#!/usr/bin/perl

# choose your poison:
our $DEBUG_HTTP = 0;
#our $DEBUG_HTTP = 1;

# TODO create_mode stats are wrong

# FIXME 20151016 bkw: behold:
#  $ grep ^D libraries/p4api/*.info
#  DOWNLOAD="ftp://ftp.perforce.com/perforce/r10.1/bin.linux26x86/p4api.tgz"
#  DOWNLOAD_x86_64="ftp://ftp.perforce.com/perforce/r10.1/bin.linux26x86_64/p4api.tgz"
# notice that both URLs have the same filename (p4api.tgz)?  this is
# exactly why we have a by-md5 tree. But right now, "add libraries/p4api"
# only adds one of them. other builds with the same issue: development/p4
# and academic/ucsc-blat

# TODO based on feedback from ttkp and pink_mist on IRC:
# - IPC::Open3 instead of open my $fh, "wget ...|"? At least use
#   open my $fh, "-|", "wget", @args or such, to avoid quoting issues.
#   However, avoiding the shell means being unable to redirect
#   stderr & stdout to the same place. Hm.

# Also, stuff added with "add" sometimes ends up as separate files
# instead of hardlinks. Not sure how to replicate this.

# Ideas for future features:
# - autopurge option for update. It only needs to purge the dirs that
#   got updated, so should be quick.... except what happens if two builds
#   use the same source file, one gets updated and the other doesn't? if
#   the purge doesn't parse all the info files in the repo, it can't know
#   not to delete the by-md5 in that case. Ugh.

=pod

=head1 NAME

sbosrcarch - Create and maintain an archive of source code for SBo builds

=head1 SYNOPSIS

sbosrcarch [-c configfile] <create|update|trim|purge|check>

sbosrcarch [-c configfile] add [-f] [<category/prgnam>] [<file> ...]

sbosrcarch [-c configfile] rm <category/prgnam>

=head1 DESCRIPTION

sbosrcarch creates and maintains an archive of source code files linked
to by DOWNLOAD= and DOWNLOAD_x86_64= URLs in SlackBuilds.org .info files.

The archive contains only source code from upstream sites. No content
from slackbuilds.org itself is included.

Since a full archive would be pretty large (45GB or so), sbosrcarch
allows limiting the size of the archive (but only indirectly, by
limiting the max file size it will download). This means we won't have
a full archive of every source tarball, but even a partial mirror is
still useful.

Rough guideline for choosing filesize:

 Max filesize | Approx. total archive size | Coverage
        1.0M  |                    803.1M  |  68%
        2.0M  |                      1.4G  |  77%
        5.0M  |                      2.7G  |  85%
       10.0M  |                      4.3G  |  90%
       20.0M  |                      6.6G  |  93%
       35.0M  |                      8.9G  |  95%
       50.0M  |                     11.6G  |  96%
      100.0M  |                     16.6G  |  98%
   unlimited  |                     43.0G  | 100%

Note: these numbers will tend to increase over time, as the SBo repository
grows. To be safe, add 25% or so to the total sizes above.

"Coverage" is the percentage of all the URLs in all the .info files
that will be kept in this archive. Notice that about 60% of the storage
space is eaten up by 2% of the files, in the unlimited case. These
large files are mostly games, if that influences your decision any.

=head1 OPTIONS

=over

=item B<-c> I<config-file>

Read specified config file instead of searching in the default locations
for it. See B<CONFIG FILE> section below for default. This option must
appear first on the command line, if used.

=item B<create>

Create archive. Used for initial archive creation, and for downloading
new files to an existing archive when the size limit ($maxfilemegs,
see B<CONFIG FILE>) is increased.

Should be run interactively, from a login shell. Takes a long time to
run and uses a lot of bandwidth. Log output goes to stdout, and is pretty
verbose (redirecting to a file is recommended).

If the archive already exists, existing files will be kept instead of
being re-downloaded (provided of course their md5sums are correct).

=item B<update>

Update archive, by checking the SBo git log and parsing any .info files that
have changed since the last create or update.

Should be run daily or weekly as a cron job.

If there are are few or no changed download URLs, update should run
quickly and not eat many resources. For each new URL, the file is
downloaded and added to the archive, but the old file is *not* deleted
(use 'sbosrcarch purge' to do that).

=item B<purge> I<[-r|--rebuild]>|I<[-f|--fake]>

Purge files from the archive that are no longer referenced by any
.info file. Should be run monthly or quarterly as a cron job. This is
more resource-intensive than an update, as it must read and parse every
.info file in the SBo repository.

If -r or --rebuild is given, the entire by-md5 tree is deleted and
recreated. This shouldn't be needed unless $symlinks (see B<CONFIG FILE>)
is changed, or something catastrophic happens to the by-md5 tree. Don't
do this automatically from cron: while it's running, your archive users
will see an incomplete by-md5 tree.

If -f or --fake is given, a list of files to be purged will be produced,
but nothing will actually be deleted. This option B<cannot> be combined
with -r/--rebuild, and no warning will be given if it's tried: whichever
option occurs first will take effect, and the other one will be ignored!

=item B<trim>

Gets rid of files that are in the archive, but are larger than the size
limit. Should be run manually after lowering $maxfilemegs; there's no
reason to run it any other time.

=item B<check> I<[-v]>

Checks the integrity and coverage of the archive. Reports at least these conditions:

 - dangling symlinks
 - invalid md5sums
 - files present in only one of by-name or by-md5 but not the other
 - extraneous files in the tree
 - generates a status report, giving the total size and coverage.

Will not modify the archive in any way, but might recommend fixes.

With -v, lists all SlackBuilds not covered by the archive.

<check> is quite I/O and CPU intensive, as it must read and md5sum every
file in the archive.

Blacklisted builds are not included in the status report, so the "Total
SlackBuilds" number might not match the number of builds in the git repo.
This is a feature (otherwise it would be impossible to see 100% coverage).

=item B<status> I<[-v]>

Checks the coverage of the archive. Like B<check>, but doesn't md5sum the
files (it just assumes they're correct). Use this as a quick way to get
a status report.

=item B<add> I<[-f] <category/prgnam> [<file> ...]>

Manually add (possibly already downloaded) files to the archive.

Use -f to skip the size limit checking, so your archive can include a
few large files (perhaps because they're for builds you maintain).

Files added this way will still be deleted by 'sbosrcarch trim', if
they're larger than the limit.

This is intended to let the mirror operator keep a few large files (over
the maxfilemegs limit), or save bandwidth by using already-downloaded
copies (e.g. of stuff that was built recently).

If files are given after the category/prgnam argument, they will be
used instead of downloading the URLs in the .info file (provided their
md5sums match the .info file). Size limits are not checked for files
added this way.

=item B<add> I<<file> [...]>

Manually add local file(s) to the archive. As above, but the
category/prgnam is discovered by parsing all the .info files and
matching md5sums. This is a good bit slower, but it can handle files
for many different category/prgnam at once. It's especially useful if
you already have an archive of SBo sources that you want to convert to
sbosrcarch format.

The -f option is not supported (or needed) with this form of the add
command.

=item B<rm> I<<category/prgnam>>

Manually remove files from the archive. All the files referenced by the
.info file for <category>/<prgnam> will be removed.

