# coding: utf-8 r""" weasyprint.pdf -------------- Post-process the PDF files created by cairo and add metadata such as hyperlinks and bookmarks. Rather than trying to parse any valid PDF, we make some assumptions that hold for cairo in order to simplify the code: * All newlines are '\n', not '\r' or '\r\n' * Except for number 0 (which is always free) there is no "free" object. * Most white space separators are made of a single 0x20 space. * Indirect dictionary objects do not contain '>>' at the start of a line except to mark the end of the object, followed by 'endobj'. (In other words, '>>' markers for sub-dictionaries are indented.) * The Page Tree is flat: all kids of the root page node are page objects, not page tree nodes. However the code uses a lot of assert statements so that if an assumptions is not true anymore, the code should (hopefully) fail with an exception rather than silently behave incorrectly. :copyright: Copyright 2011-2014 Simon Sapin and contributors, see AUTHORS. :license: BSD, see LICENSE for details. """ from __future__ import division, unicode_literals import hashlib import io import mimetypes import os import re import string import sys import zlib import cairocffi as cairo from . import VERSION_STRING, Attachment from .compat import xrange, iteritems, izip, unquote from .urls import iri_to_uri, urlsplit, URLFetchingError from .html import W3C_DATE_RE from .logger import LOGGER def pdf_escape(value): """Escape parentheses and backslashes in ``value``. ``value`` must be unicode, or latin1 bytestring. """ if isinstance(value, bytes): value = value.decode('latin1') return value.translate({40: r'\(', 41: r'\)', 92: r'\\'}) class PDFFormatter(string.Formatter): """Like str.format except: * Results are byte strings * The new !P conversion flags encodes a PDF string. (UTF-16 BE with a BOM, then backslash-escape parentheses.) Except for fields marked !P, everything should be ASCII-only. """ def convert_field(self, value, conversion): if conversion == 'P': # Make a round-trip back through Unicode for the .translate() # method. (bytes.translate only maps to single bytes.) # Use latin1 to map all byte values. return '({0})'.format(pdf_escape( ('\ufeff' + value).encode('utf-16-be').decode('latin1'))) else: return super(PDFFormatter, self).convert_field(value, conversion) def vformat(self, format_string, args, kwargs): result = super(PDFFormatter, self).vformat(format_string, args, kwargs) return result.encode('latin1') pdf_format = PDFFormatter().format class PDFDictionary(object): def __init__(self, object_number, byte_string): self.object_number = object_number self.byte_string = byte_string def __repr__(self): return self.__class__.__name__ + repr( (self.object_number, self.byte_string)) _re_cache = {} def get_value(self, key, value_re): regex = self._re_cache.get((key, value_re)) if not regex: regex = re.compile(pdf_format('/{0} {1}', key, value_re)) self._re_cache[key, value_re] = regex return regex.search(self.byte_string).group(1) def get_type(self): """ :returns: the value for the /Type key. """ # No end delimiter, + defaults to greedy return self.get_value('Type', '/(\w+)').decode('ascii') def get_indirect_dict(self, key, pdf_file): """Read the value for `key` and follow the reference, assuming it is an indirect dictionary object. :return: a new PDFDictionary instance. """ object_number = int(self.get_value(key, '(\d+) 0 R')) return type(self)(object_number, pdf_file.read_object(object_number)) def get_indirect_dict_array(self, key, pdf_file): """Read the value for `key` and follow the references, assuming it is an array of indirect dictionary objects. :return: a list of new PDFDictionary instance. """ parts = self.get_value(key, '\[(.+?)\]').split(b' 0 R') # The array looks like this: ' 0 R 0 R 0 R ' # so `parts` ends up like this [' ', ' ', ' ', ' '] # With the trailing white space in the list. trail = parts.pop() assert not trail.strip() class_ = type(self) read = pdf_file.read_object return [class_(n, read(n)) for n in map(int, parts)] class PDFFile(object): """ :param fileobj: A seekable binary file-like object for a PDF generated by cairo. """ trailer_re = re.compile( b'\ntrailer\n(.