访问整数的单个字节 [英] Accessing individual bytes of an integer
问题描述
您好！
我想处理单个字节的整数。我知道整数是
32位且永远都是。有时我想使用32位的整个
，有时我想修改
示例的前8位。对我来说，我认为最好能够像这样声明32位
：
unsigned char bits [4];
当我想把它当作一个32位整数时，我可以做一些这样的事情
吗？
unsigned int bits32 = *（（unsigned int *）bits）;
我不确定语法。我不需要就地工作。使用副本可以获得
罚款。
提前致谢！
-
Daniel
Hello!
I want to work with individual bytes of integers. I know that ints are
32-bit and will always be. Sometimes I want to work with the entire
32-bits, and other times I want to modify just the first 8-bits for
example. For me, I think it would be best if I can declare the 32-bits
like this:
unsigned char bits[4];
When I want to treat this as a 32-bits integer, can I do something
like this?
unsigned int bits32 = *((unsigned int*)bits);
I''m unsure of the syntax. I don''t need to work in-place so to speak. It is
fine to work with a copy.
Thanks in advance!
--
Daniel
推荐答案
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当我想把它当作一个32位整数时，我可以这样做吗？
unsigned int bits32 = *（（unsigned int *）bits）;
When I want to treat this as a 32-bits integer, can I do something
like this?
unsigned int bits32 = *((unsigned int*)bits);
是的，你可以，但你绝对不能保证结果是什么结果
将是:-)
（位>> n）& 0xff
其中n是0,8,16或24？
Yes you can, but you have absolutely no assurance as to what the results
will be :-)
What''s wrong with
(bits>>n) & 0xff
where n is 0, 8, 16, or 24?
" Daniel Lidstr？m <所以***** @ microsoft.com> ????
新闻：pa **************************** @ microsoft.com。 ..
"Daniel Lidstr?m" <so*****@microsoft.com> ????
news:pa****************************@microsoft.com. ..
你好！
我想处理单个字节的整数。我知道这些内容是32位的，并且永远都是。有时我想使用整个
32位，有时我想修改
示例的前8位。对我来说，我认为最好能宣布这样的32位
unsigned char bits [4];
当我想要的时候把它当作一个32位整数，我可以这样做吗？
unsigned int bits32 = *（（unsigned int *）bits）;
我不确定语法。我不需要就地工作。使用副本是好的。
提前致谢！
-
Daniel
Hello!
I want to work with individual bytes of integers. I know that ints are
32-bit and will always be. Sometimes I want to work with the entire
32-bits, and other times I want to modify just the first 8-bits for
example. For me, I think it would be best if I can declare the 32-bits
like this:
unsigned char bits[4];
When I want to treat this as a 32-bits integer, can I do something
like this?
unsigned int bits32 = *((unsigned int*)bits);
I''m unsure of the syntax. I don''t need to work in-place so to speak. It is
fine to work with a copy.
Thanks in advance!
--
Daniel
无需考虑字节顺序，你是对的。
更好的方法是使用像这样的联盟：
union xxx
{
unsigned char bits [4];
unsigned int i;
};
Unconsidering the byte sequence, you are correct.
A better way is using a union like:
union xxx
{
unsigned char bits[4];
unsigned int i;
};
MatrixV写道：
MatrixV wrote:
" Daniel Lidstr？m" <所以***** @ microsoft.com> ????
新闻：pa **************************** @ microsoft.com。 ..
"Daniel Lidstr?m" <so*****@microsoft.com> ????
news:pa****************************@microsoft.com. ..
你好！
我想处理单个字节的整数。我知道这些内容是32位的，并且永远都是。有时我想使用整个
32位，有时我想修改
示例的前8位。对我来说，我认为最好能宣布这样的32位
unsigned char bits [4];
当我想要的时候把它当作一个32位整数，我可以这样做吗？
unsigned int bits32 = *（（unsigned int *）bits）;
我不确定语法。我不需要就地工作。使用副本是好的。
提前致谢！
-
Daniel
Hello!
I want to work with individual bytes of integers. I know that ints are
32-bit and will always be. Sometimes I want to work with the entire
32-bits, and other times I want to modify just the first 8-bits for
example. For me, I think it would be best if I can declare the 32-bits
like this:
unsigned char bits[4];
When I want to treat this as a 32-bits integer, can I do something
like this?
unsigned int bits32 = *((unsigned int*)bits);
I''m unsure of the syntax. I don''t need to work in-place so to speak. It is
fine to work with a copy.
Thanks in advance!
--
Daniel
无需考虑字节序列，你是对的。
更好的方法是使用如下的联合：
union xxx
{
unsigned char bits [4];
unsigned int i;
};
Unconsidering the byte sequence, you are correct.
A better way is using a union like:
union xxx
{
unsigned char bits[4];
unsigned int i;
};
怎么样：
union xxx
{
unsigned char bytes [sizeof（unsigned int））];
unsigned int i;
};
这不假设整数中有多少字节是
。
-
Thomas Matthews
C ++新闻组欢迎信息：
http： //www.slack.net/~shiva/welcome.txt
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其他网站：
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How about this:
union xxx
{
unsigned char bytes[sizeof(unsigned int))];
unsigned int i;
};
This makes no assumptions about how many bytes are
in an integer.
--
Thomas Matthews
C++ newsgroup welcome message:
http://www.slack.net/~shiva/welcome.txt
C++ Faq: http://www.parashift.com/c++-faq-lite
C Faq: http://www.eskimo.com/~scs/c-faq/top.html
alt.comp.lang.learn.c-c++ faq:
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Other sites:
http://www.josuttis.com -- C++ STL Library book
http://www.sgi.com/tech/stl -- Standard Template Library
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