...but the next update will re-add anything you remove, if it's less than
the size limit. Mostly this is useful for manually-added files that are
over the limit.

=back

=head1 CONFIG FILE

By default, B<sbosrcarch.conf> (or B<.sbosrcarch.conf>) is the config
file for sbosrcarch. It's searched for under both names in the current
directory, the user's home directory, /etc/sbosrcarch, and /etc (in
order).

To specify a different config file, use B<-c> -I<config-file>.

Config file options are documented in comments in the sample config file.

=head1 FILES

The archive created by sbosrcarch consists of two top-level directories
called B<by-name> and B<by-md5>. All files are present in both hierarchies
(but the by-md5 tree is hard or symbolic links, to save space).

B<by-name> is organized by the familiar category and PRGNAM, like SBo
itself. Example:

  by-name/network/ifstatus/ifstatus-v1.1.0.tar.gz

This makes it easy for humans to browse the archive and find the source
file they're looking for.

B<by-md5> contains the same files, but organized in a hierarchy based on
the md5sum of the file, for automated systems to easily find the exact
file needed. The same file as the example above would be found at:

by-md5/f/4/f4d413f880754fd6677290160f8bc5d7/ifstatus-v1.1.0.tar.gz

Notice there are two layers of subdirectory, named after the first two
hex digits in the md5sum. Also, notice that the actual SlackBuilds and
.info files are not present in the archive.

There is one other directory of files used/maintained by sbosrcarch:
a git clone of SBo's master git branch. This is cloned and updated
automatically as needed, and shouldn't need to be messed with. If you
need a git clone of SBo for some other purpose, create a separate one
to avoid confusing sbosrcarch with your changes and pulls.

=head1 SERVER CONFIGURATION

If you're planning to host a public archive, you'll need to make the
$archivedir available via whatever protocols you support (HTTP, FTP,
rsync, etc). This is the directory containing B<by-name> and B<by-md5>.
The git clone directory doesn't need to be served to the public.

TODO: example Apache, proftpd, etc configs for serving up the archive.

=head1 CLIENT-SIDE EXAMPLE

The following shell script is intended to be run from an extracted
SlackBuild directory. It attempts to download the source files from
the by-md5/ tree of the archive.


	#!/bin/sh
	
	# sbosrcarch client example script. tested with bash, ash, zsh, ksh.
	
	# path to the root of your archive (contains the by-name and
	# by-md5 directories):
	ARCHIVE=http://yoursite.com/sbosrc
	
	. $( pwd )/*.info || ( echo "no .info file in current dir" 1>&2 && exit 1 )
	
	if [ "$ARCH" = "x86_64" -a "$MD5SUM_x86_64" != "" ]; then
		MD5SUM="$MD5SUM_x86_64"
		DOWNLOAD="$DOWNLOAD_x86_64"
	fi
	
	set $MD5SUM
	
	for url in $DOWNLOAD; do
		file="$( echo "$url" | sed 's,.*/,,' )"
		md5=$1
		shift
	
		echo "Downloading $file ($md5)"
	
		a=$( echo $md5 | cut -b1 )
		b=$( echo $md5 | cut -b2 )
	
		wget -O "$file" "$ARCHIVE/by-md5/$a/$b/$md5/$file"
	
		if [ -e "$file" -a "$( md5sum "$file" | cut -d' ' -f1 )" = "$md5" ]; then
			echo "downloaded, md5sum matches"
		else
			echo "download failed"
			fail=1
		fi
	done
	
	if [ "$fail" != "1" ]; then
		echo "All files found and downloaded successfully"
		exit 0
	else
		exit 1
	fi

### end of script

The perldoc format requires literal code blocks to be prefixed with
a tab on each line, so copy/pasting the above script will result in a
mess. Instead, extract it with:

	sed -n '/^\t#!\/bin\/sh/,/^### end/p' sbosrcarch | cut -f2- > script.sh

=head1 NOTES

sbosrcarch is written in perl, and is intended to work on at least
Slackware 13.0 through 14.1, using only perl modules that ship with the OS
(so no CPAN dependencies), plus an external curl or wget executable for
downloading files. If you want to run it on some other OS, it might need
some extra packages installed and/or some slight porting work. If you want
to keep a SBo source archive on your non-Slackware server, it might be
easier to just rsync someone else's (that they build using this script).

Note that there's no need to run sbosrcarch as root. In fact, it's
recommended not to. Good choices for a user to run it as:
 - your everyday user you log in as
 - apache
 - nobody

=head1 BUGS/LIMITATIONS

Plenty of these, see FIXME TODO XXX comments in the code. Here are some
that I'm not planning to address any time soon:

No threading. Not likely to change. It would be possible to spawn wget
or curl processes in the background, but I'm not going to complicate it
that way. It would mainly be useful for create mode, and hopefully each
archive site only needs to do that once.

Anything that checks referer header or otherwise tries to stop automated
downloads, will stop us. This isn't really a bug (sbopkg can't handle
them either). Usually the README will say "you must download the file
with a browser" or such. You can still download the file manually
and use "sbosrcarch add category/prgnam filename.tar.gz" to add it
to the archive...  but please pay attention to licensing! Some files
(e.g. Oracle's Java) don't allow redistribution, so please don't include
them in your archive.

For URLs that won't give us a Content-Length header, we can't determine
the file size. If $maxfilemegs is zero (unlimited), this doesn't matter:
everything gets downloaded. If there's a size limit, and we can't
determine the size, we download them 'incrementally', stopping the
download if the file size limit is set. Unfortunately this can waste a
lot of bandwidth, if the limit is high.

=head1 AUTHOR

B. Watson <yalhcru@gmail.com>

=cut

# use only modules that ship with Slackware, which pretty much
# means only modules that ship with core perl.
# use the 'legacy' 2.0 API for File::Path, since we want to support
# the older perl in Slackware 13.0.
use warnings;
use strict; # I hate strict, but I'll use it anyway...
use File::Temp qw/tempfile tempdir/;
use File::Find;
use Digest::MD5;
use Net::FTP;
use POSIX 'getcwd';
use File::Path qw/mkpath rmtree/;
use File::Copy qw/copy move/;

