Convert watch page to flask framework

1 files changed, 1303 insertions, 0 deletions

diff --git a/python/werkzeug/http.py b/python/werkzeug/http.py
new file mode 100644
index 0000000..af32007
--- /dev/null
+++ b/python/werkzeug/http.py
@@ -0,0 +1,1303 @@
+# -*- coding: utf-8 -*-
+"""
+    werkzeug.http
+    ~~~~~~~~~~~~~
+
+    Werkzeug comes with a bunch of utilities that help Werkzeug to deal with
+    HTTP data.  Most of the classes and functions provided by this module are
+    used by the wrappers, but they are useful on their own, too, especially if
+    the response and request objects are not used.
+
+    This covers some of the more HTTP centric features of WSGI, some other
+    utilities such as cookie handling are documented in the `werkzeug.utils`
+    module.
+
+
+    :copyright: 2007 Pallets
+    :license: BSD-3-Clause
+"""
+import base64
+import re
+import warnings
+from datetime import datetime
+from datetime import timedelta
+from hashlib import md5
+from time import gmtime
+from time import time
+
+from ._compat import integer_types
+from ._compat import iteritems
+from ._compat import PY2
+from ._compat import string_types
+from ._compat import text_type
+from ._compat import to_bytes
+from ._compat import to_unicode
+from ._compat import try_coerce_native
+from ._internal import _cookie_parse_impl
+from ._internal import _cookie_quote
+from ._internal import _make_cookie_domain
+
+try:
+    from email.utils import parsedate_tz
+except ImportError:
+    from email.Utils import parsedate_tz
+
+try:
+    from urllib.request import parse_http_list as _parse_list_header
+    from urllib.parse import unquote_to_bytes as _unquote
+except ImportError:
+    from urllib2 import parse_http_list as _parse_list_header
+    from urllib2 import unquote as _unquote
+
+_cookie_charset = "latin1"
+_basic_auth_charset = "utf-8"
+# for explanation of "media-range", etc. see Sections 5.3.{1,2} of RFC 7231
+_accept_re = re.compile(
+    r"""
+    (                       # media-range capturing-parenthesis
+      [^\s;,]+              # type/subtype
+      (?:[ \t]*;[ \t]*      # ";"
+        (?:                 # parameter non-capturing-parenthesis
+          [^\s;,q][^\s;,]*  # token that doesn't start with "q"
+        |                   # or
+          q[^\s;,=][^\s;,]* # token that is more than just "q"
+        )
+      )*                    # zero or more parameters
+    )                       # end of media-range
+    (?:[ \t]*;[ \t]*q=      # weight is a "q" parameter
+      (\d*(?:\.\d+)?)       # qvalue capturing-parentheses
+      [^,]*                 # "extension" accept params: who cares?
+    )?                      # accept params are optional
+    """,
+    re.VERBOSE,
+)
+_token_chars = frozenset(
+    "!#$%&'*+-.0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ^_`abcdefghijklmnopqrstuvwxyz|~"
+)
+_etag_re = re.compile(r'([Ww]/)?(?:"(.*?)"|(.*?))(?:\s*,\s*|$)')
+_unsafe_header_chars = set('()<>@,;:"/[]?={} \t')
+_option_header_piece_re = re.compile(
+    r"""
+    ;\s*,?\s*  # newlines were replaced with commas
+    (?P<key>
+        "[^"\\]*(?:\\.[^"\\]*)*"  # quoted string
+    |
+        [^\s;,=*]+  # token
+    )
+    (?:\*(?P<count>\d+))?  # *1, optional continuation index
+    \s*
+    (?:  # optionally followed by =value
+        (?:  # equals sign, possibly with encoding
+            \*\s*=\s*  # * indicates extended notation
+            (?:  # optional encoding
+                (?P<encoding>[^\s]+?)
+                '(?P<language>[^\s]*?)'
+            )?
+        |
+            =\s*  # basic notation
+        )
+        (?P<value>
+            "[^"\\]*(?:\\.[^"\\]*)*"  # quoted string
+        |
+            [^;,]+  # token
+        )?
+    )?
+    \s*
+    """,
+    flags=re.VERBOSE,
+)
+_option_header_start_mime_type = re.compile(r",\s*([^;,\s]+)([;,]\s*.+)?")
