Implement LIFO access functions for lists.

* include/mailutils/list.h (mu_list_push)
(mu_list_pop): New functions.
* libmailutils/list/pop.c: New file.
* libmailutils/list/push.c: New file.
* libmailutils/list/Makefile.am (liblist_la_SOURCES): Add new files.
* libmailutils/tests/list.at: Test LIFO access.
* libmailutils/tests/listop.c: Implement push & pop.

@@ -124,6 +124,13 @@ int mu_list_replace  (mu_list_t _list, void *_old_item, void *_new_item);
   /* A non-destructive version of mu_list_replace: the removed item is not
      deallocated. */
 int mu_list_replace_nd (mu_list_t _list, void *_old_item, void *_new_item);
+
+  /* ************************************************* */
+  /* LIFO Access                                       */
+  /* ************************************************* */
+int mu_list_push (mu_list_t list, void *item);
+int mu_list_pop (mu_list_t list, void **item);
+  
 
   /* ************************************************* */
   /* Interation over lists.                            */

@@ -37,7 +37,9 @@ liblist_la_SOURCES = \
  listlist.c\
  locate.c\
  map.c\
+ pop.c\
  prepend.c\
+ push.c\
  remove.c\
  replace.c\
  rfold.c\

+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 2011 Free Software Foundation, Inc.
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General
+   Public License along with this library.  If not, see 
+   <http://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <stdlib.h>
+#include <mailutils/sys/list.h>
+#include <mailutils/errno.h>
+
+int
+mu_list_pop (mu_list_t list, void **item)
+{
+  struct list_data *last, *prev;
+  
+  if (list == NULL)
+    return EINVAL;
+
+  if (list->count == 0)
+    return MU_ERR_NOENT;
+
+  last = list->head.prev;
+  prev = last->prev;
+  mu_iterator_advance (list->itr, last);
+  prev->next = last->next;
+  prev->next->prev = prev;
+  if (item)
+    *item = last->item;
+  else
+    DESTROY_ITEM (list, last);
+  free (last);
+  list->count--;
+  return 0;
+}

+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 2011 Free Software Foundation, Inc.
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General
+   Public License along with this library.  If not, see 
+   <http://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <stdlib.h>
+#include <mailutils/sys/list.h>
+#include <mailutils/errno.h>
+
+int
+mu_list_push (mu_list_t list, void *item)
+{
+  return mu_list_append (list, item);
+}

@@ -97,6 +97,31 @@ tre
 fem
 ])
 
+TESTLIST([push],[],
+[push en to tre
+print],
+[# items: 3
+en
+to
+tre
+])
+
+TESTLIST([pop],[],
+[push en to tre
+pop
+pop
+pop],
+[tre
+to
+en
+])
+
+TESTLIST([pop-null],[],
+[pop],
+[],
+[mu_list_pop: Requested item not found
+])
+
 TESTLIST([get],[],
 [add en to tre fire fem
 3],

@@ -781,6 +781,42 @@ sort (mu_list_t list)
 }
 
 void
+push (mu_list_t list, int argc, char **argv)
+{
+  if (argc < 2)
+    {
+      fprintf (stderr, "push arg [arg] ?\n");
+      return;
+    }
+
+  while (--argc)
+    {
+      int rc = mu_list_push (list, strdup (*++argv));
+      if (rc)
+	fprintf (stderr, "mu_list_push: %s\n", mu_strerror (rc));
+    }
+}
+
+void
+pop (mu_list_t list, int argc, char **argv)
+{
+  char *text;
+  int rc;
+  
+  if (argc != 1)
+    {
+      fprintf (stderr, "pop ?\n");
+      return;
+    }
+
+  rc = mu_list_pop (list, (void**) &text);
+  if (rc)
+    fprintf (stderr, "mu_list_pop: %s\n", mu_strerror (rc));
+  else
+    printf ("%s\n", text);
+}
+  
+void
 help ()
 {
   printf ("count\n");
@@ -808,6 +844,8 @@ help ()
   printf ("help\n");
   printf ("head\n");
   printf ("tail\n");
+  printf ("push item\n");
+  printf ("pop\n");
   printf ("sort\n");
   printf ("NUMBER\n");
 }
@@ -928,6 +966,10 @@ shell (mu_list_t list)
 	    head (ws.ws_wordc, list);
 	  else if (strcmp (ws.ws_wordv[0], "tail") == 0)
 	    tail (ws.ws_wordc, list);
+	  else if (strcmp (ws.ws_wordv[0], "push") == 0)
+	    push (list, ws.ws_wordc, ws.ws_wordv);
+	  else if (strcmp (ws.ws_wordv[0], "pop") == 0)
+	    pop (list, ws.ws_wordc, ws.ws_wordv);
 	  else if (strcmp (ws.ws_wordv[0], "sort") == 0)
 	    {
 	      int i;