333 lines
		
	
	
	
		
			10 KiB
		
	
	
	
		
			Perl
		
	
	
	
	
	
			
		
		
	
	
			333 lines
		
	
	
	
		
			10 KiB
		
	
	
	
		
			Perl
		
	
	
	
	
	
use strict;
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use File::Temp qw(tempdir);
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use File::stat;
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# Some patch generations options.
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# Max size of NAR archives to generate patches for.
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my $maxNarSize = $ENV{"NIX_MAX_NAR_SIZE"};
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$maxNarSize = 160 * 1024 * 1024 if !defined $maxNarSize;
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# If patch is bigger than this fraction of full archive, reject.
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my $maxPatchFraction = $ENV{"NIX_PATCH_FRACTION"};
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$maxPatchFraction = 0.60 if !defined $maxPatchFraction;
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my $timeLimit = $ENV{"NIX_BSDIFF_TIME_LIMIT"};
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$timeLimit = 180 if !defined $timeLimit;
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my $hashAlgo = "sha256";
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sub findOutputPaths {
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    my $narFiles = shift;
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    my %outPaths;
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    foreach my $p (keys %{$narFiles}) {
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        # Ignore derivations.
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        next if ($p =~ /\.drv$/);
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        # Ignore builders (too much ambiguity -- they're all called
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        # `builder.sh').
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        next if ($p =~ /\.sh$/);
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        next if ($p =~ /\.patch$/);
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        # Don't bother including tar files etc.
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        next if ($p =~ /\.tar$/ || $p =~ /\.tar\.(gz|bz2|Z|lzma|xz)$/ || $p =~ /\.zip$/ || $p =~ /\.bin$/ || $p =~ /\.tgz$/ || $p =~ /\.rpm$/ || $p =~ /cvs-export$/ || $p =~ /fetchhg$/);
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        $outPaths{$p} = 1;
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    }
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    return %outPaths;
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}
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sub getNameVersion {
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    my $p = shift;
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    $p =~ /\/[0-9a-z]+((?:-[a-zA-Z][^\/-]*)+)([^\/]*)$/;
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    my $name = $1;
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    my $version = $2;
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    return undef unless defined $name && defined $version;
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    $name =~ s/^-//;
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    $version =~ s/^-//;
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    return ($name, $version);
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}
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# A quick hack to get a measure of the `distance' between two
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# versions: it's just the position of the first character that differs
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# (or 999 if they are the same).
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sub versionDiff {
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    my $s = shift;
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    my $t = shift;
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    my $i;
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    return 999 if $s eq $t;
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    for ($i = 0; $i < length $s; $i++) {
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        return $i if $i >= length $t or
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            substr($s, $i, 1) ne substr($t, $i, 1);
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    }
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    return $i;
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}
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sub getNarBz2 {
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    my $narPath = shift;
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    my $narFiles = shift;
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    my $storePath = shift;
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    my $narFileList = $$narFiles{$storePath};
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    die "missing path $storePath" unless defined $narFileList;
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    my $narFile = @{$narFileList}[0];
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    die unless defined $narFile;
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    $narFile->{url} =~ /\/([^\/]+)$/;
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    die unless defined $1;
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    return "$narPath/$1";
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}
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sub containsPatch {
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    my $patches = shift;
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    my $storePath = shift;
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    my $basePath = shift;
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    my $patchList = $$patches{$storePath};
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    return 0 if !defined $patchList;
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    my $found = 0;
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    foreach my $patch (@{$patchList}) {
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        # !!! baseHash might differ
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        return 1 if $patch->{basePath} eq $basePath;
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    }
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    return 0;
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}
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sub generatePatches {
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    my ($srcNarFiles, $dstNarFiles, $srcPatches, $dstPatches, $narPath, $patchesPath, $patchesURL, $tmpDir) = @_;
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    my %srcOutPaths = findOutputPaths $srcNarFiles;
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    my %dstOutPaths = findOutputPaths $dstNarFiles;
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    # For each output path in the destination, see if we need to / can
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    # create a patch.
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    print STDERR "creating patches...\n";
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    foreach my $p (keys %dstOutPaths) {
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        # If exactly the same path already exists in the source, skip it.
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        next if defined $srcOutPaths{$p};
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        print "  $p\n";
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        # If not, then we should find the paths in the source that are
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        # `most' likely to be present on a system that wants to
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        # install this path.
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        (my $name, my $version) = getNameVersion $p;
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        next unless defined $name && defined $version;
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        my @closest = ();
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        my $closestVersion;
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        my $minDist = -1; # actually, larger means closer
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        # Find all source paths with the same name.
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        foreach my $q (keys %srcOutPaths) {
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            (my $name2, my $version2) = getNameVersion $q;
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            next unless defined $name2 && defined $version2;
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            if ($name eq $name2) {
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                my $srcSystem = @{$$dstNarFiles{$p}}[0]->{system};
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                my $dstSystem = @{$$srcNarFiles{$q}}[0]->{system};
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                if (defined $srcSystem && defined $dstSystem && $srcSystem ne $dstSystem) {
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                    print "    SKIPPING $q due to different systems ($srcSystem vs. $dstSystem)\n";
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                    next;
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                }
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                # If the sizes differ too much, then skip.  This
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                # disambiguates between, e.g., a real component and a
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                # wrapper component (cf. Firefox in Nixpkgs).
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                my $srcSize = @{$$srcNarFiles{$q}}[0]->{size};
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                my $dstSize = @{$$dstNarFiles{$p}}[0]->{size};
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                my $ratio = $srcSize / $dstSize;
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                $ratio = 1 / $ratio if $ratio < 1;
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                # print "  SIZE $srcSize $dstSize $ratio $q\n";
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                if ($ratio >= 3) {
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                    print "    SKIPPING $q due to size ratio $ratio ($srcSize vs. $dstSize)\n";
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                    next;
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                }
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                # If there are multiple matching names, include the
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                # ones with the closest version numbers.
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                my $dist = versionDiff $version, $version2;
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                if ($dist > $minDist) {
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                    $minDist = $dist;
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                    @closest = ($q);
