99 lines
2.1 KiB
Python
99 lines
2.1 KiB
Python
#
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# micro_queue.py
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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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import os
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import fdb
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fdb.api_version(300)
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db = fdb.open()
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@fdb.transactional
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def clear_subspace(tr, subspace):
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tr.clear_range_startswith(subspace.key())
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queue = fdb.Subspace(('Q',))
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clear_subspace(db, queue)
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@fdb.transactional
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def dequeue(tr):
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item = first_item(tr)
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if item is None:
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return None
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del tr[item.key]
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return item.value
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@fdb.transactional
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def enqueue(tr, value):
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tr[queue[last_index(tr) + 1][os.urandom(20)]] = value
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@fdb.transactional
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def last_index(tr):
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r = queue.range()
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for key, _ in tr.snapshot.get_range(r.start, r.stop, limit=1, reverse=True):
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return queue.unpack(key)[0]
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return 0
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@fdb.transactional
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def first_item(tr):
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r = queue.range()
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for kv in tr.get_range(r.start, r.stop, limit=1):
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return kv
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def smoke_test():
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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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print "dequeue"
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print dequeue(db)
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print dequeue(db)
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print dequeue(db)
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print dequeue(db)
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print dequeue(db)
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enqueue(db, 'a1')
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enqueue(db, 'a2')
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enqueue(db, 'a3')
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enqueue(db, 'a4')
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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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print "dequeue"
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print dequeue(db)
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print dequeue(db)
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print dequeue(db)
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print dequeue(db)
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print dequeue(db)
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print dequeue(db)
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if __name__ == "__main__":
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db = fdb.open()
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clear_subspace(db, queue)
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smoke_test()
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