Git/Packet.pm: extract parts of t0021/rot13-filter.pl for reuse

And while at it let's simplify t0021/rot13-filter.pl by
using Git/Packet.pm.

This will make it possible to reuse packet related
functions in other test scripts.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 169 insertions, 0 deletions

diff --git a/perl/Git/Packet.pm b/perl/Git/Packet.pm
new file mode 100644
index 0000000000..255b28c098
--- /dev/null
+++ b/perl/Git/Packet.pm
@@ -0,0 +1,168 @@
+package Git::Packet;
+use 5.008;
+use strict;
+use warnings;
+BEGIN {
+	require Exporter;
+	if ($] < 5.008003) {
+		*import = \&Exporter::import;
+	} else {
+		# Exporter 5.57 which supports this invocation was
+		# released with perl 5.8.3
+		Exporter->import('import');
+	}
+}
+
+our @EXPORT = qw(
+			packet_compare_lists
+			packet_bin_read
+			packet_txt_read
+			packet_required_key_val_read
+			packet_bin_write
+			packet_txt_write
+			packet_flush
+			packet_initialize
+			packet_read_capabilities
+			packet_read_and_check_capabilities
+			packet_check_and_write_capabilities
+		);
+our @EXPORT_OK = @EXPORT;
+
+sub packet_compare_lists {
+	my ($expect, @result) = @_;
+	my $ix;
+	if (scalar @$expect != scalar @result) {
+		return undef;
+	}
+	for ($ix = 0; $ix < $#result; $ix++) {
+		if ($expect->[$ix] ne $result[$ix]) {
+			return undef;
+		}
+	}
+	return 1;
+}
+
+sub packet_bin_read {
+	my $buffer;
+	my $bytes_read = read STDIN, $buffer, 4;
+	if ( $bytes_read == 0 ) {
+		# EOF - Git stopped talking to us!
+		return ( -1, "" );
+	} elsif ( $bytes_read != 4 ) {
+		die "invalid packet: '$buffer'";
+	}
+	my $pkt_size = hex($buffer);
+	if ( $pkt_size == 0 ) {
+		return ( 1, "" );
+	} elsif ( $pkt_size > 4 ) {
+		my $content_size = $pkt_size - 4;
+		$bytes_read = read STDIN, $buffer, $content_size;
+		if ( $bytes_read != $content_size ) {
+			die "invalid packet ($content_size bytes expected; $bytes_read bytes read)";
+		}
+		return ( 0, $buffer );
+	} else {
+		die "invalid packet size: $pkt_size";
+	}
+}
+
+sub remove_final_lf_or_die {
+	my $buf = shift;
+	unless ( $buf =~ s/\n$// ) {
+		die "A non-binary line MUST be terminated by an LF.\n"
+		    . "Received: '$buf'";
+	}
+	return $buf;
+}
+
+sub packet_txt_read {
+	my ( $res, $buf ) = packet_bin_read();
+	unless ( $res == -1 or $buf eq '' ) {
+		$buf = remove_final_lf_or_die($buf);
+	}
+	return ( $res, $buf );
+}
+
+sub packet_required_key_val_read {
+	my ( $key ) = @_;
+	my ( $res, $buf ) = packet_txt_read();
+	unless ( $res == -1 or ( $buf =~ s/^$key=// and $buf ne '' ) ) {
+		die "bad $key: '$buf'";
+	}
+	return ( $res, $buf );
+}
+
+sub packet_bin_write {
+	my $buf = shift;
+	print STDOUT sprintf( "%04x", length($buf) + 4 );
+	print STDOUT $buf;
+	STDOUT->flush();
+}
+
+sub packet_txt_write {
+	packet_bin_write( $_[0] . "\n" );
+}
+
+sub packet_flush {
+	print STDOUT sprintf( "%04x", 0 );
+	STDOUT->flush();
+}
+
+sub packet_initialize {
+	my ($name, $version) = @_;
+
+	packet_compare_lists([0, $name . "-client"], packet_txt_read()) ||
+		die "bad initialize";
+	packet_compare_lists([0, "version=" . $version], packet_txt_read()) ||
+		die "bad version";
+	packet_compare_lists([1, ""], packet_bin_read()) ||
+		die "bad version end";
+
+	packet_txt_write( $name . "-server" );
+	packet_txt_write( "version=" . $version );
+	packet_flush();
+}
+
+sub packet_read_capabilities {
+	my @cap;
+	while (1) {
+		my ( $res, $buf ) = packet_bin_read();
+		if ( $res == -1 ) {
+			die "unexpected EOF when reading capabilities";
+		}
+		return ( $res, @cap ) if ( $res != 0 );
+		$buf = remove_final_lf_or_die($buf);
+		unless ( $buf =~ s/capability=// ) {
+			die "bad capability buf: '$buf'";
+		}
+		push @cap, $buf;
+	}
+}
+
+# Read remote capabilities and check them against capabilities we require
+sub packet_read_and_check_capabilities {
+	my @required_caps = @_;
+	my ($res, @remote_caps) = packet_read_capabilities();
+	my %remote_caps = map { $_ => 1 } @remote_caps;
+	foreach (@required_caps) {
+		unless (exists($remote_caps{$_})) {
+			die "required '$_' capability not available from remote" ;
+		}
+	}
+	return %remote_caps;
+}
+
+# Check our capabilities we want to advertise against the remote ones
+# and then advertise our capabilities
+sub packet_check_and_write_capabilities {
+	my ($remote_caps, @our_caps) = @_;
+	foreach (@our_caps) {
+		unless (exists($remote_caps->{$_})) {
+			die "our capability '$_' is not available from remote"
+		}
+		packet_txt_write( "capability=" . $_ );
+	}
+	packet_flush();
+}
+
+1;
diff --git a/perl/Makefile b/perl/Makefile
index 15d96fcc7a..f657de20e3 100644
--- a/perl/Makefile
+++ b/perl/Makefile
@@ -30,6 +30,7 @@ instdir_SQ = $(subst ','\'',$(prefix)/lib)
 modules += Git
 modules += Git/I18N
 modules += Git/IndexInfo
+modules += Git/Packet
 modules += Git/SVN
 modules += Git/SVN/Memoize/YAML
 modules += Git/SVN/Fetcher