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809 lines
29 KiB
809 lines
29 KiB
import io
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import re
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import struct
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import hashlib as md5
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import logging
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from .psparser import PSStackParser, PSSyntaxError, PSEOF, literal_name, LIT, KWD, handle_error
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from .pdftypes import (PDFException, PDFTypeError, PDFNotImplementedError, PDFStream, PDFObjRef,
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resolve1, decipher_all, int_value, str_value, list_value, dict_value, stream_value)
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from .arcfour import Arcfour
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from .utils import choplist, nunpack, decode_text, ObjIdRange
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logger = logging.getLogger(__name__)
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## Exceptions
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##
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class PDFSyntaxError(PDFException): pass
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class PDFNoValidXRef(PDFSyntaxError): pass
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class PDFNoOutlines(PDFException): pass
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class PDFDestinationNotFound(PDFException): pass
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class PDFAlreadyParsed(PDFException): pass
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class PDFEncryptionError(PDFException): pass
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class PDFPasswordIncorrect(PDFEncryptionError): pass
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# some predefined literals and keywords.
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LITERAL_OBJSTM = LIT('ObjStm')
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LITERAL_XREF = LIT('XRef')
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LITERAL_PAGE = LIT('Page')
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LITERAL_PAGES = LIT('Pages')
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LITERAL_CATALOG = LIT('Catalog')
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class PDFBaseXRef:
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def get_trailer(self):
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raise NotImplementedError
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def get_objids(self):
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return []
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def get_pos(self, objid):
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raise KeyError(objid)
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class PDFXRef(PDFBaseXRef):
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def __init__(self):
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self.offsets = {}
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self.trailer = {}
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def load(self, parser):
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while 1:
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try:
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(pos, line) = parser.nextline()
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if not line.strip(): continue
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except PSEOF:
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raise PDFNoValidXRef('Unexpected EOF - file corrupted?')
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if not line:
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raise PDFNoValidXRef('Premature eof: %r' % parser)
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if line.startswith('trailer'):
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parser.setpos(pos)
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break
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f = line.strip().split(' ')
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if len(f) != 2:
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raise PDFNoValidXRef('Trailer not found: %r: line=%r' % (parser, line))
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try:
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(start, nobjs) = list(map(int, f))
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except ValueError:
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raise PDFNoValidXRef('Invalid line: %r: line=%r' % (parser, line))
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for objid in range(start, start+nobjs):
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try:
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(_, line) = parser.nextline()
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except PSEOF:
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raise PDFNoValidXRef('Unexpected EOF - file corrupted?')
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f = line.strip().split(' ')
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if len(f) != 3:
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raise PDFNoValidXRef('Invalid XRef format: %r, line=%r' % (parser, line))
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(pos, genno, use) = f
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if use != 'n': continue
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self.offsets[objid] = (int(genno), int(pos))
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logger.debug('xref objects: %r', self.offsets)
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self.load_trailer(parser)
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KEYWORD_TRAILER = KWD('trailer')
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def load_trailer(self, parser):
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try:
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(_,kwd) = parser.nexttoken()
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assert kwd is self.KEYWORD_TRAILER
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(_,dic) = parser.nextobject()
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except PSEOF:
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x = parser.pop(1)
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if not x:
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raise PDFNoValidXRef('Unexpected EOF - file corrupted')
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(_,dic) = x[0]
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self.trailer.update(dict_value(dic))
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PDFOBJ_CUE = re.compile(r'^(\d+)\s+(\d+)\s+obj\b')
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def load_fallback(self, parser, debug=0):
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parser.setpos(0)
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while 1:
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try:
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(pos, line) = parser.nextline()
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except PSEOF:
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break
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if line.startswith('trailer'):
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parser.setpos(pos)
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self.load_trailer(parser)
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logger.debug('trailer: %r', self.get_trailer())
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break
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m = self.PDFOBJ_CUE.match(line)
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if not m: continue
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(objid, genno) = m.groups()
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self.offsets[int(objid)] = (0, pos)
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def get_trailer(self):
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return self.trailer
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def get_objids(self):
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return iter(self.offsets.keys())
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def get_pos(self, objid):
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try:
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(genno, pos) = self.offsets[objid]
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except KeyError:
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raise
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return (None, pos)
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class PDFXRefStream(PDFBaseXRef):
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def __init__(self):
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self.data = None
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self.entlen = None
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self.fl1 = self.fl2 = self.fl3 = None
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self.objid_ranges = []
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def __repr__(self):
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return '<PDFXRefStream: fields=%d,%d,%d>' % (self.fl1, self.fl2, self.fl3)
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def load(self, parser):
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(_,objid) = parser.nexttoken() # ignored
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(_,genno) = parser.nexttoken() # ignored
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(_,kwd) = parser.nexttoken()
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(_,stream) = parser.nextobject()
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if not isinstance(stream, PDFStream) or stream['Type'] is not LITERAL_XREF:
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raise PDFNoValidXRef('Invalid PDF stream spec.')
