From: Eric Wong <e@yhbt.net>
Date: Sat, 9 May 2020 08:27:36 +0000 (+0000)
Subject: eml: reduce RE captures and possible side effects
X-Git-Tag: v1.5.0~7
X-Git-Url: http://www.git.stargrave.org/?p=public-inbox.git;a=commitdiff_plain;h=1e64f2f0450477ffbb95b887511bdeec28e30ab0

eml: reduce RE captures and possible side effects

Since Perl 5.6, the `@-' (aka @LAST_MATCH_START) and `@+' (aka
@LAST_MATCH_END) arrays provides integer offsets for every match
as documented in perlvar(1), regardless of regexp modifiers.

We can avoid relying on $1 in the epilogue scan, entirely.

So use these instead of relying on m//g and pos(), since the `g'
modifier can be affected by m//g matches performed in other
places.

Unrelated, but while we're in the area: remove some unnecessary
use of (?:...), too.
---

diff --git a/lib/PublicInbox/Eml.pm b/lib/PublicInbox/Eml.pm
index 4508bd84..80e7c1af 100644
--- a/lib/PublicInbox/Eml.pm
+++ b/lib/PublicInbox/Eml.pm
@@ -71,11 +71,11 @@ sub re_memo ($) {
 # compatible with our uses of Email::MIME
 sub new {
 	my $ref = ref($_[1]) ? $_[1] : \(my $cpy = $_[1]);
-	if ($$ref =~ /(?:\r?\n(\r?\n))/gs) { # likely
+	if ($$ref =~ /\r?\n(\r?\n)/s) { # likely
 		# This can modify $$ref in-place and to avoid memcpy/memmove
 		# on a potentially large $$ref.  It does need to make a
 		# copy for $hdr, though.  Idea stolen from Email::Simple
-		my $hdr = substr($$ref, 0, pos($$ref), ''); # sv_chop on $$ref
+		my $hdr = substr($$ref, 0, $+[0], ''); # sv_chop on $$ref
 		substr($hdr, -(length($1))) = ''; # lower SvCUR
 		bless { hdr => \$hdr, crlf => $1, bdy => $ref }, __PACKAGE__;
 	} elsif ($$ref =~ /^[a-z0-9-]+[ \t]*:/ims && $$ref =~ /(\r?\n)\z/s) {
@@ -90,8 +90,8 @@ sub new {
 sub new_sub {
 	my (undef, $ref) = @_;
 	# special case for messages like <85k5su9k59.fsf_-_@lola.goethe.zz>
-	$$ref =~ /\A(?:(\r?\n))/gs or goto &new;
-	my $hdr = substr($$ref, 0, pos($$ref), ''); # sv_chop on $$ref
+	$$ref =~ /\A(\r?\n)/s or goto &new;
+	my $hdr = substr($$ref, 0, $+[0], ''); # sv_chop on $$ref
 	bless { hdr => \$hdr, crlf => $1, bdy => $ref }, __PACKAGE__;
 }
 
@@ -132,8 +132,8 @@ sub mp_descend ($$) {
 	# *sigh* just the regexp match alone seems to bump RSS by
 	# length($$bdy) on a ~30M string:
 	my $epilogue_missing;
-	if ($$bdy =~ /((?:\r?\n)?^--$bnd--[ \t]*\r?$)/gsm) {
-		substr($$bdy, pos($$bdy) - length($1)) = '';
+	if ($$bdy =~ /(?:\r?\n)?^--$bnd--[ \t]*\r?$/sm) {
+		substr($$bdy, $-[0]) = '';
 	} else {
 		$epilogue_missing = 1;
 	}