305 lines
10 KiB
Python
305 lines
10 KiB
Python
# coding: utf-8
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"""
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weasyprint.utils
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----------------
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Various utility functions and classes.
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:copyright: Copyright 2011-2014 Simon Sapin and contributors, see AUTHORS.
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:license: BSD, see LICENSE for details.
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"""
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from __future__ import division, unicode_literals
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import contextlib
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import gzip
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import io
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import mimetypes
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import os.path
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import re
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import sys
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import traceback
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import zlib
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from . import VERSION_STRING
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from .compat import (
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FILESYSTEM_ENCODING, Request, StreamingGzipFile, base64_decode,
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parse_email, pathname2url, quote, unicode, unquote, unquote_to_bytes,
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urljoin, urllib_get_charset, urllib_get_content_type, urllib_get_filename,
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urlopen, urlsplit)
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from .logger import LOGGER
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# Unlinke HTML, CSS and PNG, the SVG MIME type is not always builtin
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# in some Python version and therefore not reliable.
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if sys.version_info[0] >= 3:
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mimetypes.add_type('image/svg+xml', '.svg')
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else:
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# Native strings required.
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mimetypes.add_type(b'image/svg+xml', b'.svg')
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# See http://stackoverflow.com/a/11687993/1162888
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# Both are needed in Python 3 as the re module does not like to mix
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# http://tools.ietf.org/html/rfc3986#section-3.1
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UNICODE_SCHEME_RE = re.compile('^([a-zA-Z][a-zA-Z0-9.+-]+):')
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BYTES_SCHEME_RE = re.compile(b'^([a-zA-Z][a-zA-Z0-9.+-]+):')
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def iri_to_uri(url):
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"""Turn an IRI that can contain any Unicode character into an ASCII-only
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URI that conforms to RFC 3986.
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"""
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if url.startswith('data:'):
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# Data URIs can be huge, but don’t need this anyway.
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return url
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# Use UTF-8 as per RFC 3987 (IRI), except for file://
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url = url.encode(FILESYSTEM_ENCODING
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if url.startswith('file:') else 'utf-8')
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# This is a full URI, not just a component. Only %-encode characters
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# that are not allowed at all in URIs. Everthing else is "safe":
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# * Reserved characters: /:?#[]@!$&'()*+,;=
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# * Unreserved characters: ASCII letters, digits and -._~
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# Of these, only '~' is not in urllib’s "always safe" list.
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# * '%' to avoid double-encoding
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return quote(url, safe=b"/:?#[]@!$&'()*+,;=~%")
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def path2url(path):
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"""Return file URL of `path`"""
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path = os.path.abspath(path)
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if os.path.isdir(path):
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# Make sure directory names have a trailing slash.
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# Otherwise relative URIs are resolved from the parent directory.
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path += os.path.sep
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path = pathname2url(path)
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if path.startswith('///'):
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# On Windows pathname2url(r'C:\foo') is apparently '///C:/foo'
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# That enough slashes already.
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return 'file:' + path
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else:
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return 'file://' + path
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def url_is_absolute(url):
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return bool(
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(UNICODE_SCHEME_RE if isinstance(url, unicode) else BYTES_SCHEME_RE)
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.match(url))
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def get_url_attribute(element, attr_name, base_url, allow_relative=False):
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"""Get the URI corresponding to the ``attr_name`` attribute.
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Return ``None`` if:
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* the attribute is empty or missing or,
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* the value is a relative URI but the document has no base URI and
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``allow_relative`` is ``False``.
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Otherwise return an URI, absolute if possible.
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"""
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value = element.get(attr_name, '').strip()
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if value:
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return url_join(
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base_url or '', value, allow_relative, '<%s %s="%s">',
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(element.tag, attr_name, value))
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def url_join(base_url, url, allow_relative, context, context_args):
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"""Like urllib.urljoin, but warn if base_url is required but missing."""
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if url_is_absolute(url):
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return iri_to_uri(url)
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elif base_url:
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return iri_to_uri(urljoin(base_url, url))
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elif allow_relative:
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return iri_to_uri(url)
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else:
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LOGGER.error('Relative URI reference without a base URI: ' + context,
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*context_args)
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return None
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def get_link_attribute(element, attr_name, base_url):
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"""Return ('external', absolute_uri) or
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('internal', unquoted_fragment_id) or None.
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"""
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attr_value = element.get(attr_name, '').strip()
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if attr_value.startswith('#') and len(attr_value) > 1:
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# Do not require a base_url when the value is just a fragment.
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return 'internal', unquote(attr_value[1:])
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uri = get_url_attribute(element, attr_name, base_url, allow_relative=True)
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if uri:
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if base_url:
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parsed = urlsplit(uri)
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# Compare with fragments removed
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if parsed[:-1] == urlsplit(base_url)[:-1]:
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return 'internal', unquote(parsed.fragment)
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return 'external', uri
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def ensure_url(string):
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"""Get a ``scheme://path`` URL from ``string``.
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If ``string`` looks like an URL, return it unchanged. Otherwise assume a
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filename and convert it to a ``file://`` URL.
