/* GdkPixbuf library

 * Copyright (C) 2003-2006 David Schleef <ds@schleef.org>

 *		 2005-2006 Eric Anholt <eric@anholt.net>

 *		 2006-2007 Benjamin Otte <otte@gnome.org>

 *

 * 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 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, see <http://www.gnu.org/licenses/>.

 */

#include "config.h"

#include "gdk-pixbuf-buffer-queue-private.h"

#include <string.h>

struct _GdkPixbufBufferQueue

{

  GSList *	first_buffer;		/* pointer to first buffer */

  GSList *	last_buffer;		/* pointer to last buffer (for fast appending) */

  gsize		size;			/* amount of bytes in the queue */

  gsize		offset;			/* amount of data already flushed out of the queue */

  int		ref_count;

};

/**

 * GdkPixbufBufferQueue:

 *

 * A #GdkPixbufBufferQueue is a queue of continuous buffers that allows reading

 * its data in chunks of pre-defined sizes. It is used to transform a data 

 * stream that was provided by buffers of random sizes to buffers of the right

 * size.

 */

/**

 * gdk_pixbuf_buffer_queue_new:

 *

 * Creates a new empty buffer queue.

 *

 * Returns: a new buffer queue. Use gdk_pixbuf_buffer_queue_unref () to free it.

 **/

GdkPixbufBufferQueue *

gdk_pixbuf_buffer_queue_new (void)

{

  GdkPixbufBufferQueue *buffer_queue;

  buffer_queue = g_new0 (GdkPixbufBufferQueue, 1);

  buffer_queue->ref_count = 1;

  return buffer_queue;

}

/**

 * gdk_pixbuf_buffer_queue_get_size:

 * @queue: a #GdkPixbufBufferQueue

 *

 * Returns the number of bytes currently in @queue.

 *

 * Returns: amount of bytes in @queue.

 **/

gsize

gdk_pixbuf_buffer_queue_get_size (GdkPixbufBufferQueue *queue)

{

  g_return_val_if_fail (queue != NULL, 0);

  return queue->size;

}

/**

 * gdk_pixbuf_buffer_queue_get_offset:

 * @queue: a #GdkPixbufBufferQueue

 *

 * Queries the amount of bytes that has already been pulled out of

 * @queue using functions like gdk_pixbuf_buffer_queue_pull().

 *

 * Returns: Number of bytes that were already pulled from this queue.

 **/

gsize

gdk_pixbuf_buffer_queue_get_offset (GdkPixbufBufferQueue * queue)

{

  g_return_val_if_fail (queue != NULL, 0);

  return queue->offset;

}

/**

 * gdk_pixbuf_buffer_queue_flush:

 * @queue: a #GdkPixbufBufferQueue

 * @n_bytes: amount of bytes to flush from the queue

 *

 * Removes the first @n_bytes bytes from the queue.

 */

void

gdk_pixbuf_buffer_queue_flush (GdkPixbufBufferQueue *queue, gsize n_bytes)

{

  g_return_if_fail (queue != NULL);

  g_return_if_fail (n_bytes <= queue->size);

  queue->size -= n_bytes;

  queue->offset += n_bytes;

  while (n_bytes > 0)

    {

      GBytes *bytes;

      gsize size;

      bytes = queue->first_buffer->data;

      size = g_bytes_get_size (bytes);

      if (size <= n_bytes)

        {

          n_bytes -= size;

          queue->first_buffer = g_slist_remove (queue->first_buffer, bytes);

        }

      else

        {

          queue->first_buffer->data = g_bytes_new_from_bytes (bytes,

	                                                      n_bytes,

                                                              size - n_bytes);

          n_bytes = 0;

        }

      g_bytes_unref (bytes);

    }

  if (queue->first_buffer == NULL)

    queue->last_buffer = NULL;

}

/**

 * gdk_pixbuf_buffer_queue_clear:

 * @queue: a #GdkPixbufBufferQueue

 *

 * Resets @queue into to initial state. All buffers it contains will be 

 * released and the offset will be reset to 0.

 **/

void

gdk_pixbuf_buffer_queue_clear (GdkPixbufBufferQueue *queue)

{

  g_return_if_fail (queue != NULL);

  g_slist_free_full (queue->first_buffer, (GDestroyNotify) g_bytes_unref);

  queue->first_buffer = NULL;

  queue->last_buffer = NULL;

  queue->size = 0;

  queue->offset = 0;

}

/**

 * gdk_pixbuf_buffer_queue_push:

 * @queue: a #GdkPixbufBufferQueue

 * @bytes: #GBytes to append to @queue

 *

 * Appends the given @bytes to the buffers already in @queue. This function

 * will take ownership of the given @buffer. Use g_bytes_ref () before

 * calling this function to keep a reference.

 **/

void

gdk_pixbuf_buffer_queue_push (GdkPixbufBufferQueue *queue,

                              GBytes               *bytes)

{

  gsize size;

  g_return_if_fail (queue != NULL);

  g_return_if_fail (bytes != NULL);

  size = g_bytes_get_size (bytes);

  if (size == 0)

    {

      g_bytes_unref (bytes);

      return;

    }

  queue->last_buffer = g_slist_append (queue->last_buffer, bytes);

  if (queue->first_buffer == NULL)

    queue->first_buffer = queue->last_buffer;

  else

    queue->last_buffer = queue->last_buffer->next;

  queue->size += size;

}

/**

 * gdk_pixbuf_buffer_queue_peek:

 * @queue: a #GdkPixbufBufferQueue to read from

 * @length: amount of bytes to peek

 *

 * Creates a new buffer with the first @length bytes from @queue, but unlike 

 * gdk_pixbuf_buffer_queue_pull(), does not remove them from @queue.