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size = stream['Size']
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index_array = stream.get('Index', (0,size))
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if len(index_array) % 2 != 0:
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raise PDFSyntaxError('Invalid index number')
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self.objid_ranges.extend( ObjIdRange(start, nobjs)
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for (start,nobjs) in choplist(2, index_array) )
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(self.fl1, self.fl2, self.fl3) = stream['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.attrs
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if logger.getEffectiveLevel() <= logging.DEBUG:
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logger.debug('xref stream: objid=%s, fields=%d,%d,%d',
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', '.join(map(repr, self.objid_ranges)), self.fl1, self.fl2, self.fl3)
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def get_trailer(self):
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return self.trailer
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def get_objids(self):
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for objid_range in self.objid_ranges:
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for x in range(objid_range.get_start_id(), objid_range.get_end_id()+1):
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yield x
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def get_pos(self, objid):
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offset = 0
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found = False
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for objid_range in self.objid_ranges:
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if objid >= objid_range.get_start_id() and objid <= objid_range.get_end_id():
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offset += objid - objid_range.get_start_id()
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found = True
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break
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else:
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offset += objid_range.get_nobjs()
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if not found: raise KeyError(objid)
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i = self.entlen * offset
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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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# this is a free object
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raise KeyError(objid)
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class PDFPage:
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"""An object that holds the information about a page.
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A PDFPage object is merely a convenience class that has a set
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of keys and values, which describe the properties of a page
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and point to its contents.
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Attributes:
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doc: a PDFDocument object.
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pageid: any Python object that can uniquely identify the page.
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attrs: a dictionary of page attributes.
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contents: a list of PDFStream objects that represents the page content.
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lastmod: the last modified time of the page.
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resources: a list of resources used by the page.
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mediabox: the physical size of the page.
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cropbox: the crop rectangle of the page.
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rotate: the page rotation (in degree).
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annots: the page annotations.
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beads: a chain that represents natural reading order.
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"""
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def __init__(self, doc, pageid, attrs):
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"""Initialize a page object.
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doc: a PDFDocument object.
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pageid: any Python object that can uniquely identify the page.
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attrs: a dictionary of page attributes.
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"""
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self.doc = doc
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self.pageid = pageid
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self.attrs = dict_value(attrs)
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self.lastmod = resolve1(self.attrs.get('LastModified'))
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self.resources = resolve1(self.attrs['Resources'])
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self.mediabox = resolve1(self.attrs['MediaBox'])
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if 'CropBox' in self.attrs:
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self.cropbox = resolve1(self.attrs['CropBox'])
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else:
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self.cropbox = self.mediabox
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self.rotate = (self.attrs.get('Rotate', 0)+360) % 360
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self.annots = self.attrs.get('Annots')
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self.beads = self.attrs.get('B')
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if 'Contents' in self.attrs:
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contents = resolve1(self.attrs['Contents'])
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else:
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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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def __repr__(self):
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return '<PDFPage: Resources=%r, MediaBox=%r>' % (self.resources, self.mediabox)
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class PDFDocument:
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"""PDFDocument object represents a PDF document.
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Since a PDF file can be very big, normally it is not loaded at
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once. So PDF document has to cooperate with a PDF parser in order to
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dynamically import the data as processing goes.
