Implement editheader sieve extension (RFC 5293).

Also fix iterator synchronization after removing an element and
improve Sieve API.

* include/mailutils/header.h (mu_header_get_itemptr): New proto.
* include/mailutils/iterator.h (mu_iterator_advance): Remove.
(mu_iterator_delitem): New proto.
(mu_iterator_set_delitem): New proto.
* include/mailutils/sieve.h (mu_sieve_register_t) <opt_args>: New member.
(mu_sieve_register_test_ext)
(mu_sieve_register_action_ext): New protos.
* include/mailutils/sys/iterator.h (_mu_iterator) <curitem_p>: Remove.
<delitem>: New member. All uses updated.

* libmailutils/base/iterator.c (mu_iterator_set_delitem): New function.

* libmailutils/mailbox/hdritr.c: Implement bidirectional iteration.
Implement itrctl method.
* libmailutils/mailbox/header.c: Likewise.

* libmailutils/base/assoc.c: Use delitem method instead of curitem_p.
(mu_iterator_delitem): New function.
* libmailutils/base/opool.c
* libmailutils/diag/debug.c
* libmailutils/list/iterator.c
* libmailutils/list/pop.c
* libmailutils/list/remove.c
* libmailutils/list/removenth.c
* libmailutils/mailbox/imapenv.c
* libmailutils/mailbox/mbxitr.c
* libproto/pop/pop3_iterator.c

* libmu_sieve/extensions/Makefile.am: Add editheader.c
* libmu_sieve/extensions/editheader.c: New file.

* libmu_sieve/prog.c (mu_sv_code_command): Allow for optional positional
arguments.
* libmu_sieve/register.c (mu_sieve_test_lookup)
(mu_sieve_action_lookup): Return NULL if a record with
empty (NULL) handler is found.
(mu_sieve_register_test_ext)
(mu_sieve_register_action_ext): New functions.
(mu_sieve_register_test)
(mu_sieve_register_action): Rewrite as wrappers to the above.
* libmu_sieve/util.c (mu_sieve_vlist_do): Allow for SVT_STRING
argument.
* sieve/tests/Makefile.am: Add new testcases.
* sieve/tests/testsuite.at: Include new testcases.
* sieve/tests/addheader.at: New testcase.
* sieve/tests/delheader.at: New testcase.

* NEWS: Update.
* doc/rfc/README: Update.

28 files changed, 870 insertions, 80 deletions

diff --git a/NEWS b/NEWS
index ac7dbdf00..94cc1b71f 100644
--- a/NEWS
+++ b/NEWS
@@ -1,4 +1,4 @@
-GNU mailutils NEWS -- history of user-visible changes. 2012-08-07
+GNU mailutils NEWS -- history of user-visible changes. 2012-11-12
 Copyright (C) 2002-2012 Free Software Foundation, Inc.
 See the end of file for copying conditions.
 
@@ -114,6 +114,10 @@ header field with the given date.
 
 See <http://mailutils.org/wiki/Timestamp_(Sieve_test)>.
 
+Implemented the Editheader extension: `addheader' and `delheader' actions.
+
+See <http://tools.ietf.org/html/rfc5293>.
+
 ** mail: sending attachments
 
 The mail[x] utility now allows for sending attachments.  Any number of
diff --git a/doc/rfc/README b/doc/rfc/README
index 38d0abbef..593ec69b0 100644
--- a/doc/rfc/README
+++ b/doc/rfc/README
@@ -53,3 +53,4 @@ the actual RFC number.
 3501	INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
 3691	Internet Message Access Protocol (IMAP) UNSELECT command
 4314	IMAP4 Access Control List (ACL) Extension
+5293	Sieve Email Filtering: Editheader Extension
diff --git a/include/mailutils/header.h b/include/mailutils/header.h
index 8e50cb601..079f679d9 100644
--- a/include/mailutils/header.h
+++ b/include/mailutils/header.h
@@ -169,6 +169,8 @@ extern int mu_header_set_fill (mu_header_t,
 			       int (*_fill) (void *data, char **, size_t *),
 			       void *data);
 
