Add Pointer[T] (#116)

Adds a Pointer[T] type that provide the same functionality as Go 1.19's `sync/atomic.Pointer[T]` in both, Go 1.18 and 1.19. In Go 1.19, this uses the standard library's implementation, and in 1.18 our own custom implementation based on UnsafePointer. For Go 1.17, even though it's now unsupported, this is a no-op. Refs GO-1572 Resolves #115
2022-08-09 16:56:14 -07:00
parent d144bb6cd7
commit 2ab21d86f6
6 changed files with 223 additions and 31 deletions
--- a/go.mod
+++ b/go.mod
@@ -1,8 +1,10 @@
 module go.uber.org/atomic

+require github.com/stretchr/testify v1.3.0
+
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/stretchr/testify v1.3.0
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 )

-go 1.13
+go 1.18
--- a/pointer_go118.go
+++ b/pointer_go118.go
@@ -0,0 +1,60 @@
+// Copyright (c) 2022 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.
+
+//go:build go1.18 && !go1.19
+// +build go1.18,!go1.19
+
+package atomic
+
+import "unsafe"
+
+type Pointer[T any] struct {
+	_ nocmp // disallow non-atomic comparison
+	p UnsafePointer
+}
+
+// NewPointer creates a new Pointer.
+func NewPointer[T any](v *T) *Pointer[T] {
+	var p Pointer[T]
+	if v != nil {
+		p.p.Store(unsafe.Pointer(v))
+	}
+	return &p
+}
+
+// Load atomically loads the wrapped value.
+func (p *Pointer[T]) Load() *T {
+	return (*T)(p.p.Load())
+}
+
+// Store atomically stores the passed value.
+func (p *Pointer[T]) Store(val *T) {
+	p.p.Store(unsafe.Pointer(val))
+}
+
+// Swap atomically swaps the wrapped pointer and returns the old value.
+func (p *Pointer[T]) Swap(val *T) (old *T) {
+	return (*T)(p.p.Swap(unsafe.Pointer(val)))
+}
+
+// CompareAndSwap is an atomic compare-and-swap.
+func (p *Pointer[T]) CompareAndSwap(old, new *T) (swapped bool) {
+	return p.p.CompareAndSwap(unsafe.Pointer(old), unsafe.Pointer(new))
+}
--- a/pointer_go119.go
+++ b/pointer_go119.go
@@ -0,0 +1,61 @@
+// Copyright (c) 2022 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.
+
+//go:build go1.19
+// +build go1.19
+
+package atomic
+
+import "sync/atomic"
+
+// Pointer is an atomic pointer of type *T.
+type Pointer[T any] struct {
+	_ nocmp // disallow non-atomic comparison
+	p atomic.Pointer[T]
+}
+
+// NewPointer creates a new Pointer.
+func NewPointer[T any](v *T) *Pointer[T] {
+	var p Pointer[T]
+	if v != nil {
+		p.p.Store(v)
+	}
+	return &p
+}
+
+// Load atomically loads the wrapped value.
+func (p *Pointer[T]) Load() *T {
+	return p.p.Load()
+}
+
+// Store atomically stores the passed value.
+func (p *Pointer[T]) Store(val *T) {
+	p.p.Store(val)
+}
+
+// Swap atomically swaps the wrapped pointer and returns the old value.
+func (p *Pointer[T]) Swap(val *T) (old *T) {
+	return p.p.Swap(val)
+}
+
+// CompareAndSwap is an atomic compare-and-swap.
+func (p *Pointer[T]) CompareAndSwap(old, new *T) (swapped bool) {
+	return p.p.CompareAndSwap(old, new)
+}
--- a/pointer_test.go
+++ b/pointer_test.go
@@ -0,0 +1,94 @@
+// Copyright (c) 2022 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.
+
+//go:build go1.18
+// +build go1.18
+
+package atomic
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestPointer(t *testing.T) {
+	type foo struct{ v int }
+
+	i := foo{42}
+	j := foo{0}
+	k := foo{1}
+
+	tests := []struct {
+		desc      string
+		newAtomic func() *Pointer[foo]
+		initial   *foo
+	}{
+		{
+			desc: "New",
+			newAtomic: func() *Pointer[foo] {
+				return NewPointer(&i)
+			},
+			initial: &i,
+		},
+		{
+			desc: "New/nil",
+			newAtomic: func() *Pointer[foo] {
+				return NewPointer[foo](nil)
+			},
+			initial: nil,
+		},
+		{
+			desc: "zero value",
+			newAtomic: func() *Pointer[foo] {
+				var p Pointer[foo]
+				return &p
+			},
+			initial: nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			t.Run("Load", func(t *testing.T) {
+				atom := tt.newAtomic()
+				require.Equal(t, tt.initial, atom.Load(), "Load should report nil.")
+			})
+
+			t.Run("Swap", func(t *testing.T) {
+				atom := tt.newAtomic()
+				require.Equal(t, tt.initial, atom.Swap(&k), "Swap didn't return the old value.")
+				require.Equal(t, &k, atom.Load(), "Swap didn't set the correct value.")
+			})
+
+			t.Run("CAS", func(t *testing.T) {
+				atom := tt.newAtomic()
+				require.True(t, atom.CompareAndSwap(tt.initial, &j), "CAS didn't report a swap.")
+				require.Equal(t, &j, atom.Load(), "CAS didn't set the correct value.")
+			})
+
+			t.Run("Store", func(t *testing.T) {
+				atom := tt.newAtomic()
+				atom.Store(&i)
+				require.Equal(t, &i, atom.Load(), "Store didn't set the correct value.")
+			})
+		})
+	}
+}
--- a/tools/go.mod
+++ b/tools/go.mod
@@ -1,6 +1,6 @@
 module go.uber.org/atomic/tools

