我有一个 Windows 应用程序，其中字符串类型是 WCHAR*。我需要将其转换为 char* 以传递到 C API。我正在使用 MultiByteToWideChar 和 WideCharToMultiByte 函数来执行转换。

但由于某些原因，转换不正确。我在输出中看到很多乱码。以下代码是在 this 中找到的修改版本计算器答案。

WCHAR* convert_to_wstring(const char* str)
{
    int size_needed = MultiByteToWideChar(CP_UTF8, 0, str, (int)strlen(str), NULL, 0);
    WCHAR* wstrTo = (WCHAR*)malloc(size_needed);
    MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)strlen(str), wstrTo, size_needed);
    return wstrTo;
}

char* convert_from_wstring(const WCHAR* wstr)
{
    int size_needed = WideCharToMultiByte(CP_UTF8, 0, wstr, (int)wcslen(wstr), NULL, 0, NULL, NULL);
    char* strTo = (char*)malloc(size_needed);
    WideCharToMultiByte(CP_UTF8, 0, wstr, (int)wcslen(wstr), strTo, size_needed, NULL, NULL);
    return strTo;
}

int main()
{
    const WCHAR* wText = L"Wide string";
    const char* text = convert_from_wstring(wText);
    std::cout << text << "\n";
    std::cout << convert_to_wstring("Multibyte string") << "\n";
    return 0;
}

最佳答案

您的转换函数有问题。

MultiByteToWideChar()的返回值是一个宽字符数，而不是像您当前正在处理的字节数。您需要将值乘以 sizeof(WCHAR)打电话时 malloc() .

您也没有考虑到返回值不包含空终止符的空间，因为您没有传递 -1在cbMultiByte范围。 Read the MultiByteToWideChar() documentation :

cbMultiByte [in]
Size, in bytes, of the string indicated by the lpMultiByteStr parameter. Alternatively, this parameter can be set to -1 if the string is null-terminated. Note that, if cbMultiByte is 0, the function fails.

If this parameter is -1, the function processes the entire input string, including the terminating null character. Therefore, the resulting Unicode string has a terminating null character, and the length returned by the function includes this character.

If this parameter is set to a positive integer, the function processes exactly the specified number of bytes. If the provided size does not include a terminating null character, the resulting Unicode string is not null-terminated, and the returned length does not include this character.

...

Return value

Returns the number of characters written to the buffer indicated by lpWideCharStr if successful. If the function succeeds and cchWideChar is 0, the return value is the required size, in characters, for the buffer indicated by lpWideCharStr.

您没有以 null 终止输出字符串。

您的 convert_from_wstring() 也是如此功能。 Read the WideCharToMultiByte() documentation :

cchWideChar [in]
Size, in characters, of the string indicated by lpWideCharStr. Alternatively, this parameter can be set to -1 if the string is null-terminated. If cchWideChar is set to 0, the function fails.

If this parameter is -1, the function processes the entire input string, including the terminating null character. Therefore, the resulting character string has a terminating null character, and the length returned by the function includes this character.

If this parameter is set to a positive integer, the function processes exactly the specified number of characters. If the provided size does not include a terminating null character, the resulting character string is not null-terminated, and the returned length does not include this character.

...

Return value

Returns the number of bytes written to the buffer pointed to by lpMultiByteStr if successful. If the function succeeds and cbMultiByte is 0, the return value is the required size, in bytes, for the buffer indicated by lpMultiByteStr.

也就是说，您的 main()代码正在泄漏分配的字符串。因为它们分配有 malloc() ，您需要使用 free() 解除分配它们当你用完它们时:

此外，您不能传递 WCHAR*字符串到 std::cout .好吧，你可以，但它没有 operator<<用于宽字符串输入，但它确实有一个 operator<<对于 void*输入，所以它最终只会输出 WCHAR* 的内存地址指的是，而不是实际的字符。如果要输出宽字符串，请使用 std::wcout相反。

尝试更像这样的东西:

WCHAR* convert_to_wstring(const char* str)
{
    int str_len = (int) strlen(str);
    int num_chars = MultiByteToWideChar(CP_UTF8, 0, str, str_len, NULL, 0);
    WCHAR* wstrTo = (WCHAR*) malloc((num_chars + 1) * sizeof(WCHAR));
    if (wstrTo)
    {
        MultiByteToWideChar(CP_UTF8, 0, str, str_len, wstrTo, num_chars);
        wstrTo[num_chars] = L'\0';
    }
    return wstrTo;
}

CHAR* convert_from_wstring(const WCHAR* wstr)
{
    int wstr_len = (int) wcslen(wstr);
    int num_chars = WideCharToMultiByte(CP_UTF8, 0, wstr, wstr_len, NULL, 0, NULL, NULL);
    CHAR* strTo = (CHAR*) malloc((num_chars + 1) * sizeof(CHAR));
    if (strTo)
    {
        WideCharToMultiByte(CP_UTF8, 0, wstr, wstr_len, strTo, num_chars, NULL, NULL);
        strTo[num_chars] = '\0';
    }
    return strTo;
}

int main()
{
    const WCHAR* wText = L"Wide string";
    const char* text = convert_from_wstring(wText);
    std::cout << text << "\n";
    free(text);

    const WCHAR *wtext = convert_to_wstring("Multibyte string");
    std::wcout << wtext << "\n";
    free(wtext);

    return 0;
}

话虽这么说，你真的应该使用 std::string和 std::wstring而不是 char*和 wchar_t*为了更好的内存管理:

std::wstring convert_to_wstring(const std::string &str)
{
    int num_chars = MultiByteToWideChar(CP_UTF8, 0, str.c_str(), str.length(), NULL, 0);
    std::wstring wstrTo;
    if (num_chars)
    {
        wstrTo.resize(num_chars);
        MultiByteToWideChar(CP_UTF8, 0, str.c_str(), str.length(), &wstrTo[0], num_chars);
    }
    return wstrTo;
}

std::string convert_from_wstring(const std::wstring &wstr)
{
    int num_chars = WideCharToMultiByte(CP_UTF8, 0, wstr.c_str(), wstr.length(), NULL, 0, NULL, NULL);
    std::string strTo;
    if (num_chars > 0)
    {
        strTo.resize(num_chars);
        WideCharToMultiByte(CP_UTF8, 0, wstr.c_str(), wstr.length(), &strTo[0], num_chars, NULL, NULL);
    }
    return strTo;
}

int main()
{
    const WCHAR* wText = L"Wide string";
    const std::string text = convert_from_wstring(wText);
    std::cout << text << "\n";

    const std::wstring wtext = convert_to_wstring("Multibyte string");
    std::wcout << wtext << "\n";

    return 0;
}

如果您使用的是 C++11 或更高版本，请查看 std::wstring_convert 用于在 UTF 字符串之间进行转换的类，例如:

std::wstring convert_to_wstring(const std::string &str)
{
    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> conv;
    return conv.from_bytes(str);
}

std::string convert_from_wstring(const std::wstring &wstr)
{
    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> conv;
    return conv.to_bytes(wstr);
}

如果您需要与基于char* 的其他代码进行交互/wchar_t* , std::string作为接受 char* 的构造函数输入和一个 c_str()可用于 char* 的方法输出，同样适用于std::wstring和 wchar_t* .

关于c++ - windows中宽字符和多字节字符串之间如何相互转换？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42793735/