machfs/machfs/main.py

633 lines
24 KiB
Python

import struct
from macresources import Resource, make_file, parse_file
from . import btree, bitmanip
from .directory import AbstractFolder, Folder, File
def _catalog_rec_sort(b):
order = [
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
0x20, 0x22, 0x23, 0x28, 0x29, 0x2a, 0x2b, 0x2c,
0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36,
0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e,
0x3f, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46,
0x47, 0x48, 0x58, 0x5a, 0x5e, 0x60, 0x67, 0x69,
0x6b, 0x6d, 0x73, 0x75, 0x77, 0x79, 0x7b, 0x7f,
0x8d, 0x8f, 0x91, 0x93, 0x96, 0x98, 0x9f, 0xa1,
0xa3, 0xa5, 0xa8, 0xaa, 0xab, 0xac, 0xad, 0xae,
0x54, 0x48, 0x58, 0x5a, 0x5e, 0x60, 0x67, 0x69,
0x6b, 0x6d, 0x73, 0x75, 0x77, 0x79, 0x7b, 0x7f,
0x8d, 0x8f, 0x91, 0x93, 0x96, 0x98, 0x9f, 0xa1,
0xa3, 0xa5, 0xa8, 0xaf, 0xb0, 0xb1, 0xb2, 0xb3,
0x4c, 0x50, 0x5c, 0x62, 0x7d, 0x81, 0x9a, 0x55,
0x4a, 0x56, 0x4c, 0x4e, 0x50, 0x5c, 0x62, 0x64,
0x65, 0x66, 0x6f, 0x70, 0x71, 0x72, 0x7d, 0x89,
0x8a, 0x8b, 0x81, 0x83, 0x9c, 0x9d, 0x9e, 0x9a,
0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0x95,
0xbb, 0xbc, 0xbd, 0xbe, 0xbf, 0xc0, 0x52, 0x85,
0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 0xc8,
0xc9, 0xca, 0xcb, 0x57, 0x8c, 0xcc, 0x52, 0x85,
0xcd, 0xce, 0xcf, 0xd0, 0xd1, 0xd2, 0xd3, 0x26,
0x27, 0xd4, 0x20, 0x4a, 0x4e, 0x83, 0x87, 0x87,
0xd5, 0xd6, 0x24, 0x25, 0x2d, 0x2e, 0xd7, 0xd8,
0xa7, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
]
b = b[0] # we are only sorting keys!
return b[:4] + bytes(order[ch] for ch in b[5:])
def _suggest_allocblk_size(volsize, minalign):
min_nonalloc_blks = 6 # just for this estimation
retval = minalign
while volsize - min_nonalloc_blks*512 > retval*65536:
retval += minalign
return retval
def _get_every_extent(nblocks, firstrecord, cnid, xoflow, fork):
accum = 0
extlist = []
for a, b in btree.unpack_extent_record(firstrecord):
if not b: continue
accum += b
extlist.append((a, b))
while accum < nblocks:
nextrecord = xoflow[cnid, fork, accum]
for a, b in btree.unpack_extent_record(nextrecord):
if not b: continue
accum += b
extlist.append((a, b))
return extlist
def _encode_name(name, kind='file'):
longest = {'file': 31, 'vol': 27, 'bb': 15}[kind]
try:
encoded = name.encode('mac_roman')
except UnicodeEncodeError:
raise BadNameError(name)
except AttributeError:
pass
if not 1 <= len(encoded) <= longest or b':' in encoded:
raise BadNameError(name)
return encoded
def _bb_name(name):
return bitmanip.pstring(_encode_name(name)).ljust(16)
def _common_prefix(*tuples):
for i in range(min(len(t) for t in tuples)):
for t in tuples[1:]:
if t[i] != tuples[0][i]:
return i
return 0
def _link_aliases(vol_cr_date, cnid_dict): # vol creation date confirms within-volume alias
for cnid, obj in cnid_dict.items():
try:
if obj.flags & 0x8000:
alis_rsrc = next(r.data for r in parse_file(obj.rsrc) if r.type == b'alis')
# print(hex(obj.flags))
# print(obj)
# open('/tmp/interpreting' + hex(cnid),'wb').write(alis_rsrc)
userType, aliasSize, aliasVersion, \
thisAliasKind, volumeName, volumeCrDate, \
volumeSig, volumeType, parDirID, fileName, \
fileNum, fileCrDate, fileType, fdCreator, \
nlvlFrom, nlvlTo, volumeAttributes, volumeFSID \
