mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-05 18:12:46 +00:00
62 lines
1.6 KiB
Go
62 lines
1.6 KiB
Go
|
// Copyright 2013 The Go Authors. All rights reserved.
|
||
|
// Use of this source code is governed by a BSD-style
|
||
|
// license that can be found in the LICENSE file.
|
||
|
|
||
|
// Adapted for dns package usage by Miek Gieben.
|
||
|
|
||
|
package dns
|
||
|
|
||
|
import "sync"
|
||
|
import "time"
|
||
|
|
||
|
// call is an in-flight or completed singleflight.Do call
|
||
|
type call struct {
|
||
|
wg sync.WaitGroup
|
||
|
val *Msg
|
||
|
rtt time.Duration
|
||
|
err error
|
||
|
dups int
|
||
|
}
|
||
|
|
||
|
// singleflight represents a class of work and forms a namespace in
|
||
|
// which units of work can be executed with duplicate suppression.
|
||
|
type singleflight struct {
|
||
|
sync.Mutex // protects m
|
||
|
m map[string]*call // lazily initialized
|
||
|
|
||
|
dontDeleteForTesting bool // this is only to be used by TestConcurrentExchanges
|
||
|
}
|
||
|
|
||
|
// Do executes and returns the results of the given function, making
|
||
|
// sure that only one execution is in-flight for a given key at a
|
||
|
// time. If a duplicate comes in, the duplicate caller waits for the
|
||
|
// original to complete and receives the same results.
|
||
|
// The return value shared indicates whether v was given to multiple callers.
|
||
|
func (g *singleflight) Do(key string, fn func() (*Msg, time.Duration, error)) (v *Msg, rtt time.Duration, err error, shared bool) {
|
||
|
g.Lock()
|
||
|
if g.m == nil {
|
||
|
g.m = make(map[string]*call)
|
||
|
}
|
||
|
if c, ok := g.m[key]; ok {
|
||
|
c.dups++
|
||
|
g.Unlock()
|
||
|
c.wg.Wait()
|
||
|
return c.val, c.rtt, c.err, true
|
||
|
}
|
||
|
c := new(call)
|
||
|
c.wg.Add(1)
|
||
|
g.m[key] = c
|
||
|
g.Unlock()
|
||
|
|
||
|
c.val, c.rtt, c.err = fn()
|
||
|
c.wg.Done()
|
||
|
|
||
|
if !g.dontDeleteForTesting {
|
||
|
g.Lock()
|
||
|
delete(g.m, key)
|
||
|
g.Unlock()
|
||
|
}
|
||
|
|
||
|
return c.val, c.rtt, c.err, c.dups > 0
|
||
|
}
|