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From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH 09/10] config: config_fh_parse: micro-optimize
Date: Wed, 23 Dec 2020 08:38:52 +0000
Message-Id: <20201223083853.30721-10-e@80x24.org>
In-Reply-To: <20201223083853.30721-1-e@80x24.org>
References: <20201223083853.30721-1-e@80x24.org>
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We can avoid a slow regexp capture and instead and rely on
rindex + substr to extract the section from the config file.

Then we use the defined-or-assignment (//=) operator combined
with the documented return value of `push' to ensure @section_order
is unique without repeating a hash lookup.

Finally, we avoid short-lived variables inside the loop and
declare them subroutine-wide to knock a teeny bit of allocation
time.

Combined, these optimizations bring the ~1.22s
PublicInbox::Config->new time down to ~0.98s with 50K inboxes.
---
 lib/PublicInbox/Config.pm | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/lib/PublicInbox/Config.pm b/lib/PublicInbox/Config.pm
index 4d143c6e..60107d45 100644
--- a/lib/PublicInbox/Config.pm
+++ b/lib/PublicInbox/Config.pm
@@ -132,20 +132,15 @@ sub default_file {
 
 sub config_fh_parse ($$$) {
 	my ($fh, $rs, $fs) = @_;
-	my %rv;
-	my (%section_seen, @section_order);
+	my (%rv, %section_seen, @section_order, $line, $k, $v, $section, $cur);
 	local $/ = $rs;
-	while (defined(my $line = <$fh>)) {
+	while (defined($line = <$fh>)) { # performance critical with giant configs
 		chomp $line;
-		my ($k, $v) = split($fs, $line, 2);
-		my ($section) = ($k =~ /\A(\S+)\.[^\.]+\z/);
-		unless (defined $section_seen{$section}) {
-			$section_seen{$section} = 1;
-			push @section_order, $section;
-		}
+		($k, $v) = split($fs, $line, 2);
+		$section = substr($k, 0, rindex($k, '.'));
+		$section_seen{$section} //= push(@section_order, $section);
 
-		my $cur = $rv{$k};
-		if (defined $cur) {
+		if (defined($cur = $rv{$k})) {
 			if (ref($cur) eq "ARRAY") {
 				push @$cur, $v;
 			} else {