[英]Redirect from a std::ostringstream to another std::ostringstream
I need write data from some std::ostringstream
to another std::ostringstream
. 我需要将一些std::ostringstream
数据写入另一个std::ostringstream
。 Of course, I can use str()
function 当然,我可以使用str()
函数
std::ostringstream in;
std::ostringstream out;
in << "just a test"; // it's just an example. I mean that stream in is filled somewhere
...
out << in.str();
I'd like to know if there is more direct way to do the same. 我想知道是否有更直接的方法来做同样的事情。
You can reassign the associated buffers: 您可以重新分配关联的缓冲区:
os2.rdbuf(os1.rdbuf());
That effectively aliases the ostream. 这有效地使ostream混淆。
In fact, you can even construct ostream
directly from a streambuffer pointer IIRC 实际上,您甚至可以直接从streambuffer指针IIRC构造ostream
Similarly, you can append the whole buffer to another stream without reassigning: 同样,您可以将整个缓冲区附加到另一个流而不重新分配:
std::cout << mystringstream.rdbuf(); // prints the stringstream to console
The copy assignment operator/copy constructor are deleted. 复制赋值运算符/复制构造函数将被删除。 However, you can use the member function swap
(C++11), or std::swap
, to swap the content. 但是,您可以使用成员函数swap
(C ++ 11)或std::swap
来交换内容。 Or, you can use the move assignment operator (C++11) to move one into the other. 或者,您可以使用移动赋值运算符(C ++ 11)将一个移动到另一个。 This solution works only in the case when you don't care about the content of the source stringstream. 此解决方案仅适用于您不关心源字符串流的内容的情况。
Example: 例:
out = std::move(in); // C++11
out.swap(in); // C++11
std::swap(out, in);
PS: I just realized that g++ does not compile any of the above lines (it seems it doesn't support move/swap for ostringstream), however, clang++ compiles it. PS:我刚刚意识到g ++没有编译上面的任何一行(似乎它不支持ostringstream的move / swap),但是,clang ++编译它。 According to the standard (27.8.4), swap/move should work. 根据标准(27.8.4),交换/移动应该有效。 See C++ compiler does not recognize std::stringstream::swap 请参阅C ++编译器无法识别std :: stringstream :: swap
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