c++ utf8 unicode ansi 互转

#include <codecvt>

std::string UnicodeToUTF8(const std::wstring & wstr)
{
std::string ret;
try {
std::wstring_convert< std::codecvt_utf8<wchar_t> > wcv;
ret = wcv.to_bytes(wstr);
} catch (const std::exception & e) {
std::cerr << e.what() << std::endl;
}
return ret;
}

std::wstring ANSIToUnicode(const std::string & str)
{

std::wstring ret;
try {
std::mbstate_t state = {};
const char *src = str.data();
size_t len = std::mbsrtowcs(nullptr, &src, 0, &state);
if (static_cast<size_t>(-1) != len) {
std::unique_ptr< wchar_t [] > buff(new wchar_t[len + 1]);
len = std::mbsrtowcs(buff.get(), &src, len, &state);
if (static_cast<size_t>(-1) != len) {
ret.assign(buff.get(), len);
}
}
}catch (const std::exception & e) {
std::cerr << e.what() << std::endl;
}
return ret;
}

std::wstring UTF8ToUnicode(const std::string & str)
{
std::wstring ret;
try {
std::wstring_convert< std::codecvt_utf8<wchar_t> > wcv;
ret = wcv.from_bytes(str);
} catch (const std::exception & e) {
std::cerr << e.what() << std::endl;
}
std::cout<<"u8tou:"<<ret.length()<<std::endl;
return ret;
}

std::string ANSIToUTF8(const std::string & str)
{
return UnicodeToUTF8(ANSIToUnicode(str));
}

std::string UnicodeToANSI(const std::wstring & wstr)
{
std::string ret;
std::mbstate_t state = {};
const wchar_t *src = wstr.data();
size_t len = std::wcsrtombs(nullptr, &src, 0, &state);
if (static_cast<size_t>(-1) != len) {
std::unique_ptr< char [] > buff(new char[len + 1]);
len = std::wcsrtombs(buff.get(), &src, len, &state);
if (static_cast<size_t>(-1) != len) {
ret.assign(buff.get(), len);
}
}
return ret;
}

std::string UTF8ToANSI(const std::string & str)
{
return UnicodeToANSI(UTF8ToUnicode(str));
}