# 20151016 bkw: migrating to curl
our $use_curl = 1;

our($sbogiturl, $sbogitdir, $archivedir, $maxfilemegs, $wget,
    $wgetargs, $symlinks, $wgetrc_contents, $wgetrc, %user_agent_overrides,
    @trim_empty_dirs, $skipcount, $urlcount, $archivecount,
    $attemptcount, $failcount, $dlcount, $nowarchived, $coverage,
    $purgebytes, $purgefiles, $trimcount, $trimbytes,
    %keep_filenames, %keep_md5sums, $fake_purge);
our ($curl, $curlopts);
our (%whitehash, %blackhash, $use_bwlist);
our @whitelist = ();
our @blacklist = ();
our $quickcheck; # used by check_mode() and its *wanted helpers

our %infofilecount;
our %parsedinfo;
our $symlinkcount = 0;
our $hardlinkcount = 0;
our $filecount = 0;
our $filebytes = 0;
our $actualfilecount = 0;
our $totalfiles = 0;

sub read_config {
	my $conf_used;

	my @configdirs = (
			".",
			$ENV{HOME},
			"/etc/sbosrcarch",
			"/etc",
	);

	if(@ARGV && $ARGV[0] =~ /^-c(.*)$/) {
		shift @ARGV;
		if($1) {
			$conf_used = $1;
		} elsif(@ARGV && $ARGV[0]) {
			$conf_used = shift @ARGV;
		} else {
			die "-c option requires argument\n";
		}
		do $conf_used;
		die "$conf_used: $!\n" if $!;
		die "reading config file $conf_used: $@" if $@;
	} else {
		for my $dir (@configdirs) {
			for my $file (qw/.sbosrcarch.conf sbosrcarch.conf/) {
				$_ = "$dir/$file";
				next unless -e $_;
				do $_;
				next if $!;
				die "reading config file $_: $@" if $@;
				$conf_used = $_;
				last;
			}
		}
	}

	if($conf_used) {
		print "read config file: $conf_used\n";
	} else {
		die "can't find .sbosrcarch.conf or sbosrcarch.conf in any of the\n" .
			"following directories (and no -c option), giving up:\n" .
			join ("\n", @configdirs) . "\n" .
			"\nTry 'sbosrcarch --help' or 'perldoc sbosrcarch' for help.\n";
	}

# required stuff in the conf file:
	die "config file missing \$sbogiturl\n" unless defined $sbogiturl;
	die "config file missing \$sbogitdir\n" unless defined $sbogitdir;
	die "config file missing \$archivedir\n" unless defined $archivedir;

# not required, but warn if it's missing:
	if((not defined $maxfilemegs) || ($maxfilemegs < 0)) {
		print "config file missing/invalid \$maxfilemegs, defaulting to 10\n";
		$maxfilemegs = 10;
	}

# quietly use defaults if missing:
	$wget = "wget" unless defined $wget;
	$curl = "curl" unless defined $curl;
	$use_curl = 1 unless defined $use_curl;
	$wgetargs = "" unless defined $wgetargs;
	$symlinks = "" unless defined $symlinks;

	if($use_curl && !defined($curlopts)) {
		die "\$\$use_curl is true, but curlopts is missing from config file\n";
	}

	if(not defined $wgetrc_contents) {
		$wgetrc_contents = <<EOF;
robots = off
user_agent = Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)
check_certificate = off
content_disposition = off
EOF
	}

	if(not %user_agent_overrides) {
		%user_agent_overrides = (
			qr/(?:sourceforge|sf)\.net/ => 'wget',
		);
	}

# white and black lists are configured as arrays, but internally
# stored as hashtables for quicker lookups.
	$whitehash{$_}++ for @whitelist;
	for(@blacklist) {
		if($whitehash{$_}) {
			warn "$_ in both \@blacklist and \@whitelist, ignoring\n";
			delete $whitehash{$_};
			next;
		}

		$blackhash{$_}++;
	}
}

# in: ($category, $prgnam) *or* "$category/$prgnam" *or" "./$cat/$prg/$prg.info"
# out: ($category, "$category/$prgnam")
sub catbuild {
	my($cat, $prgnam);
	if(defined($_[1])) {
		($cat, $prgnam) = @_;
	} else {
		$_[0] =~ s,^\./,,;
		$_[0] =~ s,/[^/]*\.info$,,;
		($cat, $prgnam) = split /\//, $_[0];
	}
	return ($cat, $cat . '/' . $prgnam);
}

sub whitelisted {
	return 0 unless $use_bwlist;
	my ($cat, $build) = catbuild(@_);
	return 1 if $whitehash{$build};
	return 1 if $whitehash{$cat} && !$blackhash{$build};
	return 0;
}

sub blacklisted {
	return 0 unless $use_bwlist;
	my ($cat, $build) = catbuild(@_);
	return 1 if $blackhash{$build};
	return 1 if $blackhash{$cat} && !$whitehash{$build};
	return 0;
}

# url_to_filename, gets the filename part of a URL (after the last slash)
# and un-escapes any %XX sequences.
# Note: we *don't* do plus-to-space conversion here, as that's only
# for CGI params, not URLs in general. There are quite a few files
# called e.g. "c++-utils.tar.gz" that would get broken by it.
sub url_to_filename {
	my $u = shift;
	$u =~ s,.*/,,;
	$u =~ s,%([0-9A-F]{2}),chr(hex($1)),ge;
	return $u;
}

# parse a single .info file, return a hashref where keys = URL(s)
# and values are their md5sums.
sub parse_info {
	local $/ = "";
	my $file = shift;

	open my $fh, "<", $file or do {
		warn "$file: $!";
		return undef;
	};

	my $got = <$fh>;

	$got =~ s/\\\s*\n//gs; # join \ continuation lines
	$got =~ s/[ \t]+/ /g;  # condense whitespace

	my @urllines = ($got =~ /DOWNLOAD(?:_x86_64)?="\s*((?:htt|ft)[^"]+)"/g);
	my @md5lines = ($got =~ /MD5SUM(?:_x86_64)?="\s*([0-9a-f][^"]+)"/g);
	my @urls = split " ", join " ", @urllines;
	my @md5s = split " ", join " ", @md5lines;

	my %ret;
	for(@urls) {
		my $m = shift @md5s;
		#next if /^un(test|support)ed$/i; # no longer need
		print "bad URL in $file (backtick)\n", next if /`/; # backticks should never occur!
		$ret{$_} = $m;
	}

	close $fh;
	return \%ret;
}

# the download_* subs return:
# 0 - file too big (so skip it)
# positive integer - file size
# undef - download error (404, failed DNS, etc).
# FIXME: the above isn't really true, and the calling code doesn't
# check the return values as it should.

# 20151016 bkw: migrating to curl
sub curl_download_http {
	my $url = shift;
	my $filename = url_to_filename($url);
	our($curl, $curlopts);

	my $tmpdir = $ENV{TMPDIR} || $ENV{TMP} || "/tmp";
	my ($fh, $outfile) = tempfile("curl.out.XXXXXXXX", DIR => $tmpdir, UNLINK => 1);
	close $fh;

	# first, dump the headers only. --head -X GET makes curl use a GET
	# request, but act like HEAD (exit after headers are read).
	# for github URLs, we retry if we got no Content-Length. for whatever
	# reason, if the length is missing in a request, it'll generally be
	# there the next time around... or the time after that (3 tries here).
	# bitbucket seems to do the same thing.

	my $httpstatus;
	my $httpstatusline;
	my $size;

	if($maxfilemegs) { # only check size if there's a size limit!
		# TODO: do this bit in download_http, not here (so it happens for wget too)
		# (either that, or rip out the wget code)
		my $tries = ($url =~ /github\.com|bitbucket\.org/) ? 3 : 1;

		for(1..$tries) {
			my $cmd =
				  "$curl $curlopts "  .
					user_agent($url) .
					" --head -X GET " .
					wget_quote_url($url) .
					" 2>$outfile |";
			warn "* $cmd\n" if $DEBUG_HTTP;
			open my $fh, $cmd or die $!;

			local $/ = "\r\n";
			while(<$fh>) {
				chomp;
				warn "* $_\n" if $DEBUG_HTTP;

