def http_date(
timestamp: t.Optional[t.Union[datetime, date, int, float,
struct_time]] = None
) -> str:
"""Format a datetime object or timestamp into an :rfc:`2822` date
string.
This is a wrapper for :func:`email.utils.format_datetime`. It
assumes naive datetime objects are in UTC instead of raising an
exception.
:param timestamp: The datetime or timestamp to format. Defaults to
the current time.
.. versionchanged:: 2.0
Use ``email.utils.format_datetime``. Accept ``date`` objects.
"""
if isinstance(timestamp, date):
if not isinstance(timestamp, datetime):
# Assume plain date is midnight UTC.
timestamp = datetime.combine(timestamp,
time(),
tzinfo=timezone.utc)
else:
# Ensure datetime is timezone-aware.
timestamp = _dt_as_utc(timestamp)
return email.utils.format_datetime(timestamp, usegmt=True)
if isinstance(timestamp, struct_time):
timestamp = mktime(timestamp)
return email.utils.formatdate(timestamp, usegmt=True)
def http_date(
timestamp: t.Optional[t.Union[datetime, int, float]] = None) -> str:
"""Format a datetime object or timestamp into an :rfc:`2822` date
string.
This is a wrapper for :func:`email.utils.format_datetime` and
``.formatdate``. It assumes naive datetime objects are in UTC
instead of raising an exception.
:param timestamp: The datetime or timestamp to format. Defaults to
the current time.
.. versionchanged:: 2.0.0
Use ``email.utils.format_datetime``.
"""
if isinstance(timestamp, datetime):
timestamp = _dt_as_utc(timestamp)
return email.utils.format_datetime(timestamp, usegmt=True)
return email.utils.formatdate(timestamp, usegmt=True)
def is_resource_modified(
environ: "WSGIEnvironment",
etag: t.Optional[str] = None,
data: t.Optional[bytes] = None,
last_modified: t.Optional[t.Union[datetime, str]] = None,
ignore_if_range: bool = True,
) -> bool:
"""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`.
.. versionchanged:: 2.0
SHA-1 is used to generate an etag value for the data. MD5 may
not be available in some environments.
.. versionchanged:: 1.0.0
The check is run for methods other than ``GET`` and ``HEAD``.
"""
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")
unmodified = False
if isinstance(last_modified, str):
last_modified = parse_date(last_modified)
# HTTP doesn't use microsecond, remove it to avoid false positive
# comparisons. Mark naive datetimes as UTC.
if last_modified is not None:
last_modified = _dt_as_utc(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: t.Optional[datetime] = 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)
etag = t.cast(str, 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