Add atomic.Time (#98)

* Add atomic.Time

* fix the arg variable name in the generated code from x to t

* fix build err

* lint

* add changelog entry

* add more tests to show we preserve the whole time.Time struct

* removing add/sub/round

* code review feedback

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 ### Added
 - Add `Float64.Swap` to match int atomic operations.
+- Add `atomic.Time` type for atomic operations on `time.Time` values.
 
 ## [1.8.0] - 2021-06-09
 ### Added

stress_test.go

@@ -27,6 +27,7 @@ import (
 	"sync"
 	"sync/atomic"
 	"testing"
+	"time"
 )
 
 const (
@@ -48,6 +49,7 @@ var _stressTests = map[string]func() func(){
 	"string":   stressString,
 	"duration": stressDuration,
 	"error":    stressError,
+	"time":     stressTime,
 }
 
 func TestStress(t *testing.T) {
@@ -272,3 +274,16 @@ func stressError() func() {
 		atom.Store(nil)
 	}
 }
+
+func stressTime() func() {
+	var atom = NewTime(time.Date(2021, 6, 17, 9, 0, 0, 0, time.UTC))
+	var dayAgo = time.Date(2021, 6, 16, 9, 0, 0, 0, time.UTC)
+	var weekAgo = time.Date(2021, 6, 10, 9, 0, 0, 0, time.UTC)
+	return func() {
+		atom.Load()
+		atom.Store(dayAgo)
+		atom.Load()
+		atom.Store(weekAgo)
+		atom.Store(time.Time{})
+	}
+}

time.go

@@ -0,0 +1,55 @@
+// @generated Code generated by gen-atomicwrapper.
+
+// Copyright (c) 2020-2021 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 (
+	"time"
+)
+
+// Time is an atomic type-safe wrapper for time.Time values.
+type Time struct {
+	_ nocmp // disallow non-atomic comparison
+
+	v Value
+}
+
+var _zeroTime time.Time
+
+// NewTime creates a new Time.
+func NewTime(val time.Time) *Time {
+	x := &Time{}
+	if val != _zeroTime {
+		x.Store(val)
+	}
+	return x
+}
+
+// Load atomically loads the wrapped time.Time.
+func (x *Time) Load() time.Time {
+	return unpackTime(x.v.Load())
+}
+
+// Store atomically stores the passed time.Time.
+func (x *Time) Store(val time.Time) {
+	x.v.Store(packTime(val))
+}

time_ext.go

@@ -0,0 +1,36 @@
+//  Copyright (c) 2021 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 "time"
+
+//go:generate bin/gen-atomicwrapper -name=Time -type=time.Time -wrapped=Value -pack=packTime -unpack=unpackTime -imports time -file=time.go
+
+func packTime(t time.Time) interface{} {
+	return t
+}
+
+func unpackTime(v interface{}) time.Time {
+	if t, ok := v.(time.Time); ok {
+		return t
+	}
+	return time.Time{}
+}

time_test.go

@@ -0,0 +1,86 @@
+// Copyright (c) 2021 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"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTime(t *testing.T) {
+	start := time.Date(2021, 6, 17, 9, 10, 0, 0, time.UTC)
+	atom := NewTime(start)
+
+	require.Equal(t, start, atom.Load(), "Load didn't work")
+	require.Equal(t, time.Time{}, NewTime(time.Time{}).Load(), "Default time value is wrong")
+}
+
+func TestTimeLocation(t *testing.T) {
+	// Check TZ data hasn't been lost from load/store.
+	ny, err := time.LoadLocation("America/New_York")
+	require.NoError(t, err, "Failed to load location")
+	nyTime := NewTime(time.Date(2021, 1, 1, 0, 0, 0, 0, ny))
+
+	var atom Time
+	atom.Store(nyTime.Load())
+
+	assert.Equal(t, ny, atom.Load().Location(), "Location information is wrong")
+}
+
+func TestLargeTime(t *testing.T) {
+	// Check "large/small" time that are beyond int64 ns
+	// representation (< year 1678 or > year 2262) can be
+	// correctly load/store'd.
+	t.Parallel()
+
+	t.Run("future", func(t *testing.T) {
+		future := time.Date(2262, 12, 31, 0, 0, 0, 0, time.UTC)
+		atom := NewTime(future)
+		dayAfterFuture := atom.Load().AddDate(0, 1, 0)
+
+		atom.Store(dayAfterFuture)
+		assert.Equal(t, 2263, atom.Load().Year())
+	})
+
+	t.Run("past", func(t *testing.T) {
+		past := time.Date(1678, 1, 1, 0, 0, 0, 0, time.UTC)
+		atom := NewTime(past)
+		dayBeforePast := atom.Load().AddDate(0, -1, 0)
+
+		atom.Store(dayBeforePast)
+		assert.Equal(t, 1677, atom.Load().Year())
+	})
+}
+
+func TestMonotonic(t *testing.T) {
+	before := NewTime(time.Now())
+	time.Sleep(15 * time.Millisecond)
+	after := NewTime(time.Now())
+
+	// try loading/storing before and test monotonic clock value hasn't been lost
+	bt := before.Load()
+	before.Store(bt)
+	d := after.Load().Sub(before.Load())
+	assert.True(t, 15 <= d.Milliseconds())
+}