Usenet 1994 January/usenetsourcesnewsgroupsinfomagicjanuary1994.iso/sources/misc/volume30/tin/part10/wildmat.c

C/C++ Source or Header | 1992-05-20 | 4.7 KB | 176 lines

/*  $Revision: 1.5 $
**
**  Do shell-style pattern matching for ?, \, [], and * characters.
**  Might not be robust in face of malformed patterns; e.g., "foo[a-"
**  could cause a segmentation violation.  It is 8bit clean.
**
**  Written by Rich $alz, mirror!rs, Wed Nov 26 19:03:17 EST 1986.
**  Rich $alz is now <[e-mail]>.
**  April, 1991:  Replaced mutually-recursive calls with in-line code
**  for the star character.
**
**  Special thanks to Lars Mathiesen <[e-mail]> for the ABORT code.
**  This can greatly speed up failing wildcard patterns.  For example:
**    pattern: -*-*-*-*-*-*-12-*-*-*-m-*-*-*
**    text 1:     -adobe-courier-bold-o-normal--12-120-75-75-m-70-iso8859-1
**    text 2:     -adobe-courier-bold-o-normal--12-120-75-75-X-70-iso8859-1
**  Text 1 matches with 51 calls, while text 2 fails with 54 calls.  Without
**  the ABORT, then it takes 22310 calls to fail.  Ugh.  The following
**  explanation is from Lars:
**  The precondition that must be fulfilled is that DoMatch will consume
**  at least one character in text.  This is true if *p is neither '*' nor
**  '\0'.)  The last return has ABORT instead of FALSE to avoid quadratic
**  behaviour in cases like pattern "*a*b*c*d" with text "abcxxxxx".  With
**  FALSE, each star-loop has to run to the end of the text; with ABORT
**  only the last one does.
**
**  Once the control of one instance of DoMatch enters the star-loop, that
**  instance will return either TRUE or ABORT, and any calling instance
**  will therefore return immediately after (without calling recursively
**  again).  In effect, only one star-loop is ever active.  It would be
**  possible to modify the code to maintain this context explicitly,
**  eliminating all recursive calls at the cost of some complication and
**  loss of clarity (and the ABORT stuff seems to be unclear enough by
**  itself).  I think it would be unwise to try to get this into a
**  released version unless you have a good test data base to try it out
**  on.
*/

#define TRUE            1
#define FALSE            0
#define ABORT            -1


    /* What character marks an inverted character class? */
#define NEGATE_CLASS        '^'
    /* Is "*" a common pattern? */
#define OPTIMIZE_JUST_STAR
    /* Do tar(1) matching rules, which ignore a trailing slash? */
#undef MATCH_TAR_PATTERN


/*
**  Match text and p, return TRUE, FALSE, or ABORT.
*/
static int
DoMatch(text, p)
    register char    *text;
    register char    *p;
{
#ifndef INDEX_DAEMON

    register int    last;
    register int    matched;
    register int    reverse;

    for ( ; *p; text++, p++) {
    if (*text == '\0' && *p != '*')
        return ABORT;
    switch (*p) {
    case '\\':
        /* Literal match with following character. */
        p++;
        /* FALLTHROUGH */
    default:
        if (*text != *p)
        return FALSE;
        continue;
    case '?':
        /* Match anything. */
        continue;
    case '*':
        while (*++p == '*')
        /* Consecutive stars act just like one. */
        continue;
        if (*p == '\0')
        /* Trailing star matches everything. */
        return TRUE;
        while (*text)
        if ((matched = DoMatch(text++, p)) != FALSE)
            return matched;
        return ABORT;
    case '[':
        reverse = p[1] == NEGATE_CLASS ? TRUE : FALSE;
        if (reverse)
        /* Inverted character class. */
        p++;
        matched = FALSE;
        if (p[1] == ']' || p[1] == '-')
        if (*++p == *text)
            matched = TRUE;
        for (last = *p; *++p && *p != ']'; last = *p)
        /* This next line requires a good C compiler. */
        if (*p == '-' && p[1] != ']'
            ? *text <= *++p && *text >= last : *text == *p)
            matched = TRUE;
        if (matched == reverse)
        return FALSE;
        continue;
    }
    }

#ifdef    MATCH_TAR_PATTERN
    if (*text == '/')
    return TRUE;
#endif    /* MATCH_TAR_ATTERN */
    return *text == '\0';

#endif    /* INDEX_DAEMON */
}


/*
**  User-level routine.  Returns TRUE or FALSE.
*/
int
wildmat(text, p)
    char    *text;
    char    *p;
{
#ifdef    OPTIMIZE_JUST_STAR
    if (p[0] == '*' && p[1] == '\0')
    return TRUE;
#endif    /* OPTIMIZE_JUST_STAR */
    return DoMatch(text, p) == TRUE;
}



#ifdef    TEST
#include <stdio.h>

/* Yes, we use gets not fgets.  Sue me. */
extern char    *gets();


main()
{
    char     p[80];
    char     text[80];

    printf("Wildmat tester.  Enter pattern, then strings to test.\n");
    printf("A blank line gets prompts for a new pattern; a blank pattern\n");
    printf("exits the program.\n");

    for ( ; ; ) {
    printf("\nEnter pattern:  ");
    (void)fflush(stdout);
    if (gets(p) == NULL || p[0] == '\0')
        break;
    for ( ; ; ) {
        printf("Enter text:  ");
        (void)fflush(stdout);
        if (gets(text) == NULL)
        exit(0);
        if (text[0] == '\0')
        /* Blank line; go back and get a new pattern. */
        break;
        printf("      %s\n", wildmat(text, p) ? "YES" : "NO");
    }
    }

    exit(0);
    /* NOTREACHED */
}
#endif    /* TEST */