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