Show LFN and SFN like ls on FAT12/16 (Support UTF-8/UTF-16 file name)

fat_ls.py

#!/usr/bin/env python3
import struct
from sys import argv

UTF8_prior = False
#FILENAME = input('img name?: ')
FILENAME = argv[1]

def getLFN(ldir_wholename):
    ldir_wholename = ldir_wholename.replace(b'\xff\xff',b'')    #remove padding
    ldir_utf8name = ldir_wholename.replace(b'\0',b'')   #UTF8だと想定してnull文字削除
    if not UTF8_prior:
        try:
            ldir_strname = ldir_wholename.decode('utf_16_le')
        #UTF8だった場合
        except UnicodeDecodeError:
            ldir_strname = ldir_utf8name.decode('utf_8')
    else:
        try:
            ldir_strname = ldir_utf8name.decode('utf_8')
        #UTF16だった場合
        except UnicodeDecodeError:
            ldir_strname = ldir_wholename.decode('utf_16_le')
    return ldir_strname

data = open(FILENAME, 'rb').read()

BytesPerSec, SecPerClus, RsvdSecCnt, NumFATs, FATSize = struct.unpack_from(b'< 3x 8x H B H B 2x 2x x H', data)

dir_start = BytesPerSec * (RsvdSecCnt + FATSize * NumFATs) #BPB+FAT*2 0x600
entry_size = 32
saved_data = b''
delLFNContinue = False

while True:
    name, attr = struct.unpack_from(b'< 11s c', data, dir_start)
    if name==b'\x00'*11:
        break
    if attr==b'\x0f':   #LFN
        LDIR_Ord, LDIR_Name1, LDIR_Chksum, LDIR_Name2, LDIR_Name3 = struct.unpack_from(b'< B 10s x x c 12s 2x 4s', data, dir_start)

        ldir_rawname = LDIR_Name1 + LDIR_Name2 + LDIR_Name3

        #16進の一の位が1以外なら連続なので連結
        ord_hex = format(LDIR_Ord, 'x')
        if len(ord_hex) == 1:   #2桁化
            ord_hex = '0' + ord_hex
        if ord_hex[1]!='1' and ord_hex!='e5':  #e5は削除済みファイル
            saved_data = ldir_rawname + saved_data
        #削除済みLFNはどこまでか判定できないのでとりえあずスタックする
        elif ord_hex=='e5':
            saved_data = ldir_rawname + saved_data
            delLFNContinue = True
        else:
            ldir_wholename = ldir_rawname + saved_data
            saved_data = b''
            ldir_strname = getLFN(ldir_wholename)
            print('LFN: '+ldir_strname)
        
    else:   #SFN
        #削除済みLFNが終わったことを確認
        if delLFNContinue:
            delLFNContinue = False
            ldir_wholename = saved_data
            saved_data = b''
            ldir_strname = getLFN(ldir_wholename)
            print('LFN: '+ldir_strname,' (DELETED)')
        try:
            if name[0:1]==b'\xe5':  #一文字目が削除フラグ0xE5か
                print('SFN: ?'+name[1:].decode('ascii'),' (DELETED)')
            else:
                print('SFN: '+name.decode('ascii'))
        except UnicodeDecodeError:
            print('SFN: (decoding failed)')
        print()
    
    dir_start += entry_size