+extern int mu_header_get_itemptr (mu_header_t header, size_t num,
+				  const void **sptr);
   
 #ifdef __cplusplus
 }
diff --git a/include/mailutils/iterator.h b/include/mailutils/iterator.h
index 84d469f96..867f77537 100644
--- a/include/mailutils/iterator.h
+++ b/include/mailutils/iterator.h
@@ -37,7 +37,7 @@ enum mu_itrctl_req
     mu_itrctl_qry_direction, /* Query iteration direction */
     mu_itrctl_set_direction  /* Set iteration direction */
   };
-  
+
 extern int mu_iterator_create   (mu_iterator_t *, void *);
 extern int mu_iterator_dup      (mu_iterator_t *piterator, mu_iterator_t orig);
 extern void mu_iterator_destroy (mu_iterator_t *);
@@ -53,7 +53,7 @@ extern int mu_iterator_ctl (mu_iterator_t, enum mu_itrctl_req, void *);
   
 extern int mu_iterator_attach (mu_iterator_t *root, mu_iterator_t iterator);
 extern int mu_iterator_detach (mu_iterator_t *root, mu_iterator_t iterator);
-extern void mu_iterator_advance (mu_iterator_t iterator, void *e);
+extern void mu_iterator_delitem (mu_iterator_t iterator, void *e);
   
 extern int mu_iterator_set_first (mu_iterator_t, int (*first) (void *));  
 extern int mu_iterator_set_next (mu_iterator_t, int (*next) (void *));  
@@ -66,8 +66,13 @@ extern int mu_iterator_set_dup (mu_iterator_t itr,
 			     int (*dup) (void **ptr, void *data));
 extern int mu_iterator_set_destroy (mu_iterator_t itr,
 				 int (*destroy) (mu_iterator_t, void *data));
-extern int mu_iterator_set_curitem_p (mu_iterator_t itr,
-				   int (*curitem_p) (void *, void *));
+
+#define MU_ITR_DELITEM_NOTHING 0  
+#define MU_ITR_DELITEM_NEXT    1
+#define MU_ITR_DELITEM_ADVANCE 2  
+  
+extern int mu_iterator_set_delitem (mu_iterator_t itr,
+				    int (*delitem) (void *, void *));
 extern int mu_iterator_set_itrctl (mu_iterator_t itr,
 				   int (*itrctl) (void *,
 						  enum mu_itrctl_req,
diff --git a/include/mailutils/sieve.h b/include/mailutils/sieve.h
index f9ef9dbf6..ffe5db347 100644
--- a/include/mailutils/sieve.h
+++ b/include/mailutils/sieve.h
@@ -100,6 +100,7 @@ typedef struct
   int required;
   mu_sieve_handler_t handler;
   mu_sieve_data_type *req_args;
+  mu_sieve_data_type *opt_args;
   mu_sieve_tag_group_t *tags;
 } mu_sieve_register_t;
 
@@ -146,10 +147,21 @@ mu_sieve_register_t *mu_sieve_test_lookup (mu_sieve_machine_t mach,
 					   const char *name);
 mu_sieve_register_t *mu_sieve_action_lookup (mu_sieve_machine_t mach,
 					     const char *name);
+int mu_sieve_register_test_ext (mu_sieve_machine_t mach,
+				const char *name, mu_sieve_handler_t handler,
+				mu_sieve_data_type *req_args,
+				mu_sieve_data_type *opt_args,
+				mu_sieve_tag_group_t *tags, int required);
 int mu_sieve_register_test (mu_sieve_machine_t mach,
 			    const char *name, mu_sieve_handler_t handler,
 			    mu_sieve_data_type * arg_types,
 			    mu_sieve_tag_group_t * tags, int required);
+
+int mu_sieve_register_action_ext (mu_sieve_machine_t mach,
+				  const char *name, mu_sieve_handler_t handler,
+				  mu_sieve_data_type *req_args,
+				  mu_sieve_data_type *opt_args,
+				  mu_sieve_tag_group_t *tags, int required);
 int mu_sieve_register_action (mu_sieve_machine_t mach,
 			      const char *name, mu_sieve_handler_t handler,
 			      mu_sieve_data_type * arg_types,
diff --git a/include/mailutils/sys/iterator.h b/include/mailutils/sys/iterator.h
index 73a4926f5..7f007afe3 100644
--- a/include/mailutils/sys/iterator.h
+++ b/include/mailutils/sys/iterator.h
@@ -36,7 +36,7 @@ struct _mu_iterator
   int (*first) (void *owner);
   int (*next) (void *owner);
   int (*getitem) (void *owner, void **pret, const void **pkey);
-  int (*curitem_p) (void *owner, void *item);
+  int (*delitem) (void *owner, void *item);
   int (*finished_p) (void *owner);
   int (*itrctl) (void *owner, enum mu_itrctl_req req, void *arg);
   void *(*dataptr) (void *);
diff --git a/libmailutils/base/assoc.c b/libmailutils/base/assoc.c
index c34b6af0f..ecef8a320 100644
--- a/libmailutils/base/assoc.c
+++ b/libmailutils/base/assoc.c
@@ -452,13 +452,13 @@ destroy (mu_iterator_t iterator, void *data)
 }
 
