MFC URLEncode / URLDecode

inline BYTE CURLEncode::toHex(const BYTE &x) {
 return x > 9 ? x + 55: x + 48;
}

inline BYTE CURLEncode::toByte(const BYTE &x) {
 return x > 57? x - 55: x - 48;
}

CString CURLEncode::URLDecode(CString sIn)
{
    CString sOut;
    const int nLen = sIn.GetLength() + 1;
    register LPBYTE pOutTmp = NULL;
    LPBYTE pOutBuf = NULL;
    register LPBYTE pInTmp = NULL;
    LPBYTE pInBuf =(LPBYTE)sIn.GetBuffer(nLen);
    //alloc out buffer
    pOutBuf = (LPBYTE)sOut.GetBuffer(nLen);
   
    if(pOutBuf)
    {
        pInTmp   = pInBuf;
        pOutTmp = pOutBuf;
        // do encoding
        while (*pInTmp)
        {
            if('%'==*pInTmp)
            {
                pInTmp++;
                *pOutTmp++ = (toByte(*pInTmp)%16<<4) + toByte(*(pInTmp+1))%16;
                pInTmp++;
            }
            else if('+'==*pInTmp)
                *pOutTmp++ = ' ';
            else
                *pOutTmp++ = *pInTmp;
            pInTmp++;
        }
        *pOutTmp = '\0';
        sOut.ReleaseBuffer();
    }
    sIn.ReleaseBuffer();
   
    return sOut;
}

CString CURLEncode::URLEncode(CString sIn)
{
    CString sOut;
    const int nLen = sIn.GetLength() + 1;
    register LPBYTE pOutTmp = NULL;
    LPBYTE pOutBuf = NULL;
    register LPBYTE pInTmp = NULL;
    LPBYTE pInBuf =(LPBYTE)sIn.GetBuffer(nLen);
    //alloc out buffer
    pOutBuf = (LPBYTE)sOut.GetBuffer(nLen*3);
   
    if(pOutBuf)
    {
        pInTmp   = pInBuf;
        pOutTmp = pOutBuf;
        // do encoding
        while (*pInTmp)
        {
            if(isalnum(*pInTmp) || '-'==*pInTmp || '_'==*pInTmp || '.'==*pInTmp)
                *pOutTmp++ = *pInTmp;
            else if(isspace(*pInTmp))
                *pOutTmp++ = '+';
            else
            {
                *pOutTmp++ = '%';
                *pOutTmp++ = toHex(*pInTmp>>4);
                *pOutTmp++ = toHex(*pInTmp%16);
            }
            pInTmp++;
        }
        *pOutTmp = '\0';
        sOut.ReleaseBuffer();
    }
    sIn.ReleaseBuffer();
   
    return sOut;
}