+
+_entity_headers = frozenset(
+    [
+        "allow",
+        "content-encoding",
+        "content-language",
+        "content-length",
+        "content-location",
+        "content-md5",
+        "content-range",
+        "content-type",
+        "expires",
+        "last-modified",
+    ]
+)
+_hop_by_hop_headers = frozenset(
+    [
+        "connection",
+        "keep-alive",
+        "proxy-authenticate",
+        "proxy-authorization",
+        "te",
+        "trailer",
+        "transfer-encoding",
+        "upgrade",
+    ]
+)
+
+
+HTTP_STATUS_CODES = {
+    100: "Continue",
+    101: "Switching Protocols",
+    102: "Processing",
+    200: "OK",
+    201: "Created",
+    202: "Accepted",
+    203: "Non Authoritative Information",
+    204: "No Content",
+    205: "Reset Content",
+    206: "Partial Content",
+    207: "Multi Status",
+    226: "IM Used",  # see RFC 3229
+    300: "Multiple Choices",
+    301: "Moved Permanently",
+    302: "Found",
+    303: "See Other",
+    304: "Not Modified",
+    305: "Use Proxy",
+    307: "Temporary Redirect",
+    308: "Permanent Redirect",
+    400: "Bad Request",
+    401: "Unauthorized",
+    402: "Payment Required",  # unused
+    403: "Forbidden",
+    404: "Not Found",
+    405: "Method Not Allowed",
+    406: "Not Acceptable",
+    407: "Proxy Authentication Required",
+    408: "Request Timeout",
+    409: "Conflict",
+    410: "Gone",
+    411: "Length Required",
+    412: "Precondition Failed",
+    413: "Request Entity Too Large",
+    414: "Request URI Too Long",
+    415: "Unsupported Media Type",
+    416: "Requested Range Not Satisfiable",
+    417: "Expectation Failed",
+    418: "I'm a teapot",  # see RFC 2324
+    421: "Misdirected Request",  # see RFC 7540
+    422: "Unprocessable Entity",
+    423: "Locked",
+    424: "Failed Dependency",
+    426: "Upgrade Required",
+    428: "Precondition Required",  # see RFC 6585
+    429: "Too Many Requests",
+    431: "Request Header Fields Too Large",
+    449: "Retry With",  # proprietary MS extension
+    451: "Unavailable For Legal Reasons",
+    500: "Internal Server Error",
+    501: "Not Implemented",
+    502: "Bad Gateway",
+    503: "Service Unavailable",
+    504: "Gateway Timeout",
+    505: "HTTP Version Not Supported",
+    507: "Insufficient Storage",
+    510: "Not Extended",
+}
+
+
+def wsgi_to_bytes(data):
+    """coerce wsgi unicode represented bytes to real ones"""
+    if isinstance(data, bytes):
+        return data
+    return data.encode("latin1")  # XXX: utf8 fallback?
+
+
+def bytes_to_wsgi(data):
+    assert isinstance(data, bytes), "data must be bytes"
+    if isinstance(data, str):
+        return data
+    else:
+        return data.decode("latin1")
+
+
+def quote_header_value(value, extra_chars="", allow_token=True):
+    """Quote a header value if necessary.
+
+    .. versionadded:: 0.5
+
+    :param value: the value to quote.
+    :param extra_chars: a list of extra characters to skip quoting.
+    :param allow_token: if this is enabled token values are returned
+                        unchanged.
+    """
+    if isinstance(value, bytes):
+        value = bytes_to_wsgi(value)
+    value = str(value)
+    if allow_token:
+        token_chars = _token_chars | set(extra_chars)
+        if set(value).issubset(token_chars):
+            return value
+    return '"%s"' % value.replace("\\", "\\\\").replace('"', '\\"')
+
+
+def unquote_header_value(value, is_filename=False):
+    r"""Unquotes a header value.  (Reversal of :func:`quote_header_value`).
+    This does not use the real unquoting but what browsers are actually
+    using for quoting.
+
+    .. versionadded:: 0.5
+
+    :param value: the header value to unquote.
+    """
+    if value and value[0] == value[-1] == '"':
+        # this is not the real unquoting, but fixing this so that the
+        # RFC is met will result in bugs with internet explorer and
+        # probably some other browsers as well.  IE for example is
+        # uploading files with "C:\foo\bar.txt" as filename
+        value = value[1:-1]
+
+        # if this is a filename and the starting characters look like
+        # a UNC path, then just return the value without quotes.  Using the
+        # replace sequence below on a UNC path has the effect of turning
+        # the leading double slash into a single slash and then
+        # _fix_ie_filename() doesn't work correctly.  See #458.
+        if not is_filename or value[:2] != "\\\\":
+            return value.replace("\\\\", "\\").replace('\\"', '"')
+    return value
+
+
+def dump_options_header(header, options):
+    """The reverse function to :func:`parse_options_header`.
+
+    :param header: the header to dump
+    :param options: a dict of options to append.
+    """
+    segments = []
+    if header is not None:
+        segments.append(header)
+    for key, value in iteritems(options):
+        if value is None:
+            segments.append(key)
+        else:
+            segments.append("%s=%s" % (key, quote_header_value(value)))
+    return "; ".join(segments)
+
+
+def dump_header(iterable, allow_token=True):
+    """Dump an HTTP header again.  This is the reversal of
+    :func:`parse_list_header`, :func:`parse_set_header` and
+    :func:`parse_dict_header`.  This also quotes strings that include an
+    equals sign unless you pass it as dict of key, value pairs.
+
+    >>> dump_header({'foo': 'bar baz'})
+    'foo="bar baz"'
+    >>> dump_header(('foo', 'bar baz'))
+    'foo, "bar baz"'
+
+    :param iterable: the iterable or dict of values to quote.
+    :param allow_token: if set to `False` tokens as values are disallowed.
+                        See :func:`quote_header_value` for more details.
+    """
+    if isinstance(iterable, dict):
+        items = []
+        for key, value in iteritems(iterable):
+            if value is None:
+                items.append(key)
+            else:
+                items.append(
+                    "%s=%s" % (key, quote_header_value(value, allow_token=allow_token))
+                )
+    else:
+        items = [quote_header_value(x, allow_token=allow_token) for x in iterable]
+    return ", ".join(items)
+
+
+def parse_list_header(value):
+    """Parse lists as described by RFC 2068 Section 2.