 static int
-curitem_p (void *owner, void *item)
+delitem (void *owner, void *item)
 {
   struct assoc_iterator *itr = owner;
   mu_assoc_t assoc = itr->assoc;
   struct _mu_assoc_elem *elem = ASSOC_ELEM (assoc, itr->index);
   
-  return elem == item;
+  return elem == item ? MU_ITR_DELITEM_NEXT : MU_ITR_DELITEM_NOTHING;
 }
 
 static int
@@ -498,7 +498,7 @@ mu_assoc_get_iterator (mu_assoc_t assoc, mu_iterator_t *piterator)
   mu_iterator_set_next (iterator, next);
   mu_iterator_set_getitem (iterator, getitem);
   mu_iterator_set_finished_p (iterator, finished_p);
-  mu_iterator_set_curitem_p (iterator, curitem_p);
+  mu_iterator_set_delitem (iterator, delitem);
   mu_iterator_set_destroy (iterator, destroy);
   mu_iterator_set_dup (iterator, assoc_data_dup);
   
diff --git a/libmailutils/base/iterator.c b/libmailutils/base/iterator.c
index 8e88c68ca..118de726b 100644
--- a/libmailutils/base/iterator.c
+++ b/libmailutils/base/iterator.c
@@ -81,12 +81,12 @@ mu_iterator_set_finished_p (mu_iterator_t itr, int (*finished_p) (void *))
 }
 
 int
-mu_iterator_set_curitem_p (mu_iterator_t itr,
-			int (*curitem_p) (void *, void *))
+mu_iterator_set_delitem (mu_iterator_t itr,
+			 int (*delitem) (void *, void *))
 {
   if (!itr)
     return EINVAL;
-  itr->curitem_p = curitem_p;
+  itr->delitem = delitem;
   return 0;
 }
 
@@ -158,7 +158,7 @@ mu_iterator_dup (mu_iterator_t *piterator, mu_iterator_t orig)
   iterator->first = orig->first;
   iterator->next = orig->next;
   iterator->getitem = orig->getitem;
-  iterator->curitem_p = orig->curitem_p;
+  iterator->delitem = orig->delitem;
   iterator->finished_p = orig->finished_p;
   iterator->itrctl = orig->itrctl;
   
@@ -250,14 +250,19 @@ iterator_get_owner (mu_iterator_t iterator, void **powner)
 }
 
 void
-mu_iterator_advance (mu_iterator_t iterator, void *e)
+mu_iterator_delitem (mu_iterator_t iterator, void *itm)
 {
   for (; iterator; iterator = iterator->next_itr)
     {
-      if (iterator->curitem_p (iterator->owner, e))
+      if (iterator->delitem)
 	{
-	  iterator->next (iterator->owner);
-	  iterator->is_advanced++;
+	  switch (iterator->delitem (iterator->owner, itm))
+	    {
+	    case MU_ITR_DELITEM_NEXT:
+	      iterator->next (iterator->owner);
+	    case MU_ITR_DELITEM_ADVANCE:
+	      iterator->is_advanced++;
+	    }
 	}
     }
 }
diff --git a/libmailutils/base/opool.c b/libmailutils/base/opool.c
index 51c8e91e0..00a65824b 100644
--- a/libmailutils/base/opool.c
+++ b/libmailutils/base/opool.c
@@ -384,10 +384,11 @@ opitr_finished_p (void *owner)
 }
 
