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encoding/json: optimize Unmarshal for maps

Browse source 
benchmark                    old ns/op     new ns/op     delta
BenchmarkUnmarshalMap-10     218           172           -21.28%

benchmark                    old allocs     new allocs     delta
BenchmarkUnmarshalMap-10     15             12             -20.00%

benchmark                    old bytes     new bytes     delta
BenchmarkUnmarshalMap-10     328           256           -21.95%

Change-Id: Ie20ab62731c752eb0040c6d1591fedd7d12b1e0c
Reviewed-on: https://go-review.googlesource.com/c/go/+/514100
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
This commit is contained in:
korzhao 2023-07-30 15:02:15 +08:00 committed by Gopher Robot
parent bac4e2f241
commit 1eaeec1095
2 changed files with 22 additions and 7 deletions
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13
src/encoding/json/bench_test.go
View file

@ -385,6 +385,19 @@ func BenchmarkUnmarshalInt64(b *testing.B) {
})
}
func BenchmarkUnmarshalMap(b *testing.B) {
b.ReportAllocs()
data := []byte(`{"key1":"value1","key2":"value2","key3":"value3"}`)
b.RunParallel(func(pb *testing.PB) {
x := make(map[string]string, 3)
for pb.Next() {
if err := Unmarshal(data, &x); err != nil {
b.Fatal("Unmarshal:", err)
}
}
})
}
func BenchmarkIssue10335(b *testing.B) {
b.ReportAllocs()
j := []byte(`{"a":{ }}`)

16
src/encoding/json/decode.go
View file

@ -762,17 +762,17 @@ func (d *decodeState) object(v reflect.Value) error {
if v.Kind() == reflect.Map {
kt := t.Key()
var kv reflect.Value
switch {
case reflect.PointerTo(kt).Implements(textUnmarshalerType):
if reflect.PointerTo(kt).Implements(textUnmarshalerType) {
kv = reflect.New(kt)
if err := d.literalStore(item, kv, true); err != nil {
return err
}
kv = kv.Elem()
case kt.Kind() == reflect.String:
kv = reflect.ValueOf(key).Convert(kt)
default:
} else {
switch kt.Kind() {
case reflect.String:
kv = reflect.New(kt).Elem()
kv.SetString(string(key))
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
s := string(key)
n, err := strconv.ParseInt(s, 10, 64)
@ -780,7 +780,8 @@ func (d *decodeState) object(v reflect.Value) error {
d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: kt, Offset: int64(start + 1)})
break
}
kv = reflect.ValueOf(n).Convert(kt)
kv = reflect.New(kt).Elem()
kv.SetInt(n)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
s := string(key)
n, err := strconv.ParseUint(s, 10, 64)
@ -788,7 +789,8 @@ func (d *decodeState) object(v reflect.Value) error {
d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: kt, Offset: int64(start + 1)})
break
}
kv = reflect.ValueOf(n).Convert(kt)
kv = reflect.New(kt).Elem()
kv.SetUint(n)
default:
panic("json: Unexpected key type") // should never occur
}