転載-C言語<<、>>、＆、|実用

 

C言語<<、>>、＆、|実用

他の人がプロジェクトを参照するか、サードパーティのライブラリのソースコードを参照しながら、あなたは、多くの場合、子供の靴のいくつかの新規参入のため、このようなA >> 4＆0x0Fに、このような文言が表示されることが開発者として、それはかなり何この意味を理解しないかもしれません。ここでは、これらの演算子の実用化を説明する必要があります。

 

まず、意味のオペレータ

演算子	意味	説明
<<	左	すべてのNビット左シフト、高い廃棄、低0のビット数のそれぞれについて。
>>	右	数の各Nビットのバイナリビット右、低の右端に符号なしの数、ハイ0ため、破棄されます。
＆	ビットAND	対応する二つのビットが1である場合、ビットの結果は1であり、そうでなければ0。
リットル	ビットごとのOR	2つのそれぞれのビット限り1が存在するように、結果は、他の1ビット、及び0です。

第二に、使用

の使用によるビット

1.クリア

メモリセルが消去されるため、全体のビットが0である場合であってもあれば、メモリセルの電流値は、両方（すなわち、元の番号が0,0である1になる）ようにネゲート＆演算子を実行するには、明確な目標を達成することができます。
例えば23 =、B =〜 ：

<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">a<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:00010111
<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">b<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:11101000
a&<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">b<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:00000000
<span aria-hidden="true" class="line-numbers-rows" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">

ビットの特定の指定された数を取る2。

例えば、4 1 0は、ビットbの数になった後、= 23、Iはバック4桁のバイナリを利用したいと思い、あなたは残りの部分を見つけることができる、すなわちB = 0x0Fの（16進、バイナリを00001111に変換されます） 、＆​​bが最後の4を取得します。

<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">a<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:00010111
<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">b<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:00001111
a&<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">b<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:00000111
<span aria-hidden="true" class="line-numbers-rows" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">

3.指定されたビットを残します

例えば、= 23（8ビットで表される）、私は、そのバイナリビット4,6（左端のビットが1である）、休止位置0を維持したいです。あなたが4見つけることができ、及び図6は、0 B残りのビットの数とビット単位のAND演算であります

<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">a<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:00010111
<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">b<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:00010100
a&<span class="token property" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">b<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">:00010100
<span aria-hidden="true" class="line-numbers-rows" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">

位置またはを使用することにより

一般的に図1は、位置の特定の数の他のビットは変化しない、使用しました。例えば、A = 23、Iは、その第二及び第三の位置1,2したい、3ビット1を残りの部分に場所を見つけることができ、0またはビット単位操作の数です。

a:00010111
b:01100000
a|b:01110111
<span aria-hidden="true" class="line-numbers-rows" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">

第三に、プロジェクトの例

在实际项目中，很多时候&和|都是和>>、<<配合使用的。比如在蓝牙项目开发中，2个设备之间进行日期数据传输时，我们先定一个协议，用4个byte来表示一个日期，其中byte0表示年份的高位数，byte1表示年份的低位数，byte2表示月份，byte3表示日期。
设备端现在收到另外一台设备传过来的日期数据00010100 00010011 00000110 00011101（为了阅读方便我将每个byte之间用空格分开）。那么我要如何解析这个数据来得到实际日期呢？

<span class="token comment" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">/* 
*第一步，获取日期。
*日期是最后一个byte，也就是最后8位，用一个后8位是1其余位是0的数(11111111,十六进制表示是0xff)与数据进行按位与计算即可
*/
date <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">= <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010100 <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010011 <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00000110 <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00011101<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">;
day <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">= date <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">& <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">0xff<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">;<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">(计算结果是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00011101，十进制表示是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">29，也就是日期是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">29<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">)。

<span class="token comment" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">/* 
*第二步，获取月份。
*月份是倒数第2个byte，此时需要先将最后一个byte砍掉(也就是右移8位)，然后再和0xff进行按位与运算
*下面代码可以简写成date=date>>8&0xff;
*/
date <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">= date<span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">>><span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">8<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">; <span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">(计算结果是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010100 <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010011 <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00000110<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">)
month <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">= date <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">& <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">0xff<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">;<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">(计算结果是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00000110，十进制表示是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">6，也就是月份是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">6月<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">)。

<span class="token comment" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">/* 
*第三步，获取年份低位。
*先将最后一个byte砍掉(也就是右移8位)，然后再和0xff进行按位与运算
*下面代码可以简写成date=date>>8&0xff;
*/
date <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">= date<span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">>><span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">8<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">; <span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">(计算结果是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010100 <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010011<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">)
year_low <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">= date <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">& <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">0xff<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">;<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">(计算结果是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010011，十进制表示是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">19<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">)。

<span class="token comment" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">/* 
*第四步，获取年份高位。
*先将最后一个byte砍掉(也就是右移8位)，然后再和0xff进行按位与运算
*下面代码可以简写成date=date>>8&0xff;
*/
date <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">= date<span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">>><span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">8<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">; <span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">(计算结果是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010100<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">)
year_heigh <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">= date <span class="token operator" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">& <span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">0xff<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">;<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">(计算结果是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">00010011，十进制表示是<span class="token number" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">20<span class="token punctuation" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">)。
<span aria-hidden="true" class="line-numbers-rows" style="font-size: inherit; color: inherit; line-height: inherit; margin: 0px; padding: 0px; word-wrap: inherit !important; word-break: inherit !important;">

最后将4个数拼起来就得到日期为2019年6月29日。