什么是位运算符？ [英] What are bitwise operators?
问题描述
我是谁的人只是为了好玩写code和还没有真正钻研它要么是学术或专业设置，所以像这样的位运算符的东西真的逃脱我。
I'm someone who writes code just for fun and haven't really delved into it in either an academic or professional setting, so stuff like these bitwise operators really escapes me.
我在阅读关于JavaScript，这显然支持位运算的文章。我一直看到的地方提到这个操作，我已经试过阅读弄清楚它到底是什么，但我只是似乎没有得到它。因此，他们是什么？明显的例子将是巨大的！ ：D
I was reading an article about JavaScript, which apparently supports bitwise operations. I keep seeing this operation mentioned in places, and I've tried reading about to figure out what exactly it is, but I just don't seem to get it at all. So what are they? Clear examples would be great! :D
短短几年更多的问题 - 什么是位运算的一些实际应用？什么时候使用它们？
Just a few more questions - what are some practical applications of bitwise operations? When might you use them?
推荐答案
由于没有人开始讨论为什么这些都是有用的主题：
Since nobody has broached the subject of why these are useful:
我用旗时使用位运算了很多。例如，如果你要通过一系列标志来操作（例如，File.Open，具有读取模式和写入模式同时启用），你可以将它们作为单个值。这是由一个bitset（字节，短，int或long）分配每个可能的标志它自己的位来实现的。例如：
I use bitwise operations a lot when working with flags. For example, if you want to pass a series of flags to an operation (say, File.Open, with Read mode and Write mode both enabled), you could pass them as a single value. This is accomplished by assigning each possible flag it's own bit in a bitset (byte, short, int, or long). For example:
Read: 00000001
Write: 00000010
所以，如果你想通过读，写，你会通过（READ | WRITE），然后结合了两成
So if you want to pass read AND write, you would pass (READ | WRITE) which then combines the two into
00000011
，然后可以在另一端等来解密
Which then can be decrypted on the other end like:
if ((flag & Read) != 0) { //...
它检查
00000011 &
00000001
返回
00000001
这是不为0，所以标记并指定读
which is not 0, so the flag does specify READ.
您可以使用XOR来切换不同的位。我已经使用标志指定方向输入（上，下，左，右）时使用此。例如，如果一个精灵的水平移动，我想它转身：
You can use XOR to toggle various bits. I've used this when using a flag to specify directional inputs (Up, Down, Left, Right). For example, if a sprite is moving horizontally, and I want it to turn around:
Up: 00000001
Down: 00000010
Left: 00000100
Right: 00001000
Current: 00000100
我简单地异或电流值（LEFT | RIGHT），这将左转断，对上，在这种情况下
I simply XOR the current value with (LEFT | RIGHT) which will turn LEFT off and RIGHT on, in this case.
位移位是有用的几起案件。
Bit Shifting is useful in several cases.
x << y
是相同的
X * 2 是
如果您需要快速乘以二的幂，但要小心移1位到最高位 - 这使得消极的，除非它是无符号数。不同大小的数据打交道时也非常有用。例如，从四个字节读取的整数：
if you need to quickly multiply by a power of two, but watch out for shifting a 1-bit into the top bit - this makes the number negative unless it's unsigned. It's also useful when dealing with different sizes of data. For example, reading an integer from four bytes:
int val = (A << 24) | (B << 16) | (C << 8) | D;
假设A是最显著字节和D最少。这将最终为：
Assuming that A is the most-significant byte and D the least. It would end up as:
A = 01000000
B = 00000101
C = 00101011
D = 11100011
val = 01000000 00000101 00101011 11100011
颜色通常存储这种方式（具有最显著字节忽略或用作阿尔法）：
Colors are often stored this way (with the most significant byte either ignored or used as Alpha):
A = 255 = 11111111
R = 21 = 00010101
G = 255 = 11111111
B = 0 = 00000000
Color = 11111111 00010101 11111111 00000000
要再次找到的值，就在比特，直到它的底部移动到右边，则屏蔽掉剩余的高位比特
To find the values again, just shift the bits to the right until it's at the bottom, then mask off the remaining higher-order bits:
Int Alpha = Color >> 24
Int Red = Color >> 16 & 0xFF
Int Green = Color >> 8 & 0xFF
Int Blue = Color & 0xFF
0xFF的是相同的11111111所以基本上，对于红，你会做这样的：
0xFF is the same as 11111111. So essentially, for Red, you would be doing this:
Color >> 16 = (filled in 00000000 00000000)11111111 00010101 (removed 11111111 00000000)
00000000 00000000 11111111 00010101 &
00000000 00000000 00000000 11111111 =
00000000 00000000 00000000 00010101 (The original value)
这篇关于什么是位运算符？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
