81 lines
1.7 KiB
Ruby
81 lines
1.7 KiB
Ruby
#
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# micro_queue.rb
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#
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# This source file is part of the FoundationDB open source project
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#
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# Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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require 'fdb'
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require 'securerandom'
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FDB.api_version 300
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@db = FDB.open
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def clear_subspace(db,subspace)
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db.transact do |tr|
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tr.clear_range_start_with(subspace.key)
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end
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end
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@queue = FDB::Subspace.new(['Q'])
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clear_subspace(@db,@queue)
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def dequeue(db)
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db.transact do |tr|
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item = first_item(tr)
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next nil if item.nil?
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tr.clear(item.key)
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item.value
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end
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end
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def enqueue(db,value)
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db.transact do |tr|
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tr[@queue[last_index(tr) + 1][SecureRandom.hex(20)]] = value
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end
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end
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def last_index(db)
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value = 0
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db.transact do |tr|
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tr.snapshot.get_range(*@queue.range(), :limit => 1, :reverse => true) do |kv|
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value = @queue.unpack(kv.key)[0]
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end
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end
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value
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end
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def first_item(db)
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pair = nil
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db.transact do |tr|
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tr.get_range(*@queue.range(), :limit=>1) do |kv|
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pair = kv
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end
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end
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pair
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end
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enqueue(@db, "a")
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enqueue(@db, "b")
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enqueue(@db, "c")
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enqueue(@db, "d")
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enqueue(@db, "e")
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puts dequeue(@db)
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puts dequeue(@db)
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puts dequeue(@db)
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puts dequeue(@db)
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puts dequeue(@db)
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puts dequeue(@db) |