regex

a pure C implementation of simple regular express engine, using DFA engine. the former is just for yes-or-no matching.

that's all begin from 正则表达式实现

Just for fun. ;)

pattern

pattern	describe
$	matches the end of the string
ab	matches a followed by b
	matches a or b (ordered)
a*	matches at least 0 repetitions of a
a?	matches 0 or 1 repetitions of a
a+	matches 1 or more repetitions of a
(...)	matches whatever regex is inside the parentheses, as a single element
[a-b]	matches any characters between a and b (range)
.	matches any characters, equivalent to the set [0-0xff]
\d	matches any decimal digit, equivalent to the set [0-9]
\	escapes special characters

the following escaping sequences are supported:

escapes	describe
\t	tab
\n	newline
\r	return
\s	space
\\	\
\(	(
\)	)
\[	[
\]	]
\-	-
\.	.
\+	+
\$	$

^ (matches the start of the string) is enabled by default.

todo list

1. subset DFA
2. backreference
3. capture

api

// create/free a regex environment.
struct reg_env* reg_open_env();
void reg_close_env(struct reg_env* env);

// create/free a regex pattern.
struct reg_pattern* reg_new_pattern(struct reg_env* env, const char* rule);
void reg_free_pattern(struct reg_pattern* pattern);

// match pattern, return a boolean value.
int reg_match(struct reg_pattern* pattern, const char* source, int len);

see src/regex.h headfile for detail.

example

  // create env
  struct reg_env* env = reg_open_env();
  
  // create pattern
  struct reg_pattern* pattern = reg_new_pattern(env, rule);

  // match pattern
  int success = reg_match(pattern, source, strlen(source));

  // free env
  reg_close_env(env);

see test/test_api.c testcase for detail.