~sircmpwn/hare

bf1e316aced9e60aeb4d85bc38fa3158544eaf6c — Max Schillinger a month ago 51d4feb
regex: implement multiple alternation

Example: The regex pattern `(ha|py|sh)` is implemented using the
following Hare Regular Expression Engine Virtual Machine NFA
Representation:

 0 groupstart
 1 split → 5 (split)
 2 lit h
 3 lit a
 4 jump → 11 (groupend)
 5 split → 9 (s)
 6 lit p
 7 lit y
 8 jump → 11 (groupend)
 9 lit s
10 lit h
11 groupend

Implements: https://todo.sr.ht/~sircmpwn/hare/696
Signed-off-by: Max Schillinger <max@mxsr.de>
2 files changed, 17 insertions(+), 15 deletions(-)

M regex/+test.ha
M regex/regex.ha
M regex/+test.ha => regex/+test.ha +3 -3
@@ 581,9 581,9 @@ fn run_rawreplace_case(
		(`ab|cd`, "cd", matchres::MATCH, 0, 2),
		(`ab|cd`, "abc", matchres::MATCH, 0, 2),
		(`ab|cd`, "abcd", matchres::MATCH, 0, 2),
		// TODO: multiple alternation
		// (`a|b|c|d|e`, "e", matchres::MATCH, 0, -1),
		// (`(a|b|c|d|e)f`, "ef", matchres::MATCH, 0, -1),
		// multiple alternation
		(`a|b|c|d|e`, "e", matchres::MATCH, 0, -1),
		(`(a|b|c|d|e)f`, "ef", matchres::MATCH, 0, -1),
		// TODO: nested capture groups
		(`((a))`, "abc", matchres::ERROR, 0, -1),
		// (`((a))`, "abc", matchres::MATCH, 0, -1),

M regex/regex.ha => regex/regex.ha +14 -12
@@ 223,7 223,7 @@ export fn compile(expr: str) (regex | error) = {
	let iter = strings::iter(expr);
	let r_idx = 0z;
	let anchored = false;
	let curr_alt_jump_idx = -1;
	let jump_idxs: []size = [];
	let in_bracket = false;
	let skip_charclass_rest = false;
	let bracket_idx = -1;


@@ 292,12 292,11 @@ export fn compile(expr: str) (regex | error) = {
			};
			n_groupstarts -= 1;
			append(insts, void: inst_groupend);
			if (curr_alt_jump_idx != -1) {
				assert(insts[curr_alt_jump_idx] is inst_jump);
				insts[curr_alt_jump_idx] =
					(len(insts) - 1): inst_jump;
				curr_alt_jump_idx = -1;
			for (let jump_idx .. jump_idxs) {
				assert(insts[jump_idx] is inst_jump);
				insts[jump_idx] = (len(insts) - 1): inst_jump;
			};
			jump_idxs = [];
		case '|' =>
			append(insts, types::SIZE_MAX: inst_jump);
			const origin = match (find_last_groupstart(&insts)) {


@@ 307,8 306,11 @@ export fn compile(expr: str) (regex | error) = {
				yield sz + 1;
			};
			const newinst = (len(insts) + 1): inst_split;
			insert(insts[origin], newinst);
			curr_alt_jump_idx = (len(insts) - 1): int;
			// add split after last jump (if any) or at origin
			const split_idx = if (len(jump_idxs) > 0)
				jump_idxs[len(jump_idxs) - 1] + 1 else origin;
			insert(insts[split_idx], newinst);
			append(jump_idxs, len(insts) - 1);
		case '{' =>
			let origin = len(insts) - 1;
			if (insts[origin] is inst_groupend) {


@@ 400,11 402,11 @@ export fn compile(expr: str) (regex | error) = {
	};

	// handle whole expression alternation
	if (curr_alt_jump_idx != -1) {
		assert(insts[curr_alt_jump_idx] is inst_jump);
		insts[curr_alt_jump_idx] = len(insts): inst_jump;
		curr_alt_jump_idx = -1;
	for (let jump_idx .. jump_idxs) {
		assert(insts[jump_idx] is inst_jump);
		insts[jump_idx] = len(insts): inst_jump;
	};
	jump_idxs = [];

	append(insts, anchored: inst_match);