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Performance optimization for common case where pattern starts with

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string
This commit is contained in:
Bruce Hill 2021-07-17 15:25:24 -07:00
parent ad85fb1da5
commit 85f6cb8e76
2 changed files with 45 additions and 2 deletions
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4
grammars/html.bp
View File

@ -14,9 +14,9 @@ void-element: `< ("area"/"base"/"br"/"col"/"embed"/"hr"/"img"/"input"/"link"/"me
template-element: "<template>" ..%(\n / comment / element) "</template>"
raw-element: `< @tag=("script"/"style"/"textarea"/"title") __attributes__ `> ..%\n ("</"tag__`>)
raw-element: `< @tag=("script"/"style"/"textarea"/"title") __attributes__ `> ..%\n "</"tag__`>
normal-element: `< @tag=id __attributes__ `> ..%(\n / comment / element) ("</"tag`>)
normal-element: `< @tag=id __attributes__ `> ..%(\n / comment / element) "</"tag__`>
comment: "<!--" ..%\n "-->"

43
match.c
View File

@ -61,11 +61,35 @@ static inline pat_t *deref(def_t *defs, pat_t *pat)
return pat;
}
//
// Find and return the first string literal to be matched (if any)
//
static pat_t *first_literal(def_t *defs, pat_t *pat)
{
for (pat_t *p = pat; p; ) {
if (p->type == BP_STRING)
return p;
else if (p->type == BP_BEFORE)
p = p->args.pat;
else if (p->type == BP_CAPTURE)
p = p->args.capture.capture_pat;
else if (p->type == BP_CHAIN)
p = p->args.multiple.first;
else if (p->type == BP_REPLACE)
p = p->args.replace.pat;
else if (p->type == BP_REF)
p = deref(defs, p);
else break;
}
return NULL;
}
//
// Find the next match after prev (or the first match if prev is NULL)
//
match_t *next_match(def_t *defs, file_t *f, match_t *prev, pat_t *pat, pat_t *skip, bool ignorecase)
{
pat = deref(defs, pat);
const char *str;
if (prev) {
str = prev->end > prev->start ? prev->end : prev->end + 1;
@ -74,6 +98,25 @@ match_t *next_match(def_t *defs, file_t *f, match_t *prev, pat_t *pat, pat_t *sk
str = f->start;
}
bool only_start = pat->type == BP_START_OF_FILE || (pat->type == BP_CHAIN && pat->args.multiple.first->type == BP_START_OF_FILE);
// Performance optimization: if the pattern starts with a string literal,
// we can just rely on the highly optimized strstr()/strcasestr()
// implementations to skip past areas where we know we won't find a match.
pat_t *first_str = first_literal(defs, pat);
if (first_str) {
for (size_t i = 0; i < first_str->min_matchlen; i++)
if (first_str->args.string[i] == '\0')
goto pattern_search;
char *tmp = strndup(first_str->args.string, first_str->min_matchlen);
char *found = (ignorecase ? strcasestr : strstr)(str, tmp);
if (found)
str = found;
else if (&str[strlen(str)] == f->end)
str = f->end+1;
free(tmp);
}
pattern_search:
while (str <= f->end) {
match_t *m = match(defs, f, str, pat, ignorecase);
if (m) return m;