字段打包以形成单个字节

Question

我正在努力学习如何将四个单独的值打包成一个字节。我试图获得0x91的十六进制输出，二进制表示应该是10010001，而是我得到的输出：0x1010001和{{1 }} 分别。或者有更好的方法吗？

16842753

Answer 1

尝试以下方法：

/* packed starts at 0 */
uint8_t packed = 0;

/* one bit of the flag is kept and shifted to the last position */
packed |= ((globalColorTableFlag & 0x1) << 7);
/* three bits of the resolution are kept and shifted to the fifth position */
packed |= ((colorResolution & 0x7) << 4);
/* one bit of the flag is kept and shifted to the fourth position */
packed |= ((sortFlag & 0x1) << 3);
/* three bits are kept and left in the first position */
packed |= ((sizeOfGlobalColorTable & 0x7) << 0);

有关十六进制和二进制数字之间关系的解释，请参阅以下答案：https://stackoverflow.com/a/17914633/4178025

对于按位操作，请参阅：https://stackoverflow.com/a/3427633/4178025

Answer 2

packed = ((globalColorTableFlag & 1) << 7) +
    ((colorResolution & 0x7) << 4) +
    ((sortFlag & 1) << 3) +
    ((sizeOfGlobalColorTable & 0x7);