--- loncom/lonnet/perl/lonnet.pm	2012/06/24 18:03:29	1.1172.2.7
+++ loncom/lonnet/perl/lonnet.pm	2012/08/01 04:56:54	1.1172.2.8
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # TCP networking package
 #
-# $Id: lonnet.pm,v 1.1172.2.7 2012/06/24 18:03:29 raeburn Exp $
+# $Id: lonnet.pm,v 1.1172.2.8 2012/08/01 04:56:54 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -9812,6 +9812,41 @@ sub devalidate_slots_cache {
     &devalidate_cache_new('allslots',$hashid);
 }
 
+sub get_coursechange {
+    my ($cdom,$cnum) = @_;
+    if ($cdom eq '' || $cnum eq '') {
+        return unless ($env{'request.course.id'});
+        $cnum = $env{'course.'.$env{'request.course.id'}.'.num'};
+        $cdom = $env{'course.'.$env{'request.course.id'}.'.domain'};
+    }
+    my $hashid=$cdom.'_'.$cnum;
+    my ($change,$cached)=&is_cached_new('crschange',$hashid);
+    if ((defined($cached)) && ($change ne '')) {
+        return $change;
+    } else {
+        my %crshash;
+        %crshash = &get('environment',['internal.contentchange'],$cdom,$cnum);
+        if ($crshash{'internal.contentchange'} eq '') {
+            $change = $env{'course.'.$cdom.'_'.$cnum.'.internal.created'};
+            if ($change eq '') {
+                %crshash = &get('environment',['internal.created'],$cdom,$cnum);
+                $change = $crshash{'internal.created'};
+            }
+        } else {
+            $change = $crshash{'internal.contentchange'};
+        }
+        my $cachetime = 600;
+        &do_cache_new('crschange',$hashid,$change,$cachetime);
+    }
+    return $change;
+}
+
+sub devalidate_coursechange_cache {
+    my ($cnum,$cdom)=@_;
+    my $hashid=$cnum.':'.$cdom;
+    &devalidate_cache_new('crschange',$hashid);
+}
+
 # ------------------------------------------------- Update symbolic store links
 
 sub symblist {
@@ -9956,7 +9991,11 @@ sub deversion {
 sub symbread {
     my ($thisfn,$donotrecurse)=@_;
     my $cache_str='request.symbread.cached.'.$thisfn;
-    if (defined($env{$cache_str})) { return $env{$cache_str}; }
+    if (defined($env{$cache_str})) {
+        if (($thisfn) || ($env{$cache_str} ne '')) {
+            return $env{$cache_str};
+        }
+    }
 # no filename provided? try from environment
     unless ($thisfn) {
         if ($env{'request.symb'}) {