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metafix.py
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# -*- coding: utf-8 -*-
#
# Based on initial version of DualMetaFix. Copyright (C) 2013 Kevin Hendricks
# Changes for KCC Copyright (C) 2014-2015 Pawel Jastrzebski <[email protected]>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import struct
import mmap
import shutil
import sys
class DualMetaFixException(Exception):
pass
# palm database offset constants
number_of_pdb_records = 76
first_pdb_record = 78
# important rec0 offsets
mobi_header_base = 16
mobi_header_length = 20
mobi_version = 36
title_offset = 84
def getint(data, ofs, sz='L'):
i, = struct.unpack_from('>'+sz, data, ofs)
return i
def writeint(data, ofs, n, slen='L'):
if slen == 'L':
return data[:ofs]+struct.pack('>L', n)+data[ofs+4:]
else:
return data[:ofs]+struct.pack('>H', n)+data[ofs+2:]
def getsecaddr(datain, secno):
nsec = getint(datain, number_of_pdb_records, 'H')
if (secno < 0) | (secno >= nsec):
emsg = 'requested section number %d out of range (nsec=%d)' % (secno, nsec)
raise DualMetaFixException(emsg)
secstart = getint(datain, first_pdb_record+secno*8)
if secno == nsec-1:
secend = len(datain)
else:
secend = getint(datain, first_pdb_record+(secno+1)*8)
return secstart, secend
def readsection(datain, secno):
secstart, secend = getsecaddr(datain, secno)
return datain[secstart:secend]
# overwrite section - must be exact same length as original
def replacesection(datain, secno, secdata):
secstart, secend = getsecaddr(datain, secno)
seclen = secend - secstart
if len(secdata) != seclen:
raise DualMetaFixException('section length change in replacesection')
datain[secstart:secstart+seclen] = secdata
def get_exth_params(rec0):
ebase = mobi_header_base + getint(rec0, mobi_header_length)
if rec0[ebase:ebase+4] != b'EXTH':
raise DualMetaFixException('EXTH tag not found where expected')
elen = getint(rec0, ebase+4)
enum = getint(rec0, ebase+8)
rlen = len(rec0)
return ebase, elen, enum, rlen
def add_exth(rec0, exth_num, exth_bytes):
ebase, elen, enum, rlen = get_exth_params(rec0)
newrecsize = 8+len(exth_bytes)
newrec0 = rec0[0:ebase+4]+struct.pack('>L', elen+newrecsize)+struct.pack('>L', enum+1)+struct.pack('>L', exth_num)\
+ struct.pack('>L', newrecsize)+exth_bytes+rec0[ebase+12:]
newrec0 = writeint(newrec0, title_offset, getint(newrec0, title_offset)+newrecsize)
# keep constant record length by removing newrecsize null bytes from end
sectail = newrec0[-newrecsize:]
if sectail != b'\0'*newrecsize:
raise DualMetaFixException('add_exth: trimmed non-null bytes at end of section')
newrec0 = newrec0[0:rlen]
return newrec0
def read_exth(rec0, exth_num):
exth_values = []
ebase, elen, enum, rlen = get_exth_params(rec0)
ebase += 12
while enum > 0:
exth_id = getint(rec0, ebase)
if exth_id == exth_num:
# We might have multiple exths, so build a list.
exth_values.append(rec0[ebase+8:ebase+getint(rec0, ebase+4)])
enum -= 1
ebase = ebase+getint(rec0, ebase+4)
return exth_values
def del_exth(rec0, exth_num):
ebase, elen, enum, rlen = get_exth_params(rec0)
ebase_idx = ebase+12
enum_idx = 0
while enum_idx < enum:
exth_id = getint(rec0, ebase_idx)
exth_size = getint(rec0, ebase_idx+4)
if exth_id == exth_num:
newrec0 = rec0
newrec0 = writeint(newrec0, title_offset, getint(newrec0, title_offset)-exth_size)
newrec0 = newrec0[:ebase_idx]+newrec0[ebase_idx+exth_size:]
newrec0 = newrec0[0:ebase+4]+struct.pack('>L', elen-exth_size)+struct.pack('>L', enum-1)+newrec0[ebase+12:]
newrec0 += b'\0'*exth_size
if rlen != len(newrec0):
raise DualMetaFixException('del_exth: incorrect section size change')
return newrec0
enum_idx += 1
ebase_idx = ebase_idx+exth_size
return rec0
class DualMobiMetaFix:
def __init__(self, infile, outfile, asin):
shutil.copyfile(infile, outfile)
f = open(outfile, "r+b")
self.datain = mmap.mmap(f.fileno(), 0)
self.datain_rec0 = readsection(self.datain, 0)
# in the first mobi header
# add 501 to "EBOK", add 113 as asin, add 504 as asin
rec0 = self.datain_rec0
rec0 = del_exth(rec0, 501)
rec0 = del_exth(rec0, 113)
rec0 = del_exth(rec0, 504)
rec0 = add_exth(rec0, 501, b'EBOK')
rec0 = add_exth(rec0, 113, asin)
rec0 = add_exth(rec0, 504, asin)
replacesection(self.datain, 0, rec0)
ver = getint(self.datain_rec0, mobi_version)
self.combo = (ver != 8)
if not self.combo:
return
exth121 = read_exth(self.datain_rec0, 121)
if len(exth121) == 0:
self.combo = False
return
else:
# only pay attention to first exth121
# (there should only be one)
datain_kf8, = struct.unpack_from('>L', exth121[0], 0)
if datain_kf8 == 0xffffffff:
self.combo = False
return
self.datain_kfrec0 = readsection(self.datain, datain_kf8)
# in the second header
# add 501 to "EBOK", add 113 as asin, add 504 as asin
rec0 = self.datain_kfrec0
rec0 = del_exth(rec0, 501)
rec0 = del_exth(rec0, 113)
rec0 = del_exth(rec0, 504)
rec0 = add_exth(rec0, 501, b'EBOK')
rec0 = add_exth(rec0, 113, asin)
rec0 = add_exth(rec0, 504, asin)
replacesection(self.datain, datain_kf8, rec0)
self.datain.flush()
self.datain.close()
name = sys.argv[1]
asin = sys.argv[2]
DualMobiMetaFix(name, name[:-5]+"_fixed"+name[-5:], asin)