				$httpstatus = $1, $httpstatusline = $_ if /^HTTP\/\S+\s+(\d+)/;

				# grr. forja.rediris.es returns Content-length (lowercase L)
				$size = $1 if /^Content-Length:\s+(\d+)/i;
			}
			close $fh;
			last if $size;
			sleep 2;
		}

		if(not defined $httpstatus) {
			open my $fh, "<$outfile";
			while(<$fh>) {
				print "! $_";
			}
			close $fh;
			return undef; # connection refused, DNS lookup failed, etc
		}

		if($httpstatus ne "200") {
			print "! $httpstatusline\n";
			return undef;
		}

		if(not defined($size)) {
#			print "? couldn't determine file size, skipping\n";
#			return undef;
			return curl_incremental_download($url);
		} elsif(toobig($size)) {
			printf "+ file too large: %0.2fMB\n", $size / (1024 * 1024);
			$skipcount++;
			return undef;
		}
	}

	# now download the file: either the size is known to be under the
	# limit, or else there was no limit.
	$attemptcount++;
	my $cmd = "$curl $curlopts "  .
			user_agent($url) .
			" -o'$filename' --retry 2 " .
			wget_quote_url($url) .
			" -D $outfile.hdr " .
			" > $outfile 2>&1";
	warn "* $cmd\n" if $DEBUG_HTTP;
	my $retval = system($cmd);

	print "curl retval==$retval\n" if $DEBUG_HTTP;

	if($retval != 0) {
		open my $fh, "<$outfile";
		while(<$fh>) {
			print " ! $_";
		}
		close $fh;
	}

	open $fh, "<$outfile.hdr";
	while(<$fh>) {
		$_ =~ s,[\r\n],,g;
		next unless /^HTTP\/\S+\s+(\d+)/;
		$httpstatusline = $_, $httpstatus = $1;
	}
	close $fh;

	unlink($outfile);
	unlink("$outfile.hdr");

	if(defined $httpstatus && ($httpstatus ne "200")) {
		print "! $httpstatusline\n";
		unlink $filename;
		return undef;
	}

	if(-f $filename) {
		$size = -s _;
		warn "* $filename exists, $size bytes\n" if $DEBUG_HTTP;
	}

	return $size;
}

# The calling code has already checked the HTTP status, and it's
# known to be 200 OK... but the server refuses to give us a Content-Length
# header. This happens for less than 1% of the URLs. What we'll do
# is start the download, writing to the output file... and either it
# finishes before the limit, or we stop & rm the file when we hit
# the limit.
# This sub doesn't report curl errors.
sub curl_incremental_download {
	my $url = shift;
	my $filename = url_to_filename($url);
	my $maxbytes = $maxfilemegs * 1024 * 1024;
	my $buffer;
	my $bufsiz = 16 * 1024;
	my $bytecount = 0;
	my  $readbytes;

	print "? couldn't determine file size, trying incremental download\n";

	open my $fh, "$curl $curlopts --no-show-error " . wget_quote_url($url) . " |"
		or return undef;
	binmode $fh;

	open my $out, ">$filename" or warn "$!\n", return undef;
	binmode $out;

	while($readbytes = read $fh, $buffer, $bufsiz) {
		syswrite($out, $buffer, $readbytes);
		$bytecount += $readbytes;
		if($bytecount > $maxbytes) {
			close $fh;
			close $out;
			unlink($filename);
			$skipcount++;
			printf "+ file too large\n";
			return 0;
		}
	}

	close $fh;
	close $out;
	return $bytecount;
}

sub download_http {
	my $url = shift;
	my $size = wget($url, 1); # HEAD request first

	# $size will be 0 for 'too big' or undef if the HEAD failed.

	if($size) {
		$size = wget($url, 0);
	}
	return $size;
}

sub download_file {
	my $url = shift;
	my $dlresult;

	if($url =~ /^ftp:/) {
		$dlresult = download_ftp($url);
	} elsif($use_curl) {
		$dlresult = curl_download_http($url);
	} else {
		$dlresult = download_http($url);
	}

	return $dlresult;
}

# see %user_agent_overrides
# this is called by both wget() and curl_download_http(), fortunately
# wget and curl happen to use the same argument for user-agent.
sub user_agent {
	my $url = shift;

	my $ua = "";
	$url =~ m,^\w+://([^/]*)/,;
	my $site = $1;
	for (keys %user_agent_overrides) {
		$site =~ /$_/ && do {
			$ua = $user_agent_overrides{$_};
		};
	}
	$ua = "--user-agent '$ua'" if $ua;
	return $ua;
}

# return true if limit set and file size > limit.
# return false if no limit set, or file size <= limit.
sub toobig {
	return 0 if $maxfilemegs <= 0; # no limit
	return $_[0] > ($maxfilemegs * 1024 * 1024);
}

# wget_fake_head: What is a fake HEAD request?

# Various cloud-ey web servers don't support HEAD requests:

# github.com and bitbucket.org download links redirect to amazonaws.com,
# which returns 403 Forbidden for any HEAD request.

# googlecode.com always returns 404 Not Found for a HEAD request.

# some other servers don't return a Content-Length header for a HEAD
# request, but they do for a GET.

# We really want to know the file size, so we can decide whether or
# not to download it. If a HEAD request fails, we'll do a GET request
# instead, but stop the transfer as soon as we get the Content-Length
# header from wget.

# Due to buffering, wget still downloads the first 16K or so of the file,
# which gets discarded when we close its filehandle. We could do better
# than this by implementing the HTTP protocol in terms of IO::Socket::INET
# or such, but I'm not writing & debugging the mess that would turn into.
# Plus, core perl (and Slackware's perl) lacks SSL support.

# This gets called for any URL that doesn't return a Content-Length header
# in its HEAD request (for whatever reason, including because of a 404
# not found). Of course, a GET might not return a length header either,
# in which case the file won't be downloaded.

# It might be nice if wget supported a --fake-head option itself. Maybe I'll
# code it up & send a patch to the wget maintainers?

# I've just discovered a better way to do this:
# curl --head -L -sS -X GET $url
# Stops downloading and exits after the headers are received.
# Not as familiar with curl as I am with wget, have to see about
# options... and if this works as well as I expect, there's never going
# to be a need to do a real HEAD request!

