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MOBI debug: Last remaininng TBS type almost completely deciphered

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This commit is contained in:
Kovid Goyal 2011-07-22 00:07:38 -06:00
parent c8545cb7d7
commit 769c1dc678
2 changed files with 57 additions and 67 deletions
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103
src/calibre/ebooks/mobi/debug.py
View File

@ -941,27 +941,33 @@ class TBSIndexing(object): # {{{
def interpret_periodical(self, tbs_type, byts):
ans = []
def tbs_type_6(byts, psi=None): # {{{
def tbs_type_6(byts, psi=None, msg=None): # {{{
if psi is None:
# Assume parent section is 1
psi = self.get_index(1)
if msg is None:
msg = ('Article index at start of record or first article'
' index, relative to parent section')
if byts:
# byts could be empty
arg, consumed = decint(byts)
byts = byts[consumed:]
flags = (arg & 0b1111)
ai = (arg >> 4)
ans.append(('Article index at start of record or first article'
' index, relative to parent section (fvwi): %d [%d absolute]'%(ai,
ai+psi.index)))
ans.append('%s (fvwi): %d [%d absolute]'%(msg, ai,
ai+psi.index))
if flags == 1:
arg, consumed = decint(byts)
byts = byts[consumed:]
ans.append('EOF (vwi: should be 0): %d'%arg)
elif flags == 4:
elif flags in (4, 5):
num = byts[0]
byts = byts[1:]
ans.append('Number of article nodes in the record (byte): %d'%num)
if flags == 5:
arg, consumed = decint(byts)
byts = byts[consumed:]
ans.append('Unknown ??? (vwi)): %d'%(arg))
elif flags == 0:
pass
else:
@ -971,70 +977,33 @@ class TBSIndexing(object): # {{{
# }}}
if tbs_type == 3: # {{{
arg2, consumed = decint(byts)
byts = byts[consumed:]
ans.append('Unknown (vwi: always 0?): %d'%arg2)
arg3, consumed = decint(byts)
byts = byts[consumed:]
fsi = arg3 >> 4
extra = arg3 & 0b1111
ans.append('First section index (fvwi): %d'%fsi)
psi = self.get_index(fsi)
ans.append('Extra bits (flag: always 0?): %d'%extra)
byts = tbs_type_6(byts, psi=psi,
msg=('First article of ending section, relative to its'
' parent\'s index'))
if byts:
arg2, consumed = decint(byts)
# We have a transition not just an opening first section
psi = self.get_index(psi.index+1)
arg, consumed = decint(byts)
off = arg >> 4
byts = byts[consumed:]
ans.append('Unknown: %d'%arg2)
if byts:
arg3, consumed = decint(byts)
byts = byts[consumed:]
fsi = arg3 >> 4
extra = arg3 & 0b1111
ans.append('First section index: %d'%fsi)
psi = self.get_index(fsi)
ans.append('Extra bits: %d'%extra)
if byts:
if byts[0] == fsi:
ssi = psi.index+1
ans.append('First section ends')
byts = byts[1:]
arg, consumed = decint(byts)
raw = byts[:consumed]
byts = byts[consumed:]
flags = arg & 0b1111
ans.append('Unknown (art index at start of record?):'
' %d %r'%((arg>>4), raw))
ans.append('Flags: %d'%flags)
num = 1
if flags >= 4:
num = byts[0]
byts = byts[1:]
ans.append('Number of articles in closing section: %d'%num)
if flags == 5:
arg, consumed = decint(byts)
ans.append('Unknown: %r'%bytes(byts[:consumed]))
byts = byts[consumed:]
arg, consumed = decint(byts)
byts = byts[consumed:]
off = arg >> 4
ans.append('Last article of ending section w.r.t. starting'
' section offset: %d [%d absolute]'%(off,
ssi+off))
ans.append('Extra bits: %d'%(arg & 0b1111))
arg, consumed = decint(byts)
byts = byts[consumed:]
off = arg >> 4
flag = arg & 0b1111
ans.append('Offset to first article of starting section: %d'
' [%d absolute]'%(off, ssi+off))
ans.append('Flags: %d'%flag)
num = 1
if flag == 4:
num = byts[0]
byts = byts[1:]
ans.append('Number of articles in starting section: %d'%num)
else:
ans.append('First section starts')
off, consumed = decint(byts)
flags = off & 0b1111
off = off >> 4
byts = byts[consumed:]
ans.append('Article at start of block as offset from '
'parent index: %d [%d absolute]'%(off, psi.index+off))
ans.append('Flags: %d'%flags)
if flags == 4:
ans.append('Number of articles: %d'%byts[0])
byts = byts[1:]
flags = arg & 0b1111
ans.append('Last article of ending section w.r.t. starting'
' section offset (fvwi): %d [%d absolute]'%(off,
psi.index+off))
ans.append('Flags (always 8?): %d'%flags)
byts = tbs_type_6(byts, psi=psi)
# }}}
elif tbs_type == 7: # {{{

21
src/calibre/ebooks/mobi/tbs_periodicals.rst
View File

@ -142,6 +142,27 @@ In such a record there is a transition from one section to the next. As such the
TODO: Note you have to test the cases of first section, a single transition and multiple transitions.
1. The first section::
Record #2: Starts at: 4096 Ends at: 8191
Contains: 2 index entries (0 ends, 0 complete, 2 starts)
TBS bytes: 83 80 80 90 c0
Starts:
Index Entry: 1 (Parent index: 0, Depth: 1, Offset: 7758, Size: 26279) [Ars Technica]
Index Entry: 5 (Parent index: 1, Depth: 2, Offset: 7766, Size: 1866) [Week in gaming: 3DS review, Crysis 2, George Hotz]
TBS Type: 011 (3)
Outer Index entry: 0
Unknown (vwi: always 0?): 0
Unknown (vwi: always 0?): 0
First section index (fvwi) : 1
Extra bits: 0
First section starts
Article at start of block as offset from parent index (fvwi): 4 [5 absolute]
Flags: 0
If there was more than one article at the start then the last byte would be replaced by: c4 n where n is the number of articles
Ending record
----------------