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cmd/viewer,types/views,various: avoid allocations in pointer field getters whenever possible

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In this PR, we add a generic views.ValuePointer type that can be used as a view for pointers
to basic types and struct types that do not require deep cloning and do not have corresponding
view types. Its Get/GetOk methods return stack-allocated shallow copies of the underlying value.

We then update the cmd/viewer codegen to produce getters that return either concrete views
when available or ValuePointer views when not, for pointer fields in generated view types.
This allows us to avoid unnecessary allocations compared to returning pointers to newly
allocated shallow copies.

Updates #14570

Signed-off-by: Nick Khyl <nickk@tailscale.com>
This commit is contained in:
Nick Khyl
2025-01-08 17:21:44 -06:00
committed by Nick Khyl
parent e4385f1c02
commit da9965d51c
15 changed files with 219 additions and 163 deletions
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2
cmd/tsconnect/wasm/wasm_js.go
View File

@@ -282,7 +282,7 @@ func (i *jsIPN) run(jsCallbacks js.Value) {
MachineKey: p.Machine().String(),
NodeKey: p.Key().String(),
},
Online: p.Online(),
Online: p.Online().Clone(),
TailscaleSSHEnabled: p.Hostinfo().TailscaleSSHEnabled(),
}
}),

9
cmd/viewer/tests/tests.go
View File

@@ -37,9 +37,14 @@ type Map struct {
StructWithPtrKey map[StructWithPtrs]int `json:"-"`
}
type StructWithNoView struct {
Value int
}
type StructWithPtrs struct {
Value *StructWithoutPtrs
Int *int
Value *StructWithoutPtrs
Int *int
NoView *StructWithNoView
NoCloneValue *StructWithoutPtrs `codegen:"noclone"`
}

4
cmd/viewer/tests/tests_clone.go
View File

@@ -28,6 +28,9 @@ func (src *StructWithPtrs) Clone() *StructWithPtrs {
if dst.Int != nil {
dst.Int = ptr.To(*src.Int)
}
if dst.NoView != nil {
dst.NoView = ptr.To(*src.NoView)
}
return dst
}
@@ -35,6 +38,7 @@ func (src *StructWithPtrs) Clone() *StructWithPtrs {
var _StructWithPtrsCloneNeedsRegeneration = StructWithPtrs(struct {
Value *StructWithoutPtrs
Int *int
NoView *StructWithNoView
NoCloneValue *StructWithoutPtrs
}{})

45
cmd/viewer/tests/tests_view.go
View File

@@ -61,20 +61,11 @@ func (v *StructWithPtrsView) UnmarshalJSON(b []byte) error {
return nil
}
func (v StructWithPtrsView) Value() *StructWithoutPtrs {
if v.ж.Value == nil {
return nil
}
x := *v.ж.Value
return &x
}
func (v StructWithPtrsView) Value() StructWithoutPtrsView { return v.ж.Value.View() }
func (v StructWithPtrsView) Int() views.ValuePointer[int] { return views.ValuePointerOf(v.ж.Int) }
func (v StructWithPtrsView) Int() *int {
if v.ж.Int == nil {
return nil
}
x := *v.ж.Int
return &x
func (v StructWithPtrsView) NoView() views.ValuePointer[StructWithNoView] {
return views.ValuePointerOf(v.ж.NoView)
}
func (v StructWithPtrsView) NoCloneValue() *StructWithoutPtrs { return v.ж.NoCloneValue }
@@ -85,6 +76,7 @@ func (v StructWithPtrsView) Equal(v2 StructWithPtrsView) bool { return v.ж.Equa
var _StructWithPtrsViewNeedsRegeneration = StructWithPtrs(struct {
Value *StructWithoutPtrs
Int *int
NoView *StructWithNoView
NoCloneValue *StructWithoutPtrs
}{})
@@ -424,12 +416,8 @@ func (v *GenericIntStructView[T]) UnmarshalJSON(b []byte) error {
}
func (v GenericIntStructView[T]) Value() T { return v.ж.Value }
func (v GenericIntStructView[T]) Pointer() *T {
if v.ж.Pointer == nil {
return nil
}
x := *v.ж.Pointer
return &x
func (v GenericIntStructView[T]) Pointer() views.ValuePointer[T] {
return views.ValuePointerOf(v.ж.Pointer)
}
func (v GenericIntStructView[T]) Slice() views.Slice[T] { return views.SliceOf(v.ж.Slice) }
@@ -500,12 +488,8 @@ func (v *GenericNoPtrsStructView[T]) UnmarshalJSON(b []byte) error {
}
func (v GenericNoPtrsStructView[T]) Value() T { return v.ж.Value }
func (v GenericNoPtrsStructView[T]) Pointer() *T {
if v.ж.Pointer == nil {
return nil
}
x := *v.ж.Pointer
return &x
func (v GenericNoPtrsStructView[T]) Pointer() views.ValuePointer[T] {
return views.ValuePointerOf(v.ж.Pointer)
}
func (v GenericNoPtrsStructView[T]) Slice() views.Slice[T] { return views.SliceOf(v.ж.Slice) }
@@ -722,19 +706,14 @@ func (v *StructWithTypeAliasFieldsView) UnmarshalJSON(b []byte) error {
return nil
}
func (v StructWithTypeAliasFieldsView) WithPtr() StructWithPtrsView { return v.ж.WithPtr.View() }
func (v StructWithTypeAliasFieldsView) WithPtr() StructWithPtrsAliasView { return v.ж.WithPtr.View() }
func (v StructWithTypeAliasFieldsView) WithoutPtr() StructWithoutPtrsAlias { return v.ж.WithoutPtr }
func (v StructWithTypeAliasFieldsView) WithPtrByPtr() StructWithPtrsAliasView {
return v.ж.WithPtrByPtr.View()
}
func (v StructWithTypeAliasFieldsView) WithoutPtrByPtr() *StructWithoutPtrsAlias {
if v.ж.WithoutPtrByPtr == nil {
return nil
}
x := *v.ж.WithoutPtrByPtr
return &x
func (v StructWithTypeAliasFieldsView) WithoutPtrByPtr() StructWithoutPtrsAliasView {
return v.ж.WithoutPtrByPtr.View()
}
func (v StructWithTypeAliasFieldsView) SliceWithPtrs() views.SliceView[*StructWithPtrsAlias, StructWithPtrsAliasView] {
return views.SliceOfViews[*StructWithPtrsAlias, StructWithPtrsAliasView](v.ж.SliceWithPtrs)
}

