common.py

#!/usr/bin/env python3

import sys
import struct
import json
import re
from collections import namedtuple

OverlayInfo = namedtuple("OverlayInfo", ["sector_start", "block_size", "filename"])

def extract_overlay(silent: memoryview, ovi: OverlayInfo):
    start = (ovi.sector_start - 0x40) * 0x800
    size  = ovi.block_size * 0x100

    return silent[start: start+size]

#based on https://github.com/Vatuu/silent-hill-decomp/blob/master/tools/silentassets/extract.py
def xorBodyprog(silent: memoryview):
    bodyprog = extract_overlay(silent, BodyProg)
    outArray = bodyprog.cast("I") # uint32_t
    seed = 0

    for i, value in enumerate(outArray):
        seed = (seed + 0x01309125) & 0xffffffff
        seed = (seed * 0x03a452f7) & 0xffffffff
        outArray[i] ^= seed

    return bodyprog

def read_uint32_le(buf, offset):
    return struct.unpack_from('<I', buf, offset)[0]

def read_c_string(data: memoryview, offset: int) -> str:
    end = offset
    while end < len(data) and data[end] != 0:
        end += 1
    return data[offset:end].tobytes().decode('ascii')

def patch_blob(dstblob, srcblob, offset):
    bloblen = len(srcblob)
    dstblob[offset: offset + bloblen] = srcblob

def patch_pointer(dstblob, pointer, offset):
    srcblob = struct.pack('<I', pointer)
    patch_blob(dstblob, srcblob, offset)

def encode_local_text(line):
    line = line.replace('ł', ';').replace('ó', '*').replace('ę', '>').replace('ą', '^')
    line = line.replace('ż', '=').replace('ć', '<').replace('ń', '+').replace('ś', '/').replace('ź', 'Q')
    return line