~al-maisan/ubuntu/karmic/pristine-tar/gendelta-fix

#!/usr/bin/perl

=head1 NAME

pristine-gz - regenerate pristine gz files

=head1 SYNOPSIS

B<pristine-gz> [-vdk] gengz delta file

B<pristine-gz> [-vdk] gendelta file.gz delta

=head1 DESCRIPTION

This is a complement to the pristine-tar(1) command. Normally you don't
need to run it by hand, since pristine-tar calls it as necessary to handle
.tar.gz files.

pristine-gz gendelta takes the specified gz file, and generates a
small binary delta file that can later be used by pristine-gz gengz
to recreate the original file.

pristine-gz gengz takes the specified delta file, and compresses
the specified input file (which must be identical to the contents
of the original gz file). The resulting gz file will be identical to the
original gz file.

The approach used to regenerate the original gz file is to figure out how
it was produced -- what compression level was used, whether it was built
with GNU gzip(1) or with a library or BSD version, whether the --rsyncable
option was used, etc, and to reproduce this build environment when
regenerating the gz.

This approach will work for about 99.5% of cases. One example of a case it
cannot currently support is a gz file that has been produced by appending
together multiple gz files.

For the few where it doesn't work, a binary diff will be included in the
delta between the closest regneratable gz file and the original. In
the worst case, the diff will include the entire content of the original
gz file, resulting in a larger than usual delta. If the delta is much
larger than usual, pristine-gz will print a warning.

If the delta filename is "-", pristine-gz reads or writes it to stdio.

=head1 OPTIONS

=over 4

=item -v

=item --verbose

Verbose mode, show each command that is run.

=item -d

=item --debug

Debug mode.

=item -k

=item --keep

Don't clean up the temporary directory on exit.

=back

=head1 AUTHOR

Joey Hess <joeyh@debian.org>,
Faidon Liambotis <paravoid@debian.org>
Josh Triplett <josh@joshtriplett.org>

Licensed under the GPL, version 2.

=cut

use warnings;
use strict;
use File::Temp;
use Getopt::Long;
use File::Basename qw/basename/;
use IPC::Open2;

use constant GZIP_DEBUG		 => 1;

# magic identification
use constant GZIP_ID1		 => 0x1F;
use constant GZIP_ID2		 => 0x8B;

# compression methods, 0x00-0x07 are reserved
use constant GZIP_METHOD_DEFLATE => 0x08;

# flags
use constant {
	GZIP_FLAG_FTEXT		 => 0,
	GZIP_FLAG_FHCRC		 => 1,
	GZIP_FLAG_FEXTRA	 => 2,
	GZIP_FLAG_FNAME		 => 3,
	GZIP_FLAG_FCOMMENT	 => 4,
	# the rest are reserved
};
# compression level
use constant {
	GZIP_COMPRESSION_NORMAL	 => 0,
	GZIP_COMPRESSION_BEST	 => 2,
	GZIP_COMPRESSION_FAST	 => 4,
};
# operating systems
use constant {
	GZIP_OS_MSDOS		 => 0,
	GZIP_OS_AMIGA		 => 1,
	GZIP_OS_VMS		 => 2,
	GZIP_OS_UNIX		 => 3,
	GZIP_OS_VMCMS		 => 4,
	GZIP_OS_ATARI		 => 5,
	GZIP_OS_HPFS		 => 6,
	GZIP_OS_MACINTOSH	 => 7,
	GZIP_OS_ZSYSTEM		 => 8,
	GZIP_OS_CPM		 => 9,
	GZIP_OS_TOPS		 => 10,
	GZIP_OS_NTFS		 => 11,
	GZIP_OS_QDOS		 => 12,
	GZIP_OS_RISCOS		 => 13,
	GZIP_OS_UNKNOWN		 => 255,
};

my $verbose=0;
my $debug=0;
my $keep=0;

sub usage {
	print STDERR "Usage: pristine-gz [-vdk] gengz delta file\n";
	print STDERR "       pristine-gz [-vdk] gendelta file.gz delta\n";
}

sub debug {
	print STDERR "debug: @_\n" if $debug;
}

sub vprint {
	print STDERR "pristine-gz: @_\n" if $verbose;
}

sub doit {
	vprint(@_);
	if (system(@_) != 0) {
		die "command failed: @_\n";
	}
}

sub doit_redir {
	no warnings 'once';
	my ($in, $out, @args) = @_;
	vprint(@args, "<", $in, ">", $out);
	open INFILE, "<", $in or die("Could not open '$in' for reading: $!\n");
	open OUTFILE, ">", $out or die("Could not open '$out' for reading: $!\n");
	my $pid = open2(">&OUTFILE", "<&INFILE", @args);
	waitpid $pid, 0;
}

