Go语言阅读小笔记,来自知呼达达关于unsafe.Pointer的分享.

func stringPointer(s string) unsafe.Pointer {
p := (*reflect.StringHeader)(unsafe.Pointer(&s))
return unsafe.Pointer(p.Data)
}

func bytePointer(b []byte) unsafe.Pointer {
p := (*reflect.SliceHeader)(unsafe.Pointer(&b))
return unsafe.Pointer(p.Data)
}

第二式 - 把[]byte转成string

package test

import "testing"
import "unsafe"

func Test_ByteString(t *testing.T) {
var x = []byte("Hello World!")
var y = *(*string)(unsafe.Pointer(&x))
var z = string(x)

if y != z {
t.Fail()
}
}

func Benchmark_Normal(b *testing.B) {
var x = []byte("Hello World!")
for i := 0; i < b.N; i ++ {
_ = string(x)
}
}

func Benchmark_ByteString(b *testing.B) {
var x = []byte("Hello World!")
for i := 0; i < b.N; i ++ {
_ = *(*string)(unsafe.Pointer(&x))
}
}

PASS
Benchmark_Normal    20000000            63.4 ns/op
Benchmark_ByteString    2000000000           0.55 ns/op
ok      github.com/idada/go-labs/labs28 2.486s

第三式 - 结构体和[]byte互转

type MyStruct struct {
A int
B int
}

var sizeOfMyStruct = int(unsafe.Sizeof(MyStruct{}))

func MyStructToBytes(s *MyStruct) []byte {
var x reflect.SliceHeader
x.Len = sizeOfMyStruct
x.Cap = sizeOfMyStruct
x.Data = uintptr(unsafe.Pointer(s))
return *(*[]byte)(unsafe.Pointer(&x))
}

func BytesToMyStruct(b []byte) *MyStruct {
return (*MyStruct)(unsafe.Pointer(
(*reflect.SliceHeader)(unsafe.Pointer(&b)).Data,
))
}