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* Impose a configurable time limit on patch generation. This is

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necessary because bsdiff has some pathological worst-case behaviour,
  e.g. O(n^2) on files consisting only of 0s.
This commit is contained in:
Eelco Dolstra 2010-11-29 09:15:45 +00:00
parent 703e5a2ce2
commit bd48fd97f6
1 changed files with 12 additions and 6 deletions
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18
scripts/generate-patches.pl.in
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@ -15,6 +15,9 @@ $maxNarSize = 100 * 1024 * 1024 if !defined $maxNarSize;
my $maxPatchFraction = $ENV{"NIX_PATCH_FRACTION"};
$maxPatchFraction = 0.60 if !defined $maxPatchFraction;
my $timeLimit = $ENV{"NIX_BSDIFF_TIME_LIMIT"};
$timeLimit = 180 if !defined $timeLimit;
die unless scalar @ARGV == 5;
@ -29,8 +32,6 @@ my $dstManifest = $ARGV[4];
my $tmpDir = tempdir("nix-generate-patches.XXXXXX", CLEANUP => 1, TMPDIR => 1)
or die "cannot create a temporary directory";
print "TEMP = $tmpDir\n";
#END { rmdir $tmpDir; }
my %srcNarFiles;
@ -223,7 +224,7 @@ foreach my $p (keys %dstOutPaths) {
foreach my $q (keys %srcOutPaths) {
(my $name2, my $version2) = getNameVersion $q;
next unless defined $name2 && defined $version2;
next unless defined $name2 && defined $version2;
if ($name eq $name2) {
@ -312,8 +313,13 @@ foreach my $p (keys %dstOutPaths) {
next;
}
system("@libexecdir@/bsdiff $tmpDir/A $tmpDir/B $tmpDir/DIFF") == 0
or die "cannot compute binary diff";
my $time1 = time();
my $res = system("ulimit -t $timeLimit; @libexecdir@/bsdiff $tmpDir/A $tmpDir/B $tmpDir/DIFF");
my $time2 = time();
if ($res) {
warn "binary diff computation aborted after ", $time2 - $time1, " seconds\n";
next;
}
my $baseHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/A` or die;
chomp $baseHash;
@ -327,7 +333,7 @@ foreach my $p (keys %dstOutPaths) {
my $narDiffSize = (stat "$tmpDir/DIFF")[7];
my $dstNarBz2Size = (stat $dstNarBz2)[7];
print " size $narDiffSize; full size $dstNarBz2Size\n";
print " size $narDiffSize; full size $dstNarBz2Size; ", $time2 - $time1, " seconds\n";
if ($narDiffSize >= $dstNarBz2Size) {
print " rejecting; patch bigger than full archive\n";