zig-regex

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An automaton-based regex implementation for zig.

Note: This is still a work in progress and many things still need to be done.

• [x] Capture group support
• [ ] UTF-8 support
• [ ] More tests (plus some automated tests/fuzzing)
• [x] Add a PikeVM implementation
• [ ] Literal optimizations and just general performance improvements.

Usage

const debug = @import("std").debug;
const Regex = @import("regex.zig").Regex;

test "example" {
    var re = try Regex.compile(debug.global_allocator, "\\w+");

    debug.assert(try re.match("hej") == true);
}

Api

Regex

fn compile(a: &Allocator, re: []const u8) !Regex

Compiles a regex string, returning any errors during parsing/compiling.

pub fn match(re: &const Regex, input: []const u8) !bool

Match a compiled regex against some input. The input must be matched in its entirety and from the first index.

pub fn partialMatch(re: &const Regex, input: []const u8) !bool

Match a compiled regex against some input. Unlike match, this matches the leftmost and does not have to be anchored to the start of input.

pub fn captures(re: &const Regex, input: []const u8) !?Captures

Match a compiled regex against some input. Returns a list of all matching slices in the regex with the first (0-index) being the entire regex.

If no match was found, null is returned.

Captures

pub fn sliceAt(captures: &const Captures, n: usize) ?[]const u8

Return the sub-slice for the numbered capture group. 0 refers to the entire match.

pub fn boundsAt(captures: &const Captures, n: usize) ?Span

Return the lower and upper byte positions for the specified capture group.

We can retrieve the sub-slice using this function:

const span = caps.boundsAt(0)
debug.assert(mem.eql(u8, caps.sliceAt(0), input[span.lower..span.upper]));

References

See the following useful sources:

• https://swtch.com/~rsc/regexp/
• Rust Regex Library
• Go Regex Library