lib: Move notmuch_messages_t code from query.cc to new messages.c

The new object is simply a linked-list of notmuch_message_t objects,
(unlike the old object which contained a couple of Xapian iterators).
This works now by the query code immediately iterator over all results
and creating notmuch_message_t objects for them, (rather than waiting
to create the objects until the notmuch_messages_get call as we did
earlier).

The point of this change is to allow other instances of lists of
messages, (such as in notmuch_thread_t), that are not directly related
to Xapian search results.

4 files changed, 123 insertions, 66 deletions

diff --git a/lib/Makefile.local b/lib/Makefile.local
index b8286c94..79f7b0b7 100644
--- a/lib/Makefile.local
+++ b/lib/Makefile.local
@@ -4,6 +4,7 @@ extra_cflags += -I$(dir)
 libnotmuch_c_srcs =		\
 	$(dir)/libsha1.c	\
 	$(dir)/message-file.c	\
+	$(dir)/messages.c	\
 	$(dir)/sha1.c		\
 	$(dir)/tags.c		\
 	$(dir)/xutil.c
diff --git a/lib/messages.c b/lib/messages.c
new file mode 100644
index 00000000..8b627750
--- /dev/null
+++ b/lib/messages.c
@@ -0,0 +1,97 @@
+/* messages.c - Iterator for a set of messages
+ *
+ * Copyright © 2009 Carl Worth
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see http://www.gnu.org/licenses/ .
+ *
+ * Author: Carl Worth <cworth@cworth.org>
+ */
+
+#include "notmuch-private.h"
+
+#include <glib.h> /* GList */
+
+typedef struct _message_list {
+    notmuch_message_t *message;
+    struct _message_list *next;
+} message_list_t;
+
+struct _notmuch_messages {
+    message_list_t *head;
+    message_list_t **tail;
+};
+
+/* Create a new notmuch_messages_t object, with 'ctx' as its talloc owner.
+ *
+ * This function can return NULL in case of out-of-memory.
+ */
+notmuch_messages_t *
+_notmuch_messages_create (void *ctx)
+{
+    notmuch_messages_t *messages;
+
+    messages = talloc (ctx, notmuch_messages_t);
+    if (unlikely (messages == NULL))
+	return NULL;
+
+    messages->head = NULL;
+    messages->tail = &messages->head;
+
+    return messages;
+}
+
+/* Add a new message to 'messages'.
+ */
+void
+_notmuch_messages_add_message (notmuch_messages_t *messages,
+			       notmuch_message_t *message)
+{
+    message_list_t *new = talloc (messages, message_list_t);
+
+    new->message = message;
+    new->next = NULL;
+
+    *(messages->tail) = new;
+    messages->tail = &new->next;
+}
+
+notmuch_bool_t
+notmuch_messages_has_more (notmuch_messages_t *messages)
+{
+    return messages->head != NULL;
+}
+
+notmuch_message_t *
+notmuch_messages_get (notmuch_messages_t *messages)
+{
+    if (messages->head == NULL)
+	return NULL;
+
+    return messages->head->message;
+}
+
+void
+notmuch_messages_advance (notmuch_messages_t *messages)
+{
+    if (messages->head == NULL)
+	return;
+
+    messages->head = messages->head->next;
+}
+
+void
+notmuch_messages_destroy (notmuch_messages_t *messages)
+{
+    talloc_free (messages);
+}
diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
index c286aa4b..bb1f235e 100644
--- a/lib/notmuch-private.h
+++ b/lib/notmuch-private.h
@@ -275,6 +275,15 @@ const char *
 notmuch_message_file_get_header (notmuch_message_file_t *message,
 				 const char *header);
 
+/* messages.c */
+
+notmuch_messages_t *
+_notmuch_messages_create (void *ctx);
+
+void
+_notmuch_messages_add_message (notmuch_messages_t *messages,
+			       notmuch_message_t *message);
+
 /* date.c */
 
