Iga Ninden Gaiou text extraction (unfinished)

iga_ninden_gaiou_text.py

# Files:
# Iga Ninden Gaiou (Japan).chd CRC32 1243A2DE
#
# Use chdman to extractcd:
# ing.bin CRC32 07E9BA8D

romin = "ing.bin"
romout = "inge.bin"

rom = open(romin,"rb").read()

# check to try to sort out real text from garbage
def text_check(s):
    return any(c in s for c in ["う","ん","い","し","。","？"]) # most common 4 hiragana + punctuation

# standard PCE text encoding seems to be a variant of shift_jisx0213
# probably need to add a bunch of special cases as well
def decode_range(rom,i,span=64):
    s = rom[i:i+span]
    d = s.decode(encoding="shift_jisx0213",errors="backslashreplace")
    return d

# decodes a block of the file and prints it
def view_range(rom,i,span=64,check=False):
    d = decode_range(rom,i,span)
    if not check or text_check(d):
        print("%08X: %s" % (i,d))

# views a range of blocks from the file, every block at 2 offsets
# (characters are 2-byte but can start/stop on 1-byte offsets)
def check_range(rom,start,end,span=64,check=True):
    print("check_range(%08X,%08X)" % (start,end))
    for i in range(start,end,span):
        view_range(rom,i+0,span,check)
        view_range(rom,i+1,span,check)
    print("done.")

# views a group of strings, terminated/separated by a 0 byte
def view_group(rom,i,end=-1):
    print("view_group(%08X)" % i)
    while (end<0) or (i<end):
        e = rom.index(0,i) # search for next 0 to mark end of string
        if (e-i) < 2: # all characters are 2-byte?
            break
        d = decode_range(rom,i,e-i)
        print("%08X: [%s]" % (i,d))
        i = e+1
    print("end %08X" % i)

# replace bytes in ROM with an encoded string
# (probably need to deal with groups of 0 terminated strings?)
def inject_string(rom,i,s):
    b = bytearray()
    for c in s:
        if c == "\n": # is this how the game does newlines?
            b.append(0x02)
            b.append(0x06)
            b.append(0x90)
        else:
            b.extend(c.encode(encoding="shift_jisx0213"))
    for j in range(len(b)):
        rom[i+j] = b[j]
    rom[i+len(b)] = 0

# examples to explore ROM
##check_range(rom,0,len(rom)) # explore entire ROM, only recognized text
##check_range(rom,0x0080DA56,0x00810AB5) # explore range, only recognized text
##check_range(rom,0x0080DA56,0x00810AB5,64,False) # explore range, all as text

# suspicious areas that seem to contain text
# (use view_group to find the exact location and break these down)
##check_range(rom,0x0080D700,0x00820000)
##check_range(rom,0x008266C0,0x00826800)
##check_range(rom,0x0086EA40,0x00890400)
##check_range(rom,0x00FA0780,0x00FA5000)
##check_range(rom,0x240C0200,0x240EE400)
##check_range(rom,0x2487AD00,0x2487AE00)

# bits of text groups found via check_range
view_group(rom,0x0080D730)
view_group(rom,0x00810AB5)
# TODO group 0x008266C0,0x00826800
view_group(rom,0x0086EA47,0x0086EBA0)
view_group(rom,0x0086EBA3)
view_group(rom,0x0086F181)
view_group(rom,0x008743CB,0x874424)
view_group(rom,0x00876001)
view_group(rom,0x00876464)
view_group(rom,0x008764C2)
view_group(rom,0x00876614)
view_group(rom,0x00876664)
view_group(rom,0x0087669F)
view_group(rom,0x00876711)
view_group(rom,0x00876886)
view_group(rom,0x00876909)
view_group(rom,0x00876A45)
# there's still a lot more in 0x0086EA40,0x00890400

# there are duplicates of some things, e.g.:
view_group(rom,0x0086EBA3)
view_group(rom,0x00FA3B13)
view_group(rom,0x240C2C5D)

# now let's try to modify it
rom = bytearray(rom) # modifyable
#inject_string(rom,0x0086EBA3+0x1C,"Ｉｓ　ｔｈｉｓ？")
inject_string(rom,0x00FA3B13,"Ｈｏｗ　ａｒｅ　ｙｏｕ\nｇｅｎｔｌｅｍｅｎ？")
#inject_string(rom,0x240C2C5D+0x1C,"Ｗｈａｔ　ｔｈｅ？")
view_group(rom,0x00FA3B13)
open(romout,"wb").write(rom)
print("%s written (%d bytes)" % (romout,len(rom)))