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Allow NULL as compare function for direct value lookup. https://bugzilla.gnome.org/show_bug.cgi?id=692691
341 lines
8.4 KiB
C
341 lines
8.4 KiB
C
/* GStreamer
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* Copyright (C) 2009 Edward Hervey <bilboed@bilboed.com>
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*
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* gstqueuearray.c:
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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/**
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* SECTION:gstqueuearray
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* @short_description: Array based queue object
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*
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* #GstQueueArray is an object that provides standard queue functionality
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* based on an array instead of linked lists. This reduces the overhead
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* caused by memory managment by a large factor.
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*/
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#include <string.h>
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#include <gst/gst.h>
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#include "gstqueuearray.h"
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struct _GstQueueArray
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{
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/* < private > */
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gpointer *array;
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guint size;
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guint head;
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guint tail;
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guint length;
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};
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/**
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* gst_queue_array_new:
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* @initial_size: Initial size of the new queue
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*
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* Allocates a new #GstQueueArray object with an initial
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* queue size of @initial_size.
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*
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* Returns: a new #GstQueueArray object
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*
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* Since: 1.2.0
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*/
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GstQueueArray *
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gst_queue_array_new (guint initial_size)
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{
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GstQueueArray *array;
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array = g_slice_new (GstQueueArray);
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array->size = initial_size;
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array->array = g_new0 (gpointer, initial_size);
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array->head = 0;
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array->tail = 0;
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array->length = 0;
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return array;
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}
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/**
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* gst_queue_array_free:
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* @array: a #GstQueueArray object
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*
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* Frees queue @array and all memory associated to it.
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*
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* Since: 1.2.0
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*/
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void
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gst_queue_array_free (GstQueueArray * array)
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{
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g_free (array->array);
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g_slice_free (GstQueueArray, array);
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}
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/**
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* gst_queue_array_pop_head:
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* @array: a #GstQueueArray object
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*
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* Returns and head of the queue @array and removes
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* it from the queue.
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*
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* Returns: The head of the queue
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*
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* Since: 1.2.0
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*/
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gpointer
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gst_queue_array_pop_head (GstQueueArray * array)
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{
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gpointer ret;
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/* empty array */
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if (G_UNLIKELY (array->length == 0))
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return NULL;
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ret = array->array[array->head];
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array->head++;
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array->head %= array->size;
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array->length--;
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return ret;
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}
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/**
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* gst_queue_array_pop_head:
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* @array: a #GstQueueArray object
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*
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* Returns and head of the queue @array and does not
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* remove it from the queue.
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*
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* Returns: The head of the queue
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*
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* Since: 1.2.0
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*/
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gpointer
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gst_queue_array_peek_head (GstQueueArray * array)
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{
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/* empty array */
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if (G_UNLIKELY (array->length == 0))
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return NULL;
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return array->array[array->head];
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}
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/**
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* gst_queue_array_push_tail:
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* @array: a #GstQueueArray object
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* @data: object to push
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*
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* Pushes @data to the tail of the queue @array.
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*
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* Since: 1.2.0
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*/
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void
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gst_queue_array_push_tail (GstQueueArray * array, gpointer data)
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{
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/* Check if we need to make room */
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if (G_UNLIKELY (array->length == array->size)) {
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/* newsize is 50% bigger */
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guint newsize = (3 * array->size) / 2;
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/* copy over data */
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if (array->tail != 0) {
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gpointer *array2 = g_new0 (gpointer, newsize);
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guint t1 = array->head;
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guint t2 = array->size - array->head;
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/* [0-----TAIL][HEAD------SIZE]
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*
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* We want to end up with
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* [HEAD------------------TAIL][----FREEDATA------NEWSIZE]
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*
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* 1) move [HEAD-----SIZE] part to beginning of new array
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* 2) move [0-------TAIL] part new array, after previous part
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*/
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memcpy (array2, &array->array[array->head], t2 * sizeof (gpointer));
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memcpy (&array2[t2], array->array, t1 * sizeof (gpointer));
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g_free (array->array);
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array->array = array2;
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array->head = 0;
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} else {
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/* Fast path, we just need to grow the array */
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array->array = g_renew (gpointer, array->array, newsize);
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}
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array->tail = array->size;
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array->size = newsize;
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}
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array->array[array->tail] = data;
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array->tail++;
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array->tail %= array->size;
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array->length++;
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}
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/**
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* gst_queue_array_is_empty:
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* @array: a #GstQueueArray object
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*
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* Checks if the queue @array is empty.
