# Copied from the Requests library by Kenneth Reitz et al.
#
# Copyright 2013 Kenneth Reitz
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Data structures.
This module provides additional data structures not found in the
standard library. These classes are hoisted into the `falcon` module
for convenience::
import falcon
things = falcon.CaseInsensitiveDict()
"""
from collections.abc import Mapping
from collections.abc import MutableMapping
# TODO(kgriffs): If we ever diverge from what is upstream in Requests,
# then we will need write tests and remove the "no cover" pragma.
class CaseInsensitiveDict(MutableMapping): # pragma: no cover
"""
A case-insensitive ``dict``-like object.
Implements all methods and operations of
``collections.abc.MutableMapping`` as well as dict's `copy`. Also
provides `lower_items`.
All keys are expected to be strings. The structure remembers the
case of the last key to be set, and ``iter(instance)``,
``keys()``, and ``items()``
will contain case-sensitive keys. However, querying and contains
testing is case insensitive:
cid = CaseInsensitiveDict()
cid['Accept'] = 'application/json'
cid['aCCEPT'] == 'application/json' # True
list(cid) == ['Accept'] # True
For example, ``headers['content-encoding']`` will return the
value of a ``'Content-Encoding'`` response header, regardless
of how the header name was originally stored.
If the constructor, ``.update``, or equality comparison
operations are given keys that have equal ``.lower()``s, the
behavior is undefined.
"""
def __init__(self, data=None, **kwargs):
self._store = dict()
if data is None:
data = {}
self.update(data, **kwargs)
def __setitem__(self, key, value):
# Use the lowercased key for lookups, but store the actual
# key alongside the value.
self._store[key.lower()] = (key, value)
def __getitem__(self, key):
return self._store[key.lower()][1]
def __delitem__(self, key):
del self._store[key.lower()]
def __iter__(self):
return (casedkey for casedkey, mappedvalue in self._store.values())
def __len__(self):
return len(self._store)
def lower_items(self):
"""Like iteritems(), but with all lowercase keys."""
return ((lowerkey, keyval[1]) for (lowerkey, keyval) in self._store.items())
def __eq__(self, other):
if isinstance(other, Mapping):
other = CaseInsensitiveDict(other)
else:
return NotImplemented
# Compare insensitively
return dict(self.lower_items()) == dict(other.lower_items())
# Copy is required
def copy(self):
return CaseInsensitiveDict(self._store.values())
def __repr__(self):
return '%s(%r)' % (self.__class__.__name__, dict(self.items()))
# NOTE(vytas): Although Context is effectively implementing the MutableMapping
# interface, we choose not to subclass MutableMapping to stress the fact that
# Context is, by design, a bare class, and the mapping interface may be
# removed in a future Falcon release.
[docs]
class Context:
"""
Convenience class to hold contextual information in its attributes.
This class is used as the default :class:`~.Request` and :class:`~Response`
context type (see
:attr:`Request.context_type <falcon.Request.context_type>` and
:attr:`Response.context_type <falcon.Response.context_type>`,
respectively).
In Falcon versions prior to 2.0, the default context type was ``dict``. To
ease the migration to attribute-based context object approach, this class
also implements the mapping interface; that is, object attributes are
linked to dictionary items, and vice versa. For instance:
>>> context = falcon.Context()
>>> context.cache_strategy = 'lru'
>>> context.get('cache_strategy')
'lru'
>>> 'cache_strategy' in context
True
"""
def __contains__(self, key):
return self.__dict__.__contains__(key)
def __getitem__(self, key):
