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Performance optimization for patterns like (^"foo") or (|"foo"|)

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Bruce Hill 2021-09-27 21:33:30 -07:00
parent 840d62a60a
commit b882e30bf7
1 changed files with 17 additions and 5 deletions
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22
match.c
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@ -231,9 +231,10 @@ static inline pat_t *deref(match_ctx_t *ctx, pat_t *pat)
//
// Find and return the first and simplest pattern that will definitely have to
// match for the whole pattern to match (if any)
// match for the whole pattern to match (if any). Ideally, this would be a
// string literal that can be quickly scanned for.
//
static pat_t *first_pat(match_ctx_t *ctx, pat_t *pat)
static pat_t *get_prerequisite(match_ctx_t *ctx, pat_t *pat)
{
for (pat_t *p = pat; p; ) {
switch (p->type) {
@ -245,7 +246,13 @@ static pat_t *first_pat(match_ctx_t *ctx, pat_t *pat)
p = p->args.repetitions.repeat_pat; break;
case BP_CAPTURE:
p = p->args.capture.capture_pat; break;
case BP_CHAIN: case BP_MATCH: case BP_NOT_MATCH:
case BP_CHAIN: {
pat_t *f = p->args.multiple.first;
// If pattern is something like (|"foo"|), then use "foo" as the first thing to scan for
p = (f->type == BP_WORD_BOUNDARY || f->type == BP_START_OF_LINE) ? p->args.multiple.second : f;
break;
}
case BP_MATCH: case BP_NOT_MATCH:
p = p->args.multiple.first; break;
case BP_REPLACE:
p = p->args.replace.pat; break;
@ -282,11 +289,13 @@ static match_t *_next_match(match_ctx_t *ctx, const char *str, pat_t *pat, pat_t
cache_destroy(ctx, NULL);
pat = deref(ctx, pat); // Avoid repeated lookups
pat_t *first = first_pat(ctx, pat);
pat_t *first = get_prerequisite(ctx, pat);
// Don't bother looping if this can only match at the start:
// Don't bother looping if this can only match at the start/end:
if (first->type == BP_START_OF_FILE)
return match(ctx, str, pat);
else if (first->type == BP_END_OF_FILE)
return match(ctx, ctx->end, pat);
// Performance optimization: if the pattern starts with a string literal,
// we can just rely on the highly optimized memmem() implementation to skip
@ -294,6 +303,9 @@ static match_t *_next_match(match_ctx_t *ctx, const char *str, pat_t *pat, pat_t
if (!skip && first->type == BP_STRING && first->min_matchlen > 0 && !ctx->ignorecase) {
char *found = memmem(str, (size_t)(ctx->end - str), first->args.string, first->min_matchlen);
str = found ? found : ctx->end;
} else if (!skip && str > ctx->start && (first->type == BP_START_OF_LINE || first->type == BP_END_OF_LINE)) {
char *found = memchr(str, '\n', (size_t)(ctx->end - str));
str = found ? (first->type == BP_START_OF_LINE ? found+1 : found) : ctx->end;
}
do {