= struct.unpack_from('>4s H hh 28p L 2s hL 64p LL 4s4s HHLh', alis_rsrc)
# print(userType, aliasSize, aliasVersion,
# thisAliasKind, volumeName, volumeCrDate,
# volumeSig, volumeType, parDirID, fileName,
# fileNum, fileCrDate, fileType, fdCreator,
# nlvlFrom, nlvlTo, volumeAttributes, volumeFSID)
if volumeCrDate != vol_cr_date: raise ValueError
obj.aliastarget = cnid_dict[fileNum]
except (AttributeError, KeyError, StopIteration, ValueError):
pass
def _defer_special_files(iter_paths):
"""Defer special files (aliases) to late CNIDs, and resolve aliases"""
approved_dict = dict()
unapproved = []
for path, obj in iter_paths:
if isinstance(obj, File) and obj.aliastarget is not None:
unapproved.append((path, obj))
else:
yield path, obj, None
approved_dict[id(obj)] = path
while unapproved:
made_progress = False
for i in reversed(range(len(unapproved))):
path, obj = unapproved[i]
try:
targetpath = approved_dict[id(obj.aliastarget)]
except KeyError:
continue
yield path, obj, targetpath
approved_dict[id(obj)] = path
unapproved.pop(i)
made_progress = True
if not made_progress: break
def _alis_append(alis, kind, data):
if len(alis) % 2: alis.append(0)
alis.extend(struct.pack('>hH', kind, len(data)))
alis.extend(data)
if len(alis) % 2: alis.append(0)
class _TempWrapper:
"""Volume uses this to store metadata while serialising"""
def __init__(self, of):
self.of = of
class OutOfSpaceError(Exception):
pass
class BadNameError(Exception):
pass
class Volume(AbstractFolder):
def __init__(self):
super().__init__()
self.crdate = self.mddate = self.bkdate = 0
self.name = 'Untitled'
def read(self, from_volume):
for i in range(0, len(from_volume), 512):
if from_volume[i+1024:i+1024+2] == b'BD':
if i: from_volume = from_volume[i:]
break
else:
raise ValueError('Magic number not found in image')
drSigWord, drCrDate, drLsMod, drAtrb, drNmFls, \
drVBMSt, drAllocPtr, drNmAlBlks, drAlBlkSiz, drClpSiz, drAlBlSt, \
drNxtCNID, drFreeBks, drVN, drVolBkUp, drVSeqNum, \
drWrCnt, drXTClpSiz, drCTClpSiz, drNmRtDirs, drFilCnt, drDirCnt, \
drFndrInfo, drVCSize, drVBMCSize, drCtlCSize, \
drXTFlSize, drXTExtRec, \
drCTFlSize, drCTExtRec, \
= struct.unpack_from('>2sLLHHHHHLLHLH28pLHLLLHLL32sHHHL12sL12s', from_volume, 1024)
self.crdate, self.mddate, self.bkdate = drCrDate, drLsMod, drVolBkUp
block2offset = lambda block: 512*drAlBlSt + drAlBlkSiz*block
getextents = lambda extents: b''.join(from_volume[block2offset(firstblk):block2offset(firstblk+blkcnt)] for (firstblk, blkcnt) in extents)
getfork = lambda size, extrec1, cnid, fork: getextents(_get_every_extent((size+drAlBlkSiz-1)//drAlBlkSiz, extrec1, cnid, extoflow, fork))[:size]
extoflow = {}
for rec in btree.dump_btree(getfork(drXTFlSize, drXTExtRec, 3, 'data')):
if rec[0] != 7: continue
xkrFkType, xkrFNum, xkrFABN, extrec = struct.unpack_from('>xBLH12s', rec)
if xkrFkType == 0xFF:
fork = 'rsrc'
elif xkrFkType == 0:
fork = 'data'
extoflow[xkrFNum, fork, xkrFABN] = extrec
cnids = {}
childlist = [] # list of (parent_cnid, child_name, child_object) tuples
prev_key = None
for rec in btree.dump_btree(getfork(drCTFlSize, drCTExtRec, 4, 'data')):
# create a directory tree from the catalog file
rec_len = rec[0]
if rec_len == 0: continue
key = rec[2:1+rec_len]
val = rec[bitmanip.pad_up(1+rec_len, 2):]
