Crate safe_regex

A safe regular expression library.

Features

• forbid(unsafe_code)
• Good test coverage (??%) - TODO(mleonhard) Update.
• Checks input in a single pass. Runtime and memory usage are both O(n * r * 2^g) where
  • n is the length of the data to check
  • r is the length of the regex
  • g is the number of capturing groups in the regex TODO(mleonhard) Confirm this with a benchmark.
• Rust compiler checks and optimizes the matcher
• Supports basic regular expression syntax:
  • Any byte: .
  • Sequences: abc
  • Classes: [-ab0-9], [^ab]
  • Repetition: a?, a*, a+, a{1}, a{1,}, a{,1}, a{1,2}, a{,}
  • Alternates: a|b|c
  • Capturing groups: a(b*)?

Limitations

• Only works on byte slices, not strings.
• Allocates. Uses std::collections::HashSet during matching.

Alternatives

• regex
  • Mature & Popular
  • Maintained by the core Rust language developers
  • Contains unsafe code.
• pcre2
  • Uses PCRE library which is written in unsafe C.
• regular-expression
  • No documentation
• rec

Cargo Geiger Safety Report

Examples

use safe_regex::{regex, Matcher};
let re: Matcher<_> = regex!(br"(ab)?c");
assert_eq!(None, re.match_all(b""));
assert_eq!(None, re.match_all(b"abcX"));

let groups1 = re.match_all(b"abc").unwrap();
assert_eq!(b"ab", groups1.group(0).unwrap());
assert_eq!(0..2, groups1.group_range(0).unwrap());

let groups2 = re.match_all(b"c").unwrap();
assert_eq!(None, groups2.group(0));
assert_eq!(None, groups2.group_range(0));

// groups2.group(1); // panics

Changelog

• v0.1.0 - First published version

TO DO

• DONE - Read about regular expressions
• DONE - Read about NFAs, https://swtch.com/~rsc/regexp/
• DONE - Design API
• DONE - Implement
• DONE - Add integration tests
• DONE - Add macro, regex!(r"[a-z][0-9]")
• Add fuzzing tests
• Add common character classes: whitespace, letters, punctuation, etc.
• Match strings

TO DO

• Add a memory-limited match_all fn, for use on untrusted data. Make it the default.
• Once const generics are stable, use the feature to simplify Repeat and other types.

Release Process

1. Edit Cargo.toml and bump version number.
2. Run ./release.sh

Modules

internal

Macros

regex

Compiles a regular expression into a Rust type.

Structs

Groups	Groups captured by a regular expression.
Matcher	A compiled regular expression.