[tracker/wip/miner-priority-queues: 1/19] libtracker-miner: Add TrackerPriorityQueue

[Carlos Garnacho <carlosg src gnome org>]

commit 50d4bac5229516a7ebe4bb57ff2b26aacda88571
Author: Carlos Garnacho <carlos lanedo com>
Date:   Tue Jun 28 14:36:45 2011 +0200

    libtracker-miner: Add TrackerPriorityQueue
    
    This is a simple type that allows insertion of elements with
    priorities, so doing pop() returns the highest/earliest element
    in the queue.

 src/libtracker-miner/Makefile.am              |    2 +
 src/libtracker-miner/tracker-priority-queue.c |  351 +++++++++++++++++++++++++
 src/libtracker-miner/tracker-priority-queue.h |   67 +++++
 3 files changed, 420 insertions(+), 0 deletions(-)
---
diff --git a/src/libtracker-miner/Makefile.am b/src/libtracker-miner/Makefile.am
index 5e8f8e5..b83a53c 100644
--- a/src/libtracker-miner/Makefile.am
+++ b/src/libtracker-miner/Makefile.am
@@ -34,6 +34,8 @@ crawler_sources = 				       \
 	tracker-utils.h					
 
 private_sources = 				       \
+	tracker-priority-queue.h                       \
+	tracker-priority-queue.c                       \
 	tracker-miner-fs-processing-pool.h             \
 	tracker-miner-fs-processing-pool.c             \
 	tracker-storage.c                              \
diff --git a/src/libtracker-miner/tracker-priority-queue.c b/src/libtracker-miner/tracker-priority-queue.c
new file mode 100644
index 0000000..4a9a24b
--- /dev/null
+++ b/src/libtracker-miner/tracker-priority-queue.c
@@ -0,0 +1,351 @@
+/*
+ * Copyright (C) 2011, Carlos Garnacho <carlos lanedo com>
+ *
+ * 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 2.1 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, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301, USA.
+ */
+
+#include "tracker-priority-queue.h"
+
+typedef struct PrioritySegment PrioritySegment;
+
+struct PrioritySegment
+{
+	gint priority;
+	GList *first_elem;
+	GList *last_elem;
+};
+
+struct _TrackerPriorityQueue
+{
+	GQueue queue;
+	GArray *segments;
+
+	gint ref_count;
+};
+
+TrackerPriorityQueue *
+tracker_priority_queue_new (void)
+{
+	TrackerPriorityQueue *queue;
+
+	queue = g_slice_new (TrackerPriorityQueue);
+	g_queue_init (&queue->queue);
+	queue->segments = g_array_new (FALSE, FALSE,
+	                               sizeof (PrioritySegment));
+
+	queue->ref_count = 1;
+
+	return queue;
+}
+
+TrackerPriorityQueue *
+tracker_priority_queue_ref (TrackerPriorityQueue *queue)
+{
+	g_atomic_int_inc (&queue->ref_count);
+	return queue;
+}
+
+void
+tracker_priority_queue_unref (TrackerPriorityQueue *queue)
+{
+	if (g_atomic_int_dec_and_test (&queue->ref_count)) {
+		g_queue_clear (&queue->queue);
+		g_array_free (queue->segments, TRUE);
+		g_slice_free (TrackerPriorityQueue, queue);
+	}
+}
+
+static GList *
+priority_segment_alloc_node (TrackerPriorityQueue *queue,
+                             gint                  priority)
+{
+	PrioritySegment *segment = NULL;
+	gboolean found = FALSE;
+	gint l, r, c;
+	GList *node;
+
+	/* Perform binary search to find out the segment for
+	 * the given priority, create one if it isn't found.
+	 */
+	l = 0;
+	r = queue->segments->len - 1;
+
+	while (queue->segments->len > 0 && !found) {
+		c = r + l / 2;
+		segment = &g_array_index (queue->segments, PrioritySegment, c);
+
+		if (segment->priority == priority) {
+			found = TRUE;
+			break;
+		} else if (segment->priority > priority) {
+			l = c + 1;
+		} else if (segment->priority < priority) {
+			r = c - 1;
+		}
+
+		if (l > r) {
+			break;
+		}
+	}
+
+	if (found) {
+		/* Element found, append at the end of segment */
+		g_assert (segment != NULL);
+		g_assert (segment->priority == priority);
+
+		g_queue_insert_after (&queue->queue, segment->last_elem, NULL);
+		node = segment->last_elem = segment->last_elem->next;
+	} else {
+		PrioritySegment new_segment = { 0 };
+
+		new_segment.priority = priority;
+
+		if (segment) {
+			g_assert (segment->priority != priority);
+
+			/* Binary search got to one of the closest results,
+			 * but we may have come from either of both sides,
+			 * so check whether we have to insert after the
+			 * segment we got.
+			 */
+			if (segment->priority > priority) {
+				/* We have to insert to the left of this element */
