C++編程：ASCII,UTF-8,Unicode字符串相互轉換

#include<string>
#include<windows.h>
#include<vector>
using namespace std;

//utf8 轉 Unicode


std::wstring Utf82Unicode(const std::string& utf8string)
{
    int widesize = ::MultiByteToWideChar(CP_UTF8, 0, utf8string.c_str(), -1, NULL, 0);
    if (widesize == ERROR_NO_UNICODE_TRANSLATION)
    {
        throw std::exception("Invalid UTF-8 sequence.");
    }
    if (widesize == 0)
    {
        throw std::exception("Error in conversion.");
    }

    std::vector<wchar_t> resultstring(widesize);

    int convresult = ::MultiByteToWideChar(CP_UTF8, 0, utf8string.c_str(), -1, &resultstring[0], widesize);

    if (convresult != widesize)
    {
        throw std::exception("La falla!");
    }

    return std::wstring(&resultstring[0]);
}


//unicode 轉爲 ascii


std::string WideByte2Acsi(std::wstring& wstrcode)
{
    int asciisize = ::WideCharToMultiByte(CP_OEMCP, 0, wstrcode.c_str(), -1, NULL, 0, NULL, NULL);
    if (asciisize == ERROR_NO_UNICODE_TRANSLATION)
    {
        throw std::exception("Invalid UTF-8 sequence.");
    }
    if (asciisize == 0)
    {
        throw std::exception("Error in conversion.");
    }
    std::vector<char> resultstring(asciisize);
    int convresult =::WideCharToMultiByte(CP_OEMCP, 0, wstrcode.c_str(), -1, &resultstring[0], asciisize, NULL, NULL);

    if (convresult != asciisize)
    {
        throw std::exception("La falla!");
    }

    return std::string(&resultstring[0]);
}





//utf-8 轉 ascii


std::string UTF_82ASCII(std::string& strUtf8Code)
{
    std::string strRet("");
    //先把 utf8 轉爲 unicode
    std::wstring wstr = Utf82Unicode(strUtf8Code);
    //最後把 unicode 轉爲 ascii
    strRet = WideByte2Acsi(wstr);
    return strRet;
}


///////////////////////////////////////////////////////////////////////


//ascii 轉 Unicode


std::wstring Acsi2WideByte(std::string& strascii)
{
    int widesize = MultiByteToWideChar (CP_ACP, 0, (char*)strascii.c_str(), -1, NULL, 0);
    if (widesize == ERROR_NO_UNICODE_TRANSLATION)
    {
        throw std::exception("Invalid UTF-8 sequence.");
    }
    if (widesize == 0)
    {
        throw std::exception("Error in conversion.");
    }
    std::vector<wchar_t> resultstring(widesize);
    int convresult = MultiByteToWideChar (CP_ACP, 0, (char*)strascii.c_str(), -1, &resultstring[0], widesize);


    if (convresult != widesize)
    {
        throw std::exception("La falla!");
    }

    return std::wstring(&resultstring[0]);
}


//Unicode 轉 Utf8


std::string Unicode2Utf8(const std::wstring& widestring)
{
    int utf8size = ::WideCharToMultiByte(CP_UTF8, 0, widestring.c_str(), -1, NULL, 0, NULL, NULL);
    if (utf8size == 0)
    {
        throw std::exception("Error in conversion.");
    }

    std::vector<char> resultstring(utf8size);

    int convresult = ::WideCharToMultiByte(CP_UTF8, 0, widestring.c_str(), -1, &resultstring[0], utf8size, NULL, NULL);

    if (convresult != utf8size)
    {
        throw std::exception("La falla!");
    }

    return std::string(&resultstring[0]);
}


//ascii 轉 Utf8


std::string ASCII2UTF_8(std::string& strAsciiCode)
{
    std::string strRet("");
    //先把 ascii 轉爲 unicode
    std::wstring wstr = Acsi2WideByte(strAsciiCode);
    //最後把 unicode 轉爲 utf8
    strRet = Unicode2Utf8(wstr);
    return strRet;
}