 *

 * Returns: NULL if the requested amount of data wasn't available or a new 

 *          #GBytes. Use g_bytes_unref() after use.

 **/

GBytes *

gdk_pixbuf_buffer_queue_peek (GdkPixbufBufferQueue *queue,

                              gsize                 length)

{

  GSList *g;

  GBytes *result, *bytes;

  g_return_val_if_fail (queue != NULL, NULL);

  if (queue->size < length)

    return NULL;

  /* need to special case here, because the queue may be empty */

  if (length == 0)

    return g_bytes_new (NULL, 0);

  g = queue->first_buffer;

  bytes = g->data;

  if (g_bytes_get_size (bytes) == length)

    {

      result = g_bytes_ref (bytes);

    }

  else if (g_bytes_get_size (bytes) > length)

    {

      result = g_bytes_new_from_bytes (bytes, 0, length);

    }

  else

    {

      guchar *data;

      gsize amount, offset;

      data = g_malloc (length);

      for (offset = 0; offset < length; offset += amount)

        {

          bytes = g->data;

          amount = MIN (length - offset, g_bytes_get_size (bytes));

          memcpy (data + offset, g_bytes_get_data (bytes, NULL), amount);

          g = g->next;

        }

      result = g_bytes_new_take (data, length);

    }

  return result;

}

/**

 * gdk_pixbuf_buffer_queue_pull:

 * @queue: a #GdkPixbufBufferQueue

 * @length: amount of bytes to pull

 *

 * If enough data is still available in @queue, the first @length bytes are 

 * put into a new buffer and that buffer is returned. The @length bytes are

 * removed from the head of the queue. If not enough data is available, %NULL

 * is returned.

 *

 * Returns: a new #GBytes or %NULL

 **/

GBytes *

gdk_pixbuf_buffer_queue_pull (GdkPixbufBufferQueue * queue, gsize length)

{

  GBytes *result;

  g_return_val_if_fail (queue != NULL, NULL);

  result = gdk_pixbuf_buffer_queue_peek (queue, length);

  if (result == NULL)

    return NULL;

  gdk_pixbuf_buffer_queue_flush (queue, length);

  return result;

}

/**

 * gdk_pixbuf_buffer_queue_peek_buffer:

 * @queue: a #GdkPixbufBufferQueue

 *

 * Gets the first buffer out of @queue and returns it. This function is 

 * equivalent to calling gdk_pixbuf_buffer_queue_peek() with the size of the

 * first buffer in it.

 *

 * Returns: The first buffer in @queue or %NULL if @queue is empty. Use 

 *          g_bytes_unref() after use.

 **/

GBytes *

gdk_pixbuf_buffer_queue_peek_buffer (GdkPixbufBufferQueue * queue)

{

  GBytes *bytes;

  g_return_val_if_fail (queue != NULL, NULL);

  if (queue->first_buffer == NULL)

    return NULL;

  bytes = queue->first_buffer->data;

  return g_bytes_ref (bytes);

}

/**

 * gdk_pixbuf_buffer_queue_pull_buffer:

 * @queue: a #GdkPixbufBufferQueue

 *

 * Pulls the first buffer out of @queue and returns it. This function is 

 * equivalent to calling gdk_pixbuf_buffer_queue_pull() with the size of the

 * first buffer in it.

 *

 * Returns: The first buffer in @queue or %NULL if @queue is empty.

 **/

GBytes *

gdk_pixbuf_buffer_queue_pull_buffer (GdkPixbufBufferQueue *queue)

{

  GBytes *bytes;

  g_return_val_if_fail (queue != NULL, NULL);

  bytes = gdk_pixbuf_buffer_queue_peek_buffer (queue);

  if (bytes)

    gdk_pixbuf_buffer_queue_flush (queue, g_bytes_get_size (bytes));

  return bytes;

}

/**

 * gdk_pixbuf_buffer_queue_ref:

 * @queue: a #GdkPixbufBufferQueue

 *

 * increases the reference count of @queue by one.

 *

 * Returns: The passed in @queue.

 **/

GdkPixbufBufferQueue *

gdk_pixbuf_buffer_queue_ref (GdkPixbufBufferQueue * queue)

{

  g_return_val_if_fail (queue != NULL, NULL);

  g_return_val_if_fail (queue->ref_count > 0, NULL);

  queue->ref_count++;

  return queue;

}

/**

 * gdk_pixbuf_buffer_queue_unref:

 * @queue: a #GdkPixbufBufferQueue

 *

 * Decreases the reference count of @queue by one. If no reference 

 * to this buffer exists anymore, the buffer and the memory 

 * it manages are freed.

 **/

void

gdk_pixbuf_buffer_queue_unref (GdkPixbufBufferQueue * queue)

{

  g_return_if_fail (queue != NULL);

  g_return_if_fail (queue->ref_count > 0);

  queue->ref_count--;

  if (queue->ref_count > 0)

    return;

  gdk_pixbuf_buffer_queue_clear (queue);

  g_free (queue);

}