+
+    In particular, parse comma-separated lists where the elements of
+    the list may include quoted-strings.  A quoted-string could
+    contain a comma.  A non-quoted string could have quotes in the
+    middle.  Quotes are removed automatically after parsing.
+
+    It basically works like :func:`parse_set_header` just that items
+    may appear multiple times and case sensitivity is preserved.
+
+    The return value is a standard :class:`list`:
+
+    >>> parse_list_header('token, "quoted value"')
+    ['token', 'quoted value']
+
+    To create a header from the :class:`list` again, use the
+    :func:`dump_header` function.
+
+    :param value: a string with a list header.
+    :return: :class:`list`
+    """
+    result = []
+    for item in _parse_list_header(value):
+        if item[:1] == item[-1:] == '"':
+            item = unquote_header_value(item[1:-1])
+        result.append(item)
+    return result
+
+
+def parse_dict_header(value, cls=dict):
+    """Parse lists of key, value pairs as described by RFC 2068 Section 2 and
+    convert them into a python dict (or any other mapping object created from
+    the type with a dict like interface provided by the `cls` argument):
+
+    >>> d = parse_dict_header('foo="is a fish", bar="as well"')
+    >>> type(d) is dict
+    True
+    >>> sorted(d.items())
+    [('bar', 'as well'), ('foo', 'is a fish')]
+
+    If there is no value for a key it will be `None`:
+
+    >>> parse_dict_header('key_without_value')
+    {'key_without_value': None}
+
+    To create a header from the :class:`dict` again, use the
+    :func:`dump_header` function.
+
+    .. versionchanged:: 0.9
+       Added support for `cls` argument.
+
+    :param value: a string with a dict header.
+    :param cls: callable to use for storage of parsed results.
+    :return: an instance of `cls`
+    """
+    result = cls()
+    if not isinstance(value, text_type):
+        # XXX: validate
+        value = bytes_to_wsgi(value)
+    for item in _parse_list_header(value):
+        if "=" not in item:
+            result[item] = None
+            continue
+        name, value = item.split("=", 1)
+        if value[:1] == value[-1:] == '"':
+            value = unquote_header_value(value[1:-1])
+        result[name] = value
+    return result
+
+
+def parse_options_header(value, multiple=False):
+    """Parse a ``Content-Type`` like header into a tuple with the content
+    type and the options:
+
+    >>> parse_options_header('text/html; charset=utf8')
+    ('text/html', {'charset': 'utf8'})
+
+    This should not be used to parse ``Cache-Control`` like headers that use
+    a slightly different format.  For these headers use the
+    :func:`parse_dict_header` function.
+
+    .. versionchanged:: 0.15
+        :rfc:`2231` parameter continuations are handled.
+
+    .. versionadded:: 0.5
+
+    :param value: the header to parse.
+    :param multiple: Whether try to parse and return multiple MIME types
+    :return: (mimetype, options) or (mimetype, options, mimetype, options, …)
+             if multiple=True
+    """
+    if not value:
+        return "", {}
+
+    result = []
+
+    value = "," + value.replace("\n", ",")
+    while value:
+        match = _option_header_start_mime_type.match(value)
+        if not match:
+            break
+        result.append(match.group(1))  # mimetype
+        options = {}
+        # Parse options
+        rest = match.group(2)
+        continued_encoding = None
+        while rest:
+            optmatch = _option_header_piece_re.match(rest)
+            if not optmatch:
+                break
+            option, count, encoding, language, option_value = optmatch.groups()
+            # Continuations don't have to supply the encoding after the
+            # first line. If we're in a continuation, track the current
+            # encoding to use for subsequent lines. Reset it when the
+            # continuation ends.
+            if not count:
+                continued_encoding = None
+            else:
+                if not encoding:
+                    encoding = continued_encoding
+                continued_encoding = encoding
+            option = unquote_header_value(option)
+            if option_value is not None:
+                option_value = unquote_header_value(option_value, option == "filename")
+                if encoding is not None:
+                    option_value = _unquote(option_value).decode(encoding)
+            if count:
+                # Continuations append to the existing value. For
+                # simplicity, this ignores the possibility of
+                # out-of-order indices, which shouldn't happen anyway.
+                options[option] = options.get(option, "") + option_value
+            else:
+                options[option] = option_value
+            rest = rest[optmatch.end() :]
+        result.append(options)
+        if multiple is False:
+            return tuple(result)
+        value = rest
+
+    return tuple(result) if result else ("", {})
+
+
+def parse_accept_header(value, cls=None):
+    """Parses an HTTP Accept-* header.  This does not implement a complete
+    valid algorithm but one that supports at least value and quality
+    extraction.
+
+    Returns a new :class:`Accept` object (basically a list of ``(value, quality)``
+    tuples sorted by the quality with some additional accessor methods).
+
+    The second parameter can be a subclass of :class:`Accept` that is created
+    with the parsed values and returned.
+
+    :param value: the accept header string to be parsed.
+    :param cls: the wrapper class for the return value (can be
+                         :class:`Accept` or a subclass thereof)
+    :return: an instance of `cls`.
+    """
+    if cls is None:
+        cls = Accept
+
+    if not value:
+        return cls(None)
+
+    result = []
+    for match in _accept_re.finditer(value):
+        quality = match.group(2)
+        if not quality:
+            quality = 1
+        else:
+            quality = max(min(float(quality), 1), 0)
+        result.append((match.group(1), quality))
+    return cls(result)
+
+
+def parse_cache_control_header(value, on_update=None, cls=None):
+    """Parse a cache control header.  The RFC differs between response and
+    request cache control, this method does not.  It's your responsibility
+    to not use the wrong control statements.