+)\nstartxref\n(\d+)\n%%EOF\n$', re.DOTALL) def __init__(self, fileobj): # cairo’s trailer only has Size, Root and Info. # The trailer + startxref + EOF is typically under 100 bytes fileobj.seek(-200, os.SEEK_END) trailer, startxref = self.trailer_re.search(fileobj.read()).groups() trailer = PDFDictionary(None, trailer) startxref = int(startxref) fileobj.seek(startxref) line = next(fileobj) assert line == b'xref\n' line = next(fileobj) first_object, total_objects = line.split() assert first_object == b'0' total_objects = int(total_objects) line = next(fileobj) assert line == b'0000000000 65535 f \n' objects_offsets = [None] for object_number in xrange(1, total_objects): line = next(fileobj) assert line[10:] == b' 00000 n \n' objects_offsets.append(int(line[:10])) self.fileobj = fileobj #: Maps object number -> bytes from the start of the file self.objects_offsets = objects_offsets info = trailer.get_indirect_dict('Info', self) catalog = trailer.get_indirect_dict('Root', self) page_tree = catalog.get_indirect_dict('Pages', self) pages = page_tree.get_indirect_dict_array('Kids', self) # Check that the tree is flat assert all(p.get_type() == 'Page' for p in pages) self.startxref = startxref self.info = info self.catalog = catalog self.page_tree = page_tree self.pages = pages self.finished = False self.overwritten_objects_offsets = {} self.new_objects_offsets = [] def read_object(self, object_number): """ :param object_number: An integer N so that 1 <= N < len(self.objects_offsets) :returns: The object content as a byte string. """ fileobj = self.fileobj fileobj.seek(self.objects_offsets[object_number]) line = next(fileobj) assert line.endswith(b' 0 obj\n') assert int(line[:-7]) == object_number # len(b' 0 obj\n') == 7 object_lines = [] for line in fileobj: if line == b'>>\n': assert next(fileobj) == b'endobj\n' # No newline, we’ll add it when writing. object_lines.append(b'>>') return b''.join(object_lines) object_lines.append(line) def overwrite_object(self, object_number, byte_string): """Write the new content for an existing object at the end of the file. :param object_number: An integer N so that 1 <= N < len(self.objects_offsets) :param byte_string: The new object content as a byte string. """ self.overwritten_objects_offsets[object_number] = ( self._write_object(object_number, byte_string)) def extend_dict(self, dictionary, new_content): """Overwrite a dictionary object after adding content inside the << >> delimiters. """ assert dictionary.byte_string.endswith(b'>>') self.overwrite_object( dictionary.object_number, dictionary.byte_string[:-2] + new_content + b'\n>>') def next_object_number(self): """Return the object number that would be used by write_new_object(). """ return len(self.objects_offsets) + len(self.new_objects_offsets) def write_new_object(self, byte_string): """Write a new object at the end of the file. :param byte_string: The object content as a byte string. :return: The new object number. """ object_number = self.next_object_number() self.new_objects_offsets.append( self._write_object(object_number, byte_string)) return object_number def finish(self): """ Write the cross-reference table and the trailer for the new and overwritten objects. This makes `fileobj` a valid (updated) PDF file. """ new_startxref, write = self._start_writing() self.finished = True write(b'xref\n') # Don’t bother sorting or finding contiguous numbers, # just write a new sub-section for each overwritten object. for object_number, offset in iteritems( self.overwritten_objects_offsets): write(pdf_format( '{0} 1\n{1:010} 00000 n \n', object_number, offset)) if self.new_objects_offsets: first_new_object = len(self.objects_offsets) write(pdf_format( '{0} {1}\n', first_new_object, len(self.new_objects_offsets))) for object_number, offset in enumerate( self.new_objects_offsets, start=first_new_object): write(pdf_format('{0:010} 00000 n \n', offset)) write(pdf_format( 'trailer\n<< ' '/Size {size} /Root {root} 0 R /Info {info} 0 R /Prev {prev}' ' >>\nstartxref\n{startxref}\n%%EOF\n', size=self.next_object_number(), root=self.catalog.object_number, info=self.info.object_number, prev=self.startxref, startxref=new_startxref)) def _write_object(self, object_number, byte_string): offset, write = self._start_writing() write(pdf_format('{0} 0 obj\n', object_number)) write(byte_string) write(b'\nendobj\n') return offset def _start_writing(self): assert not self.finished fileobj = self.fileobj fileobj.seek(0, os.SEEK_END) return fileobj.tell(), fileobj.write def flatten_bookmarks(bookmarks, depth=1): for label, target, children