int 转换成定长的 byte数组

public byte[] IntToByteArray(int src, int length)
{
    byte[] b = new byte[length];
    for (int i = 0; i < length; i++)
    {
            b[length - i - 1] = (byte)((src >> 8 * i) & 0xff);
    }
    return b;

}