91 lines
2 KiB
Perl
Executable file
91 lines
2 KiB
Perl
Executable file
#! /usr/bin/perl -w
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use strict;
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use File::Basename;
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my @paths = ("/nix/store");
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print "hashing...\n";
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my $hashList = "/tmp/nix-optimise-hash-list";
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system("find @paths -type f -print0 | xargs -0 md5sum -- > $hashList") == 0
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or die "cannot hash store files";
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print "sorting by hash...\n";
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system("sort $hashList > $hashList.sorted") == 0
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or die "cannot sort list";
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sub atomicLink {
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my $target = shift;
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my $new = shift;
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my $tmpNew = "${new}_optimise.$$";
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# Make the directory writable temporarily.
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my $dir = dirname $new;
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my @st = stat $dir or die;
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chmod ($st[2] | 0200, $dir) or die "cannot make `$dir' writable: $!";
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link $target, $tmpNew or die "cannot create hard link `$tmpNew': $!";
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rename $tmpNew, $new or die "cannot rename `$tmpNew' to `$new': $!";
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chmod ($st[2], $dir) or die "cannot restore permission on `$dir': $!";
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utime ($st[8], $st[9], $dir) or die "cannot restore timestamp on `$dir': $!";
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}
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print "hard-linking...\n";
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open LIST, "<$hashList.sorted" or die;
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my $prevFile;
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my $prevHash;
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my $prevInode;
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my $prevExec;
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my $totalSpace = 0;
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my $savedSpace = 0;
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while (<LIST>) {
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/^([0-9a-f]*)\s+(.*)$/ or die;
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my $curFile = $2;
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my $curHash = $1;
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my @st = stat $curFile or die;
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next if ($st[2] & 0222) != 0; # skip writable files
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my $fileSize = $st[7];
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$totalSpace += $fileSize;
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my $isExec = ($st[2] & 0111) == 0111;
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if (defined $prevHash && $curHash eq $prevHash
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&& $prevExec == $isExec)
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{
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if ($st[1] != $prevInode) {
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print "$curFile = $prevFile\n";
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atomicLink $prevFile, $curFile;
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$savedSpace += $fileSize;
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}
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} else {
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$prevFile = $curFile;
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$prevHash = $curHash;
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$prevInode = $st[1];
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$prevExec = ($st[2] & 0111) == 0111;
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}
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}
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print "total space = $totalSpace\n";
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print "saved space = $savedSpace\n";
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my $savings = ($savedSpace / $totalSpace) * 100.0;
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print "savings = $savings %\n";
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close LIST;
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