Doubt in reading numeric values from INI file

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Hi,

In my application, I want read the two integer values from ini file.That value should be in the range -1 to 1023. I have used GetPrivateProfileString() to read the values and converted the string to integer using _wtoi().
But if I enter some invalid values like string values or empty values, the _wtoi returns the value as zero. That is a valid number in my case, but it should not happen.

So please tell me whether I can specify any range while reading the value from ini file or any other alternative for _wtoi().

Thanks in advance...

Posted 18-Aug-11 21:13pm

sanoopdas

Updated 19-Aug-11 19:44pm

v2

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6 solutions

Solution 1

You can't specify any limits on GetPrivbateProfileString - it returns what it finds, and can only be given a default value (which could be a number outside your valid range). But it only applied the default if it does not find the key defined in the INI file.

There is no equivalent of _wtoi that does what you ask - it returns 0 if the function fails.

I would suggest that you pre-process the returned string, and check it for validity yourself.

Posted 18-Aug-11 21:31pm

OriginalGriff

Solution 2

You may use instead the GetPrivateProfileInt[^] function, providing a default value 'out of the allowed range' (e.g. 16384) and then check the return value.

Posted 18-Aug-11 21:33pm

CPallini

Comments

sanoopdas 19-Aug-11 3:38am

We can't use GetPrivateProfileInt(), since it does not support negative values.

UINT WINAPI GetPrivateProfileInt()

CPallini 19-Aug-11 3:44am

Despite its signature, that function works with (signed) integers (just made a test).
An alternative route would be using GetPrivateProfileString and then strtol to perform the conversion (the latter function gives you the means to check if the conversion was good).

Philippe Mori 19-Aug-11 16:38pm

strtol won't help to detect all errors.

CPallini 21-Aug-11 3:58am

Yes, it would help.

Philippe Mori 21-Aug-11 7:36am

It helps for out of range values but not for invalid text which will still returns 0.... which seems to be the main concern of the OP.

CPallini 22-Aug-11 3:36am

It sets the pointer to the first character that stopped the parsing. That is a useful info in order to establish the correctness of the input string.

Solution 3

There are no standard library functions to do what you want, so you should write your own conversion routine which checks for illegal characters and values.

[edit]Alternatively you could use wcsspn()[^] to check for valid characters and then use _wtoi() to convert if valid.[/edit]

Posted 18-Aug-11 22:31pm

Richard MacCutchan

Updated 18-Aug-11 22:33pm

v2

Solution 4

If the returns value is 0 then check if the string contains a 0.

It is a bit simpler to do it that way as the extra check is simpler to code.

Posted 19-Aug-11 10:34am

Philippe Mori

Updated 19-Aug-11 10:35am

v2

Comments

sanoopdas 20-Aug-11 2:02am

That is a nice solution.
But if the user has given like this "00" or "000", then also that is a zero. So the checking will be little difficult.

Philippe Mori 20-Aug-11 8:27am

Well, often if user should not modify those strings, then a bit of "undefined" behavior could be acceptable. Thus it might not be that bad if such string are handled either as 0 or as other invalid strings.

Similary, does the application has to handle binary, hexadecimal or octal numbers? Do it have to handle number in scientific notation (1e3 for 1000)? Does it have to handle very large numbers? Does it have to handle the case where there is some text after the number?

If you want it to be fully defined and implement it according to the specification, then it is fine but most of the time simpler code is more than enough (particulary when normally the settings are written only by the application itself).

Solution 6

You can use GetPrivateProfileInt() for this requirement.

UINT WINAPI GetPrivateProfileInt()

Since the size of UINT and INT are same, there will not any data lose.
The only difference is that, UINT take the sign bit as value.
but when you type cast the same UINT to a INT, the sign bit is valid again.

C++

UINT uRet = GetPrivateProfileInt( csAppName, csKeyName, nDefaultVal, lpctszFile );
// Now the nRet is invalid due to the sign error
// convert the UINT to INT
INT nValue = static_cast<int>( uRet );
</int>

Posted 10-Sep-14 2:36am

Nyil

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sanoopdas · Accepted Answer · 2011-08-19T20:10:00

Finally I have decided to write my own function which will read the integer value from INI and does the validation according to the input as shown below.

C++

long ReadIntegerValueFromIni( const CString& csAppName_i,
                              const CString& csKeyName_i,
                              const CString& csDefaultVal_i,
                              const CString& csFileName_i,
                              const int nMinVal_i,
                              const int nMaxVal_i )
{
    long lKeyValue = 0;
    int nDefaultVal = _ttoi( csDefaultVal_i );
    try
    {
        const int SUCCESS_RET = 1;
        TCHAR tcszBuf[ MAX_PATH ];
        TCHAR tcszBufTemp[ MAX_PATH ];
        lKeyValue = nDefaultVal;

        // Read the value from INI file.
        GetPrivateProfileString( csAppName_i, csKeyName_i, csDefaultVal_i, tcszBuf, sizeof( tcszBuf ),
                                 csFileName_i );
        // Check whether the value read from ini is a valid numeric number or not.
        if( SUCCESS_RET != swscanf( tcszBuf, _T( "%d%s" ), &lKeyValue, &tcszBufTemp ))
        {
            lKeyValue = nDefaultVal;
            // Invalid value found so adjusted to Default Value.
        }
        // Check whether the value read from ini is within the allowed range or not.
        else if( nMinVal_i > lKeyValue || nMaxVal_i < lKeyValue )
        {
            lKeyValue = nDefaultVal;
            // Input value is not within the allowed range, so adjusted to Default Value
        }
        else
        {
            // Do nothing.
        }
    }
    catch( ... )
    {
        // Unhandled exception occured in ReadIntegerValueFromIni()
        lKeyValue = nDefaultVal;
    }
    return lKeyValue;
}

Valid comments are welcome.