const_cast，reinterpret_cast [英] const_cast, reinterpret_cast
问题描述
有人可以给我一些很好的参考网站/信息
了解何时以及为什么我会使用
1.）const_cast
不知道你为什么会这样做？
2.）reinterpret_cast。
当我转换一个时我用了一点原始到一个类，但是
希望看到其他应用程序。
是的，我已经在网上看了，但是想知道一些什么的专家
了解这一点。
非常感谢您的帮助，
John
Can someone please give me some good reference site/information for
understanding when and why I would use
1.) const_cast
Don''t know why you would do this?
2.) reinterpret_cast.
I have used this a little when I converted a primitive to a class, but
would like to see other applications.
Yes, I have looked on the web, but want to know what some of the experts
know about this.
Thanks alot for your help,
John
推荐答案
johny smith写道：
johny smith wrote:
有人可以给我一些很好的参考网站/信息，以便了解何时和为什么我会用
1.）const_cast
不知道你为什么会这样做？
Can someone please give me some good reference site/information for
understanding when and why I would use
1.) const_cast
Don''t know why you would do this?
我''我需要使用它来在连接不良时插入常量
写入inte将参数视为const的rfaces，但在参数列表中没有将其限定为
const。
I''ve had need to use this to cast away constness when interfacing w/ poorly
written interfaces that treat a parameter as const, but don''t qualify it as
const in the parameter list.
" johny smith" < PR ************** @ charter.net>在消息中写道
新闻：10 ************* @ corp.supernews.com ...
"johny smith" <pr**************@charter.net> wrote in message
news:10*************@corp.supernews.com...
有人可以给我一些良好的参考网站/信息，了解我何时以及为何使用
1.）const_cast
不知道为什么要这样做？
这是从const转换为非const。
2.）reinterpret_cast。
当我使用时，我已经使用了一点将原语转换为类，但
希望看到其他应用程序。
Can someone please give me some good reference site/information for
understanding when and why I would use
1.) const_cast
Don''t know why you would do this?
It''s for casting from const to non-const.
2.) reinterpret_cast.
I have used this a little when I converted a primitive to a class, but
would like to see other applications.
您可以使用它来转换不兼容的类型，例如，
unsigned char buffer [20];
if（read_message_from_com_port（buffer））
{
double x = * reinterpret_cast< double *>（缓冲区）;
// ...
}
根据经验，使用reinterpret_cast if没有隐式转换
和static_cast被编译器拒绝 - 而且你确定
它是你需要的转换。
如果你无法找到这些演员阵容的用途，那么算上你的祝福。
没有人_wants_使用它们。它们应该尽可能少地使用，但是有时你必须使用它们才能使用它们。
DW
You use it to convert between incompatible types, e.g.,
unsigned char buffer[20];
if(read_message_from_com_port(buffer))
{
double x = *reinterpret_cast<double*>(buffer);
//...
}
As a rule of thumb, use reinterpret_cast if there is no implicit conversion
and static_cast is rejected by the compiler - and you are really sure that
it''s the conversion you need.
If you are unable to find uses for these casts, then count your blessings.
No one _wants_ to use them. They should be used as little as possible, but
sometimes you have to use to use them.
DW
" johny smith" < PR ************** @ charter.net>在消息中写道
"johny smith" <pr**************@charter.net> wrote in message
1.）const_cast
不知道为什么要这样做？
如果你实现了const函数，你就可以实现nonconst函数
的非结果函数。
const T& Foo :: stuff（）const {
/ *很多代码* /
}
T& Foo :: stuff（）{
const Foo * cthis = this;
返回const_cast< T&>（cthis-> stuff）;
}
另外，你需要const_cast来添加第二级const。虽然这很少使用
。
int main（int argc，char * * argv）{
char const * const * cargv = const_cast< char const * const *>（argv）;
};
你还需要const_cast来处理那些' 't const
正确，例如使用变量as const而不是声明它为const，因为
Julie指出。
2.） reinterpret_cast。
当我将一个原语转换为一个类时，我已经习惯了这个，但
希望看到其他应用程序。
1.) const_cast
Don''t know why you would do this?
If you implement the const function, you can implement the nonconst function
in terms of the nonconst one.
const T& Foo::stuff() const {
/* lots of code */
}
T& Foo::stuff() {
const Foo * cthis = this;
return const_cast<T&>(cthis->stuff);
}
Also, you need const_cast to add 2nd level const. Though this is rarely
used.
int main(int argc, char * * argv) {
char const *const * cargv = const_cast<char const *const *>(argv);
};
And you also need const_cast to deal with interfaces that aren''t const
correct, for example using a variable as const by not declaring it const, as
Julie points out.
2.) reinterpret_cast.
I have used this a little when I converted a primitive to a class, but
would like to see other applications.
一个可以使用它将int，double等转换为字节流，适合
用于写入调用。
int i = 3;
cout.write（reinterpret_cast< const char *>（& i），sizeof（i））;
在池分配器方案中，我们分配空间存储N个元素，比如N =
100.您可以将元素的空间视为元素或指针
t o下一个元素，前提是空格的大小是> =
指向元素的空间。
还有很多其他的域名具体例子。
One can use it to convert an int, double, etc to a stream of bytes, suitable
for a call to write.
int i = 3;
cout.write(reinterpret_cast<const char *>(&i), sizeof(i));
In pool allocator schemes, we allocate space to store N elements, say N =
100. You can treat the space of element as either an element or a pointer
to the next element, provided that the sizeof the space is >= the space of a
pointer to the element.
There are lots of other domain specific examples.
这篇关于const_cast，reinterpret_cast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！