 static int
-opitr_curitem_p (void *owner, void *item)
+opitr_delitem (void *owner, void *item)
 {
   struct opool_iterator *itr = owner;
-  return itr->cur && itr->cur->buf == item;
+  return (itr->cur && itr->cur->buf == item) ? 
+     MU_ITR_DELITEM_NEXT : MU_ITR_DELITEM_NOTHING;
 }
 
 static int
@@ -446,7 +447,7 @@ mu_opool_get_iterator (mu_opool_t opool, mu_iterator_t *piterator)
   mu_iterator_set_next (iterator, opitr_next);
   mu_iterator_set_getitem (iterator, opitr_getitem);
   mu_iterator_set_finished_p (iterator, opitr_finished_p);
-  mu_iterator_set_curitem_p (iterator, opitr_curitem_p);
+  mu_iterator_set_delitem (iterator, opitr_delitem);
   mu_iterator_set_destroy (iterator, opitr_destroy);
   mu_iterator_set_dup (iterator, opitr_data_dup);
 
diff --git a/libmailutils/diag/debug.c b/libmailutils/diag/debug.c
index 897062cfe..d9b5178b8 100644
--- a/libmailutils/diag/debug.c
+++ b/libmailutils/diag/debug.c
@@ -572,10 +572,11 @@ finished_p (void *owner)
 }
 
 static int
-curitem_p (void *owner, void *item)
+delitem (void *owner, void *item)
 {
   struct debug_iterator *itr = owner;
-  return mu_c_strcasecmp (cattab[itr->pos].name, (char *) item) == 0;
+  return mu_c_strcasecmp (cattab[itr->pos].name, (char *) item) == 0 ?
+     MU_ITR_DELITEM_NEXT : MU_ITR_DELITEM_NOTHING;
 }
 
 static int
@@ -659,7 +660,7 @@ mu_debug_get_iterator (mu_iterator_t *piterator, int skipunset)
   mu_iterator_set_next (iterator, next);
   mu_iterator_set_getitem (iterator, getitem);
   mu_iterator_set_finished_p (iterator, finished_p);
-  mu_iterator_set_curitem_p (iterator, curitem_p);
+  mu_iterator_set_delitem (iterator, delitem);
   mu_iterator_set_dup (iterator, list_data_dup);
   mu_iterator_set_itrctl (iterator, list_itrctl);
   
diff --git a/libmailutils/list/iterator.c b/libmailutils/list/iterator.c
index 26cc364e0..f517a8093 100644
--- a/libmailutils/list/iterator.c
+++ b/libmailutils/list/iterator.c
@@ -84,10 +84,10 @@ destroy (mu_iterator_t iterator, void *data)
 }
 
 static int
-curitem_p (void *owner, void *item)
+delitem (void *owner, void *item)
 {
   struct list_iterator *itr = owner;
-  return itr->cur == item;
+  return itr->cur == item ? MU_ITR_DELITEM_NEXT : MU_ITR_DELITEM_NOTHING;
 }
 
 static int
@@ -142,7 +142,7 @@ list_itrctl (void *owner, enum mu_itrctl_req req, void *arg)
 	  ptr = itr->cur;
 	  prev = ptr->prev;
 	
