mirror of
https://github.com/golang/go
synced 2024-11-21 18:14:42 -07:00
parent
7886318ca0
commit
a621a7ef74
@ -100,7 +100,6 @@ DIRS=\
|
||||
net/textproto\
|
||||
netchan\
|
||||
nntp\
|
||||
once\
|
||||
os\
|
||||
os/signal\
|
||||
patch\
|
||||
|
@ -1,11 +0,0 @@
|
||||
# Copyright 2009 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.
|
||||
|
||||
include ../../Make.$(GOARCH)
|
||||
|
||||
TARG=once
|
||||
GOFILES=\
|
||||
once.go\
|
||||
|
||||
include ../../Make.pkg
|
@ -1,59 +0,0 @@
|
||||
// Copyright 2009 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.
|
||||
|
||||
// This package provides a single function, Do, to run a function
|
||||
// exactly once, usually used as part of initialization.
|
||||
package once
|
||||
|
||||
import "sync"
|
||||
|
||||
type job struct {
|
||||
done bool
|
||||
sync.Mutex // should probably be sync.Notification or some such
|
||||
}
|
||||
|
||||
var jobs = make(map[func()]*job)
|
||||
var joblock sync.Mutex
|
||||
|
||||
// Do is the the only exported piece of the package.
|
||||
// For one-time initialization that is not done during init,
|
||||
// wrap the initialization in a niladic function f() and call
|
||||
// Do(f)
|
||||
// If multiple processes call Do(f) simultaneously
|
||||
// with the same f argument, only one will call f, and the
|
||||
// others will block until f finishes running.
|
||||
//
|
||||
// Since a func() expression typically evaluates to a differerent
|
||||
// function value each time it is evaluated, it is incorrect to
|
||||
// pass such values to Do. For example,
|
||||
// func f(x int) {
|
||||
// Do(func() { fmt.Println(x) })
|
||||
// }
|
||||
// behaves the same as
|
||||
// func f(x int) {
|
||||
// fmt.Println(x)
|
||||
// }
|
||||
// because the func() expression in the first creates a new
|
||||
// func each time f runs, and each of those funcs is run once.
|
||||
func Do(f func()) {
|
||||
joblock.Lock()
|
||||
j := jobs[f]
|
||||
if j == nil {
|
||||
// run it
|
||||
j = new(job)
|
||||
j.Lock()
|
||||
jobs[f] = j
|
||||
joblock.Unlock()
|
||||
f()
|
||||
j.done = true
|
||||
j.Unlock()
|
||||
} else {
|
||||
// wait for it
|
||||
joblock.Unlock()
|
||||
if j.done != true {
|
||||
j.Lock()
|
||||
j.Unlock()
|
||||
}
|
||||
}
|
||||
}
|
@ -1,30 +0,0 @@
|
||||
// Copyright 2009 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.
|
||||
|
||||
package once_test
|
||||
|
||||
import (
|
||||
"once"
|
||||
"testing"
|
||||
)
|
||||
|
||||
var ncall int
|
||||
|
||||
func call() { ncall++ }
|
||||
|
||||
func TestDo(t *testing.T) {
|
||||
ncall = 0
|
||||
once.Do(call)
|
||||
if ncall != 1 {
|
||||
t.Fatalf("once.Do(call) didn't call(): ncall=%d", ncall)
|
||||
}
|
||||
once.Do(call)
|
||||
if ncall != 1 {
|
||||
t.Fatalf("second once.Do(call) did call(): ncall=%d", ncall)
|
||||
}
|
||||
once.Do(call)
|
||||
if ncall != 1 {
|
||||
t.Fatalf("third once.Do(call) did call(): ncall=%d", ncall)
|
||||
}
|
||||
}
|
@ -185,7 +185,6 @@ var packages = []string{
|
||||
"mime",
|
||||
"net",
|
||||
"nntp",
|
||||
"once",
|
||||
"os",
|
||||
"os/signal",
|
||||
"patch",
|
||||
|
Loading…
Reference in New Issue
Block a user