翻转一个字节

查表法

unsigned char reverse8(unsigned char c) {
    static unsigned char sta[16] = {//不多不少的静态数据
        0x00,0x08,0x04,0x0C,0x02,0x0A,0x06,0x0E,0x01,0x09,0x05,0x0D,0x03,0x0B,0x07,0x0F
    };
    unsigned char d = 0;
    d |= (sta[c & 0xF]) << 4;
    d |= sta[c >> 4];
    return d;
}

移位法

unsigned char reverse8_2(unsigned char c) {
    c = (c & 0x55) << 1 | (c & 0xAA) >> 1;
    c = (c & 0x33) << 2 | (c & 0xCC) >> 2;
    c = (c & 0x0F) << 4 | (c & 0xF0) >> 4;
    return c;
}

执行速度：查表法快于移位法，大约是移位法的80%。