239 lines
9 KiB
Python
239 lines
9 KiB
Python
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# Copyright 2009-2022 Joshua Bronson. All rights reserved.
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#
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# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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# * Code review nav *
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# (see comments in __init__.py)
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#==============================================================================
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# ← Prev: _bidict.py Current: _orderedbase.py Next: _frozenordered.py →
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#==============================================================================
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"""Provide :class:`OrderedBidictBase`."""
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from __future__ import annotations
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from functools import partial
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from weakref import ref as weakref
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import typing as t
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from ._base import BidictBase, PreparedWrite
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from ._bidict import bidict
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from ._iter import iteritems
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from ._typing import KT, VT, OKT, OVT, MISSING, Items, MapOrItems
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IT = t.TypeVar('IT') # instance type
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AT = t.TypeVar('AT') # attr type
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class WeakAttr(t.Generic[IT, AT]):
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"""Descriptor to automatically manage (de)referencing the given slot as a weakref.
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See https://docs.python.org/3/howto/descriptor.html#managed-attributes
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for an intro to using descriptors like this for managed attributes.
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"""
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def __init__(self, *, slot: str) -> None:
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self.slot = slot
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def __set__(self, instance: IT, value: AT) -> None:
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setattr(instance, self.slot, weakref(value))
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def __get__(self, instance: IT, owner: t.Any) -> AT:
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return getattr(instance, self.slot)() # type: ignore [no-any-return]
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class Node:
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"""A node in a circular doubly-linked list
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used to encode the order of items in an ordered bidict.
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A weak reference to the previous node is stored
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to avoid creating strong reference cycles.
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Referencing/dereferencing the weakref is handled automatically by :class:`WeakAttr`.
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"""
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prv: WeakAttr[Node, Node] = WeakAttr(slot='_prv_weak')
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__slots__ = ('_prv_weak', 'nxt', '__weakref__')
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def __init__(self, prv: Node, nxt: Node) -> None:
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self.prv = prv
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self.nxt = nxt
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def unlink(self) -> None:
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"""Remove self from in between prv and nxt.
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Self's references to prv and nxt are retained so it can be relinked (see below).
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"""
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self.prv.nxt = self.nxt
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self.nxt.prv = self.prv
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def relink(self) -> None:
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"""Restore self between prv and nxt after unlinking (see above)."""
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self.prv.nxt = self.nxt.prv = self
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class SentinelNode(Node):
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"""Special node in a circular doubly-linked list
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that links the first node with the last node.
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When its next and previous references point back to itself
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it represents an empty list.
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"""
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nxt: WeakAttr['SentinelNode', Node] = WeakAttr(slot='_nxt_weak') # type: ignore [assignment]
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__slots__ = ('_nxt_weak',)
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def __init__(self) -> None:
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super().__init__(self, self)
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def iternodes(self, *, reverse: bool = False) -> t.Iterator[Node]:
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"""Iterator yielding nodes in the requested order."""
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attr = 'prv' if reverse else 'nxt'
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node = getattr(self, attr)
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while node is not self:
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yield node
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node = getattr(node, attr)
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def new_last_node(self) -> Node:
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"""Create and return a new terminal node."""
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old_last = self.prv
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new_last = Node(old_last, self)
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old_last.nxt = self.prv = new_last
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return new_last
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class OrderedBidictBase(BidictBase[KT, VT]):
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"""Base class implementing an ordered :class:`BidirectionalMapping`."""
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_repr_delegate: t.ClassVar[t.Any] = list
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_node_by_korv: bidict[t.Any, Node]
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_bykey: bool
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@t.overload
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def __init__(self, __m: t.Mapping[KT, VT], **kw: VT) -> None: ...
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@t.overload
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def __init__(self, __i: Items[KT, VT], **kw: VT) -> None: ...
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@t.overload
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def __init__(self, **kw: VT) -> None: ...
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def __init__(self, *args: MapOrItems[KT, VT], **kw: VT) -> None:
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"""Make a new ordered bidirectional mapping.
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The signature behaves like that of :class:`dict`.
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Items passed in are added in the order they are passed,
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respecting the :attr:`on_dup` class attribute in the process.
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The order in which items are inserted is remembered,
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similar to :class:`collections.OrderedDict`.
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"""
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self._sntl = SentinelNode()
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self._node_by_korv = bidict()
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self._bykey = True
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super().__init__(*args, **kw)
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if t.TYPE_CHECKING:
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@property
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def inverse(self) -> OrderedBidictBase[VT, KT]: ...
