zero_copy.go

package main

import (
	"fmt"
	"unsafe"
)

type StringHeader struct {
	Data uintptr
	Len  int
}
type SliceHeader struct {
	Data uintptr
	Len  int
	Cap  int
}

func string2bytes(s string) []byte {
	//stringHeader := (*reflect.StringHeader)(unsafe.Pointer(&s))
	//bh := reflect.SliceHeader{
	//	Data: stringHeader.Data,
	//	Len:  stringHeader.Len,
	//	Cap:  stringHeader.Len,
	//}
	x := (*[2]uintptr)(unsafe.Pointer(&s))
	h := [3]uintptr{x[0], x[1], x[1]}
	return *(*[]byte)(unsafe.Pointer(&h))
}
func bytes2string(b []byte) string {
	//sliceHeader := (*reflect.SliceHeader)(unsafe.Pointer(&b))
	//sh := reflect.StringHeader{
	//	Data: sliceHeader.Data,
	//	Len:  sliceHeader.Len,
	//}
	return *(*string)(unsafe.Pointer(&b))
}



func main() {
	fmt.Println(string2bytes("hello"))
}

zero_copy_test.go

package main

import (
	"strings"
	"testing"
)

var s = strings.Repeat("a", 1024)

func test() {
	b := []byte(s)
	_ = string(b)
}

func test2() {
	b := string2bytes(s)
	_ = bytes2string(b)
}

func BenchmarkTest(b *testing.B) {
	for i := 0; i < b.N; i++ {
		test()
	}
}

func BenchmarkTestBlock(b *testing.B) {
	for i := 0; i < b.N; i++ {
		test2()
	}
}

//go test -v -bench . -benchmem
//goos: darwin
//goarch: amd64
//BenchmarkTest
//BenchmarkTest-12                 4438213               270 ns/op            2048 B/op          2 allocs/op
//BenchmarkTestBlock
//BenchmarkTestBlock-12           1000000000               0.500 ns/op           0 B/op          0 allocs/op
//PASS