The GstBuffer class ::copy() vfunc wrongly creates a new buffer with a GstBuffer GType and the size of a GstBuffer structure, instead of creating a new buffer with the same type and size as the input buffer.

This fails spectactularly in the case of GstNetBuffer from gst-plugins-base, which just chains up to GstBuffer::copy and then copies over some additional fields.

This might have been done on purpose, but I still wonder whether this isn't broken and should be fixed, since it kind of defeats the purpose of sub-classing (copying over the code from the copy vfunc into every subclass doesn't seem like a particularly good idea).

However, changing GstBuffer::copy() to create a new buffer struct of the type and size of the incoming buffer will probably break implementations of read-only buffers that have been built on top of this behaviour (such as GstSubBuffer and GstFileSrcMMapBuffer). The reason this breaks stuff is because ::copy() is used to create a writable buffer.

Possibilities:

 1) declare current behaviour as broken, and use
      copy = gst_mini_object_new (G_TYPE_FROM_INSTANCE (buffer))
    in GstBuffer::copy() and fix up read-only buffer subclasses to
    munge the GType before chaining up to the parent class copy function.
    This might break external uses of read-only buffer subclasses that
    chain up to GstBuffer::copy() though.

 2) just fix GstNetBuffer not to chain up and copy over code from gstbuffer.c

 3) make functionality from GstBuffer::copy() available as new function that
    operates on an already-copied buffer structure, so sub-classes just
    create their own copied buffer instance and then use that new function
    instead of chaining up to the parent class's copy function.

Opinions?