utf8转gbk

string UTF8ToGBK(const string &utf8)
{
  int length1 = MultiByteToWideChar(CP_UTF8,MB_ERR_INVALID_CHARS,utf8.c_str(),utf8.length(),NULL,0);
  if(length1 > 0)
  {
    WCHAR *wbuf = new WCHAR[length1 * 2 + 2];
    memset(wbuf,0,length1 * 2 + 2);
    int length2 = MultiByteToWideChar(CP_UTF8,0,utf8.c_str(),utf8.length(),wbuf,length1);
    if(length2 > 0)
    {
      length1 = WideCharToMultiByte(CP_ACP,0,buf,length2,NULL,0,NULL,NULL);
      if(length1 > 0)
      {
        char *buf = new char[length1 + 1];
        memset(buf,0,length1 + 1);
        length2 = WideCharToMultiByte(CP_ACP,0,wbuf,length2,buf,length1,NULL,NULL);
        if(length2 > 0)
    {
      string gbk(buf);
      delete []wbuf;
      delete []buf;
      return gbk;
    }
    else
    {
      delete []wbuf;
      delete []buf;
      return utf8;
    }
      }
    }
    else
    {
      delete []wbuf;
      return utf8;
    }
  }
  return utf8;
} 

测试代码：

string ss = "中文状态";//这个地方一定要保存为UTF-8 with signature，不然会有new line in constant错误

string str = UTF8ToGBK(ss);

cout<<str;//中文状态