+
+    .. versionadded:: 0.5
+       The `cls` was added.  If not specified an immutable
+       :class:`~werkzeug.datastructures.RequestCacheControl` is returned.
+
+    :param value: a cache control header to be parsed.
+    :param on_update: an optional callable that is called every time a value
+                      on the :class:`~werkzeug.datastructures.CacheControl`
+                      object is changed.
+    :param cls: the class for the returned object.  By default
+                :class:`~werkzeug.datastructures.RequestCacheControl` is used.
+    :return: a `cls` object.
+    """
+    if cls is None:
+        cls = RequestCacheControl
+    if not value:
+        return cls(None, on_update)
+    return cls(parse_dict_header(value), on_update)
+
+
+def parse_set_header(value, on_update=None):
+    """Parse a set-like header and return a
+    :class:`~werkzeug.datastructures.HeaderSet` object:
+
+    >>> hs = parse_set_header('token, "quoted value"')
+
+    The return value is an object that treats the items case-insensitively
+    and keeps the order of the items:
+
+    >>> 'TOKEN' in hs
+    True
+    >>> hs.index('quoted value')
+    1
+    >>> hs
+    HeaderSet(['token', 'quoted value'])
+
+    To create a header from the :class:`HeaderSet` again, use the
+    :func:`dump_header` function.
+
+    :param value: a set header to be parsed.
+    :param on_update: an optional callable that is called every time a
+                      value on the :class:`~werkzeug.datastructures.HeaderSet`
+                      object is changed.
+    :return: a :class:`~werkzeug.datastructures.HeaderSet`
+    """
+    if not value:
+        return HeaderSet(None, on_update)
+    return HeaderSet(parse_list_header(value), on_update)
+
+
+def parse_authorization_header(value):
+    """Parse an HTTP basic/digest authorization header transmitted by the web
+    browser.  The return value is either `None` if the header was invalid or
+    not given, otherwise an :class:`~werkzeug.datastructures.Authorization`
+    object.
+
+    :param value: the authorization header to parse.
+    :return: a :class:`~werkzeug.datastructures.Authorization` object or `None`.
+    """
+    if not value:
+        return
+    value = wsgi_to_bytes(value)
+    try:
+        auth_type, auth_info = value.split(None, 1)
+        auth_type = auth_type.lower()
+    except ValueError:
+        return
+    if auth_type == b"basic":
+        try:
+            username, password = base64.b64decode(auth_info).split(b":", 1)
+        except Exception:
+            return
+        return Authorization(
+            "basic",
+            {
+                "username": to_unicode(username, _basic_auth_charset),
+                "password": to_unicode(password, _basic_auth_charset),
+            },
+        )
+    elif auth_type == b"digest":
+        auth_map = parse_dict_header(auth_info)
+        for key in "username", "realm", "nonce", "uri", "response":
+            if key not in auth_map:
+                return
+        if "qop" in auth_map:
+            if not auth_map.get("nc") or not auth_map.get("cnonce"):
+                return
+        return Authorization("digest", auth_map)
+
+
+def parse_www_authenticate_header(value, on_update=None):
+    """Parse an HTTP WWW-Authenticate header into a
+    :class:`~werkzeug.datastructures.WWWAuthenticate` object.
+
+    :param value: a WWW-Authenticate header to parse.
+    :param on_update: an optional callable that is called every time a value
+                      on the :class:`~werkzeug.datastructures.WWWAuthenticate`
+                      object is changed.
+    :return: a :class:`~werkzeug.datastructures.WWWAuthenticate` object.
+    """
+    if not value:
+        return WWWAuthenticate(on_update=on_update)
+    try:
+        auth_type, auth_info = value.split(None, 1)
+        auth_type = auth_type.lower()
+    except (ValueError, AttributeError):
+        return WWWAuthenticate(value.strip().lower(), on_update=on_update)
+    return WWWAuthenticate(auth_type, parse_dict_header(auth_info), on_update)
+
+
+def parse_if_range_header(value):
+    """Parses an if-range header which can be an etag or a date.  Returns
+    a :class:`~werkzeug.datastructures.IfRange` object.
+
+    .. versionadded:: 0.7
+    """
+    if not value:
+        return IfRange()
+    date = parse_date(value)
+    if date is not None:
+        return IfRange(date=date)
+    # drop weakness information
+    return IfRange(unquote_etag(value)[0])
+
+
+def parse_range_header(value, make_inclusive=True):
+    """Parses a range header into a :class:`~werkzeug.datastructures.Range`
+    object.  If the header is missing or malformed `None` is returned.
+    `ranges` is a list of ``(start, stop)`` tuples where the ranges are
+    non-inclusive.
