1 /* GStreamer

     2  * Copyright (C) 2004 Benjamin Otte <otte@gnome.org>

     3  *               2005 Wim Taymans <wim@fluendo.com>

     4  *

     5  * This library is free software; you can redistribute it and/or

     6  * modify it under the terms of the GNU Library General Public

     7  * License as published by the Free Software Foundation; either

     8  * version 2 of the License, or (at your option) any later version.

     9  *

    10  * This library is distributed in the hope that it will be useful,

    11  * but WITHOUT ANY WARRANTY; without even the implied warranty of

    12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    13  * Library General Public License for more details.

    14  *

    15  * You should have received a copy of the GNU Library General Public

    16  * License along with this library; if not, write to the

    17  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,

    18  * Boston, MA 02111-1307, USA.

    19  */

    20 

    21 /**

    22  * SECTION:gstadapter

    23  * @short_description: adapts incoming data on a sink pad into chunks of N bytes

    24  *

    25  * This class is for elements that receive buffers in an undesired size.

    26  * While for example raw video contains one image per buffer, the same is not

    27  * true for a lot of other formats, especially those that come directly from

    28  * a file. So if you have undefined buffer sizes and require a specific size,

    29  * this object is for you.

    30  *

    31  * An adapter is created with gst_adapter_new(). It can be freed again with

    32  * g_object_unref().

    33  *

    34  * The theory of operation is like this: All buffers received are put

    35  * into the adapter using gst_adapter_push() and the data is then read back

    36  * in chunks of the desired size using gst_adapter_peek(). After the data is

    37  * processed, it is freed using gst_adapter_flush().

    38  *

    39  * For example, a sink pad's chain function that needs to pass data to a library

    40  * in 512-byte chunks could be implemented like this:

    41  * <programlisting>

    42  * static GstFlowReturn

    43  * sink_pad_chain (GstPad *pad, GstBuffer *buffer)

    44  * {

    45  *   MyElement *this;

    46  *   GstAdapter *adapter;

    47  *   GstFlowReturn ret = GST_FLOW_OK;

    48  *   

    49  *   // will give the element an extra ref; remember to drop it 

    50  *   this = MY_ELEMENT (gst_pad_get_parent (pad));

    51  *   adapter = this->adapter;

    52  *   

    53  *   // put buffer into adapter

    54  *   gst_adapter_push (adapter, buffer);

    55  *   // while we can read out 512 bytes, process them

    56  *   while (gst_adapter_available (adapter) >= 512 && ret == GST_FLOW_OK) {

    57  *     // use flowreturn as an error value

    58  *     ret = my_library_foo (gst_adapter_peek (adapter, 512));

    59  *     gst_adapter_flush (adapter, 512);

    60  *   }

    61  *   

    62  *   gst_object_unref (this);

    63  *   return ret;

    64  * }

    65  * </programlisting>

    66  * For another example, a simple element inside GStreamer that uses GstAdapter

    67  * is the libvisual element.

    68  *

    69  * An element using GstAdapter in its sink pad chain function should ensure that

    70  * when the FLUSH_STOP event is received, that any queued data is cleared using

    71  * gst_adapter_clear(). Data should also be cleared or processed on EOS and

    72  * when changing state from #GST_STATE_PAUSED to #GST_STATE_READY.

    73  *

    74  * Also check the GST_BUFFER_FLAG_DISCONT flag on the buffer. Some elements might

    75  * need to clear the adapter after a discontinuity.

    76  *

    77  * A last thing to note is that while GstAdapter is pretty optimized,

    78  * merging buffers still might be an operation that requires a memcpy()

    79  * operation, and this operation is not the fastest. Because of this, some

    80  * functions like gst_adapter_available_fast() are provided to help speed up

    81  * such cases should you want to.

    82  *

    83  * GstAdapter is not MT safe. All operations on an adapter must be serialized by

    84  * the caller. This is not normally a problem, however, as the normal use case

    85  * of GstAdapter is inside one pad's chain function, in which case access is

    86  * serialized via the pad's STREAM_LOCK.

    87  *

    88  * Note that gst_adapter_push() takes ownership of the buffer passed. Use 

    89  * gst_buffer_ref() before pushing it into the adapter if you still want to

    90  * access the buffer later. The adapter will never modify the data in the

    91  * buffer pushed in it.

    92  *

    93  * Last reviewed on 2006-04-04 (0.10.6).

