Hi Ævar,
On Wed, 26 Jun 2019, Ævar Arnfjörð Bjarmason wrote:
> Bring back optimized fixed-string search for "grep", this time with
> PCRE v2 as an optional backend. As noted in [1] with kwset we were
> slower than PCRE v1 and v2 JIT with the kwset backend, so that
> optimization was counterproductive.
>
> This brings back the optimization for "-F", without changing the
> semantics of "\0" in patterns. As seen in previous commits in this
> series we could support it now, but I'd rather just leave that
> edge-case aside so the tests don't need to do one thing or the other
> depending on what --fixed-strings backend we're using.
Nice. Very, very nice.
> I could also support the v1 backend here, but that would make the code
> more complex, and I'd rather aim for simplicity here and in future
> changes to the diffcore. We're not going to have someone who
> absolutely must have faster search, but for whom building PCRE v2
> isn't acceptable.
I could not agree more.
> diff --git a/grep.c b/grep.c
> index 4716217837..6b75d5be68 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -356,6 +356,18 @@ static NORETURN void compile_regexp_failed(const struct grep_pat *p,
> die("%s'%s': %s", where, p->pattern, error);
> }
>
> +static int is_fixed(const char *s, size_t len)
> +{
> + size_t i;
> +
> + for (i = 0; i < len; i++) {
> + if (is_regex_special(s[i]))
> + return 0;
> + }
> +
> + return 1;
> +}
> +
> #ifdef USE_LIBPCRE1
> static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
> {
> @@ -602,7 +614,6 @@ static int pcre2match(struct grep_pat *p, const char *line, const char *eol,
> static void free_pcre2_pattern(struct grep_pat *p)
> {
> }
> -#endif /* !USE_LIBPCRE2 */
Huh? Removing an `#endif` without removing the corresponding `#if`?
... but...
> static void compile_fixed_regexp(struct grep_pat *p, struct grep_opt *opt)
> {
> @@ -623,11 +634,13 @@ static void compile_fixed_regexp(struct grep_pat *p, struct grep_opt *opt)
> compile_regexp_failed(p, errbuf);
> }
> }
> +#endif /* !USE_LIBPCRE2 */
Ah hah!
If we would not have plenty of exercise for the PCRE2 build options, I
would be worried. But AFAICT the CI build includes this all the time, so
we're fine.
> static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
> {
> int err;
> int regflags = REG_NEWLINE;
> + int pat_is_fixed;
>
> p->word_regexp = opt->word_regexp;
> p->ignore_case = opt->ignore_case;
> @@ -636,8 +649,38 @@ static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
> if (memchr(p->pattern, 0, p->patternlen) && !opt->pcre2)
> die(_("given pattern contains NULL byte (via -f <file>). This is only supported with -P under PCRE v2"));
>
> - if (opt->fixed) {
> + pat_is_fixed = is_fixed(p->pattern, p->patternlen);
> + if (opt->fixed || pat_is_fixed) {
> +#ifdef USE_LIBPCRE2
> + opt->pcre2 = 1;
> + if (pat_is_fixed) {
> + compile_pcre2_pattern(p, opt);
> + } else {
> + /*
> + * E.g. t7811-grep-open.sh relies on the
> + * pattern being restored, and unfortunately
> + * there's no PCRE compile flag for "this is
> + * fixed", so we need to munge it to
> + * "\Q<pat>\E".
> + */
> + char *old_pattern = p->pattern;
> + size_t old_patternlen = p->patternlen;
> + struct strbuf sb = STRBUF_INIT;
> +
> + strbuf_add(&sb, "\\Q", 2);
> + strbuf_add(&sb, p->pattern, p->patternlen);
> + strbuf_add(&sb, "\\E", 2);
> +
> + p->pattern = sb.buf;
> + p->patternlen = sb.len;
> + compile_pcre2_pattern(p, opt);
> + p->pattern = old_pattern;
> + p->patternlen = old_patternlen;
> + strbuf_release(&sb);
> + }
> +#else
> compile_fixed_regexp(p, opt);
> +#endif
It might be a bit easier to read if the shorter clause came first.
Other than that: what a nice read. I should save reviewing all your patch
series for just-before-bed time.
Thanks,
Dscho
> return;
> }
>
> --
> 2.22.0.455.g172b71a6c5
>
>
