From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- libgo/go/sync/once.go | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) create mode 100644 libgo/go/sync/once.go (limited to 'libgo/go/sync/once.go') diff --git a/libgo/go/sync/once.go b/libgo/go/sync/once.go new file mode 100644 index 000000000..8c877cdec --- /dev/null +++ b/libgo/go/sync/once.go @@ -0,0 +1,35 @@ +// 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 sync + +// Once is an object that will perform exactly one action. +type Once struct { + m Mutex + done bool +} + +// Do calls the function f if and only if the method is being called for the +// first time with this receiver. In other words, given +// var once Once +// if Do(f) is called multiple times, only the first call will invoke f, +// even if f has a different value in each invocation. A new instance of +// Once is required for each function to execute. +// +// Do is intended for initialization that must be run exactly once. Since f +// is niladic, it may be necessary to use a function literal to capture the +// arguments to a function to be invoked by Do: +// config.once.Do(func() { config.init(filename) }) +// +// Because no call to Do returns until the one call to f returns, if f causes +// Do to be called, it will deadlock. +// +func (o *Once) Do(f func()) { + o.m.Lock() + defer o.m.Unlock() + if !o.done { + o.done = true + f() + } +} -- cgit v1.2.3