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#!/usr/bin/perl -w

=head1 NAME

dh_compress - compress files and fix symlinks in package build directories

=cut

use strict;
use Cwd;
use Debian::Debhelper::Dh_Lib;

=head1 SYNOPSIS

  dh_compress [debhelper options] [-Xitem] [-A] [file ...]

=head1 DESCRIPTION

dh_compress is a debhelper program that is responsible for compressing
the files in package build directories, and makes sure that any symlinks
that pointed to the files before they were compressed are updated to point
to the new files.

By default, dh_compress compresses files that debian policy mandates should
be compressed, namely all files in usr/share/info, usr/share/man,
usr/X11R6/man, and all files in usr/share/doc that are larger than 4k in size,
(except the copyright file, .html files and .gif files), and all changelog
files. It skips any files that appear to be already compressed (based on their
extensions).

If a debian/package.compress file exists, however, it will be ran as a shell
script, and all filenames that the shell script outputs will be compressed
instead of the default files. The shell script will be run from
inside the package build directory. Note though that using -X is a much
better idea in general; you should only use a debian/package.compress file
if you really have to.

=head1 OPTIONS

=over 4

=item B<-X>I<item>, B<--exclude=>I<item>

Exclude files that contain "item" anywhere in their filename from being
compressed. For example, -X.jpeg will exclude jpeg's from compression.
You may use this option multiple times to build up a list of things to
exclude. You can accomplish the same thing by using a debian/compress file,
but this is easier.

=item B<-A>, B<--all>

Compress all files specified by command line parameters in ALL packages
acted on.

=item I<file ...>

Add these files to the list of files to compress.

=back

=head1 CONFORMS TO

Debian policy, version 3.0

=cut

init();

foreach my $package (@{$dh{DOPACKAGES}}) {
	my $tmp=tmpdir($package);
	my $compress=pkgfile($package,"compress");

	# Run the file name gathering commands from within the directory
	# structure that will be effected.
	my $olddir=getcwd();
	verbose_print("cd $tmp");
	chdir($tmp) || error("Can't cd to $tmp: $!");

	# Figure out what files to compress.
	my @files;
	# First of all, deal with any files specified right on the command line.
	if (($package eq $dh{FIRSTPACKAGE} || $dh{PARAMS_ALL}) && @ARGV) {
		push @files, @ARGV;
	}
	if ($compress) {
		# The config file is a sh script that outputs the files to be compressed
		# (typically using find).
		push @files, split(/\n/,`sh $olddir/$compress 2>/dev/null`);
	}
	else {
		# By default, fall back to what the policy manual says to
		# compress. Note that all the excludes of odd things like _z 
		# are because gzip refuses to compress such files, assumming
		# they are zip files. I looked at the gzip source to get the
		# complete list of such extensions: ".gz", ".z", ".taz", 
		# ".tgz", "-gz", "-z", "_z"
		push @files, split(/\n/,`
			find usr/info usr/share/info usr/man usr/share/man usr/X11*/man -type f ! -name "*.gz" 2>/dev/null || true;
			find usr/doc usr/share/doc -type f \\( -size +4k -or -name "changelog*" \\) \\
				\\( -name changelog.html -or ! -iname "*.htm*" \\) \\
				! -iname "*.gif" ! -iname "*.png" ! -iname "*.jpg" ! -iname "*.jpeg" ! -iname "*.gz" \\
				! -iname "*.taz" ! -iname "*.tgz" ! -iname "*.z" \\
				! -iname "*-gz" ! -iname "*-z" ! -iname "*_z" \\
				! -name "copyright" 2>/dev/null || true
		`);
	}

	# Exclude files from compression.
	if (@files && defined($dh{EXCLUDE}) && $dh{EXCLUDE}) {
		my @new=();
		foreach (@files) {
			my $ok=1;
			foreach my $x (@{$dh{EXCLUDE}}) {
				if (/\Q$x\E/) {
					$ok='';
					last;
				}
			}
			push @new,$_ if $ok;
		}
		@files=@new;
	}
	
	# Look for files with hard links. If we are going to compress both,
	# we can preserve the hard link across the compression and save
	# space in the end.
	my @f=();
	my %hardlinks;
	my %seen;
	foreach (@files) {
		my ($dev, $inode, undef, $nlink)=stat($_);
		if ($nlink > 1) {
			if (! $seen{"$inode.$dev"}) {
				$seen{"$inode.$dev"}=$_;
				push @f, $_;
			}
			else {
				# This is a hardlink.
				$hardlinks{$_}=$seen{"$inode.$dev"};
			}
		}
		else {
			push @f, $_;
		}
	}

	if (@f) {
		# Make executables not be anymore.
		xargs(\@f,"chmod","a-x");
		
		xargs(\@f,"gzip","-9f");
	}
	
	# Now change over any files we can that used to be hard links so
	# they are again.
	foreach (keys %hardlinks) {
		# Remove old file.
	    	doit("rm","-f","$_");
		# Make new hardlink.
		doit("ln","$hardlinks{$_}.gz","$_.gz");
	}

	verbose_print("cd $olddir");
	chdir($olddir);

	# Fix up symlinks that were pointing to the uncompressed files.
	open (FIND,"find $tmp -type l |");
	while (<FIND>) {
		chomp;
		my ($directory)=m:(.*)/:;
		my $linkval=readlink($_);
		if (! -e "$directory/$linkval" && -e "$directory/$linkval.gz") {
			doit("rm","-f",$_);
			doit("ln","-sf","$linkval.gz","$_.gz");
		}
	}
}

=head1 SEE ALSO

L<debhelper(1)|debhelper>

This program is a part of debhelper.

=head1 AUTHOR

Joey Hess <joeyh@debian.org>

=cut