508 lines
14 KiB
Python
Executable File
508 lines
14 KiB
Python
Executable File
#!/usr/bin/env python
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# pdfparser.py, Yusuke Shinyama
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# ver 0.1, Dec 24 2004-
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# ver 0.2, Dec 24 2007
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# TODO:
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# - Code Documentation.
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# - Error handling for invalid type.
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# - Outlines.
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# - Named Objects. (pages)
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# - Writers.
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# - Linearized PDF.
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# - Encryption?
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import sys, re
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try:
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from cStringIO import StringIO
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except ImportError:
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from StringIO import StringIO
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stderr = sys.stderr
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from utils import choplist, nunpack
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from psparser import PSException, PSSyntaxError, PSTypeError, \
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PSLiteral, PSKeyword, PSLiteralTable, PSKeywordTable, \
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literal_name, keyword_name, \
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PSStackParser
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## PDF Exceptions
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##
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class PDFException(PSException): pass
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class PDFSyntaxError(PDFException): pass
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class PDFEncrypted(PDFException): pass
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class PDFTypeError(PDFException): pass
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class PDFValueError(PDFException): pass
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# some predefined literals and keywords.
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LITERAL_OBJSTM = PSLiteralTable.intern('ObjStm')
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LITERAL_XREF = PSLiteralTable.intern('XRef')
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LITERAL_PAGE = PSLiteralTable.intern('Page')
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LITERAL_PAGES = PSLiteralTable.intern('Pages')
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LITERAL_CATALOG = PSLiteralTable.intern('Catalog')
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LITERAL_FLATE_DECODE = PSLiteralTable.intern('FlateDecode')
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KEYWORD_OBJ = PSKeywordTable.intern('obj')
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## PDFObjRef
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##
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class PDFObjRef:
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def __init__(self, doc, objid, genno):
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if objid == 0:
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raise PDFValueError('objid cannot be 0.')
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self.doc = doc
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self.objid = objid
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#self.genno = genno # Never used.
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return
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def __repr__(self):
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return '<PDFObjRef:%d>' % (self.objid)
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def resolve(self):
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return self.doc.getobj(self.objid)
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# resolve
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def resolve1(x):
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'''
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Resolve an object. If this is an array or dictionary,
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it may still contains some indirect objects inside.
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'''
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while isinstance(x, PDFObjRef):
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x = x.resolve()
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return x
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def resolveall(x):
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'''
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Recursively resolve X and all the internals.
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Make sure there is no indirect reference within the nested object.
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This procedure might be slow.
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'''
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while isinstance(x, PDFObjRef):
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x = x.resolve()
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if isinstance(x, list):
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x = [ resolveall(v) for v in x ]
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elif isinstance(x, dict):
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for (k,v) in x.iteritems():
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x[k] = resolveall(v)
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return x
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# Type cheking
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def int_value(x):
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x = resolve1(x)
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if not isinstance(x, int):
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raise PDFTypeError('integer required: %r' % x)
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return x
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def float_value(x):
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x = resolve1(x)
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if not isinstance(x, float):
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raise PDFTypeError('float required: %r' % x)
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return x
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def num_value(x):
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x = resolve1(x)
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if not (isinstance(x, int) or isinstance(x, float)):
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raise PDFTypeError('int or float required: %r' % x)
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return x
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def str_value(x):
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x = resolve1(x)
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if not isinstance(x, str):
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raise PDFTypeError('string required: %r' % x)
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return x
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def list_value(x):
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x = resolve1(x)
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if not isinstance(x, list):
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raise PDFTypeError('list required: %r' % x)
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return x
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def dict_value(x):
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x = resolve1(x)
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if not isinstance(x, dict):
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raise PDFTypeError('dict required: %r' % x)
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return x
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def stream_value(x):
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x = resolve1(x)
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if not isinstance(x, PDFStream):
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raise PDFTypeError('stream required: %r' % x)
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return x
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## PDFStream type
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##
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class PDFStream:
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def __init__(self, dic, rawdata, crypt=None):
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self.dic = dic
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self.rawdata = rawdata
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self.crypt = crypt
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self.data = None
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return
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def __repr__(self):
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return '<PDFStream: %r>' % (self.dic)
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def decode(self):
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assert self.data == None and self.rawdata != None
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data = self.rawdata
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if self.crypt:
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# func DECRYPT is not implemented yet...
