utf8_to_sjis.cpp

#include <Windows.h>
#include <vector>
#include <string>

BOOL utf8_to_sjis(BYTE* pSource, BYTE* pDist, int* pSize)
{
    *pSize = 0;

    //UTF-8 -> UTF-16
    const int nSize = ::MultiByteToWideChar(CP_UTF8, 0, (LPCSTR) pSource, -1, NULL, 0);

    BYTE* buffUtf16 = new BYTE[nSize * 2 + 2];
    ::MultiByteToWideChar(CP_UTF8, 0, (LPCSTR) pSource, -1, (LPWSTR) buffUtf16, nSize);

    //UTF-16 -> Shift-JIS
    const int nSizeSJis = ::WideCharToMultiByte(CP_ACP, 0, (LPCWSTR) buffUtf16, -1, NULL, 0, NULL, NULL);
    if (!pDist) {
        *pSize = nSizeSJis;
        delete buffUtf16;
        return TRUE;
    }

    BYTE* buffSJis = new BYTE[nSizeSJis * 2];
    ZeroMemory(buffSJis, nSizeSJis * 2);
    ::WideCharToMultiByte(CP_ACP, 0, (LPCWSTR) buffUtf16, -1, (LPSTR) buffSJis, nSizeSJis, NULL, NULL);

    *pSize = lstrlen((char*) buffSJis);
    memcpy(pDist, buffSJis, *pSize);

    delete buffUtf16;
    delete buffSJis;

    return TRUE;
}

std::string utf8_to_sjis(std::string const& utf8)
{
    int n;
    std::vector<unsigned char> sjis(utf8.size(), '\0');
    utf8_to_sjis((BYTE*) utf8.data(), sjis.data(), &n);
    return {sjis.begin(), sjis.end()};
}