-go 1.17
+go 1.18

 require (
 	golang.org/x/lint v0.0.0-20210508222113-6edffad5e616
@@ -11,6 +11,6 @@ require (
 	github.com/BurntSushi/toml v1.2.0 // indirect
 	golang.org/x/exp/typeparams v0.0.0-20220722155223-a9213eeb770e // indirect
 	golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 // indirect
-	golang.org/x/sys v0.0.0-20220804214406-8e32c043e418 // indirect
+	golang.org/x/sys v0.0.0-20220808155132-1c4a2a72c664 // indirect
 	golang.org/x/tools v0.1.12 // indirect
 )
--- a/tools/go.sum
+++ b/tools/go.sum
@@ -1,12 +1,7 @@
-github.com/BurntSushi/toml v0.4.1/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
 github.com/BurntSushi/toml v1.2.0 h1:Rt8g24XnyGTyglgET/PRUNlrUeu9F5L+7FilkXfZgs0=
 github.com/BurntSushi/toml v1.2.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
-github.com/yuin/goldmark v1.4.1/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
-github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
-golang.org/x/exp/typeparams v0.0.0-20220218215828-6cf2b201936e/go.mod h1:AbB0pIl9nAr9wVwH+Z2ZpaocVmF5I4GyWCDIsVjR0bk=
 golang.org/x/exp/typeparams v0.0.0-20220722155223-a9213eeb770e h1:7Xs2YCOpMlNqSQSmrrnhlzBXIE/bpMecZplbLePTJvE=
 golang.org/x/exp/typeparams v0.0.0-20220722155223-a9213eeb770e/go.mod h1:AbB0pIl9nAr9wVwH+Z2ZpaocVmF5I4GyWCDIsVjR0bk=
 golang.org/x/lint v0.0.0-20210508222113-6edffad5e616 h1:VLliZ0d+/avPrXXH+OakdXhpJuEoBZuwh1m2j7U6Iug=
@@ -16,35 +11,15 @@ golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 h1:6zppjxzCulZykYSLyVD
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.0.0-20211015210444-4f30a5c0130f/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
-golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20211019181941-9d821ace8654/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220804214406-8e32c043e418 h1:9vYwv7OjYaky/tlAeD7C4oC9EsPTlaFl1H2jS++V+ME=
-golang.org/x/sys v0.0.0-20220804214406-8e32c043e418/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
+golang.org/x/sys v0.0.0-20220808155132-1c4a2a72c664 h1:v1W7bwXHsnLLloWYTVEdvGvA7BHMeBYsPcF0GLDxIRs=
+golang.org/x/sys v0.0.0-20220808155132-1c4a2a72c664/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20200130002326-2f3ba24bd6e7/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
-golang.org/x/tools v0.1.11-0.20220513221640-090b14e8501f/go.mod h1:SgwaegtQh8clINPpECJMqnxLv9I09HLqnW3RMqW0CA4=
 golang.org/x/tools v0.1.12 h1:VveCTK38A2rkS8ZqFY25HIDFscX5X9OoEhJd3quQmXU=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 honnef.co/go/tools v0.3.3 h1:oDx7VAwstgpYpb3wv0oxiZlxY+foCpRAwY7Vk6XpAgA=
 honnef.co/go/tools v0.3.3/go.mod h1:jzwdWgg7Jdq75wlfblQxO4neNaFFSvgc1tD5Wv8U0Yw=