+
+    .. versionadded:: 0.7
+    """
+    if not value or "=" not in value:
+        return None
+
+    ranges = []
+    last_end = 0
+    units, rng = value.split("=", 1)
+    units = units.strip().lower()
+
+    for item in rng.split(","):
+        item = item.strip()
+        if "-" not in item:
+            return None
+        if item.startswith("-"):
+            if last_end < 0:
+                return None
+            try:
+                begin = int(item)
+            except ValueError:
+                return None
+            end = None
+            last_end = -1
+        elif "-" in item:
+            begin, end = item.split("-", 1)
+            begin = begin.strip()
+            end = end.strip()
+            if not begin.isdigit():
+                return None
+            begin = int(begin)
+            if begin < last_end or last_end < 0:
+                return None
+            if end:
+                if not end.isdigit():
+                    return None
+                end = int(end) + 1
+                if begin >= end:
+                    return None
+            else:
+                end = None
+            last_end = end
+        ranges.append((begin, end))
+
+    return Range(units, ranges)
+
+
+def parse_content_range_header(value, on_update=None):
+    """Parses a range header into a
+    :class:`~werkzeug.datastructures.ContentRange` object or `None` if
+    parsing is not possible.
+
+    .. versionadded:: 0.7
+
+    :param value: a content range header to be parsed.
+    :param on_update: an optional callable that is called every time a value
+                      on the :class:`~werkzeug.datastructures.ContentRange`
+                      object is changed.
+    """
+    if value is None:
+        return None
+    try:
+        units, rangedef = (value or "").strip().split(None, 1)
+    except ValueError:
+        return None
+
+    if "/" not in rangedef:
+        return None
+    rng, length = rangedef.split("/", 1)
+    if length == "*":
+        length = None
+    elif length.isdigit():
+        length = int(length)
+    else:
+        return None
+
+    if rng == "*":
+        return ContentRange(units, None, None, length, on_update=on_update)
+    elif "-" not in rng:
+        return None
+
+    start, stop = rng.split("-", 1)
+    try:
+        start = int(start)
+        stop = int(stop) + 1
+    except ValueError:
+        return None
+
+    if is_byte_range_valid(start, stop, length):
+        return ContentRange(units, start, stop, length, on_update=on_update)
+
+
+def quote_etag(etag, weak=False):
+    """Quote an etag.
+
+    :param etag: the etag to quote.
+    :param weak: set to `True` to tag it "weak".
+    """
+    if '"' in etag:
+        raise ValueError("invalid etag")
+    etag = '"%s"' % etag
+    if weak:
+        etag = "W/" + etag
+    return etag
+
+
+def unquote_etag(etag):
+    """Unquote a single etag:
+
+    >>> unquote_etag('W/"bar"')
+    ('bar', True)
+    >>> unquote_etag('"bar"')
+    ('bar', False)
+
+    :param etag: the etag identifier to unquote.
+    :return: a ``(etag, weak)`` tuple.
+    """
+    if not etag:
+        return None, None
+    etag = etag.strip()
+    weak = False
+    if etag.startswith(("W/", "w/")):
+        weak = True
+        etag = etag[2:]
+    if etag[:1] == etag[-1:] == '"':
+        etag = etag[1:-1]
+    return etag, weak
+
+
+def parse_etags(value):
+    """Parse an etag header.
+
+    :param value: the tag header to parse
+    :return: an :class:`~werkzeug.datastructures.ETags` object.
+    """
+    if not value:
+        return ETags()
+    strong = []
+    weak = []
+    end = len(value)
+    pos = 0
+    while pos < end:
+        match = _etag_re.match(value, pos)
+        if match is None:
+            break
+        is_weak, quoted, raw = match.groups()
+        if raw == "*":
+            return ETags(star_tag=True)
+        elif quoted:
+            raw = quoted
+        if is_weak:
+            weak.append(raw)
+        else:
+            strong.append(raw)
+        pos = match.end()
+    return ETags(strong, weak)
+
+
+def generate_etag(data):
+    """Generate an etag for some data."""
+    return md5(data).hexdigest()
+
+
+def parse_date(value):
+    """Parse one of the following date formats into a datetime object:
+
+    .. sourcecode:: text
+
+        Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
+        Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
+        Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
+
+    If parsing fails the return value is `None`.
+
+    :param value: a string with a supported date format.
+    :return: a :class:`datetime.datetime` object.
+    """
+    if value:
+        t = parsedate_tz(value.strip())
+        if t is not None:
+            try:
+                year = t[0]
+                # unfortunately that function does not tell us if two digit
+                # years were part of the string, or if they were prefixed
+                # with two zeroes.  So what we do is to assume that 69-99
+                # refer to 1900, and everything below to 2000
+                if year >= 0 and year <= 68:
+                    year += 2000
+                elif year >= 69 and year <= 99:
+                    year += 1900
+                return datetime(*((year,) + t[1:7])) - timedelta(seconds=t[-1] or 0)
+            except (ValueError, OverflowError):
+                return None
+
+
+def _dump_date(d, delim):
+    """Used for `http_date` and `cookie_date`."""
+    if d is None:
+        d = gmtime()
+    elif isinstance(d, datetime):
+        d = d.utctimetuple()
+    elif isinstance(d, (integer_types, float)):
+        d = gmtime(d)
+    return "%s, %02d%s%s%s%s %02d:%02d:%02d GMT" % (
+        ("Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun")[d.tm_wday],
+        d.tm_mday,
+        delim,
+        (
+            "Jan",
+            "Feb",
+            "Mar",
+            "Apr",
+            "May",
+            "Jun",
+            "Jul",
+            "Aug",
+            "Sep",
+            "Oct",
+            "Nov",
+            "Dec",
+        )[d.tm_mon - 1],
+        delim,
+        str(d.tm_year),
+        d.tm_hour,
+        d.tm_min,
+        d.tm_sec,
+    )
+
+
+def cookie_date(expires=None):
+    """Formats the time to ensure compatibility with Netscape's cookie
+    standard.
