1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
|
# A part of pdfrw (pdfrw.googlecode.com)
# Copyright (C) 2006-2009 Patrick Maupin, Austin, Texas
# MIT license -- See LICENSE.txt for details
'''
The PdfReader class reads an entire PDF file into memory and
parses the top-level container objects. (It does not parse
into streams.) The object subclasses PdfDict, and the
document pages are stored in a list in the pages attribute
of the object.
'''
from pdftokens import PdfTokens
from pdfobjects import PdfDict, PdfArray, PdfName
from pdfcompress import uncompress
class PdfReader(PdfDict):
class unresolved:
# Used as a placeholder until we have an object.
pass
def readindirect(self, objnum, gennum):
''' Read an indirect object. If it has already
been read, return it from the cache.
'''
def setobj(obj):
# Store the new object in the dictionary
# once we have its value
record[1] = obj
def ordinary(source, setobj, obj):
# Deal with an ordinary (non-array, non-dict) object
setobj(obj)
return obj
fdata, objnum, gennum = self.fdata, int(objnum), int(gennum)
record = self.indirect_objects[fdata, objnum, gennum]
if record[1] is not self.unresolved:
return record[1]
# Read the object header and validate it
source = PdfTokens(fdata, record[0])
objid = source.multiple(3)
assert int(objid[0]) == objnum, objid
assert int(objid[1]) == gennum, objid
assert objid[2] == 'obj', objid
# Read the object, and call special code if it starts
# an array or dictionary
obj = source.next()
obj = self.special.get(obj, ordinary)(source, setobj, obj)
self.readstream(obj, source)
obj.indirect = True
return obj
def readstream(obj, source):
''' Read optional stream following a dictionary
object.
'''
tok = source.next()
if tok == 'endobj':
return # No stream
assert isinstance(obj, PdfDict)
assert tok == 'stream', tok
fdata = source.fdata
floc = fdata.rindex(tok, 0, source.floc) + len(tok)
ch = fdata[floc]
if ch == '\r':
floc += 1
ch = fdata[floc]
assert ch == '\n'
startstream = floc + 1
endstream = startstream + int(obj.Length)
obj._stream = fdata[startstream:endstream]
source = PdfTokens(fdata, endstream)
endit = source.multiple(2)
if endit != 'endstream endobj'.split():
# /Length attribute is broken, try to read stream
# anyway disregarding the specified value
# TODO: issue warning here once we have some kind of
# logging
endstream = fdata.index('endstream', startstream)
if fdata[endstream-2:endstream] == '\r\n':
endstream -= 2
elif fdata[endstream-1] in ['\n', '\r']:
endstream -= 1
source = PdfTokens(fdata, endstream)
endit = source.multiple(2)
assert endit == 'endstream endobj'.split()
obj.Length = str(endstream-startstream)
obj._stream = fdata[startstream:endstream]
readstream = staticmethod(readstream)
def readarray(self, source, setobj=lambda x:None, original=None):
special = self.special
result = PdfArray()
setobj(result)
for value in source:
if value == ']':
break
if value in special:
value = special[value](source)
elif value == 'R':
generation = result.pop()
value = self.readindirect(result.pop(), generation)
result.append(value)
return result
def readdict(self, source, setobj=lambda x:None, original=None):
special = self.special
result = PdfDict()
setobj(result)
tok = source.next()
while tok != '>>':
assert tok.startswith('/'), (tok, source.multiple(10))
key = tok
value = source.next()
if value in special:
value = special[value](source)
tok = source.next()
else:
tok = source.next()
if value.isdigit() and tok.isdigit():
assert source.next() == 'R'
value = self.readindirect(value, tok)
tok = source.next()
result[key] = value
return result
def readxref(fdata):
startloc = fdata.rindex('startxref')
xrefinfo = list(PdfTokens(fdata, startloc, False))
assert len(xrefinfo) == 3, xrefinfo
assert xrefinfo[0] == 'startxref', xrefinfo[0]
assert xrefinfo[1].isdigit(), xrefinfo[1]
assert xrefinfo[2].rstrip() == '%%EOF', repr(xrefinfo[2])
return startloc, PdfTokens(fdata, int(xrefinfo[1]))
readxref = staticmethod(readxref)
def parsexref(self, source):
tok = source.next()
assert tok == 'xref', tok
while 1:
tok = source.next()
if tok == 'trailer':
break
startobj = int(tok)
for objnum in range(startobj, startobj + int(source.next())):
offset = int(source.next())
generation = int(source.next())
if source.next() == 'n':
objid = self.fdata, objnum, generation
objval = [offset, self.unresolved]
self.indirect_objects.setdefault(objid, objval)
pagename = PdfName.Page
pagesname = PdfName.Pages
def readpages(self, node):
# PDFs can have arbitrarily nested Pages/Page
# dictionary structures.
if node.Type == self.pagename:
return [node]
assert node.Type == self.pagesname, node.Type
result = []
for node in node.Kids:
result.extend(self.readpages(node))
return result
def __init__(self, fname=None, fdata=None, decompress=True):
if fname is not None:
assert fdata is None
# Allow reading preexisting streams like pyPdf
if hasattr(fname, 'read'):
fdata = fname.read()
else:
f = open(fname, 'rb')
fdata = f.read()
f.close()
assert fdata is not None
fdata = fdata.rstrip('\00')
self.private.fdata = fdata
self.private.indirect_objects = {}
self.private.special = {'<<': self.readdict, '[': self.readarray}
startloc, source = self.readxref(fdata)
self.parsexref(source)
assert source.next() == '<<'
self.update(self.readdict(source))
assert source.next() == 'startxref' and source.floc > startloc
self.private.pages = self.readpages(self.Root.Pages)
if decompress:
self.uncompress()
# For compatibility with pyPdf
self.private.numPages = len(self.pages)
# For compatibility with pyPdf
def getPage(self, pagenum):
return self.pages[pagenum]
def uncompress(self):
uncompress([x[1] for x in self.indirect_objects.itervalues()])
|