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*
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* Returns: %TRUE if the queue @array is empty
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*
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* Since: 1.2.0
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*/
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gboolean
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gst_queue_array_is_empty (GstQueueArray * array)
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{
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return (array->length == 0);
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}
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/**
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* gst_queue_array_drop_element:
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* @array: a #GstQueueArray object
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* @idx: index to drop
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*
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* Drops the queue element at position @idx from queue @array.
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*
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* Returns: the dropped element
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*
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* Since: 1.2.0
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*/
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gpointer
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gst_queue_array_drop_element (GstQueueArray * array, guint idx)
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{
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int first_item_index, last_item_index;
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gpointer element;
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g_return_val_if_fail (array->length > 0, NULL);
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g_return_val_if_fail (idx < array->size, NULL);
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first_item_index = array->head;
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/* tail points to the first free spot */
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last_item_index = (array->tail - 1 + array->size) % array->size;
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element = array->array[idx];
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/* simple case idx == first item */
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if (idx == first_item_index) {
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/* move the head plus one */
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array->head++;
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array->head %= array->size;
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array->length--;
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return element;
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}
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/* simple case idx == last item */
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if (idx == last_item_index) {
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/* move tail minus one, potentially wrapping */
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array->tail = (array->tail - 1 + array->size) % array->size;
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array->length--;
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return element;
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}
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/* non-wrapped case */
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if (first_item_index < last_item_index) {
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g_assert (first_item_index < idx && idx < last_item_index);
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/* move everything beyond idx one step towards zero in array */
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memmove (&array->array[idx],
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&array->array[idx + 1], (last_item_index - idx) * sizeof (gpointer));
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/* tail might wrap, ie if tail == 0 (and last_item_index == size) */
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array->tail = (array->tail - 1 + array->size) % array->size;
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array->length--;
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return element;
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}
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/* only wrapped cases left */
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g_assert (first_item_index > last_item_index);
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if (idx < last_item_index) {
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/* idx is before last_item_index, move data towards zero */
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memmove (&array->array[idx],
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&array->array[idx + 1], (last_item_index - idx) * sizeof (gpointer));
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/* tail should not wrap in this case! */
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g_assert (array->tail > 0);
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array->tail--;
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array->length--;
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return element;
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}
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if (idx > first_item_index) {
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element = array->array[idx];
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/* idx is after first_item_index, move data to higher indices */
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memmove (&array->array[first_item_index + 1],
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&array->array[first_item_index],
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(idx - first_item_index) * sizeof (gpointer));
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array->head++;
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/* head should not wrap in this case! */
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g_assert (array->head < array->size);
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array->length--;
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return element;
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}
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g_return_val_if_reached (NULL);
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}
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/**
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* gst_queue_array_find:
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* @array: a #GstQueueArray object
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* @func: (allow-none): comparison function, or %NULL to find @data by value
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* @data: data for comparison function
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*
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* Finds an element in the queue @array, either by comparing every element
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* with @func or by looking up @data if no compare function @func is provided,
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* and returning the index of the found element.
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*
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* Note that the index is not 0-based, but an internal index number with a
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* random offset. The index can be used in connection with
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* gst_queue_array_drop_element(). FIXME: return index 0-based and make
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* _drop_element() take a 0-based index.
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*
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* Returns: Index of the found element or -1 if nothing was found.
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*
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* Since: 1.2.0
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*/
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guint
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gst_queue_array_find (GstQueueArray * array, GCompareFunc func, gpointer data)
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{
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guint i;
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if (func != NULL) {
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/* Scan from head to tail */
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for (i = 0; i < array->length; i++) {
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if (func (array->array[(i + array->head) % array->size], data) == 0)
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return (i + array->head) % array->size;
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}
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} else {
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for (i = 0; i < array->length; i++) {
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if (array->array[(i + array->head) % array->size] == data)
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return (i + array->head) % array->size;
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}
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}
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return -1;
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}
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/**
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* gst_queue_array_get_length:
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* @array: a #GstQueueArray object
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*
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* Returns the length of the queue @array
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*
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* Returns: the length of the queue @array.
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*
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* Since: 1.2.0
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*/
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guint
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gst_queue_array_get_length (GstQueueArray * array)
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{
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return array->length;
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}
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