Implement bidirectional iteration over lists.

* include/mailutils/iterator.h (mu_itrctl_qry_direction)
(mu_itrctl_set_direction): New mu_itrctl_req constants.
* mailbox/iterator.c (mu_iterator_dup): Bugfix: copy dup as well.
* mailbox/list.c (struct list_iterator)
<backwards>: New member.
(first, next): Move direction depends on the value
of list_iterator.backwards.
(list_itrctl): Handle mu_itrctl_qry_direction and
mu_itrctl_set_direction

* examples/listop.c (ictl_dir): New function.
(ictl_ins): Handle new subcommand "dir".
(help): Show new subcommand "dir".
* mailbox/testsuite/mailbox/list.exp: Add tests for
iteration backwards.

@@ -285,6 +285,41 @@ ictl_repl (mu_iterator_t itr, int argc, char **argv)
 }
 
 void
+ictl_dir (mu_iterator_t itr, int argc, char **argv)
+{
+  int rc;
+  int dir;
+  
+  if (argc > 1)
+    {
+      fprintf (stderr, "ictl dir [backwards|forwards]?\n");
+      return;
+    }
+  if (argc == 1)
+    {
+      if (strcmp (argv[0], "backwards") == 0)
+	dir = 1;
+      else if (strcmp (argv[0], "forwards") == 0)
+	dir = 0;
+      else
+	{
+	  fprintf (stderr, "ictl dir [backwards|forwards]?\n");
+	  return;
+	}
+      rc = mu_iterator_ctl (itr, mu_itrctl_set_direction, &dir);
+      if (rc)
+	lperror ("mu_iterator_ctl", rc);
+    }
+  else
+    {
+      rc = mu_iterator_ctl (itr, mu_itrctl_qry_direction, &dir);
+      if (rc)
+	lperror ("mu_iterator_ctl", rc);
+      printf ("%s\n", dir ? "backwards" : "forwards");
+    }
+}
+  
+void
 ictl_ins (mu_iterator_t itr, int argc, char **argv)
 {
   int rc;
@@ -324,6 +359,8 @@ ictl (mu_iterator_t itr, int argc, char **argv)
     ictl_repl (itr, argc - 2, argv + 2);
   else if (strcmp (argv[1], "ins") == 0)
     ictl_ins (itr, argc - 2, argv + 2);
+  else if (strcmp (argv[1], "dir") == 0)
+    ictl_dir (itr, argc - 2, argv + 2);
   else
     fprintf (stderr, "unknown subcommand\n");
 }
@@ -391,6 +428,7 @@ help ()
   printf ("ictl del\n");
   printf ("ictl repl item\n");
   printf ("ictl ins item [item*]\n");
+  printf ("ictl dir [backwards|forwards]\n");
   printf ("print\n");
   printf ("quit\n");
   printf ("iter num\n");

@@ -28,13 +28,15 @@ extern "C" {
 
 enum mu_itrctl_req
   {
-    mu_itrctl_tell,        /* Return current position in the object */
-    mu_itrctl_delete,      /* Delete current element */
-    mu_itrctl_delete_nd,   /* Delete current element, non-destructive */
-    mu_itrctl_replace,     /* Replace current element */
-    mu_itrctl_replace_nd,  /* Replace current element, non-destructive */
-    mu_itrctl_insert,      /* Insert new element in the current position */
-    mu_itrctl_insert_list, /* Insert a list of elements */
+    mu_itrctl_tell,          /* Return current position in the object */
+    mu_itrctl_delete,        /* Delete current element */
+    mu_itrctl_delete_nd,     /* Delete current element, non-destructive */
+    mu_itrctl_replace,       /* Replace current element */
+    mu_itrctl_replace_nd,    /* Replace current element, non-destructive */
+    mu_itrctl_insert,        /* Insert new element in the current position */
+    mu_itrctl_insert_list,   /* Insert a list of elements */
+    mu_itrctl_qry_direction, /* Query iteration direction */
+    mu_itrctl_set_direction  /* Set iteration direction */
   };
   
 extern int mu_iterator_create   (mu_iterator_t *, void *);

@@ -145,14 +145,15 @@ mu_iterator_dup (mu_iterator_t *piterator, mu_iterator_t orig)
       return status;
     }
   iterator->is_advanced = orig->is_advanced;   
+  iterator->dup = orig->dup;
+  iterator->destroy = orig->destroy;
   iterator->first = orig->first;
   iterator->next = orig->next;
   iterator->getitem = orig->getitem;
-  iterator->finished_p = orig->finished_p;
   iterator->curitem_p = orig->curitem_p;
-  iterator->dup = orig->dup;
-  iterator->destroy = orig->destroy;
-
+  iterator->finished_p = orig->finished_p;
+  iterator->itrctl = orig->itrctl;
+  
   *piterator = iterator;
   return 0;
 }

@@ -479,13 +479,17 @@ struct list_iterator
 {
   mu_list_t list;
   struct list_data *cur;
+  int backwards; /* true if iterating backwards */
 };
 
 static int
 first (void *owner)
 {
   struct list_iterator *itr = owner;
-  itr->cur = itr->list->head.next;
+  if (itr->backwards)
+    itr->cur = itr->list->head.prev;
+  else
+    itr->cur = itr->list->head.next;
   return 0;
 }
 
@@ -493,7 +497,10 @@ static int
 next (void *owner)
 {
   struct list_iterator *itr = owner;
-  itr->cur = itr->cur->next;
+  if (itr->backwards)
+    itr->cur = itr->cur->prev;
+  else
+    itr->cur = itr->cur->next;
   return 0;
 }
 
@@ -618,6 +625,20 @@ list_itrctl (void *owner, enum mu_itrctl_req req, void *arg)
 	  _mu_list_clear (new_list);
 	}
       break;
+
+    case mu_itrctl_qry_direction:
+      if (!arg)
+	return EINVAL;
+      else
+	*(int*)arg = itr->backwards;
+      break;
+
+    case mu_itrctl_set_direction:
+      if (!arg)
+	return EINVAL;
+      else
+	itr->backwards = !!*(int*)arg;
+      break;
       
     default:
       return ENOSYS;

@@ -301,6 +301,29 @@ mailbox_prog_test "print" \
 prompt_text "tres"
 mailbox_prog_test "next"
 
+mailbox_prog_test "ictl dir" "forwards"
+
+mailbox_prog_test "ictl dir backwards"
+
+prompt_text "dos"
+mailbox_prog_test "next"
+
+prompt_text "dwa"
+mailbox_prog_test "next 4"
+
+prompt_text "jeden"
+mailbox_prog_test "ictl del"
+
+mailbox_prog_test "next"
+
+prompt_text "zero"
+mailbox_prog_test "next"
+
+mailbox_prog_test "ictl dir forwards"
+
+prompt_text "jeden"
+mailbox_prog_test "next"
+
 mailbox_prog_send "quit"
 mailbox_prog_stop