+
+    Accepts a floating point number expressed in seconds since the epoch in, a
+    datetime object or a timetuple.  All times in UTC.  The :func:`parse_date`
+    function can be used to parse such a date.
+
+    Outputs a string in the format ``Wdy, DD-Mon-YYYY HH:MM:SS GMT``.
+
+    :param expires: If provided that date is used, otherwise the current.
+    """
+    return _dump_date(expires, "-")
+
+
+def http_date(timestamp=None):
+    """Formats the time to match the RFC1123 date format.
+
+    Accepts a floating point number expressed in seconds since the epoch in, a
+    datetime object or a timetuple.  All times in UTC.  The :func:`parse_date`
+    function can be used to parse such a date.
+
+    Outputs a string in the format ``Wdy, DD Mon YYYY HH:MM:SS GMT``.
+
+    :param timestamp: If provided that date is used, otherwise the current.
+    """
+    return _dump_date(timestamp, " ")
+
+
+def parse_age(value=None):
+    """Parses a base-10 integer count of seconds into a timedelta.
+
+    If parsing fails, the return value is `None`.
+
+    :param value: a string consisting of an integer represented in base-10
+    :return: a :class:`datetime.timedelta` object or `None`.
+    """
+    if not value:
+        return None
+    try:
+        seconds = int(value)
+    except ValueError:
+        return None
+    if seconds < 0:
+        return None
+    try:
+        return timedelta(seconds=seconds)
+    except OverflowError:
+        return None
+
+
+def dump_age(age=None):
+    """Formats the duration as a base-10 integer.
+
+    :param age: should be an integer number of seconds,
+                a :class:`datetime.timedelta` object, or,
+                if the age is unknown, `None` (default).
+    """
+    if age is None:
+        return
+    if isinstance(age, timedelta):
+        # do the equivalent of Python 2.7's timedelta.total_seconds(),
+        # but disregarding fractional seconds
+        age = age.seconds + (age.days * 24 * 3600)
+
+    age = int(age)
+    if age < 0:
+        raise ValueError("age cannot be negative")
+
+    return str(age)
+
+
+def is_resource_modified(
+    environ, etag=None, data=None, last_modified=None, ignore_if_range=True
+):
+    """Convenience method for conditional requests.
+
+    :param environ: the WSGI environment of the request to be checked.
+    :param etag: the etag for the response for comparison.
+    :param data: or alternatively the data of the response to automatically
+                 generate an etag using :func:`generate_etag`.
+    :param last_modified: an optional date of the last modification.
+    :param ignore_if_range: If `False`, `If-Range` header will be taken into
+                            account.
+    :return: `True` if the resource was modified, otherwise `False`.
+    """
+    if etag is None and data is not None:
+        etag = generate_etag(data)
+    elif data is not None:
+        raise TypeError("both data and etag given")
+    if environ["REQUEST_METHOD"] not in ("GET", "HEAD"):
+        return False
+
+    unmodified = False
+    if isinstance(last_modified, string_types):
+        last_modified = parse_date(last_modified)
+
+    # ensure that microsecond is zero because the HTTP spec does not transmit
+    # that either and we might have some false positives.  See issue #39
+    if last_modified is not None:
+        last_modified = last_modified.replace(microsecond=0)
+
+    if_range = None
+    if not ignore_if_range and "HTTP_RANGE" in environ:
+        # https://tools.ietf.org/html/rfc7233#section-3.2
+        # A server MUST ignore an If-Range header field received in a request
+        # that does not contain a Range header field.
+        if_range = parse_if_range_header(environ.get("HTTP_IF_RANGE"))
+
+    if if_range is not None and if_range.date is not None:
+        modified_since = if_range.date
+    else:
+        modified_since = parse_date(environ.get("HTTP_IF_MODIFIED_SINCE"))
+
+    if modified_since and last_modified and last_modified <= modified_since:
+        unmodified = True
+
+    if etag:
+        etag, _ = unquote_etag(etag)
+        if if_range is not None and if_range.etag is not None:
+            unmodified = parse_etags(if_range.etag).contains(etag)
+        else:
+            if_none_match = parse_etags(environ.get("HTTP_IF_NONE_MATCH"))
+            if if_none_match:
+                # https://tools.ietf.org/html/rfc7232#section-3.2
+                # "A recipient MUST use the weak comparison function when comparing
+                # entity-tags for If-None-Match"
+                unmodified = if_none_match.contains_weak(etag)
+
+            # https://tools.ietf.org/html/rfc7232#section-3.1
+            # "Origin server MUST use the strong comparison function when
+            # comparing entity-tags for If-Match"
+            if_match = parse_etags(environ.get("HTTP_IF_MATCH"))
+            if if_match:
+                unmodified = not if_match.is_strong(etag)
+
+    return not unmodified
+
+
+def remove_entity_headers(headers, allowed=("expires", "content-location")):
+    """Remove all entity headers from a list or :class:`Headers` object.  This
+    operation works in-place.  `Expires` and `Content-Location` headers are
+    by default not removed.  The reason for this is :rfc:`2616` section
+    10.3.5 which specifies some entity headers that should be sent.
+
+    .. versionchanged:: 0.5
+       added `allowed` parameter.
+
+    :param headers: a list or :class:`Headers` object.
