C++ 与String与WString相互转换

#include <wchar.h>
#include <windows.h>
 
/** @fn        std::wstring String2WString(const std::string& str_in)
*  @brief    string转换为wstring
*  @param    (IN) const std::string&
*  @return    std::wstring
*/
std::wstring String2WString(const std::string& str_in)
{
    if (str_in.empty())
    {
        std::cout << "str_in is empty" << std::endl;
        return L"";
    }
 
    // 获取待转换的数据的长度
    int len_in = MultiByteToWideChar(CP_UTF8, 0, (LPCSTR)str_in.c_str(), -1, NULL, 0);
    if (len_in <= 0)
    {
        std::cout << "The result of WideCharToMultiByte is Invalid!" << std::endl;
        return L"";
    }
 
    // 为输出数据申请空间
    std::wstring wstr_out;
    wstr_out.resize(len_in - 1, L'\0');
 
    // 数据格式转换
    int to_result = MultiByteToWideChar(CP_UTF8, 0, (LPCSTR)str_in.c_str(), -1, (LPWSTR)wstr_out.c_str(), len_in);
 
    // 判断转换结果
    if (0 == to_result)
    {
        std::cout << "Can't transfer String to WString" << std::endl;
    }
 
    return wstr_out;
}
 
/** @fn        std::string WString2String(const std::wstring& str_in)
*  @brief    wstring转换为string
*  @param    (IN) const std::wstring&
*  @return    std::string
*/
std::string WString2String(const std::wstring& str_in)
{
    if (str_in.empty())
    {
        std::cout << "str_in is empty" << std::endl;
        return "";
    }
 
    // 获取待转换的数据的长度
    int len_in = WideCharToMultiByte(CP_UTF8, 0, (LPCWSTR)str_in.c_str(), -1, NULL, 0, NULL, NULL);
    if (len_in <= 0)
    {
        std::cout << "The result of WideCharToMultiByte is Invalid!" << std::endl;
        return "";
    }
 
    // 为输出数据申请空间
    std::string wstr_out;
    wstr_out.resize(len_in - 1, '\0');
 
    // 数据格式转换
    int to_result = WideCharToMultiByte(CP_UTF8, 0, (LPCWSTR)str_in.c_str(), -1, (LPSTR)wstr_out.c_str(), len_in, NULL, NULL);
 
    // 判断转换结果
    if (0 == to_result)
    {
        std::cout << "Can't transfer WString to String" << std::endl;
        return "";
    }
 
    return wstr_out;
}