java整型数与网络字节序的 byte[] 数组转换关系

工作项目需要在 java 和 c/c++ 之间进行 socket 通信， socket 通信是以字节流或者字节包进行的， socket 发送方须将数据转换为字节流或者字节包，而接收方则将字节流和字节包再转换回相应的数据类型。如果发送方和接收方都是同种语言，则一般只涉及到字节序的调整。而对于 java 和 c/c++ 的通信，则情况就要复杂一些，主要是因为 java 中没有 unsigned 类型，并且 java 和 c 在某些数据类型上的长度不一致。
    本文就是针对这种情况，整理了 java 数据类型和网络字节流或字节包 ( 相当于 java 的 byte 数组 ) 之间转换方法。实际上网上这方面的资料不少，但往往不全，甚至有些有错误，于是就花了点时间对 java 整型数和网络字节序的 byte[] 之间转换的各种情况做了一些验证和整理。整理出来的函数如下：

public class ByteConvert {

	/**
	 * 长整形转byte数组
	 * 
	 * @param n
	 *            长整形数字
	 * @return 转换后的数组
	 */
	public static byte[] longToBytes(long n) {
		byte[] b = new byte[8];
		b[7] = (byte) (n & 0xff);
		b[6] = (byte) (n >> 8 & 0xff);
		b[5] = (byte) (n >> 16 & 0xff);
		b[4] = (byte) (n >> 24 & 0xff);
		b[3] = (byte) (n >> 32 & 0xff);
		b[2] = (byte) (n >> 40 & 0xff);
		b[1] = (byte) (n >> 48 & 0xff);
		b[0] = (byte) (n >> 56 & 0xff);
		return b;
	}

	/**
	 * 长整形转byte数组
	 * 
	 * @param n
	 *            长整形数字
	 * @param array
	 *            转换后的结果
	 * @param offset
	 *            从第offset位开始转换
	 */
	public static void longToBytes(long n, byte[] array, int offset) {
		array[7 + offset] = (byte) (n & 0xff);
		array[6 + offset] = (byte) (n >> 8 & 0xff);
		array[5 + offset] = (byte) (n >> 16 & 0xff);
		array[4 + offset] = (byte) (n >> 24 & 0xff);
		array[3 + offset] = (byte) (n >> 32 & 0xff);
		array[2 + offset] = (byte) (n >> 40 & 0xff);
		array[1 + offset] = (byte) (n >> 48 & 0xff);
		array[0 + offset] = (byte) (n >> 56 & 0xff);
	}

	/**
	 * bytes 转 Long
	 * 
	 * @param array
	 *            要转换的byte
	 * @return long长整形数字
	 */
	public static long bytesToLong(byte[] array) {
		return ((((long) array[0] & 0xff) << 56) | (((long) array[1] & 0xff) << 48) | (((long) array[2] & 0xff) << 40)
		        | (((long) array[3] & 0xff) << 32) | (((long) array[4] & 0xff) << 24)
		        | (((long) array[5] & 0xff) << 16) | (((long) array[6] & 0xff) << 8) | (((long) array[7] & 0xff) << 0));
	}

	/**
	 * byte数组转长整形数字
	 * 
	 * @param array
	 *            要转换的byte数组
	 * @param offset
	 *            从第offset开始转换
	 * @return 转换后的长整形数字
	 */
	public static long bytesToLong(byte[] array, int offset) {
		return ((((long) array[offset + 0] & 0xff) << 56) | (((long) array[offset + 1] & 0xff) << 48)
		        | (((long) array[offset + 2] & 0xff) << 40) | (((long) array[offset + 3] & 0xff) << 32)
		        | (((long) array[offset + 4] & 0xff) << 24) | (((long) array[offset + 5] & 0xff) << 16)
		        | (((long) array[offset + 6] & 0xff) << 8) | (((long) array[offset + 7] & 0xff) << 0));
	}

	public static byte[] intToBytes(int n) {
		byte[] b = new byte[4];
		b[3] = (byte) (n & 0xff);
		b[2] = (byte) (n >> 8 & 0xff);
		b[1] = (byte) (n >> 16 & 0xff);
		b[0] = (byte) (n >> 24 & 0xff);
		return b;
	}

	public static void intToBytes(int n, byte[] array, int offset) {
		array[3 + offset] = (byte) (n & 0xff);
		array[2 + offset] = (byte) (n >> 8 & 0xff);
		array[1 + offset] = (byte) (n >> 16 & 0xff);
		array[offset] = (byte) (n >> 24 & 0xff);
	}

