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GwR revisions to extend EXTH header
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GRiker
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345e752714
commit
d5c756a84d
@ -17,6 +17,8 @@ from calibre.ebooks.mobi import MobiError
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from calibre.ebooks.mobi.writer import rescale_image, MAX_THUMB_DIMEN
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from calibre.ebooks.mobi.langcodes import iana2mobi
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import struct, traceback
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class StreamSlicer(object):
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def __init__(self, stream, start=0, stop=None):
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@ -72,6 +74,17 @@ class StreamSlicer(object):
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return stream.write(value)
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raise TypeError("stream indices must be integers")
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def update(self, data_blocks):
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# Rewrite the stream
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stream = self._stream
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base = self.start
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stream.seek(base)
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self._stream.truncate(base)
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for block in data_blocks:
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stream.write(block)
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def truncate(self, value):
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self._stream.truncate(value)
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class MetadataUpdater(object):
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def __init__(self, stream):
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@ -84,13 +97,27 @@ class MetadataUpdater(object):
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codepage, = unpack('>I', record0[28:32])
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self.codec = 'utf-8' if codepage == 65001 else 'cp1252'
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image_base, = unpack('>I', record0[108:112])
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flags, = unpack('>I', record0[128:132])
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flags, = self.flags, = unpack('>I', record0[128:132])
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have_exth = self.have_exth = (flags & 0x40) != 0
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self.cover_record = self.thumbnail_record = None
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self.timestamp = None
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self.pdbrecords = self.get_pdbrecords()
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if not have_exth:
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return
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self.create_exth()
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# Fetch timestamp, cover_record, thumbnail_record
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self.fetchEXTHFields()
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def fetchEXTHFields(self):
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stream = self.stream
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record0 = self.record0
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# 20:24 = mobiHeaderLength, 16=PDBHeader size
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exth_off = unpack('>I', record0[20:24])[0] + 16 + record0.start
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image_base, = unpack('>I', record0[108:112])
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# Fetch EXTH block
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exth = self.exth = StreamSlicer(stream, exth_off, record0.stop)
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nitems, = unpack('>I', exth[8:12])
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pos = 12
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@ -108,7 +135,136 @@ class MetadataUpdater(object):
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elif id == 202:
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rindex, = self.thumbnail_rindex, = unpack('>I', content)
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self.thumbnail_record = self.record(rindex + image_base)
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def patch(self, off, new_record0):
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# Save the current size of each record
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record_sizes = [len(new_record0)]
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for i in range(1,self.nrecs-1):
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record_sizes.append(self.pdbrecords[i+1][0]-self.pdbrecords[i][0])
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# And the last one
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record_sizes.append(self.data.stop - self.pdbrecords[self.nrecs-1][0])
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# pdbrecord[0] is the offset of record0. It will not change
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# record1 offset will be offset of record0 + len(new_record0)
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updated_pdbrecords = [self.pdbrecords[0][0]]
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record0_offset = self.pdbrecords[0][0]
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current_offset = self.pdbrecords[1][0]
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updated_offset = record0_offset + len(new_record0)
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for i in range(1,self.nrecs-1):
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updated_pdbrecords.append(updated_offset)
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updated_offset += record_sizes[i]
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# Update the last pdbrecord
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updated_pdbrecords.append(updated_offset)
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# Read in current records 1 to last
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data_blocks = [new_record0]
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for i in range(1,self.nrecs):
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data_blocks.append(self.data[self.pdbrecords[i][0]:self.pdbrecords[i][0] + record_sizes[i]])
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# Rewrite the stream
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self.record0.update(data_blocks)
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# Rewrite the pdbrecords
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self.update_pdbrecords(updated_pdbrecords)
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# Truncate if necessary
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if (updated_pdbrecords[-1] + record_sizes[-1]) < self.data.stop:
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self.data.truncate(updated_pdbrecords[-1] + record_sizes[-1])
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else:
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self.data.stop = updated_pdbrecords[-1] + record_sizes[-1]
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def patchSection(self, section, new):
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if (section + 1 == self.nrecs):
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endoff = len(self.stream)
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else:
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endoff = self.pdbrecords[section + 1][0]
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off = self.pdbrecords[section][0]
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self.patch(off, new)
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def create_exth(self, exth=None):
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# Add an EXTH block to record 0, rewrite the stream
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# self.hexdump(self.record0)
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# Fetch the title
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title_offset, = struct.unpack('>L', self.record0[0x54:0x58])
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title_length, = struct.unpack('>L', self.record0[0x58:0x5c])
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title_in_file, = struct.unpack('%ds' % (title_length), self.record0[title_offset:title_offset + title_length])
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# Adjust length to accommodate PrimaryINDX if necessary
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mobi_header_length, = unpack('>L', self.record0[0x14:0x18])
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if mobi_header_length == 0xe4:
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# Patch mobi_header_length to 0xE8
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self.record0[0x17] = "\xe8"
