> for {@link
     * #BIG_ENDIAN} and <tt>"LITTLE_ENDIAN"</tt> for {@link #LITTLE_ENDIAN}.
     * </p>
     *
     * @return  The specified string
     */
    public String toString() {
        return name;
    }
​
}

netty测试：

①、默认使用高位存储字节序。

public class ByteOrder {
​
    private static final int writeInt = 345;
​
    public static void main(String[] args) {
        ByteBuf byteBuf = Unpooled.buffer(4,4);
        byteBuf.writeIntLE(writeInt);
        byte[] arr = new byte[4];
        byteBuf.readBytes(arr);
        System.out.println(Arrays.toString(arr));
    }
​
}

 

②、使用小端字节序。