[PATCHv2 3/5] Git.pm: allow pipes to be closed prior to calling command_close_bidi_pipe

From

MNMichal Nazarewicz <mpn@google.com>

Date

Feb 7, 2013, 14:01 UTC

Message-ID

<afa54fb5dd2d08759317099d10090b81adfb593f.1360242782.git.mina86@mina86.com>

In-Reply-To

<cover.1360242782.git.mina86@mina86.com>

From: Michal Nazarewicz <mina86@mina86.com>

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
---
 perl/Git.pm | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

 > On Wed, Feb 06, 2013 at 09:47:04PM +0100, Michal Nazarewicz wrote:
 >> This allows for something like:
 >> 
 >>   my ($pid, $in, $out, $ctx) = command_bidi_pipe(...);
 >>   print $out "write data";
 >>   close $out;
 >>   # ... do stuff with $in
 >>   command_close_bidi_pipe($pid, $in, undef, $ctx);

 On Thu, Feb 07 2013, Jeff King <peff@peff.net> wrote:
 > Should this part go into the documentation for command_close_bidi_pipe
 > in Git.pm?

 Done.

diff --git a/perl/Git.pm b/perl/Git.pm
index 11f310a..9dded54 100644
--- a/perl/Git.pm
+++ b/perl/Git.pm
@@ -426,13 +426,26 @@ Note that you should not rely on whatever actually is in C<CTX>;
 currently it is simply the command name but in future the context might
 have more complicated structure.
 
+C<PIPE_IN> and C<PIPE_OUT> may be C<undef> if they have been closed prior to
+calling this function.  This may be useful in a query-response type of
+commands where caller first writes a query and later reads response, eg:
+
+	my ($pid, $in, $out, $ctx) = $r->command_bidi_pipe('cat-file --batch-check');
+	print $out "000000000\n";
+	close $out;
+	while (<$in>) { ... }
+	$r->command_close_bidi_pipe($pid, $in, undef, $ctx);
+
+This idiom may prevent potential dead locks caused by data sent to the output
+pipe not being flushed and thus not reaching the executed command.
+
 =cut
 
 sub command_close_bidi_pipe {
 	local $?;
 	my ($self, $pid, $in, $out, $ctx) = _maybe_self(@_);
 	foreach my $fh ($in, $out) {
-		unless (close $fh) {
+		if (defined $fh && !close $fh) {
 			if ($!) {
 				carp "error closing pipe: $!";
 			} elsif ($? >> 8) {

-- 
1.8.1.2.549.g1d13f9f