It seems that go 1.22 has optimized the implementation of string to byte
slicing and no longer requires memory allocation.
But why not optimize byte slicing to string conversion together?
```go
package main
import (
"reflect"
"testing"
"unsafe"
)
func BenchmarkString(b *testing.B) {
byteSli := []byte{123, 34, 100, 101, 102, 97, 117, 108, 116, 34, 58, 123,
34, 99, 111, 109, 109, 111, 110, 34, 58, 123, 34, 112, 101, 116, 34, 58,
123, 34, 102, 105, 118, 101, 34, 58, 34, 230, 150, 145, 230, 150, 145, 34,
44, 34, 102, 111, 117, 114, 34, 58, 34, 231, 154, 174, 231, 147, 156, 231,
147, 156, 34, 44, 34, 111, 110, 101, 34, 58, 34, 229, 188, 165, 229, 188,
165, 230, 135, 181, 34, 44, 34, 116, 104, 114, 101, 101, 34, 58, 34, 229,
145, 134, 229, 145, 134, 34, 44, 34, 116, 119, 111, 34, 58, 34, 233, 187,
132, 230, 169, 153, 230, 169, 153, 34, 125, 44, 34, 114, 101, 108, 97, 116,
105, 111, 110, 34, 58, 123, 34, 102, 97, 116, 104, 101, 114, 34, 58, 34,
99, 117, 105, 120, 120, 120, 120, 120, 120, 120, 34, 44, 34, 109, 111, 116,
104, 101, 114, 34, 58, 34, 121, 105, 110, 120, 120, 120, 120, 120, 34, 44,
34, 119, 105, 102, 101, 34, 58, 34, 112, 101, 110, 103, 120, 120, 34, 125,
125, 125, 125}
_ = string(byteSli)
}
func BenchmarkUnsafe(b *testing.B) {
byteSli := []byte{123, 34, 100, 101, 102, 97, 117, 108, 116, 34, 58, 123,
34, 99, 111, 109, 109, 111, 110, 34, 58, 123, 34, 112, 101, 116, 34, 58,
123, 34, 102, 105, 118, 101, 34, 58, 34, 230, 150, 145, 230, 150, 145, 34,
44, 34, 102, 111, 117, 114, 34, 58, 34, 231, 154, 174, 231, 147, 156, 231,
147, 156, 34, 44, 34, 111, 110, 101, 34, 58, 34, 229, 188, 165, 229, 188,
165, 230, 135, 181, 34, 44, 34, 116, 104, 114, 101, 101, 34, 58, 34, 229,
145, 134, 229, 145, 134, 34, 44, 34, 116, 119, 111, 34, 58, 34, 233, 187,
132, 230, 169, 153, 230, 169, 153, 34, 125, 44, 34, 114, 101, 108, 97, 116,
105, 111, 110, 34, 58, 123, 34, 102, 97, 116, 104, 101, 114, 34, 58, 34,
99, 117, 105, 120, 120, 120, 120, 120, 120, 120, 34, 44, 34, 109, 111, 116,
104, 101, 114, 34, 58, 34, 121, 105, 110, 120, 120, 120, 120, 120, 34, 44,
34, 119, 105, 102, 101, 34, 58, 34, 112, 101, 110, 103, 120, 120, 34, 125,
125, 125, 125}
_ = *(*string)(unsafe.Pointer(&byteSli))
}
func BenchmarkByteStyle(b *testing.B) {
str :=
`{"default":{"common":{"pet":{"five":"aa","four":"bb","one":"cc","three":"dd","two":"黄ee"},"relation":{"father":"ff","mother":"mm","wife":"ww"}}}}`
_ = []byte(str)
}
func BenchmarkWithUnsafe(b *testing.B) {
str
:=
`{"default":{"common":{"pet":{"five":"aa","four":"bb","one":"cc","three":"dd","two":"黄ee"},"relation":{"father":"ff","mother":"mm","wife":"ww"}}}}`
sh := (*reflect.StringHeader)(unsafe.Pointer(&str))
bh := reflect.SliceHeader{
Data: sh.Data,
Len: sh.Len,
Cap: sh.Len,
}
_ = *(*[]byte)(unsafe.Pointer(&bh))
}
```
```bench_test.go
package main
import (
"testing"
)
func BenchmarkTest1(b *testing.B) {
for i := 0; i < b.N; i++ {
BenchmarkString(b)
}
}
func BenchmarkTest2(b *testing.B) {
for i := 0; i < b.N; i++ {
BenchmarkUnsafe(b)
}
}
func BenchmarkTest3(b *testing.B) {
for i := 0; i < b.N; i++ {
BenchmarkByteStyle(b)
}
}
func BenchmarkTest4(b *testing.B) {
for i := 0; i < b.N; i++ {
BenchmarkWithUnsafe(b)
}
}
```
when go version is 1.21
```shell
go version
go version go1.21.0 darwin/arm64
goos: darwin
goarch: arm64
pkg: bc
BenchmarkTest1-8 37078008 32.45 ns/op 192
B/op 1 allocs/op
BenchmarkTest2-8 144106840 9.181 ns/op 0
B/op 0 allocs/op
BenchmarkTest3-8 38973375 28.94 ns/op 192
B/op 1 allocs/op
BenchmarkTest4-8 1000000000 0.3130 ns/op 0
B/op 0 allocs/op
PASS
ok bc 6.038s
```
when go version is 1.22
```shell
go version
go version devel go1.22-631a6c2abf Fri Nov 17 23:34:11 2023 +0000
darwin/arm64
go test -test.bench=".*" -benchmem
goos: darwin
goarch: arm64
pkg: bc
BenchmarkTest1-8 35727334 33.51 ns/op 192
B/op 1 allocs/op
BenchmarkTest2-8 147172425 8.157 ns/op 0
B/op 0 allocs/op
BenchmarkTest3-8 1000000000 0.3136 ns/op 0
B/op 0 allocs/op
BenchmarkTest4-8 1000000000 0.3153 ns/op 0
B/op 0 allocs/op
PASS
ok bc 5.095s
```
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