-	  mu_iterator_advance (list->itr, ptr);
+	  mu_iterator_delitem (list->itr, ptr);
 	  prev->next = ptr->next;
 	  ptr->next->prev = prev;
 	  if (req == mu_itrctl_delete)
@@ -238,7 +238,7 @@ mu_list_get_iterator (mu_list_t list, mu_iterator_t *piterator)
   mu_iterator_set_next (iterator, next);
   mu_iterator_set_getitem (iterator, getitem);
   mu_iterator_set_finished_p (iterator, finished_p);
-  mu_iterator_set_curitem_p (iterator, curitem_p);
+  mu_iterator_set_delitem (iterator, delitem);
   mu_iterator_set_destroy (iterator, destroy);
   mu_iterator_set_dup (iterator, list_data_dup);
   mu_iterator_set_itrctl (iterator, list_itrctl);
diff --git a/libmailutils/list/pop.c b/libmailutils/list/pop.c
index c25c2aed8..6a504eb73 100644
--- a/libmailutils/list/pop.c
+++ b/libmailutils/list/pop.c
@@ -35,7 +35,7 @@ mu_list_pop (mu_list_t list, void **item)
 
   last = list->head.prev;
   prev = last->prev;
-  mu_iterator_advance (list->itr, last);
+  mu_iterator_delitem (list->itr, last);
   prev->next = last->next;
   prev->next->prev = prev;
   if (item)
diff --git a/libmailutils/list/remove.c b/libmailutils/list/remove.c
index 5ebd31235..f56340390 100644
--- a/libmailutils/list/remove.c
+++ b/libmailutils/list/remove.c
@@ -41,7 +41,7 @@ mu_list_remove (mu_list_t list, void *item)
 	{
 	  struct list_data *previous = current->prev;
 	  
-	  mu_iterator_advance (list->itr, current);
+	  mu_iterator_delitem (list->itr, current);
 	  previous->next = current->next;
 	  current->next->prev = previous;
 	  DESTROY_ITEM (list, current);
diff --git a/libmailutils/list/removenth.c b/libmailutils/list/removenth.c
index 80550eeb7..f589b51e1 100644
--- a/libmailutils/list/removenth.c
+++ b/libmailutils/list/removenth.c
@@ -26,7 +26,6 @@ int
 mu_list_remove_nth (mu_list_t list, size_t n)
 {
   struct list_data *current;
-  mu_list_comparator_t comp;
   int status = MU_ERR_NOENT;
   size_t i;
     
@@ -42,7 +41,7 @@ mu_list_remove_nth (mu_list_t list, size_t n)
 	{
 	  struct list_data *previous = current->prev;
 	  
-	  mu_iterator_advance (list->itr, current);
+	  mu_iterator_delitem (list->itr, current);
 	  previous->next = current->next;
 	  current->next->prev = previous;
 	  DESTROY_ITEM (list, current);
diff --git a/libmailutils/mailbox/hdritr.c b/libmailutils/mailbox/hdritr.c
index a2504d5fb..d516b7259 100644
--- a/libmailutils/mailbox/hdritr.c
+++ b/libmailutils/mailbox/hdritr.c
@@ -30,13 +30,20 @@ struct header_iterator
 {
   mu_header_t header;
   size_t index;
+  int backwards;
 };
 
 static int
 hdr_first (void *owner)
 {
   struct header_iterator *itr = owner;
-  itr->index = 1;
+  if (itr->backwards)
+    {
+      if (mu_header_get_field_count (itr->header, &itr->index))
+	return 1;
+    }
+  else
+    itr->index = 1;
   return 0;
 }
 
@@ -44,7 +51,13 @@ static int
 hdr_next (void *owner)
 {
   struct header_iterator *itr = owner;
-  itr->index++;
+  if (itr->backwards)
+    {
+      if (itr->index != 0)
+	itr->index--;
+    }
+  else
+    itr->index++;
   return 0;
 }
 
@@ -58,16 +71,16 @@ hdr_getitem (void *owner, void **pret, const void **pkey)
   rc = mu_header_get_field_count (itr->header, &count);
   if (rc)
     return rc;
-  if (itr->index > count)
+  if (itr->index < 1 || itr->index > count)
     return MU_ERR_NOENT;
   
-  rc = mu_header_sget_field_name (itr->header, itr->index,
-				  (const char**) pkey);
+  rc = mu_header_sget_field_value (itr->header, itr->index,
+				   (const char**) pret);
   if (rc == 0)
     {
       if (pkey)
-	rc = mu_header_sget_field_value (itr->header, itr->index,
-					 (const char**) pret);
+	rc = mu_header_sget_field_name (itr->header, itr->index,
+					(const char**) pkey);
     }
   return rc;
 }
@@ -78,6 +91,9 @@ hdr_finished_p (void *owner)
   struct header_iterator *itr = owner;
   size_t count;
 
