Nguyễn Thái Ngọc Duy <[email protected]> writes:
> Notice that packing_data::nr_objects is uint32_t, we could only handle
> maximum 4G objects and can address all of them with an uint32_t. If we
> use a pointer here, we waste 4 bytes on 64 bit architecture.
Some things are left unsaid or left unclear and make readers stutter
a bit while reading this paragraph. We can address them with
uint32_t only because we happen to have a linear array of all
objects involved already, i.e. the pack->objects[] array. The
readers are forced to rephrase the above in their mind
... and each of them can be identified with an uint32_t.
Because we have all of these objects in pack->objects[], we
can replace the "delta" field in each object entry that
points at its delta base object with uint32_t index into
this array to save memory (on 64-bit arch, 8-byte pointer
gets shrunk to 4-byte uint).
or something like that before understanding why this is a valid
memory footprint optimization.
