[downloader/hls] Assemble single-file WebVTT subtitles from HLS segments
This commit is contained in:
Felix S
parent
5fbcebed8c
commit
4a2f19abbd
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@ -3018,10 +3018,24 @@ else:
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return ctypes.WINFUNCTYPE(*args, **kwargs)
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try:
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compat_Pattern = re.Pattern
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except AttributeError:
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compat_Pattern = type(re.compile(''))
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try:
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compat_Match = re.Match
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except AttributeError:
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compat_Match = type(re.compile('').match(''))
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__all__ = [
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'compat_HTMLParseError',
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'compat_HTMLParser',
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'compat_HTTPError',
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'compat_Match',
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'compat_Pattern',
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'compat_Struct',
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'compat_b64decode',
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'compat_basestring',
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@ -2,6 +2,7 @@ from __future__ import unicode_literals
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import errno
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import re
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import io
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import binascii
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try:
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from Crypto.Cipher import AES
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@ -27,7 +28,9 @@ from ..utils import (
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parse_m3u8_attributes,
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sanitize_open,
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update_url_query,
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bug_reports_message,
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)
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from .. import webvtt
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class HlsFD(FragmentFD):
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@ -78,6 +81,8 @@ class HlsFD(FragmentFD):
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man_url = info_dict['url']
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self.to_screen('[%s] Downloading m3u8 manifest' % self.FD_NAME)
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is_webvtt = info_dict['ext'] == 'vtt'
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urlh = self.ydl.urlopen(self._prepare_url(info_dict, man_url))
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man_url = urlh.geturl()
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s = urlh.read().decode('utf-8', 'ignore')
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@ -142,6 +147,8 @@ class HlsFD(FragmentFD):
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else:
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self._prepare_and_start_frag_download(ctx)
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extra_state = ctx.setdefault('extra_state', {})
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fragment_retries = self.params.get('fragment_retries', 0)
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skip_unavailable_fragments = self.params.get('skip_unavailable_fragments', True)
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test = self.params.get('test', False)
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@ -308,6 +315,42 @@ class HlsFD(FragmentFD):
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return frag_content, frag_index
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pack_fragment = lambda frag_content, _: frag_content
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if is_webvtt:
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def pack_fragment(frag_content, frag_index):
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output = io.StringIO()
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adjust = 0
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for block in webvtt.parse_fragment(frag_content):
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if isinstance(block, webvtt.CueBlock):
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block.start += adjust
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block.end += adjust
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elif isinstance(block, webvtt.Magic):
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# XXX: we do not handle MPEGTS overflow
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if frag_index == 1:
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extra_state['webvtt_mpegts'] = block.mpegts or 0
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extra_state['webvtt_local'] = block.local or 0
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# XXX: block.local = block.mpegts = None ?
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else:
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if block.mpegts is not None and block.local is not None:
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adjust = (
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(block.mpegts - extra_state.get('webvtt_mpegts', 0))
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- (block.local - extra_state.get('webvtt_local', 0))
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)
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continue
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elif isinstance(block, webvtt.HeaderBlock):
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if frag_index != 1:
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# XXX: this should probably be silent as well
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# or verify that all segments contain the same data
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self.report_warning(bug_reports_message(
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'Discarding a %s block found in the middle of the stream; '
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'if the subtitles display incorrectly,'
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% (type(block).__name__)))
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continue
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block.write_into(output)
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return output.getvalue().encode('utf-8')
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def append_fragment(frag_content, frag_index):
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if frag_content:
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fragment_filename = '%s-Frag%d' % (ctx['tmpfilename'], frag_index)
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@ -315,6 +358,7 @@ class HlsFD(FragmentFD):
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file, frag_sanitized = sanitize_open(fragment_filename, 'rb')
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ctx['fragment_filename_sanitized'] = frag_sanitized
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file.close()
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frag_content = pack_fragment(frag_content, frag_index)
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self._append_fragment(ctx, frag_content)
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return True
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except EnvironmentError as ose:
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@ -2035,6 +2035,12 @@ class InfoExtractor(object):
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'url': url,
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'ext': determine_ext(url),
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}
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if sub_info['ext'] == 'm3u8':
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# Per RFC 8216 §3.1, the only possible subtitle format m3u8
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# files may contain is WebVTT:
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# <https://tools.ietf.org/html/rfc8216#section-3.1>
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sub_info['ext'] = 'vtt'
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sub_info['protocol'] = 'm3u8_native'
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subtitles.setdefault(lang, []).append(sub_info)
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if media_type not in ('VIDEO', 'AUDIO'):
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return
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@ -0,0 +1,368 @@
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# coding: utf-8
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from __future__ import unicode_literals, print_function, division
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"""
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A partial parser for WebVTT segments. Interprets enough of the WebVTT stream
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to be able to assemble a single stand-alone subtitle file, suitably adjusting
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timestamps on the way, while everything else is passed through unmodified.
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Regular expressions based on the W3C WebVTT specification
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<https://www.w3.org/TR/webvtt1/>. The X-TIMESTAMP-MAP extension is described
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in RFC 8216 §3.5 <https://tools.ietf.org/html/rfc8216#section-3.5>.
