如何使用位掩码？ [英] How to use bitmask?

问题描述

如何在C ++中使用它？
什么时候使用有用？

请给我举一个使用bitmask的问题示例，它实际上是如何工作的。
谢谢！

How do i use it in C++ ? when is it useful to use ?
Please give me an example of a problem where bitmask is used , how it actually works . Thanks!

推荐答案

当您要存储（然后提取）不同的内容时，使用位掩码是有用的

Bit masking is "useful" to use when you want to store (and subsequently extract) different data within a single data value.

我以前使用的示例应用程序是假设您将彩色RGB值存储在16位值中。所以看起来像这样：

An example application I've used before is imagine you were storing colour RGB values in a 16 bit value. So something that looks like this:

RRRR RGGG GGGB BBBB

然后可以使用位掩码按如下方式检索颜色分量：

You could then use bit masking to retrieve the colour components as follows:

  const unsigned short redMask   = 0xF800;
  const unsigned short greenMask = 0x07E0;
  const unsigned short blueMask  = 0x001F;

  unsigned short lightGray = 0x7BEF;

  unsigned short redComponent   = (lightGray & redMask) >> 11;
  unsigned short greenComponent = (lightGray & greenMask) >> 5;
  unsigned short blueComponent =  (lightGray & blueMask);

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