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Typical usage:
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doc = PDFDocument()
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doc.set_parser(parser)
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doc.initialize(password)
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obj = doc.getobj(objid)
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"""
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KEYWORD_OBJ = KWD('obj')
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def __init__(self, caching=True):
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self.caching = caching
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self.xrefs = []
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self.info = []
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self.catalog = None
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self.encryption = None
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self.decipher = None
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self._parser = None
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self._cached_objs = {}
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self._parsed_objs = {}
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self._parsed_everything = False
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def _parse_next_object(self, parser):
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# This is a bit awkward and I suspect that it could be a lot more elegant, but it would
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# require refactoring the parsing process and I don't want to do that yet.
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stack = []
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_, token = parser.nexttoken()
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while token is not self.KEYWORD_OBJ:
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stack.append(token)
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_, token = parser.nexttoken()
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objid = stack[-2]
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genno = stack[-1]
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_, obj = parser.nextobject()
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return objid, genno, obj
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def _parse_objstream(self, stream):
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# ObjStm have a special organization. First, the param "N" tells how many objs we have in
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# there. Then, they start with a list of (objids, genno) pairs, and then the actual objects
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# come in.
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parser = PDFStreamParser(stream.get_data())
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parser.set_document(self)
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objcount = stream['N']
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objids = []
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for i in range(objcount):
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_, objid = parser.nextobject()
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_, genno = parser.nextobject()
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objids.append(objid)
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# Now we should be at the point where we read objects
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for objid in objids:
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_, obj = parser.nextobject()
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self._cached_objs[objid] = obj
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def _parse_whole(self, parser):
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while True:
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try:
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objid, genno, obj = self._parse_next_object(parser)
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self._cached_objs[objid] = obj
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if isinstance(obj, PDFStream) and obj.get('Type') is LITERAL_OBJSTM:
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obj.set_objid(objid, genno)
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self._parse_objstream(obj)
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except PSEOF:
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break
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def _parse_everything(self):
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# Sometimes, we have malformed xref, but we still want to manage to read the PDF. In cases
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# like these, the last resort is to read all objects at once so that our object reference
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# can finally be resolved. This is slower than the normal method, so ony use this when the
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# xref tables are corrupt/wrong/whatever.
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if self._parsed_everything:
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raise PDFAlreadyParsed()
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parser = self._parser
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parser.setpos(0)
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parser.reset()
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self._parse_whole(parser)
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self._parsed_everything = True
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def _getobj(self, objid):
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if not self.xrefs:
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raise PDFException('PDFDocument is not initialized')
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# logger.debug('getobj: objid=%r', objid)
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if objid in self._cached_objs:
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genno = 0
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obj = self._cached_objs[objid]
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else:
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strmid, index = self.find_obj_ref(objid)
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if index is None:
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handle_error(PDFSyntaxError, 'Cannot locate objid=%r' % objid)
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# return null for a nonexistent reference.
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return None
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if strmid:
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stream = self.getobj(strmid)
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if stream is None:
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return None
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stream = stream_value(stream)
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if stream.get('Type') is not LITERAL_OBJSTM:
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handle_error(PDFSyntaxError, 'Not a stream object: %r' % stream)
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try:
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n = stream['N']
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except KeyError:
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handle_error(PDFSyntaxError, 'N is not defined: %r' % stream)
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n = 0
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if strmid in self._parsed_objs:
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objs = self._parsed_objs[strmid]
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else:
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parser = PDFStreamParser(stream.get_data())
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parser.set_document(self)
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objs = []
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try:
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while True:
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_, obj = parser.nextobject()
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objs.append(obj)
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except PSEOF:
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pass
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if self.caching:
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self._parsed_objs[strmid] = objs
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genno = 0
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i = n*2+index
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try:
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obj = objs[i]
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except IndexError:
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raise PDFSyntaxError('Invalid object number: objid=%r' % (objid))
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if isinstance(obj, PDFStream):
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obj.set_objid(objid, 0)
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else:
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try:
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self._parser.setpos(index)
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except PSEOF:
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handle_error(PSEOF, 'Parser index out of bounds')
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return None
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(_,objid1) = self._parser.nexttoken() # objid
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(_,genno) = self._parser.nexttoken() # genno
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(_,kwd) = self._parser.nexttoken()
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# #### hack around malformed pdf files
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#assert objid1 == objid, (objid, objid1)
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if objid1 != objid:
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x = []
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while kwd is not self.KEYWORD_OBJ:
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(_,kwd) = self._parser.nexttoken()
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x.append(kwd)
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if x:
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objid1 = x[-2]
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genno = x[-1]
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# #### end hack around malformed pdf files
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if kwd is not self.KEYWORD_OBJ:
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raise PDFSyntaxError('Invalid object spec: offset=%r' % index)
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try:
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(_,obj) = self._parser.nextobject()
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if isinstance(obj, PDFStream):
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obj.set_objid(objid, genno)
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except PSEOF:
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return None
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# logger.debug('register: objid=%r: %r', objid, obj)
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if self.caching:
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self._cached_objs[objid] = obj
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if self.decipher:
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obj = decipher_all(self.decipher, objid, genno, obj)
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return obj
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def set_parser(self, parser):
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"Set the document to use a given PDFParser object."
