Best way to find a whitespace-delimited word in a CString

Question

example: "select * from somewhere where x = 1"

I want to find the whitespace-delimited "where", but not the "where" within "somewhere". In the example "where" is delimited by spaces, but it could be carriage returns, tabs etc.

Note: I know regex would make it easy to do (the regex equivalent would be "\bwhere\b"), but I don't want to add a regex library to my project just to do this.

score 7 · Accepted Answer · answered Jul 24 '09 at 13:23

7

If you wanted to use the pure MFC method of string manipulation, then this should work:

CString strSql = _T("select * from somewhere where x = 1");

int nTokenPos = 0;
CString strToken = strSql.Tokenize(_T(" \r\n\t"), nTokenPos);

while (!strToken.IsEmpty())
{
    if (strToken.Trim().CompareNoCase(_T("where")) == 0)
        return TRUE; // found
    strToken = strSql.Tokenize(_T(" \r\n\t"), nTokenPos);
}

return FALSE; // not found

answered Jul 24 '09 at 13:23

Alan

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I like this answer. It uses pure MFC, which I prefer, and also enables to do case insensitive searches. sbi's and JIa3ep's answers are also pretty good, though. – djeidot Jul 24 '09 at 13:52

score 3 · Answer 2 · answered Jul 24 '09 at 12:26

3

I don't know the first thing about MFC and CString, but in plain C++ I'd stuff that string into an std::istringstream and read from that into a string:

std::istringstream iss("select * from somewhere where x = 1");
std::string word;
do {
  iss >> word;
  if( !iss ) throw "blah blah!";
} while( word != "where" );

I suppose CString does have stream operators overloaded with the appropriate semantics, but, as I said, I don't know it.

answered Jul 24 '09 at 12:26

sbi

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The extraction requires an ostream, and will read from any ostreambuf. You'd need an ostreambuf over CString to do this. – MSalters Jul 24 '09 at 13:37
@MSalters: Ah, `istream` -- _that_ I understand. Anyway, I wouldn't know whether there's any stream buffers for `CString`. I never used MFC. – sbi Jul 24 '09 at 16:17

Kirill V. Lyadvinsky · Answer 3 · 2009-07-24T13:03:39.040

2

Pretty fast and doesn't need to construct heavy istringstream objects.

CString str = L"select * from somewhere where x = 1";
CString to_find = L"where";
int i =0;
while ( i < str.GetLength() ) {
    i = str.Find(to_find, i);
    if ( i == -1 ) break;
    if ( (i == 0 || !isalpha(str[i-1])) && (i == str.GetLength()-to_find.GetLength() || !isalpha(str[i+to_find.GetLength()])) ) break;
    i+=to_find.GetLength();
}
if ( i >= 0 && i < str.GetLength() ) // found
else // not found

edited Jul 24 '09 at 13:03

answered Jul 24 '09 at 12:30

Kirill V. Lyadvinsky

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this one actually enables to search for more complex expressions like "GROUP BY" – djeidot Jul 29 '09 at 10:25
Yes, my solution is universal and doesn't require additional memory. – Kirill V. Lyadvinsky Jul 29 '09 at 10:49

score 0 · Answer 4 · answered Jul 24 '09 at 12:24

0

If you are using Visual Studio 2008 with Feature Pack you already have std::tr1::regex in C++.

answered Jul 24 '09 at 12:24

Cristian Adam

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score -1 · Answer 5 · answered Jul 24 '09 at 12:23

Well, regex is the correct answer. If you don't want to include regex, you will have to try and implement a bit of regex yourself and search for " where ".

Your only other option I guess would be to search for "where", then check the character before and after the match to see if they are whitespace characters.

Best way to find a whitespace-delimited word in a CString

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