字段打包形成一个字节
我努力学习如何将四个独立的值打包成一个字节。 我试图得到一个十六进制输出0x91和二进制表示应该是10010001 ，而是我得到的输出： 0x1010001和16842753分别。 还是有更好的方法来做到这一点？
uint8_t globalColorTableFlag = 1;
uint8_t colorResolution = 001;
uint8_t sortFlag = 0;
uint8_t sizeOfGlobalColorTable = 001;
uint32_t packed = ((globalColorTableFlag << 24) | (colorResolution << 16) | (sortFlag << 8) | (sizeOfGlobalColorTable << 0));
NSLog(@"%d",packed); // Logs 16842753, should be: 10010001
NSLog(@"0x%02X",packed); // Logs 0x1010001, should be: 0x91
尝试以下操作：
/* 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，请参阅此答案：https://stackoverflow.com/a/17914633/4178025
对于按位操作，请参阅：https://stackoverflow.com/a/3427633/4178025
packed = ((globalColorTableFlag & 1) << 7) +
((colorResolution & 0x7) << 4) +
((sortFlag & 1) << 3) +
((sizeOfGlobalColorTable & 0x7);