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Cleanup on left recursion code

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This commit is contained in:
Bruce Hill 2021-10-01 20:04:12 -07:00
parent 0ad64a1006
commit 9648eb66d3
1 changed files with 12 additions and 24 deletions
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36
match.c
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@ -602,10 +602,8 @@ static match_t *match(match_ctx_t *ctx, const char *str, pat_t *pat)
pat_t rec_op = {
.type = BP_LEFTRECURSION,
.start = ref->start,
.end = ref->end,
.min_matchlen = 0,
.max_matchlen = -1,
.start = ref->start, .end = ref->end,
.min_matchlen = 0, .max_matchlen = -1,
.args.leftrec = {
.match = NULL,
.visits = 0,
@ -627,31 +625,21 @@ static match_t *match(match_ctx_t *ctx, const char *str, pat_t *pat)
},
};
const char *prev = str;
match_t *m = match(&ctx2, str, ref);
if (m == NULL) {
cache_failure(ctx, str, pat);
return NULL;
}
while (rec_op.args.leftrec.visits > 0) {
rec_op.args.leftrec.visits = 0;
if (rec_op.args.leftrec.match && rec_op.args.leftrec.match != m)
recycle_match(&rec_op.args.leftrec.match);
match_t *m = NULL;
// Keep matching as long as left recursion keeps happening and forward progress is made
for (const char *prev = str; m == NULL || (rec_op.args.leftrec.visits > 0 && m->end > prev); prev = m->end) {
rec_op.args.leftrec.match = m;
prev = m->end;
rec_op.args.leftrec.visits = 0;
match_t *m2 = match(&ctx2, str, ref);
if (m2 == NULL) break;
if (m2->end <= prev) {
recycle_match(&m2);
break;
}
recycle_match(&m);
if (!m2) break;
if (m) recycle_match(&m);
m = m2;
}
if (rec_op.args.leftrec.match && rec_op.args.leftrec.match != m)
recycle_match(&rec_op.args.leftrec.match);
if (!m) {
cache_failure(ctx, str, pat);
return NULL;
}
// This match wrapper mainly exists for record-keeping purposes.
// It also helps with visualization of match results.