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if self._parser:
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return
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self._parser = parser
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# Retrieve the information of each header that was appended
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# (maybe multiple times) at the end of the document.
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self.xrefs = parser.read_xref()
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for xref in self.xrefs:
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trailer = xref.get_trailer()
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if not trailer: continue
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# If there's an encryption info, remember it.
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if 'Encrypt' in trailer:
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#assert not self.encryption
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self.encryption = (list_value(trailer['ID']),
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dict_value(trailer['Encrypt']))
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if 'Info' in trailer:
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self.info.append(dict_value(trailer['Info']))
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if 'Root' in trailer:
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# Every PDF file must have exactly one /Root dictionary.
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self.catalog = dict_value(trailer['Root'])
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break
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else:
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raise PDFSyntaxError('No /Root object! - Is this really a PDF?')
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if self.catalog.get('Type') is not LITERAL_CATALOG:
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handle_error(PDFSyntaxError, 'Catalog not found!')
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# initialize(password='')
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# Perform the initialization with a given password.
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# This step is mandatory even if there's no password associated
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# with the document.
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PASSWORD_PADDING = b'(\xbfN^Nu\x8aAd\x00NV\xff\xfa\x01\x08..\x00\xb6\xd0h>\x80/\x0c\xa9\xfedSiz'
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def initialize(self, password=''):
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if not self.encryption:
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self.is_printable = self.is_modifiable = self.is_extractable = True
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return
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(docid, param) = self.encryption
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if literal_name(param.get('Filter')) != 'Standard':
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raise PDFEncryptionError('Unknown filter: param=%r' % param)
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V = int_value(param.get('V', 0))
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if not (V == 1 or V == 2):
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raise PDFEncryptionError('Unknown algorithm: param=%r' % param)
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length = int_value(param.get('Length', 40)) # Key length (bits)
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O = str_value(param['O'])
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R = int_value(param['R']) # Revision
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if 5 <= R:
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raise PDFEncryptionError('Unknown revision: %r' % R)
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U = str_value(param['U'])
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P = int_value(param['P'])
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self.is_printable = bool(P & 4)
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self.is_modifiable = bool(P & 8)
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self.is_extractable = bool(P & 16)
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# Algorithm 3.2
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# XXX is latin-1 the correct encoding???
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password = password.encode('latin-1')
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password = (password+self.PASSWORD_PADDING)[:32] # 1
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hash = md5.md5(password) # 2
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hash.update(O) # 3
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hash.update(struct.pack('<l', P)) # 4
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hash.update(docid[0]) # 5
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if 4 <= R:
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# 6
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raise PDFNotImplementedError('Revision 4 encryption is currently unsupported')
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if 3 <= R:
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# 8
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for _ in range(50):
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hash = md5.md5(hash.digest()[:length//8])
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key = hash.digest()[:length//8]
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|
if R == 2:
|
|
# Algorithm 3.4
|
|
u1 = Arcfour(key).process(self.PASSWORD_PADDING)
|
|
elif R == 3:
|
|
# Algorithm 3.5
|
|
hash = md5.md5(self.PASSWORD_PADDING) # 2
|
|
hash.update(docid[0]) # 3
|
|
x = Arcfour(key).process(hash.digest()[:16]) # 4
|
|
for i in range(1,19+1):
|
|
k = bytes( c ^ i for c in key )
|
|
x = Arcfour(k).process(x)
|
|
u1 = x+x # 32bytes total
|
|
if R == 2:
|
|
is_authenticated = (u1 == U)
|
|
else:
|
|
is_authenticated = (u1[:16] == U[:16])
|
|
if not is_authenticated:
|
|
raise PDFPasswordIncorrect
|
|
self.decrypt_key = key
|
|
self.decipher = self.decrypt_rc4 # XXX may be AES
|
|
|
|
def decrypt_rc4(self, objid, genno, data):
|
|
key = self.decrypt_key + struct.pack('<L',objid)[:3]+struct.pack('<L',genno)[:2]
|
|
hash = md5.md5(key)
|
|
key = hash.digest()[:min(len(key),16)]
|
|
return Arcfour(key).process(data)
|
|
|
|
def readobj(self):
|
|
"""Read the next object at current position.
