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# Copyright 2018 Google 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.
require 'linked-list'
# A linked list node that tracks its order reltaive to other nodes.
#
# This assumes that, while nodes may be added or removed from a given list, a
# given node object will only ever have one position in the list. This invariant
# is maintained by all methods of LinkedList::List other than
# LinkedList::List#reverse and LinkedList::List#reverse!.
#
# We use this to efficiently determine where to insert a new file relative to
# existing files with HRX#write.
class HRX::OrderedNode < LinkedList::Node # :nodoc:
def initialize(data)
super
@order = nil
end
# The relative order of this node.
#
# This is guaranteed to be greater than the order of all nodes before this in
# the list, and less than the order of all nodes after it. Otherwise it
# provides no guarantees.
#
# This is not guaranteed to be stale over time.
def order
@order || 0
end
def next=(other)
@order ||=
if other.nil?
nil
elsif other.prev
(other.prev.order + other.order) / 2.0
else
other.order - 1
end
super
end
def prev=(other)
@order ||=
if other.nil?
nil
elsif other.next&.order
(other.next.order + other.order) / 2.0
else
other.order + 1
end
super
end
end
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