mirror of
https://github.com/gryf/ebook-converter.git
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488 lines
18 KiB
Python
488 lines
18 KiB
Python
"""
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Splitting of the XHTML flows. Splitting can happen on page boundaries or can be
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forced at "likely" locations to conform to size limitations. This transform
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assumes a prior call to the flatcss transform.
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"""
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import os, functools, collections, re, copy
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from collections import OrderedDict
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import urllib.parse
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from lxml.etree import XPath as _XPath
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from lxml import etree
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from ebook_converter import as_unicode, force_unicode
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from ebook_converter.ebooks.epub import rules
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from ebook_converter.ebooks.oeb.base import (OEB_STYLES, XPNSMAP as NAMESPACES,
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rewrite_links, XHTML, urlnormalize)
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from ebook_converter.ebooks.oeb.polish.split import do_split
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from ebook_converter.polyglot.builtins import iteritems
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from ebook_converter.polyglot.urllib import unquote
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from ebook_converter.css_selectors import Select, SelectorError
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__license__ = 'GPL v3'
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__copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net'
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__docformat__ = 'restructuredtext en'
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XPath = functools.partial(_XPath, namespaces=NAMESPACES)
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SPLIT_POINT_ATTR = 'csp'
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def tostring(root):
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return etree.tostring(root, encoding='utf-8')
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class SplitError(ValueError):
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def __init__(self, path, root):
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size = len(tostring(root))/1024.
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ValueError.__init__(self,
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_('Could not find reasonable point at which to split: '
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'%(path)s Sub-tree size: %(size)d KB')%dict(
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path=path, size=size))
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class Split(object):
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def __init__(self, split_on_page_breaks=True, page_breaks_xpath=None,
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max_flow_size=0, remove_css_pagebreaks=True):
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self.split_on_page_breaks = split_on_page_breaks
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self.page_breaks_xpath = page_breaks_xpath
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self.max_flow_size = max_flow_size
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self.page_break_selectors = None
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self.remove_css_pagebreaks = remove_css_pagebreaks
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if self.page_breaks_xpath is not None:
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self.page_break_selectors = [(XPath(self.page_breaks_xpath), False)]
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def __call__(self, oeb, opts):
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self.oeb = oeb
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self.log = oeb.log
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self.log('Splitting markup on page breaks and flow limits, if any...')
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self.opts = opts
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self.map = {}
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for item in list(self.oeb.manifest.items):
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if item.spine_position is not None and etree.iselement(item.data):
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self.split_item(item)
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self.fix_links()
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def split_item(self, item):
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page_breaks, page_break_ids = [], []
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if self.split_on_page_breaks:
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page_breaks, page_break_ids = self.find_page_breaks(item)
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splitter = FlowSplitter(item, page_breaks, page_break_ids,
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self.max_flow_size, self.oeb, self.opts)
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if splitter.was_split:
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am = splitter.anchor_map
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self.map[item.href] = collections.defaultdict(
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am.default_factory, am)
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def find_page_breaks(self, item):
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if self.page_break_selectors is None:
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self.page_break_selectors = set()
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stylesheets = [x.data for x in self.oeb.manifest if x.media_type in
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OEB_STYLES]
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for rule in rules(stylesheets):
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before = force_unicode(getattr(rule.style.getPropertyCSSValue(
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'page-break-before'), 'cssText', '').strip().lower())
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after = force_unicode(getattr(rule.style.getPropertyCSSValue(
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'page-break-after'), 'cssText', '').strip().lower())
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try:
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if before and before not in {'avoid', 'auto', 'inherit'}:
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self.page_break_selectors.add((rule.selectorText, True))
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if self.remove_css_pagebreaks:
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rule.style.removeProperty('page-break-before')
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except:
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pass
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try:
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if after and after not in {'avoid', 'auto', 'inherit'}:
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self.page_break_selectors.add((rule.selectorText, False))
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if self.remove_css_pagebreaks:
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rule.style.removeProperty('page-break-after')
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except:
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pass
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page_breaks = set()
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select = Select(item.data)
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if not self.page_break_selectors:
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return [], []
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body = item.data.xpath('//h:body', namespaces=NAMESPACES)
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if not body:
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return [], []
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descendants = frozenset(body[0].iterdescendants('*'))
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for selector, before in self.page_break_selectors:
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try:
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for elem in select(selector):
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if elem in descendants and elem.tag.rpartition('}')[2].lower() not in {'html', 'body', 'head', 'style', 'script', 'meta', 'link'}:
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elem.set('pb_before', '1' if before else '0')
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page_breaks.add(elem)
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except SelectorError as err:
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self.log.warn('Ignoring page breaks specified with invalid CSS selector: %r (%s)' % (selector, as_unicode(err)))
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for i, elem in enumerate(item.data.iter('*')):
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try:
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elem.set('pb_order', str(i))
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except TypeError: # Cant set attributes on comment nodes etc.