# update: the above has been implemented, see curl_download_http()

sub wget_fake_head {
	my $url = shift;
	our $wget_config_arg;
	my $cmd = "$wget $wget_config_arg " .
		"--tries 1 --quiet -O- --save-headers " .
		user_agent($url) . " " .
		" $wgetargs " .
		wget_quote_url($url);

	#print "real HEAD failed, trying fake HEAD request: $cmd\n";

	# TODO: open3?
	open my $fh, "$cmd|" or return undef;
	my $size;
	while(<$fh>) {
		s/\r//;
		chomp;
		last if /^$/;
		$size = $1 if /^Content-Length:\s+(\d+)/i;
	}
	close $fh;

	if($size && toobig($size)) {
		printf "+ file too large: %0.2fMB\n", $size / (1024 * 1024);
		$skipcount++;
		$size = 0;
	} elsif(not defined $size) {
		print "? can't determine file size, skipping\n";
	}

	return $size;
}

# return url, in single quotes.
sub wget_quote_url {
	my $url = shift;

# At one time I thought this was necessary to get dropbox URLs to
# work. Turns out user_agent_overrides works better.
#	if($url =~ m,https?://(?:\w+\.)dropbox\.com/,) {
#		$url =~ s,\?dl=\d$,,;
#		$url .= "?dl=1";
#	}

	return "'$url'";
}

# wget() does a HEAD (or fake head, if HEAD fails), or GET (download),
# using an external wget process. Return value is the file size in bytes,
# or 0 for "too big", or undef for any error.
sub wget {
	my $url = shift;
	our $wget_config_arg;

	if($url =~ /'/) {
		print "! refusing to deal with URL \"$url\" due to embedded single-quote.\n" .
			"! please contact the maintainer of the SlackBuild to have this fixed.\n";
		return undef;
	}

	my $head = shift; # boolean, 0 = download (GET), 1 = HEAD request only
	$attemptcount++ if !$head;

	my $size;
	my $fh;

	my $tmpdir = $ENV{TMPDIR} || $ENV{TMP} || "/tmp";

	if(not defined $wgetrc) {
		($fh, $wgetrc) = tempfile("wgetrc.XXXXXXXX", DIR => $tmpdir, UNLINK => 1);
		print $fh $wgetrc_contents;
		close $fh;
	}

	if(not defined $wget_config_arg) {
		$wget_config_arg = "";
		open my $fh, "$wget --help|" or die "can't run wget: $!\n";
		while(<$fh>) {
			$wget_config_arg = "--config=$wgetrc" if /--config/;
		}
		close $fh;
		if(not $wget_config_arg) {
			print "| wget version is too old to support --config option.\n";
			print "| continuing without it...\n";
		}
	}

	my $outfile;
	($fh, $outfile) = tempfile("wget.out.XXXXXXXX", DIR => $tmpdir, UNLINK => 1);
	close $fh;

	# TODO: open3?
	# the -O is there to force the filename, in case of a redirect. newer
	# versions of wget don't actually need this, but it doesn't hurt.
	my $cmd = "$wget $wget_config_arg " .
		user_agent($url) . " " .
		($head ? "--spider --tries 1" : "-O '" . url_to_filename($url) . "'") .
		" $wgetargs " .
		wget_quote_url($url) . " " .
		">$outfile 2>&1";

		#" --referer='$url' " . # don't use, it breaks sourceforge

	my $retval = system($cmd);
	print "$cmd\n" if $retval != 0;

	open $fh, "<", "$outfile";
	while(<$fh>) {
		print " ! $_" if $retval != 0;

		/^Length:\s*(\d+).*\[(.*?)\]/ && do {
			$size = $1; # TODO: $content_type = $2, check for text/html or such
			if(toobig($size)) {
				printf "+ file too large: %0.2fMB\n", $size / (1024 * 1024);
				$skipcount++;
				$size = 0;
			}
		};
	}
	close $fh;
	unlink $outfile;

	# Grr. Some sites refuse HEAD requests, and some allow them but
	# don't return a Content-Length header. So we must resort to more
	# drastic measures.
	# FIXME: don't bother doing this if we got a DNS error from the HEAD.
	if($head && not(defined($size))) {
		return wget_fake_head($url);
	}

	return $size; # which might be undef!
}

# we could use wget for FTP links too, but doing it this way
# lets us check the filesize and do the download with only one
# FTP session.
sub download_ftp {
	my ($server, $dir, $filename) = ($_[0] =~ m,
		^ftp://   # proto
		([^/]+)   # server (no slashes)
		(/.*?)?   # optional path (always at least the initial slash)
		([^/]+)$  # filename (everything after last slash)
		,x);

	print "* download_ftp $_[0] " .
		"(server $server, dir $dir, filename $filename\n" if $DEBUG_HTTP;
	my $size = undef;
	eval {
		my $ftp = Net::FTP->new($server, Debug => 0)
			or die "Can't connect to $server: $@";
		print "* connected\n" if $DEBUG_HTTP;
		$ftp->login("anonymous",'-anonymous@')
			or die "Can't log in to $server: ", $ftp->message;
		print "* logged in as anonymous\n" if $DEBUG_HTTP;
		$ftp->cwd($dir)
			or die "Can't chdir($dir) on $server: ", $ftp->message;
		print "* chdir $dir OK\n" if $DEBUG_HTTP;
		$ftp->binary;
		$size = $ftp->size($filename)
			or die "Can't get $filename size from $server: ", $ftp->message;
		print "* $filename is $size bytes\n" if $DEBUG_HTTP;

		if(toobig($size)) {
			printf "+ file too large: %0.2fMB\n", $size / (1024 * 1024);
			$skipcount++;
			$size = 0;
		} else {
			$attemptcount++;
			$ftp->get($filename)
				or die "Can't download $filename from server: ",
					($ftp->message ? $ftp->message : "(no message, timed out?)"), "\n";
			print "* get finished\n" if $DEBUG_HTTP;
		}

		$ftp->quit;
		print "* \$ftp->quit\n" if $DEBUG_HTTP;
	};

	if($@) {
		print "! $@";
		undef $size;
	}

	return $size;
}

sub git_clone {
	system('git', 'clone', $sbogiturl, $sbogitdir);
}

sub git_pull {
	return !system('git', 'pull');
}

sub md5_dir {
	my $md5 = shift;
	return "$archivedir/by-md5/" .
		substr($md5, 0, 1) .
		"/" .
		substr($md5, 1, 1) .
		"/" .
		$md5 .
		"/";
}

sub name_dir {
	my ($cat, $prg) = @_;
	return "$archivedir/by-name/$cat/$prg/";
}

sub md5sum_file {
	my $filename = shift;
	open my $fh, "<", $filename or do {
		print "can't get md5sum of $filename: $!\n";
		return undef;
	};
	binmode($fh);
	my $ret = Digest::MD5->new->addfile($fh)->hexdigest;
	close $fh;
	return $ret;
}

sub already_exists {
	my ($filename, $category, $prgnam, $md5) = @_;

	my $n = name_dir($category, $prgnam) . "/" . $filename;
	my $m = md5_dir($md5) . "/" . $filename;

	return
		-e $n &&
		-e $m &&
		($md5 eq md5sum_file($n)) &&
		($md5 eq md5sum_file($n));
}

sub store_file {
	my ($filename, $category, $prgnam, $md5) = @_;

	#warn "store_file($filename, $category, $prgnam, $md5);\n";

	my $md5dir = md5_dir($md5);
	my $namedir = name_dir($category, $prgnam);

	mkpath($md5dir);
	mkpath($namedir);
	unlink($namedir . "/" . $filename); # rm -f old copy, if any
	move($filename, $namedir . "/" . $filename);
	if($symlinks) {
		symlink("../../../../by-name/" . $category . "/" . $prgnam . "/" . $filename,
				$md5dir . "/" . $filename);
	} else {
		link($namedir . "/" . $filename, $md5dir . "/" . $filename);
	}
}

