filename pattern matching

This is a discussion on filename pattern matching within the C Programming forums, part of the General Programming Boards category; Here's a function that matches a filter (like *.c) to a filename (like hippo.c). Code: int match(char *f, char *s) ...

  1. #1
    Frequently Quite Prolix dwks's Avatar
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    Lightbulb filename pattern matching

    Here's a function that matches a filter (like *.c) to a filename (like hippo.c).

    Code:
    int match(char *f, char *s) {
        char *t;
    
        while(1) {
            if(*f == '?' || *s == '?') ;
            else if(*f == '*') {
                t = s;
                while(1) {
                    if(match(f+1, t)) return 1;
                    if(!*t++) break;
                }
    
                return 0;
            }
            else if(*s == '*') {
                t = f;
                while(1) {
                    if(match(s+1, t)) return 1;
                    if(!*t++) break;
                }
    
                return 0;
            }
            else if(*f != *s) return 0;
    
            if(!*s || !*f) break;
            s++, f++;
        }
    
        return *f || *s ? 0 : 1;
    }
    It returns 1 if there's a match, 0 otherwise.

    There's nothing wrong with it (as far as I can see), I was just wondering how it could be improved. It's a little too slow for me.

    Before anyone points it out, the * matching could be removed from one of the arguments.
    Last edited by dwks; 07-12-2005 at 05:47 PM.
    dwk

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  2. #2
    ATH0 quzah's Avatar
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    Here's a quick lazy way:
    Code:
    int match( char *f, char *s )
    {
        char *fend, *send;
        fend = f + strlen( f ) - 1;
        send = s + strlen( s ) - 1;
    
        while( *fend == *send && fend > f && send > s )
        {
            fend--;
            send--;
        }
    
        if( *fend == '*' )
            return 1;
        return 0;
    }
    Something like that? Or do you want stuff like this to work too?
    Code:
    int restult = match ( "hip*.c", "hippo.c" ); /* returns 1 */

    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
    Frequently Quite Prolix dwks's Avatar
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    I want everything to work - like hi??o.exe matches hippo.*
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
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  4. #4
    ATH0 quzah's Avatar
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    So what are all of your matching rules? You'll need to actually list what you consider a match first. Define the rules for matching and wild cards.


    Quzah.
    Hope is the first step on the road to disappointment.

  5. #5
    Frequently Quite Prolix dwks's Avatar
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    All DOS pattern matching . . . Like ? matches any one character, and * matches zero or more characters.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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  6. #6
    Yes, my avatar is stolen anonytmouse's Avatar
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    Code:
    #include <windows.h>
    #include <shlwapi.h>
    
    int match(char *f, char *s)
    {
        return PathMatchSpec(f, s);
    }

  7. #7
    Frequently Quite Prolix dwks's Avatar
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    That's sort of what I'm trying to duplicate . . . but I don't have <windows.h>.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


    Other boards: DaniWeb, TPS
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  8. #8
    Registered User major_small's Avatar
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    you may want to check the boost libraries... I think they have libraries for what's called regular expressions (or REGEX for short)

    note: their site seems to be not working ATM...

    edit: it works, but it's slow as anything... (>2 minute load time)
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  9. #9
    ATH0 quzah's Avatar
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    Aren't the Boost libraries for C++? At any rate, yours fails a few tests it should pass. At least from what I can gather by your rules. Maybe not? Any way, mine's a bit different. Perhaps not better. Either way, they don't always give the same results, so one of us is wrong. :P
    Code:
    #include<stdio.h>
    #include<string.h>
    
    int match(char *f, char *s) {
        char *t;
    
        while(1) {
            if(*f == '?' || *s == '?') ;
            else if(*f == '*') {
                t = s;
                while(1) {
                    if(match(f+1, t)) return 1;
                    if(!*t++) break;
                }
    
                return 0;
            }
            else if(*s == '*') {
                t = f;
                while(1) {
                    if(match(s+1, t)) return 1;
                    if(!*t++) break;
                }
    
                return 0;
            }
            else if(*f != *s) return 0;
    
            if(!*s || !*f) break;
            s++, f++;
        }
    
        return *f || *s ? 0 : 1;
    }
    
    int qmatch( char *f, char *s )
    {
        while( *f && *s )
        {
            if( *f == '*' )
            {
                while( *f && (*f == '*' || *f == '?') ) f++;
                while( *s && *s != *f )*s++;
            }
            if( !*s || !*f ) break;
            if( *s == '*' )
            {
                while( *s && (*s == '*' || *s == '?') ) s++;
                while( *f && *f != *s )*f++;
            }
            if( !*s || !*f ) break;
            if( *f == *s || *f == '?' || *s == '?' )
            {
                f++;
                s++;
            }
            else
                return 0;
        }
        return (*f || *s) || (*f==*s) ? 1 : 0;
    
    }
    
    int main( void )
    {
        char *s[] =
        {
            "foo.c",
            "?oo.c",
            "*.c",
            "f?*",
            "?*?",
            "*",
            "?.*",
            "foo.*"
        };
    
        char *f[] =
        {
            "foo.c",
            "?oo.c",
            "*.c",
            "?*.c",
            "*?.?",
            "foo.?",
            "foo.*",
            "f?o?c",
            "f*o*"
            "*",
            "?????"
        };
    
        int x,y;
    
        for( y = 0; y < sizeof f / sizeof f[0]; y++ )
        {
            for( x = 0; x < sizeof s / sizeof s[0]; x++ )
            {
                printf("%8s vs %8s = %d, %d\n", f[ y ], s[ x ],
                    match( f[ y ], s[ x ] ),
                    qmatch( f[ y ], s[ x ] )
                );
            }
    