+  if (itr->backwards)
+    return itr->index < 1;
+
   if (mu_header_get_field_count (itr->header, &count))
     return 1;
   return itr->index > count;
@@ -93,13 +109,16 @@ hdr_destroy (mu_iterator_t iterator, void *data)
 }
 
 static int
-hdr_curitem_p (void *owner, void *item)
+hdr_delitem (void *owner, void *item)
 {
-  void *ptr;
+  struct header_iterator *itr = owner;
+  const void *ptr;
 
-  if (hdr_getitem (owner, &ptr, NULL))
-    return 0;
-  return ptr == item;
+  if (mu_header_get_itemptr (itr->header, itr->index, &ptr))
+    return MU_ITR_DELITEM_NOTHING;
+  if (ptr == item && !itr->backwards)
+    return MU_ITR_DELITEM_ADVANCE;
+  return MU_ITR_DELITEM_NOTHING;
 }
 
 static int
@@ -115,6 +134,51 @@ hdr_data_dup (void **ptr, void *owner)
   return 0;
 }
 
+static int
+hdr_itrctl (void *owner, enum mu_itrctl_req req, void *arg)
+{
+  struct header_iterator *itr = owner;
+
+  switch (req)
+    {
+    case mu_itrctl_tell:
+      /* Return current position in the object */
+      if (hdr_finished_p (owner))
+	return MU_ERR_NOENT;
+      else
+	*(size_t*)arg = itr->index;
+      return 0;
+      break;
+      
+    case mu_itrctl_delete:
+      /* Delete current element */
+      if (hdr_finished_p (owner))
+	return MU_ERR_NOENT;
+      else
+	return mu_header_remove (itr->header, NULL, itr->index);
+      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;
+    }
+  return 0;
+}
+  
+
 int
 mu_header_get_iterator (mu_header_t hdr, mu_iterator_t *piterator)
 {
@@ -142,9 +206,10 @@ mu_header_get_iterator (mu_header_t hdr, mu_iterator_t *piterator)
   mu_iterator_set_next (iterator, hdr_next);
   mu_iterator_set_getitem (iterator, hdr_getitem);
   mu_iterator_set_finished_p (iterator, hdr_finished_p);
-  mu_iterator_set_curitem_p (iterator, hdr_curitem_p);
+  mu_iterator_set_delitem (iterator, hdr_delitem);
   mu_iterator_set_destroy (iterator, hdr_destroy);
   mu_iterator_set_dup (iterator, hdr_data_dup);
+  mu_iterator_set_itrctl (iterator, hdr_itrctl);
 
   mu_iterator_attach (&hdr->itr, iterator);
 
diff --git a/libmailutils/mailbox/header.c b/libmailutils/mailbox/header.c
index 1c7642183..2745963b9 100644
--- a/libmailutils/mailbox/header.c
+++ b/libmailutils/mailbox/header.c
@@ -80,13 +80,15 @@ mu_hdrent_find (struct _mu_header *hdr, const char *name, int pos)
   if (pos > 0)
     {
       for (p = hdr->head; p; p = p->next)
-	if (mu_c_strcasecmp (MU_HDRENT_NAME (hdr,p), name) == 0 && pos-- == 1)
+	if ((!name || mu_c_strcasecmp (MU_HDRENT_NAME (hdr,p), name) == 0) &&
+	    pos-- == 1)
 	  break;
     }
   else if (pos < 0)
     {
       for (p = hdr->tail; p; p = p->prev)
-	if (mu_c_strcasecmp (MU_HDRENT_NAME (hdr,p), name) == 0 && ++pos == 0)
+	if ((!name || mu_c_strcasecmp (MU_HDRENT_NAME (hdr,p), name) == 0) &&
+	    ++pos == 0)
 	  break;
     }
   else
@@ -544,7 +546,7 @@ mu_header_remove (mu_header_t header, const char *fn, int n)
   int status;
   struct mu_hdrent *ent;
   
