string与utf8字符串转换

1.  utf8转std::string

转换过程：先将utf8转双字节Unicode编码，再通过WideCharToMultiByte将宽字符转换为多字节。
//-----------------------------------------------------------------------
std::string UTF8_To_string(const std::string & str)
{
int nwLen = MultiByteToWideChar(CP_UTF8, 0, str.c_str(), -1, NULL, 0);

wchar_t * pwBuf = new wchar_t[nwLen + 1];//此处要加1

memset(pwBuf, 0, nwLen * 2 + 2);

MultiByteToWideChar(CP_UTF8, 0, str.c_str(), str.length(), pwBuf, nwLen);

int nLen = WideCharToMultiByte(CP_ACP, 0, pwBuf, -1, NULL, NULL, NULL, NULL);

char * pBuf = new char[nLen + 1];
memset(pBuf, 0, nLen + 1);

WideCharToMultiByte(CP_ACP, 0, pwBuf, nwLen, pBuf, nLen, NULL, NULL);

std::string retStr = pBuf;

delete []pBuf;
delete []pwBuf;

pBuf = NULL;
pwBuf = NULL;

return retStr;
}

2.std::string转utf8字符串

转换过程：与1过程相反
//------------------------------------------------------------------------
std::string string_To_UTF8(const std::string & str)
{
int nwLen = ::MultiByteToWideChar(CP_ACP, 0, str.c_str(), -1, NULL, 0);

wchar_t * pwBuf = new wchar_t[nwLen + 1];//此处要加1

ZeroMemory(pwBuf, nwLen * 2 + 2);

::MultiByteToWideChar(CP_ACP, 0, str.c_str(), str.length(), pwBuf, nwLen);

int nLen = ::WideCharToMultiByte(CP_UTF8, 0, pwBuf, -1, NULL, NULL, NULL, NULL);

char * pBuf = new char[nLen + 1];
ZeroMemory(pBuf, nLen + 1);

::WideCharToMultiByte(CP_UTF8, 0, pwBuf, nwLen, pBuf, nLen, NULL, NULL);

std::string retStr(pBuf);

delete []pwBuf;
delete []pBuf;

pwBuf = NULL;
pBuf  = NULL;

return retStr;
}

转载自：http://blog.csdn.net/kieven2008/article/details/5797932