syncmap: rename DeepCopyMap to CopyMap

Also, remove unnecessary variable

Change-Id: Ic2a8966b14cd4dab4e7e8fcd3496f10940e9b1f7
Reviewed-on: https://go-review.googlesource.com/c/sync/+/848685
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

singleflight/singleflight_test.go

diff --git a/singleflight/singleflight_test.go b/singleflight/singleflight_test.go
index 9d8edc8..921adac 100644
--- a/singleflight/singleflight_test.go
+++ b/singleflight/singleflight_test.go
@@ -46,8 +46,6 @@
 	}
 
 	for _, tc := range testCases {
-		tc := tc
-
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 

syncmap/map_bench_test.go

diff --git a/syncmap/map_bench_test.go b/syncmap/map_bench_test.go
index 9fb7181..dc5ea88 100644
--- a/syncmap/map_bench_test.go
+++ b/syncmap/map_bench_test.go
@@ -19,7 +19,7 @@
 }
 
 func benchMap(b *testing.B, bench bench) {
-	for _, m := range [...]mapInterface{&DeepCopyMap{}, &RWMutexMap{}, &syncmap.Map{}} {
+	for _, m := range [...]mapInterface{&CopyMap{}, &RWMutexMap{}, &syncmap.Map{}} {
 		b.Run(fmt.Sprintf("%T", m), func(b *testing.B) {
 			m = reflect.New(reflect.TypeOf(m).Elem()).Interface().(mapInterface)
 			if bench.setup != nil {
@@ -86,7 +86,7 @@
 
 	benchMap(b, bench{
 		setup: func(b *testing.B, m mapInterface) {
-			if _, ok := m.(*DeepCopyMap); ok {
+			if _, ok := m.(*CopyMap); ok {
 				b.Skip("DeepCopyMap has quadratic running time.")
 			}
 			for i := 0; i < hits; i++ {
@@ -118,7 +118,7 @@
 func BenchmarkLoadOrStoreUnique(b *testing.B) {
 	benchMap(b, bench{
 		setup: func(b *testing.B, m mapInterface) {
-			if _, ok := m.(*DeepCopyMap); ok {
+			if _, ok := m.(*CopyMap); ok {
 				b.Skip("DeepCopyMap has quadratic running time.")
 			}
 		},

syncmap/map_reference_test.go

diff --git a/syncmap/map_reference_test.go b/syncmap/map_reference_test.go
index f9b4dcf..59d4d9b 100644
--- a/syncmap/map_reference_test.go
+++ b/syncmap/map_reference_test.go
@@ -81,21 +81,21 @@
 	}
 }
 
-// DeepCopyMap is an implementation of mapInterface using a Mutex and
-// atomic.Value. It makes deep copies of the map on every write to avoid
-// acquiring the Mutex in Load.
-type DeepCopyMap struct {
+// CopyMap is an implementation of mapInterface using a Mutex and atomic.Value.
+// Each update operation makes a copy of the map (a functional update) so that
+// no published map is mutated. This avoids acquiring the Mutex in Load and Range.
+type CopyMap struct {
 	mu    sync.Mutex
 	clean atomic.Value
 }
 
-func (m *DeepCopyMap) Load(key any) (value any, ok bool) {
+func (m *CopyMap) Load(key any) (value any, ok bool) {
 	clean, _ := m.clean.Load().(map[any]any)
 	value, ok = clean[key]
 	return value, ok
 }
 
-func (m *DeepCopyMap) Store(key, value any) {
+func (m *CopyMap) Store(key, value any) {
 	m.mu.Lock()
 	dirty := m.dirty()
 	dirty[key] = value
@@ -103,7 +103,7 @@
 	m.mu.Unlock()
 }
 
-func (m *DeepCopyMap) LoadOrStore(key, value any) (actual any, loaded bool) {
+func (m *CopyMap) LoadOrStore(key, value any) (actual any, loaded bool) {
 	clean, _ := m.clean.Load().(map[any]any)
 	actual, loaded = clean[key]
 	if loaded {
@@ -124,7 +124,7 @@
 	return actual, loaded
 }
 
-func (m *DeepCopyMap) Delete(key any) {
+func (m *CopyMap) Delete(key any) {
 	m.mu.Lock()
 	dirty := m.dirty()
 	delete(dirty, key)
@@ -132,7 +132,7 @@
 	m.mu.Unlock()
 }
 
-func (m *DeepCopyMap) Range(f func(key, value any) (shouldContinue bool)) {
+func (m *CopyMap) Range(f func(key, value any) (shouldContinue bool)) {
 	clean, _ := m.clean.Load().(map[any]any)
 	for k, v := range clean {
 		if !f(k, v) {
@@ -141,7 +141,7 @@
 	}
 }
 
-func (m *DeepCopyMap) dirty() map[any]any {
+func (m *CopyMap) dirty() map[any]any {
 	clean, _ := m.clean.Load().(map[any]any)
 	dirty := make(map[any]any, len(clean)+1)
 	for k, v := range clean {

syncmap/map_test.go

diff --git a/syncmap/map_test.go b/syncmap/map_test.go
index 912d09c..1f2c337 100644
--- a/syncmap/map_test.go
+++ b/syncmap/map_test.go
@@ -95,7 +95,7 @@
 }
 
 func applyDeepCopyMap(calls []mapCall) ([]mapResult, map[any]any) {
-	return applyCalls(new(DeepCopyMap), calls)
+	return applyCalls(new(CopyMap), calls)
 }
 
 func TestMapMatchesRWMutex(t *testing.T) {