Adding a buffer to the end of a GstBufferList is supposed to be a fast
operation, but it was not since the iterator does not advance its
nextpointer when adding buffers and GList does not have a tail pointer.
Using a GQueue to store the buffers makes it easier to add buffers to
the end of the list and this operation will now be much more efficient.
Adding an entire GList of buffers using
gst_buffer_list_iterator_add_list() will however have to iterate over
the list being added to be able to update the tail pointer in the
GQueue.
This is not really necessary here because everything is
initialized from gst_init() already but using G_DEFINE_TYPE()
removes some copy&paste boilerplate code.
This changes some APIs in compatible ways:
- Some functions now take "const char *" arguments, not "char *"
- Some structs now have "conts char *" members, not "char *"
The changes may cause warnings when compiling with the right warning
flags. You've been warned.
Also adds -Wwrite-strings as a warning flag in configure.ac.
https://bugzilla.gnome.org/show_bug.cgi?id=611692
Add new method to iterate a bufferlist without having to allocate an iterator.
Add convenience method for getting an item from the list based on the group and
index.
Remove redundant _do_data callback and method.
Update unit-tests and add some more for the new methods.
Buffer lists are a means to manage disjoint buffers as one buffer. It's also
possible to put many of those buffers into a list.
The idea is that when support is added to various elements, we will be able to
more efficiently slice and dice buffers, reduce the amount of memcpy and also
reduce data passing overhead.
The implementation is kept simple on purpose, reusing all of the memory
management features we have for miniobjects and buffers.
Access to the bufferlist object is done with an iterator, which allows for
efficient iteration and modification of the list.
See #572285
