gstreamer/libs/gst/base/gstqueuearray.c
Evan Nemerson 1cd4bd64b0 queuearray: fix expanding size of queue from 1
Without we would not actually expand and access
memory beyond the allocated region for the array.

https://bugzilla.gnome.org/show_bug.cgi?id=731349
2014-06-07 09:45:39 +01:00

341 lines
8.5 KiB
C

/* GStreamer
* Copyright (C) 2009 Edward Hervey <bilboed@bilboed.com>
*
* gstqueuearray.c:
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/**
* SECTION:gstqueuearray
* @short_description: Array based queue object
*
* #GstQueueArray is an object that provides standard queue functionality
* based on an array instead of linked lists. This reduces the overhead
* caused by memory management by a large factor.
*/
#include <string.h>
#include <gst/gst.h>
#include "gstqueuearray.h"
struct _GstQueueArray
{
/* < private > */
gpointer *array;
guint size;
guint head;
guint tail;
guint length;
};
/**
* gst_queue_array_new:
* @initial_size: Initial size of the new queue
*
* Allocates a new #GstQueueArray object with an initial
* queue size of @initial_size.
*
* Returns: a new #GstQueueArray object
*
* Since: 1.2
*/
GstQueueArray *
gst_queue_array_new (guint initial_size)
{
GstQueueArray *array;
array = g_slice_new (GstQueueArray);
array->size = initial_size;
array->array = g_new0 (gpointer, initial_size);
array->head = 0;
array->tail = 0;
array->length = 0;
return array;
}
/**
* gst_queue_array_free:
* @array: a #GstQueueArray object
*
* Frees queue @array and all memory associated to it.
*
* Since: 1.2
*/
void
gst_queue_array_free (GstQueueArray * array)
{
g_free (array->array);
g_slice_free (GstQueueArray, array);
}
/**
* gst_queue_array_pop_head:
* @array: a #GstQueueArray object
*
* Returns and head of the queue @array and removes
* it from the queue.
*
* Returns: The head of the queue
*
* Since: 1.2
*/
gpointer
gst_queue_array_pop_head (GstQueueArray * array)
{
gpointer ret;
/* empty array */
if (G_UNLIKELY (array->length == 0))
return NULL;
ret = array->array[array->head];
array->head++;
array->head %= array->size;
array->length--;
return ret;
}
/**
* gst_queue_array_peek_head:
* @array: a #GstQueueArray object
*
* Returns and head of the queue @array and does not
* remove it from the queue.
*
* Returns: The head of the queue
*
* Since: 1.2
*/
gpointer
gst_queue_array_peek_head (GstQueueArray * array)
{
/* empty array */
if (G_UNLIKELY (array->length == 0))
return NULL;
return array->array[array->head];
}
/**
* gst_queue_array_push_tail:
* @array: a #GstQueueArray object
* @data: object to push
*
* Pushes @data to the tail of the queue @array.
*
* Since: 1.2
*/
void
gst_queue_array_push_tail (GstQueueArray * array, gpointer data)
{
/* Check if we need to make room */
if (G_UNLIKELY (array->length == array->size)) {
/* newsize is 50% bigger */
guint newsize = MAX ((3 * array->size) / 2, array->size + 1);
/* copy over data */
if (array->tail != 0) {
gpointer *array2 = g_new0 (gpointer, newsize);
guint t1 = array->head;
guint t2 = array->size - array->head;
/* [0-----TAIL][HEAD------SIZE]
*
* We want to end up with
* [HEAD------------------TAIL][----FREEDATA------NEWSIZE]
*
* 1) move [HEAD-----SIZE] part to beginning of new array
* 2) move [0-------TAIL] part new array, after previous part
*/
memcpy (array2, &array->array[array->head], t2 * sizeof (gpointer));
memcpy (&array2[t2], array->array, t1 * sizeof (gpointer));
g_free (array->array);
array->array = array2;
array->head = 0;
} else {
/* Fast path, we just need to grow the array */
array->array = g_renew (gpointer, array->array, newsize);
}
array->tail = array->size;
array->size = newsize;
}
array->array[array->tail] = data;
array->tail++;
array->tail %= array->size;
array->length++;
}
/**
* gst_queue_array_is_empty:
* @array: a #GstQueueArray object
*
* Checks if the queue @array is empty.
*
