lei: micro-optimize startup time

We'll use lower-level Socket and avoid IO::Socket::UNIX,
use Cwd::fastcwd(*), avoid IO::Handle->autoflush by
using the select operator, and reuse buffer for reading
the socket while avoiding unnecessary $/ localization
in a tiny script.

All these things adds up to ~5-10 ms savings on my loaded
system.

(*) caveats about fastcwd won't apply since lei won't work
    in removed directories.

1 files changed, 17 insertions, 16 deletions

diff --git a/script/lei b/script/lei
index e59e4316..2b041fb4 100755
--- a/script/lei
+++ b/script/lei
@@ -3,8 +3,7 @@
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict;
 use v5.10.1;
-use Cwd qw(cwd);
-use IO::Socket::UNIX;
+use Socket qw(AF_UNIX SOCK_STREAM pack_sockaddr_un);
 
 if (eval { require IO::FDPass; 1 }) { # use daemon to reduce load time
         my $path = do {
@@ -13,14 +12,15 @@ if (eval { require IO::FDPass; 1 }) { # use daemon to reduce load time
                         require File::Spec;
                         $runtime_dir = File::Spec->tmpdir."/lei-$<";
                 }
-                unless (-d $runtime_dir && -w _) {
+                unless (-d $runtime_dir) {
                         require File::Path;
                         File::Path::mkpath($runtime_dir, 0, 0700);
                 }
                 "$runtime_dir/sock";
         };
-        my $sock = IO::Socket::UNIX->new(Peer => $path, Type => SOCK_STREAM);
-        unless ($sock) { # start the daemon if not started
+        my $addr = pack_sockaddr_un($path);
+        socket(my $sock, AF_UNIX, SOCK_STREAM, 0) or die "socket: $!";
+        unless (connect($sock, $addr)) { # start the daemon if not started
                 my $err = $! + 0;
                 my $env = { PERL5LIB => join(':', @INC) };
                 my $cmd = [ $^X, qw[-MPublicInbox::LEI
@@ -31,13 +31,14 @@ if (eval { require IO::FDPass; 1 }) { # use daemon to reduce load time
                 warn "lei-daemon exited with \$?=$?\n" if $?;
 
                 # try connecting again anyways, unlink+bind may be racy
-                $sock = IO::Socket::UNIX->new(Peer => $path,
-                                                Type => SOCK_STREAM) // die
+                connect($sock, $addr) or die
                         "connect($path): $! (after attempted daemon start)";
         }
-        my $pwd = $ENV{PWD};
-        my $cwd = cwd();
-        if ($pwd) { # prefer ENV{PWD} if it's a symlink to real cwd
+        require Cwd;
+        my $cwd = Cwd::fastcwd() // die "fastcwd: $!";
+        my $pwd = $ENV{PWD} // '';
+        if ($pwd eq $cwd) { # likely, all good
+        } elsif ($pwd) { # prefer ENV{PWD} if it's a symlink to real cwd
                 my @st_cwd = stat($cwd) or die "stat(cwd=$cwd): $!\n";
                 my @st_pwd = stat($pwd);
                 # make sure st_dev/st_ino match for {PWD} to be valid
@@ -47,16 +48,16 @@ if (eval { require IO::FDPass; 1 }) { # use daemon to reduce load time
                 $pwd = $cwd;
         }
         local $ENV{PWD} = $pwd;
-        $sock->autoflush(1);
-        IO::FDPass::send(fileno($sock), $_) for (0..2);
         my $buf = "$$\0\0>" . join("]\0[", @ARGV) . "\0\0>";
         while (my ($k, $v) = each %ENV) { $buf .= "$k=$v\0" }
         $buf .= "\0\0";
+        select $sock;
+        $| = 1; # unbuffer selected $sock
+        IO::FDPass::send(fileno($sock), $_) for (0..2);
         print $sock $buf or die "print(sock, buf): $!";
-        local $/ = "\n";
-        while (my $line = <$sock>) {
-                $line =~ /\Aexit=([0-9]+)\n\z/ and exit($1 + 0);
-                die $line;
+        while ($buf = <$sock>) {
+                $buf =~ /\Aexit=([0-9]+)\n\z/ and exit($1 + 0);
+                die $buf;
         }
 } else { # for systems lacking IO::FDPass
         require PublicInbox::LEI;