[notmuch] [PATCH 2/2] Added regress option to messages iterator

[meskio at sindominio.net]

From: Ruben Pollan <meskio at sindominio.net>

Added the functions notmuch_messages_regress and notmuch_messages_is_first to
notmuch library. With them is possible to iterate backwards on messages.

* notmuch_messages_regress do the opposite than notmuch_messages_advance,
  getting the messages iterator one position backwards.

* notmuch_messages_is_first return TRUE if the iterator is in the first
  message.
---
 lib/messages.c        |   27 +++++++++++++++++++++++++++
 lib/notmuch-private.h |    7 +++++++
 lib/notmuch.h         |    8 ++++++++
 lib/query.cc          |   24 ++++++++++++++++++++++++
 4 files changed, 66 insertions(+), 0 deletions(-)

diff --git a/lib/messages.c b/lib/messages.c
index 5414f87..2c28738 100644
--- a/lib/messages.c
+++ b/lib/messages.c
@@ -90,6 +90,7 @@ _notmuch_messages_create (notmuch_message_list_t *list)
 
     messages->is_of_list_type = TRUE;
     messages->iterator = list->head;
+    messages->previous_node = NULL;
 
     return messages;
 }
@@ -121,6 +122,18 @@ notmuch_messages_has_more (notmuch_messages_t *messages)
     return (messages->iterator != NULL);
 }
 
+notmuch_bool_t
+notmuch_messages_is_first (notmuch_messages_t *messages)
+{
+    if (messages == NULL)
+	return TRUE;
+
+    if (! messages->is_of_list_type)
+	return _notmuch_mset_messages_is_first (messages);
+
+    return (messages->previous_node == NULL);
+}
+
 notmuch_message_t *
 notmuch_messages_get (notmuch_messages_t *messages)
 {
@@ -142,10 +155,24 @@ notmuch_messages_advance (notmuch_messages_t *messages)
     if (messages->iterator == NULL)
 	return;
 
+    messages->previous_node = messages->iterator;
     messages->iterator = messages->iterator->next;
 }
 
 void
+notmuch_messages_regress (notmuch_messages_t *messages)
+{
+    if (! messages->is_of_list_type)
+	return _notmuch_mset_messages_regress (messages);
+
+    if (messages->previous_node == NULL)
+	return;
+
+    messages->iterator = messages->previous_node;
+    messages->previous_node = messages->iterator->prev;
+}
+
+void
 notmuch_messages_destroy (notmuch_messages_t *messages)
 {
     talloc_free (messages);
diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
index 133ed0e..5852c00 100644
--- a/lib/notmuch-private.h
+++ b/lib/notmuch-private.h
@@ -299,6 +299,7 @@ typedef struct _notmuch_message_list {
  */
 struct _notmuch_messages {
     notmuch_bool_t is_of_list_type;
+    notmuch_message_node_t *previous_node;
     notmuch_message_node_t *iterator;
 };
 
@@ -321,12 +322,18 @@ _notmuch_messages_create (notmuch_message_list_t *list);
 notmuch_bool_t
 _notmuch_mset_messages_has_more (notmuch_messages_t *messages);
 
+notmuch_bool_t
+_notmuch_mset_messages_is_first (notmuch_messages_t *messages);
+
 notmuch_message_t *
 _notmuch_mset_messages_get (notmuch_messages_t *messages);
 
 void
 _notmuch_mset_messages_advance (notmuch_messages_t *messages);
 
+void
+_notmuch_mset_messages_regress (notmuch_messages_t *messages);
+
 /* message.cc */
 
 void
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 60834fb..69bd98a 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -604,6 +604,10 @@ notmuch_thread_destroy (notmuch_thread_t *thread);
 notmuch_bool_t
 notmuch_messages_has_more (notmuch_messages_t *messages);
 
+/* Is the given notmuch_messages_t object on the first message */
+notmuch_bool_t
+notmuch_messages_is_first (notmuch_messages_t *messages);
+
 /* Get the current message from 'messages' as a notmuch_message_t.
  *
  * Note: The returned message belongs to 'messages' and has a lifetime
@@ -626,6 +630,10 @@ notmuch_messages_get (notmuch_messages_t *messages);
 void
 notmuch_messages_advance (notmuch_messages_t *messages);
 
+/* Regress the 'messages' iterator to the previous result. */
+void
+notmuch_messages_regress (notmuch_messages_t *messages);
+
 /* Destroy a notmuch_messages_t object.
  *
  * It's not strictly necessary to call this function. All memory from
diff --git a/lib/query.cc b/lib/query.cc
index 9106b92..94a6860 100644
--- a/lib/query.cc
+++ b/lib/query.cc
@@ -35,6 +35,7 @@ typedef struct _notmuch_mset_messages {
     notmuch_messages_t base;
     notmuch_database_t *notmuch;
     Xapian::MSetIterator iterator;
+    Xapian::MSetIterator iterator_begin;
     Xapian::MSetIterator iterator_end;
 } notmuch_mset_messages_t;
 
@@ -86,6 +87,7 @@ static int
 _notmuch_messages_destructor (notmuch_mset_messages_t *messages)
 {
     messages->iterator.~MSetIterator ();
+    messages->iterator_begin.~MSetIterator ();
     messages->iterator_end.~MSetIterator ();
 
     return 0;
@@ -108,6 +110,7 @@ notmuch_query_search_messages (notmuch_query_t *query)
 	messages->base.iterator = NULL;
 	messages->notmuch = notmuch;
 	new (&messages->iterator) Xapian::MSetIterator ();
+	new (&messages->iterator_begin) Xapian::MSetIterator ();
 	new (&messages->iterator_end) Xapian::MSetIterator ();
 
 	talloc_set_destructor (messages, _notmuch_messages_destructor);
@@ -155,6 +158,7 @@ notmuch_query_search_messages (notmuch_query_t *query)
 	mset = enquire.get_mset (0, notmuch->xapian_db->get_doccount ());
 
 	messages->iterator = mset.begin ();
+	messages->iterator_end = mset.begin ();
 	messages->iterator_end = mset.end ();
 
     } catch (const Xapian::Error &error) {
@@ -177,6 +181,16 @@ _notmuch_mset_messages_has_more (notmuch_messages_t *messages)
     return (mset_messages->iterator != mset_messages->iterator_end);
 }
 
+notmuch_bool_t
+_notmuch_mset_messages_is_first (notmuch_messages_t *messages)
+{
+    notmuch_mset_messages_t *mset_messages;
+
+    mset_messages = (notmuch_mset_messages_t *) messages;
+
+    return (mset_messages->iterator == mset_messages->iterator_begin);
+}
+
 notmuch_message_t *
 _notmuch_mset_messages_get (notmuch_messages_t *messages)
 {
@@ -215,6 +229,16 @@ _notmuch_mset_messages_advance (notmuch_messages_t *messages)
     mset_messages->iterator++;
 }
 
+void
+_notmuch_mset_messages_regress (notmuch_messages_t *messages)
+{
+    notmuch_mset_messages_t *mset_messages;
+
+    mset_messages = (notmuch_mset_messages_t *) messages;
+
+    mset_messages->iterator--;
+}
+
 /* Glib objects force use to use a talloc destructor as well, (but not
  * nearly as ugly as the for messages due to C++ objects). At
  * this point, I'd really like to have some talloc-friendly
-- 
1.6.5.4