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continue
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page_breaks = list(page_breaks)
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page_breaks.sort(key=lambda x:int(x.get('pb_order')))
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page_break_ids, page_breaks_ = [], []
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for i, x in enumerate(page_breaks):
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x.set('id', x.get('id', 'calibre_pb_%d'%i))
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id = x.get('id')
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try:
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xp = XPath('//*[@id="%s"]'%id)
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except:
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try:
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xp = XPath("//*[@id='%s']"%id)
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except:
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# The id has both a quote and an apostrophe or some other
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# Just replace it since I doubt its going to work anywhere else
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# either
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id = 'calibre_pb_%d'%i
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x.set('id', id)
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xp = XPath('//*[@id=%r]'%id)
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page_breaks_.append((xp, x.get('pb_before', '0') == '1'))
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page_break_ids.append(id)
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for elem in item.data.iter(etree.Element):
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elem.attrib.pop('pb_order', False)
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elem.attrib.pop('pb_before', False)
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return page_breaks_, page_break_ids
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def fix_links(self):
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'''
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Fix references to the split files in other content files.
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'''
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for item in self.oeb.manifest:
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if etree.iselement(item.data):
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self.current_item = item
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rewrite_links(item.data, self.rewrite_links)
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def rewrite_links(self, url):
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href, frag = urllib.parse.urldefrag(url)
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try:
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href = self.current_item.abshref(href)
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except ValueError:
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# Unparseable URL
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return url
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try:
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href = urlnormalize(href)
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except ValueError:
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# href has non utf-8 quoting
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return url
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if href in self.map:
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anchor_map = self.map[href]
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nhref = anchor_map[frag if frag else None]
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nhref = self.current_item.relhref(nhref)
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if frag:
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nhref = '#'.join((unquote(nhref), frag))
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return nhref
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return url
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class FlowSplitter(object):
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'The actual splitting logic'
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def __init__(self, item, page_breaks, page_break_ids, max_flow_size, oeb,
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opts):
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self.item = item
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self.oeb = oeb
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self.opts = opts
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self.log = oeb.log
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self.page_breaks = page_breaks
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self.page_break_ids = page_break_ids
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self.max_flow_size = max_flow_size
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self.base = item.href
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self.csp_counter = 0
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base, ext = os.path.splitext(self.base)
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self.base = base.replace('%', '%%')+'_split_%.3d'+ext
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self.trees = [self.item.data.getroottree()]
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self.splitting_on_page_breaks = True
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if self.page_breaks:
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self.split_on_page_breaks(self.trees[0])
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self.splitting_on_page_breaks = False
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if self.max_flow_size > 0:
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lt_found = False
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self.log('\tLooking for large trees in %s...'%item.href)
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trees = list(self.trees)
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self.tree_map = {}
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for i, tree in enumerate(trees):
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size = len(tostring(tree.getroot()))
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if size > self.max_flow_size:
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self.log('\tFound large tree #%d'%i)
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lt_found = True
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self.split_trees = []
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self.split_to_size(tree)
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self.tree_map[tree] = self.split_trees
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if not lt_found:
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self.log('\tNo large trees found')
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self.trees = []
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for x in trees:
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self.trees.extend(self.tree_map.get(x, [x]))
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self.was_split = len(self.trees) > 1
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if self.was_split:
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self.log('\tSplit into %d parts'%len(self.trees))
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self.commit()
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def split_on_page_breaks(self, orig_tree):
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ordered_ids = OrderedDict()
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all_page_break_ids = frozenset(self.page_break_ids)
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for elem_id in orig_tree.xpath('//*/@id'):
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if elem_id in all_page_break_ids:
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ordered_ids[elem_id] = self.page_breaks[
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self.page_break_ids.index(elem_id)]
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self.trees = [orig_tree]
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while ordered_ids:
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pb_id, (pattern, before) = next(iteritems(ordered_ids))
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del ordered_ids[pb_id]
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for i in range(len(self.trees)-1, -1, -1):
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tree = self.trees[i]
