From b735fd32081b00b0c94196cf77c9b465703d8da5 Mon Sep 17 00:00:00 2001
From: Michael Vrable <mvrable@cs.ucsd.edu>
Date: Sat, 2 Jun 2007 17:14:13 -0700
Subject: [PATCH] Add version information to the backup descriptor files.

This adds a "Format:" line at the start of a backup descriptor, with the
intent that different formats can be recognized if there is a need to make
changes in the future.  This can also be used as a magic number to identify
LBS snapshot files.

Also, update the restore.pl script to handle the new format--make the
parser more flexible so that fields can appear in any order, and
unrecognized lines are ignored.
---
 restore.pl | 30 ++++++++++++++++++++++++++----
 scandir.cc |  1 +
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/restore.pl b/restore.pl
index 53b48dc..3a600b1 100755
--- a/restore.pl
+++ b/restore.pl
@@ -374,14 +374,36 @@ if (defined($ARGV[1])) {
 $OBJECT_DIR = dirname($descriptor);
 print "Source directory: $OBJECT_DIR\n" if $VERBOSE;
 
-# Read the snapshot descriptor to find the root object.
+# Read the snapshot descriptor to find the root object.  Parse it to get a set
+# of key/value pairs.
 open DESCRIPTOR, "<", $descriptor
     or die "Cannot open backup descriptor file $descriptor: $!";
-my $line = <DESCRIPTOR>;
-if ($line !~ m/^Root: (\S+)$/) {
+my %descriptor = ();
+my ($line, $last_key);
+while (defined($line = <DESCRIPTOR>)) {
+    # Any lines of the form "key: value" should be inserted into the
+    # %descriptor dictionary.  Any continuation line (a line starting with
+    # whitespace) will append text to the previous key's value.  Ignore other
+    # lines.
+    chomp $line;
+
+    if ($line =~ m/^(\w+):\s*(.*)$/) {
+        $descriptor{$1} = $2;
+        $last_key = $1;
+    } elsif ($line =~/^\s/ && defined $last_key) {
+        $descriptor{$last_key} .= $line;
+    } else {
+        undef $last_key;
+        print STDERR "Ignoring line in backup descriptor: $line\n";
+    }
+}
+
+# A valid backup descriptor should at the very least specify the root metadata
+# object.
+if (!exists $descriptor{Root}) {
     die "Expected 'Root:' specification in backup descriptor file";
 }
-my $root = $1;
+my $root = $descriptor{Root};
 close DESCRIPTOR;
 
 # Set the umask to something restrictive.  As we unpack files, we'll originally
diff --git a/scandir.cc b/scandir.cc
index 64a0dbf..bf4a583 100644
--- a/scandir.cc
+++ b/scandir.cc
@@ -485,6 +485,7 @@ int main(int argc, char *argv[])
     root->checksum();
 
     segment_list.insert(root->get_ref().get_segment());
+    descriptor << "Format: LBS Snapshot v0.1\n";
     descriptor << "Root: " << root->get_ref().to_string() << "\n";
     strftime(desc_buf, sizeof(desc_buf), "%Y-%m-%d %H:%M:%S %z", &time_buf);
     descriptor << "Date: " << desc_buf << "\n";
-- 
2.20.1