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"""
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import re
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import io
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from .utils import int_or_none
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from .compat import (
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compat_str as str,
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compat_Pattern,
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compat_Match,
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)
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class _MatchParser(object):
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"""
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An object that maintains the current parsing position and allows
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conveniently advancing it as syntax elements are successfully parsed.
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"""
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def __init__(self, string):
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self._data = string
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self._pos = 0
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def match(self, r):
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if isinstance(r, compat_Pattern):
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return r.match(self._data, self._pos)
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if isinstance(r, str):
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if self._data.startswith(r, self._pos):
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return len(r)
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return None
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raise ValueError(r)
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def advance(self, by):
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if by is None:
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amt = 0
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elif isinstance(by, compat_Match):
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amt = len(by.group(0))
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elif isinstance(by, str):
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amt = len(by)
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elif isinstance(by, int):
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amt = by
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else:
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raise ValueError(by)
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self._pos += amt
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return by
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def consume(self, r):
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return self.advance(self.match(r))
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def child(self):
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return _MatchChildParser(self)
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class _MatchChildParser(_MatchParser):
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"""
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A child parser state, which advances through the same data as
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its parent, but has an independent position. This is useful when
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advancing through syntax elements we might later want to backtrack
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from.
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"""
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def __init__(self, parent):
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super(_MatchChildParser, self).__init__(parent._data)
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self.__parent = parent
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self._pos = parent._pos
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def commit(self):
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"""
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Advance the parent state to the current position of this child state.
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"""
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self.__parent._pos = self._pos
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return self.__parent
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class ParseError(Exception):
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def __init__(self, parser):
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super(ParseError, self).__init__("Parse error at position %u (near %r)" % (
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parser._pos, parser._data[parser._pos:parser._pos + 20]
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))
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_REGEX_TS = re.compile(r'''(?x)
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(?:([0-9]{2,}):)?
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([0-9]{2}):
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([0-9]{2})\.
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([0-9]{3})?
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''')
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_REGEX_EOF = re.compile(r'\Z')
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_REGEX_NL = re.compile(r'(?:\r\n|[\r\n])')
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_REGEX_BLANK = re.compile(r'(?:\r\n|[\r\n])+')
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def _parse_ts(ts):
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"""
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Convert a parsed WebVTT timestamp (a re.Match obtained from _REGEX_TS)
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into an MPEG PES timestamp: a tick counter at 90 kHz resolution.
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"""
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h, min, s, ms = ts.groups()
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return 90 * (
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int(h or 0) * 3600000 + # noqa: W504,E221,E222
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int(min) * 60000 + # noqa: W504,E221,E222
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int(s) * 1000 + # noqa: W504,E221,E222
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int(ms) # noqa: W504,E221,E222
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)
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def _format_ts(ts):
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"""
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Convert an MPEG PES timestamp into a WebVTT timestamp.
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This will lose sub-millisecond precision.
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"""
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ts = int((ts + 45) // 90)
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ms , ts = divmod(ts, 1000) # noqa: W504,E221,E222,E203
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s , ts = divmod(ts, 60) # noqa: W504,E221,E222,E203
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min, h = divmod(ts, 60) # noqa: W504,E221,E222
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return '%02u:%02u:%02u.%03u' % (h, min, s, ms)
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class Block(object):
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"""
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An abstract WebVTT block.
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"""
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def __init__(self, **kwargs):
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for key, val in kwargs.items():
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setattr(self, key, val)
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@classmethod
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def parse(cls, parser):
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m = parser.match(cls._REGEX)
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if not m:
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return None
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parser.advance(m)
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return cls(raw=m.group(0))
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def write_into(self, stream):
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stream.write(self.raw)
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class HeaderBlock(Block):
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"""
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A WebVTT block that may only appear in the header part of the file,
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i.e. before any cue blocks.
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"""
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pass
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class Magic(HeaderBlock):
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_REGEX = re.compile(r'\ufeff?WEBVTT([ \t][^\r\n]*)?(?:\r\n|[\r\n])')
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# XXX: The X-TIMESTAMP-MAP extension is described in RFC 8216 §3.5
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# <https://tools.ietf.org/html/rfc8216#section-3.5>, but the RFC
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# doesn’t specify the exact grammar nor where in the WebVTT
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# syntax it should be placed; the below has been devised based
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# on usage in the wild
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#
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# And strictly speaking, the presence of this extension violates
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# the W3C WebVTT spec. Oh well.
