Current File : //lib/calibre/calibre/ebooks/epub/cfi/parse.py
#!/usr/bin/env python3
__license__ = 'GPL v3'
__copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
import regex
class Parser:
''' See epubcfi.ebnf for the specification that this parser tries to
follow. I have implemented it manually, since I dont want to depend on
grako, and the grammar is pretty simple. This parser is thread-safe, i.e.
it can be used from multiple threads simultaneously. '''
def __init__(self):
# All allowed unicode characters + escaped special characters
special_char = r'[\[\](),;=^]'
unescaped_char = f'[[\t\n\r -\ud7ff\ue000-\ufffd\U00010000-\U0010ffff]--{special_char}]'
# calibre used to escape hyphens as well, so recognize them even though
# not strictly spec compliant
escaped_char = r'\^' + special_char[:-1] + '-]'
chars = fr'(?:{unescaped_char}|(?:{escaped_char}))+'
chars_no_space = chars.replace('0020', '0021')
# No leading zeros allowed for integers
integer = r'(?:[1-9][0-9]*)|0'
# No leading zeros, except for numbers in (0, 1) and no trailing zeros for the fractional part
frac = r'\.[0-9]*[1-9]'
number = r'(?:[1-9][0-9]*(?:{0})?)|(?:0{0})|(?:0)'.format(frac)
c = lambda x:regex.compile(x, flags=regex.VERSION1)
# A step of the form /integer
self.step_pat = c(r'/(%s)' % integer)
# An id assertion of the form [characters]
self.id_assertion_pat = c(r'\[(%s)\]' % chars)
# A text offset of the form :integer
self.text_offset_pat = c(r':(%s)' % integer)
# A temporal offset of the form ~number
self.temporal_offset_pat = c(r'~(%s)' % number)
# A spatial offset of the form @number:number
self.spatial_offset_pat = c(r'@({0}):({0})'.format(number))
# A spatio-temporal offset of the form ~number@number:number
self.st_offset_pat = c(r'~({0})@({0}):({0})'.format(number))
# Text assertion patterns
self.ta1_pat = c(r'({0})(?:,({0})){{0,1}}'.format(chars))
self.ta2_pat = c(r',(%s)' % chars)
self.parameters_pat = c(fr'(?:;({chars_no_space})=((?:{chars},?)+))+')
self.csv_pat = c(r'(?:(%s),?)+' % chars)
# Unescape characters
unescape_pat = c(fr'{escaped_char[:2]}({escaped_char[2:]})')
self.unescape = lambda x: unescape_pat.sub(r'\1', x)
def parse_epubcfi(self, raw):
' Parse a full epubcfi of the form epubcfi(path [ , path , path ]) '
null = {}, {}, {}, raw
if not raw:
return null
if not raw.startswith('epubcfi('):
return null
raw = raw[len('epubcfi('):]
parent_cfi, raw = self.parse_path(raw)
if not parent_cfi:
return null
start_cfi, end_cfi = {}, {}
if raw.startswith(','):
start_cfi, raw = self.parse_path(raw[1:])
if raw.startswith(','):
end_cfi, raw = self.parse_path(raw[1:])
if not start_cfi or not end_cfi:
return null
if raw.startswith(')'):
raw = raw[1:]
else:
return null
return parent_cfi, start_cfi, end_cfi, raw
def parse_path(self, raw):
' Parse the path component of an epubcfi of the form /step... '
path = {'steps':[]}
raw = self._parse_path(raw, path)
if not path['steps']:
path = {}
return path, raw
def do_match(self, pat, raw):
m = pat.match(raw)
if m is not None:
raw = raw[len(m.group()):]
return m, raw
def _parse_path(self, raw, ans):
m, raw = self.do_match(self.step_pat, raw)
if m is None:
return raw
ans['steps'].append({'num':int(m.group(1))})
m, raw = self.do_match(self.id_assertion_pat, raw)
if m is not None:
