[C/C++] 轉換編碼的function (iconv)

在C/C++裡面使用iconv function包含下列三步驟：
1. 用iconv_open建立一個iconv_t的變數
2. 呼叫iconv執行轉換
3. 用iconv_close來結束iconv_t的變數

下面這一段code是把iconv包成一個function方便使用：

string    pwtIconv(string buf, string fromCode, string toCode)
{
   iconv_t        cd;
   char        tmp[1000];
   string        outBuf;
   size_t        inBytesLeft, outBytesLeft;
   const char    *inTmp;
   char        *outTmp;


   cd = iconv_open(toCode.c_str(), fromCode.c_str());
   if(cd == ((iconv_t) - 1))
   {
       if(errno == EINVAL)
           cout << "no conversion from " << toCode << " to " << fromCode << endl;
       else
           cout << "conversion setup error" << endl;
       fflush(stdout);
       return "";
   }

   //type conversion
   inTmp = buf.c_str();
   outTmp = tmp;
   //set initial length of in and out string
   inBytesLeft = buf.length() + 1;
   outBytesLeft = 1000;

   while(inBytesLeft > 0)
   {
       size_t iconv_value;

       iconv_value = iconv(cd, &inTmp, &inBytesLeft, &outTmp, &outBytesLeft);
       if(iconv_value  == (size_t) - 1)
       {
           cout << "some error" << endl;
           fflush(stdout);
           break;
       }
   }

   outBuf = tmp;
   iconv_close(cd);

   return outBuf;
}

有些錯誤檢查沒有很嚴謹，但是資料正常應該是能運作。

參考資料 :
http://www.gnu.org/software/libtool/manual/libc/iconv-Examples.html#iconv-Examples