    94  */

    95 

    96 #ifdef __SYMBIAN32__

    97 #include <gst_global.h>

    98 #endif

    99 

   100 #include "gstadapter.h"

   101 #include <string.h>

   102 

   103 /* default size for the assembled data buffer */

   104 #define DEFAULT_SIZE 16

   105 

   106 GST_DEBUG_CATEGORY_STATIC (gst_adapter_debug);

   107 #define GST_CAT_DEFAULT gst_adapter_debug

   108 

   109 #define _do_init(thing) \

   110   GST_DEBUG_CATEGORY_INIT (gst_adapter_debug, "adapter", 0, "object to splice and merge buffers to desired size")

   111 GST_BOILERPLATE_FULL (GstAdapter, gst_adapter, GObject, G_TYPE_OBJECT,

   112     _do_init);

   113 

   114 static void gst_adapter_dispose (GObject * object);

   115 static void gst_adapter_finalize (GObject * object);

   116 

   117 static void

   118 gst_adapter_base_init (gpointer g_class)

   119 {

   120   /* nop */

   121 }

   122 

   123 static void

   124 gst_adapter_class_init (GstAdapterClass * klass)

   125 {

   126   GObjectClass *object = G_OBJECT_CLASS (klass);

   127 

   128   object->dispose = gst_adapter_dispose;

   129   object->finalize = gst_adapter_finalize;

   130 }

   131 

   132 static void

   133 gst_adapter_init (GstAdapter * adapter, GstAdapterClass * g_class)

   134 {

   135   adapter->assembled_data = g_malloc (DEFAULT_SIZE);

   136   adapter->assembled_size = DEFAULT_SIZE;

   137 }

   138 

   139 static void

   140 gst_adapter_dispose (GObject * object)

   141 {

   142   GstAdapter *adapter = GST_ADAPTER (object);

   143 

   144   gst_adapter_clear (adapter);

   145 

   146   GST_CALL_PARENT (G_OBJECT_CLASS, dispose, (object));

   147 }

   148 

   149 static void

   150 gst_adapter_finalize (GObject * object)

   151 {

   152   GstAdapter *adapter = GST_ADAPTER (object);

   153 

   154   g_free (adapter->assembled_data);

   155 

   156   GST_CALL_PARENT (G_OBJECT_CLASS, finalize, (object));

   157 }

   158 

   159 /**

   160  * gst_adapter_new:

   161  *

   162  * Creates a new #GstAdapter. Free with g_object_unref().

   163  *

   164  * Returns: a new #GstAdapter

   165  */

   166 #ifdef __SYMBIAN32__

   167 EXPORT_C

   168 #endif

   169 

   170 GstAdapter *

   171 gst_adapter_new (void)

   172 {

   173   return g_object_new (GST_TYPE_ADAPTER, NULL);

   174 }

   175 

   176 /**

   177  * gst_adapter_clear:

   178  * @adapter: a #GstAdapter

   179  *

   180  * Removes all buffers from @adapter.

   181  */

   182 #ifdef __SYMBIAN32__

   183 EXPORT_C

   184 #endif

   185 

   186 void

   187 gst_adapter_clear (GstAdapter * adapter)

   188 {

   189   g_return_if_fail (GST_IS_ADAPTER (adapter));

   190 

   191   g_slist_foreach (adapter->buflist, (GFunc) gst_mini_object_unref, NULL);

   192   g_slist_free (adapter->buflist);

   193   adapter->buflist = NULL;

   194   adapter->buflist_end = NULL;

   195   adapter->size = 0;

   196   adapter->skip = 0;

   197   adapter->assembled_len = 0;

   198 }

   199 

   200 /**

   201  * gst_adapter_push:

   202  * @adapter: a #GstAdapter

   203  * @buf: a #GstBuffer to add to queue in the adapter

   204  *

   205  * Adds the data from @buf to the data stored inside @adapter and takes

   206  * ownership of the buffer.

