We recently started using blenloader code in blendthumb to avoid having to
reimplement some parts of .blend file parsing. While this works, it has the side
effect that on Windows referencing blenloader code increased the binary size of
blendthumb from < 1MB to ~75 MB. That happens because this dependency drags
along lots of other code which effectively is unused, but the compiler is unable
to remove it.
There didn't seem to be a simple solution to make msvc optimize the unused code
away. This patch solves the issue by extracting the shared code into a separate
`blenloader_core` module which does not depend on the rest of Blender (except
blenlib). Therefore, using this new module in blendthumb does not drag along all
the other dependencies, bring its file size back down.
In the future, more code may be moved from blenloader to blenloader_core, but
for now I extracted these two headers:
* `BLO_core_bhead.hh`: Various `BHead` types and related parsing functions.
* `BLO_core_blend_header.hh`: Parsing of the header at the beginning of .blend
files.
Pull Request: https://projects.blender.org/blender/blender/pulls/138371
ed29ab303c