# if prev_key: # Uncomment this to test the sort order with 20% performance cost!
# if _catalog_rec_sort((prev_key,)) >= _catalog_rec_sort((key,)):
# raise ValueError('Sort error: %r, %r' % (prev_key, key))
# prev_key = key
ckrParID, namelen = struct.unpack_from('>LB', key)
ckrCName = key[5:5+namelen]
datatype = (None, 'dir', 'file', 'dthread', 'fthread')[val[0]]
datarec = val[2:]
# print(datatype + '\t' + repr(key))
# print('\t', datarec)
# print()
if datatype == 'dir':
dirFlags, dirVal, dirDirID, dirCrDat, dirMdDat, dirBkDat, dirUsrInfo, dirFndrInfo \
= struct.unpack_from('>HHLLLL16s16s', datarec)
f = Folder()
cnids[dirDirID] = f
childlist.append((ckrParID, ckrCName, f))
f.crdate, f.mddate, f.bkdate = dirCrDat, dirMdDat, dirBkDat
elif datatype == 'file':
filFlags, filTyp, filUsrWds, filFlNum, \
filStBlk, filLgLen, filPyLen, \
filRStBlk, filRLgLen, filRPyLen, \
filCrDat, filMdDat, filBkDat, \
filFndrInfo, filClpSize, \
filExtRec, filRExtRec, \
= struct.unpack_from('>BB16sLHLLHLLLLL16sH12s12sxxxx', datarec)
f = File()
cnids[filFlNum] = f
childlist.append((ckrParID, ckrCName, f))
f.crdate, f.mddate, f.bkdate = filCrDat, filMdDat, filBkDat
f.type, f.creator, f.flags, f.x, f.y = struct.unpack_from('>4s4sHHH', filUsrWds)
f.data = getfork(filLgLen, filExtRec, filFlNum, 'data')
f.rsrc = getfork(filRLgLen, filRExtRec, filFlNum, 'rsrc')
# elif datatype == 3:
# print('dir thread:', rec)
# elif datatype == 4:
# print('fil thread:', rec)
for parent_cnid, child_name, child_obj in childlist:
if parent_cnid != 1:
parent_obj = cnids[parent_cnid]
parent_obj[child_name] = child_obj
self.update(cnids[2])
self.pop('Desktop', None)
self.pop('Desktop DB', None)
self.pop('Desktop DF', None)
_link_aliases(drCrDate, cnids)
def write(self, size=800*1024, align=512, desktopdb=True, bootable=True, startapp=None, sparse=False):
if align < 512 or align % 512:
raise ValueError('align must be multiple of 512')
if size < 400 * 1024 or size % 512:
raise ValueError('size must be a multiple of 512b and >= 400K')
# These are declared up here because they are needed for aliases
drVN = _encode_name(self.name, 'vol')
drSigWord = b'BD'
drAtrb = 1<<8 # volume attributes (hwlock, swlock, CLEANUNMOUNT, badblocks)
drCrDate, drLsMod, drVolBkUp = self.crdate, self.mddate, self.bkdate
# overall layout:
# 1. two boot blocks (offset=0)
# 2. one volume control block (offset=2)
# 3. some bitmap blocks (offset=3)
# 4. many allocation blocks
# 5. duplicate VCB (offset=-2)
# 6. unused block (offset=-1)
# so we will our best guess at these variables as we go:
# drNmAlBlks, drAlBlkSiz, drAlBlSt
# the smallest possible alloc block size
drAlBlkSiz = _suggest_allocblk_size(size, align)
