452 lines
14 KiB
Python
452 lines
14 KiB
Python
# local imports
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from shep.error import (
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StateExists,
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StateInvalid,
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StateItemExists,
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StateItemNotFound,
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)
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class State:
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"""State is an in-memory bitmasked state store for key-value pairs, or even just keys alone.
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A State is comprised of a number of atomic state bits, and zero or more aliases that represent unique combinations of these bits.
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The State object will enforce that duplicate states cannot exist. It will also enforce that all alias states are composed of valid atomic states.
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:param bits: Number of atomic states that this State object will represent (i.e. number of bits).
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:type bits: int
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:param logger: Standard library logging instance to output to
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:type logger: logging.Logger
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"""
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def __init__(self, bits, logger=None):
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self.__bits = bits
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self.__limit = (1 << bits) - 1
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self.__c = 0
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self.NEW = 0
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self.__reverse = {0: self.NEW}
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self.__keys = {self.NEW: []}
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self.__keys_reverse = {}
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self.__contents = {}
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# return true if v is a single-bit state
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def __is_pure(self, v):
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if v == 0:
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return True
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c = 1
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for i in range(self.__bits):
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if c & v > 0:
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break
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c <<= 1
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return c == v
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# validates a state name and return its canonical representation
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def __check_name_valid(self, k):
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if not k.isalpha():
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raise ValueError('only alpha')
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return k.upper()
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# enforces name validity, aswell as name uniqueness
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def __check_name(self, k):
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k = self.__check_name_valid(k)
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try:
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getattr(self, k)
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raise StateExists(k)
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except AttributeError:
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pass
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return k
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# enforces state value validity and uniqueness
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def __check_valid(self, v):
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v = self.__check_value_typ(v)
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if self.__reverse.get(v):
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raise StateExists(v)
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return v
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# enforces state value within bit limit of instantiation
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def __check_limit(self, v):
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if v > self.__limit:
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raise OverflowError(v)
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return v
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# enforces state value validity, uniqueness and value limit
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def __check_value(self, v):
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v = self.__check_valid(v)
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self.__check_limit(v)
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return v
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# enforces state value validity
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def __check_value_typ(self, v):
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return int(v)
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# enforces state value validity within the currently registered states (number of add calls vs number of bits in instantiation).
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def __check_value_cursor(self, v):
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v = self.__check_value_typ(v)
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if v > 1 << self.__c:
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raise StateInvalid(v)
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return v
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# set a bit for state of the given key
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def __set(self, k, v):
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setattr(self, k, v)
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self.__reverse[v] = k
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self.__c += 1
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# check validity of key to register state for
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def __check_key(self, item):
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if self.__keys_reverse.get(item) != None:
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raise StateItemExists(item)
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# adds a new key to the state store
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def __add_state_list(self, state, item):
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if self.__keys.get(state) == None:
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self.__keys[state] = []
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self.__keys[state].append(item)
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self.__keys_reverse[item] = state
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# Get index of a key for a given state.
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# A key should only ever exist in one state.
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# A failed lookup should indicate a mistake on the caller part, (it may also indicate corruption, but probanbly impossible to tell the difference)
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def __state_list_index(self, item, state_list):
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idx = -1
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try:
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idx = state_list.index(item)
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except ValueError:
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pass
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if idx == -1:
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raise StateCorruptionError() # should have state int here as value
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return idx
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# Add a state to the store.
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#
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# :param k: State name
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# :type k: str
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# :raises shep.error.StateExists: State name is already registered
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def add(self, k):
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v = 1 << self.__c
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k = self.__check_name(k)
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v = self.__check_value(v)
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self.__set(k, v)
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# Add an alias for a combination of states in the store.
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#
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# State aggregates may be provided as comma separated values or as a single (or'd) integer value.
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#|
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# :param k: Alias name
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# :type k: str
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# :param *args: One or more states to aggregate for this alias.
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# :type *args: int or list of ints
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# :raises StateInvalid: Attempt to create alias for one or more atomic states that do not exist.