# handle_info_file() is used as the 'wanted' sub for File::Find, but
# it's also called from add and update modes, so it doesn't use any of
# the File::Find stuff. Call while cd'ed to $sbogitdir, with $_ set to
# the relative path to the .info file.
sub handle_info_file {
	return unless /\.info$/;

	s,^\./,,; # strip leading ./, if present
	my ($category, $prgnam) = split /\//, $_;
	print "=== $category/$prgnam\n";

	if(blacklisted($category, $prgnam)) {
		print "- blacklisted, skipping\n";
		return;
	}

	my $dls = parse_info($_);
	for(keys %$dls) {
		$urlcount++;
		my $url = $_;
		my $md5 = $dls->{$_};
		my $filename = url_to_filename($url);
		print ": $url\n";

		if(already_exists($filename, $category, $prgnam, $md5)) {
			print "  already in archive, OK\n";
			$archivecount++;
		} else {
			{
				local $maxfilemegs = 0 if whitelisted($category, $prgnam);
				download_file($url); # TODO: check result!
			}
			if(! -f $filename || -z $filename) {
				unlink($filename);
				$failcount++;
				print "- not downloaded\n";
				next;
			}

			if(md5sum_file($filename) ne $md5) {
				$failcount++;
				print "! md5sum failed\n";
				unlink($filename);
				next;
			}

			print "  downloaded, OK\n";
			$dlcount++;
			store_file($filename, $category, $prgnam, $md5);
		}
	}
}

sub init_git {
	chdir($sbogitdir) && -d ".git" ||
		die "SBo git dir $sbogitdir not a git checkout, " .
			"do you need to run 'sbosrcarch create?'\n";
}

sub create_mode {
	chdir($sbogitdir) or git_clone;
	chdir($sbogitdir) or die "can't find or create SBo git dir $sbogitdir\n";
	git_clone() unless -d ".git";
	git_pull() or die "git pull failed, check $sbogitdir\n";

	$use_bwlist = 1;
	$skipcount = $attemptcount = $urlcount =
	$archivecount = $dlcount = $failcount = $nowarchived = 0;

	find({wanted => \&handle_info_file, no_chdir => 1}, ".");

	$nowarchived = $dlcount + $archivecount;
	$coverage = sprintf("%.1d", ($nowarchived * 100 / $urlcount));
	print <<EOF;

---
Total URLs: $urlcount
Already archived: $archivecount
Skipped downloads due to size limit: $skipcount
Attempted downloads: $attemptcount
Successful downloads: $dlcount
Failed downloads: $failcount
Now archived: $nowarchived
Coverage: $coverage%
EOF
	exit 0;
}

sub update_mode {
	my $oldcommit;

	init_git();

	$use_bwlist = 1;

	open my $fh, "git log|" or die "$!";
	my $logline = <$fh>;
	(undef, $oldcommit) = split /\s+/, $logline;
	print "git repo was at commit $oldcommit\n";
	close $fh;

	git_pull();

	open $fh, "git diff --numstat $oldcommit|" or die "$!";
	while(<$fh>) {
		(undef, undef, $_) = split /\s+/;
		next unless /\.info$/;
		print "$_ was removed from repo\n", next unless -f;
		handle_info_file();
	}
	exit 0;
}

# purge_mode() does 3 or 4 passes:

# 1. get all the filenames from all the info files, build hashes of filenames
#    and md5sums that we want to keep.
# 2. walk the archive tree with File::Find and rm any file that's in a
#    category/name dir, but not mentioned in the filename hash

# If --rebuild not given:
# 3. walk the archive tree with File::Find and rm any file that's in a
#    by-md5 dir, but whose md5sum is not mentioned in the md5sum hash.
# 4. do a trim_post() pass to delete any empty dirs and/or dangling symlinks

# If --rebuild is given:
# 3. delete the entire by-md5 tree and recreate it. should not be done on a
#    regular basis, only if something drastic happened to the by-md5 tree.

# If --fake is given, the 4 passes are all done, but nothing is deleted. Not
# possible to combine --rebuild and --fake!

sub purge_mode {
	my $rebuild = 0;

	shift @ARGV;
	if($ARGV[0]) {
		if($ARGV[0] =~ /^--?r(?:ebuild)?/) {
			$rebuild = 1;
		} elsif($ARGV[0] =~ /^--?f(?:ake)?/) {
			$fake_purge = 1;
		} else {
			die "Unknown option: $ARGV[0]\n";
		}
	}

	init_git();

	$purgebytes = $purgefiles = 0;

	# pass 1; build list of all source files, by parsing all .info files
	%keep_filenames = %keep_md5sums = (); # populated by the find():
	find({wanted => \&purge_pass_1_wanted, no_chdir => 1}, ".");

#	for(keys %keep_filenames) {
#		warn "keep $_\n";
#	}

	# pass 2: find all source files, delete any that aren't mentioned in any
	# .info files (using list from above)
	chdir($archivedir) or die "$archivedir: $!\n";
	find({wanted => \&purge_pass_2_wanted, no_chdir => 1}, "by-name");

	if($rebuild) {
		# pass 3: delete & recreate entire by-md5 tree
		rmtree("by-md5");
		print "Removed by-md5 tree, rebuilding\n";
		find({wanted => \&rebuild_wanted, no_chdir => 1}, "by-name");
	} else {
		# pass 3: find all by-md5 files, delete any whose md5sums aren't found
		# in any .info file.
		find({wanted => \&purge_pass_3_wanted, no_chdir => 1}, "by-md5");

		# pass 4: clean out (remove) any empty directories.
		trim_post();
	}

	printf("Purged $purgefiles files, %.1fMB\n", ($purgebytes / (1024 * 1024)));
	exit 0;
}

# helper for purge_mode, populates %keep_filenames and %keep_md5sums
sub purge_pass_1_wanted {
	return unless /\.info$/;
	my $dls = parse_info($_);
	my ($undef, $cat, $name, undef) = split /\//, $_;
	for(keys %$dls) {
		my $path = "by-name/$cat/$name/" . url_to_filename($_);
		$keep_filenames{$path}++;
		$keep_md5sums{$$dls{$_}}++;
	}
}

# helper for purge_mode, removes all files in category/prgnam/
# dirs that aren't listed in %keep_filenames
sub purge_pass_2_wanted {
	s,^\./,,; # remove leading ./
	my (undef, $cat, $name, $file) = split /\//, $_;
	return unless defined $file;
	return if $keep_filenames{"by-name/$cat/$name/$file"};

	$purgebytes += -s $_;
	$purgefiles++;

	my $namepath = name_dir($cat, $name) . "$file";
	#my $md5path = md5_dir(md5sum_file($namepath)) . "$file";

	#print "purge $namepath $md5path\n";
	print "purge $namepath\n";

	unlink $namepath unless $fake_purge;
	#unlink $md5path;
}

# helper for purge_mode, removes all files in by-md5
# dirs that aren't listed in %keep_md5sums
sub purge_pass_3_wanted {
	s,^\./,,; # remove leading ./
	my (undef, undef, undef, $md5sum, $filename) = split /\//, $_;
	return unless defined $md5sum; # only want the last dir...
	return if defined $filename; # and skip if it's not the dir

	if($keep_md5sums{$md5sum}) {
		#print "keep md5sum: $md5sum\n";
	} else {
		print "purge $_\n";
		rmtree(md5_dir($_)) unless $fake_purge;
	}
}

sub rebuild_wanted {
	return unless -f;

	s,^\./,,; # remove leading ./
	my $md5dir = md5_dir(md5sum_file($_));
	my (undef, $category, $prgnam, $filename) = split /\//, $_;

	mkpath($md5dir);

	if($symlinks) {
		symlink("../../../../by-name/" . $category . "/" . $prgnam . "/" . $filename,
				$md5dir . "/" . $filename);
	} else {
		link($_, $md5dir . "/" . $filename);
	}
}

