From b140961420c0f240c9c3f55e83c52cfc3efa709d Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Thu, 17 Dec 2015 05:37:31 +0000
Subject: git: cat-file wrapper enhancements

The "cat_file" sub now allows a block to be passed for partial
processing.  Additionally, a new "check" method is added to
retrieve only object metadata: (SHA-1 identifier, type, size)
---
 lib/PublicInbox/GitCatFile.pm | 125 ++++++++++++++++++++++++++++--------------
 1 file changed, 83 insertions(+), 42 deletions(-)

(limited to 'lib')

diff --git a/lib/PublicInbox/GitCatFile.pm b/lib/PublicInbox/GitCatFile.pm
index dd95d5f3..b3666a08 100644
--- a/lib/PublicInbox/GitCatFile.pm
+++ b/lib/PublicInbox/GitCatFile.pm
@@ -17,75 +17,116 @@ sub new {
 	bless { git_dir => $git_dir }, $class
 }
 
-sub _cat_file_begin {
-	my ($self) = @_;
-	return if $self->{pid};
+sub _bidi_pipe {
+	my ($self, $batch, $in, $out, $pid) = @_;
+	return if $self->{$pid};
 	my ($in_r, $in_w, $out_r, $out_w);
 
-	pipe($in_r, $in_w) or die "pipe failed: $!\n";
-	pipe($out_r, $out_w) or die "pipe failed: $!\n";
+	pipe($in_r, $in_w) or fail($self, "pipe failed: $!");
+	pipe($out_r, $out_w) or fail($self, "pipe failed: $!");
 
-	my @cmd = ('git', "--git-dir=$self->{git_dir}", qw(cat-file --batch));
-	my $pid = fork;
-	defined $pid or die "fork failed: $!\n";
-	if ($pid == 0) {
+	my @cmd = ('git', "--git-dir=$self->{git_dir}", qw(cat-file), $batch);
+	$self->{$pid} = fork;
+	defined $self->{$pid} or fail($self, "fork failed: $!");
+	if ($self->{$pid} == 0) {
 		dup2(fileno($out_r), 0) or die "redirect stdin failed: $!\n";
 		dup2(fileno($in_w), 1) or die "redirect stdout failed: $!\n";
 		exec(@cmd) or die 'exec `' . join(' '). "' failed: $!\n";
 	}
-	close $out_r or die "close failed: $!\n";
-	close $in_w or die "close failed: $!\n";
+	close $out_r or fail($self, "close failed: $!");
+	close $in_w or fail($self, "close failed: $!");
 	$out_w->autoflush(1);
-
-	$self->{in} = $in_r;
-	$self->{out} = $out_w;
-	$self->{pid} = $pid;
+	$self->{$out} = $out_w;
+	$self->{$in} = $in_r;
 }
 
 sub cat_file {
-	my ($self, $object, $sizeref) = @_;
+	my ($self, $obj, $ref) = @_;
 
-	$self->_cat_file_begin;
-	print { $self->{out} } $object, "\n" or die "pipe write error: $!\n";
+	$self->_bidi_pipe(qw(--batch in out pid));
+	$self->{out}->print($obj, "\n") or fail($self, "write error: $!");
 
 	my $in = $self->{in};
-	my $head = <$in>;
+	my $head = $in->getline;
 	$head =~ / missing$/ and return undef;
 	$head =~ /^[0-9a-f]{40} \S+ (\d+)$/ or
-		die "Unexpected result from git cat-file: $head\n";
+		fail($self, "Unexpected result from git cat-file: $head");
 
 	my $size = $1;
-	$$sizeref = $size if $sizeref;
-	my $bytes_left = $size;
-	my $offset = 0;
-	my $rv = '';
-
-	while ($bytes_left) {
-		my $read = read($in, $rv, $bytes_left, $offset);
-		defined($read) or die "sysread pipe failed: $!\n";
-		$bytes_left -= $read;
-		$offset += $read;
-	}
+	my $ref_type = $ref ? ref($ref) : '';
+
+	my $rv;
+	my $left = $size;
+	$$ref = $size if ($ref_type eq 'SCALAR');
+	my $cb_err;
 
-	my $read = read($in, my $buf, 1);
-	defined($read) or die "read pipe failed: $!\n";
-	if ($read != 1 || $buf ne "\n") {
-		die "newline missing after blob\n";
+	if ($ref_type eq 'CODE') {
+		$rv = eval { $ref->($in, \$left) };
+		$cb_err = $@;
+		# drain the rest
+		my $max = 8192;
+		while ($left > 0) {
+			my $r = read($in, my $x, $left > $max ? $max : $left);
+			defined($r) or fail($self, "read failed: $!");
+			$r == 0 and fail($self, 'exited unexpectedly');
+			$left -= $r;
+		}
+	} else {
+		my $offset = 0;
+		my $buf = '';
+		while ($left > 0) {
+			my $r = read($in, $buf, $left, $offset);
+			defined($r) or fail($self, "read failed: $!");
+			$r == 0 and fail($self, 'exited unexpectedly');
+			$left -= $r;
+			$offset += $r;
+		}
+		$rv = \$buf;
 	}
-	\$rv;
+
+	my $r = read($in, my $buf, 1);
+	defined($r) or fail($self, "read failed: $!");
+	fail($self, 'newline missing after blob') if ($r != 1 || $buf ne "\n");
+	die $cb_err if $cb_err;
+
+	$rv;
 }
 
-sub DESTROY {
-	my ($self) = @_;
-	my $pid = $self->{pid} or return;
-	$self->{pid} = undef;
-	foreach my $f (qw(in out)) {
+sub check {
+	my ($self, $obj) = @_;
+	$self->_bidi_pipe(qw(--batch-check in_c out_c pid_c));
+	$self->{out_c}->print($obj, "\n") or fail($self, "write error: $!");
+	chomp(my $line = $self->{in_c}->getline);
+	my ($hex, $type, $size) = split(' ', $line);
+	return if $type eq 'missing';
+	($hex, $type, $size);
+}
+
+sub _destroy {
+	my ($self, $in, $out, $pid) = @_;
+	my $p = $self->{$pid} or return;
+	$self->{$pid} = undef;
+	foreach my $f ($in, $out) {
 		my $fh = $self->{$f};
 		defined $fh or next;
 		close $fh;
 		$self->{$f} = undef;
 	}
-	waitpid $pid, 0;
+	waitpid $p, 0;
+}
+
+sub fail {
+	my ($self, $msg) = @_;
+	cleanup($self);
+	die $msg;
 }
 
+sub cleanup {
+	my ($self) = @_;
+	_destroy($self, qw(in out pid));
+	_destroy($self, qw(in_c out_c pid_c));
+}
+
+sub DESTROY { cleanup(@_) }
+
 1;
-- 
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