sub tempdir {
	return File::Temp::tempdir("pristine-gz.XXXXXXXXXX",
		TMPDIR => 1, CLEANUP => !$keep);
}

sub readgzip {
	my $filename = shift;
	my $chars;

	open(GZIP, "< $filename")
		or die("Could not open '$filename' for reading: $!\n");

	if (read(GZIP, $chars, 10) != 10) {
		die("Unable to read from input\n");
	}

	my ($id1, $id2, $method, $flags, $timestamp, $level, $os, $name)
		= (unpack("CCCb8VCC", $chars), '');

	if ($id1 != GZIP_ID1 || $id2 != GZIP_ID2 || $method != GZIP_METHOD_DEFLATE) {
		die("This is not a valid GZip archive.\n");
	}
	my @flags = split(//, $flags);
	
	if ($flags[GZIP_FLAG_FNAME]) {
		# read a null-terminated string
		$name .= $chars
			while (read(GZIP, $chars, 1) == 1 && ord($chars) != 0);
	}
	close(GZIP);

	return (\@flags, $timestamp, $level, $os, $name);
}

sub predictgzipargs {
	my ($flags, $timestamp, $level) = @_;
	my @flags = @$flags;

	my @args;
	unless ($flags[GZIP_FLAG_FNAME]) {
		push @args, '-n';
		push @args, '-M' if $timestamp;
	}

	if ($level == GZIP_COMPRESSION_BEST) {
		push @args, '-9'
	} elsif ($level == GZIP_COMPRESSION_FAST) {
		push @args, '-1'
	}

	return @args;
}

sub comparefiles {
	my ($old, $new) = (shift, shift);
	system('cmp', '-s', $old, $new);

	if ($? == -1 || $? & 127) {
		die("Failed to execute cmp: $!\n");
	}

	return $? >> 8;
}

sub reproducegz {
	my ($orig, $tempdir, $tempin) = @_;
	my $tempout="$tempdir/test.gz";
	doit_redir($orig, $tempin, "gzip", "-dc");

	# read fields from gzip headers
	my ($flags, $timestamp, $level, $os, $name) = readgzip($orig);
	debug("flags: [".join(", ", @$flags).
		"] timestamp: $timestamp level: $level os: $os name: $name");

	# try to guess the gzip arguments that are needed by the header
	# information
	my @args = predictgzipargs($flags, $timestamp, $level);
	my @extraargs = ("-F", $name, "-T", $timestamp);

	my @try;

	if ($os == GZIP_OS_UNIX) {
		# for 98% of the cases the simple heuristic above works
		# and it was produced by gnu gzip.
		push @try, ['--gnu', @args];
		push @try, ['--gnu', @args, '--rsyncable'];
	}

	if ($name =~ /\//) {
		push @args, "--original-name", $name;
		@extraargs = ("-T", $timestamp);
		$name = basename($name);
	}

	# set the Operating System flag to the one found in the original
	# archive
	push @args, ("--osflag", $os) if $os != GZIP_OS_UNIX;

	# many of the .gz out there are created using the BSD version of
	# gzip which is using the zlib library; try with our version of
	# bsd-gzip with added support for the undocumented GNU gzip options
	# -m and -M
	push @try, [@args];

	# apparently, there is an old version of bsd-gzip (or a similar tool
	# based on zlib) that creates gz using maximum compression (-9) but
	# does not indicate so in the headers. surprisingly, there are many
	# .gz out there.
	push @try, [@args, '--quirk', 'buggy-bsd'];

	# Windows' NTFS gzip implementation; quirk is really really evil
	# it should be the last test: it can result in a corrupted archive!
	if ($os == GZIP_OS_NTFS) {
		pop @args; pop @args; # ntfs quirk implies NTFS osflag
		push @try, [@args, '--quirk', 'ntfs'];
	}

	my $origsize=(stat($orig))[7];
	my ($bestvariant, $bestsize);

	foreach my $variant (@try) {
		doit_redir($tempin, $tempout, 'zgz', @$variant, @extraargs, '-c');
		if (!comparefiles($orig, $tempout)) {
			# success
			return $name, $timestamp, undef, @$variant;
		}
		else {
			# generate a binary delta and see if this is the
			# best variant so far
			my $ret=system("xdelta delta -0 --pristine $tempout $orig $tempdir/tmpdelta 2>/dev/null") >> 8;
			# xdelta exits 1 on success
			if ($ret == 1) {
				my $size=(stat("$tempdir/tmpdelta"))[7];
				if (! defined $bestsize || $size < $bestsize) {
					$bestvariant = $variant;
					$bestsize=$size;
					rename("$tempdir/tmpdelta", "$tempdir/bestdelta") || die "rename: $!";
				}
			}
		}
	}

