/**
* gst_buffer_span:
* @buf1: the first source #GstBuffer to merge.
* @offset: the offset in the first buffer from where the new
* buffer should start.
* @buf2: the second source #GstBuffer to merge.
* @len: the total length of the new buffer.
*
* Creates a new buffer that consists of part of buf1 and buf2.
* Logically, buf1 and buf2 are concatenated into a single larger
* buffer, and a new buffer is created at the given offset inside
* this space, with a given length.
*
* If the two source buffers are children of the same larger buffer,
* and are contiguous, the new buffer will be a child of the shared
* parent, and thus no copying is necessary. you can use
* gst_buffer_is_span_fast() to determine if a memcpy will be needed.
*
* MT safe.
* Returns: the new #GstBuffer that spans the two source buffers.
* Returns NULL if the arguments are invalid.
*/
GstBuffer *
gst_buffer_span (GstBuffer * buf1, guint32 offset, GstBuffer * buf2,
guint32 len)
{
GstBuffer *newbuf;
g_return_val_if_fail (buf1 != NULL && buf2 != NULL, NULL);
g_return_val_if_fail (buf1->mini_object.refcount > 0, NULL);
g_return_val_if_fail (buf2->mini_object.refcount > 0, NULL);
g_return_val_if_fail (len > 0, NULL);
g_return_val_if_fail (len <= buf1->size + buf2->size - offset, NULL);
/* if the two buffers have the same parent and are adjacent */
if (gst_buffer_is_span_fast (buf1, buf2)) {
GstBuffer *parent = GST_SUBBUFFER_CAST (buf1)->parent;
/* we simply create a subbuffer of the common parent */
newbuf = gst_buffer_create_sub (parent,
buf1->data - parent->data + offset, len);
} else {
GST_CAT_DEBUG (GST_CAT_BUFFER,
"slow path taken while spanning buffers %p and %p", buf1, buf2);
/* otherwise we simply have to brute-force copy the buffers */
newbuf = gst_buffer_new_and_alloc (len);
/* copy the first buffer's data across */
memcpy (newbuf->data, buf1->data + offset, buf1->size - offset);
/* copy the second buffer's data across */
memcpy (newbuf->data + (buf1->size - offset), buf2->data,
len - (buf1->size - offset));
}
/* if the offset is 0, the new buffer has the same timestamp as buf1 */
if (offset == 0) {
GST_BUFFER_OFFSET (newbuf) = GST_BUFFER_OFFSET (buf1);
GST_BUFFER_TIMESTAMP (newbuf) = GST_BUFFER_TIMESTAMP (buf1);
/* if we completely merged the two buffers (appended), we can
* calculate the duration too. Also make sure we's not messing with
* invalid DURATIONS */
if (buf1->size + buf2->size == len) {
if (GST_BUFFER_DURATION_IS_VALID (buf1) &&
GST_BUFFER_DURATION_IS_VALID (buf2)) {
/* add duration */
GST_BUFFER_DURATION (newbuf) = GST_BUFFER_DURATION (buf1) +
GST_BUFFER_DURATION (buf2);
}
if (GST_BUFFER_OFFSET_END_IS_VALID (buf2)) {
/* add offset_end */
GST_BUFFER_OFFSET_END (newbuf) = GST_BUFFER_OFFSET_END (buf2);
}
}
}
return newbuf;
}
/* Internal method only. Tries to merge buffers at the head of the queue
* to form a single larger buffer of size 'size'. Only merges buffers that
* where 'gst_buffer_is_span_fast' returns TRUE.
*
* Returns TRUE if it managed to merge anything.
*/
static gboolean
gst_adapter_try_to_merge_up (GstAdapter * adapter, guint size)
{
GstBuffer *cur, *head;
GSList *g;
gboolean ret = FALSE;
g = adapter->buflist;
if (g == NULL)
return FALSE;
head = g->data;
g = g_slist_next (g);
/* How large do we want our head buffer? The requested size, plus whatever's
* been skipped already */
size += adapter->skip;
while (g != NULL && GST_BUFFER_SIZE (head) < size) {
cur = g->data;
if (!gst_buffer_is_span_fast (head, cur))
return ret;
/* Merge the head buffer and the next in line */
GST_LOG_OBJECT (adapter,
"Merging buffers of size %u & %u in search of target %u",
GST_BUFFER_SIZE (head), GST_BUFFER_SIZE (cur), size);
head = gst_buffer_join (head, cur);
ret = TRUE;
/* Delete the front list item, and store our new buffer in the 2nd list
* item */
adapter->buflist = g_slist_delete_link (adapter->buflist, adapter->buflist);
g->data = head;
/* invalidate scan position */
adapter->priv->scan_offset = 0;
adapter->priv->scan_entry = NULL;
g = g_slist_next (g);
}
return ret;
}
