Hatsukoi 1/1 NoCD patch applier / reverter

hatsukoi_1_-_1_tone_works_apply_nocd_patch.py

#!/usr/bin/env python3
"""Hatsukoi 1/1 NoCD patch - applier / reverter.

Forces the engine's disc-presence check (FUN_005f4500) to always report
"disc present" by overwriting its entry prologue with `mov al,1 ; ret`.

Keep THIS file (a few KB) instead of the 8.5 MB patched exe. After a reinstall,
run it against the fresh original SiglusEngine.exe to re-apply.

Usage:
    python apply_nocd_patch.py [apply|revert|check] [path-to-SiglusEngine.exe]

  - no path  -> looks for SiglusEngine.exe next to this script, then in the
                parent folder (i.e. the game dir, if this file lives in _nocd_backup).
  - if action is omitted, it defaults to "apply".
"""
import os, sys, hashlib

OFFSET   = 0x1F3900                     # .text file offset; VMA 0x5F4500
ORIG     = bytes([0x55, 0x8B, 0xEC])    # push ebp ; mov ebp,esp
PATCHED  = bytes([0xB0, 0x01, 0xC3])    # mov al,1 ; ret
# 13-byte build signature that follows the 3 patched bytes (unchanged by the
# patch). Used to confirm we're looking at the known build before writing.
ANCHOR_TAIL = bytes([0x6A, 0xFF, 0x68, 0x2C, 0x6C, 0x97, 0x00,
                     0x64, 0xA1, 0x00, 0x00, 0x00, 0x00])
# This is the English patched executable from https://tsurezurescans.wordpress.com/2018/09/27/hatsukoi-1-1-full-english-patch-main-game-append-scenarios/
ORIG_SHA256 = "2e48aa40b5f0db720c1f520effd4b39e364ecf16a66ed0611a991d49a513e8d3"

def find_exe():
    here = os.path.dirname(os.path.abspath(__file__))
    parent = os.path.dirname(here)
    cands = []
    # If this script lives in _nocd_backup\, the real game exe is one level up;
    # prefer it over the pristine backup copy that sits next to this script.
    if os.path.basename(here).lower() == "_nocd_backup":
        cands.append(os.path.join(parent, "SiglusEngine.exe"))
    cands.append(os.path.join(here, "SiglusEngine.exe"))
    cands.append(os.path.join(parent, "SiglusEngine.exe"))
    for cand in cands:
        if os.path.isfile(cand):
            return cand
    return None

def state(data):
    window = data[OFFSET:OFFSET + 16]
    if len(window) < 16 or window[3:16] != ANCHOR_TAIL:
        return "unknown"          # not the known build (updated/different exe)
    head = window[0:3]
    if head == PATCHED:
        return "patched"
    if head == ORIG:
        return "original"
    return "unexpected"

def main():
    args = [a for a in sys.argv[1:]]
    action = "apply"
    path = None
    for a in args:
        if a in ("apply", "revert", "check"):
            action = a
        else:
            path = a
    if path is None:
        path = find_exe()
    if not path or not os.path.isfile(path):
        sys.exit("ERROR: SiglusEngine.exe not found. Pass its path as an argument.")

    data = bytearray(open(path, "rb").read())
    st = state(data)
    sha = hashlib.sha256(data).hexdigest()
    print("target : %s" % path)
    print("state  : %s   (sha256 %s%s)" % (
        st, sha[:16], " == known-original" if sha == ORIG_SHA256 else ""))

    if st == "unknown":
        sys.exit("ABORT: bytes at 0x%X don't match the known build. This is likely a\n"
                 "       different/updated SiglusEngine.exe. Not touching it to avoid\n"
                 "       corruption. (Expected tail %s)" % (OFFSET, ANCHOR_TAIL.hex(" ")))
    if st == "unexpected":
        sys.exit("ABORT: unexpected bytes at the patch site; refusing to write.")

    if action == "check":
        print("OK (no changes made).")
        return

    if action == "apply":
        if st == "patched":
            print("Already patched. Nothing to do.")
            return
        data[OFFSET:OFFSET + 3] = PATCHED
        open(path, "wb").write(data)
        print("PATCHED: wrote %s at 0x%X (NoCD active)." % (PATCHED.hex(" "), OFFSET))
        return

    if action == "revert":
        if st == "original":
            print("Already original. Nothing to do.")
            return
        data[OFFSET:OFFSET + 3] = ORIG
        open(path, "wb").write(data)
        print("REVERTED: wrote %s at 0x%X (original disc check restored)." % (ORIG.hex(" "), OFFSET))
        return

if __name__ == "__main__":
    main()