-  if (header == NULL || fn == NULL)
+  if (header == NULL)
     return EINVAL;
 
   status = mu_header_fill (header);
@@ -555,6 +557,7 @@ mu_header_remove (mu_header_t header, const char *fn, int n)
   if (!ent)
     return MU_ERR_NOENT;
 
+  mu_iterator_delitem (header->itr, ent);
   mu_hdrent_remove (header, ent);
   HEADER_SET_MODIFIED (header);
   free (ent);
@@ -782,6 +785,26 @@ mu_header_get_field_count (mu_header_t header, size_t *pcount)
 }
 
 int
+mu_header_get_itemptr (mu_header_t header, size_t num, const void **sptr)
+{
+  int status;
+  
+  if (header == NULL)
+    return EINVAL;
+
+  status = mu_header_fill (header);
+  if (status == 0)
+    {
+      struct mu_hdrent *ent = mu_hdrent_nth (header, num);
+      if (ent)
+	*sptr = ent;
+      else
+	status = MU_ERR_NOENT;
+    }
+  return status;
+}
+
+int
 mu_header_sget_field_name (mu_header_t header, size_t num, const char **sptr)
 {
   int status;
diff --git a/libmailutils/mailbox/imapenv.c b/libmailutils/mailbox/imapenv.c
index 847a6f762..aa8a865af 100644
--- a/libmailutils/mailbox/imapenv.c
+++ b/libmailutils/mailbox/imapenv.c
@@ -52,7 +52,7 @@ mu_message_get_imapenvelope (mu_message_t msg, struct mu_imapenvelope **pimapenv
   
   if (msg == NULL)
     return EINVAL;
-  if (imapenvelope == NULL)
+  if (pimapenvelope == NULL)
     return MU_ERR_OUT_PTR_NULL;
   if (msg->_imapenvelope)
     return msg->_imapenvelope (msg, pimapenvelope);
diff --git a/libmailutils/mailbox/mbxitr.c b/libmailutils/mailbox/mbxitr.c
index 72c7a7dfb..0ea8856aa 100644
--- a/libmailutils/mailbox/mbxitr.c
+++ b/libmailutils/mailbox/mbxitr.c
@@ -111,13 +111,14 @@ mbx_destroy (mu_iterator_t iterator, void *data)
 }
 
 static int
-mbx_curitem_p (void *owner, void *item)
+mbx_delitem (void *owner, void *item)
 {
   void *ptr;
 
   if (mbx_getitem (owner, &ptr, NULL))
     return 0;
-  return ptr == item;/* FIXME: Is it ok? */
+  return ptr == item ? MU_ITR_DELITEM_NEXT : MU_ITR_DELITEM_NOTHING;
+  /* FIXME: is it ok? */
 }
 
 static int
@@ -210,7 +211,7 @@ mu_mailbox_get_iterator (mu_mailbox_t mbx, mu_iterator_t *piterator)
   mu_iterator_set_next (iterator, mbx_next);
   mu_iterator_set_getitem (iterator, mbx_getitem);
   mu_iterator_set_finished_p (iterator, mbx_finished_p);
-  mu_iterator_set_curitem_p (iterator, mbx_curitem_p);
+  mu_iterator_set_delitem (iterator, mbx_delitem);
   mu_iterator_set_destroy (iterator, mbx_destroy);
   mu_iterator_set_dup (iterator, mbx_data_dup);
   mu_iterator_set_itrctl (iterator, mbx_itrctl);
diff --git a/libmu_sieve/extensions/Makefile.am b/libmu_sieve/extensions/Makefile.am
index 9ac82b175..d538ca6b1 100644
--- a/libmu_sieve/extensions/Makefile.am
+++ b/libmu_sieve/extensions/Makefile.am
@@ -16,6 +16,7 @@
 