# how many blocks will we use for the bitmap?
# (cheat by adding blocks to align the alloc area)
bitmap_blk_cnt = 0
while (size - (5+bitmap_blk_cnt)*512) // drAlBlkSiz > bitmap_blk_cnt*512*8:
bitmap_blk_cnt += 1
while (3+bitmap_blk_cnt)*512 % align:
bitmap_blk_cnt += 1
# decide how many alloc blocks there will be
drNmAlBlks = (size - (5+bitmap_blk_cnt)*512) // drAlBlkSiz
blkaccum = []
def accumulate(x):
blkaccum.extend(x)
if len(blkaccum) > drNmAlBlks:
raise OutOfSpaceError
# <<< put the empty extents overflow file in here >>>
extoflowfile = btree.make_btree([], bthKeyLen=7, blksize=drAlBlkSiz)
# also need to do some cleverness to ensure that this gets picked up...
drXTFlSize = len(extoflowfile)
drXTExtRec_Start = len(blkaccum)
accumulate(bitmanip.chunkify(extoflowfile, drAlBlkSiz))
drXTExtRec_Cnt = len(blkaccum) - drXTExtRec_Start
# write all the files in the volume
topwrap = _TempWrapper(self)
topwrap.path = (self.name,)
topwrap.cnid = 2
godwrap = _TempWrapper(None)
godwrap.cnid = 1
root_dict_backup = self._prefdict
if desktopdb:
self._prefdict = dict(self._prefdict)
f = File()
f.type, f.creator = b'FNDR', b'ERIK'
f.flags = 0x4000 # invisible
f.rsrc = make_file([Resource(b'STR ', 0, data=b'\x0AFinder 1.0')])
self['Desktop'] = f
if size >= 2*1024*1024:
f = File()
f.type, f.creator = b'BTFL', b'DMGR'
f.flags = 0x4000
f.data = btree.make_btree([], bthKeyLen=37, blksize=drAlBlkSiz)
self['Desktop DB'] = f
f = File()
f.type, f.creator = b'DTFL', b'DMGR'
f.flags = 0x4000
self['Desktop DF'] = f
system_folder_cnid = 0
startapp_folder_cnid = 0
bootblocks = bytearray(1024)
path2wrap = {(): godwrap, (self.name,): topwrap}
drNxtCNID = 16
for path, obj, aliastarget in _defer_special_files(self.iter_paths()):
path = (self.name,) + path
wrap = _TempWrapper(obj)
path2wrap[path] = wrap
wrap.path = path
wrap.cnid = drNxtCNID; drNxtCNID += 1
if isinstance(obj, File) and obj.type.upper() == b'ZSYS':
try:
sysname = path[-1]
fellows = path2wrap[path[:-1]].of.items()
fndrname = next(n for (n, o) in fellows if isinstance(o, File) and o.type == b'FNDR')
sysresources = parse_file(obj.rsrc)
boot1 = next(r for r in sysresources if (r.type, r.id) == (b'boot', 1))
bb = bytearray(boot1.data)
if len(bb) != 1024: raise ValueError
bb[0x0A:0x1A] = _bb_name(sysname)
bb[0x1A:0x2A] = _bb_name(fndrname)
except:
pass
else:
bootblocks[:] = bb
system_folder_cnid = path2wrap[path[:-1]].cnid
if isinstance(obj, File) and startapp and path[1:] == tuple(startapp):
startapp_folder_cnid = path2wrap[path[:-1]].cnid
if isinstance(obj, File):
wrap.data, wrap.rsrc = obj.data, obj.rsrc
wrap.type, wrap.creator = obj.type, obj.creator
# This is the place to manage your special files (aliases for now)
if aliastarget is not None:
aliastarget = (self.name,) + aliastarget # match the convention for this function
targetobj = path2wrap[aliastarget].of # probe the target to set some metadata
if isinstance(targetobj, Folder):
wrap.creator = b'MACS'
wrap.type = b'fdrp'
elif isinstance(targetobj, Volume):
wrap.creator = b'MACS'
wrap.type = b'hdsk' if size > 1440*1024 else b'flpy'
elif isinstance(targetobj, File):
wrap.creator = targetobj.creator
if targetobj.type == b'APPL':
wrap.type = b'adrp'
else:
wrap.type = targetobj.type
wrap.data = b''
userType = b''
aliasSize = 9999 # fill this short at offset 4
aliasVersion = 2
thisAliasKind = 1 if isinstance(targetobj, Folder) else 0
volumeName = drVN
volumeCrDate = drCrDate
volumeSig = drSigWord
volumeType = 5 #2 if size == 400*1024 else 3 if size == 800*1024 else 4 if size == 1440*1024 else 1
