Add String as a type-safe wrapper for atomic.Value

stress_test.go

@@ -120,3 +120,18 @@ func TestStressBool(t *testing.T) {
 		}()
 	}
 }
+
+func TestStressString(t *testing.T) {
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(_parallelism))
+	atom := NewString("")
+	for i := 0; i < _parallelism; i++ {
+		go func() {
+			for j := 0; j < _iterations; j++ {
+				atom.Load()
+				atom.Store("abc")
+				atom.Load()
+				atom.Store("def")
+			}
+		}()
+	}
+}

string.go

@@ -0,0 +1,47 @@
+// Copyright (c) 2016 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package atomic
+
+import "sync/atomic"
+
+// String is an atomic type-safe wrapper around atomic.Value for strings.
+type String struct{ atomic.Value }
+
+// NewString creates a String.
+func NewString(s string) *String {
+	return &String{}
+}
+
+// Load atomically loads the wrapped string.
+func (s *String) Load() string {
+	v := s.Value.Load()
+	if v == nil {
+		return ""
+	}
+	return v.(string)
+}
+
+// Store atomically stores the passed string.
+// Note: Converting the string to an interface{} to store in the atomic.Value
+// requires an allocation.
+func (s *String) Store(str string) {
+	s.Value.Store(str)
+}

string_test.go

@@ -0,0 +1,43 @@
+// Copyright (c) 2016 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package atomic
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestStringNoInitialValue(t *testing.T) {
+	atom := &String{}
+	require.Equal(t, "", atom.Load(), "Initial value should be blank string")
+}
+
+func TestString(t *testing.T) {
+	atom := NewString("")
+	require.Equal(t, "", atom.Load(), "Expected Load to return initialized value")
+
+	atom.Store("abc")
+	require.Equal(t, "abc", atom.Load(), "Unexpected value after Store")
+
+	atom = NewString("bcd")
+	require.Equal(t, "", atom.Load(), "Expected Load to return initialized value")
+}