如何使用位掩码? [英] How to use bitmask?
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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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