45 lines
836 B
Go
45 lines
836 B
Go
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package chansync
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import (
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"sync"
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"sync/atomic"
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"github.com/anacrolix/chansync/events"
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)
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// SetOnce is a boolean value that can only be flipped from false to true.
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type SetOnce struct {
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ch chan struct{}
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// Could be faster than trying to receive from ch
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closed uint32
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initOnce sync.Once
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closeOnce sync.Once
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}
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// Returns a channel that is closed when the event is flagged.
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func (me *SetOnce) Done() events.Done {
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me.init()
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return me.ch
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}
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func (me *SetOnce) init() {
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me.initOnce.Do(func() {
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me.ch = make(chan struct{})
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})
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}
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// Set only returns true the first time it is called.
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func (me *SetOnce) Set() (first bool) {
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me.closeOnce.Do(func() {
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me.init()
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first = true
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atomic.StoreUint32(&me.closed, 1)
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close(me.ch)
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})
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return
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}
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func (me *SetOnce) IsSet() bool {
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return atomic.LoadUint32(&me.closed) != 0
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}
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