Ys I/II/Origin/VI extractor

nani.py

import typing as T
from pathlib import Path
import zlib
import struct

try:
	import numpy as np
	def decode(data: bytes) -> bytes:
		data = np.frombuffer(data, dtype=np.ubyte).copy()
		obf = 0x7C53F961 * 0x3D09 ** (1+np.arange(len(data), dtype=np.uint32))
		data -= obf >> 16
		return data.tobytes()
except ImportError:
	print("Could not import numpy — falling back to slow method")
	def decode(data: bytes) -> bytes:
		k = 0x7C53F961
		o = bytearray()
		for b in data:
			k *= 0x3D09
			o.append((b - (k >> 16)) & 0xFF)
		return bytes(o)

def fnhash(name: bytes) -> int:
	return sum(
		(b - 32) * (1<<(i%5*5))
		for i, b in enumerate(name)
	) % 0xFFF1

def extract(na: bytes, ni: bytes, *, verify: bool = False) -> T.Iterator[tuple[str, bytes]]:
	def take(a: bytes, n: int) -> tuple[bytes, bytes]: return a[:n], a[n:]
	head, ni = take(ni, 16)
	head, p2, p3, p4 = struct.unpack("<4sIII", head)
	assert head == b"NNI\0"
	toc, ni = take(ni, p2*16)
	names, ni = take(ni, p3)
	assert p4 & 0x01 == 0, ".\\core\\nnk_file.cpp: vfs::Startup: No incremental linking support."
	assert not ni

	toc = decode(toc)
	names = decode(names)

	for hash, size, pos, namepos in struct.iter_unpack("<IIII", toc):
		name = names[namepos:names.find(b"\0", namepos)]
		if verify: assert hash == fnhash(name), name
		name = name.decode("cp932").lower().replace("\\", "/")

		if (pos, size) == (0, 0):
			print(f"skipping blank file {name}")
			continue

		data = na[pos:pos+size]
		if name.endswith(".z"):
			name = name[:-2]
			try:
				checksum, usize = struct.unpack("<II", data[:8])
				data = zlib.decompress(data[8:])
				assert len(data) == usize
				if verify: assert checksum == zlib.crc32(data)
			except Exception:
				print(f"failed to decompress {name}")
				import traceback
				traceback.print_exc()
		yield name, data

import argparse
argp = argparse.ArgumentParser()
argp.add_argument("-o", "--outdir", type=Path, required=True, dest="outdir")
argp.add_argument("-v", "--verbose", action="store_true")
argp.add_argument("-V", "--verify", action="store_true")
argp.add_argument("files", nargs="+", type=Path)
def __main__(outdir: Path, verbose: bool, verify: bool, files: list[Path]):
	for path in files:
		assert path.suffix in [".na", ".ni"], path
		na = path.with_suffix(".na").read_bytes()
		ni = path.with_suffix(".ni").read_bytes()
		for name, data in extract(na, ni, verify=verify):
			out = outdir / name
			if verbose: print(out)
			out.parent.mkdir(parents=True, exist_ok=True)
			out.write_bytes(data)
if __name__ == "__main__":
	__main__(**argp.parse_args().__dict__)