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use sync.OnceFunc instead of sync.Once
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sync.OnceFunc was added in Go 1.21 and simplifies the code slightly.
Worth noting that, compared to Once, OnceFunc does a bit more work
as it replays any panic that happens on the first call:

    goos: linux
    goarch: amd64
    pkg: github.com/go-json-experiment/json
    cpu: AMD Ryzen 7 PRO 5850U with Radeon Graphics
                                                  │     old     │                new                │
                                                  │   sec/op    │   sec/op     vs base              │
    Testdata/CanadaGeometry/Marshal/Concrete-8      1.311m ± 0%   1.339m ± 0%  +2.17% (p=0.002 n=6)
    Testdata/CanadaGeometry/Marshal/Interface-8     1.347m ± 1%   1.434m ± 0%  +6.46% (p=0.002 n=6)
    Testdata/CanadaGeometry/Unmarshal/Concrete-8    1.832m ± 0%   1.867m ± 0%  +1.92% (p=0.002 n=6)
    Testdata/CanadaGeometry/Unmarshal/Interface-8   2.962m ± 0%   2.827m ± 1%  -4.54% (p=0.002 n=6)
    geomean                                         1.759m        1.785m       +1.43%
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@mvdan
mvdan committed Apr 2, 2024
1 parent 908677b commit 2449b35
Showing 1 changed file with 23 additions and 34 deletions.
57 changes: 23 additions & 34 deletions arshal_default.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -612,14 +612,13 @@ func makeMapArshaler(t reflect.Type) *arshaler {

var fncs arshaler
var (
once sync.Once
keyFncs *arshaler
valFncs *arshaler
)
init := func() {
initOnce := sync.OnceFunc(func() {
keyFncs = lookupArshaler(t.Key())
valFncs = lookupArshaler(t.Elem())
}
})
fncs.marshal = func(enc *jsontext.Encoder, va addressableValue, mo *jsonopts.Struct) error {
// Check for cycles.
xe := export.Encoder(enc)
Expand Down Expand Up @@ -661,7 +660,7 @@ func makeMapArshaler(t reflect.Type) *arshaler {
}
}

once.Do(init)
initOnce()
if err := enc.WriteToken(jsontext.ObjectStart); err != nil {
return err
}
Expand Down Expand Up @@ -792,7 +791,7 @@ func makeMapArshaler(t reflect.Type) *arshaler {
va.SetZero()
return nil
case '{':
once.Do(init)
initOnce()
if va.IsNil() {
va.Set(reflect.MakeMap(t))
}
Expand Down Expand Up @@ -900,19 +899,18 @@ func makeStructArshaler(t reflect.Type) *arshaler {

var fncs arshaler
var (
once sync.Once
fields structFields
errInit *SemanticError
)
init := func() {
initOnce := sync.OnceFunc(func() {
fields, errInit = makeStructFields(t)
}
})
fncs.marshal = func(enc *jsontext.Encoder, va addressableValue, mo *jsonopts.Struct) error {
xe := export.Encoder(enc)
if mo.Format != "" && mo.FormatDepth == xe.Tokens.Depth() {
return newInvalidFormatError("marshal", t, mo.Format)
}
once.Do(init)
initOnce()
if errInit != nil {
err := *errInit // shallow copy SemanticError
err.action = "marshal"
Expand Down Expand Up @@ -1080,7 +1078,7 @@ func makeStructArshaler(t reflect.Type) *arshaler {
va.SetZero()
return nil
case '{':
once.Do(init)
initOnce()
if errInit != nil {
err := *errInit // shallow copy SemanticError
err.action = "unmarshal"
Expand Down Expand Up @@ -1214,13 +1212,10 @@ func isLegacyEmpty(v addressableValue) bool {

func makeSliceArshaler(t reflect.Type) *arshaler {
var fncs arshaler
var (
once sync.Once
valFncs *arshaler
)
init := func() {
var valFncs *arshaler
initOnce := sync.OnceFunc(func() {
valFncs = lookupArshaler(t.Elem())
}
})
fncs.marshal = func(enc *jsontext.Encoder, va addressableValue, mo *jsonopts.Struct) error {
// Check for cycles.
xe := export.Encoder(enc)
Expand Down Expand Up @@ -1262,7 +1257,7 @@ func makeSliceArshaler(t reflect.Type) *arshaler {
}
}

once.Do(init)
initOnce()
if err := enc.WriteToken(jsontext.ArrayStart); err != nil {
return err
}
Expand Down Expand Up @@ -1303,7 +1298,7 @@ func makeSliceArshaler(t reflect.Type) *arshaler {
va.SetZero()
return nil
case '[':
once.Do(init)
initOnce()
unmarshal := valFncs.unmarshal
if uo.Unmarshalers != nil {
unmarshal, _ = uo.Unmarshalers.(*Unmarshalers).lookup(unmarshal, t.Elem())
Expand Down Expand Up @@ -1348,20 +1343,17 @@ func makeSliceArshaler(t reflect.Type) *arshaler {

func makeArrayArshaler(t reflect.Type) *arshaler {
var fncs arshaler
var (
once sync.Once
valFncs *arshaler
)
init := func() {
var valFncs *arshaler
initOnce := sync.OnceFunc(func() {
valFncs = lookupArshaler(t.Elem())
}
})
n := t.Len()
fncs.marshal = func(enc *jsontext.Encoder, va addressableValue, mo *jsonopts.Struct) error {
xe := export.Encoder(enc)
if mo.Format != "" && mo.FormatDepth == xe.Tokens.Depth() {
return newInvalidFormatError("marshal", t, mo.Format)
}
once.Do(init)
initOnce()
if err := enc.WriteToken(jsontext.ArrayStart); err != nil {
return err
}
Expand Down Expand Up @@ -1395,7 +1387,7 @@ func makeArrayArshaler(t reflect.Type) *arshaler {
va.SetZero()
return nil
case '[':
once.Do(init)
initOnce()
unmarshal := valFncs.unmarshal
if uo.Unmarshalers != nil {
unmarshal, _ = uo.Unmarshalers.(*Unmarshalers).lookup(unmarshal, t.Elem())
Expand Down Expand Up @@ -1441,13 +1433,10 @@ func makeArrayArshaler(t reflect.Type) *arshaler {

func makePointerArshaler(t reflect.Type) *arshaler {
var fncs arshaler
var (
once sync.Once
valFncs *arshaler
)
init := func() {
var valFncs *arshaler
initOnce := sync.OnceFunc(func() {
valFncs = lookupArshaler(t.Elem())
}
})
fncs.marshal = func(enc *jsontext.Encoder, va addressableValue, mo *jsonopts.Struct) error {
// Check for cycles.
xe := export.Encoder(enc)
Expand All @@ -1462,7 +1451,7 @@ func makePointerArshaler(t reflect.Type) *arshaler {
if va.IsNil() {
return enc.WriteToken(jsontext.Null)
}
once.Do(init)
initOnce()
marshal := valFncs.marshal
if mo.Marshalers != nil {
marshal, _ = mo.Marshalers.(*Marshalers).lookup(marshal, t.Elem())
Expand All @@ -1479,7 +1468,7 @@ func makePointerArshaler(t reflect.Type) *arshaler {
va.SetZero()
return nil
}
once.Do(init)
initOnce()
unmarshal := valFncs.unmarshal
if uo.Unmarshalers != nil {
unmarshal, _ = uo.Unmarshalers.(*Unmarshalers).lookup(unmarshal, t.Elem())
Expand Down

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