80 lines
2.1 KiB
Go
80 lines
2.1 KiB
Go
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// Copyright (C) 2014 Space Monkey, Inc.
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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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package utils
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import (
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"sync"
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)
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// Future is a type that is essentially the inverse of a channel. With a
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// channel, you have multiple senders and one receiver. With a future, you can
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// have multiple receivers and one sender. Additionally, a future protects
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// against double-sends. Since this is usually used for returning function
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// results, we also capture and return error values as well. Use NewFuture
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// to initialize.
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type Future struct {
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mutex *sync.Mutex
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cond *sync.Cond
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received bool
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val interface{}
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err error
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}
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// NewFuture returns an initialized and ready Future.
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func NewFuture() *Future {
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mutex := &sync.Mutex{}
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return &Future{
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mutex: mutex,
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cond: sync.NewCond(mutex),
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received: false,
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val: nil,
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err: nil,
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}
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}
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// Get blocks until the Future has a value set.
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func (self *Future) Get() (interface{}, error) {
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self.mutex.Lock()
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defer self.mutex.Unlock()
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for {
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if self.received {
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return self.val, self.err
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}
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self.cond.Wait()
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}
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}
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// Fired returns whether or not a value has been set. If Fired is true, Get
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// won't block.
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func (self *Future) Fired() bool {
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self.mutex.Lock()
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defer self.mutex.Unlock()
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return self.received
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}
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// Set provides the value to present and future Get calls. If Set has already
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// been called, this is a no-op.
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func (self *Future) Set(val interface{}, err error) {
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self.mutex.Lock()
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defer self.mutex.Unlock()
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if self.received {
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return
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}
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self.received = true
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self.val = val
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self.err = err
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self.cond.Broadcast()
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}
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