	# Nothing worked perfectly, so use the delta that was generated for
	# the best variant
	my $percentover=100 - int (($origsize-$bestsize)/$origsize*100);
	debug("Using delta to best variant, bloating $percentover%: @$bestvariant");
	if ($percentover > 10) {
		print STDERR "warning: pristine-gz cannot reproduce build of $orig; ";
		if ($percentover >= 100) {
			print STDERR "storing entire file in delta!\n";
		}
		else {
			print STDERR "storing $percentover% size diff in delta\n";
		}
		print STDERR "(Please consider filing a bug report so the delta size can be improved.)\n";
	}
	return $name, $timestamp, "$tempdir/bestdelta", @$bestvariant;
}

sub gengz {
	my $delta=shift;
	my $file=shift;

	my $tempdir=tempdir();

	if ($delta eq "-") {
		$delta="$tempdir/in";
		open (OUT, ">", $delta) || die "$delta: $!";
		while (<STDIN>) {
			print OUT $_;
		}
		close OUT;
	}
	
	doit("tar", "xf", File::Spec->rel2abs($delta), "-C", $tempdir);
	if (! -e "$tempdir/type") {
		die "failed to gengz delta $delta\n";
	}

	open (IN, "$tempdir/version") || die "delta lacks version number ($!)";
	my $version=<IN>;
	if ($version >= 4) {
		die "delta is version $version, not supported\n";
	}
	close IN;
	if (open (IN, "$tempdir/type")) {
		my $type=<IN>;
		chomp $type;
		if ($type ne "gz") {
			die "delta is for a $type, not a gz\n";
		}
		close IN;
	}

	
	open (IN, "$tempdir/params") || die "delta lacks params file ($!)";
	my $params=<IN>;
	chomp $params;
	my @params=split(' ', $params);
	while (@params) {
		$_=shift @params;
		next if /^(--gnu|--rsyncable|-[nmM1-9])$/;
		if (/^(--original-name|--quirk|--osflag)$/) {
			shift @params;
			next;
		}
		die "paranoia check failed on params file from delta ($params)";
	}
	@params=split(' ', $params);
	close IN;
	open (IN, "$tempdir/filename") || die "delta lacks filename file ($!)";
	my $filename=<IN>;
	chomp $filename;
	$filename=~s/^.*\///; # basename isn't strong enough
	close IN;
	open (IN, "$tempdir/timestamp") || die "delta lacks timestamp file ($!)";
	my $timestamp=<IN>;
	chomp $timestamp;
	close IN;

	my @zgz=("zgz", @params, "-T", $timestamp);
	if (! grep { $_ eq "--original-name" } @params) {
		push @zgz, "-F", "$filename";
	}
	push @zgz, "-c";

	if (-e "$tempdir/delta") {
		my $tfile="$tempdir/".basename($file).".gz";
		doit_redir($file, $tfile, @zgz);
		doit("xdelta", "patch", "--pristine", "$tempdir/delta", $tfile, "$file.gz");
	}
	else {
		doit_redir("$file", "$file.gz", @zgz);
	}
}

sub gendelta {
	my $gzfile=shift;
	my $delta=shift;

	my $tempdir=tempdir();
	
	my $stdout=0;
	if ($delta eq "-") {
		$stdout=1;
		$delta="$tempdir/out";
	}

	my @files=qw(version type params filename timestamp);

	my ($filename, $timestamp, $xdelta, @params)=
		reproducegz($gzfile, $tempdir, "$tempdir/test");
	
	open(OUT, ">", "$tempdir/version") || die "$!";
	print OUT (defined $xdelta ? "3.0" : "2.0")."\n";
	close OUT;
	open(OUT, ">", "$tempdir/type") || die "$!";
	print OUT "gz\n";
	close OUT;
	open(OUT, ">", "$tempdir/params") || die "$!";
	print OUT "@params\n";
	close OUT;
	open(OUT, ">", "$tempdir/filename") || die "$!";
	print OUT basename($filename)."\n";
	close OUT;
	open(OUT, ">", "$tempdir/timestamp") || die "$!";
	print OUT "$timestamp\n";
	close OUT;
	if (defined $xdelta) {
		rename($xdelta, "$tempdir/delta") || die "rename: $!";
		push @files, "delta";
	}

	doit("tar", "czf", $delta, "-C", $tempdir, @files);

	if ($stdout) {
		doit("cat", $delta);
	}
}

Getopt::Long::Configure("bundling");
if (! GetOptions(
	"v|verbose!" => \$verbose,
	"d|debug!" => \$debug,
	"k|keep!" => \$keep,
   ) || @ARGV != 3) {
	usage();
	exit 1;
}

my $command=shift;
if ($command eq 'gengz') {
	gengz(@ARGV);
}
elsif ($command eq 'gendelta') {
	gendelta(@ARGV);
}
else {
	print STDERR "Unknown subcommand \"$command\"\n";
	usage();
	exit 1;
}