parDirID = path2wrap[aliastarget[:-1]].cnid
fileName = _encode_name(aliastarget[-1])
fileNum = path2wrap[aliastarget].cnid
fileCrDate = path2wrap[aliastarget].of.crdate
fileType = targetobj.type if isinstance(targetobj, File) else b''
fdCreator = targetobj.creator if isinstance(targetobj, File) else b''
nlvlFrom = len(path) - _common_prefix(path, aliastarget)
nlvlTo = len(aliastarget) - _common_prefix(path, aliastarget)
volumeAttributes = 0 # this is aliasmgr-specific
volumeFSID = 0
# Stress test: find file by name, not CNID
# fileNum = 0
alis = Resource(b'alis', 0, name=path[-1])
alis.data[:] = struct.pack('>4s H hh 28p L 2s hL 64p LL 4s4s HHLh',
userType, aliasSize, aliasVersion, \
thisAliasKind, volumeName, volumeCrDate, \
volumeSig, volumeType, parDirID, fileName, \
fileNum, fileCrDate, fileType, fdCreator, \
nlvlFrom, nlvlTo, volumeAttributes, volumeFSID \
) + bytes(10) # reserved stuff
_alis_append(alis.data, 0, aliastarget[-2].encode('mac_roman'))
_alis_append(alis.data, 2, ':'.join(aliastarget).encode('mac_roman'))
_alis_append(alis.data, -1, b'')
struct.pack_into('>H', alis.data, 4, len(alis.data))
# open('/tmp/creating','wb').write(alis.data)
wrap.rsrc = make_file([alis])
if isinstance(obj, File):
wrap.dfrk = wrap.rfrk = (0, 0)
if wrap.data:
pre = len(blkaccum)
accumulate(bitmanip.chunkify(wrap.data, drAlBlkSiz))
wrap.dfrk = (pre, len(blkaccum)-pre)
if wrap.rsrc:
pre = len(blkaccum)
accumulate(bitmanip.chunkify(wrap.rsrc, drAlBlkSiz))
wrap.rfrk = (pre, len(blkaccum)-pre)
self._prefdict = root_dict_backup
catalog = [] # (key, value) tuples
drFilCnt = 0
drDirCnt = -1 # to exclude the root directory
for path, wrap in path2wrap.items():
if wrap.cnid == 1: continue
obj = wrap.of
pstrname = bitmanip.pstring(_encode_name(path[-1], 'file'))
mainrec_key = struct.pack('>L', path2wrap[path[:-1]].cnid) + pstrname
if isinstance(wrap.of, File):
drFilCnt += 1
cdrType = 2
filFlags = 1 << 1 # file thread record exists, but is not locked, nor "file record is used"
filTyp = 0
filUsrWds = struct.pack('>4s4sHHHxxxxxx', wrap.type, wrap.creator, obj.flags, obj.x, obj.y)
filFlNum = wrap.cnid
filStBlk, filLgLen, filPyLen = wrap.dfrk[0], len(wrap.data), bitmanip.pad_up(len(wrap.data), drAlBlkSiz)
filRStBlk, filRLgLen, filRPyLen = wrap.rfrk[0], len(wrap.rsrc), bitmanip.pad_up(len(wrap.rsrc), drAlBlkSiz)
filCrDat, filMdDat, filBkDat = obj.crdate, obj.mddate, obj.bkdate
filFndrInfo = bytes(16) # todo must fix
filClpSize = 0 # todo must fix
filExtRec = struct.pack('>HHHHHH', *wrap.dfrk, 0, 0, 0, 0)
filRExtRec = struct.pack('>HHHHHH', *wrap.rfrk, 0, 0, 0, 0)
mainrec_val = struct.pack('>BxBB16sLHLLHLLLLL16sH12s12sxxxx',
cdrType, \
filFlags, filTyp, filUsrWds, filFlNum, \
filStBlk, filLgLen, filPyLen, \
filRStBlk, filRLgLen, filRPyLen, \
filCrDat, filMdDat, filBkDat, \
filFndrInfo, filClpSize, \
filExtRec, filRExtRec, \
)
else: # assume directory
drDirCnt += 1
cdrType = 1
dirFlags = 0 # must fix
dirVal = len(wrap.of)
dirDirID = wrap.cnid
dirCrDat, dirMdDat, dirBkDat = obj.crdate, obj.mddate, obj.bkdate
dirUsrInfo = bytes(16)
dirFndrInfo = bytes(16)
mainrec_val = struct.pack('>BxHHLLLL16s16sxxxxxxxxxxxxxxxx',
cdrType, dirFlags, dirVal, dirDirID,
dirCrDat, dirMdDat, dirBkDat,
dirUsrInfo, dirFndrInfo,
)
catalog.append((mainrec_key, mainrec_val))
thdrec_key = struct.pack('>Lx', wrap.cnid)
thdrec_val_type = 4 if isinstance(wrap.of, File) else 3
thdrec_val = struct.pack('>BxxxxxxxxxL', thdrec_val_type, path2wrap[path[:-1]].cnid) + pstrname
catalog.append((thdrec_key, thdrec_val))