|
|
|
|
The object doesn't have to start exactly where we are. We'll read the first
|
|
object that comes to us.
|
|
"""
|
|
return self._parse_next_object(self._parser)
|
|
|
|
def find_obj_ref(self, objid):
|
|
for xref in self.xrefs:
|
|
try:
|
|
strmid, index = xref.get_pos(objid)
|
|
return strmid, index
|
|
except KeyError:
|
|
pass
|
|
else:
|
|
# return null for a nonexistent reference.
|
|
return None, None
|
|
|
|
def getobj(self, objid):
|
|
result = self._getobj(objid)
|
|
if result is None:
|
|
try:
|
|
self._parse_everything()
|
|
result = self._getobj(objid)
|
|
except PDFAlreadyParsed:
|
|
result = None
|
|
return result
|
|
|
|
INHERITABLE_ATTRS = {'Resources', 'MediaBox', 'CropBox', 'Rotate'}
|
|
def get_pages(self):
|
|
if not self.xrefs:
|
|
raise PDFException('PDFDocument is not initialized')
|
|
def search(obj, parent):
|
|
try:
|
|
if isinstance(obj, int):
|
|
objid = obj
|
|
tree = dict_value(self.getobj(objid), strict=True).copy()
|
|
else:
|
|
objid = obj.objid
|
|
tree = dict_value(obj, strict=True).copy()
|
|
except PDFTypeError:
|
|
return
|
|
for (k,v) in parent.items():
|
|
if k in self.INHERITABLE_ATTRS and k not in tree:
|
|
tree[k] = v
|
|
if tree.get('Type') is LITERAL_PAGES and 'Kids' in tree:
|
|
logger.debug('Pages: Kids=%r', tree['Kids'])
|
|
for c in list_value(tree['Kids']):
|
|
for x in search(c, tree):
|
|
yield x
|
|
elif tree.get('Type') is LITERAL_PAGE:
|
|
logger.debug('Page: %r', tree)
|
|
yield (objid, tree)
|
|
if 'Pages' not in self.catalog:
|
|
return
|
|
for (pageid,tree) in search(self.catalog['Pages'], self.catalog):
|
|
yield PDFPage(self, pageid, tree)
|
|
|
|
def get_outlines(self):
|
|
if 'Outlines' not in self.catalog:
|
|
raise PDFNoOutlines
|
|
def search(entry, level):
|
|
entry = dict_value(entry)
|
|
if 'Title' in entry:
|
|
if 'A' in entry or 'Dest' in entry:
|
|
title = decode_text(str_value(entry['Title']))
|
|
dest = entry.get('Dest')
|
|
action = entry.get('A')
|
|
se = entry.get('SE')
|
|
yield (level, title, dest, action, se)
|
|
if 'First' in entry and 'Last' in entry:
|
|
for x in search(entry['First'], level+1):
|
|
yield x
|
|
if 'Next' in entry:
|
|
for x in search(entry['Next'], level):
|
|
yield x
|
|
return search(self.catalog['Outlines'], 0)
|
|
|
|
def lookup_name(self, cat, key):
|
|
try:
|
|
names = dict_value(self.catalog['Names'])
|
|
except (PDFTypeError, KeyError):
|
|
raise KeyError((cat,key))
|
|
# may raise KeyError
|
|
d0 = dict_value(names[cat])
|
|
def lookup(d):
|
|
if 'Limits' in d:
|
|
(k1,k2) = list_value(d['Limits'])
|
|
if key < k1 or k2 < key: return None
|
|
if 'Names' in d:
|
|
objs = list_value(d['Names'])
|
|
names = dict(choplist(2, objs))
|
|
return names[key]
|
|
if 'Kids' in d:
|
|
for c in list_value(d['Kids']):
|
|
v = lookup(dict_value(c))
|
|
if v: return v
|
|
raise KeyError((cat,key))
|
|
return lookup(d0)
|
|
|
|
def get_dest(self, name):
|
|
try:
|
|
# PDF-1.2 or later
|
|
obj = self.lookup_name('Dests', name)
|
|
except KeyError:
|
|
# PDF-1.1 or prior
|
|
if 'Dests' not in self.catalog:
|
|
raise PDFDestinationNotFound(name)
|
|
d0 = dict_value(self.catalog['Dests'])
|
|
if name not in d0:
|
|
raise PDFDestinationNotFound(name)
|
|
obj = d0[name]
|
|
return obj
|
|
|
|
|
|
class PDFParser(PSStackParser):
|
|
|
|
"""
|
|
PDFParser fetch PDF objects from a file stream.
