bd48fd97f6
necessary because bsdiff has some pathological worst-case behaviour, e.g. O(n^2) on files consisting only of 0s.
422 lines
12 KiB
Perl
Executable file
422 lines
12 KiB
Perl
Executable file
#! @perl@ -w -I@libexecdir@/nix
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use strict;
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use File::Temp qw(tempdir);
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use readmanifest;
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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 = 100 * 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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die unless scalar @ARGV == 5;
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my $hashAlgo = "sha256";
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my $narDir = $ARGV[0];
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my $patchesDir = $ARGV[1];
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my $patchesURL = $ARGV[2];
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my $srcManifest = $ARGV[3];
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my $dstManifest = $ARGV[4];
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my $tmpDir = tempdir("nix-generate-patches.XXXXXX", CLEANUP => 1, TMPDIR => 1)
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or die "cannot create a temporary directory";
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#END { rmdir $tmpDir; }
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my %srcNarFiles;
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my %srcLocalPaths;
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my %srcPatches;
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my %dstNarFiles;
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my %dstLocalPaths;
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my %dstPatches;
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readManifest "$srcManifest",
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\%srcNarFiles, \%srcLocalPaths, \%srcPatches;
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readManifest "$dstManifest",
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\%dstNarFiles, \%dstLocalPaths, \%dstPatches;
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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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print "finding src output paths...\n";
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my %srcOutPaths = findOutputPaths \%srcNarFiles;
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print "finding dst output paths...\n";
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my %dstOutPaths = findOutputPaths \%dstNarFiles;
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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 $narFiles = shift;
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my $storePath = shift;
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my $narFileList = $$narFiles{$storePath};
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die "missing path $storePath" unless defined $narFileList;
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my $narFile = @{$narFileList}[0];
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die unless defined $narFile;
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$narFile->{url} =~ /\/([^\/]+)$/;
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die unless defined $1;
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return "$narDir/$1";
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}
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sub containsPatch {
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my $patches = shift;
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my $storePath = shift;
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my $basePath = shift;
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my $patchList = $$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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# Compute the "weighted" number of uses of a path in the build graph.
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sub computeUses {
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my $narFiles = shift;
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my $path = shift;
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# Find the deriver of $path.
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return 1 unless defined $$narFiles{$path};
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my $deriver = @{$$narFiles{$path}}[0]->{deriver};
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return 1 unless defined $deriver && $deriver ne "";
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# print " DERIVER $deriver\n";
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# Optimisation: build the referrers graph from the references
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# graph.
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my %referrers;
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foreach my $q (keys %{$narFiles}) {
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my @refs = split " ", @{$$narFiles{$q}}[0]->{references};
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foreach my $r (@refs) {
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$referrers{$r} = [] unless defined $referrers{$r};
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push @{$referrers{$r}}, $q;
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}
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}
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# Determine the shortest path from $deriver to all other reachable
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# paths in the `referrers' graph.
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my %dist;
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$dist{$deriver} = 0;
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my @queue = ($deriver);
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my $pos = 0;
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while ($pos < scalar @queue) {
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my $p = $queue[$pos];
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$pos++;
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foreach my $q (@{$referrers{$p}}) {
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if (!defined $dist{$q}) {
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$dist{$q} = $dist{$p} + 1;
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# print " $q $dist{$q}\n";
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push @queue, $q;
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}
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}
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}
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my $wuse = 1.0;
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foreach my $user (keys %dist) {
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next if $user eq $deriver;
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# print " $user $dist{$user}\n";
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$wuse += 1.0 / 2.0**$dist{$user};
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}
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# print " XXX $path $wuse\n";
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return $wuse;
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}
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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 "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 install
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# 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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# 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 $dstSize)\n";
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next;
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}
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# If the numbers of weighted uses differ too much, then
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# skip. This disambiguates between, e.g., the bootstrap
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# GCC and the final GCC in Nixpkgs.
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# my $srcUses = computeUses \%srcNarFiles, $q;
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# my $dstUses = computeUses \%dstNarFiles, $p;
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# $ratio = $srcUses / $dstUses;
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# $ratio = 1 / $ratio if $ratio < 1;
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# print " USE $srcUses $dstUses $ratio $q\n";
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# if ($ratio >= 2) {
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# print " SKIPPING $q due to use ratio $ratio ($srcUses $dstUses)\n";
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# next;
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# }
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# If there are multiple matching names, include the ones
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# 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 " $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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# next;
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my $srcNarBz2 = getNarBz2 \%srcNarFiles, $closest;
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my $dstNarBz2 = getNarBz2 \%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")[7] >= $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")[7] >= $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")[7];
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my $dstNarBz2Size = (stat $dstNarBz2)[7];
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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 $finalName =
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"$narDiffHash.nar-bsdiff";
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if (-e "$patchesDir/$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 '$tmpDir/DIFF' '$patchesDir/$finalName.tmp'") == 0
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or die "cannot copy diff";
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rename("$patchesDir/$finalName.tmp", "$patchesDir/$finalName")
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or die "cannot rename $patchesDir/$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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}, 0;
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}
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}
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# Add in any potentially useful patches in the source (namely, those
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# patches that produce either paths in the destination or paths that
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# can be used as the base for other useful patches).
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print "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 "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 $changed;
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# Rewrite the manifest of the destination (with the new patches).
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writeManifest "${dstManifest}",
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\%dstNarFiles, \%dstPatches;
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