如何检查c中的位设置？ [英] How to check how a bit is set in c?

问题描述

How to check a bit in a variable whether it is set or not using C language

推荐答案

与CP的答案相关：

Related to CP''s answer:

#define bit_set(val, bit_no) (((val) >> (bit_no)) & 1)

这个数字位从（n-1）到0从高值位到低位，即a short 最低位（值1）是位号0，最高位（值32768）是数字15.

This numbers bits from (n-1) to 0 from the high value bits to the low, i.e. in a short the lowest bit (value 1) is bit number 0, and the highest (value 32768) is number 15.

（例如）使用 shift 和按位和，例如

(For instance) With a shift and a bitwise and, e.g.

// check if bit 5 is set
if ( (val >> 5) & 1)
{
  // bit is set
}
else
{
  // bit unset
}

上面列出的解决方案适用于非结构化测试。如果您从头开始设计系统，并且您知道算法的数据结构需要检查位，那么您应该调查位字段的使用。



http://en.wikipedia.org/wiki/Bit_field [ ^ ]

The solutions listed above are good for unstructured testing. If you are designing a system from scratch and you know that the data structure for your algorithm is going to need to check bits then you should investigate the use of bit fields.

http://en.wikipedia.org/wiki/Bit_field[^]

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