lib/parser.c: add match_wildcard() function

match_wildcard function is a simple implementation of wildcard
matching algorithm. It only supports two usual wildcardes:
'*' - matches zero or more characters
'?' - matches one character
This algorithm is safe since it is non-recursive.

Signed-off-by: Du, Changbin <[e-mail]>
Cc: Jason Baron <[e-mail]>
Cc: Joe Perches <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/parser.h

···
 int match_int(substring_t *, int *result);
 int match_octal(substring_t *, int *result);
 int match_hex(substring_t *, int *result);
+bool match_wildcard(const char *pattern, const char *str);
 size_t match_strlcpy(char *, const substring_t *, size_t);
 char *match_strdup(const substring_t *);

lib/parser.c

···
 }
 
 /**
+ * match_wildcard: - parse if a string matches given wildcard pattern
+ * @pattern: wildcard pattern
+ * @str: the string to be parsed
+ *
+ * Description: Parse the string @str to check if matches wildcard
+ * pattern @pattern. The pattern may contain two type wildcardes:
+ *   '*' - matches zero or more characters
+ *   '?' - matches one character
+ * If it's matched, return true, else return false.
+ */
+bool match_wildcard(const char *pattern, const char *str)
+{
+	const char *s = str;
+	const char *p = pattern;
+	bool star = false;
+
+	while (*s) {
+		switch (*p) {
+		case '?':
+			s++;
+			p++;
+			break;
+		case '*':
+			star = true;
+			str = s;
+			if (!*++p)
+				return true;
+			pattern = p;
+			break;
+		default:
+			if (*s == *p) {
+				s++;
+				p++;
+			} else {
+				if (!star)
+					return false;
+				str++;
+				s = str;
+				p = pattern;
+			}
+			break;
+		}
+	}
+
+	if (*p == '*')
+		++p;
+	return !*p;
+}
+
+/**
  * match_strlcpy: - Copy the characters from a substring_t to a sized buffer
  * @dest: where to copy to
  * @src: &substring_t to copy
···
 EXPORT_SYMBOL(match_int);
 EXPORT_SYMBOL(match_octal);
 EXPORT_SYMBOL(match_hex);
+EXPORT_SYMBOL(match_wildcard);
 EXPORT_SYMBOL(match_strlcpy);
 EXPORT_SYMBOL(match_strdup);