	/**
	 * @param b
	 * @return
	 */
	public static int bytesToInt(byte b[]) {
		return b[3] & 0xff | (b[2] & 0xff) << 8 | (b[1] & 0xff) << 16 | (b[0] & 0xff) << 24;
	}

	/**
	 * byte 数组转 int
	 * 
	 * @param b
	 *            byte数组
	 * @param offset
	 *            从数组的第几位开始转
	 * @return 整形
	 */
	public static int bytesToInt(byte b[], int offset) {
		return b[offset + 3] & 0xff | (b[offset + 2] & 0xff) << 8 | (b[offset + 1] & 0xff) << 16
		        | (b[offset] & 0xff) << 24;
	}

	/**
	 * 无符号整形转数组
	 * 
	 * @param n
	 *            要转换的整形
	 * @return byte数组
	 */
	public static byte[] uintToBytes(long n) {
		byte[] b = new byte[4];
		b[3] = (byte) (n & 0xff);
		b[2] = (byte) (n >> 8 & 0xff);
		b[1] = (byte) (n >> 16 & 0xff);
		b[0] = (byte) (n >> 24 & 0xff);

		return b;
	}

	public static void uintToBytes(long n, byte[] array, int offset) {
		array[3 + offset] = (byte) (n);
		array[2 + offset] = (byte) (n >> 8 & 0xff);
		array[1 + offset] = (byte) (n >> 16 & 0xff);
		array[offset] = (byte) (n >> 24 & 0xff);
	}

	public static long bytesToUint(byte[] array) {
		return ((long) (array[3] & 0xff)) | ((long) (array[2] & 0xff)) << 8 | ((long) (array[1] & 0xff)) << 16
		        | ((long) (array[0] & 0xff)) << 24;
	}

	public static long bytesToUint(byte[] array, int offset) {
		return ((long) (array[offset + 3] & 0xff)) | ((long) (array[offset + 2] & 0xff)) << 8
		        | ((long) (array[offset + 1] & 0xff)) << 16 | ((long) (array[offset] & 0xff)) << 24;
	}

	public static byte[] shortToBytes(short n) {
		byte[] b = new byte[2];
		b[1] = (byte) (n & 0xff);
		b[0] = (byte) ((n >> 8) & 0xff);
		return b;
	}

	public static void shortToBytes(short n, byte[] array, int offset) {
		array[offset + 1] = (byte) (n & 0xff);
		array[offset] = (byte) ((n >> 8) & 0xff);
	}

	public static short bytesToShort(byte[] b) {
		return (short) (b[1] & 0xff | (b[0] & 0xff) << 8);
	}

	public static short bytesToShort(byte[] b, int offset) {
		return (short) (b[offset + 1] & 0xff | (b[offset] & 0xff) << 8);
	}

	public static byte[] ushortToBytes(int n) {
		byte[] b = new byte[2];
		b[1] = (byte) (n & 0xff);
		b[0] = (byte) ((n >> 8) & 0xff);
		return b;
	}

	public static void ushortToBytes(int n, byte[] array, int offset) {
		array[offset + 1] = (byte) (n & 0xff);
		array[offset] = (byte) ((n >> 8) & 0xff);
	}

	public static int bytesToUshort(byte b[]) {
		return b[1] & 0xff | (b[0] & 0xff) << 8;
	}

	public static int bytesToUshort(byte b[], int offset) {
		return b[offset + 1] & 0xff | (b[offset] & 0xff) << 8;
	}

	public static byte[] ubyteToBytes(int n) {
		byte[] b = new byte[1];
		b[0] = (byte) (n & 0xff);
		return b;
	}

	public static void ubyteToBytes(int n, byte[] array, int offset) {
		array[0] = (byte) (n & 0xff);
	}

	public static int bytesToUbyte(byte[] array) {
		return array[0] & 0xff;
	}

	public static int bytesToUbyte(byte[] array, int offset) {
		return array[offset] & 0xff;
	}
	// char 类型、 float、double 类型和 byte[] 数组之间的转换关系还需继续研究实现。
}