|
|
It can handle indirect references by referring to
|
|
a PDF document set by set_document method.
|
|
It also reads XRefs at the end of every PDF file.
|
|
|
|
Typical usage:
|
|
parser = PDFParser(fp)
|
|
parser.read_xref()
|
|
parser.set_document(doc)
|
|
parser.seek(offset)
|
|
parser.nextobject()
|
|
|
|
"""
|
|
|
|
def __init__(self, fp):
|
|
PSStackParser.__init__(self, fp)
|
|
self.doc = None
|
|
self.fallback = False
|
|
|
|
def set_document(self, doc):
|
|
"""Associates the parser with a PDFDocument object."""
|
|
self.doc = doc
|
|
|
|
KEYWORD_R = KWD('R')
|
|
KEYWORD_NULL = KWD('null')
|
|
KEYWORD_ENDOBJ = KWD('endobj')
|
|
KEYWORD_STREAM = KWD('stream')
|
|
KEYWORD_XREF = KWD('xref')
|
|
KEYWORD_STARTXREF = KWD('startxref')
|
|
def do_keyword(self, pos, token):
|
|
"""Handles PDF-related keywords."""
|
|
|
|
if token in (self.KEYWORD_XREF, self.KEYWORD_STARTXREF):
|
|
self.add_results(*self.pop(1))
|
|
|
|
elif token is self.KEYWORD_ENDOBJ:
|
|
self.add_results(*self.pop(4))
|
|
|
|
elif token is self.KEYWORD_NULL:
|
|
# null object
|
|
self.push((pos, None))
|
|
|
|
elif token is self.KEYWORD_R:
|
|
# reference to indirect object
|
|
try:
|
|
((_,objid), (_,genno)) = self.pop(2)
|
|
(objid, genno) = (int(objid), int(genno))
|
|
obj = PDFObjRef(self.doc, objid, genno)
|
|
self.push((pos, obj))
|
|
except PSSyntaxError:
|
|
pass
|
|
|
|
elif token is self.KEYWORD_STREAM:
|
|
# stream object
|
|
((_,dic),) = self.pop(1)
|
|
dic = dict_value(dic)
|
|
try:
|
|
objlen = int_value(dic['Length'])
|
|
except KeyError:
|
|
handle_error(PDFSyntaxError, '/Length is undefined: %r' % dic)
|
|
objlen = 0
|
|
self.setpos(pos)
|
|
try:
|
|
(_, line) = self.nextline() # 'stream'
|
|
except PSEOF:
|
|
handle_error(PDFSyntaxError, 'Unexpected EOF')
|
|
return
|
|
pos += len(line)
|
|
endpos = pos + objlen
|
|
if 'endstream' not in self.data[endpos:endpos+len('endstream')+2]:
|
|
r = re.compile(r'(\r\n|\r|\n)endstream')
|
|
m = r.search(self.data, pos)
|
|
if m is None:
|
|
raise PDFSyntaxError("stream with no endstream")
|
|
endpos = m.start()
|
|
data = self.data[pos:endpos].encode('latin-1')
|
|
self.setpos(endpos)
|
|
self.nexttoken() # consume 'endstream'
|
|
# XXX limit objlen not to exceed object boundary
|
|
# logger.debug('Stream: pos=%d, objlen=%d, dic=%r, data=%r...', pos, objlen, dic, data[:10])
|
|
obj = PDFStream(dic, data, self.doc.decipher)
|
|
self.push((pos, obj))
|
|
|
|
else:
|
|
# others
|
|
self.push((pos, token))
|
|
|
|
|
|
def find_xref(self):
|
|
"""Internal function used to locate the first XRef."""