in bookmarks: yield label, target, depth for result in flatten_bookmarks(children, depth + 1): yield result def prepare_metadata(document, bookmark_root_id, scale): """Change metadata into data structures closer to the PDF objects. In particular, convert from WeasyPrint units (CSS pixels from the top-left corner) to PDF units (points from the bottom-left corner.) :param scale: PDF points per CSS pixels. Defaults to 0.75, but is affected by `zoom` in :meth:`weasyprint.document.Document.write_pdf`. """ # X and width unchanged; Y’ = page_height - Y; height’ = -height matrices = [cairo.Matrix(xx=scale, yy=-scale, y0=page.height * scale) for page in document.pages] links = [] for page_links, matrix in izip(document.resolve_links(), matrices): new_page_links = [] for link_type, target, rectangle in page_links: if link_type == 'internal': target_page, target_x, target_y = target target = ( (target_page,) + matrices[target_page].transform_point(target_x, target_y)) rect_x, rect_y, width, height = rectangle rect_x, rect_y = matrix.transform_point(rect_x, rect_y) width, height = matrix.transform_distance(width, height) # x, y, w, h => x0, y0, x1, y1 rectangle = rect_x, rect_y, rect_x + width, rect_y + height new_page_links.append((link_type, target, rectangle)) links.append(new_page_links) bookmark_root = {'Count': 0} bookmark_list = [] last_id_by_depth = [bookmark_root_id] last_by_depth = [bookmark_root] for bookmark_id, (label, target, depth) in enumerate( flatten_bookmarks(document.make_bookmark_tree()), bookmark_root_id + 1): target_page, target_x, target_y = target target = (target_page,) + matrices[target_page].transform_point( target_x, target_y) bookmark = { 'Count': 0, 'First': None, 'Last': None, 'Prev': None, 'Next': None, 'Parent': last_id_by_depth[depth - 1], 'label': label, 'target': target} if depth > len(last_by_depth) - 1: last_by_depth[depth - 1]['First'] = bookmark_id else: # The bookmark is sibling of last_id_by_depth[depth] bookmark['Prev'] = last_id_by_depth[depth] last_by_depth[depth]['Next'] = bookmark_id # Remove the bookmarks with a depth higher than the current one del last_by_depth[depth:] del last_id_by_depth[depth:] for i in range(depth): last_by_depth[i]['Count'] += 1 last_by_depth[depth - 1]['Last'] = bookmark_id last_by_depth.append(bookmark) last_id_by_depth.append(bookmark_id) bookmark_list.append(bookmark) return bookmark_root, bookmark_list, links def _write_compressed_file_object(pdf, file): """ Write a file like object as ``/EmbeddedFile``, compressing it with deflate. In fact, this method writes multiple PDF objects to include length, compressed length and MD5 checksum. :return: the object number of the compressed file stream object """ object_number = pdf.next_object_number() # Make sure we stay in sync with our object numbers expected_next_object_number = object_number + 4 length_number = object_number + 1 md5_number = object_number + 2 uncompressed_length_number = object_number + 3 offset, write = pdf._start_writing() write(pdf_format('{0} 0 obj\n', object_number)) write(pdf_format( '<< /Type /EmbeddedFile /Length {0} 0 R /Filter ' '/FlateDecode /Params << /CheckSum {1} 0 R /Size {2} 0 R >> >>\n', length_number, md5_number, uncompressed_length_number)) write(b'stream\n') uncompressed_length = 0 compressed_length = 0 md5 = hashlib.md5() compress = zlib.compressobj() for data in iter(lambda: file.read(4096), b''): uncompressed_length += len(data) md5.update(data) compressed = compress.compress(data) compressed_length += len(compressed) write(compressed) compressed = compress.flush(zlib.Z_FINISH) compressed_length += len(compressed) write(compressed) write(b'\nendstream\n') write(b'endobj\n') pdf.new_objects_offsets.append(offset) pdf.write_new_object(pdf_format("{0}", compressed_length)) pdf.write_new_object(pdf_format("<{0}>", md5.hexdigest())) pdf.write_new_object(pdf_format("{0}", uncompressed_length)) assert pdf.next_object_number() == expected_next_object_number return object_number def _get_filename_from_result(url, result): """ Derives a filename from a fetched resource. This is either the filename returned by the URL fetcher, the last URL path component or a synthetic name if the URL has no path """ filename = None # A given filename will always take precedence if result: filename = result.get('filename') if filename: return filename # The URL path likely