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raise NotImplementedError
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data = DECRYPT(self.crypt, data)
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if 'Filter' not in self.dic:
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self.data = data
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self.rawdata = None
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return
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filters = self.dic['Filter']
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if not isinstance(filters, list):
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filters = [ filters ]
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for f in filters:
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if f == LITERAL_FLATE_DECODE:
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import zlib
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# will get errors if the document is encrypted.
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data = zlib.decompress(data)
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# apply predictors
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params = self.dic.get('DecodeParms', {})
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if 'Predictor' in params:
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pred = int_value(params['Predictor'])
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if pred:
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if pred != 12:
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raise PDFValueError('Unsupported predictor: %r' % pred)
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if 'Columns' not in params:
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raise PDFValueError('Columns undefined for predictor=12')
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columns = int_value(params['Columns'])
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buf = ''
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ent0 = '\x00' * columns
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for i in xrange(0, len(data), columns+1):
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pred = data[i]
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ent1 = data[i+1:i+1+columns]
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if pred == '\x02':
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ent1 = ''.join( chr((ord(a)+ord(b)) & 255) for (a,b) in zip(ent0,ent1) )
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buf += ent1
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ent0 = ent1
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data = buf
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else:
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raise PDFValueError('Invalid filter spec: %r' % f)
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self.data = data
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self.rawdata = None
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return
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def get_data(self):
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if self.data == None:
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self.decode()
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return self.data
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## PDFPage
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##
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class PDFPage:
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def __init__(self, doc, pageidx, attrs):
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self.doc = doc
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self.pageid = pageidx
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self.attrs = dict_value(attrs)
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self.resources = resolve1(self.attrs['Resources'])
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self.mediabox = resolve1(self.attrs['MediaBox'])
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contents = resolve1(self.attrs['Contents'])
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if not isinstance(contents, list):
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contents = [ contents ]
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self.contents = contents
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return
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def __repr__(self):
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return '<PDFPage: Resources=%r, MediaBox=%r>' % (self.resources, self.mediabox)
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## XRefs
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## PDFXRef
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##
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class PDFXRef:
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def __init__(self, parser):
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while 1:
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(_, line) = parser.nextline()
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if not line:
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raise PDFSyntaxError('premature eof: %r' % parser)
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line = line.strip()
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f = line.split(' ')
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if len(f) != 2:
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if line != 'trailer':
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raise PDFSyntaxError('trailer not found: %r: line=%r' % (parser, line))
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break
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(start, nobjs) = map(long, f)
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self.objid0 = start
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self.objid1 = start+nobjs
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self.offsets = []
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for objid in xrange(start, start+nobjs):
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(_, line) = parser.nextline()
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f = line.strip().split(' ')
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if len(f) != 3:
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raise PDFSyntaxError('invalid xref format: %r, line=%r' % (parser, line))
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(pos, genno, use) = f
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self.offsets.append((int(genno), long(pos), use))
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# read trailer
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self.trailer = dict_value(parser.parse()[0])
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return
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def getpos(self, objid):
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if objid < self.objid0 or self.objid1 <= objid:
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raise IndexError
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(genno, pos, use) = self.offsets[objid-self.objid0]
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if use != 'n':
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raise PDFValueError('unused objid=%r' % objid)
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return (None, pos)
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## PDFXRefStream
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##
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class PDFXRefStream:
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def __init__(self, parser):
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(objid, genno, _, stream) = list_value(parser.parse())
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assert stream.dic['Type'] == LITERAL_XREF
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size = stream.dic['Size']
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(start, nobjs) = stream.dic.get('Index', (0,size))
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self.objid0 = start
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self.objid1 = start+nobjs
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(self.fl1, self.fl2, self.fl3) = stream.dic['W']
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self.data = stream.get_data()