 moddir=@MU_SIEVE_MODDIR@
 mod_LTLIBRARIES = \
+ editheader.la\
  list.la\
  moderator.la\
  pipe.la\
diff --git a/libmu_sieve/extensions/editheader.c b/libmu_sieve/extensions/editheader.c
new file mode 100644
index 000000000..89ae6ea43
--- /dev/null
+++ b/libmu_sieve/extensions/editheader.c
@@ -0,0 +1,339 @@
+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 2012 Free Software Foundation, Inc.
+
+   GNU Mailutils 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, or (at your option)
+   any later version.
+
+   GNU Mailutils 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 GNU Mailutils.  If not, see
+   <http://www.gnu.org/licenses/>. */
+
+/* This module implements the Editheader Extension (RFC 5293) */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif  
+
+#include <mailutils/types.h>
+#include <mailutils/message.h>
+#include <mailutils/header.h>
+#include <mailutils/error.h>
+#include <mailutils/errno.h>
+#include <mailutils/sieve.h>
+
+/* Syntax: addheader [:last] <field-name: string> <value: string>
+ */
+int
+sieve_addheader (mu_sieve_machine_t mach, mu_list_t args, mu_list_t tags)
+{
+  mu_sieve_value_t *val;
+  const char *field_name;
+  const char *field_value;
+  mu_message_t msg;
+  mu_header_t hdr;
+  int rc;
+  
+  val = mu_sieve_value_get (args, 0);
+  if (!val)
+    {
+      mu_sieve_error (mach, "%lu: %s",
+		      (unsigned long) mu_sieve_get_message_num (mach),
+		      _("cannot get field name"));
+      mu_sieve_abort (mach);
+    }
+  field_name = val->v.string;
+
+  val = mu_sieve_value_get (args, 1);
+  if (!val)
+    {
+      mu_sieve_error (mach, "%lu: %s",
+		      (unsigned long) mu_sieve_get_message_num (mach),
+		      _("cannot get field value"));
+      mu_sieve_abort (mach);
+    }
+  field_value = val->v.string;
+
+  mu_sieve_log_action (mach, "ADDHEADER", "%s: %s", field_name, field_value);
+
+  if (mu_sieve_is_dry_run (mach))
+    return 0;
+
+  msg = mu_sieve_get_message (mach);
+  rc = mu_message_get_header (msg, &hdr);
+  if (rc)
+    {
+      mu_sieve_error (mach, "%lu: %s: %s",
+		      (unsigned long) mu_sieve_get_message_num (mach),
+		      _("cannot get message header"),
+		      mu_strerror (rc));
+      mu_sieve_abort (mach);
+    }
+
+  rc = (mu_sieve_tag_lookup (tags, "last", NULL) ?
+	mu_header_append : mu_header_prepend) (hdr, field_name, field_value);
+  if (rc)
+    {
+      mu_sieve_error (mach, "%lu: %s: %s",
+		      (unsigned long) mu_sieve_get_message_num (mach),
+		      _("cannot append message header"),
+		      mu_strerror (rc));
+      mu_sieve_abort (mach);
+    }
+  return 0;
+}
+
+/* Syntax: deleteheader [:index <fieldno: number> [:last]]
+                        [COMPARATOR] [MATCH-TYPE]
+                        <field-name: string>
+                        [<value-patterns: string-list>]
+ */
+int
+sieve_deleteheader (mu_sieve_machine_t mach, mu_list_t args, mu_list_t tags)
+{
+  mu_sieve_value_t *val;
+  const char *field_name;
+  const char *field_pattern;
+  mu_message_t msg;
+  mu_header_t hdr;
+  int rc;
+  mu_sieve_comparator_t comp;
+  mu_iterator_t itr;
+  unsigned long i, idx = 0;
+  
+  val = mu_sieve_value_get (args, 0);
+  if (!val)
+    {
+      mu_sieve_error (mach, "%lu: %s",
+		      (unsigned long) mu_sieve_get_message_num (mach),
+		      _("cannot get field name"));
+      mu_sieve_abort (mach);
+    }
+  field_name = val->v.string;
+
+  val = mu_sieve_value_get (args, 1);
+  if (!val)
+    {
+      field_pattern = NULL;
+      mu_sieve_log_action (mach, "DELETEHEADER", "%s", field_name);
+    }
+  else
+    {
+      switch (val->type)
+	{
+	case SVT_STRING_LIST:
+	  if (mu_list_get (val->v.list, 0, (void**)&field_pattern))