        }
    
        return 0;
    }
    /*
       foo.c vs    foo.c = 1, 1
       foo.c vs    ?oo.c = 1, 1
       foo.c vs      *.c = 1, 1
       foo.c vs      f?* = 1, 1
       foo.c vs      ?*? = 1, 1
       foo.c vs        * = 1, 1
       foo.c vs      ?.* = 0, 0
       foo.c vs    foo.* = 1, 1
       ?oo.c vs    foo.c = 1, 1
       ?oo.c vs    ?oo.c = 1, 1
       ?oo.c vs      *.c = 0, 1
       ?oo.c vs      f?* = 1, 1
       ?oo.c vs      ?*? = 1, 1
       ?oo.c vs        * = 0, 1
       ?oo.c vs      ?.* = 0, 0
       ?oo.c vs    foo.* = 1, 1
         *.c vs    foo.c = 1, 1
         *.c vs    ?oo.c = 0, 1
         *.c vs      *.c = 1, 1
         *.c vs      f?* = 1, 1
         *.c vs      ?*? = 1, 1
         *.c vs        * = 1, 1
         *.c vs      ?.* = 1, 1
         *.c vs    foo.* = 1, 1
        ?*.c vs    foo.c = 1, 1
        ?*.c vs    ?oo.c = 1, 1
        ?*.c vs      *.c = 1, 1
        ?*.c vs      f?* = 1, 1
        ?*.c vs      ?*? = 1, 1
        ?*.c vs        * = 0, 1
        ?*.c vs      ?.* = 1, 1
        ?*.c vs    foo.* = 1, 1
        *?.? vs    foo.c = 1, 1
        *?.? vs    ?oo.c = 0, 1
        *?.? vs      *.c = 1, 1
        *?.? vs      f?* = 1, 1
        *?.? vs      ?*? = 0, 1
        *?.? vs        * = 0, 1
        *?.? vs      ?.* = 1, 1
        *?.? vs    foo.* = 1, 1
       foo.? vs    foo.c = 1, 1
       foo.? vs    ?oo.c = 1, 1
       foo.? vs      *.c = 1, 1
       foo.? vs      f?* = 1, 1
       foo.? vs      ?*? = 1, 1
       foo.? vs        * = 1, 1
       foo.? vs      ?.* = 0, 0
       foo.? vs    foo.* = 1, 1
       foo.* vs    foo.c = 1, 1
       foo.* vs    ?oo.c = 1, 1
       foo.* vs      *.c = 1, 1
       foo.* vs      f?* = 1, 1
       foo.* vs      ?*? = 1, 1
       foo.* vs        * = 1, 1
       foo.* vs      ?.* = 0, 0
       foo.* vs    foo.* = 1, 1
       f?o?c vs    foo.c = 1, 1
       f?o?c vs    ?oo.c = 1, 1
       f?o?c vs      *.c = 1, 1
       f?o?c vs      f?* = 1, 1
       f?o?c vs      ?*? = 0, 1
       f?o?c vs        * = 1, 1
       f?o?c vs      ?.* = 1, 1
       f?o?c vs    foo.* = 1, 1
       f*o** vs    foo.c = 1, 1
       f*o** vs    ?oo.c = 1, 1
       f*o** vs      *.c = 1, 1
       f*o** vs      f?* = 1, 1
       f*o** vs      ?*? = 1, 1
       f*o** vs        * = 1, 1
       f*o** vs      ?.* = 1, 1
       f*o** vs    foo.* = 1, 1
       ????? vs    foo.c = 1, 1
       ????? vs    ?oo.c = 1, 1
       ????? vs      *.c = 0, 1
       ????? vs      f?* = 0, 1
       ????? vs      ?*? = 0, 1
       ????? vs        * = 0, 1
       ????? vs      ?.* = 0, 1
       ????? vs    foo.* = 1, 1
    */
    Mine was an attempt to really cover all the cases I could think up for valid matching. I don't know if they fit all of your rules, but that's my take on it.

    Quzah.
    Hope is the first step on the road to disappointment.

  10. #10
    aoeuhtns
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    Let's stop this madness; only one string should be parsed for wildcards; the filename should not.

  11. #11
    ATH0 quzah's Avatar
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    That wasn't a requirement given. Thus, I matched his code, except mine works. As I recall, you weren't the one setting the rules for this little event.


    Quzah.
    Hope is the first step on the road to disappointment.

  12. #12
    Frequently Quite Prolix dwks's Avatar
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    Quzah, you're right: mine was wrong. The if(*s=='?' || *f=='?') was in the wrong place.

    Code:
    int match(char *f, char *s) {
        char *t;
    
        while(1) {
            if(*f == '*') {
                t = s;
                while(1) {
                    if(match(f+1, t)) return 1;
                    if(!*t++) break;
                }
    
                return 0;
            }
            else if(*s == '*') {
                t = f;
                while(1) {
                    if(match(s+1, t)) return 1;
                    if(!*t++) break;
                }
    
                return 0;
            }
            else if(*f == '?' || *s == '?') ;
            else if(*f != *s) return 0;
    
            if(!*s || !*f) break;
            s++, f++;
        }
    
        return *f || *s ? 0 : 1;
    }
    If there was a ?, it ignored the other character - even if it was a *. This should work - run it through your test again.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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    My website: http://dwks.theprogrammingsite.com/
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