A savestate is whole-machine state. One taken on disc 2 and restored while
disc 1 is mounted resumes a guest that still believes it is reading disc 2,
and the slot list gives no hint: every disc of a set shares one entry_pc, and
entry_pc is the key the slot filenames already use. So the same slot number
meant a different machine on every disc, silently.
Savestates were already isolated per BIOS, as a directory. The disc joins that
as a FILENAME token inside it:
<saves>/<bios>/state_<entry>_disc<N>_slot<NN>.pst
The BIOS stays a directory because a state is invalid across BIOS images
whatever disc it came from. The disc only has to not collide within one, and a
token does that without another level to browse, back up and migrate.
An empty token leaves the historical name byte-for-byte, so single-disc titles
keep every existing state -- the scope is set only when the roster has more
than one disc.
States saved before this predate the naming and are not listed. They are left
alone rather than migrated: nothing in a .pst says which disc it was taken on,
so placing them would be a guess, and guessing wrong reintroduces exactly the
mix-up this prevents. Startup names them and the directory so they can be
renamed deliberately.
Verified: slot 1 saved on disc 2 and on disc 3 produced disc2/disc3 files side
by side with no collision; booting disc 1 and loading slot 1 rejected with
"missing state_800110C0_disc1_slot01.pst" rather than restoring another disc's
machine; the pre-existing untagged slot 0 was untouched throughout.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0194TYJAqgyG9a9PJe9uUcgQ
Alex Vanderveen
a44fb12575