go 的结构体极速序列化

序列化有很多种方式，最简单的就是gob，但是最慢，如果我们使用bigCache之类的库，则需要自己做序列化以及反序列化，

高并发环境下还是很重要的，各种对比参考：

我这里要使用就是最直接的序列化，按照小端直接写到字节流，网上很多的例子都是这样的：

type Counter struct {
	Count     uint64
	LastCount uint64
}
 
func Counter2Buf(c Counter) []byte {
	buf := bytes.NewBuffer([]byte{})
	buf.Grow(16)
	binary.Write(buf, binary.LittleEndian, c.Count)
	binary.Write(buf, binary.LittleEndian, c.LastCount)
	return buf.Bytes()
}
 
func Buf2Counter(b []byte) (*Counter, error) {
	if len(b) < 16 {
		return nil, fmt.Errorf("len is too short")
	}
 
	c := Counter{0, 0}
	bytesBuffer := bytes.NewBuffer(b)
	binary.Read(bytesBuffer, binary.LittleEndian, &c.Count)
	binary.Read(bytesBuffer, binary.LittleEndian, &c.LastCount)
 
	return &c, nil
}

而实际上性能依然很差，比protobuf还要差，比如我需要做100万次操作，结果如下：

编码：106 ms

解码：86 ms

对应的1单次操作平均：116ms和86ms，protobuf压缩也不过如此，

其实这里还可以更快，直接操作[]byte,

// 这里按照系统库的方式抄一下，直接添加一个偏移就可以了
func putUint64Little(b []byte, v uint64, off int) {
	b[0+off] = byte(v)
	b[1+off] = byte(v >> 8)
	b[2+off] = byte(v >> 16)
	b[3+off] = byte(v >> 24)
	b[4+off] = byte(v >> 32)
	b[5+off] = byte(v >> 40)
	b[6+off] = byte(v >> 48)
	b[7+off] = byte(v >> 56)
}
 
func Couter2Bytes(c Counter) []byte {
	buff := make([]byte, 16)
	binary.LittleEndian.PutUint64(buff, c.Count)
	putUint64Little(buff, c.LastCount, 8)
	return buff
 
}
 
///
// 这里按照系统库的方式抄一下，直接添加一个偏移就可以了
func Uint64Litter(b []byte, off int) uint64 {
	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
	return uint64(b[0+off]) | uint64(b[1+off])<<8 | uint64(b[2+off])<<16 | uint64(b[3+off])<<24 |
		uint64(b[4+off])<<32 | uint64(b[5+off])<<40 | uint64(b[6+off])<<48 | uint64(b[7+off])<<56
}
 
// 字节转换成整形
func BytesToCounter(b []byte) (*Counter, error) {
	if len(b) < 16 {
		return nil, fmt.Errorf("len is too short")
	}
	c := Counter{binary.LittleEndian.Uint64(b),
		Uint64Litter(b, 8)}
 
	return &c, nil
}

这时候，我们执行测试100万次编码测试，

编码：19 ms

解码： 18ms

平均单次耗时：编码19ns，解码18ns

整体性能提高了5倍；

后记：有人做过相关对比测试：go语言序列化json/gob/msgp/protobuf性能对比 - 知乎

对比帖子中的性能测试，我们直接做一个写测试：

type Doc struct {
	Doc_id       uint32 // 4B
	School_level uint32
	Active       uint32
	Work_age     uint32
 
	Vip  bool // 1B
	Chat bool
 
	Position string // 4B + bytes
	Company  string
	City     string
}
 
func Doc2Bytes(doc *Doc) []byte {
	length := 16 + 2 + 12 + len(doc.Position) + len(doc.Company) + len(doc.City)
	buf := make([]byte, length)
	putUint32Little(buf, 0, doc.Doc_id)
	putUint32Little(buf, 4, doc.School_level)
	putUint32Little(buf, 8, doc.Active)
	putUint32Little(buf, 12, doc.Work_age)
 
	putBool(buf, 16, doc.Vip)
	putBool(buf, 17, doc.Chat)
 
	off := putString(buf, 18, doc.Position)
	off = putString(buf, off, doc.Company)
	putString(buf, off, doc.City)
	return buf
}
 
func DocFromByte(b []byte) *Doc {
	doc := Doc{
		Doc_id:       0,
		School_level: 0,
		Active:       0,
		Work_age:     0,
		Vip:          false,
		Chat:         false,
		Position:     "",
		Company:      "",
		City:         "",
	}
	doc.Doc_id = Uint32Little(b, 0)
	doc.School_level = Uint32Little(b, 4)
	doc.Active = Uint32Little(b, 8)
	doc.Work_age = Uint32Little(b, 12)
	doc.Vip = BoolLitter(b, 16)
	doc.Chat = BoolLitter(b, 17)
	var off int = 0
	doc.Position, off = StringLittle(b, 18)
	doc.Company, off = StringLittle(b, off)
	doc.City, off = StringLittle(b, off)
 
	return &doc
}
 
func putUint32Little(b []byte, off int, v uint32) {
	// 这样比指针更快些，
	b[0+off] = byte(v)
	b[1+off] = byte(v >> 8)
	b[2+off] = byte(v >> 16)
	b[3+off] = byte(v >> 24)
	//pInt := unsafe.Pointer(&v)
	//bInt := (*[4]byte)(pInt)
	//copy(b[off:], (*bInt)[0:])
}
 
func putBool(b []byte, off int, v bool) {
	if v {
		b[0+off] = byte(1)
	} else {
		b[0+off] = byte(0)
	}
 
}
 
func str2bytes(s string) []byte {
	x := (*[2]uintptr)(unsafe.Pointer(&s))
	h := [3]uintptr{x[0], x[1], x[1]}
	return *(*[]byte)(unsafe.Pointer(&h))
}
 
func bytes2str(b []byte) string {
	return *(*string)(unsafe.Pointer(&b))
}
 
func putString(b []byte, off int, v string) int {
	length := uint32(len(v))
	putUint32Little(b, off, length)
 
	off = off + 4
 
	// TODO: 优化这里
	//buf := []byte(v)
	//for i, v := range buf {
	//	b[off+4+i] = v
	//}
	//return off + 4 + len(v)
	// test it
	x := (*[2]uintptr)(unsafe.Pointer(&v))
	h := [3]uintptr{x[0], x[1], x[1]}
	bStr := *(*[]byte)(unsafe.Pointer(&h))
	//bStr := str2bytes(v)
	copy(b[off:], bStr[0:])
	return off + len(v)
}
 
func Uint32Little(b []byte, off int) uint32 {
	return uint32(b[0+off]) | uint32(b[1+off])<<8 | uint32(b[2+off])<<16 | uint32(b[3+off])<<24
}
 
func BoolLitter(b []byte, off int) bool {
	a := int8(b[0+off])
	if a != 0 {
		return true
	}
	return false
}
 
func StringLittle(b []byte, off int) (string, int) {
	length := Uint32Little(b, off)
	bPart := b[off+4 : off+4+int(length)]
	str := bytes2str(bPart)
 
	return str, off + 4 + int(length)
 
}
 
 
 
func testSeri() {
	doc := Doc{1, 2, 3, 4,
		false, true,
		"abcdefg",
		"XXXX",
		"zz",
	}
	b := Doc2Bytes(&doc)
	fmt.Println(b)
	doc1 := DocFromByte(b)
	fmt.Println(doc1)
}

测试结果是平均42ns，比protobuf还要快一点点；