+    :param allowed: a list of headers that should still be allowed even though
+                    they are entity headers.
+    """
+    allowed = set(x.lower() for x in allowed)
+    headers[:] = [
+        (key, value)
+        for key, value in headers
+        if not is_entity_header(key) or key.lower() in allowed
+    ]
+
+
+def remove_hop_by_hop_headers(headers):
+    """Remove all HTTP/1.1 "Hop-by-Hop" headers from a list or
+    :class:`Headers` object.  This operation works in-place.
+
+    .. versionadded:: 0.5
+
+    :param headers: a list or :class:`Headers` object.
+    """
+    headers[:] = [
+        (key, value) for key, value in headers if not is_hop_by_hop_header(key)
+    ]
+
+
+def is_entity_header(header):
+    """Check if a header is an entity header.
+
+    .. versionadded:: 0.5
+
+    :param header: the header to test.
+    :return: `True` if it's an entity header, `False` otherwise.
+    """
+    return header.lower() in _entity_headers
+
+
+def is_hop_by_hop_header(header):
+    """Check if a header is an HTTP/1.1 "Hop-by-Hop" header.
+
+    .. versionadded:: 0.5
+
+    :param header: the header to test.
+    :return: `True` if it's an HTTP/1.1 "Hop-by-Hop" header, `False` otherwise.
+    """
+    return header.lower() in _hop_by_hop_headers
+
+
+def parse_cookie(header, charset="utf-8", errors="replace", cls=None):
+    """Parse a cookie.  Either from a string or WSGI environ.
+
+    Per default encoding errors are ignored.  If you want a different behavior
+    you can set `errors` to ``'replace'`` or ``'strict'``.  In strict mode a
+    :exc:`HTTPUnicodeError` is raised.
+
+    .. versionchanged:: 0.5
+       This function now returns a :class:`TypeConversionDict` instead of a
+       regular dict.  The `cls` parameter was added.
+
+    :param header: the header to be used to parse the cookie.  Alternatively
+                   this can be a WSGI environment.
+    :param charset: the charset for the cookie values.
+    :param errors: the error behavior for the charset decoding.
+    :param cls: an optional dict class to use.  If this is not specified
+                       or `None` the default :class:`TypeConversionDict` is
+                       used.
+    """
+    if isinstance(header, dict):
+        header = header.get("HTTP_COOKIE", "")
+    elif header is None:
+        header = ""
+
+    # If the value is an unicode string it's mangled through latin1.  This
+    # is done because on PEP 3333 on Python 3 all headers are assumed latin1
+    # which however is incorrect for cookies, which are sent in page encoding.
+    # As a result we
+    if isinstance(header, text_type):
+        header = header.encode("latin1", "replace")
+
+    if cls is None:
+        cls = TypeConversionDict
+
+    def _parse_pairs():
+        for key, val in _cookie_parse_impl(header):
+            key = to_unicode(key, charset, errors, allow_none_charset=True)
+            if not key:
+                continue
+            val = to_unicode(val, charset, errors, allow_none_charset=True)
+            yield try_coerce_native(key), val
+
+    return cls(_parse_pairs())
+
+
+def dump_cookie(
+    key,
+    value="",
+    max_age=None,
+    expires=None,
+    path="/",
+    domain=None,
+    secure=False,
+    httponly=False,
+    charset="utf-8",
+    sync_expires=True,
+    max_size=4093,
+    samesite=None,
+):
+    """Creates a new Set-Cookie header without the ``Set-Cookie`` prefix
+    The parameters are the same as in the cookie Morsel object in the
+    Python standard library but it accepts unicode data, too.
+
+    On Python 3 the return value of this function will be a unicode
+    string, on Python 2 it will be a native string.  In both cases the
+    return value is usually restricted to ascii as the vast majority of
+    values are properly escaped, but that is no guarantee.  If a unicode
+    string is returned it's tunneled through latin1 as required by
+    PEP 3333.
+
+    The return value is not ASCII safe if the key contains unicode
+    characters.  This is technically against the specification but
+    happens in the wild.  It's strongly recommended to not use
+    non-ASCII values for the keys.
+
+    :param max_age: should be a number of seconds, or `None` (default) if
+                    the cookie should last only as long as the client's
+                    browser session.  Additionally `timedelta` objects
+                    are accepted, too.
+    :param expires: should be a `datetime` object or unix timestamp.
+    :param path: limits the cookie to a given path, per default it will
+                 span the whole domain.
+    :param domain: Use this if you want to set a cross-domain cookie. For
+                   example, ``domain=".example.com"`` will set a cookie
+                   that is readable by the domain ``www.example.com``,
+                   ``foo.example.com`` etc. Otherwise, a cookie will only
+                   be readable by the domain that set it.
+    :param secure: The cookie will only be available via HTTPS
+    :param httponly: disallow JavaScript to access the cookie.  This is an
+                     extension to the cookie standard and probably not
+                     supported by all browsers.
+    :param charset: the encoding for unicode values.
+    :param sync_expires: automatically set expires if max_age is defined
+                         but expires not.
+    :param max_size: Warn if the final header value exceeds this size. The
+        default, 4093, should be safely `supported by most browsers
+        <cookie_>`_. Set to 0 to disable this check.
+    :param samesite: Limits the scope of the cookie such that it will only
+                     be attached to requests if those requests are "same-site".