   207  */

   208 #ifdef __SYMBIAN32__

   209 EXPORT_C

   210 #endif

   211 

   212 void

   213 gst_adapter_push (GstAdapter * adapter, GstBuffer * buf)

   214 {

   215   g_return_if_fail (GST_IS_ADAPTER (adapter));

   216   g_return_if_fail (GST_IS_BUFFER (buf));

   217 

   218   adapter->size += GST_BUFFER_SIZE (buf);

   219 

   220   /* Note: merging buffers at this point is premature. */

   221   if (G_UNLIKELY (adapter->buflist == NULL)) {

   222     adapter->buflist = adapter->buflist_end = g_slist_append (NULL, buf);

   223   } else {

   224     /* Otherwise append to the end, and advance our end pointer */

   225     adapter->buflist_end = g_slist_append (adapter->buflist_end, buf);

   226     adapter->buflist_end = g_slist_next (adapter->buflist_end);

   227   }

   228 }

   229 

   230 /* Internal function that copies data into the given buffer, size must be 

   231  * bigger than the first buffer */

   232 static void

   233 gst_adapter_peek_into (GstAdapter * adapter, guint8 * data, guint size)

   234 {

   235   GstBuffer *cur;

   236   GSList *cur_list;

   237   guint copied, to_copy;

   238 

   239   /* The first buffer might be partly consumed, so need to handle

   240    * 'skipped' bytes. */

   241   cur = adapter->buflist->data;

   242   copied = to_copy = MIN (GST_BUFFER_SIZE (cur) - adapter->skip, size);

   243   memcpy (data, GST_BUFFER_DATA (cur) + adapter->skip, copied);

   244   data += copied;

   245 

   246   cur_list = g_slist_next (adapter->buflist);

   247   while (copied < size) {

   248     g_assert (cur_list);

   249     cur = cur_list->data;

   250     cur_list = g_slist_next (cur_list);

   251     to_copy = MIN (GST_BUFFER_SIZE (cur), size - copied);

   252     memcpy (data, GST_BUFFER_DATA (cur), to_copy);

   253     data += to_copy;

   254     copied += to_copy;

   255   }

   256 }

   257 

   258 /* Internal method only. Tries to merge buffers at the head of the queue

   259  * to form a single larger buffer of size 'size'. Only merges buffers that

   260  * where 'gst_buffer_is_span_fast' returns TRUE.

   261  *

   262  * Returns TRUE if it managed to merge anything.

   263  */

   264 static gboolean

   265 gst_adapter_try_to_merge_up (GstAdapter * adapter, guint size)

   266 {

   267   GstBuffer *cur, *head;

   268   GSList *g;

   269 

   270   g = adapter->buflist;

   271   if (g == NULL)

   272     return FALSE;

   273 

   274   head = g->data;

   275   g = g_slist_next (g);

   276 

   277   /* How large do we want our head buffer? The requested size, plus whatever's

   278    * been skipped already */

   279   size += adapter->skip;

   280 

   281   while (g != NULL && GST_BUFFER_SIZE (head) < size) {

   282     cur = g->data;

   283     if (!gst_buffer_is_span_fast (head, cur))

   284       return TRUE;

   285 

   286     /* Merge the head buffer and the next in line */

   287     GST_LOG_OBJECT (adapter,

   288         "Merging buffers of size %u & %u in search of target %u",

   289         GST_BUFFER_SIZE (head), GST_BUFFER_SIZE (cur), size);

   290 

   291     head = gst_buffer_join (head, cur);

   292 

   293     /* Delete the front list item, and store our new buffer in the 2nd list 

   294      * item */

   295     adapter->buflist = g_slist_delete_link (adapter->buflist, adapter->buflist);

   296     g->data = head;

   297   }

   298 

   299   return FALSE;

   300 }

   301 

   302 /**

   303  * gst_adapter_peek:

   304  * @adapter: a #GstAdapter

   305  * @size: the number of bytes to peek

   306  *

   307  * Gets the first @size bytes stored in the @adapter. The returned pointer is

   308  * valid until the next function is called on the adapter.

   309  *

   310  * Note that setting the returned pointer as the data of a #GstBuffer is

   311  * incorrect for general-purpose plugins. The reason is that if a downstream

   312  * element stores the buffer so that it has access to it outside of the bounds

   313  * of its chain function, the buffer will have an invalid data pointer after

   314  * your element flushes the bytes. In that case you should use

   315  * gst_adapter_take(), which returns a freshly-allocated buffer that you can set

   316  * as #GstBuffer malloc_data or the potentially more performant 

   317  * gst_adapter_take_buffer().

   318  *

   319  * Returns #NULL if @size bytes are not available.

   320  *

   321  * Returns: a pointer to the first @size bytes of data, or NULL.

