git-http-backend: start refactoring to use callback

Designing for asynchronous, non-blocking operations makes
adapting for synchronous, blocking operation easy.

Going the other way around is not easy, so do it now and
allow us to be more easily adapted for non-blocking use
in the next commit...

1 files changed, 47 insertions, 26 deletions

diff --git a/lib/PublicInbox/GitHTTPBackend.pm b/lib/PublicInbox/GitHTTPBackend.pm
index cba025e7..3cf78579 100644
--- a/lib/PublicInbox/GitHTTPBackend.pm
+++ b/lib/PublicInbox/GitHTTPBackend.pm
@@ -178,34 +178,55 @@ sub serve_smart {
                 my @cmd = qw(git http-backend);
                 exec(@cmd) or die 'exec `' . join(' ', @cmd). "' failed: $!\n";
         }
-        $wpipe = undef;
-        $in = undef;
-        my @h;
-        my $code = 200;
-        {
-                local $/ = "\r\n";
-                while (defined(my $line = <$rpipe>)) {
-                        if ($line =~ /\AStatus:\s*(\d+)/) {
-                                $code = $1;
-                        } else {
-                                chomp $line;
-                                last if $line eq '';
-                                push @h, split(/:\s*/, $line, 2);
-                        }
+        $wpipe = $in = undef;
+        $rpipe->blocking(0);
+        $buf = '';
+        my $vin;
+        vec($vin, fileno($rpipe), 1) = 1;
+        my ($fh, $res);
+        my $fail = sub {
+                my ($e) = @_;
+                if ($e eq 'EAGAIN') {
+                        select($vin, undef, undef, undef);
+                } else {
+                        $rpipe = undef;
+                        $fh->close if $fh;
+                        $err->print('git http-backend error: ', $e, "\n");
                 }
-        }
-        return if $code == 403;
-        sub {
-                my ($cb) = @_;
-                my $fh = $cb->([ $code, \@h ]);
-                while (1) {
-                        my $r = sysread($rpipe, $buf, 8192);
-                        die "$!\n" unless defined $r;
-                        last if ($r == 0);
-                        $fh->write($buf);
+        };
+        my $cb = sub {
+                my $r = sysread($rpipe, $buf, 8192, length($buf));
+                return $fail->($!{EAGAIN} ? 'EAGAIN' : $!) unless defined $r;
+                if ($r == 0) { # EOF
+                        $rpipe = undef;
+                        $fh->close if $fh;
+                        return;
                 }
-                $fh->close;
-        }
+                if ($fh) { # stream body from git-http-backend to HTTP client
+                        $fh->write($buf);
+                        $buf = '';
+                } elsif ($buf =~ s/\A(.*?)\r?\n\r?\n//s) { # parse headers
+                        my $h = $1;
+                        my $code = 200;
+                        my @h;
+                        foreach my $l (split(/\r?\n/, $h)) {
+                                my ($k, $v) = split(/:\s*/, $l, 2);
+                                if ($k =~ /\AStatus\z/i) {
+                                        $code = int($v);
+                                } else {
+                                        push @h, $k, $v;
+                                }
+                        }
+                        # write response header:
+                        $fh = $res->([ $code, \@h ]);
+                        $fh->write($buf);
+                        $buf = '';
+                } # else { keep reading ... }
+        };
+        sub {
+                ($res) = @_;
+                while ($rpipe) { $cb->() }
+        };
 }
 
 1;