|
|
# the word 'startxref' followed by a newline followed by digits
|
|
re_startxref = re.compile(r'startxref\s*[\r\n]+\s*(\d+)', re.MULTILINE)
|
|
# try at the end, then try the whole file.
|
|
m = re_startxref.findall(self.data, len(self.data)-4096)
|
|
if not m:
|
|
m = re_startxref.findall(self.data)
|
|
if not m:
|
|
raise PDFNoValidXRef('Unexpected EOF')
|
|
logger.debug('xref found: pos=%r', m[-1])
|
|
return int(m[-1])
|
|
|
|
# read xref table
|
|
def read_xref_from(self, start, xrefs):
|
|
"""Reads XRefs from the given location."""
|
|
self.setpos(start)
|
|
self.reset()
|
|
try:
|
|
(pos, token) = self.nexttoken()
|
|
except PSEOF:
|
|
raise PDFNoValidXRef('Unexpected EOF')
|
|
# logger.debug('read_xref_from: start=%d, token=%r', start, token)
|
|
if isinstance(token, int):
|
|
# XRefStream: PDF-1.5
|
|
self.setpos(pos)
|
|
self.reset()
|
|
xref = PDFXRefStream()
|
|
xref.load(self)
|
|
else:
|
|
if token is self.KEYWORD_XREF:
|
|
self.nextline()
|
|
xref = PDFXRef()
|
|
xref.load(self)
|
|
xrefs.append(xref)
|
|
trailer = xref.get_trailer()
|
|
logger.debug('trailer: %r', trailer)
|
|
if 'XRefStm' in trailer:
|
|
pos = int_value(trailer['XRefStm'])
|
|
self.read_xref_from(pos, xrefs)
|
|
if 'Prev' in trailer:
|
|
# find previous xref
|
|
pos = int_value(trailer['Prev'])
|
|
self.read_xref_from(pos, xrefs)
|
|
|
|
# read xref tables and trailers
|
|
def read_xref(self):
|
|
"""Reads all the XRefs in the PDF file and returns them."""
|
|
xrefs = []
|
|
try:
|
|
pos = self.find_xref()
|
|
self.read_xref_from(pos, xrefs)
|
|
except PDFNoValidXRef:
|
|
# fallback
|
|
logger.debug('no xref, fallback')
|
|
self.fallback = True
|
|
xref = PDFXRef()
|
|
xref.load_fallback(self)
|
|
xrefs.append(xref)
|
|
return xrefs
|
|
|
|
|
|
class PDFStreamParser(PDFParser):
|
|
|
|
"""
|
|
PDFStreamParser is used to parse PDF content streams
|
|
that is contained in each page and has instructions
|
|
for rendering the page. A reference to a PDF document is
|
|
needed because a PDF content stream can also have
|
|
indirect references to other objects in the same document.
|
|
"""
|
|
|
|
def __init__(self, data):
|
|
PDFParser.__init__(self, io.BytesIO(data))
|
|
|
|
def flush(self):
|
|
self.add_results(*self.popall())
|
|
|
|
def do_keyword(self, pos, token):
|
|
if token is self.KEYWORD_R:
|
|
# reference to indirect object
|
|
try:
|
|
((_,objid), (_,genno)) = self.pop(2)
|
|
(objid, genno) = (int(objid), int(genno))
|
|
obj = PDFObjRef(self.doc, objid, genno)
|
|
self.push((pos, obj))
|
|
except PSSyntaxError:
|
|
pass
|
|
return
|
|
# others
|
|
self.push((pos, token))
|