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marshal.go
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marshal.go
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package typemarshal
import (
"encoding/json"
"errors"
"reflect"
)
type typeValue struct {
T string `json:"t"`
V json.RawMessage `json:"v"`
}
type Marshaler func(v interface{}) ([]byte, error)
type Unmarshaler func(data []byte) (interface{}, error)
type encoder struct {
Marshal Marshaler
Unmarshal Unmarshaler
}
var (
typeToName = map[reflect.Type]string{nil: "nil"}
nameToType = map[string]reflect.Type{}
encoders = map[string]encoder{"nil": encoder{nilMarshaler, nilUnmarshaler}}
)
func Register(name string, typ reflect.Type) error {
return RegisterCustom(name, typ, DefaultMarshaler, TypeUnmarshalerOf(typ))
}
func RegisterCustom(name string, typ reflect.Type, marshal Marshaler, unmarshal Unmarshaler) error {
if name == "" {
return errors.New("Missing name")
}
if typ == nil {
name = "nil"
}
typeToName[typ] = name
nameToType[name] = typ
encoders[name] = encoder{marshal, unmarshal}
return nil
}
func Marshal(v interface{}) ([]byte, error) {
typ := reflect.TypeOf(v)
name, ok := typeToName[typ]
if !ok {
return nil, errors.New("Not found type name")
}
enc, ok := encoders[name]
if !ok {
return nil, errors.New("Not found marshaler")
}
data, err := enc.Marshal(v)
if err != nil {
return nil, err
}
return json.Marshal(&typeValue{name, json.RawMessage(data)})
}
func Unmarshal(data []byte) (interface{}, error) {
var tv typeValue
err := json.Unmarshal(data, &tv)
if err != nil {
return nil, err
}
enc, ok := encoders[tv.T]
if !ok {
return nil, errors.New("Not found marshaler")
}
return enc.Unmarshal([]byte(tv.V))
}
func DefaultMarshaler(v interface{}) ([]byte, error) {
return json.Marshal(v)
}
func TypeUnmarshalerOf(typ reflect.Type) Unmarshaler {
return func(data []byte) (interface{}, error) {
v := reflect.New(typ)
err := json.Unmarshal(data, v.Interface())
if err != nil {
return nil, err
}
return v.Elem().Interface(), nil
}
}
func nilMarshaler(v interface{}) ([]byte, error) {
return []byte("null"), nil
}
func nilUnmarshaler(data []byte) (interface{}, error) {
if string(data) != "null" {
return nil, errors.New("Nil unmarshaler error")
}
return nil, nil
}