Closes the round trip. Gold, Silver and Crystal progress writes back to a
cartridge save the real game boots.
Writes into the image the save came from. Gen 2 SRAM holds a great deal
this codec does not model and the real game trusts it on CONTINUE, so a
save with no cartridge behind it is refused rather than built from nothing.
That refusal is the known limitation: a game begun in this project has no
lineage to write back into yet.
The image lives BESIDE the slot as saves/<version>/<id>.cart, not in the
save table. 32 KB of binary in the serialized table is 40 KB of Lua source
reparsed on every save and load, for every imported slot, forever.
Only the primary copy is written. TryLoadSaveFile rewrites the backup from
the primary the moment VerifyChecksum passes, so a stale backup heals
itself on the first load and this does not need a second offset mapping.
Crystal arranges its backup differently from Gold and Silver, so that
matters.
What encode now reaches that it did not:
* the bag, all four pockets, bucketed by each item's own pocket, plus
wCurBox and the box names. It used to leave them at whatever the
template carried, so a potion bought in a session never arrived.
* the RTC footer. importToSlot truncates to 32768, so the image is kept
at its full length and the footer is carried through. Dropping it
resets the clock and costs the player daily events, the bug contest
and a clock-adjustment penalty.
* 0x1C-0x1E, pokerus and caught data. Left to the template they survive
POSITIONALLY, so reordering the party gives slot 1 the previous
occupant's caught level and location.
A bag that cannot be bucketed is refused rather than written short: without
the item table every item falls into ITEM, which holds 20, and a real bag
is bigger than that. Silently dropping the overflow would be worse than
the bug this fixes.
Two bugs in the text encoder that only real names caught: the cart's table
carries the ligature halves PO and KE, so a name containing "PO" became
0x70 where the cart had a plain P; and #glyph counts BYTES in Lua, so every
multi-byte glyph was dropped and came back as "?", which is NIDORAN and
every name with an accent.
Tests
The round trip CHANGES things first, in each place export has to reach, and
reads them back through a fresh decode. Exporting onto the buffer a save was
decoded from proves nothing, because every region encode does not write
matches by construction.
The fixture-gated audit exports a real cart save too, and pins that the
image keeps its size, RTC and all.
./scripts/test.sh passes end to end, and luacheck is clean.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Gold, Silver and Crystal battery saves import now. Export is still refused.
GenSave.lua is pokered's SRAM window and nothing else, which is why the
guard refusing Gen 2 was right to be there. This adds Gen2Save.lua beside
it, covering pokegold and pokecrystal.
Every offset is generated, not transcribed. tools/gen2_sram_offsets.py
reads pokegold.sym and pokecrystal.sym from a pret build and emits
Gen2Layout.lua, including the text table from constants/charmap.asm and
Crystal's backup-save layout. Gen 2 copies a contiguous WRAM block into
SRAM bank 1, so a field's file offset is sPlayerData + (wField -
wPlayerData); the generator asserts that relation against sPokemonData
rather than assuming it, and range-guards anything outside
sGameData..sGameDataEnd.
Gold and Crystal are separate tables because they disagree about nearly
every field. Reading a Crystal save with Gold's numbers gives a party
count of 133 and 13113 hours played, with a checksum that validates.
The cart stores numbers and the engine is keyed by name, so the codec
crosswalks species, moves and items through the generated tables the same
way GenSave.crosswalks does for Gen 1. Without that, an import looks
perfect and the engine cannot read a byte of it.
Shapes that have to match what the engine reads:
* events is byte index -> packed byte, which Save.scrubEvents validates
with tonumber. A set of booleans is silently emptied.
* the bag is one flat save.inventory keyed by item id, which PackMenu
buckets by each item's pocket. Nothing reads save.keyItems or
save.balls, and the TM/HM pocket lands here too.
* position carries the map id, or Save.summary falls through to
save.spawn and the player resumes somewhere else at their old
coordinates.
* mon.status is an ItemEffects.STATUS_CLASS key with statusTurns beside
it, nil when healthy. 0 is truthy in Lua.
A save the real cartridge would open is not refused: TryLoadSaveFile falls
back to VerifyBackupChecksum, so this does too. Crystal's backup is
contiguous and laid out like the primary; Gold and Silver split theirs
across three sections and have none to offer.
Three suites that pinned Gen 2 import being refused now pin what refuses
instead. Tests live in tests/engine so the ROM-free tier actually runs
them.
./scripts/test.sh passes end to end, and luacheck is clean.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
bryanthaboi