# helper for trim_mode
sub trim_wanted {
	return unless -f $_;
	my $size = -s _;
	if(toobig($size)) {
		unlink($_);
		$trimcount++;
		$trimbytes += $size;
	}
}

# helper for trim_post
sub trim_post_wanted {
	return if $fake_purge;
	unlink $_ if -l $_ && ! -e _;
	return unless -d _;
	push @trim_empty_dirs, $_ if !<*>;
}

# pass 2 of trim_mode, also called by purge_mode. removes
# empty directories and dangling symlinks.
sub trim_post {
	chdir($archivedir) or die "$archivedir: $!\n";

	# can't rmdir from within find's wanted sub, or we get
	# lots of 'Can't opendir()' warnings. So collect all the
	# empty dirs in an array during the find, then rmdir them
	# all in one swell foop afterwards.
	@trim_empty_dirs = ();

	# remove dangling symlinks and make a list of empty dirs
	find({wanted => \&trim_post_wanted, no_chdir => 1}, ".");

	rmdir $_ for @trim_empty_dirs; # the aforementioned swell foop
}

# this mode doesn't know/care about the git stuff, it operates purely
# on the archive file tree.
sub trim_mode {
	chdir($archivedir) or die "$archivedir: $!\n";

	$trimcount = $trimbytes = 0;

	# first pass: remove files that are too big
	find({wanted => \&trim_wanted, no_chdir => 1}, ".");

	# 2nd pass
	trim_post();

	printf("Trimmed $trimcount files, %.1fMB\n", ($trimbytes / (1024 * 1024)));
	exit 0;
}

# in: "category/name"
# out: "category/name/name.info"
sub find_info_file {
	my $info = shift;
	$info =~ s,/([^/]+)$,/$1/$1.info,;
	return $info;
}

# FIXME: this will fail if @localfiles are absolute paths!
sub local_add {
	my ($oldcwd, $catname, $info, @localfiles) = @_;
	$catname =~ s,^\./,,;
	my ($category, $prgnam) = split /\//, $catname;
	my %localmd5s;

	for(@localfiles) {
		$localmd5s{md5sum_file("$oldcwd/$_")} = "$oldcwd/$_";
	}

	my $dls = parse_info($info);

	chdir($archivedir) or die "$archivedir: $!";
	for(keys %$dls) {
		my $targetfile = url_to_filename($_);

		my $md5 = $dls->{$_};
		my $localfile = $localmd5s{$md5};
		next unless $localfile;

		delete $localmd5s{$md5};

		copy($localfile, $targetfile);
		store_file($targetfile, $category, $prgnam, $md5);
		print "added $targetfile for $category/$prgnam\n";
	}

	for(keys %localmd5s) {
		print "$localmd5s{$_} ($_) ignored: doesn't match any md5sum in $info\n";
	}
}

sub add_by_md5_wanted {
	our %md5_to_dl;
	return unless /\.info/;
	s,\./,,;
	my ($category, $prgnam, undef) = split /\//;
	my $dls = parse_info($_);
	$md5_to_dl{$_} = "$category/$prgnam" for values %$dls;
}

sub add_by_md5 {
	print "no category/prgnam, adding file(s) by md5sum\n";
	my $oldcwd = shift;
	our %md5_to_dl;
	find({wanted => \&add_by_md5_wanted, no_chdir => 1}, ".");

	for my $filename (@_) {
		my $infile = $filename;
		$infile = "$oldcwd/$infile" unless $infile =~ m,^/,;

		my $md5 = md5sum_file($infile);
		next unless defined $md5;

		my $catname = $md5_to_dl{$md5} or do {
			print "$filename ($md5) doesn't match any .info file, skipping\n";
			next;
		};

		my $info = find_info_file($catname) or do {
			print "can't find info file for $catname";
			next;
		};

		local_add($oldcwd, $catname, $info, $filename);
		chdir($sbogitdir);
	}
}

sub add_or_rm_mode {
	my $oldcwd = POSIX::getcwd();
	init_git();
	my $mode = shift @ARGV;

	if($mode eq 'add' && @ARGV && (-f $ARGV[0] || -f "$oldcwd/$ARGV[0]")) {
		add_by_md5($oldcwd, @ARGV);
		exit 0;
	}

	my $catname = shift @ARGV or usage();

	$use_bwlist = 0;
	if($catname eq '-f') {
		$maxfilemegs = 0;
		$catname = shift(@ARGV) or usage();
	}

	my $info = find_info_file($catname);
	if(! -f $info) {
		die "Can't find $info in repo\n";
	}

	if($mode eq "add") {
		if(!@ARGV) { # no args, use URL(s) in .info file
			$_ = $info;
			handle_info_file();
		} else {
			local_add($oldcwd, $catname, $info, @ARGV);
		}
	} elsif($mode eq "rm") {
		my $dls = parse_info($info);
		for(keys %$dls) {
			my $md5 = $dls->{$_};
			my $filename = url_to_filename($_);
			my ($category, $prgname) = split /\//, $catname;
			unlink(name_dir($category, $prgname) . "/$filename");
			rmdir(name_dir($category, $prgname));
			unlink(md5_dir($md5) . "/$filename");
			rmdir(md5_dir($md5));
		}
	} else {
		die "this never happens";
	}
	exit 0;
}

# check_mode() needs to do this:

# Find/parse all info files, building hashes of filenames and md5sums

# Find all files in by-name, make sure the md5sums match, make sure the
# by-md5 file exists and is either a hardlink or symlink to the by-name
# file. If the size is over the limit, make a note of it. If the file
# isn't found in the hash of filenames, it's extraneous (and so is its
# by-md5 counterpart).

# Do the same thing for the by-md5 tree, more or less. If both hard and
# symolic links are found, that fact will get reported (but only once!)