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"""
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return string if url_is_absolute(string) else path2url(string)
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def safe_base64_decode(data):
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"""Decode base64, padding being optional.
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"From a theoretical point of view, the padding character is not needed,
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since the number of missing bytes can be calculated from the number
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of Base64 digits."
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https://en.wikipedia.org/wiki/Base64#Padding
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:param data: Base64 data as an ASCII byte string
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:returns: The decoded byte string.
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"""
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missing_padding = 4 - len(data) % 4
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if missing_padding:
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data += b'=' * missing_padding
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return base64_decode(data)
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def open_data_url(url):
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"""Decode URLs with the 'data' scheme. urllib can handle them
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in Python 2, but that is broken in Python 3.
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Inspired from Python 2.7.2’s urllib.py.
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"""
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# syntax of data URLs:
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# dataurl := "data:" [ mediatype ] [ ";base64" ] "," data
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# mediatype := [ type "/" subtype ] *( ";" parameter )
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# data := *urlchar
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# parameter := attribute "=" value
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try:
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header, data = url.split(',', 1)
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except ValueError:
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raise IOError('bad data URL')
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header = header[5:] # len('data:') == 5
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if header:
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semi = header.rfind(';')
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if semi >= 0 and '=' not in header[semi:]:
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content_type = header[:semi]
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encoding = header[semi + 1:]
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else:
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content_type = header
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encoding = ''
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message = parse_email('Content-type: ' + content_type)
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mime_type = message.get_content_type()
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charset = message.get_content_charset()
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else:
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mime_type = 'text/plain'
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charset = 'US-ASCII'
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encoding = ''
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data = unquote_to_bytes(data)
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if encoding == 'base64':
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data = safe_base64_decode(data)
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return dict(string=data, mime_type=mime_type, encoding=charset,
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redirected_url=url)
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HTTP_HEADERS = {
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'User-Agent': VERSION_STRING,
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'Accept-Encoding': 'gzip, deflate',
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}
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def default_url_fetcher(url):
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"""Fetch an external resource such as an image or stylesheet.
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Another callable with the same signature can be given as the
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:obj:`url_fetcher` argument to :class:`HTML` or :class:`CSS`.
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(See :ref:`url-fetchers`.)
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:type url: Unicode string
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:param url: The URL of the resource to fetch.
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:raises: An exception indicating failure, e.g. ``ValueError`` on
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syntactically invalid URL.
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:returns: A dict with the following keys:
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* One of ``string`` (a byte string) or ``file_obj``
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(a file-like object)
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* Optionally: ``mime_type``, a MIME type extracted e.g. from a
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*Content-Type* header. If not provided, the type is guessed from the
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file extension in the URL.
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* Optionally: ``encoding``, a character encoding extracted e.g. from a
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*charset* parameter in a *Content-Type* header
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* Optionally: ``redirected_url``, the actual URL of the resource
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if there were e.g. HTTP redirects.
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* Optionally: ``filename``, the filename of the resource. Usually
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derived from the *filename* parameter in a *Content-Disposition*
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header
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If a ``file_obj`` key is given, it is the caller’s responsibility
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to call ``file_obj.close()``.
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"""
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if url.lower().startswith('data:'):
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return open_data_url(url)
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elif UNICODE_SCHEME_RE.match(url):
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url = iri_to_uri(url)
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response = urlopen(Request(url, headers=HTTP_HEADERS))
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result = dict(redirected_url=response.geturl(),
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mime_type=urllib_get_content_type(response),
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encoding=urllib_get_charset(response),
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filename=urllib_get_filename(response))
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content_encoding = response.info().get('Content-Encoding')
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if content_encoding == 'gzip':
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if StreamingGzipFile is None:
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result['string'] = gzip.GzipFile(
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fileobj=io.BytesIO(response.read())).read()
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response.close()
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else:
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result['file_obj'] = StreamingGzipFile(fileobj=response)
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elif content_encoding == 'deflate':
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data = response.read()
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try:
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result['string'] = zlib.decompress(data)
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except zlib.error:
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# Try without zlib header or checksum
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result['string'] = zlib.decompress(data, -15)
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else:
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result['file_obj'] = response
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return result
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else:
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raise ValueError('Not an absolute URI: %r' % url)
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class URLFetchingError(IOError):
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"""Some error happened when fetching an URL."""
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@contextlib.contextmanager
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def fetch(url_fetcher, url):
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"""Call an url_fetcher, fill in optional data, and clean up."""
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try:
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result = url_fetcher(url)
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except Exception as exc:
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raise URLFetchingError('%s: %s' % (type(exc).__name__, str(exc)))
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result.setdefault('redirected_url', url)
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result.setdefault('mime_type', None)
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if 'file_obj' in result:
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try:
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yield result
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finally:
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try:
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result['file_obj'].close()
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except Exception:
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# May already be closed or something.
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# This is just cleanup anyway: log but make it non-fatal.
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LOGGER.warning('Error when closing stream for %s:\n%s',
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url, traceback.format_exc())
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else:
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yield result
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