掩蔽最显著位 [英] masking most significant bit

问题描述

我写此功能来消除最显著位的每一个字节。但这个功能似乎并不奏效，我想它是的方式。

I wrote this function to remove the most significant bit in every byte. But this function doesn't seem to be working the way I wanted it to be.

输出文件的大小始终是'0'，我不明白为什么什么也没有被写入到输出文件。有没有更好的和简单的方法来消除每一个字节？

The output file size is always '0', I don't understand why nothing's been written to the output file. Is there a better and simple way to remove the most significant bit in every byte??

推荐答案

，这种经历只有 1 位。 高（）如果参数为零返回参数的高位，或零。

Instead of going through all of the bits to find the high one, this goes through only the 1 bits. high() returns the high bit of the argument, or zero if the argument is zero.

inline int high(int n)
{
    int k;

    do {
        k = n ^ (n - 1);
        n &= ~k;
    } while (n);
    return (k + 1) >> 1;
}

inline int drop_high(int n)
{
    return n ^ high(n);
}

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