From 5088b10449d20ba24448ee3230d260bdda605208 Mon Sep 17 00:00:00 2001
From: Joey Hess <joey@kitenet.net>
Date: Tue, 31 Jan 2012 16:13:21 -0400
Subject: [PATCH] xz: try levels 6 and 9

---
 debian/changelog |  4 +++-
 debian/control   |  2 +-
 pristine-xz      | 33 ++++++++++++++++++---------------
 3 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/debian/changelog b/debian/changelog
index 3133f38..cbb9ed9 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,6 +1,8 @@
 pristine-tar (1.18) UNRELEASED; urgency=low
 
-  * pristine-xz: A very simplistic xz recreator.
+  * pristine-xz: A simplistic xz recreator, supporting only the
+    most common xz files. Current success rate on the Debian corpus: 70%.
+    Closes: #499489
 
  -- Joey Hess <joeyh@debian.org>  Mon, 09 Jan 2012 12:36:57 -0400
 
diff --git a/debian/control b/debian/control
index 2a392a2..e38eaa5 100644
--- a/debian/control
+++ b/debian/control
@@ -12,7 +12,7 @@ Package: pristine-tar
 Architecture: any
 Section: utils
 Depends: xdelta, ${shlibs:Depends}, ${misc:Depends}, perl-modules
-Recommends: pbzip2, bzip2
+Recommends: pbzip2, bzip2, xz-utils
 Description: regenerate pristine tarballs
  pristine-tar can regenerate a pristine upstream tarball using only a small
  binary delta file and a revision control checkout of the upstream branch.
diff --git a/pristine-xz b/pristine-xz
index a0365b3..678193e 100755
--- a/pristine-xz
+++ b/pristine-xz
@@ -108,21 +108,25 @@ sub readxz {
 		error "This is not a valid xz archive.";
 	}
 
-	# XXX This is the default compression level; we don't currently have
-	# a way to guess the level from the file format, as this level only
-	# presets several other tunables. Correct handling would involve
-	# finding as many preset values as possible, and reconstructing the
-	# compression level from that.
-	my $level = 6;
-
-	return ($level);
+	# XXX We don't currently have a way to guess the level from the
+	# file format, as this level only presets several other tunables.
+	# Correct handling would involve finding as many preset values as
+	# possible, and reconstructing the compression level from that.
+	#
+	# So far in the wild only these levels have been seen.
+	# (Note that level 9 can use a lot of memory.)
+	my $possible_levels = [6, 9];
+
+	return ($possible_levels);
 }
 
 sub predictxzargs {
-	my ($level, $program) = @_;
-
-	my @args=["-z", "-$level"];
+	my ($possible_levels, $program) = @_;
 
+	my @args;
+	foreach my $level (@$possible_levels) {
+		push @args, ["-z", "-$level"];
+	}
 	return @args;
 }
 
@@ -154,13 +158,12 @@ sub reproducexz {
 	doit_redir($orig, $tmpin, "xz", "-dc");
 
 	# read fields from xz headers
-	my ($level) = readxz($orig);
-	debug("level: $level");
+	my ($possible_levels) = readxz($orig);
 
 	foreach my $program (@supported_xz_programs) {
 		# try to guess the xz arguments that are needed by the
 		# header information
-		foreach my $args (predictxzargs($level, $program)) {
+		foreach my $args (predictxzargs($possible_levels, $program)) {
 			testvariant($orig, $tmpin, $program, @$args)
 				&& return $program, @$args;
 		}
@@ -183,7 +186,7 @@ sub genxz {
 	while (@params) {
 		my $param=shift @params;
 
-		next if $param=~/^(-[1-9])$/;
+		next if $param=~/^(-[0-9])$/;
 		next if $param eq '-z';
 		die "paranoia check failed on params from delta (@params)";
 	}
-- 
2.7.4