C++ 将窄字符串转换为宽字符串
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converting narrow string to wide string
提问by saplingPro
How can i convert a narrow stringto a wide string?
如何将窄转换string为宽string？
I have tried this method :
我试过这种方法：
string myName;
getline( cin , myName );
wstring printerName( L(myName) ); // error C3861: 'L': identifier not found
wchar_t* WprinterName = printerName.c_str(); // error C2440: 'initializing' : cannot convert from 'const wchar_t *' to 'wchar_t *'
But i get errors as listed above.
但是我得到了上面列出的错误。
Why do i get these errors ? How can i fix them ?
为什么我会收到这些错误？我该如何修复它们？
Is there any other method of directly converting a narrowstring to a widestring ?
有没有其他方法可以直接将narrow字符串转换为wide字符串？
回答by Blazes
If the source is ASCII encoded, you can just do this:
如果源是 ASCII 编码的，你可以这样做：
wstring printerName;
printerName.assign( myName.begin(), myName.end() );
回答by Christopher
You should do this :
你应该做这个 ：
inline std::wstring convert( const std::string& as )
{
// deal with trivial case of empty string
if( as.empty() ) return std::wstring();
// determine required length of new string
size_t reqLength = ::MultiByteToWideChar( CP_UTF8, 0, as.c_str(), (int)as.length(), 0, 0 );
// construct new string of required length
std::wstring ret( reqLength, L'inline std::wstring convert( const std::string& as )
{
wchar_t* buf = new wchar_t[as.size() * 2 + 2];
swprintf( buf, L"%S", as.c_str() );
std::wstring rval = buf;
delete[] buf;
return rval;
}
' );
// convert old string to new string
::MultiByteToWideChar( CP_UTF8, 0, as.c_str(), (int)as.length(), &ret[0], (int)ret.length() );
// return new string ( compiler should optimize this away )
return ret;
}
This expects the std::string to be UTF-8 (CP_UTF8), when you have another encoding replace the codepage.
这期望 std::string 为 UTF-8 ( CP_UTF8)，当您有另一种编码替换代码页时。
Another way could be :
另一种方法可能是：
std::string str = "Hello";
std::wstring str2(str.length(), L' '); // Make room for characters
// Copy string to wstring.
std::copy(str.begin(), str.end(), str2.begin());
回答by ólafur Waage
I found thiswhile googling the problem. I have pasted the code for reference. Author of this post is Paul McKenzie.
我在谷歌搜索问题时发现了这一点。我已经粘贴了代码以供参考。这篇文章的作者是保罗·麦肯齐。
#include <atlbase.h>
std::wstring wideString(L"My wide string");
std::string narrowString("My not-so-wide string");
ATL::CW2A narrow(wideString.c_str()); // narrow is a narrow string
ATL::CA2W wide(asciiString.c_str()); // wide is a wide string
回答by Alex
ATL (non-express editions of Visual Studio) has a couple useful class types which can convert the strings plainly. You can use the constructor directly, if you do not need to hold onto the string.
ATL（Visual Studio 的非快速版本）有几个有用的类类型，可以简单地转换字符串。如果不需要保留字符串，则可以直接使用构造函数。
errno_t wcstombs_s(
size_t *pReturnValue,
char *mbstr,
size_t sizeInBytes,
const wchar_t *wcstr,
size_t count
);
errno_t mbstowcs_s(
size_t *pReturnValue,
wchar_t *wcstr,
size_t sizeInWords,
const char *mbstr,
size_t count
回答by eddyq
Here are two functions that can be used: mbstowcs_s and wcstombs_s.
这里有两个可以使用的函数：mbstowcs_s 和 wcstombs_s。
mbstowcs_s: Converts a sequence of multibyte characters to a corresponding sequence of wide characters. wcstombs_s: Converts a sequence of wide characters to a corresponding sequence of multibyte characters.
mbstowcs_s：将多字节字符序列转换为相应的宽字符序列。wcstombs_s：将宽字符序列转换为相应的多字节字符序列。
// wchar_t* wstr = L"A wide string"; // Error: cannot convert from 'const wchar_t *' to 'wchar_t *'
wchar_t const* wstr = L"A wide string"; // okay
const wchar_t* wstr_equivalent = L"A wide string"; // also okay
);
);
See http://msdn.microsoft.com/en-us/library/eyktyxsx.aspxand http://msdn.microsoft.com/en-us/library/s7wzt4be.aspx.
请参阅http://msdn.microsoft.com/en-us/library/eyktyxsx.aspx和http://msdn.microsoft.com/en-us/library/s7wzt4be.aspx。
回答by Indinfer
The original question of this thread was: "How can i convert a narrow string to a wide string?"
该线程的原始问题是：“如何将窄字符串转换为宽字符串？”
However, from the example code given in the question, there seems to be no conversion necessary. Rather, there is a compiler error due to the newer compilers deprecating something that used to be okay. Here is what I think is going on:
但是，从问题中给出的示例代码来看，似乎没有必要进行转换。相反，由于较新的编译器弃用了曾经没问题的东西，因此存在编译器错误。这是我认为正在发生的事情：
string myName;
wchar_t wstr[BUFFER_SIZE];
getline( cin , myName );
mbtowc(wstr, myName, BUFFER_SIZE);
The c_str() seems to be treated the same as a literal, and is considered a constant (const). You could use a cast. But preferable is to add const.
c_str() 似乎被视为与文字相同，并被视为常量 (const)。你可以使用演员表。但最好是添加const。
The best answer I have seen for converting between wide and narrow strings is to use std::wstringstream. And this is one of the answers given to C++ Convert string (or char*) to wstring (or wchar_t*)
我见过的在宽字符串和窄字符串之间转换的最佳答案是使用 std::wstringstream。这是C++ Convert string (or char*) to wstring (or wchar_t*)的答案之一
You can convert most anything to and from strings and wide strings using stringstream and wstringstream.
您可以使用 stringstream 和 wstringstream 将大多数内容与字符串和宽字符串相互转换。
回答by ravenspoint
The Windows API provides routines for doing this: WideCharToMultiByte() and MultiByteToWideChar(). However, they are a pain to use. Each conversion requires two calls to the routines and you have to look after allocating/freeing memory and making sure the strings are correctly terminated. You need a wrapper!
Windows API 提供了执行此操作的例程：WideCharToMultiByte() 和 MultiByteToWideChar()。但是，它们使用起来很痛苦。每次转换都需要对例程进行两次调用，您必须注意分配/释放内存并确保字符串正确终止。你需要一个包装！
I have a convenient C++ wrapper on my blog, here, which you are welcome to use.
我的博客上有一个方便的 C++ 包装器，这里，欢迎您使用。
回答by Mr.C64
This articlepublished on the MSDN Magazine 2016 September issue discusses the conversion in details using Win32 APIs.
发表在 MSDN 杂志 2016 年 9 月号上的这篇文章详细讨论了使用 Win32 API 的转换。
Note that using MultiByteToWideChar()is much fasterthan using the std:: stuff on Windows.
请注意，使用MultiByteToWideChar()是要快得多比在Windows上使用的std ::东西。
回答by Simon Rigét
Use mbtowc():
使用mbtowc()：
##代码##