ans['steps'][-1]['id'] = self.unescape(m.group(1))
if raw.startswith('!'):
ans['redirect'] = r = {'steps':[]}
return self._parse_path(raw[1:], r)
else:
remaining_raw = self.parse_offset(raw, ans['steps'][-1])
return self._parse_path(raw, ans) if remaining_raw is None else remaining_raw
def parse_offset(self, raw, ans):
m, raw = self.do_match(self.text_offset_pat, raw)
if m is not None:
ans['text_offset'] = int(m.group(1))
return self.parse_text_assertion(raw, ans)
m, raw = self.do_match(self.st_offset_pat, raw)
if m is not None:
t, x, y = m.groups()
ans['temporal_offset'] = float(t)
ans['spatial_offset'] = tuple(map(float, (x, y)))
return raw
m, raw = self.do_match(self.temporal_offset_pat, raw)
if m is not None:
ans['temporal_offset'] = float(m.group(1))
return raw
m, raw = self.do_match(self.spatial_offset_pat, raw)
if m is not None:
ans['spatial_offset'] = tuple(map(float, m.groups()))
return raw
def parse_text_assertion(self, raw, ans):
oraw = raw
if not raw.startswith('['):
return oraw
raw = raw[1:]
ta = {}
m, raw = self.do_match(self.ta1_pat, raw)
if m is not None:
before, after = m.groups()
ta['before'] = self.unescape(before)
if after is not None:
ta['after'] = self.unescape(after)
else:
m, raw = self.do_match(self.ta2_pat, raw)
if m is not None:
ta['after'] = self.unescape(m.group(1))
# parse parameters
m, raw = self.do_match(self.parameters_pat, raw)
if m is not None:
params = {}
for name, value in zip(m.captures(1), m.captures(2)):
params[name] = tuple(map(self.unescape, self.csv_pat.match(value).captures(1)))
if params:
ta['params'] = params
if not raw.startswith(']'):
return oraw # no closing ] or extra content in the assertion
if ta:
ans['text_assertion'] = ta
return raw[1:]
_parser = None
def parser():
global _parser
if _parser is None:
_parser = Parser()
return _parser
def get_steps(pcfi):
ans = tuple(pcfi['steps'])
if 'redirect' in pcfi:
ans += get_steps(pcfi['redirect'])
return ans
def cfi_sort_key(cfi, only_path=True):
p = parser()
try:
if only_path:
pcfi = p.parse_path(cfi)[0]
else:
parent, start = p.parse_epubcfi(cfi)[:2]
pcfi = start or parent
except Exception:
import traceback
traceback.print_exc()
return (), (0, (0, 0), 0)
if not pcfi:
import sys
print('Failed to parse CFI: %r' % cfi, file=sys.stderr)
return (), (0, (0, 0), 0)
steps = get_steps(pcfi)
step_nums = tuple(s.get('num', 0) for s in steps)
step = steps[-1] if steps else {}
offsets = (step.get('temporal_offset', 0), tuple(reversed(step.get('spatial_offset', (0, 0)))), step.get('text_offset', 0), )
return step_nums, offsets
def decode_cfi(root, cfi):
from lxml.etree import XPathEvalError
p = parser()
try:
pcfi = p.parse_path(cfi)[0]
except Exception:
import traceback
traceback.print_exc()
return
if not pcfi:
import sys
print('Failed to parse CFI: %r' % pcfi, file=sys.stderr)
return
steps = get_steps(pcfi)
ans = root
for step in steps:
num = step.get('num', 0)
node_id = step.get('id')
try:
match = ans.xpath('descendant::*[@id="%s"]' % node_id)
except XPathEvalError:
match = ()
if match:
ans = match[0]
continue
index = 0
for child in ans.iterchildren('*'):
index |= 1 # increment index by 1 if it is even
index += 1
if index == num:
ans = child
break
else:
return
return ans
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