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# :raises ValueError: Attempt to use bit value as alias
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def alias(self, k, *args):
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k = self.__check_name(k)
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v = 0
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for a in args:
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a = self.__check_value_cursor(a)
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v = self.__check_limit(v | a)
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if self.__is_pure(v):
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raise ValueError('use add to add pure values')
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self.__set(k, v)
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# Return list of all unique atomic and alias states.
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#
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# :rtype: list of ints
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# :return: states
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def all(self):
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l = []
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for k in dir(self):
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if k[0] == '_':
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continue
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if k.upper() != k:
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continue
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l.append(k)
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l.sort()
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return l
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# Retrieve that string representation of the state attribute represented by the given state integer value.
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#
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# :param v: State integer
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# :type v: int
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# :raises StateInvalid: State corresponding to given integer not found
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# :rtype: str
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# :return: State name
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def name(self, v):
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if v == None or v == 0:
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return 'NEW'
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k = self.__reverse.get(v)
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if k == None:
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raise StateInvalid(v)
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return k
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# Retrieve the real state integer value corresponding to an attribute name.
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#
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# :param k: Attribute name
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# :type k: str
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# :raises ValueError: Invalid attribute name
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# :raises AttributeError: Attribute not found
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# :rtype: int
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# :return: Numeric state value
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def from_name(self, k):
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k = self.__check_name_valid(k)
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return getattr(self, k)
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# Match against all stored states.
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#
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# If pure is set, only match against the single atomic state will be returned.
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#
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# :param v: Integer state to match
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# :type v: int
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# :param pure: Match only pure states
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# :type pure: bool
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# :raises KeyError: Unknown state
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# :rtype: tuple
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# :return: 0: Alias that input resolves to, 1: list of atomic states that matches the state
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def match(self, v, pure=False):
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alias = None
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if not pure:
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alias = self.__reverse.get(v)
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r = []
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c = 1
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for i in range(self.__bits):
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if v & c > 0:
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try:
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k = self.__reverse[c]
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r.append(k)
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except KeyError:
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pass
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c <<= 1
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return (alias, r,)
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# Add a key to an existing state.
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#
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# If no state it specified, the default state attribute "NEW" will be used.
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#
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# Contents may be supplied as value to pair with the given key. Contents may be changed later by calling the `replace` method.
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#
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# :param key: Content key to add
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# :type key: str
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# :param state: Initial state for the put. If not given, initial state will be NEW
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# :type state: int
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# :param contents: Contents to associate with key. A valie of None should be recognized as an undefined value as opposed to a zero-length value throughout any backend
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# :type contents: str
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# :raises StateItemExists: Content key has already been added
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# :raises StateInvalid: Given state has not been registered
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# :rtype: integer
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# :return: Resulting state that key is put under (should match the input state)
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def put(self, key, state=None, contents=None):
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if state == None:
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state = self.NEW
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elif self.__reverse.get(state) == None:
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raise StateInvalid(state)
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self.__check_key(key)
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self.__add_state_list(state, key)
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if contents != None:
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self.__contents[key] = contents
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return state
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# Move a given content key from one state to another.
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#
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# :param key: Key to move
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# :type key: str
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# :param to_state: Numeric state to move to (may be atomic or alias)
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# :type to_state: integer
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# :raises StateItemNotFound: Given key has not been registered
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# :raises StateInvalid: Given state has not been registered
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# :rtype: integer
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# :return: Resulting state from move (should match the state given as input)
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def move(self, key, to_state):
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current_state = self.__keys_reverse.get(key)
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if current_state == None:
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raise StateItemNotFound(key)
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new_state = self.__reverse.get(to_state)
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if new_state == None:
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raise StateInvalid(to_state)
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return self.__move(key, current_state, to_state)
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# implementation for state move that ensures integrity of keys and states.
