6f4d89045a
Doesnt require storing the result of the function in a dedicated global variable with a dedicated getter function
36 lines
568 B
Go
36 lines
568 B
Go
// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
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package utils
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import (
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"fmt"
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"sync"
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"sync/atomic"
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)
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var _ = fmt.Print
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type Once[T any] struct {
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done uint32
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mutex sync.Mutex
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cached_val T
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Run func() T
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}
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func (self *Once[T]) Get() T {
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if atomic.LoadUint32(&self.done) == 0 {
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self.do_slow()
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}
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return self.cached_val
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}
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func (self *Once[T]) do_slow() {
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self.mutex.Lock()
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defer self.mutex.Unlock()
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if atomic.LoadUint32(&self.done) == 0 {
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defer atomic.StoreUint32(&self.done, 1)
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self.cached_val = self.Run()
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}
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}
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