byte[] 转 int int 转byte apache mina源码

    /**
     * Returns the integer represented by up to 4 bytes in network byte order.
     * 
     * @param buf the buffer to read the bytes from
     * @param start
     * @param count
     * @return
     */
    public static int networkByteOrderToInt(byte[] buf, int start, int count) {
        if (count > 4) {
            throw new IllegalArgumentException("Cannot handle more than 4 bytes");
        }

        int result = 0;

        for (int i = 0; i < count; i++) {
            result <<= 8;
            result |= (buf[start + i] & 0xff);
        }

        return result;
    }

    /**
     * Encodes an integer into up to 4 bytes in network byte order.
     * 
     * @param num the int to convert to a byte array
     * @param count the number of reserved bytes for the write operation
     * @return the resulting byte array
     */
    public static byte[] intToNetworkByteOrder(int num, int count) {
        byte[] buf = new byte[count];
        intToNetworkByteOrder(num, buf, 0, count);

        return buf;
    }

    /**
     * Encodes an integer into up to 4 bytes in network byte order in the 
     * supplied buffer starting at <code>start</code> offset and writing
     * <code>count</code> bytes.
     * 
     * @param num the int to convert to a byte array
     * @param buf the buffer to write the bytes to
     * @param start the offset from beginning for the write operation
     * @param count the number of reserved bytes for the write operation
     */
    public static void intToNetworkByteOrder(int num, byte[] buf, int start, int count) {
        if (count > 4) {
            throw new IllegalArgumentException("Cannot handle more than 4 bytes");
        }

        for (int i = count - 1; i >= 0; i--) {
            buf[start + i] = (byte) (num & 0xff);
            num >>>= 8;
        }
    }