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_REGEX_TSMAP = re.compile(r'X-TIMESTAMP-MAP=')
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_REGEX_TSMAP_LOCAL = re.compile(r'LOCAL:')
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_REGEX_TSMAP_MPEGTS = re.compile(r'MPEGTS:([0-9]+)')
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@classmethod
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def __parse_tsmap(cls, parser):
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parser = parser.child()
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while True:
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m = parser.consume(cls._REGEX_TSMAP_LOCAL)
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if m:
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m = parser.consume(_REGEX_TS)
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if m is None:
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raise ParseError(parser)
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local = _parse_ts(m)
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if local is None:
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raise ParseError(parser)
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else:
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m = parser.consume(cls._REGEX_TSMAP_MPEGTS)
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if m:
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mpegts = int_or_none(m.group(1))
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if mpegts is None:
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raise ParseError(parser)
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else:
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raise ParseError(parser)
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if parser.consume(','):
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continue
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if parser.consume(_REGEX_NL):
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break
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raise ParseError(parser)
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parser.commit()
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return local, mpegts
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@classmethod
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def parse(cls, parser):
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parser = parser.child()
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m = parser.consume(cls._REGEX)
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if not m:
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raise ParseError(parser)
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extra = m.group(1)
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local, mpegts = None, None
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if parser.consume(cls._REGEX_TSMAP):
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local, mpegts = cls.__parse_tsmap(parser)
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if not parser.consume(_REGEX_NL):
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raise ParseError(parser)
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parser.commit()
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return cls(extra=extra, mpegts=mpegts, local=local)
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def write_into(self, stream):
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stream.write('WEBVTT')
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if self.extra is not None:
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stream.write(self.extra)
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stream.write('\n')
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if self.local or self.mpegts:
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stream.write('X-TIMESTAMP-MAP=LOCAL:')
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stream.write(_format_ts(self.local if self.local is not None else 0))
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stream.write(',MPEGTS:')
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stream.write(str(self.mpegts if self.mpegts is not None else 0))
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stream.write('\n')
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stream.write('\n')
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class StyleBlock(HeaderBlock):
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_REGEX = re.compile(r'''(?x)
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STYLE[\ \t]*(?:\r\n|[\r\n])
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((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
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(?:\r\n|[\r\n])
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''')
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class RegionBlock(HeaderBlock):
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_REGEX = re.compile(r'''(?x)
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REGION[\ \t]*
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((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
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(?:\r\n|[\r\n])
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''')
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class CommentBlock(Block):
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_REGEX = re.compile(r'''(?x)
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NOTE(?:\r\n|[\ \t\r\n])
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((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
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(?:\r\n|[\r\n])
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''')
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class CueBlock(Block):
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"""
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A cue block. The payload is not interpreted.
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"""
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_REGEX_ID = re.compile(r'((?:(?!-->)[^\r\n])+)(?:\r\n|[\r\n])')
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_REGEX_ARROW = re.compile(r'[ \t]+-->[ \t]+')
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_REGEX_SETTINGS = re.compile(r'[ \t]+((?:(?!-->)[^\r\n])+)')
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_REGEX_PAYLOAD = re.compile(r'[^\r\n]+(?:\r\n|[\r\n])?')
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@classmethod
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def parse(cls, parser):
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parser = parser.child()
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id = None
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m = parser.consume(cls._REGEX_ID)
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if m:
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id = m.group(1)
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m0 = parser.consume(_REGEX_TS)
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if not m0:
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return None
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if not parser.consume(cls._REGEX_ARROW):
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return None
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m1 = parser.consume(_REGEX_TS)
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if not m1:
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return None
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m2 = parser.consume(cls._REGEX_SETTINGS)
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if not parser.consume(_REGEX_NL):
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return None
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start = _parse_ts(m0)
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end = _parse_ts(m1)
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settings = m2.group(1) if m2 is not None else None
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text = io.StringIO()
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while True:
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m = parser.consume(cls._REGEX_PAYLOAD)
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if not m:
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break
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text.write(m.group(0))
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parser.commit()
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return cls(
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id=id,
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start=start, end=end, settings=settings,
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text=text.getvalue()
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)
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def write_into(self, stream):
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if self.id is not None:
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stream.write(self.id)
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stream.write('\n')
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stream.write(_format_ts(self.start))
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stream.write(' --> ')
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stream.write(_format_ts(self.end))
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if self.settings is not None:
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stream.write(' ')
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stream.write(self.settings)
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stream.write('\n')
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stream.write(self.text)
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stream.write('\n')
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def parse_fragment(frag_content):
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"""
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A generator that yields (partially) parsed WebVTT blocks when given
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a bytes object containing the raw contents of a WebVTT file.
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"""
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parser = _MatchParser(frag_content.decode('utf-8'))
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yield Magic.parse(parser)
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while not parser.match(_REGEX_EOF):
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if parser.consume(_REGEX_BLANK):
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continue
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block = RegionBlock.parse(parser)
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if block:
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yield block
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continue
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block = StyleBlock.parse(parser)
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if block:
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yield block
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continue
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block = CommentBlock.parse(parser)
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if block:
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yield block # XXX: or skip
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continue
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break
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while not parser.match(_REGEX_EOF):
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if parser.consume(_REGEX_BLANK):
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continue
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block = CommentBlock.parse(parser)
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if block:
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yield block # XXX: or skip
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continue
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block = CueBlock.parse(parser)
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||||
if block:
|
||||
yield block
|
||||
continue
|
||||
|
||||
raise ParseError(parser)
|
||||
Loading…
Reference in New Issue