避免 string 转 []byte 开销的方式

s2b.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"reflect"
	"unsafe"
)

// s2b converts string to a byte slice without memory allocation.
//
// Note it may break if string and/or slice header will change
// in the future go versions.
func s2b(s string) []byte {
	sh := (*reflect.StringHeader)(unsafe.Pointer(&s))
	bh := reflect.SliceHeader{
		Data: sh.Data,
		Len:  sh.Len,
		Cap:  sh.Len,
	}
	return *(*[]byte)(unsafe.Pointer(&bh))
}

func main() {
	reader := bufio.NewReader(os.Stdin)
	fmt.Print("Enter text: ")
	hello, _ := reader.ReadString('\n')
	fmt.Println(hello)
	helloBytes := s2b(hello)
	helloBytes[1] = 'w'
	fmt.Println(hello)
}