# Print a report.

sub check_byname_wanted {
	if(-d) {
		my (undef, $category, $prgnam, $extra) = split /\//;

		if(defined($extra)) {
			print "misplaced dir (not a category/prgnam): $_\n";
		}

		return;
	}

	return unless -f _;

	$filecount++;

	my $size = -s _;
	$filebytes += $size;

	s,^\./,,;
	my (undef,  $category, $prgnam, $filename, $extra) = split /\//;

	if(!defined($filename) || defined($extra)) {
		print "misplaced file (not in a category/prgnam dir): $_\n";
		$filecount--;
		return;
	}

	my $shortname = join("/", $category, $prgnam, $filename);

	my $info = join("/", $sbogitdir, $category, $prgnam, $prgnam . ".info");
	if(!-f $info) {
		print "$shortname extraneous: no info file for $category/$prgnam\n";
		$filecount--;
		return;
	}

	my $dls = $parsedinfo{"$category/$prgnam"};
	my $md5 = md5sum_file($_) unless $quickcheck;
	my $foundfile;

	# make $info and printable (relative path only)
	$info = join("/", $category, $prgnam, $prgnam . ".info");

	for my $dl (keys %$dls) {
		my $infofilename = url_to_filename($dl);
		if($infofilename eq $filename) {
			$foundfile++;
			if(!$quickcheck) {
				if($md5 ne $dls->{$dl}) {
					print "$info: $shortname: wrong md5sum (should be $dls->{$dl})\n";
				} else {
# check by-md5 file existence only (check_bymd5_wanted will do more)
					my $md5file = md5_dir($md5) . "/" . $filename;
					if(! -e $md5file) {
						print "$info: $shortname: missing $md5file\n";
					}
				}
			}
		}
	}

	if($foundfile) {
		$infofilecount{"$category/$prgnam"}--;
	} else {
		print "$shortname extraneous: not mentioned in $info (sbosrcarch purge)\n";
		$filecount--;
	}

	if(blacklisted($category, $prgnam)) {
		print "$category/$prgnam blacklisted, but present in archive (sbosrcarch rm $category/$prgnam)?\n";
	}

	if(toobig($size)) {
		$size = sprintf("%.1f", $size / (1024 * 1024));
		print "$shortname (${size}MB) exceeds file size limit ${maxfilemegs}MB (add to whitelist or sbosrcarch rm $category/$prgnam)?\n";
	}
}

sub check_bymd5_wanted {
	return if -d;

	s,^\./,,;

	if(-l $_ && (! -e $_)) {
		print "dangling symlink: $_\n";
		return;
	}

	my $realmd5 = md5sum_file($_) || return;

	my (undef, $a, $b, $md5dir, $filename, $extra) = split /\//;

	if(!defined($filename) || defined($extra)) {
		print "$_: misplaced file (not in a a/b/md5sum dir)\n";
		return;
	}

	if(-l $_) {
		our $symlinkcount++;
	} else {
		my (undef, undef, undef, $nlink) = stat $_;
		if($nlink >= 2) {
			our $hardlinkcount++;
		} else {
			print "$_: not a symlink or hardlink\n";
		}
	}

	my $reala = substr($realmd5, 0, 1);
	my $realb = substr($realmd5, 1, 1);
	if($reala ne $a || $realb ne $b) {
		print "$_: wrong subdir (should be $reala/$realb/$realmd5)\n";
	}

	if($realmd5 ne $md5dir) {
		print "$_: md5sum mismatch\n";
	}
}

sub check_info_wanted {
	return unless /\.info/;
	s,\./,,;

	my ($category, $prgnam, $file) = split /\//;

	if(blacklisted("$category/$prgnam")) {
		warn "  $category/$prgnam blacklisted, skipping\n";
		return;
	}

	# 20180604 bkw: games/mrboom has a file named "mrboom_libretro.info"
	# which isn't an SBo info file. In general it's allowed for builds to
	# include other files with .info filenames, so this bit is to make
	# sure we're only looking at the real prgnam.info file:
	return unless $file eq ($prgnam . ".info");

	my $dls = parse_info($_);
	$totalfiles += keys %$dls;
	$infofilecount{"$category/$prgnam"} += keys %$dls;
	$parsedinfo{"$category/$prgnam"} = $dls;
}

sub check_mode {
	$quickcheck = shift; # 1 = don't md5sum stuff
	shift @ARGV;
	my $verbose = ($ARGV[0] && $ARGV[0] =~ /^-*v(?:erbose)?$/);

	$use_bwlist = 1;
	init_git();

	print "* Parsing .info files...\n";
	find({wanted => \&check_info_wanted, no_chdir => 1}, ".");

	chdir($archivedir) or die "$archivedir: $!";

	print "* Checking by-name tree...\n";
	find({wanted => \&check_byname_wanted, no_chdir => 1}, "by-name");

	if(!$quickcheck) {
		print "* Checking by-md5 tree...\n";
		find({wanted => \&check_bymd5_wanted, no_chdir => 1}, "by-md5");
	}

	my @missingfilebuilds;
	for(keys %infofilecount) {
		my $count = $infofilecount{$_};
		push @missingfilebuilds, $_ if $count;
	}

	if($verbose) {
		if(@missingfilebuilds) {
			print "Following SlackBuilds are missing files:\n";
			print "  $_\n" for sort { $a cmp $b } @missingfilebuilds;
		} else {
			print "All SlackBuild download files present\n";
		}
	}

	if($symlinkcount && $hardlinkcount) {
		print "by-md5 contains both symlinks and hardlinks (harmless but messy)\n";
	}

	my $totalbuildcount = keys %infofilecount;
	my $missingbuildcount = @missingfilebuilds;
	my $completebuildcount = $totalbuildcount - $missingbuildcount;
	my $coverage = sprintf("%.2f", ($completebuildcount * 100 / $totalbuildcount));
	my $filemegs = sprintf("%.1fMB", $filebytes / (1024 * 1024));
	my $missingfiles = $totalfiles - $filecount;
	my $filecoverage = sprintf("%.2f", $filecount * 100 / $totalfiles);

	print <<EOF;
---
Total source files: $totalfiles
Archived files: $filecount
Archive size: $filemegs
Missing files: $missingfiles
File coverage: $filecoverage%

Total SlackBuilds: $totalbuildcount
SlackBuilds with all files present: $completebuildcount
SlackBuilds missing at least one file: $missingbuildcount
SlackBuild coverage: $coverage%
EOF

	exit 0;
}

# test code for black/white lists, remove?
sub bwlist_mode {
	shift @ARGV;

	$use_bwlist = 1;

	print "\nblacklist:\n";
	print "\t(empty)\n" unless %blackhash;
	print "\t$_\n" for sort keys %blackhash;
	print "whitelist:\n";
	print "\t(empty)\n" unless %whitehash;
	print "\t$_\n" for sort keys %whitehash;
	print "\n";

	for(@ARGV) {
		print "$_: ";
		if(whitelisted($_)) {
			print "whitelisted";
		} elsif(blacklisted($_)) {
			print "blacklisted";
		} else {
			print "not listed in whitelist or blacklist";
		}
		print "\n";
	}

	exit 0;
}

sub usage {
	my $self = $0;
	$self =~ s,.*/,,;

	print <<EOF;
$self - create and maintain SBo source archive

Usage: $self <mode>

<mode> is one of:

  create
  update
  purge
  trim
  check
  add <category/prgname> [<file> ...]
  rm <category/prgname>

For full documentation try:
  perldoc $self
EOF

	exit 1
}

#main()

$|++;
usage() unless (defined $ARGV[0] && $ARGV[0] !~ /^-+h(?:elp)?/);
read_config();
for ($ARGV[0]) {
	/create/ && do { create_mode();    };
	/update/ && do { update_mode();    };
	/purge/  && do { purge_mode();     };
	/add/    && do { add_or_rm_mode(); };
	/rm/     && do { add_or_rm_mode(); };
	/trim/   && do { trim_mode();      };
	/check/  && do { check_mode(0);    };
	/status/ && do { check_mode(1);    };
	/bwlist/ && do { bwlist_mode();    };
	usage();
}

__END__