52 lines
953 B
Go
52 lines
953 B
Go
package shadow
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import (
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"sync"
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)
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// Value is a struct that coordinates a value between two
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// parallel routines. It is similar to atomic.Value except that when
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// Value is called if it isn't set it will wait for it.
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type Value struct {
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lock sync.Mutex
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cond *sync.Cond
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value interface{}
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valueSet bool
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}
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// Value returns the value that was set.
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func (w *Value) Value() interface{} {
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w.lock.Lock()
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defer w.lock.Unlock()
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// If we already have a value just return
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for !w.valueSet {
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// No value, setup the condition variable if we have to
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if w.cond == nil {
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w.cond = sync.NewCond(&w.lock)
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}
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// Wait on it
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w.cond.Wait()
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}
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// Return the value
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return w.value
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}
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// SetValue sets the value.
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func (w *Value) SetValue(v interface{}) {
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w.lock.Lock()
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defer w.lock.Unlock()
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// Set the value
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w.valueSet = true
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w.value = v
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// If we have a condition, clear it
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if w.cond != nil {
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w.cond.Broadcast()
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w.cond = nil
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}
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}
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