+				g_queue_insert_before (&queue->queue, segment->first_elem, NULL);
+				node = segment->first_elem->prev;
+			} else {
+				/* We have to insert to the right of this element */
+				g_queue_insert_after (&queue->queue, segment->last_elem, NULL);
+				node = segment->last_elem->next;
+				c++;
+			}
+
+			new_segment.first_elem = new_segment.last_elem = node;
+			g_array_insert_val (queue->segments, c, new_segment);
+		} else {
+			/* Segments list has 0 elements */
+			g_assert (queue->segments->len == 0);
+			g_assert (g_queue_get_length (&queue->queue) == 0);
+
+			node = g_list_alloc ();
+			g_queue_push_head_link (&queue->queue, node);
+			new_segment.first_elem = new_segment.last_elem = node;
+
+			g_array_append_val (queue->segments, new_segment);
+		}
+	}
+
+	return node;
+}
+
+void
+tracker_priority_queue_foreach (TrackerPriorityQueue *queue,
+                                GFunc                 func,
+                                gpointer              user_data)
+{
+	g_return_if_fail (queue != NULL);
+	g_return_if_fail (func != NULL);
+
+	g_queue_foreach (&queue->queue, func, user_data);
+}
+
+void
+tracker_priority_queue_foreach_remove (TrackerPriorityQueue *queue,
+                                       GEqualFunc            compare_func,
+                                       gpointer              compare_user_data,
+                                       GDestroyNotify        destroy_notify)
+{
+	PrioritySegment *segment;
+	gint n_segment = 0;
+	GList *list;
+
+	g_return_if_fail (queue != NULL);
+	g_return_if_fail (compare_func != NULL);
+
+	list = queue->queue.head;
+
+	if (!list) {
+		return;
+	}
+
+	segment = &g_array_index (queue->segments, PrioritySegment, n_segment);
+
+	while (list) {
+		GList *elem;
+
+		elem = list;
+		list = list->next;
+
+		if ((compare_func) (elem->data, compare_user_data)) {
+			/* Update segment limits */
+			if (elem == segment->first_elem &&
+			    elem == segment->last_elem) {
+				/* Last element of segment, remove it */
+				g_array_remove_index (queue->segments,
+				                      n_segment);
+
+				if (list) {
+					/* Fetch the next one */
+					segment = &g_array_index (queue->segments,
+					                          PrioritySegment,
+					                          n_segment);
+				}
+			} else if (elem == segment->first_elem) {
+				/* First elemen in segment */
+				segment->first_elem = elem->next;
+			} else if (elem == segment->last_elem) {
+				segment->last_elem = elem->prev;
+			}
+
+			if (destroy_notify) {
+				(destroy_notify) (elem->data);
+			}
+
+			g_queue_delete_link (&queue->queue, elem);
+		} else {
+			if (list != NULL &&
+			    elem == segment->last_elem) {
+				/* Move on to the next segment */
+				n_segment++;
+				g_assert (n_segment < queue->segments->len);
+
+				segment = &g_array_index (queue->segments,
+				                          PrioritySegment,
+				                          n_segment);
+			}
+		}
+	}
+}
+
+gboolean
+tracker_priority_queue_is_empty (TrackerPriorityQueue *queue)
+{
+	g_return_val_if_fail (queue != NULL, FALSE);
+
+	return g_queue_is_empty (&queue->queue);
+}
+
+void
+tracker_priority_queue_add (TrackerPriorityQueue *queue,
+                            gpointer              data,
+                            gint                  priority)
+{
+	GList *node;
+
+	g_return_if_fail (queue != NULL);
+	g_return_if_fail (data != NULL);
+
+	/* clamp on G_PRIORITY_HIGH, to avoid much greediness */
+	priority = MAX (priority, G_PRIORITY_HIGH);
+
+	node = priority_segment_alloc_node (queue, priority);
+	g_assert (node != NULL);
+
+	node->data = data;
+}
+
+gpointer
+tracker_priority_queue_find (TrackerPriorityQueue *queue,
+                             gint                 *priority_out,
+                             GEqualFunc            compare_func,
+                             gpointer              user_data)
+{
+	PrioritySegment *segment;
+	gint n_segment = 0;
+	GList *list;
+
+	g_return_val_if_fail (queue != NULL, NULL);
+	g_return_val_if_fail (compare_func != NULL, NULL);
+
+	list = queue->queue.head;
+	segment = &g_array_index (queue->segments, PrioritySegment, n_segment);
+
+	while (list) {
+		if ((compare_func) (list->data, user_data)) {
+			if (priority_out) {
+				*priority_out = segment->priority;
+			}
+
