如何将wstring转换为u16string? [英] how can I convert wstring to u16string?

问题描述

我想在C ++中将wstring转换为u16string.

I want to convert wstring to u16string in C++.

我可以将wstring转换为字符串，也可以反向转换.但是我不知道如何转换为u16string.

I can convert wstring to string, or reverse. But I don't know how convert to u16string.

u16string CTextConverter::convertWstring2U16(wstring str)

{

        int iSize;
        u16string szDest[256] = {};
        memset(szDest, 0, 256);
        iSize = WideCharToMultiByte(CP_UTF8, NULL, str.c_str(), -1, NULL, 0,0,0);

        WideCharToMultiByte(CP_UTF8, NULL, str.c_str(), -1, szDest, iSize,0,0);
        u16string s16 = szDest;
        return s16;
}

WideCharToMultiByte(CP_UTF8，NULL，str.c_str()，-1，szDest，iSize，0,0);中的错误szDest. u16string的原因不能与LPSTR一起使用.

Error in WideCharToMultiByte(CP_UTF8, NULL, str.c_str(), -1, szDest, iSize,0,0);'s szDest. Cause of u16string can't use with LPSTR.

如何解决此代码?

推荐答案

有关与平台无关的解决方案，请参见这个答案.

For a platform-independent solution see this answer.

如果仅需要 Windows平台的解决方案，则下面的代码就足够了:

If you need a solution only for the Windows platform, the following code will be sufficient:

std::wstring wstr( L"foo" );
std::u16string u16str( wstr.begin(), wstr.end() );

在Windows平台上，std::wstring可与std::u16string互换，因为sizeof(wstring::value_type) == sizeof(u16string::value_type)且两者都是UTF-16(小尾数)编码的.

On the Windows platform, a std::wstring is interchangeable with std::u16string because sizeof(wstring::value_type) == sizeof(u16string::value_type) and both are UTF-16 (little endian) encoded.

wstring::value_type = wchar_t
u16string::value_type = char16_t

唯一的区别是wchar_t是带符号的，而char16_t是无符号的，因此您只需要进行符号转换，可以使用将迭代器对作为参数的w16string构造函数来执行.此构造函数会将wchar_t隐式转换为char16_t.

The only difference being that wchar_t is signed, whereas char16_t is unsigned so you only have to do sign conversion, which can be performed using the w16string constructor that takes an iterator pair as arguments. This constructor will implicitly convert wchar_t to char16_t.

完整的示例控制台应用程序:

Full example console application:

#include <windows.h>
#include <string>

int main()
{
    static_assert( sizeof(std::wstring::value_type) == sizeof(std::u16string::value_type),
        "std::wstring and std::u16string are expected to have the same character size" );

    std::wstring wstr( L"foo" );
    std::u16string u16str( wstr.begin(), wstr.end() );

    // The u16string constructor performs an implicit conversion like:
    wchar_t wch = L'A';
    char16_t ch16 = wch;

    // Need to reinterpret_cast because char16_t const* is not implicitly convertible
    // to LPCWSTR (aka wchar_t const*).
    ::MessageBoxW( 0, reinterpret_cast<LPCWSTR>( u16str.c_str() ), L"test", 0 );

    return 0;
}

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