   322  */

   323 #ifdef __SYMBIAN32__

   324 EXPORT_C

   325 #endif

   326 

   327 const guint8 *

   328 gst_adapter_peek (GstAdapter * adapter, guint size)

   329 {

   330   GstBuffer *cur;

   331 

   332   g_return_val_if_fail (GST_IS_ADAPTER (adapter), NULL);

   333   g_return_val_if_fail (size > 0, NULL);

   334 

   335   /* we don't have enough data, return NULL. This is unlikely

   336    * as one usually does an _available() first instead of peeking a

   337    * random size. */

   338   if (G_UNLIKELY (size > adapter->size))

   339     return NULL;

   340 

   341   /* we have enough assembled data, return it */

   342   if (adapter->assembled_len >= size)

   343     return adapter->assembled_data;

   344 

   345   /* our head buffer has enough data left, return it */

   346   cur = adapter->buflist->data;

   347   if (GST_BUFFER_SIZE (cur) >= size + adapter->skip)

   348     return GST_BUFFER_DATA (cur) + adapter->skip;

   349 

   350   /* We may be able to efficiently merge buffers in our pool to 

   351    * gather a big enough chunk to return it from the head buffer directly */

   352   if (gst_adapter_try_to_merge_up (adapter, size)) {

   353     /* Merged something! Check if there's enough avail now */

   354     cur = adapter->buflist->data;

   355     if (GST_BUFFER_SIZE (cur) >= size + adapter->skip)

   356       return GST_BUFFER_DATA (cur) + adapter->skip;

   357   }

   358 

   359   /* Gonna need to copy stuff out */

   360   if (adapter->assembled_size < size) {

   361     adapter->assembled_size = (size / DEFAULT_SIZE + 1) * DEFAULT_SIZE;

   362     GST_DEBUG_OBJECT (adapter, "setting size of internal buffer to %u",

   363         adapter->assembled_size);

   364     g_free (adapter->assembled_data);

   365     adapter->assembled_data = g_malloc (adapter->assembled_size);

   366   }

   367   adapter->assembled_len = size;

   368 

   369   gst_adapter_peek_into (adapter, adapter->assembled_data, size);

   370 

   371   return adapter->assembled_data;

   372 }

   373 

   374 /**

   375  * gst_adapter_copy:

   376  * @adapter: a #GstAdapter

   377  * @dest: the memory where to copy to

   378  * @offset: the bytes offset in the adapter to start from

   379  * @size: the number of bytes to copy

   380  *

   381  * Copies @size bytes of data starting at @offset out of the buffers

   382  * contained in @GstAdapter into an array @dest provided by the caller.

   383  *

   384  * The array @dest should be large enough to contain @size bytes.

   385  * The user should check that the adapter has (@offset + @size) bytes

   386  * available before calling this function.

   387  *

   388  * Since: 0.10.12

   389  */

   390 #ifdef __SYMBIAN32__

   391 EXPORT_C

   392 #endif

   393 

   394 void

   395 gst_adapter_copy (GstAdapter * adapter, guint8 * dest, guint offset, guint size)

   396 {

   397   GSList *g;

   398   int skip;

   399 

   400   g_return_if_fail (GST_IS_ADAPTER (adapter));

   401   g_return_if_fail (size > 0);

   402 

   403   /* we don't have enough data, return. This is unlikely

   404    * as one usually does an _available() first instead of copying a

   405    * random size. */

   406   if (G_UNLIKELY (offset + size > adapter->size))

   407     return;

   408 

   409   skip = adapter->skip;

   410   for (g = adapter->buflist; g && size > 0; g = g_slist_next (g)) {

   411     GstBuffer *buf;

   412 

   413     buf = g->data;

   414     if (offset < GST_BUFFER_SIZE (buf) - skip) {

   415       int n;

   416 

   417       n = MIN (GST_BUFFER_SIZE (buf) - skip - offset, size);

   418       memcpy (dest, GST_BUFFER_DATA (buf) + skip + offset, n);

   419 

   420       dest += n;

   421       offset = 0;

   422       size -= n;

   423     } else {

   424       offset -= GST_BUFFER_SIZE (buf) - skip;

   425     }

   426     skip = 0;

   427   }

   428 }

   429 

   430 /**

   431  * gst_adapter_flush:

   432  * @adapter: a #GstAdapter

   433  * @flush: the number of bytes to flush

   434  *

   435  * Flushes the first @flush bytes in the @adapter. The caller must ensure that

   436  * at least this many bytes are available.

