sed and gawk use fastmap in regex, but grep does not. By using fastmap,
I expect that grep speeds up for patterns as regex is used.
before:
$ time -p env LC_ALL=ja_JP.eucjp src/grep '\([a-b]\)\1' k
real 7.83
user 7.62
sys 0.07
after:
$ time -p env LC_ALL=ja_JP.eucjp src/grep '\([a-b]\)\1' k
real 0.46
user 0.38
sys 0.07
However, if grep uses fastmap, fails in case-fold-titlecase test. It
means that grep's behavior differ from sed and gawk, as they use fastmap,
although it seems to be a bug in regex.
From 1337006597a7d7e14993af14e57d47d6b483fb0d Mon Sep 17 00:00:00 2001
From: Norihiro Tanaka <nori...@kcn.ne.jp>
Date: Sun, 17 Jul 2016 01:25:18 +0900
Subject: [PATCH] grep: use fastmap in regex
* src/dfasearch.c (GEAcompile): Use fastmap in regex.
---
src/dfasearch.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/src/dfasearch.c b/src/dfasearch.c
index 8052ef0..e5223e5 100644
--- a/src/dfasearch.c
+++ b/src/dfasearch.c
@@ -154,6 +154,9 @@ GEAcompile (char const *pattern, size_t size, reg_syntax_t
syntax_bits)
patterns = xnrealloc (patterns, pcount + 1, sizeof *patterns);
patterns[pcount] = patterns0;
+ patterns[pcount].regexbuf.fastmap =
+ = xmalloc ((UCHAR_MAX + 1) * sizeof (char));
+
char const *err = re_compile_pattern (p, len,
&(patterns[pcount].regexbuf));
if (err)
--
1.7.1