* Returns: %TRUE if the queue @array is empty
*
* Since: 1.2
*/
gboolean
gst_queue_array_is_empty (GstQueueArray * array)
{
return (array->length == 0);
}
/**
* gst_queue_array_drop_element:
* @array: a #GstQueueArray object
* @idx: index to drop
*
* Drops the queue element at position @idx from queue @array.
*
* Returns: the dropped element
*
* Since: 1.2
*/
gpointer
gst_queue_array_drop_element (GstQueueArray * array, guint idx)
{
int first_item_index, last_item_index;
gpointer element;
g_return_val_if_fail (array->length > 0, NULL);
g_return_val_if_fail (idx < array->size, NULL);
first_item_index = array->head;
/* tail points to the first free spot */
last_item_index = (array->tail - 1 + array->size) % array->size;
element = array->array[idx];
/* simple case idx == first item */
if (idx == first_item_index) {
/* move the head plus one */
array->head++;
array->head %= array->size;
array->length--;
return element;
}
/* simple case idx == last item */
if (idx == last_item_index) {
/* move tail minus one, potentially wrapping */
array->tail = (array->tail - 1 + array->size) % array->size;
array->length--;
return element;
}
/* non-wrapped case */
if (first_item_index < last_item_index) {
g_assert (first_item_index < idx && idx < last_item_index);
/* move everything beyond idx one step towards zero in array */
memmove (&array->array[idx],
&array->array[idx + 1], (last_item_index - idx) * sizeof (gpointer));
/* tail might wrap, ie if tail == 0 (and last_item_index == size) */
array->tail = (array->tail - 1 + array->size) % array->size;
array->length--;
return element;
}
/* only wrapped cases left */
g_assert (first_item_index > last_item_index);
if (idx < last_item_index) {
/* idx is before last_item_index, move data towards zero */
memmove (&array->array[idx],
&array->array[idx + 1], (last_item_index - idx) * sizeof (gpointer));
/* tail should not wrap in this case! */
g_assert (array->tail > 0);
array->tail--;
array->length--;
return element;
}
if (idx > first_item_index) {
element = array->array[idx];
/* idx is after first_item_index, move data to higher indices */
memmove (&array->array[first_item_index + 1],
&array->array[first_item_index],
(idx - first_item_index) * sizeof (gpointer));
array->head++;
/* head should not wrap in this case! */
g_assert (array->head < array->size);
array->length--;
return element;
}
g_return_val_if_reached (NULL);
}
/**
* gst_queue_array_find:
* @array: a #GstQueueArray object
* @func: (allow-none): comparison function, or %NULL to find @data by value
* @data: data for comparison function
*
* Finds an element in the queue @array, either by comparing every element
* with @func or by looking up @data if no compare function @func is provided,
* and returning the index of the found element.
*
* Note that the index is not 0-based, but an internal index number with a
* random offset. The index can be used in connection with
* gst_queue_array_drop_element(). FIXME: return index 0-based and make
* gst_queue_array_drop_element() take a 0-based index.
*
* Returns: Index of the found element or -1 if nothing was found.
*
* Since: 1.2
*/
guint
gst_queue_array_find (GstQueueArray * array, GCompareFunc func, gpointer data)
{
guint i;
if (func != NULL) {
/* Scan from head to tail */
for (i = 0; i < array->length; i++) {
if (func (array->array[(i + array->head) % array->size], data) == 0)
return (i + array->head) % array->size;
}
} else {
for (i = 0; i < array->length; i++) {
if (array->array[(i + array->head) % array->size] == data)
return (i + array->head) % array->size;
}
}
return -1;
}
/**
* gst_queue_array_get_length:
* @array: a #GstQueueArray object
*
* Returns the length of the queue @array
*
* Returns: the length of the queue @array.
*
* Since: 1.2
*/
guint
gst_queue_array_get_length (GstQueueArray * array)
{
return array->length;
}