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self.entlen = self.fl1+self.fl2+self.fl3
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self.trailer = stream.dic
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return
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def getpos(self, objid):
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if objid < self.objid0 or self.objid1 <= objid:
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raise IndexError
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i = self.entlen * (objid-self.objid0)
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ent = self.data[i:i+self.entlen]
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f1 = nunpack(ent[:self.fl1], 1)
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if f1 == 1:
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pos = nunpack(ent[self.fl1:self.fl1+self.fl2])
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genno = nunpack(ent[self.fl1+self.fl2:])
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return (None, pos)
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elif f1 == 2:
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objid = nunpack(ent[self.fl1:self.fl1+self.fl2])
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index = nunpack(ent[self.fl1+self.fl2:])
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return (objid, index)
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## PDFDocument
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##
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class PDFDocument:
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def __init__(self, debug=0):
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self.debug = debug
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self.xrefs = []
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self.objs = {}
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self.parsed_objs = {}
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self.crypt = None
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self.root = None
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self.catalog = None
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self.parser = None
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return
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def set_parser(self, parser):
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if self.parser: return
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self.parser = parser
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self.xrefs = list(parser.read_xref())
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for xref in self.xrefs:
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trailer = xref.trailer
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if 'Encrypt' in trailer:
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self.crypt = dict_value(trailer['Encrypt'])
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if 'Root' in trailer:
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self.set_root(dict_value(trailer['Root']))
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break
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else:
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raise PDFValueError('no /Root object!')
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return
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def getobj(self, objid):
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assert self.xrefs
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if objid in self.objs:
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obj = self.objs[objid]
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else:
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for xref in self.xrefs:
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try:
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(strmid, index) = xref.getpos(objid)
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break
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except IndexError:
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pass
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else:
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raise PDFValueError('Cannot locate objid=%r' % objid)
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if strmid:
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stream = stream_value(self.getobj(strmid))
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if stream.dic['Type'] != LITERAL_OBJSTM:
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raise PDFSyntaxError('Not a stream object: %r' % stream)
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if 'N' not in stream.dic:
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raise PDFSyntaxError('N is not defined: %r' % stream)
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if strmid in self.parsed_objs:
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objs = self.parsed_objs[stream]
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else:
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parser = PDFParser(self, StringIO(stream.get_data()),
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debug=self.debug)
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objs = list(parser.parse())
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self.parsed_objs[stream] = objs
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obj = objs[stream.dic['N']*2+index]
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else:
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prevpos = self.parser.seek(index)
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seq = list_value(self.parser.parse())
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if not (len(seq) == 4 and seq[0] == objid and seq[2] == KEYWORD_OBJ):
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raise PDFSyntaxError('invalid stream spec: %r' % seq)
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obj = seq[3]
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self.parser.seek(prevpos)
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if 2 <= self.debug:
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print >>stderr, 'register: objid=%r: %r' % (objid, obj)
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self.objs[objid] = obj
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return obj
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def get_pages(self, debug=0):
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assert self.xrefs
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def search(obj, parent):
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tree = dict_value(obj).copy()
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for (k,v) in parent.iteritems():
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if k not in tree:
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tree[k] = v
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if tree['Type'] == LITERAL_PAGES:
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if 1 <= debug:
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print >>stderr, 'Pages: Kids=%r' % tree['Kids']
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for c in tree['Kids']:
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for x in search(c, tree):
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yield x
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elif tree['Type'] == LITERAL_PAGE:
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if 1 <= debug:
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print >>stderr, 'Page: %r' % tree
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yield tree
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for (i,tree) in enumerate(search(self.catalog['Pages'], self.catalog)):
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yield PDFPage(self, i, tree)
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return
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def set_root(self, root):
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self.root = root
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self.catalog = dict_value(self.root)
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if self.catalog['Type'] != LITERAL_CATALOG:
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raise PDFValueError('Catalog not found!')
