Module cheat 

SNES cheat-code decoding: Game Genie and Pro Action Replay (v0.8.0 "Instrumentation", T-81-003).

Ported from bsnes’s CheatEditor::decodeSNES (ref-proj/bsnes/bsnes/target-bsnes/tools/ cheat-editor.cpp) and cross-checked bit-for-bit against Mesen2’s independent CheatManager::ConvertFromSnesGameGenie/ConvertFromSnesProActionReplay (ref-proj/Mesen2/Core/Shared/CheatManager.cpp) — both codebases compute an identical 24-bit address and value byte for any given code string. Test vectors below are real commercial codes drawn from Mesen2’s shipped cheat database (ref-proj/Mesen2/UI/Dependencies/Internal/ CheatDb.Snes.json), decoded independently by hand against the bit formula as a third check.

Both formats decode to a plain 24-bit CPU-bus address ($bank:offset) plus an 8-bit substitute value — no LoROM/HiROM bank translation happens here (that is the Bus’s normal memory-map job, same as crate::Bus::poke_wram/crate::Bus::peek_wram). Neither SNES format supports a compare byte (unlike NES’s 8-character Game Genie) — a decoded cheat is always an unconditional address/value substitution.

A cheat is host-applied external input, not emulated hardware behavior (docs/adr/0004) — it is not part of any save state and is not evaluated unless the frontend’s cheats feature is on and a patch is actually applied, so the determinism contract is untouched when no cheat is active.

Structs

CheatPatch

A decoded cheat patch: substitute value at CPU-bus address ($bank:offset, 24-bit).

Enums

CheatError

Error decoding a cheat-code string.

Functions

decode

Decode code as a Game Genie code, falling back to Pro Action Replay only when code doesn’t match the Game Genie shape at all.

decode_game_genie

Decode a Game Genie code: XXXX-XXXX (case-insensitive, a dash at index 4, 9 characters total).

decode_pro_action_replay

Decode a Pro Action Replay code: 8 hex digits (case-insensitive), no scrambling — AAAAAADD (6 hex-digit address, high; 2 hex-digit value, low).