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self.record0[0xf4:0xf8] = pack('>L', 0xFFFFFFFF)
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mobi_header_length = 0xe8
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# Set EXTH flag (0x40)
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self.record0[0x80:0x84] = pack('>L', self.flags|0x40)
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if not exth:
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# Construct an empty EXTH block
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pad = '\0' * 4
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exth = ['EXTH', pack('>II', 12, 0), pad]
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exth = ''.join(exth)
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# Update title_offset
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self.record0[0x54:0x58] = pack('>L', 0x10 + mobi_header_length + len(exth))
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# Create an updated Record0
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new_record0 = StringIO()
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new_record0.write(self.record0[:0x10 + mobi_header_length])
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new_record0.write(exth)
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new_record0.write(title_in_file)
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# Pad to a 4-byte boundary
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trail = len(new_record0.getvalue()) % 4
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pad = '\0' * (4 - trail) # Always pad w/ at least 1 byte
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new_record0.write(pad)
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self.hexdump(new_record0.getvalue())
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# Rebuild the stream, update the pdbrecords pointers
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self.patchSection(0,new_record0.getvalue())
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# Update record0
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self.record0 = self.record(0)
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def hexdump(self, src, length=16):
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# Diagnostic
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FILTER=''.join([(len(repr(chr(x)))==3) and chr(x) or '.' for x in range(256)])
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N=0; result=''
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while src:
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s,src = src[:length],src[length:]
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hexa = ' '.join(["%02X"%ord(x) for x in s])
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s = s.translate(FILTER)
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result += "%04X %-*s %s\n" % (N, length*3, hexa, s)
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N+=length
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print result
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def get_pdbrecords(self):
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pdbrecords = []
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for i in xrange(self.nrecs):
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offset, a1,a2,a3,a4 = struct.unpack('>LBBBB', self.data[78+i*8:78+i*8+8])
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flags, val = a1, a2<<16|a3<<8|a4
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pdbrecords.append( [offset, flags, val] )
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return pdbrecords
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def update_pdbrecords(self, updated_pdbrecords):
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for (i, pdbrecord) in enumerate(updated_pdbrecords):
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self.data[78+i*8:78+i*8 + 4] = pack('>L',pdbrecord)
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# Refresh local copy
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self.pdbrecords = self.get_pdbrecords()
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def dump_pdbrecords(self):
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# Diagnostic
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print "MetadataUpdater.dump_pdbrecords()"
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print "%10s %10s %10s" % ("offset","flags","val")
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for i in xrange(len(self.pdbrecords)):
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pdbrecord = self.pdbrecords[i]
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print "%10X %10X %10X" % (pdbrecord[0], pdbrecord[1], pdbrecord[2])
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def record(self, n):
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if n >= self.nrecs:
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raise ValueError('non-existent record %r' % n)
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@ -142,7 +298,6 @@ class MetadataUpdater(object):
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if mi.tags:
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subjects = '; '.join(mi.tags)
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recs.append((105, subjects.encode(self.codec, 'replace')))
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if mi.pubdate:
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recs.append((106, str(mi.pubdate).encode(self.codec, 'replace')))
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elif mi.timestamp:
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@ -151,15 +306,16 @@ class MetadataUpdater(object):
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recs.append((106, self.timestamp))
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else:
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recs.append((106, str(datetime.now()).encode(self.codec, 'replace')))
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if self.cover_record is not None:
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recs.append((201, pack('>I', self.cover_rindex)))
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recs.append((203, pack('>I', 0)))
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if self.thumbnail_record is not None:
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recs.append((202, pack('>I', self.thumbnail_rindex)))
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exth = StringIO()
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if getattr(self, 'encryption_type', -1) != 0:
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raise MobiError('Setting metadata in DRMed MOBI files is not supported.')
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exth = StringIO()
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for code, data in recs:
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exth.write(pack('>II', code, len(data) + 8))
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exth.write(data)
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@ -168,17 +324,17 @@ class MetadataUpdater(object):
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pad = '\0' * (4 - trail) # Always pad w/ at least 1 byte
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exth = ['EXTH', pack('>II', len(exth) + 12, len(recs)), exth, pad]
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exth = ''.join(exth)
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title = (mi.title or _('Unknown')).encode(self.codec, 'replace')
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if getattr(self, 'exth', None) is None:
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raise MobiError('No existing EXTH record. Cannot update metadata.')
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title_off = (self.exth.start - self.record0.start) + len(exth)
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title_len = len(title)
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trail = len(self.exth) - len(exth) - len(title)
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if trail < 0:
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raise MobiError("Insufficient space to update metadata")
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self.exth[:] = ''.join([exth, title, '\0' * trail])
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self.record0[84:92] = pack('>II', title_off, title_len)
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self.record0[92:96] = iana2mobi(mi.language)
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self.create_exth(exth)
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# Fetch updated timestamp, cover_record, thumbnail_record
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self.fetchEXTHFields()
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if mi.cover_data[1] or mi.cover:
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try:
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data = mi.cover_data[1] if mi.cover_data[1] else open(mi.cover, 'rb').read()
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