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                    $closestVersion = $version2;
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                } elsif ($dist == $minDist) {
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                    push @closest, $q;
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                }
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            }
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        }
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        if (scalar(@closest) == 0) {
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            print "    NO BASE: $p\n";
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            next;
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        }
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        foreach my $closest (@closest) {
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            # Generate a patch between $closest and $p.
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            print STDERR "  $p <- $closest\n";
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            # If the patch already exists, skip it.
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            if (containsPatch($srcPatches, $p, $closest) ||
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                containsPatch($dstPatches, $p, $closest))
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            {
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                print "    skipping, already exists\n";
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                next;
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            }
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            my $srcNarBz2 = getNarBz2 $narPath, $srcNarFiles, $closest;
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            my $dstNarBz2 = getNarBz2 $narPath, $dstNarFiles, $p;
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            if (! -f $srcNarBz2) {
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                warn "patch source archive $srcNarBz2 is missing\n";
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                next;
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            }
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            system("@bunzip2@ < $srcNarBz2 > $tmpDir/A") == 0
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                or die "cannot unpack $srcNarBz2";
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            if (stat("$tmpDir/A")->size >= $maxNarSize) {
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                print "    skipping, source is too large\n";
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                next;
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            }
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            system("@bunzip2@ < $dstNarBz2 > $tmpDir/B") == 0
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                or die "cannot unpack $dstNarBz2";
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            if (stat("$tmpDir/B")->size >= $maxNarSize) {
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                print "    skipping, destination is too large\n";
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                next;
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            }
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            my $time1 = time();
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            my $res = system("ulimit -t $timeLimit; @libexecdir@/bsdiff $tmpDir/A $tmpDir/B $tmpDir/DIFF");
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            my $time2 = time();
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            if ($res) {
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                warn "binary diff computation aborted after ", $time2 - $time1, " seconds\n";
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                next;
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            }
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            my $baseHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/A` or die;
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            chomp $baseHash;
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            my $narHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/B` or die;
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            chomp $narHash;
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            my $narDiffHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/DIFF` or die;
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            chomp $narDiffHash;
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            my $narDiffSize = stat("$tmpDir/DIFF")->size;
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            my $dstNarBz2Size = stat($dstNarBz2)->size;
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            print "    size $narDiffSize; full size $dstNarBz2Size; ", $time2 - $time1, " seconds\n";
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            if ($narDiffSize >= $dstNarBz2Size) {
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                print "    rejecting; patch bigger than full archive\n";
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                next;
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            }
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            if ($narDiffSize / $dstNarBz2Size >= $maxPatchFraction) {
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                print "    rejecting; patch too large relative to full archive\n";
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                next;
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            }
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            my $finalName = "$narDiffHash.nar-bsdiff";
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            if (-e "$patchesPath/$finalName") {
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                print "    not copying, already exists\n";
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            }
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            else {
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                system("cp '$tmpDir/DIFF' '$patchesPath/$finalName.tmp'") == 0
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                    or die "cannot copy diff";
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                rename("$patchesPath/$finalName.tmp", "$patchesPath/$finalName")
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                    or die "cannot rename $patchesPath/$finalName.tmp";
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            }
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            # Add the patch to the manifest.
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            addPatch $dstPatches, $p,
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                { url => "$patchesURL/$finalName", hash => "$hashAlgo:$narDiffHash"
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                , size => $narDiffSize, basePath => $closest, baseHash => "$hashAlgo:$baseHash"
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                , narHash => "$hashAlgo:$narHash", patchType => "nar-bsdiff"
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                };
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        }
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    }
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}
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# Propagate useful patches from $srcPatches to $dstPatches.  A patch
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# is useful if it produces either paths in the $dstNarFiles or paths
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# that can be used as the base for other useful patches.
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sub propagatePatches {
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    my ($srcPatches, $dstNarFiles, $dstPatches) = @_;
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    print STDERR "propagating patches...\n";
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    my $changed;
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    do {
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        # !!! we repeat this to reach the transitive closure; inefficient
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        $changed = 0;
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        print STDERR "loop\n";
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        my %dstBasePaths;
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        foreach my $q (keys %{$dstPatches}) {
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            foreach my $patch (@{$$dstPatches{$q}}) {
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                $dstBasePaths{$patch->{basePath}} = 1;
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            }
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        }
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        foreach my $p (keys %{$srcPatches}) {
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            my $patchList = $$srcPatches{$p};
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            my $include = 0;
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            # Is path $p included in the destination?  If so, include
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            # patches that produce it.
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            $include = 1 if defined $$dstNarFiles{$p};
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            # Is path $p a path that serves as a base for paths in the
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            # destination?  If so, include patches that produce it.
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            # !!! check baseHash
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            $include = 1 if defined $dstBasePaths{$p};
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            if ($include) {
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                foreach my $patch (@{$patchList}) {
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                    $changed = 1 if addPatch $dstPatches, $p, $patch;
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                }
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            }
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        }
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    } while $changed;
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}
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# Add all new patches in $srcPatches to $dstPatches.
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sub copyPatches {
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    my ($srcPatches, $dstPatches) = @_;
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    foreach my $p (keys %{$srcPatches}) {
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        addPatch $dstPatches, $p, $_ foreach @{$$srcPatches{$p}};
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    }
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}
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return 1;
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