+			return list->data;
+		}
+
+		if (list->next != NULL &&
+		    list == segment->last_elem) {
+			/* Move on to the next segment */
+			n_segment++;
+			g_assert (n_segment < queue->segments->len);
+			segment = &g_array_index (queue->segments,
+			                          PrioritySegment,
+			                          n_segment);
+		}
+
+		list = list->next;
+	}
+
+	return NULL;
+}
+
+gpointer
+tracker_priority_queue_peek (TrackerPriorityQueue *queue,
+                             gint                 *priority_out)
+{
+	g_return_val_if_fail (queue != NULL, NULL);
+
+	if (priority_out) {
+		PrioritySegment *segment;
+
+		segment = &g_array_index (queue->segments, PrioritySegment, 0);
+		*priority_out = segment->priority;
+	}
+
+	return g_queue_peek_head (&queue->queue);
+}
+
+gpointer
+tracker_priority_queue_pop (TrackerPriorityQueue *queue,
+                            gint                 *priority_out)
+{
+	PrioritySegment *segment;
+	GList *node;
+
+	g_return_val_if_fail (queue != NULL, NULL);
+
+	node = g_queue_peek_head_link (&queue->queue);
+
+	if (!node) {
+		/* No elements in queue */
+		return NULL;
+	}
+
+	segment = &g_array_index (queue->segments, PrioritySegment, 0);
+	g_assert (segment->first_elem == node);
+
+	if (priority_out) {
+		*priority_out = segment->priority;
+	}
+
+	if (segment->last_elem == node) {
+		/* It is the last element of the first
+		 * segment, remove segment as well.
+		 */
+		g_array_remove_index (queue->segments, 0);
+	} else {
+
+		/* Move segments first element forward */
+		segment->first_elem = segment->first_elem->next;
+	}
+
+	return g_queue_pop_head (&queue->queue);
+}
diff --git a/src/libtracker-miner/tracker-priority-queue.h b/src/libtracker-miner/tracker-priority-queue.h
new file mode 100644
index 0000000..9a530cc
--- /dev/null
+++ b/src/libtracker-miner/tracker-priority-queue.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2011, Carlos Garnacho <carlos lanedo com>
+ *
+ * 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 2.1 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, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301, USA.
+ */
+
+#ifndef __TRACKER_PRIORITY_QUEUE_H__
+#define __TRACKER_PRIORITY_QUEUE_H__
+
+#include <glib.h>
+
+G_BEGIN_DECLS
+
+/* Some defines for priorities */
+#define TRACKER_QUEUE_PRIORITY_HIGH    -100
+#define TRACKER_QUEUE_PRIORITY_DEFAULT 0
+#define TRACKER_QUEUE_PRIORITY_LOW     100
+
+typedef struct _TrackerPriorityQueue TrackerPriorityQueue;
+
+TrackerPriorityQueue *tracker_priority_queue_new   (void);
+
+TrackerPriorityQueue *tracker_priority_queue_ref   (TrackerPriorityQueue *queue);
+void                  tracker_priority_queue_unref (TrackerPriorityQueue *queue);
+
+gboolean tracker_priority_queue_is_empty           (TrackerPriorityQueue *queue);
+
+void     tracker_priority_queue_add     (TrackerPriorityQueue *queue,
+                                         gpointer              data,
+                                         gint                  priority);
+
+void     tracker_priority_queue_foreach (TrackerPriorityQueue *queue,
+                                         GFunc                 func,
+                                         gpointer              user_data);
+
+void     tracker_priority_queue_foreach_remove (TrackerPriorityQueue *queue,
+                                                GEqualFunc            compare_func,
+                                                gpointer              compare_user_data,
+                                                GDestroyNotify        destroy_notify);
+
+gpointer tracker_priority_queue_find           (TrackerPriorityQueue *queue,
+                                                gint                 *priority_out,
+                                                GEqualFunc            compare_func,
+                                                gpointer              user_data);
+
+gpointer tracker_priority_queue_peek    (TrackerPriorityQueue *queue,
+                                         gint                 *priority_out);
+gpointer tracker_priority_queue_pop     (TrackerPriorityQueue *queue,
+                                         gint                 *priority_out);
+
+
+G_END_DECLS
+
+#endif /* __TRACKER_PRIORITY_QUEUE_H__ */