go中struct和[]byte互相转换

binary 包处理二进制

读取将r中的结构化二进制数据读入数据。数据必须是指向固定大小值或固定大小值切片的指针。从r读取的字节使用指定的字节顺序进行解码，并写入数据的连续字段。当解码布尔值时，零字节被解码为假，并且任何其他非零字节被解码为真。读入结构时，将跳过具有空白（_）字段名称的字段的字段数据; 即，空白字段名称可用于填充。读入结构时，必须导出所有非空白字段，否则“读取”可能会出现混乱。

但是这种只能使用固定大小类型的数据，变长数据就会异常，例如string, slice 等

package main

import (
	"bytes"
	"encoding/binary"
	"fmt"
)

type T struct {
	A int64
	B float64
}

func main() {
	// Create a struct and write it.
	t := T{A: 0xEEFFEEFF, B: 3.14}
	buf := &bytes.Buffer{}
	err := binary.Write(buf, binary.BigEndian, t)
	if err != nil {
		panic(err)
	}
	fmt.Println(buf.Bytes())

	// Read into an empty struct.
	t = T{}
	err = binary.Read(buf, binary.BigEndian, &t)
	if err != nil {
		panic(err)
	}
	fmt.Printf("%x %f", t.A, t.B)
}

unsafe 包处理二进制

使用 unsafe 包

ByteToStruct

package main


import (
	"fmt"
	"unsafe"
)
type TestStructTobytes struct {
	data int64
}
type SliceMock struct {
	addr uintptr
	len  int
	cap  int
}

func main() {

	var testStruct = &TestStructTobytes{100}
	Len := unsafe.Sizeof(*testStruct)
	testBytes := &SliceMock{
		addr: uintptr(unsafe.Pointer(testStruct)),
		cap:  int(Len),
		len:  int(Len),
	}
	data := *(*[]byte)(unsafe.Pointer(testBytes))
	fmt.Println("[]byte is : ", data)
	var ptestStruct *TestStructTobytes = *(**TestStructTobytes)(unsafe.Pointer(&data))
	fmt.Println("ptestStruct.data is : ", ptestStruct.data)
}

StructToByte

package main

import (
	"fmt"
	"unsafe"
)

type TestStructTobytes struct {
	data int64
}
type SliceMock struct {
	addr uintptr
	len  int
	cap  int
}

func main() {

	var testStruct = &TestStructTobytes{100}
	Len := unsafe.Sizeof(*testStruct)
	testBytes := &SliceMock{
		addr: uintptr(unsafe.Pointer(testStruct)),
		cap:  int(Len),
		len:  int(Len),
	}
	data := *(*[]byte)(unsafe.Pointer(testBytes))
	fmt.Println("[]byte is : ", data)
}

gob 处理二进制

只使用于客户端服务端都使用gob包进行编码和解码的情况。也就是客户端服务端都是go写的，不试用于多种语言。

Gob流不支持函数和通道。试图在最顶层编码这些类型的值会导致失败。结构体中包含函数或者通道类型的字段的话，会视作非导出字段（忽略）处理。

Gob可以编码任意实现了GobEncoder接口或者encoding.BinaryMarshaler接口的类型的值（通过调用对应的方法），GobEncoder接口优先。

Gob可以解码任意实现了GobDecoder接口或者encoding.BinaryUnmarshaler接口的类型的值（通过调用对应的方法），同样GobDecoder接口优先。

package main

import (
	"bytes"
	"encoding/gob"
	"fmt"
)

// A struct with a mix of fields, used for the GOB example.
type complexData struct {
	N int
	S string
	M map[string]int
	P []byte
	C *complexData
	E Addr
}

type Addr struct {
	Comment string
}

func main() {

	testStruct := complexData{
		N: 23,
		S: "string data",
		M: map[string]int{"one": 1, "two": 2, "three": 3},
		P: []byte("abc"),
		C: &complexData{
			N: 256,
			S: "Recursive structs? Piece of cake!",
			M: map[string]int{"01": 1, "10": 2, "11": 3},
			E: Addr{
				Comment: "InnerTest123123123123",
			},
		},
		E: Addr{
			Comment: "Test123123123",
		},
	}

	fmt.Println("Outer complexData struct: ", testStruct)
	fmt.Println("Inner complexData struct: ", testStruct.C)
	fmt.Println("Inner complexData struct: ", testStruct.E)
	fmt.Println("===========================")

	var b bytes.Buffer
	enc := gob.NewEncoder(&b)
	err := enc.Encode(testStruct)
	if err != nil {
		fmt.Println(err)
	}

	dec := gob.NewDecoder(&b)
	var data complexData
	err = dec.Decode(&data)
	if err != nil {
		fmt.Println("Error decoding GOB data:", err)
		return
	}

	fmt.Println("Outer complexData struct: ", data)
	fmt.Println("Inner complexData struct: ", data.C)
	fmt.Println("Inner complexData struct: ", testStruct.E)

}

参考

[译]Go里面的unsafe包详解

来源：oschina

链接：https://my.oschina.net/u/1992048/blog/2998321

标签

gob