   437  *

   438  * See also: gst_adapter_peek().

   439  */

   440 #ifdef __SYMBIAN32__

   441 EXPORT_C

   442 #endif

   443 

   444 void

   445 gst_adapter_flush (GstAdapter * adapter, guint flush)

   446 {

   447   GstBuffer *cur;

   448 

   449   g_return_if_fail (GST_IS_ADAPTER (adapter));

   450   g_return_if_fail (flush <= adapter->size);

   451 

   452   GST_LOG_OBJECT (adapter, "flushing %u bytes", flush);

   453   adapter->size -= flush;

   454   adapter->assembled_len = 0;

   455   while (flush > 0) {

   456     cur = adapter->buflist->data;

   457     if (GST_BUFFER_SIZE (cur) <= flush + adapter->skip) {

   458       /* can skip whole buffer */

   459       flush -= GST_BUFFER_SIZE (cur) - adapter->skip;

   460       adapter->skip = 0;

   461       adapter->buflist =

   462           g_slist_delete_link (adapter->buflist, adapter->buflist);

   463       if (G_UNLIKELY (adapter->buflist == NULL))

   464         adapter->buflist_end = NULL;

   465       gst_buffer_unref (cur);

   466     } else {

   467       adapter->skip += flush;

   468       break;

   469     }

   470   }

   471 }

   472 

   473 /**

   474  * gst_adapter_take:

   475  * @adapter: a #GstAdapter

   476  * @nbytes: the number of bytes to take

   477  *

   478  * Returns a freshly allocated buffer containing the first @nbytes bytes of the

   479  * @adapter. The returned bytes will be flushed from the adapter.

   480  *

   481  * Caller owns returned value. g_free after usage.

   482  *

   483  * Returns: oven-fresh hot data, or #NULL if @nbytes bytes are not available

   484  */

   485 #ifdef __SYMBIAN32__

   486 EXPORT_C

   487 #endif

   488 

   489 guint8 *

   490 gst_adapter_take (GstAdapter * adapter, guint nbytes)

   491 {

   492   guint8 *data;

   493 

   494   g_return_val_if_fail (GST_IS_ADAPTER (adapter), NULL);

   495   g_return_val_if_fail (nbytes > 0, NULL);

   496 

   497   /* we don't have enough data, return NULL. This is unlikely

   498    * as one usually does an _available() first instead of peeking a

   499    * random size. */

   500   if (G_UNLIKELY (nbytes > adapter->size))

   501     return NULL;

   502 

   503   data = g_malloc (nbytes);

   504 

   505   /* we have enough assembled data, copy from there */

   506   if (adapter->assembled_len >= nbytes) {

   507     GST_LOG_OBJECT (adapter, "taking %u bytes already assembled", nbytes);

   508     memcpy (data, adapter->assembled_data, nbytes);

   509   } else {

   510     GST_LOG_OBJECT (adapter, "taking %u bytes by collection", nbytes);

   511     gst_adapter_peek_into (adapter, data, nbytes);

   512   }

   513 

   514   gst_adapter_flush (adapter, nbytes);

   515 

   516   return data;

   517 }

   518 

   519 /**

   520  * gst_adapter_take_buffer:

   521  * @adapter: a #GstAdapter

   522  * @nbytes: the number of bytes to take

   523  *

   524  * Returns a #GstBuffer containing the first @nbytes bytes of the

   525  * @adapter. The returned bytes will be flushed from the adapter.

   526  * This function is potentially more performant than gst_adapter_take() 

   527  * since it can reuse the memory in pushed buffers by subbuffering

   528  * or merging.

   529  *

   530  * Caller owns returned value. gst_buffer_unref() after usage.

