/
converters.py
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/
converters.py
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# Copyright 2017 by Rackspace Hosting, Inc.
#
# 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.
import abc
from datetime import datetime
from math import isfinite
from typing import Optional
import uuid
__all__ = (
'BaseConverter',
'DateTimeConverter',
'FloatConverter',
'IntConverter',
'UUIDConverter',
)
# PERF(kgriffs): Avoid an extra namespace lookup when using this function
strptime = datetime.strptime
class BaseConverter(metaclass=abc.ABCMeta):
"""Abstract base class for URI template field converters."""
CONSUME_MULTIPLE_SEGMENTS = False
"""When set to ``True`` it indicates that this converter will consume
multiple URL path segments. Currently a converter with
``CONSUME_MULTIPLE_SEGMENTS=True`` must be at the end of the URL template
effectively meaning that it will consume all of the remaining URL path
segments.
"""
@abc.abstractmethod # pragma: no cover
def convert(self, value):
"""Convert a URI template field value to another format or type.
Args:
value (str or List[str]): Original string to convert.
If ``CONSUME_MULTIPLE_SEGMENTS=True`` this value is a
list of strings containing the path segments matched by
the converter.
Returns:
object: Converted field value, or ``None`` if the field
can not be converted.
"""
def _consumes_multiple_segments(converter):
return getattr(converter, 'CONSUME_MULTIPLE_SEGMENTS', False)
class IntConverter(BaseConverter):
"""Converts a field value to an int.
Identifier: `int`
Keyword Args:
num_digits (int): Require the value to have the given
number of digits.
min (int): Reject the value if it is less than this number.
max (int): Reject the value if it is greater than this number.
"""
__slots__ = ('_num_digits', '_min', '_max')
def __init__(self, num_digits=None, min=None, max=None):
if num_digits is not None and num_digits < 1:
raise ValueError('num_digits must be at least 1')
self._num_digits = num_digits
self._min = min
self._max = max
def convert(self, value):
if self._num_digits is not None and len(value) != self._num_digits:
return None
# NOTE(kgriffs): int() will accept numbers with preceding or
# trailing whitespace, so we need to do our own check. Using
# strip() is faster than either a regex or a series of or'd
# membership checks via "in", esp. as the length of contiguous
# numbers in the value grows.
if value.strip() != value:
return None
try:
value = int(value)
except ValueError:
return None
return self._validate_min_max_value(value)
def _validate_min_max_value(self, value):
if self._min is not None and value < self._min:
return None
if self._max is not None and value > self._max:
return None
return value
class FloatConverter(IntConverter):
"""Converts a field value to an float.
Identifier: `float`
Keyword Args:
min (float): Reject the value if it is less than this number.
max (float): Reject the value if it is greater than this number.
finite (bool) : Determines whether or not to only match ordinary
finite numbers (default: ``True``). Set to ``False`` to match
nan, inf, and -inf in addition to finite numbers.
"""
__slots__ = '_finite'
def __init__(
self,
min: Optional[float] = None,
max: Optional[float] = None,
finite: bool = True,
):
self._min = min
self._max = max
self._finite = finite if finite is not None else True
def convert(self, value: str):
if value.strip() != value:
return None
try:
converted = float(value)
if self._finite and not isfinite(converted):
return None
except ValueError:
return None
return self._validate_min_max_value(converted)
class DateTimeConverter(BaseConverter):
"""Converts a field value to a datetime.
Identifier: `dt`
Keyword Args:
format_string (str): String used to parse the field value
into a datetime. Any format recognized by strptime() is
supported (default ``'%Y-%m-%dT%H:%M:%SZ'``).
"""
__slots__ = ('_format_string',)
def __init__(self, format_string='%Y-%m-%dT%H:%M:%SZ'):
self._format_string = format_string
def convert(self, value):
try:
return strptime(value, self._format_string)
except ValueError:
return None
class UUIDConverter(BaseConverter):
"""Converts a field value to a uuid.UUID.
Identifier: `uuid`
In order to be converted, the field value must consist of a
string of 32 hexadecimal digits, as defined in RFC 4122, Section 3.
Note, however, that hyphens and the URN prefix are optional.
"""
def convert(self, value):
try:
return uuid.UUID(value)
except ValueError:
return None
class PathConverter(BaseConverter):
"""Field converted used to match the rest of the path.
This field converter matches the remainder of the URL path,
returning it as a string.
This converter is currently supported only when used at the
end of the URL template.
The classic routing rules of falcon apply also to this converter:
considering the template ``'/foo/bar/{matched_path:path}'``, the path
``'/foo/bar'`` will *not* match the route; ``'/foo/bar/'`` will
match, producing ``matched_path=''``, when
:attr:`~falcon.RequestOptions.strip_url_path_trailing_slash` is ``False``
(the default), while it will *not* match when that option is ``True``.
(See also: :ref:`trailing_slash_in_path`)
"""
CONSUME_MULTIPLE_SEGMENTS = True
def convert(self, value):
return '/'.join(value)
BUILTIN = (
('int', IntConverter),
('dt', DateTimeConverter),
('uuid', UUIDConverter),
('float', FloatConverter),
('path', PathConverter),
)