166 lines
4.9 KiB
Python
166 lines
4.9 KiB
Python
#!/usr/bin/env python2
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import sys
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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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from psparser import PSStackParser
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from psparser import PSSyntaxError, PSEOF
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from psparser import KWD, STRICT
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from pdftypes import PDFException
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from pdftypes import PDFStream, PDFObjRef
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from pdftypes import int_value, float_value, num_value
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from pdftypes import str_value, list_value, dict_value, stream_value
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## Exceptions
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##
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class PDFSyntaxError(PDFException): pass
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## PDFParser
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##
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class PDFParser(PSStackParser):
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"""
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PDFParser fetch PDF objects from a file stream.
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It can handle indirect references by referring to
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a PDF document set by set_document method.
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It also reads XRefs at the end of every PDF file.
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Typical usage:
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parser = PDFParser(fp)
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parser.read_xref()
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parser.read_xref(fallback=True) # optional
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parser.set_document(doc)
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parser.seek(offset)
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parser.nextobject()
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"""
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def __init__(self, fp):
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PSStackParser.__init__(self, fp)
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self.doc = None
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self.fallback = False
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return
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def set_document(self, doc):
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"""Associates the parser with a PDFDocument object."""
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self.doc = doc
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return
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KEYWORD_R = KWD('R')
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KEYWORD_NULL = KWD('null')
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KEYWORD_ENDOBJ = KWD('endobj')
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KEYWORD_STREAM = KWD('stream')
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KEYWORD_XREF = KWD('xref')
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KEYWORD_STARTXREF = KWD('startxref')
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def do_keyword(self, pos, token):
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"""Handles PDF-related keywords."""
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if token in (self.KEYWORD_XREF, self.KEYWORD_STARTXREF):
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self.add_results(*self.pop(1))
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elif token is self.KEYWORD_ENDOBJ:
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self.add_results(*self.pop(4))
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elif token is self.KEYWORD_NULL:
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# null object
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self.push((pos, None))
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elif token is self.KEYWORD_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((pos, obj))
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except PSSyntaxError:
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pass
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elif token is self.KEYWORD_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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objlen = 0
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if not self.fallback:
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try:
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objlen = int_value(dic['Length'])
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except KeyError:
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if STRICT:
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raise PDFSyntaxError('/Length is undefined: %r' % dic)
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self.seek(pos)
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try:
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(_, line) = self.nextline() # 'stream'
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except PSEOF:
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if STRICT:
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raise PDFSyntaxError('Unexpected EOF')
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return
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pos += len(line)
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self.fp.seek(pos)
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data = self.fp.read(objlen)
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self.seek(pos+objlen)
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while 1:
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try:
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(linepos, line) = self.nextline()
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except PSEOF:
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if STRICT:
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raise PDFSyntaxError('Unexpected EOF')
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break
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if 'endstream' in line:
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i = line.index('endstream')
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objlen += i
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data += line[:i]
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break
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objlen += len(line)
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data += line
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self.seek(pos+objlen)
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# XXX limit objlen not to exceed object boundary
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if 2 <= self.debug:
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print >>sys.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, self.doc.decipher)
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self.push((pos, obj))
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else:
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# others
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self.push((pos, token))
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return
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## PDFStreamParser
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##
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class PDFStreamParser(PDFParser):
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"""
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PDFStreamParser is used to parse PDF content streams
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that is contained in each page and has instructions
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for rendering the page. A reference to a PDF document is
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needed because a PDF content stream can also have
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indirect references to other objects in the same document.
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"""
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def __init__(self, data):
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PDFParser.__init__(self, StringIO(data))
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return
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def flush(self):
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self.add_results(*self.popall())
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return
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def do_keyword(self, pos, token):
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if token is self.KEYWORD_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((pos, obj))
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except PSSyntaxError:
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pass
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return
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# others
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self.push((pos, token))
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return
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