   531  *

   532  * Since: 0.10.6

   533  *

   534  * Returns: a #GstBuffer containing the first @nbytes of the adapter, 

   535  * or #NULL if @nbytes bytes are not available

   536  */

   537 #ifdef __SYMBIAN32__

   538 EXPORT_C

   539 #endif

   540 

   541 GstBuffer *

   542 gst_adapter_take_buffer (GstAdapter * adapter, guint nbytes)

   543 {

   544   GstBuffer *buffer;

   545   GstBuffer *cur;

   546 

   547   g_return_val_if_fail (GST_IS_ADAPTER (adapter), NULL);

   548   g_return_val_if_fail (nbytes > 0, NULL);

   549 

   550   GST_LOG_OBJECT (adapter, "taking buffer of %u bytes", nbytes);

   551 

   552   /* we don't have enough data, return NULL. This is unlikely

   553    * as one usually does an _available() first instead of grabbing a

   554    * random size. */

   555   if (G_UNLIKELY (nbytes > adapter->size))

   556     return NULL;

   557 

   558   /* our head buffer has enough data left, return it */

   559   cur = adapter->buflist->data;

   560   if (GST_BUFFER_SIZE (cur) >= nbytes + adapter->skip) {

   561     GST_LOG_OBJECT (adapter, "providing buffer of %d bytes via sub-buffer",

   562         nbytes);

   563     buffer = gst_buffer_create_sub (cur, adapter->skip, nbytes);

   564 

   565     gst_adapter_flush (adapter, nbytes);

   566 

   567     return buffer;

   568   }

   569 

   570   if (gst_adapter_try_to_merge_up (adapter, nbytes)) {

   571     /* Merged something, let's try again for sub-buffering */

   572     cur = adapter->buflist->data;

   573     if (GST_BUFFER_SIZE (cur) >= nbytes + adapter->skip) {

   574       GST_LOG_OBJECT (adapter, "providing buffer of %d bytes via sub-buffer",

   575           nbytes);

   576       buffer = gst_buffer_create_sub (cur, adapter->skip, nbytes);

   577 

   578       gst_adapter_flush (adapter, nbytes);

   579 

   580       return buffer;

   581     }

   582   }

   583 

   584   buffer = gst_buffer_new_and_alloc (nbytes);

   585 

   586   /* we have enough assembled data, copy from there */

   587   if (adapter->assembled_len >= nbytes) {

   588     GST_LOG_OBJECT (adapter, "taking %u bytes already assembled", nbytes);

   589     memcpy (GST_BUFFER_DATA (buffer), adapter->assembled_data, nbytes);

   590   } else {

   591     GST_LOG_OBJECT (adapter, "taking %u bytes by collection", nbytes);

   592     gst_adapter_peek_into (adapter, GST_BUFFER_DATA (buffer), nbytes);

   593   }

   594 

   595   gst_adapter_flush (adapter, nbytes);

   596 

   597   return buffer;

   598 }

   599 

   600 /**

   601  * gst_adapter_available:

   602  * @adapter: a #GstAdapter

   603  *

   604  * Gets the maximum amount of bytes available, that is it returns the maximum

   605  * value that can be supplied to gst_adapter_peek() without that function

   606  * returning NULL.

   607  *

   608  * Returns: number of bytes available in @adapter

   609  */

   610 #ifdef __SYMBIAN32__

   611 EXPORT_C

   612 #endif

   613 

   614 guint

   615 gst_adapter_available (GstAdapter * adapter)

   616 {

   617   g_return_val_if_fail (GST_IS_ADAPTER (adapter), 0);

   618 

   619   return adapter->size;

   620 }

   621 

   622 /**

   623  * gst_adapter_available_fast:

   624  * @adapter: a #GstAdapter

   625  *

   626  * Gets the maximum number of bytes that are immediately available without

   627  * requiring any expensive operations (like copying the data into a 

   628  * temporary buffer).

   629  *

   630  * Returns: number of bytes that are available in @adapter without expensive 

   631  * operations

   632  */

   633 #ifdef __SYMBIAN32__

   634 EXPORT_C

   635 #endif

   636 

   637 guint

   638 gst_adapter_available_fast (GstAdapter * adapter)

   639 {

   640   g_return_val_if_fail (GST_IS_ADAPTER (adapter), 0);

   641 

   642   /* no buffers, we have no data */

   643   if (!adapter->buflist)

   644     return 0;

   645 

   646   /* some stuff we already assembled */

   647   if (adapter->assembled_len)

   648     return adapter->assembled_len;

   649 

   650   /* we cannot have skipped more than the first buffer */

   651   g_assert (GST_BUFFER_SIZE (adapter->buflist->data) > adapter->skip);

   652 

   653   /* we can quickly get the data of the first buffer */

   654   return GST_BUFFER_SIZE (adapter->buflist->data) - adapter->skip;

   655 }