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"""
Represents the Cache-Control header
"""
import re
class UpdateDict(dict):
"""
Dict that has a callback on all updates
"""
# these are declared as class attributes so that
# we don't need to override constructor just to
# set some defaults
updated = None
updated_args = None
def _updated(self):
"""
Assign to new_dict.updated to track updates
"""
updated = self.updated
if updated is not None:
args = self.updated_args
if args is None:
args = (self,)
updated(*args)
def __setitem__(self, key, item):
dict.__setitem__(self, key, item)
self._updated()
def __delitem__(self, key):
dict.__delitem__(self, key)
self._updated()
def clear(self):
dict.clear(self)
self._updated()
def update(self, *args, **kw):
dict.update(self, *args, **kw)
self._updated()
def setdefault(self, key, value=None):
val = dict.setdefault(self, key, value)
if val is value:
self._updated()
return val
def pop(self, *args):
v = dict.pop(self, *args)
self._updated()
return v
def popitem(self):
v = dict.popitem(self)
self._updated()
return v
token_re = re.compile(
r'([a-zA-Z][a-zA-Z_-]*)\s*(?:=(?:"([^"]*)"|([^ \t",;]*)))?')
need_quote_re = re.compile(r'[^a-zA-Z0-9._-]')
class exists_property(object):
"""
Represents a property that either is listed in the Cache-Control
header, or is not listed (has no value)
"""
def __init__(self, prop, type=None):
self.prop = prop
self.type = type
def __get__(self, obj, type=None):
if obj is None:
return self
return self.prop in obj.properties
def __set__(self, obj, value):
if (self.type is not None
and self.type != obj.type):
raise AttributeError(
"The property %s only applies to %s Cache-Control" % (
self.prop, self.type))
if value:
obj.properties[self.prop] = None
else:
if self.prop in obj.properties:
del obj.properties[self.prop]
def __delete__(self, obj):
self.__set__(obj, False)
class value_property(object):
"""
Represents a property that has a value in the Cache-Control header.
When no value is actually given, the value of self.none is returned.
"""
def __init__(self, prop, default=None, none=None, type=None):
self.prop = prop
self.default = default
self.none = none
self.type = type
def __get__(self, obj, type=None):
if obj is None:
return self
if self.prop in obj.properties:
value = obj.properties[self.prop]
if value is None:
return self.none
else:
return value
else:
return self.default
def __set__(self, obj, value):
if (self.type is not None
and self.type != obj.type):
raise AttributeError(
"The property %s only applies to %s Cache-Control" % (
self.prop, self.type))
if value == self.default:
if self.prop in obj.properties:
del obj.properties[self.prop]
elif value is True:
obj.properties[self.prop] = None # Empty value, but present
else:
obj.properties[self.prop] = value
def __delete__(self, obj):
if self.prop in obj.properties:
del obj.properties[self.prop]
class CacheControl(object):
"""
Represents the Cache-Control header.
By giving a type of ``'request'`` or ``'response'`` you can
control what attributes are allowed (some Cache-Control values
only apply to requests or responses).
"""
update_dict = UpdateDict
def __init__(self, properties, type):
self.properties = properties
self.type = type
@classmethod
def parse(cls, header, updates_to=None, type=None):
"""
Parse the header, returning a CacheControl object.
The object is bound to the request or response object
``updates_to``, if that is given.
"""
if updates_to:
props = cls.update_dict()
props.updated = updates_to
else:
props = {}
for match in token_re.finditer(header):
name = match.group(1)
value = match.group(2) or match.group(3) or None
if value:
try:
value = int(value)
except ValueError:
pass
props[name] = value
obj = cls(props, type=type)
if updates_to:
props.updated_args = (obj,)
return obj
def __repr__(self):
return '<CacheControl %r>' % str(self)
# Request values:
# no-cache shared (below)
# no-store shared (below)
# max-age shared (below)
max_stale = value_property('max-stale', none='*', type='request')
min_fresh = value_property('min-fresh', type='request')
# no-transform shared (below)
only_if_cached = exists_property('only-if-cached', type='request')
# Response values:
public = exists_property('public', type='response')
private = value_property('private', none='*', type='response')
no_cache = value_property('no-cache', none='*')
no_store = exists_property('no-store')
no_transform = exists_property('no-transform')
must_revalidate = exists_property('must-revalidate', type='response')
proxy_revalidate = exists_property('proxy-revalidate', type='response')
max_age = value_property('max-age', none=-1)
s_maxage = value_property('s-maxage', type='response')
s_max_age = s_maxage
stale_while_revalidate = value_property(
'stale-while-revalidate', type='response')
stale_if_error = value_property('stale-if-error', type='response')
immutable = exists_property('immutable', type='response')
def __str__(self):
return serialize_cache_control(self.properties)
def copy(self):
"""
Returns a copy of this object.
"""
return self.__class__(self.properties.copy(), type=self.type)
def serialize_cache_control(properties):
if isinstance(properties, CacheControl):
properties = properties.properties
parts = []
for name, value in sorted(properties.items()):
if value is None:
parts.append(name)
continue
value = str(value)
if need_quote_re.search(value):
value = '"%s"' % value
parts.append('%s=%s' % (name, value))
return ', '.join(parts)
|