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self.outline = self.catalog.get('Outline')
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return
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## PDFParser
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##
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class PDFParser(PSStackParser):
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def __init__(self, doc, fp, debug=0):
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PSStackParser.__init__(self, fp, debug=debug)
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self.doc = doc
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self.doc.set_parser(self)
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return
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def __repr__(self):
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return '<PDFParser: linepos=%d>' % self.linepos
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EOIPAT = re.compile(r'\nEI\W')
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def do_token(self, pos, token):
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name = keyword_name(token)
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if name in ('xref', 'trailer', 'startxref', 'endobj'):
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return True
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if name == 'R':
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# reference to indirect object
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try:
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(objid, genno) = self.pop(2)
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(objid, genno) = (int(objid), int(genno))
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obj = PDFObjRef(self.doc, objid, genno)
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self.push(obj)
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if 2 <= self.debug:
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print >>stderr, 'refer obj: %r' % obj
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except PSSyntaxError:
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pass
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elif name == 'stream':
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# stream object
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(dic,) = self.pop(1)
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dic = dict_value(dic)
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if 'Length' not in dic:
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raise PDFValueError('/Length is undefined: %r' % dic)
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objlen = int_value(dic['Length'])
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self.seek(pos)
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(_, line) = self.nextline() # 'stream'
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self.fp.seek(pos+len(line))
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data = self.fp.read(objlen)
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self.seek(pos+len(line)+objlen)
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while 1:
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(linepos, line) = self.nextline()
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if not line:
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raise PDFSyntaxError('premature eof, need endstream: linepos=%d, line=%r' %
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(linepos, line))
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if line.strip():
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if not line.startswith('endstream'):
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raise PDFSyntaxError('need endstream: linepos=%d, line=%r' %
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(linepos, line))
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break
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if 1 <= self.debug:
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print >>stderr, 'Stream: pos=%d, objlen=%d, dic=%r, data=%r...' % \
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(pos, objlen, dic, data[:10])
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obj = PDFStream(dic, data)
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self.push(obj)
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else:
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self.push(token)
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return False
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def find_xref(self):
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# find the first xref table
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prev = None
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for line in self.revreadlines():
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line = line.strip()
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if 2 <= self.debug:
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print >>stderr, 'line: %r' % line
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if line == 'startxref': break
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if line:
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prev = line
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else:
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raise PDFSyntaxError('startxref not found!')
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if 1 <= self.debug:
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print >>stderr, 'xref found: pos=%r' % prev
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self.seek(long(prev))
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return
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# read xref tables and trailers
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def read_xref(self):
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self.find_xref()
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while 1:
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# read xref table
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(linepos, line) = self.nextline()
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if 2 <= self.debug:
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print >>stderr, 'line: %r' % line
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if line[0].isdigit():
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# XRefStream: PDF-1.5
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self.seek(linepos)
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xref = PDFXRefStream(self)
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elif line.strip() != 'xref':
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raise PDFSyntaxError('xref not found: linepos=%d, line=%r' %
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(linepos, line))
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else:
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xref = PDFXRef(self)
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yield xref
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trailer = xref.trailer
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if 1 <= self.debug:
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print >>stderr, 'trailer: %r' % trailer
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if 'XRefStm' in trailer:
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self.seek(int_value(trailer['XRefStm']))
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if 'Prev' in trailer:
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# find previous xref
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pos = int_value(trailer['Prev'])
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self.seek(pos)
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if 1 <= self.debug:
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print >>stderr, 'prev trailer: pos=%d' % pos
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else:
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break
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return
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