137 lines
3.3 KiB
Go
137 lines
3.3 KiB
Go
/*
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* queue.go
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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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package main
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import (
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"fmt"
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"github.com/apple/foundationdb/bindings/go/src/fdb"
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"github.com/apple/foundationdb/bindings/go/src/fdb/directory"
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"github.com/apple/foundationdb/bindings/go/src/fdb/subspace"
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"github.com/apple/foundationdb/bindings/go/src/fdb/tuple"
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"log"
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)
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type EmptyQueueError struct{}
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func (q EmptyQueueError) Error() string {
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return "Queue is Empty"
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}
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func clear_subspace(trtr fdb.Transactor, sub subspace.Subspace) error {
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_, err := trtr.Transact(func(tr fdb.Transaction) (interface{}, error) {
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tr.ClearRange(sub)
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return nil, nil
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})
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return err
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}
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type Queue struct {
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QueueSS subspace.Subspace
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}
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func (q *Queue) NewQueue(ss subspace.Subspace) {
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q.QueueSS = ss
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}
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func (q *Queue) Dequeue(trtr fdb.Transactor) (interface{}, error) {
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i, e := trtr.Transact(func(tr fdb.Transaction) (interface{}, error) {
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item, err := q.FirstItem(tr)
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if err != nil {
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return nil, err
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}
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tr.Clear(item.(fdb.KeyValue).Key)
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return item.(fdb.KeyValue).Value, err
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})
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return i, e
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}
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func (q *Queue) Enqueue(trtr fdb.Transactor, item interface{}) (interface{}, error) {
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i, e := trtr.Transact(func(tr fdb.Transaction) (interface{}, error) {
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index, err := q.LastIndex(tr)
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if err != nil {
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return nil, err
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}
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ki, err := q.QueueSS.Unpack(index.(fdb.Key))
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if err != nil {
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return nil, err
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}
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tr.Set(q.QueueSS.Pack(tuple.Tuple{ki[0].(int64) + 1}), []byte(item.(string)))
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return nil, nil
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})
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return i, e
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}
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func (q *Queue) LastIndex(trtr fdb.Transactor) (interface{}, error) {
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i, e := trtr.ReadTransact(func(rtr fdb.ReadTransaction) (interface{}, error) {
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r, err := rtr.Snapshot().GetRange(q.QueueSS, fdb.RangeOptions{1, 0, true}).GetSliceWithError()
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if len(r) == 0 {
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return q.QueueSS.Pack(tuple.Tuple{0}), nil
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}
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return r[0].Key, err
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})
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return i, e
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}
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func (q *Queue) FirstItem(trtr fdb.Transactor) (interface{}, error) {
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i, e := trtr.ReadTransact(func(rtr fdb.ReadTransaction) (interface{}, error) {
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r, err := rtr.GetRange(q.QueueSS, fdb.RangeOptions{1, 0, false}).GetSliceWithError()
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if len(r) == 0 {
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return nil, EmptyQueueError{}
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}
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return r[0], err
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})
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return i, e
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}
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func main() {
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fmt.Println("Queue Example Program")
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fdb.MustAPIVersion(630)
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db := fdb.MustOpenDefault()
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QueueDemoDir, err := directory.CreateOrOpen(db, []string{"Queue"}, nil)
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if err != nil {
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log.Fatal(err)
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}
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clear_subspace(db, QueueDemoDir)
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var q Queue
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q.NewQueue(QueueDemoDir.Sub("Queue"))
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q.Enqueue(db, "test")
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q.Enqueue(db, "test1")
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q.Enqueue(db, "test2")
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q.Enqueue(db, "test3")
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for i := 0; i < 5; i++ {
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item, e := q.Dequeue(db)
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if e != nil {
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log.Fatal(e)
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}
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fmt.Println(string(item.([]byte)))
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}
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}
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