m4_qlen speedup

[Eric Blake]

Phooey.  I meant to commit this linearly (and after a review), but goofed up my 
git repository and ended up pushing a merge instead.  At any rate, the damage 
is done (I don't feel like rewinding the master branch of savannah's git 
repository), so here's what I committed.  The idea here is that m4_qlen can be 
done via a single builtin m4_patsubst, rather than a series of macro expansions 
through the multi-level m4_patsubsts, making m4_qlen faster when quadrigraphs 
are present.  Or put another way, since we already have a regex with 
alternation, we can use that alternation to our advantage rather than needing a 
separate m4_if.  However, thanks to my patch last year that avoids the regex 
altogether if the string has no @ characters, the gains are not usually in a 
hot path (for example, coreutils does not use quadrigraphs in its configure.ac).

From: Eric Blake <address@hidden>
Date: Tue, 15 Jan 2008 08:49:08 -0700
Subject: [PATCH] * lib/m4sugar/m4sugar.m4 (m4_qlen): Use fewer macros.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog              |    4 ++++
 lib/m4sugar/m4sugar.m4 |    9 +++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 107d031..5f70b64 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2008-01-15  Eric Blake  <address@hidden>
+
+       * lib/m4sugar/m4sugar.m4 (m4_qlen): Use fewer macros.
+
 2008-01-08  Ralf Wildenhues  <address@hidden>
 
        * tests/Makefile.am (noinst_SCRIPTS): Renamed from
diff --git a/lib/m4sugar/m4sugar.m4 b/lib/m4sugar/m4sugar.m4
index c73a940..e831555 100644
--- a/lib/m4sugar/m4sugar.m4
+++ b/lib/m4sugar/m4sugar.m4
@@ -3,8 +3,8 @@ divert(-1)#                                                  -*-
 Autoconf -*-
 # Base M4 layer.
 # Requires GNU M4.
 #
-# Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free
-# Software Foundation, Inc.
+# Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
+# 2008 Free Software Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -1760,7 +1760,7 @@ m4_define([m4_flatten],
 #    => active activeend
 #
 # First, notice that we guarantee trailing space.  Why?  Because regular
-# expressions are greedy, and `.* ?' would alway groups the space into the
+# expressions are greedy, and `.* ?' would always group the space into the
 # .* portion.  The algorithm is simpler by avoiding `?' at the end.  The
 # algorithm correctly strips everything if STRING is just ` '.
 #
@@ -2032,7 +2032,8 @@ m4_builtin([popdef], [m4_Border])dnl
 # Avoid bpatsubsts for the common case of no quadrigraphs.
 m4_define([m4_qlen],
 [m4_if(m4_index([$1], address@hidden), [-1], [m4_len([$1])],
-       [m4_len(m4_bpatsubsts([[$1]], address@hidden(<:\|:>\|S|\|%:\)@], [P], 
[@&address@hidden))])])
+       [m4_len(m4_bpatsubst([[$1]], 
address@hidden(\(<:\|:>\|S|\|%:\)\(@\)\|&address@hidden)],
+                           [\3]))])])
 
 
 # m4_qdelta(STRING)
-- 
1.5.3.8