# PERF(vytas): On CPython, using this mapping interface (instead of a
# standard dict) to get, set and delete items incurs overhead
# approximately comparable to that of two function calls
# (per get/set/delete operation, that is).
return self.__dict__.__getitem__(key)
def __setitem__(self, key, value):
return self.__dict__.__setitem__(key, value)
def __delitem__(self, key):
self.__dict__.__delitem__(key)
def __iter__(self):
return self.__dict__.__iter__()
def __len__(self):
return self.__dict__.__len__()
def __eq__(self, other):
if isinstance(other, type(self)):
return self.__dict__.__eq__(other.__dict__)
return self.__dict__.__eq__(other)
def __ne__(self, other):
if isinstance(other, type(self)):
return self.__dict__.__ne__(other.__dict__)
return self.__dict__.__ne__(other)
def __hash__(self):
return hash(self.__dict__)
def __repr__(self):
return '{}({})'.format(type(self).__name__, self.__dict__.__repr__())
def __str__(self):
return '{}({})'.format(type(self).__name__, self.__dict__.__str__())
def clear(self):
return self.__dict__.clear()
def copy(self):
ctx = type(self)()
ctx.update(self.__dict__)
return ctx
def get(self, key, default=None):
return self.__dict__.get(key, default)
def items(self):
return self.__dict__.items()
def keys(self):
return self.__dict__.keys()
def pop(self, key, default=None):
return self.__dict__.pop(key, default)
def popitem(self):
return self.__dict__.popitem()
def setdefault(self, key, default_value=None):
return self.__dict__.setdefault(key, default_value)
def update(self, items):
self.__dict__.update(items)
def values(self):
return self.__dict__.values()
[docs]
class ETag(str):
"""Convenience class to represent a parsed HTTP entity-tag.
This class is simply a subclass of ``str`` with a few helper methods and
an extra attribute to indicate whether the entity-tag is weak or strong. The
value of the string is equivalent to what RFC 7232 calls an "opaque-tag",
i.e. an entity-tag sans quotes and the weakness indicator.
Note:
Given that a weak entity-tag comparison can be performed by
using the ``==`` operator (per the example below), only a
:meth:`~.strong_compare` method is provided.
Here is an example ``on_get()`` method that demonstrates how to use instances
of this class::
def on_get(self, req, resp):
content_etag = self._get_content_etag()
for etag in (req.if_none_match or []):
if etag == '*' or etag == content_etag:
resp.status = falcon.HTTP_304
return
# -- snip --
resp.etag = content_etag
resp.status = falcon.HTTP_200
(See also: RFC 7232)
Attributes:
is_weak (bool): ``True`` if the entity-tag is weak, otherwise ``False``.
"""
is_weak = False
[docs]
def strong_compare(self, other):
"""Perform a strong entity-tag comparison.
Two entity-tags are equivalent if both are not weak and their
opaque-tags match character-by-character.
(See also: RFC 7232, Section 2.3.2)
Arguments:
other (ETag): The other :class:`~.ETag` to which you are comparing
this one.
Returns:
bool: ``True`` if the two entity-tags match, otherwise ``False``.
"""
return self == other and not (self.is_weak or other.is_weak)
[docs]
def dumps(self):
"""Serialize the ETag to a string suitable for use in a precondition header.
(See also: RFC 7232, Section 2.3)
Returns:
str: An opaque quoted string, possibly prefixed by a weakness
indicator ``W/``.
"""
if self.is_weak:
# PERF(kgriffs): Simple concatenation like this is slightly faster
# than %s string formatting.
return 'W/"' + self + '"'
return '"' + self + '"'
[docs]
@classmethod
def loads(cls, etag_str):
"""Deserialize a single entity-tag string from a precondition header.
Note:
This method is meant to be used only for parsing a single
entity-tag. It can not be used to parse a comma-separated list of
values.
(See also: RFC 7232, Section 2.3)
Arguments:
etag_str (str): An ASCII string representing a single entity-tag,
as defined by RFC 7232.
Returns:
ETag: An instance of `~.ETag` representing the parsed entity-tag.
"""
value = etag_str
is_weak = False
if value.startswith(('W/', 'w/')):
is_weak = True
value = value[2:]
# NOTE(kgriffs): We allow for an unquoted entity-tag just in case,
# although it has been non-standard to do so since at least 1999
# with the advent of RFC 2616.
if value[:1] == value[-1:] == '"':
value = value[1:-1]
t = cls(value)
t.is_weak = is_weak
return t