# now it is time to sort these records! fuck that shit...
catalog.sort(key=_catalog_rec_sort)
catalogfile = btree.make_btree(catalog, bthKeyLen=37, blksize=drAlBlkSiz)
# also need to do some cleverness to ensure that this gets picked up...
drCTFlSize = len(catalogfile)
drCTExtRec_Start = len(blkaccum)
accumulate(bitmanip.chunkify(catalogfile, drAlBlkSiz))
drCTExtRec_Cnt = len(blkaccum) - drCTExtRec_Start
if len(blkaccum) > drNmAlBlks:
raise ValueError('Does not fit!')
# Create the bitmap of free volume allocation blocks
bitmap = bitmanip.bits(bitmap_blk_cnt * 512 * 8, len(blkaccum))
# Set the startup app
if system_folder_cnid and startapp_folder_cnid:
try:
bootblocks[0x5A:0x6A] = _bb_name(startapp[-1])
except:
startapp_folder_cnid = 0
# Create the Volume Information Block
drNmFls = sum(isinstance(x, File) for x in self.values())
drNmRtDirs = sum(not isinstance(x, File) for x in self.values())
drVBMSt = 3 # first block of volume bitmap
drAllocPtr = 0
drClpSiz = drXTClpSiz = drCTClpSiz = drAlBlkSiz
drAlBlSt = 3 + bitmap_blk_cnt
drFreeBks = drNmAlBlks - len(blkaccum)
drWrCnt = 0 # ????volume write count
drVCSize = drVBMCSize = drCtlCSize = 0
drVolBkUp = 0 # date and time of last backup
drVSeqNum = 0 # volume backup sequence number
drFndrInfo = struct.pack('>LLL28x', system_folder_cnid, startapp_folder_cnid, startapp_folder_cnid)
vib = struct.pack('>2sLLHHHHHLLHLH28pLHLLLHLL32sHHHLHHxxxxxxxxLHHxxxxxxxx',
drSigWord, drCrDate, drLsMod, drAtrb, drNmFls,
drVBMSt, drAllocPtr, drNmAlBlks, drAlBlkSiz, drClpSiz, drAlBlSt,
drNxtCNID, drFreeBks, drVN, drVolBkUp, drVSeqNum,
drWrCnt, drXTClpSiz, drCTClpSiz, drNmRtDirs, drFilCnt, drDirCnt,
drFndrInfo, drVCSize, drVBMCSize, drCtlCSize,
drXTFlSize, drXTExtRec_Start, drXTExtRec_Cnt,
drCTFlSize, drCTExtRec_Start, drCTExtRec_Cnt,
)
vib += bytes(512-len(vib))
assert all(len(x) == drAlBlkSiz for x in blkaccum)
left_elements = [bootblocks, vib, bitmap, *blkaccum]
unused_offset = sum(len(x) for x in left_elements)
unused_length = size - unused_offset - 2*512
right_elements = [vib, bytes(512)]
if sparse:
return b''.join(left_elements), unused_length, b''.join(right_elements)
else:
all_elements = left_elements
all_elements.append(bytes(unused_length))
all_elements.extend(right_elements)
return b''.join(all_elements)