 /* Parse an RFC 8222 date string to a time_t value.
diff --git a/lib/query.cc b/lib/query.cc
index 7c1df90c..d499a219 100644
--- a/lib/query.cc
+++ b/lib/query.cc
@@ -72,21 +72,6 @@ notmuch_query_set_sort (notmuch_query_t *query, notmuch_sort_t sort)
     query->sort = sort;
 }
 
-/* We end up having to call the destructors explicitly because we had
- * to use "placement new" in order to initialize C++ objects within a
- * block that we allocated with talloc. So C++ is making talloc
- * slightly less simple to use, (we wouldn't need
- * talloc_set_destructor at all otherwise).
- */
-static int
-_notmuch_messages_destructor (notmuch_messages_t *messages)
-{
-    messages->iterator.~MSetIterator ();
-    messages->iterator_end.~MSetIterator ();
-
-    return 0;
-}
-
 notmuch_messages_t *
 notmuch_query_search_messages (notmuch_query_t *query,
 			       int first,
@@ -95,8 +80,9 @@ notmuch_query_search_messages (notmuch_query_t *query,
     notmuch_database_t *notmuch = query->notmuch;
     const char *query_string = query->query_string;
     notmuch_messages_t *messages;
+    Xapian::MSetIterator i;
 
-    messages = talloc (query, notmuch_messages_t);
+    messages = _notmuch_messages_create (query);
     if (unlikely (messages == NULL))
 	return NULL;
 
@@ -144,15 +130,22 @@ notmuch_query_search_messages (notmuch_query_t *query,
 	    max_messages = notmuch->xapian_db->get_doccount ();
 	mset = enquire.get_mset (first, max_messages);
 
-	messages->notmuch = notmuch;
+	for (i = mset.begin (); i != mset.end (); i++) {
+	    notmuch_message_t *message;
+	    notmuch_private_status_t status;
 
-	new (&messages->iterator) Xapian::MSetIterator ();
-	new (&messages->iterator_end) Xapian::MSetIterator ();
-
-	talloc_set_destructor (messages, _notmuch_messages_destructor);
+	    message = _notmuch_message_create (messages, notmuch,
+					       *i, &status);
+	    if (message == NULL)
+	    {
+		if (status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND)
+		    INTERNAL_ERROR ("A message iterator contains a "
+				    "non-existent document ID.\n");
+		break;
+	    }
 
-	messages->iterator = mset.begin ();
-	messages->iterator_end = mset.end ();
+	    _notmuch_messages_add_message (messages, message);
+	}
 
     } catch (const Xapian::Error &error) {
 	fprintf (stderr, "A Xapian exception occurred: %s\n",
@@ -257,49 +250,6 @@ notmuch_query_destroy (notmuch_query_t *query)
 }
 
 notmuch_bool_t
-notmuch_messages_has_more (notmuch_messages_t *messages)
-{
-    return (messages->iterator != messages->iterator_end);
-}
-
-notmuch_message_t *
-notmuch_messages_get (notmuch_messages_t *messages)
-{
-    notmuch_message_t *message;
-    Xapian::docid doc_id;
-    notmuch_private_status_t status;
-
-    if (! notmuch_messages_has_more (messages))
-	return NULL;
-
-    doc_id = *messages->iterator;
-
-    message = _notmuch_message_create (messages,
-				       messages->notmuch, doc_id,
-				       &status);
-
-    if (message == NULL &&
-	status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND)
-    {
-	INTERNAL_ERROR ("a messages iterator contains a non-existent document ID.\n");
-    }
-
-    return message;
-}
-
-void
-notmuch_messages_advance (notmuch_messages_t *messages)
-{
-    messages->iterator++;
-}
-
-void
-notmuch_messages_destroy (notmuch_messages_t *messages)
-{
-    talloc_free (messages);
-}
-
-notmuch_bool_t
 notmuch_threads_has_more (notmuch_threads_t *threads)
 {
     return (threads->index < threads->threads->len);