Inserts the memory block mem into this at idx.
This function takes ownership of mem and thus doesn't increase its refcount.
Only buffer_get_max_memory can be added to a buffer. If more memory is added, existing memory blocks will automatically be merged to make room for the new memory.
| this |
a Buffer. |
| idx |
the index to add the memory at, or -1 to append it to the end |
| mem |
a Memory. |