72
cmd/viewer/viewer.go
View File

@@ -79,13 +79,7 @@ func (v *{{.ViewName}}{{.TypeParamNames}}) UnmarshalJSON(b []byte) error {
{{end}}
{{define "makeViewField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldViewName}} { return {{.MakeViewFnName}}(&v.ж.{{.FieldName}}) }
{{end}}
{{define "valuePointerField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldType}} {
if v.ж.{{.FieldName}} == nil {
return nil
}
x := *v.ж.{{.FieldName}}
return &x
}
{{define "valuePointerField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() views.ValuePointer[{{.FieldType}}] { return views.ValuePointerOf(v.ж.{{.FieldName}}) }
{{end}}
{{define "mapField"}}
@@ -126,7 +120,7 @@ func requiresCloning(t types.Type) (shallow, deep bool, base types.Type) {
return p, p, t
}
func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, thisPkg *types.Package) {
func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, _ *types.Package) {
t, ok := typ.Underlying().(*types.Struct)
if !ok || codegen.IsViewType(t) {
return
@@ -354,10 +348,32 @@ func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, thi
} else {
writeTemplate("unsupportedField")
}
} else {
args.FieldType = it.QualifiedName(ptr)
writeTemplate("valuePointerField")
continue
}
// If a view type is already defined for the base type, use it as the field's view type.
if viewType := viewTypeForValueType(base); viewType != nil {
args.FieldType = it.QualifiedName(base)
args.FieldViewName = it.QualifiedName(viewType)
writeTemplate("viewField")
continue
}
// Otherwise, if the unaliased base type is a named type whose view type will be generated by this viewer invocation,
// append the "View" suffix to the unaliased base type name and use it as the field's view type.
if base, ok := types.Unalias(base).(*types.Named); ok && slices.Contains(typeNames, it.QualifiedName(base)) {
baseTypeName := it.QualifiedName(base)
args.FieldType = baseTypeName
args.FieldViewName = appendNameSuffix(args.FieldType, "View")
writeTemplate("viewField")
continue
}
// Otherwise, if the base type does not require deep cloning, has no existing view type,
// and will not have a generated view type, use views.ValuePointer[T] as the field's view type.
// Its Get/GetOk methods return stack-allocated shallow copies of the field's value.
args.FieldType = it.QualifiedName(base)
writeTemplate("valuePointerField")
continue
case *types.Interface:
// If fieldType is an interface with a "View() {ViewType}" method, it can be used to clone the field.
@@ -405,6 +421,33 @@ func appendNameSuffix(name, suffix string) string {
return name + suffix
}
func typeNameOf(typ types.Type) (name *types.TypeName, ok bool) {
switch t := typ.(type) {
case *types.Alias:
return t.Obj(), true
case *types.Named:
return t.Obj(), true
default:
return nil, false
}
}
func lookupViewType(typ types.Type) types.Type {
for {
if typeName, ok := typeNameOf(typ); ok && typeName.Pkg() != nil {
if viewTypeObj := typeName.Pkg().Scope().Lookup(typeName.Name() + "View"); viewTypeObj != nil {
return viewTypeObj.Type()
}
}
switch alias := typ.(type) {
case *types.Alias:
typ = alias.Rhs()
default:
return nil
}
}
}
func viewTypeForValueType(typ types.Type) types.Type {
if ptr, ok := typ.(*types.Pointer); ok {
return viewTypeForValueType(ptr.Elem())
@@ -417,7 +460,12 @@ func viewTypeForValueType(typ types.Type) types.Type {
if !ok || sig.Results().Len() != 1 {
return nil
}
return sig.Results().At(0).Type()
viewType := sig.Results().At(0).Type()
// Check if the typ's package defines an alias for the view type, and use it if so.
if viewTypeAlias, ok := lookupViewType(typ).(*types.Alias); ok && types.AssignableTo(viewType, viewTypeAlias) {
viewType = viewTypeAlias
}
return viewType
}
func viewTypeForContainerType(typ types.Type) (*types.Named, *types.Func) {