+
+    .. _`cookie`: http://browsercookielimits.squawky.net/
+    """
+    key = to_bytes(key, charset)
+    value = to_bytes(value, charset)
+
+    if path is not None:
+        path = iri_to_uri(path, charset)
+    domain = _make_cookie_domain(domain)
+    if isinstance(max_age, timedelta):
+        max_age = (max_age.days * 60 * 60 * 24) + max_age.seconds
+    if expires is not None:
+        if not isinstance(expires, string_types):
+            expires = cookie_date(expires)
+    elif max_age is not None and sync_expires:
+        expires = to_bytes(cookie_date(time() + max_age))
+
+    samesite = samesite.title() if samesite else None
+    if samesite not in ("Strict", "Lax", None):
+        raise ValueError("invalid SameSite value; must be 'Strict', 'Lax' or None")
+
+    buf = [key + b"=" + _cookie_quote(value)]
+
+    # XXX: In theory all of these parameters that are not marked with `None`
+    # should be quoted.  Because stdlib did not quote it before I did not
+    # want to introduce quoting there now.
+    for k, v, q in (
+        (b"Domain", domain, True),
+        (b"Expires", expires, False),
+        (b"Max-Age", max_age, False),
+        (b"Secure", secure, None),
+        (b"HttpOnly", httponly, None),
+        (b"Path", path, False),
+        (b"SameSite", samesite, False),
+    ):
+        if q is None:
+            if v:
+                buf.append(k)
+            continue
+
+        if v is None:
+            continue
+
+        tmp = bytearray(k)
+        if not isinstance(v, (bytes, bytearray)):
+            v = to_bytes(text_type(v), charset)
+        if q:
+            v = _cookie_quote(v)
+        tmp += b"=" + v
+        buf.append(bytes(tmp))
+
+    # The return value will be an incorrectly encoded latin1 header on
+    # Python 3 for consistency with the headers object and a bytestring
+    # on Python 2 because that's how the API makes more sense.
+    rv = b"; ".join(buf)
+    if not PY2:
+        rv = rv.decode("latin1")
+
+    # Warn if the final value of the cookie is less than the limit. If the
+    # cookie is too large, then it may be silently ignored, which can be quite
+    # hard to debug.
+    cookie_size = len(rv)
+
+    if max_size and cookie_size > max_size:
+        value_size = len(value)
+        warnings.warn(
+            'The "{key}" cookie is too large: the value was {value_size} bytes'
+            " but the header required {extra_size} extra bytes. The final size"
+            " was {cookie_size} bytes but the limit is {max_size} bytes."
+            " Browsers may silently ignore cookies larger than this.".format(
+                key=key,
+                value_size=value_size,
+                extra_size=cookie_size - value_size,
+                cookie_size=cookie_size,
+                max_size=max_size,
+            ),
+            stacklevel=2,
+        )
+
+    return rv
+
+
+def is_byte_range_valid(start, stop, length):
+    """Checks if a given byte content range is valid for the given length.
+
+    .. versionadded:: 0.7
+    """
+    if (start is None) != (stop is None):
+        return False
+    elif start is None:
+        return length is None or length >= 0
+    elif length is None:
+        return 0 <= start < stop
+    elif start >= stop:
+        return False
+    return 0 <= start < length
+
+
+# circular dependency fun
+from .datastructures import Accept
+from .datastructures import Authorization
+from .datastructures import ContentRange
+from .datastructures import ETags
+from .datastructures import HeaderSet
+from .datastructures import IfRange
+from .datastructures import Range
+from .datastructures import RequestCacheControl
+from .datastructures import TypeConversionDict
+from .datastructures import WWWAuthenticate
+from .urls import iri_to_uri
+
+# DEPRECATED
+from .datastructures import CharsetAccept as _CharsetAccept
+from .datastructures import Headers as _Headers
+from .datastructures import LanguageAccept as _LanguageAccept
+from .datastructures import MIMEAccept as _MIMEAccept
+
+
+class MIMEAccept(_MIMEAccept):
+    def __init__(self, *args, **kwargs):
+        warnings.warn(
+            "'werkzeug.http.MIMEAccept' has moved to 'werkzeug"
+            ".datastructures.MIMEAccept' as of version 0.5. This old"
+            " import will be removed in version 1.0.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        super(MIMEAccept, self).__init__(*args, **kwargs)
+
+
+class CharsetAccept(_CharsetAccept):
+    def __init__(self, *args, **kwargs):
+        warnings.warn(
+            "'werkzeug.http.CharsetAccept' has moved to 'werkzeug"
+            ".datastructures.CharsetAccept' as of version 0.5. This old"
+            " import will be removed in version 1.0.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        super(CharsetAccept, self).__init__(*args, **kwargs)
+
+
+class LanguageAccept(_LanguageAccept):
+    def __init__(self, *args, **kwargs):
+        warnings.warn(
+            "'werkzeug.http.LanguageAccept' has moved to 'werkzeug"
+            ".datastructures.LanguageAccept' as of version 0.5. This"
+            " old import will be removed in version 1.0.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        super(LanguageAccept, self).__init__(*args, **kwargs)
+
+
+class Headers(_Headers):
+    def __init__(self, *args, **kwargs):
+        warnings.warn(
+            "'werkzeug.http.Headers' has moved to 'werkzeug"
+            ".datastructures.Headers' as of version 0.5. This old"
+            " import will be removed in version 1.0.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        super(Headers, self).__init__(*args, **kwargs)