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def __move(self, key, from_state, to_state):
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current_state_list = self.__keys.get(from_state)
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if current_state_list == None:
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raise StateCorruptionError(current_state)
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idx = self.__state_list_index(key, current_state_list)
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new_state_list = self.__keys.get(to_state)
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if current_state_list == None:
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raise StateCorruptionError(to_state)
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self.__add_state_list(to_state, key)
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current_state_list.pop(idx)
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return to_state
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# Move to an alias state by setting a single bit.
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#
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# :param key: Content key to modify state for
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# :type key: str
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# :param or_state: Atomic stat to add
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# :type or_state: int
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# :raises ValueError: State is not a single bit state
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# :raises StateItemNotFound: Content key is not registered
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# :raises StateInvalid: Resulting state after addition of atomic state is unknown
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# :rtype: int
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# :returns: Resulting state
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def set(self, key, or_state):
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if not self.__is_pure(or_state):
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raise ValueError('can only apply using single bit states')
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current_state = self.__keys_reverse.get(key)
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if current_state == None:
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raise StateItemNotFound(key)
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to_state = current_state | or_state
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new_state = self.__reverse.get(to_state)
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if new_state == None:
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raise StateInvalid('resulting to state is unknown: {}'.format(to_state))
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return self.__move(key, current_state, to_state)
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# Unset a single bit, moving to a pure or alias state.
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#
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# The resulting state cannot be NEW (0).
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#
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# :param key: Content key to modify state for
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# :type key: str
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# :param or_state: Atomic stat to add
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# :type or_state: int
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# :raises ValueError: State is not a single bit state, or attempts to revert to NEW
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# :raises StateItemNotFound: Content key is not registered
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# :raises StateInvalid: Resulting state after addition of atomic state is unknown
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# :rtype: int
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# :returns: Resulting state
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def unset(self, key, not_state):
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if not self.__is_pure(not_state):
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raise ValueError('can only apply using single bit states')
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current_state = self.__keys_reverse.get(key)
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if current_state == None:
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raise StateItemNotFound(key)
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to_state = current_state & (~not_state)
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if to_state == current_state:
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raise ValueError('invalid change for state {}: {}'.format(key, not_state))
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if to_state == self.NEW:
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raise ValueError('State {} for {} cannot be reverted to NEW'.format(current_state, key))
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new_state = self.__reverse.get(to_state)
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if new_state == None:
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raise StateInvalid('resulting to state is unknown: {}'.format(to_state))
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return self.__move(key, current_state, to_state)
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# Return the current numeric state for the given content key.
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#
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# :param key: Key to return content for
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# :type key: str
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# :raises StateItemNotFound: Content key is unknown
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# :rtype: int
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# :returns: State
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def state(self, key):
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state = self.__keys_reverse.get(key)
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if state == None:
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raise StateItemNotFound(key)
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return state
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# Retrieve the content for a content key.
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#
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# :param key: Content key to retrieve content for
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# :type key: str
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# :rtype: any
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# :returns: Content
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def get(self, key):
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return self.__contents.get(key)
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# List all content keys matching a state.
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#
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# :param state: State to match
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# :type state: int
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# :rtype: list of str
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# :returns: Matching content keys
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def list(self, state):
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try:
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return self.__keys[state]
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except KeyError:
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return []
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# Noop method for interface implementation providing sync to backend.
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#
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# :param state: State to sync.
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# :type state:
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# :todo: (for higher level implementer) if sync state is none, sync all
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def sync(self, state):
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pass
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def path(self, state, key=None):
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return None
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def peek(self, key):
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state = self.__keys_reverse.get(key)
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if state == None:
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raise StateItemNotFound(key)
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if not self.__is_pure(state):
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raise StateInvalid('cannot run next on an alias state')
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if state == 0:
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state = 1
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else:
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state <<= 1
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if state > self.__c:
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raise StateInvalid('unknown state {}'.format(state))
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return state
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def next(self, key):
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from_state = self.state(key)
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new_state = self.peek(key)
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return self.__move(key, from_state, new_state)
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def replace(self, key, contents):
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self.state(key)
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self.__contents[key] = contents
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