Introduction
I had a problem where I wanted to match a string
against a pattern based on wild characters (* and ?). The function presented in this article is a simple one that does this matching. Here are some sample patterns:
Using the Code
The usage of the function is very simple. Just call the function with two arguments. The first one is the string
to be compared with the pattern specified in the second argument. The function does not perform any error checking.
bool pattern_match(const char *str, const char *pattern) {
enum State {
Exact, Any, AnyRepeat };
const char *s = str;
const char *p = pattern;
const char *q = 0;
int state = 0;
bool match = true;
while (match && *p) {
if (*p == '*') {
state = AnyRepeat;
q = p+1;
} else if (*p == '?') state = Any;
else state = Exact;
if (*s == 0) break;
switch (state) {
case Exact:
match = *s == *p;
s++;
p++;
break;
case Any:
match = true;
s++;
p++;
break;
case AnyRepeat:
match = true;
s++;
if (*s == *q) p++;
break;
}
}
if (state == AnyRepeat) return (*s == *q);
else if (state == Any) return (*s == *p);
else return match && (*s == *p);
}
History
- 22nd July, 2007: Initial post