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elem = pattern(tree)
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if elem:
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self.log.debug('\t\tSplitting on page-break at id=%s'%
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elem[0].get('id'))
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before_tree, after_tree = self.do_split(tree, elem[0], before)
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self.trees[i:i+1] = [before_tree, after_tree]
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break
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trees, ids = [], set()
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for tree in self.trees:
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root = tree.getroot()
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if self.is_page_empty(root):
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discarded_ids = root.xpath('//*[@id]')
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for x in discarded_ids:
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x = x.get('id')
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if not x.startswith('calibre_'):
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ids.add(x)
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else:
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if ids:
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body = self.get_body(root)
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if body is not None:
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existing_ids = frozenset(body.xpath('//*/@id'))
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for x in ids - existing_ids:
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body.insert(0, body.makeelement(XHTML('div'), id=x, style='height:0pt'))
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ids = set()
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trees.append(tree)
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self.trees = trees
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def get_body(self, root):
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body = root.xpath('//h:body', namespaces=NAMESPACES)
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if not body:
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return None
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return body[0]
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def do_split(self, tree, split_point, before):
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'''
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Split ``tree`` into a *before* and *after* tree at ``split_point``.
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:param before: If True tree is split before split_point, otherwise after split_point
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:return: before_tree, after_tree
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'''
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return do_split(split_point, self.log, before=before)
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def is_page_empty(self, root):
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body = self.get_body(root)
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if body is None:
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return False
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txt = re.sub(r'\s+|\xa0', '',
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etree.tostring(body, method='text', encoding='unicode'))
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if len(txt) > 1:
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return False
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for img in root.xpath('//h:img', namespaces=NAMESPACES):
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if img.get('style', '') != 'display:none':
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return False
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if root.xpath('//*[local-name() = "svg"]'):
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return False
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return True
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def split_text(self, text, root, size):
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self.log.debug('\t\t\tSplitting text of length: %d'%len(text))
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rest = text.replace('\r', '')
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parts = re.split('\n\n', rest)
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self.log.debug('\t\t\t\tFound %d parts'%len(parts))
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if max(map(len, parts)) > size:
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raise SplitError('Cannot split as file contains a <pre> tag '
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'with a very large paragraph', root)
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ans = []
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buf = ''
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for part in parts:
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if len(buf) + len(part) < size:
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buf += '\n\n'+part
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else:
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ans.append(buf)
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buf = part
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return ans
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def split_to_size(self, tree):
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self.log.debug('\t\tSplitting...')
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root = tree.getroot()
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# Split large <pre> tags if they contain only text
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for pre in XPath('//h:pre')(root):
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if len(tuple(pre.iterchildren(etree.Element))) > 0:
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continue
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if pre.text and len(pre.text) > self.max_flow_size*0.5:
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self.log.debug('\t\tSplitting large <pre> tag')
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frags = self.split_text(pre.text, root, int(0.2*self.max_flow_size))
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new_pres = []
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for frag in frags:
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pre2 = copy.copy(pre)
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pre2.text = frag
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pre2.tail = ''
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new_pres.append(pre2)
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new_pres[-1].tail = pre.tail
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p = pre.getparent()
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i = p.index(pre)
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p[i:i+1] = new_pres
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split_point, before = self.find_split_point(root)
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if split_point is None:
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raise SplitError(self.item.href, root)
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self.log.debug('\t\t\tSplit point:', split_point.tag, tree.getpath(split_point))
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trees = self.do_split(tree, split_point, before)
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sizes = [len(tostring(t.getroot())) for t in trees]
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if min(sizes) < 5*1024:
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self.log.debug('\t\t\tSplit tree too small')
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self.split_to_size(tree)
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return
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for t, size in zip(trees, sizes):
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r = t.getroot()
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if self.is_page_empty(r):
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continue
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elif size <= self.max_flow_size:
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self.split_trees.append(t)
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self.log.debug(
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'\t\t\tCommitted sub-tree #%d (%d KB)'%(
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len(self.split_trees), size/1024.))
