regex's Introduction

regex

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

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

subset DFA
backreference
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);