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def _make_inverse(self) -> OrderedBidictBase[VT, KT]:
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inv = t.cast(OrderedBidictBase[VT, KT], super()._make_inverse())
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inv._sntl = self._sntl
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inv._node_by_korv = self._node_by_korv
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inv._bykey = not self._bykey
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return inv
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def _assoc_node(self, node: Node, key: KT, val: VT) -> None:
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korv = key if self._bykey else val
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self._node_by_korv.forceput(korv, node)
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def _dissoc_node(self, node: Node) -> None:
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del self._node_by_korv.inverse[node]
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node.unlink()
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def _init_from(self, other: MapOrItems[KT, VT]) -> None:
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"""See :meth:`BidictBase._init_from`."""
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super()._init_from(other)
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bykey = self._bykey
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korv_by_node = self._node_by_korv.inverse
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korv_by_node.clear()
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korv_by_node_set = korv_by_node.__setitem__
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self._sntl.nxt = self._sntl.prv = self._sntl
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new_node = self._sntl.new_last_node
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for (k, v) in iteritems(other):
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korv_by_node_set(new_node(), k if bykey else v)
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def _prep_write(self, newkey: KT, newval: VT, oldkey: OKT[KT], oldval: OVT[VT], save_unwrite: bool) -> PreparedWrite:
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"""See :meth:`bidict.BidictBase._prep_write`."""
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write, unwrite = super()._prep_write(newkey, newval, oldkey, oldval, save_unwrite)
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assoc, dissoc = self._assoc_node, self._dissoc_node
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node_by_korv, bykey = self._node_by_korv, self._bykey
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if oldval is MISSING and oldkey is MISSING: # no key or value duplication
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# {0: 1, 2: 3} + (4, 5) => {0: 1, 2: 3, 4: 5}
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newnode = self._sntl.new_last_node()
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write.append(partial(assoc, newnode, newkey, newval))
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if save_unwrite:
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unwrite.append(partial(dissoc, newnode))
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elif oldval is not MISSING and oldkey is not MISSING: # key and value duplication across two different items
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# {0: 1, 2: 3} + (0, 3) => {0: 3}
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# n1, n2 => n1 (collapse n1 and n2 into n1)
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# oldkey: 2, oldval: 1, oldnode: n2, newkey: 0, newval: 3, newnode: n1
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if bykey:
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oldnode = node_by_korv[oldkey]
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newnode = node_by_korv[newkey]
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else:
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oldnode = node_by_korv[newval]
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newnode = node_by_korv[oldval]
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write.extend((
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partial(dissoc, oldnode),
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partial(assoc, newnode, newkey, newval),
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))
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if save_unwrite:
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unwrite.extend((
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partial(assoc, newnode, newkey, oldval),
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partial(assoc, oldnode, oldkey, newval),
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partial(oldnode.relink,),
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))
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elif oldval is not MISSING: # just key duplication
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# {0: 1, 2: 3} + (2, 4) => {0: 1, 2: 4}
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# oldkey: MISSING, oldval: 3, newkey: 2, newval: 4
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node = node_by_korv[newkey if bykey else oldval]
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write.append(partial(assoc, node, newkey, newval))
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if save_unwrite:
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unwrite.append(partial(assoc, node, newkey, oldval))
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else:
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assert oldkey is not MISSING # just value duplication
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# {0: 1, 2: 3} + (4, 3) => {0: 1, 4: 3}
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# oldkey: 2, oldval: MISSING, newkey: 4, newval: 3
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node = node_by_korv[oldkey if bykey else newval]
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write.append(partial(assoc, node, newkey, newval))
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if save_unwrite:
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unwrite.append(partial(assoc, node, oldkey, newval))
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return write, unwrite
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def __iter__(self) -> t.Iterator[KT]:
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"""Iterator over the contained keys in insertion order."""
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return self._iter(reverse=False)
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def __reversed__(self) -> t.Iterator[KT]:
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"""Iterator over the contained keys in reverse insertion order."""
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return self._iter(reverse=True)
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def _iter(self, *, reverse: bool = False) -> t.Iterator[KT]:
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nodes = self._sntl.iternodes(reverse=reverse)
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korv_by_node = self._node_by_korv.inverse
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if self._bykey:
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for node in nodes:
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yield korv_by_node[node]
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else:
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key_by_val = self._invm
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for node in nodes:
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val = korv_by_node[node]
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yield key_by_val[val]
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# * Code review nav *
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#==============================================================================
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# ← Prev: _bidict.py Current: _orderedbase.py Next: _frozenordered.py →
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#==============================================================================
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