引用元

Convert lptstr to char*
https://stackoverflow.com/questions/342772/convert-lptstr-to-char

引用元のコード

CP_ACPはSJIS

WinNIs.h

#define CP_ACP                    0           // default to ANSI code page
#define CP_UTF8                   65001       // UTF-8 translation

Sample.cpp

#include <windows.h>

/* string consisting of several Asian characters */
LPTSTR wcsString = L"\u9580\u961c\u9640\u963f\u963b\u9644";
//LPTSTR wcsString = L"OnlyAsciiCharacters";

char* encode(const wchar_t* wstr, unsigned int codePage)
{
    int sizeNeeded = WideCharToMultiByte(codePage, 0, wstr, -1, NULL, 0, NULL, NULL);
    char* encodedStr = new char[sizeNeeded];
    WideCharToMultiByte(codePage, 0, wstr, -1, encodedStr, sizeNeeded, NULL, NULL);
    return encodedStr;
}

wchar_t* decode(const char* encodedStr, unsigned int codePage)
{
   int sizeNeeded = MultiByteToWideChar(codePage, 0, encodedStr, -1, NULL, 0);
   wchar_t* decodedStr = new wchar_t[sizeNeeded ];
   MultiByteToWideChar(codePage, 0, encodedStr, -1, decodedStr, sizeNeeded );
   return decodedStr;
}

int main(int argc, char* argv[])
{
   char* str = encode(wcsString, CP_UTF8); //UTF-8 encoding
   wchar_t* wstr = decode(str, CP_UTF8);
   //If the wcsString is UTF-8 encodable, then this comparison will result to true.
   //(As i remember some of the Chinese dialects cannot be UTF-8 encoded 
   bool ok = memcmp(wstr, wcsString, sizeof(wchar_t) * wcslen(wcsString)) == 0; 
   delete str;
   delete wstr;

   str = encode(wcsString, 20127); //US-ASCII (7-bit) encoding
   wstr = decode(str, 20127);
   //If there were non-ascii characters existing on wcsString, 
   //we cannot return back, since some of the data is lost
   ok = memcmp(wstr, wcsString, sizeof(wchar_t) * wcslen(wcsString)) == 0; 
   delete str;
   delete wstr;
}