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#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <assert.h>
#include <stdio.h>
#include "regex.h"
range_t*_regexp_match(
char *whole_regex, char *regex, char *line,
bool caret, bool dollar,
size_t index, size_t start, size_t len) {
if ((regex[0] == '\0' && line[0] == '\0') || (regex[0] == '\0' && !dollar)) {
range_t *result = malloc(sizeof(range_t));
*result = (range_t){.start=start, .end=len + start};
return result;
}
if (regex[0] == '\0' || line[0] == '\0') {
return NULL;
}
if (regex[1] == '*') {
if (regex[0] == line[0]) {
range_t *end = _regexp_match(whole_regex, regex + 2, line + 1, dollar, index + 1, start, len + 1);
if (end) {
return end;
}
return _regexp_match(whole_regex, regex, line + 1, dollar, index + 1, start, len + 1);
}
if (!caret) {
range_t *restart = _regexp_match(whole_regex, whole_regex, line + 1, dollar, index + 1, index + 1, 0);
if (restart) {
return restart;
}
}
return _regexp_match(whole_regex, regex + 2, line, dollar, index, start, len);
}
if (regex[0] == line[0]) {
range_t *has_match = _regexp_match(whole_regex, regex + 1, line + 1, dollar, index + 1, start, len + 1);
if (has_match) {
return has_match;
}
}
if (!caret) {
return _regexp_match(whole_regex, whole_regex, line + 1, dollar, index + 1, index + 1, 0);
}
return NULL;
}
range_t *regexp_match(char *regex, char *line) {
bool caret = false;
if (regex[0] == '^') {
caret = true;
regex += 1;
}
bool dollar = false;
if (regex[strlen(regex) - 1] == '$') {
dollar = true;
regex[strlen(regex) - 1] = '\0';
}
assert(line[0] != '*');
range_t *result;
for (size_t i = 0; i < strlen(line); i++) {
if ((result = _regexp_match(regex, regex, line + i, dollar, i, i, 0))) {
return result;
}
}
return NULL;
}