contains a filename, which is a good second guess if url: split = urlsplit(url) if split.scheme != 'data': filename = split.path.split("/")[-1] if filename == '': filename = None if filename is None: # The URL lacks a path altogether. Use a synthetic name. # Using guess_extension is a great idea, but sadly the extension is # probably random, depending on the alignment of the stars, which car # you're driving and which software has been installed on your machine. # # Unfortuneatly this isn't even imdepodent on one machine, because the # extension can depend on PYTHONHASHSEED if mimetypes has multiple # extensions to offer extension = None if result: mime_type = result.get('mime_type') if mime_type == 'text/plain': # text/plain has a phletora of extensions - all garbage extension = '.txt' else: extension = mimetypes.guess_extension(mime_type) or '.bin' else: extension = '.bin' filename = 'attachment' + extension else: if sys.version_info[0] < 3: # Python 3 unquotes with UTF-8 per default, here we have to do it # manually # TODO: this assumes that the filename has been quoted as UTF-8. # I'm not sure if this assumption holds, as there is some magic # involved with filesystem encoding in other parts of the code filename = unquote(filename) if not isinstance(filename, bytes): filename = filename.encode('latin1') filename = filename.decode('utf-8') else: filename = unquote(filename) return filename def _write_pdf_embedded_files(pdf, attachments, url_fetcher): """ Writes attachments as embedded files (document attachments). :return: the object number of the name dictionary or :obj:`None` """ file_spec_ids = [] for attachment in attachments: file_spec_id = _write_pdf_attachment(pdf, attachment, url_fetcher) if file_spec_id is not None: file_spec_ids.append(file_spec_id) # We might have failed to write any attachment at all if len(file_spec_ids) == 0: return None content = [b'<< /Names ['] for fs in file_spec_ids: content.append(pdf_format('\n(attachment{0}) {0} 0 R ', fs)) content.append(b'\n] >>') return pdf.write_new_object(b''.join(content)) def _write_pdf_attachment(pdf, attachment, url_fetcher): """ Writes an attachment to the PDF stream :return: the object number of the ``/Filespec`` object or :obj:`None` if the attachment couldn't be read. """ try: # Attachments from document links like or can only be URLs. # They're passed in as tuples if isinstance(attachment, tuple): url, description = attachment attachment = Attachment( url=url, url_fetcher=url_fetcher, description=description) elif not isinstance(attachment, Attachment): attachment = Attachment(guess=attachment, url_fetcher=url_fetcher) with attachment.source as (source_type, source, url, _): if isinstance(source, bytes): source = io.BytesIO(source) file_stream_id = _write_compressed_file_object(pdf, source) except URLFetchingError as exc: LOGGER.warning('Failed to load attachment: %s', exc) return None # TODO: Use the result object from a URL fetch operation to provide more # details on the possible filename filename = _get_filename_from_result(url, None) return pdf.write_new_object(pdf_format( '<< /Type /Filespec /F () /UF {0!P} /EF << /F {1} 0 R >> ' '/Desc {2!P}\n>>', filename, file_stream_id, attachment.description or '')) def _write_pdf_annotation_files(pdf, links, url_fetcher): """ Write all annotation attachments to the PDF file. :return: a dictionary that maps URLs to PDF object numbers, which can be :obj:`None` if the resource failed to load. """ annot_files = {} for page_links in links: for link_type, target, rectangle in page_links: if link_type == 'attachment' and target not in annot_files: # TODO: use the title attribute as description annot_files[target] = _write_pdf_attachment( pdf, (target, None), url_fetcher) return annot_files def write_pdf_metadata(document, fileobj, scale, metadata, attachments, url_fetcher): """Append to a seekable file-like object to add PDF metadata.""" pdf = PDFFile(fileobj) bookmark_root_id = pdf.next_object_number() bookmark_root, bookmarks, links = prepare_metadata( document, bookmark_root_id, scale) if bookmarks: pdf.write_new_object(pdf_format( '<< /Type /Outlines /Count {0} /First {1} 0 R /Last {2} 0 R\n>>', bookmark_root['Count'], bookmark_root['First'], bookmark_root['Last'])) for bookmark in bookmarks: content = [pdf_format('<< /Title {0!P}\n', bookmark['label'])] page_num, pos_x, pos_y = bookmark['target'] content.append(pdf_format( '/A << /Type /Action /S /GoTo ' '/D [{0} 0 R /XYZ {1:f} {2:f} 0] >>\n', pdf.pages[page_num].object_number, pos_x, pos_y)) if bookmark['Count']: content.append(pdf_format('/Count {0}\n', bookmark['Count'])) for key in ['Parent', 'Prev', 'Next', 'First', 'Last']: if bookmark[key]: content.append(pdf_format( '/{0} {1} 0 R\n', key, bookmark[key])) content.append(b'>>') pdf.write_new_object(b''.join(content)) embedded_files_id = _write_pdf_embedded_files( pdf, metadata.attachments + (attachments or []), url_fetcher) if bookmarks or embedded_files_id is not None: params = b'' if bookmarks: params += pdf_format(' /Outlines {0} 0 R /PageMode /UseOutlines', bookmark_root_id) if embedded_files_id is not None: params += pdf_format(' /Names << /EmbeddedFiles {0} 0 R >>', embedded_files_id) pdf.extend_dict(pdf.catalog, params) # A single link can be split in multiple regions. We don't want to embedded # a file multiple times of course, so keep a reference to every embedded # URL and reuse the object number. # TODO: If we add support for descriptions this won't always be correct, # because two links might have the same href, but different titles. annot_files = _write_pdf_annotation_files(pdf, links, url_fetcher) # TODO: splitting a link into multiple independent rectangular annotations # works well for pure links, but rather mediocre for other annotations and # fails completely for transformed (CSS) or complex link shapes (area). # It would be better to use /AP for all links and coalesce link shapes that # originate from the same HTML link. This would give a feeling similiar to # what browsers do with links that span multiple lines. for page, page_links in zip(pdf.pages, links): annotations = [] for link_type, target, rectangle in page_links: content = [pdf_format( '<< /Type /Annot ' '/Rect [{0:f} {1:f} {2:f} {3:f}] /Border [0 0 0]\n', *rectangle)] if link_type != 'attachment' or annot_files[target] is None: content.append(b'/Subtype /Link ') if link_type == 'internal': content.append(pdf_format( '/A << /Type /Action /S /GoTo ' '/D [{0} /XYZ {1:f} {2:f} 0] >>\n', *target)) else: content.append(pdf_format( '/A << /Type /Action /S /URI /URI ({0}) >>\n', pdf_escape(iri_to_uri(target)))) else: assert not annot_files[target] is None link_ap = pdf.write_new_object(pdf_format( '<< /Type /XObject /Subtype /Form ' '/BBox [{0:f} {1:f} {2:f} {3:f}] /Length 0 >>\n' 'stream\n' 'endstream', *rectangle)) content.append(b'/Subtype /FileAttachment ') # evince needs /T or fails on an internal assertion. PDF # doesn't require it. content.append(pdf_format( '/T () /FS {0} 0 R /AP << /N {1} 0 R >>', annot_files[target], link_ap)) content.append(b'>>') annotations.append(pdf.write_new_object(b''.join(content))) if annotations: pdf.extend_dict(page, pdf_format( '/Annots [{0}]', ' '.join( '{0} 0 R'.format(n) for n in annotations))) info = [pdf_format('<< /Producer {0!P}\n', VERSION_STRING)] for attr, key in (('title', 'Title'), ('description', 'Subject'), ('generator', 'Creator')): value = getattr(metadata, attr) if value is not None: info.append(pdf_format('/{0} {1!P}', key, value)) for attr, key in (('authors', 'Author'), ('keywords', 'Keywords')): value = getattr(metadata, attr) if value is not None: info.append(pdf_format('/{0} {1!P}', key, ', '.join(value))) for attr, key in (('created', 'CreationDate'), ('modified', 'ModDate')): value = w3c_date_to_pdf(getattr(metadata, attr), attr) if value is not None: info.append(pdf_format('/{0} (D:{1})', key, value)) # TODO: write metadata['CreationDate'] and metadata['ModDate'] as dates. info.append(b' >>') pdf.overwrite_object(pdf.info.object_number, b''.join(info)) pdf.finish() def w3c_date_to_pdf(string, attr_name): """ YYYYMMDDHHmmSSOHH'mm' """ if string is None: return None match = W3C_DATE_RE.match(string) if match is None: LOGGER.warning('Invalid %s date: %r', attr_name, string) return None groups = match.groupdict() pdf_date = (groups['year'] + (groups['month'] or '') + (groups['day'] or '') + (groups['hour'] or '') + (groups['minute'] or '') + (groups['second'] or '')) if groups['hour']: assert groups['minute'] if not groups['second']: pdf_date += '00' if groups['tz_hour']: assert groups['tz_hour'].startswith(('+', '-')) assert groups['tz_minute'] pdf_date += "%s'%s'" % (groups['tz_hour'], groups['tz_minute']) else: pdf_date += 'Z' # UTC return pdf_date