Move package sync to third_party

PiperOrigin-RevId: 231889261
Change-Id: I482f1df055bcedf4edb9fe3fe9b8e9c80085f1a0

1 files changed, 37 insertions, 0 deletions

diff --git a/third_party/gvsync/atomicptr_unsafe.go b/third_party/gvsync/atomicptr_unsafe.go
new file mode 100644
index 000000000..da9f16240
--- /dev/null
+++ b/third_party/gvsync/atomicptr_unsafe.go
@@ -0,0 +1,37 @@
+// Copyright 2019 Google LLC
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package template doesn't exist. This file must be instantiated using the
+// go_template_instance rule in tools/go_generics/defs.bzl.
+package template
+
+import (
+	"sync/atomic"
+	"unsafe"
+)
+
+// Value is a required type parameter.
+type Value struct{}
+
+// An AtomicPtr is a pointer to a value of type Value that can be atomically
+// loaded and stored. The zero value of an AtomicPtr represents nil.
+//
+// Note that copying AtomicPtr by value performs a non-atomic read of the
+// stored pointer, which is unsafe if Store() can be called concurrently; in
+// this case, do `dst.Store(src.Load())` instead.
+type AtomicPtr struct {
+	ptr unsafe.Pointer
+}
+
+// Load returns the value set by the most recent Store. It returns nil if there
+// has been no previous call to Store.
+func (p *AtomicPtr) Load() *Value {
+	return (*Value)(atomic.LoadPointer(&p.ptr))
+}
+
+// Store sets the value returned by Load to x.
+func (p *AtomicPtr) Store(x *Value) {
+	atomic.StorePointer(&p.ptr, (unsafe.Pointer)(x))
+}