From: Eric Wong <e@80x24.org>
Date: Mon, 26 Sep 2022 10:17:12 +0000 (+0000)
Subject: viewdiff: save memory by eliminating two captures
X-Git-Url: http://www.git.stargrave.org/?p=public-inbox.git;a=commitdiff_plain;h=06600f6ea9258425f4f7ff7a7b1f3d028d11b638

viewdiff: save memory by eliminating two captures

Avoid relying on $DIGIT captures when @- and @+ to access
last match start and end, respectively.  The elimination of
the post capture ought to allow the use of sv_chop to advance
the string start pointer without memory copies.

This ought to save 1-2MB of memory on my system since I've
noticed the captures was using a big chunk of scratchpad
space.
---

diff --git a/lib/PublicInbox/ViewDiff.pm b/lib/PublicInbox/ViewDiff.pm
index 9a7adb57..95bbf2d2 100644
--- a/lib/PublicInbox/ViewDiff.pm
+++ b/lib/PublicInbox/ViewDiff.pm
@@ -154,16 +154,16 @@ sub diff_header ($$$) {
 
 sub diff_before_or_after ($$) {
 	my ($ctx, $x) = @_;
-	if (exists $ctx->{-anchors} && $$x =~ /\A(.*?) # likely "---\n" # \$1
-			# diffstat lines:
-			((?:^\x20(?:[^\n]+?)(?:\x20+\|\x20[^\n]*\n))+)
-			(\x20[0-9]+\x20files?\x20)changed,
-			(.*?)\z/msx) { # notes, commit message, etc
-		my @x = ($4, $3, $2, $1);
-		undef $$x;
+	if (exists $ctx->{-anchors} && $$x =~ # diffstat lines:
+			/((?:^\x20(?:[^\n]+?)(?:\x20+\|\x20[^\n]*\n))+)
+			(\x20[0-9]+\x20files?\x20)changed,/msx) {
+		my $pre = substr($$x, 0, $-[0]); # (likely) short prefix
+		substr($$x, 0, $+[0], ''); # sv_chop on $$x ($$x may be long)
+		my @x = ($2, $1);
 		my $lnk = $ctx->{-linkify};
 		my $zfh = $ctx->{zfh};
-		print $zfh $lnk->to_html(pop @x); # $1 uninteresting prefix
+		# uninteresting prefix
+		print $zfh $lnk->to_html($pre);
 		for my $l (split(/^/m, pop(@x))) { # $2 per-file stat lines
 			$l =~ /^ (.+)( +\| .*\z)/s and
 				anchor0($ctx, $1, $2) and next;
@@ -173,7 +173,7 @@ sub diff_before_or_after ($$) {
 		print $zfh pop(@x), # $3 /^ \d+ files? /
 			qq(<a href="$ch">changed</a>,),
 			# insertions/deletions, notes, commit message, etc:
-			$lnk->to_html(@x);
+			$lnk->to_html($$x);
 	} else {
 		print { $ctx->{zfh} } $ctx->{-linkify}->to_html($$x);
 	}