mirror of
https://github.com/jkdansereau/goldeneye-pc-port.git
synced 2026-10-24 00:02:45 +02:00
James Dansereau
f1e2c7cbb8
v0.3.0 silently wiped all v0.2.x saves on first launch: stored slot CRCs are fingerprints of the PRNG that wrote them, and D284 changed the PRNG. One-time migration in the eeprom shim's read path (block 4 only): a slot that fails the current-CRC check but validates under the legacy PRNG is re-stamped with current-PRNG checksums before fileValidateSaves sees it, then persisted once. Runs before geEepromPatchAllCheats so cheat patches never reach the file. Corrupt/fresh slots untouched (game's own wipe path). - port/src/legacycrc.c: isolated file carrying the deliberately-wrong pre-D284 PRNG (verbatim from 0de99b4d^, reviewer-verified bit-exact) + lockstep copy of the crc.c loop; header says when it may be deleted. - tools_pc/d295_crc.py: reference CRC model, bit-exact vs compiled C for both PRNGs (used to verify migrated files). Verified: user's #87 artifact migrates 5/5 slots with progress intact and is idempotent on relaunch; native post-fix saves, corrupt slots, and fresh eeps all behave per design; 21/21 sweep PASS.
85 lines
3.6 KiB
Python
85 lines
3.6 KiB
Python
#!/usr/bin/env python3
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"""D295/M-148: reproduce fileGenerateCRC (src/game/crc.c) with both the pre-D284
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(buggy, shipped in v0.2.x) and post-D284 (HEAD) PRNG semantics, verify against the
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user's saved slot CRCs, and emit a patched eep whose slots carry POST-FIX CRCs so
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a HEAD build accepts them (proves the difficultytext overflow is still live).
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Save layout in ge007.eep (verified M-148):
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bytes 0..31 : smallSave header (block 0)
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slot i : file offset 32 + i*96, i = 0..5 (sizeof(save_data)=96, padded)
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slot fields : c1(s32) c2(s32) bitflags(1) flag_007(1) music(1) sfx(1)
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options(2) cheats(3) pad(1) times[76]
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CRC region : &completion_bitflags .. save+1 => slot bytes [8..96), 88 bytes.
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"""
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import struct, sys
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M64 = (1 << 64) - 1
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def make_rng(buggy: bool):
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def dsll32(x, n):
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if buggy: return (x << n) & 0xFFFFFFFF
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return (x << (n + 32)) & M64
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def dsrl32(x, n):
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if buggy: return (x >> n) & 0xFFFFFFFF
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return x >> (n + 32)
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def step(seed: int) -> int:
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# Mirrors randomGetNextFrom line-by-line. NOTE the plain dsrl/dsll lines
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# (a2 >>= 31, a1 = a3 << 31, a2 >>= 20) are NOT the *32 helpers.
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a3 = seed & M64
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a2 = dsll32(a3, 0x1F) >> 0x1F # dsll32 then plain dsrl 31
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a1 = dsrl32((a3 << 0x1F) & M64, 0) # plain dsll 31 then dsrl32 0
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a3 = dsrl32(dsll32(a3, 0xC), 0) # dsll32 then dsrl32 0
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a2 = (a2 | a1) ^ a3
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a3 = ((a2 >> 0x14) & 0xFFF) ^ a2 # plain dsrl 20, andi, xor
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return a3 & M64
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return step
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def file_generate_crc(data: bytes, buggy: bool):
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"""Mirror crc.c exactly: shift is NOT reset between the two passes."""
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step = make_rng(buggy)
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poly = 0x8F809F473108B3C1 & M64
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c1 = 0; c2 = 0; shift = 0
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for b in data: # forward pass, +7/byte
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poly = (poly + ((b << (shift & 0xF)) & M64)) & M64
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shift += 7
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poly = step(poly) # randomGetNextFrom updates the seed IN PLACE
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c1 ^= poly & 0xFFFFFFFF
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for b in reversed(data): # backward pass, +3/byte, shift continues
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poly = (poly + ((b << (shift & 0xF)) & M64)) & M64
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shift += 3
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poly = step(poly)
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c2 ^= poly & 0xFFFFFFFF
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return c1 & 0xFFFFFFFF, c2 & 0xFFFFFFFF
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def main():
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src = sys.argv[1] if len(sys.argv) > 1 else r"C:\Users\james\Downloads\ge-issue87-artifacts\ge007.eep"
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dst = sys.argv[2] if len(sys.argv) > 2 else None
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eep = bytearray(open(src, "rb").read())
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assert len(eep) == 2048, len(eep)
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print("slot | stored c1,c2 | oldPRNG c1,c2 | newPRNG c1,c2 | old? new?")
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ok_old = ok_new = True
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for i in range(5):
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off = 32 + i * 96
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sc1, sc2 = struct.unpack_from("<II", eep, off)
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region = bytes(eep[off + 8: off + 96])
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oc1, oc2 = file_generate_crc(region, buggy=True)
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nc1, nc2 = file_generate_crc(region, buggy=False)
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o = (oc1, oc2) == (sc1, sc2); n = (nc1, nc2) == (sc1, sc2)
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ok_old &= o; ok_new &= n
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print(f" {i} | {sc1:08x},{sc2:08x} | {oc1:08x},{oc2:08x} | {nc1:08x},{nc2:08x} | {o=} {n=}")
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print(f"old PRNG matches all 5 stored CRCs: {ok_old}")
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print(f"new PRNG matches all 5 stored CRCs: {ok_new}")
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if dst:
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for i in range(5):
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off = 32 + i * 96
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region = bytes(eep[off + 8: off + 96])
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nc1, nc2 = file_generate_crc(region, buggy=False)
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struct.pack_into("<II", eep, off, nc1, nc2)
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open(dst, "wb").write(eep)
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print(f"patched (post-fix CRCs, slots 0-4) -> {dst}")
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if __name__ == "__main__":
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main()
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