C++ 将 std::wstring 转换为 WCHAR*
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Convert std::wstring to WCHAR*
提问by Jona
I have no idea how to convert a std::wstringto a WCHAR*
我不知道如何将 a 转换 std::wstring为 aWCHAR*
std::wstring wstrProcToSearch;
WCHAR * wpProcToSearch = NULL;
std::wcin >> wstrProcToSearch; // input std::wstring
// now i need to convert the wstring to a WCHAR*
Does anyone know how to accomplish this?
有谁知道如何做到这一点？
回答by Mr.C64
If you want to convert from std::wstringto const WCHAR*(i.e. the returned pointer gives read-only accessto the string content), then calling std::wstring::c_str()method is just fine:
如果你想从转换std::wstring到const WCHAR*（即返回指针表示只读访问字符串的内容），然后调用std::wstring::c_str()方法就好了：
std::wstring wstrProcToSearch;
std::wcin >> wstrProcToSearch; // input std::wstring
// Convert to const WCHAR* (read-only access)
const WCHAR * wpszProcToSearch = wstrProcToSearch.c_str();
Instead, if you want to modifystd::wstring's content, things are different. You can use &wstr[0](where wstris a non-empty instance of std::wstring) to access the content of the std::wstring(starting from the address of its first characters, and noting that characters are stored contiguously in memory), but you must pay attention to not overrun string's pre-allocated memory.
相反，如果你想修改std::wstring的内容，事情就不一样了。可以使用&wstr[0](where wstris an non-empty instance of std::wstring) 来访问内容std::wstring（从它的第一个字符的地址开始，注意字符在内存中是连续存储的），但一定要注意不要溢出字符串的 pre - 分配的内存。
In general, if you have a std::wstringof length L, you can access characters from index 0to (L-1).
Overwriting the terminating '\0'(located at index L) is undefined behavior(in practice, it's OK on Visual C++, at least with VC9/VS2008 and VC10/VS2010).
一般来说，如果你有一个std::wstring长度L，你可以访问从索引0到的字符(L-1)。
覆盖终止'\0'（位于 index L）是未定义的行为（实际上，在 Visual C++ 上是可以的，至少对于 VC9/VS2008 和 VC10/VS2010）。
If the string has not the proper size (i.e. it's not big enough for your needs), then you can call std::wstring::resize()to make room for new characters (i.e. resizing internal std::wstring's buffer), and then use &wstr[0]to read-write std::wstring's content.
如果字符串的大小不合适（即它不足以满足您的需要），那么您可以调用std::wstring::resize()为新字符腾出空间（即调整 internalstd::wstring的缓冲区大小），然后用于&wstr[0]读写std::wstring的内容。
回答by Mark Ransom
If the string is already the proper length and will not need to be changed, you can get a non-const pointer by taking a pointer to the first character:
如果字符串已经是正确的长度并且不需要更改，则可以通过获取指向第一个字符的指针来获得非常量指针：
WCHAR * wpProcToSearch = &wstrProcToSearch[0];
This is guaranteed to work in C++11 and there are no known implementations of C++03 where it doesn't.
这保证在 C++11 中工作，并且没有已知的 C++03 实现。
If you only need a const pointer you should use c_str:
如果你只需要一个 const 指针，你应该使用c_str：
const WCHAR * wpProcToSearch = wstrProcToSearch.c_str();
回答by Eric
I think you can use
我想你可以用
wpProcToSearch = wstrProcToSearch.c_str()
wpProcToSearch = wstrProcToSearch.c_str()
like you do with a normal std::string.
就像使用普通的 std::string 一样。
回答by Michael G?ttinger
I recommend this approach:
我推荐这种方法：
wstring str = L"Hallo x y 111 2222 3333 rrr 4444 ";
wchar_t* psStr = &str[0];
It is quite simple but you can not change the length of the string at all. So moving "\0" might not be valid...
这很简单，但您根本无法更改字符串的长度。所以移动 "\0" 可能无效......
