Quelle glob.c Sprache: C

#include <linux/module.h>
#include <linux/glob.h>

/*
* The only reason this code can be compiled as a module is because the
* ATA code that depends on it can be as well.  In practice, they're
* both usually compiled in and the module overhead goes away.
*/
MODULE_DESCRIPTION("glob(7) matching");
MODULE_LICENSE("Dual MIT/GPL");

/**
* glob_match - Shell-style pattern matching, like !fnmatch(pat, str, 0)
* @pat: Shell-style pattern to match, e.g. "*.[ch]".
* @str: String to match.  The pattern must match the entire string.
*
* Perform shell-style glob matching, returning true (1) if the match
* succeeds, or false (0) if it fails.  Equivalent to !fnmatch(@pat, @str, 0).
*
* Pattern metacharacters are ?, *, [ and \.
* (And, inside character classes, !, - and ].)
*
* This is small and simple implementation intended for device blacklists
* where a string is matched against a number of patterns.  Thus, it
* does not preprocess the patterns.  It is non-recursive, and run-time
* is at most quadratic: strlen(@str)*strlen(@pat).
*
* An example of the worst case is glob_match("*aaaaa", "aaaaaaaaaa");
* it takes 6 passes over the pattern before matching the string.
*
* Like !fnmatch(@pat, @str, 0) and unlike the shell, this does NOT
* treat / or leading . specially; it isn't actually used for pathnames.
*
* Note that according to glob(7) (and unlike bash), character classes
* are complemented by a leading !; this does not support the regex-style
* [^a-z] syntax.
*
* An opening bracket without a matching close is matched literally.
*/
bool __pure glob_match(char const *pat, char const *str)
{
/*
* Backtrack to previous * on mismatch and retry starting one
* character later in the string.  Because * matches all characters
* (no exception for /), it can be easily proved that there's
* never a need to backtrack multiple levels.
*/
char const *back_pat = NULL, *back_str;

/*
* Loop over each token (character or class) in pat, matching
* it against the remaining unmatched tail of str.  Return false
* on mismatch, or true after matching the trailing nul bytes.
*/
for (;;) {
  unsigned char c = *str++;
  unsigned char d = *pat++;

  switch (d) {
  case '?': /* Wildcard: anything but nul */
   if (c == '\0')
    return false;
   break;
  case '*': /* Any-length wildcard */
   if (*pat == '\0') /* Optimize trailing * case */
    return true;
   back_pat = pat;
   back_str = --str; /* Allow zero-length match */
   break;
  case '[': { /* Character class */
   if (c == '\0') /* No possible match */
    return false;
   bool match = false, inverted = (*pat == '!');
   char const *class = pat + inverted;
   unsigned char a = *class++;

   /*
* Iterate over each span in the character class.
* A span is either a single character a, or a
* range a-b.  The first span may begin with ']'.
*/
   do {
    unsigned char b = a;

    if (a == '\0') /* Malformed */
     goto literal;

    if (class[0] == '-' && class[1] != ']') {
     b = class[1];

     if (b == '\0')
      goto literal;

     class += 2;
     /* Any special action if a > b? */
    }
    match |= (a <= c && c <= b);
   } while ((a = *class++) != ']');

   if (match == inverted)
    goto backtrack;
   pat = class;
   }
   break;
  case '\\':
   d = *pat++;
   fallthrough;
  default: /* Literal character */
literal:
   if (c == d) {
    if (d == '\0')
     return true;
    break;
   }
backtrack:
   if (c == '\0' || !back_pat)
    return false; /* No point continuing */
   /* Try again from last *, one character later in str. */
   pat = back_pat;
   str = ++back_str;
   break;
  }
}
}
EXPORT_SYMBOL(glob_match);

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