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else:
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self.log.debug(
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'\t\t\tSplit tree still too large: %d KB' % (size/1024.))
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self.split_to_size(t)
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def find_split_point(self, root):
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'''
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Find the tag at which to split the tree rooted at `root`.
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Search order is:
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* Heading tags
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* <div> tags
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* <pre> tags
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* <hr> tags
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* <p> tags
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* <br> tags
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* <li> tags
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We try to split in the "middle" of the file (as defined by tag counts.
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'''
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def pick_elem(elems):
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if elems:
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elems = [i for i in elems if i.get(SPLIT_POINT_ATTR, '0') !=
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'1']
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if elems:
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i = int(len(elems)//2)
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elems[i].set(SPLIT_POINT_ATTR, '1')
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return elems[i]
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for path in (
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'//*[re:match(name(), "h[1-6]", "i")]',
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'/h:html/h:body/h:div',
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'//h:pre',
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'//h:hr',
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'//h:p',
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'//h:div',
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'//h:br',
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'//h:li',
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):
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elems = root.xpath(path, namespaces=NAMESPACES)
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elem = pick_elem(elems)
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if elem is not None:
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try:
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XPath(elem.getroottree().getpath(elem))
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except:
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continue
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return elem, True
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return None, True
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def commit(self):
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'''
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Commit all changes caused by the split. Calculates an *anchor_map* for
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all anchors in the original tree. Internal links are re-directed. The
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original file is deleted and the split files are saved.
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'''
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if not self.was_split:
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return
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self.anchor_map = collections.defaultdict(lambda :self.base%0)
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self.files = []
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for i, tree in enumerate(self.trees):
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root = tree.getroot()
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self.files.append(self.base%i)
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for elem in root.xpath('//*[@id or @name]'):
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for anchor in elem.get('id', ''), elem.get('name', ''):
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if anchor != '' and anchor not in self.anchor_map:
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self.anchor_map[anchor] = self.files[-1]
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for elem in root.xpath('//*[@%s]'%SPLIT_POINT_ATTR):
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elem.attrib.pop(SPLIT_POINT_ATTR, '0')
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spine_pos = self.item.spine_position
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for current, tree in zip(*map(reversed, (self.files, self.trees))):
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for a in tree.getroot().xpath('//h:a[@href]', namespaces=NAMESPACES):
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href = a.get('href').strip()
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if href.startswith('#'):
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anchor = href[1:]
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file = self.anchor_map[anchor]
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file = self.item.relhref(file)
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if file != current:
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a.set('href', file+href)
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new_id = self.oeb.manifest.generate(id=self.item.id)[0]
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new_item = self.oeb.manifest.add(new_id, current,
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self.item.media_type, data=tree.getroot())
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self.oeb.spine.insert(spine_pos, new_item, self.item.linear)
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if self.oeb.guide:
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for ref in self.oeb.guide.values():
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href, frag = urllib.parse.urldefrag(ref.href)
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if href == self.item.href:
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nhref = self.anchor_map[frag if frag else None]
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if frag:
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nhref = '#'.join((nhref, frag))
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ref.href = nhref
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def fix_toc_entry(toc):
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if toc.href:
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href, frag = urllib.parse.urldefrag(toc.href)
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if href == self.item.href:
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nhref = self.anchor_map[frag if frag else None]
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if frag:
|
|
nhref = '#'.join((nhref, frag))
|
|
toc.href = nhref
|
|
for x in toc:
|
|
fix_toc_entry(x)
|
|
|
|
if self.oeb.toc:
|
|
fix_toc_entry(self.oeb.toc)
|
|
|
|
if self.oeb.pages:
|
|
for page in self.oeb.pages:
|
|
href, frag = urllib.parse.urldefrag(page.href)
|
|
if href == self.item.href:
|
|
nhref = self.anchor_map[frag if frag else None]
|
|
if frag:
|
|
nhref = '#'.join((nhref, frag))
|
|
page.href = nhref
|
|
|
|
self.oeb.manifest.remove(self.item)
|