反向字节 [英] reverse byte

问题描述

我试图反转一个字节，例如。

11010000应该看起来像

00001011

Plz注意，这不是作业问题而且我不需要c代码

。

请告诉我如何继续关于它。


我知道基本的位操作，左移，右移和已经完成

简单的问题，如计算1'等但这似乎没有to

点击给我。


谢谢。

Kapil

解决方案

" Kapil Khosla" < KH ********* @ yahoo.com>在留言中写道

news：91 ************************** @ posting.google.c om ...

我试图反转一个字节，例如。
11010000应该看起来像
00001011

Plz注意，它不是一个家庭作业问题，我不需要它的代码
。
请告诉我应该如何处理它。

我知道基本的位操作，左移，对，并做了简单的问题，如计数1'等，但这似乎没有点击给我。

谢谢。
Kapil

创建一个临时字节和AND与掩码0x1的原始字节，以查看是否

在LSB中为1。

如果有一个1然后OR 0x80到临时字节


现在和原始的0x2如果它是1然后OR的临时用0x4

等等。


HTH

Allan

Kapil Khosla< kh*********@yahoo.com>写道：

我试图反转一个字节，例如。
11010000应该看起来像
00001011

Plz注意，它这不是一个家庭作业问题，我不需要它的代码
。
请告诉我应该如何处理它。

最简单，最清晰，最有效的方法就是使用256个条目的

查询表。


- 凯文。

Kevin Easton写道：

Kapil Khosla< kh ********* @ yahoo.com>写道：
....

我试图反转一个字节，例如。
11010000应该看起来像是00001011

请注意，这不是一个家庭作业问题而且我不需要c代码
。
请告诉我如何处理它。

http：// graphics .stanford.edu / ~seander / bithacks.html

最简单，最清晰，最有效的方法就是使用256个条目的查找表。

这可能是真的。但它不是很有帮助。

如何生成查找表？你不会手工做，对吗？


Jirka

Hi,
I am trying to reverse a byte eg.
11010000 should look like
00001011

Plz note, it is not a homework problem and I do not need the c code
for it.
Just give me an idea how should I proceed about it.

I know basic bit manipulation , shifting left, right and have done
simple problems like counting 1''s etc but this one doesnt seem to
click to me.

Thanks.
Kapil

解决方案

"Kapil Khosla" <kh*********@yahoo.com> wrote in message
news:91**************************@posting.google.c om...

Hi,
I am trying to reverse a byte eg.
11010000 should look like
00001011

Plz note, it is not a homework problem and I do not need the c code
for it.
Just give me an idea how should I proceed about it.

I know basic bit manipulation , shifting left, right and have done
simple problems like counting 1''s etc but this one doesnt seem to
click to me.

Thanks.
Kapil

Create a temp Byte and AND the original byte with mask 0x1 to see if there
is a 1 in the LSB.
If there is a 1 then OR 0x80 to the temp byte

Now AND the original with 0x2 and if its a 1 then OR the temp with 0x4

And so on.

HTH
Allan

Kapil Khosla <kh*********@yahoo.com> wrote:

Hi,
I am trying to reverse a byte eg.
11010000 should look like
00001011

Plz note, it is not a homework problem and I do not need the c code
for it.
Just give me an idea how should I proceed about it.

The easiest, clearest and most efficient way is just to use a 256-entry
lookup table.

- Kevin.

Kevin Easton wrote:

Kapil Khosla <kh*********@yahoo.com> wrote: ....

I am trying to reverse a byte eg.
11010000 should look like
00001011

Plz note, it is not a homework problem and I do not need the c code
for it.
Just give me an idea how should I proceed about it.

http://graphics.stanford.edu/~seander/bithacks.html
The easiest, clearest and most efficient way is just to use a 256-entry
lookup table.

That might be true. But it''s not very helpful.
How is the lookup table generated? You wouldn''t do this by hand, would you?

Jirka

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