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marshaler.go
129 lines (104 loc) · 2.6 KB
/
marshaler.go
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package binary
import (
"bytes"
"encoding/binary"
"fmt"
"reflect"
)
const (
commandLength = 12
hashLength = 32
magicAndChecksumLength = 4
)
// Marshaler is the interface implemented by types that can marshal themselves into binary.
type Marshaler interface {
MarshalBinary() ([]byte, error)
}
// ensures that littleEndian is used to encode varint value
func MarshalForVarint(i interface{}) ([]byte, error) {
buf := bytes.NewBuffer([]byte{})
switch val := i.(type) {
case uint8, uint16, uint32, uint64:
if err := binary.Write(buf, binary.LittleEndian, val); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
return nil, fmt.Errorf("unsuported varint value type")
}
// Marshal returns the binary encoding of v.
func Marshal(v interface{}) ([]byte, error) {
buf := bytes.NewBuffer([]byte{})
if reflect.TypeOf(v).Kind() == reflect.Ptr {
v = reflect.ValueOf(v).Elem().Interface()
}
switch val := v.(type) {
case uint8, int32, uint32, int64, uint64, bool:
if err := binary.Write(buf, binary.LittleEndian, val); err != nil {
return nil, err
}
// port
case uint16:
if err := binary.Write(buf, binary.BigEndian, val); err != nil {
return nil, err
}
case [magicAndChecksumLength]byte:
if _, err := buf.Write(val[:]); err != nil {
return nil, err
}
case [commandLength]byte:
if _, err := buf.Write(val[:]); err != nil {
return nil, err
}
case [hashLength]byte:
if _, err := buf.Write(val[:]); err != nil {
return nil, err
}
case []byte:
if _, err := buf.Write(val); err != nil {
return nil, err
}
// VarStr.String
case string:
if _, err := buf.Write([]byte(val)); err != nil {
return nil, err
}
case Marshaler:
b, err := val.MarshalBinary()
if err != nil {
return nil, err
}
if _, err := buf.Write(b); err != nil {
return nil, err
}
default:
// is it a struct?
if reflect.ValueOf(v).Kind() == reflect.Struct {
b, err := marshalStruct(v)
if err != nil {
return nil, err
}
if _, err := buf.Write(b); err != nil {
return nil, err
}
break
}
return nil, fmt.Errorf("unsupported type %s", reflect.TypeOf(v).String())
}
return buf.Bytes(), nil
}
func marshalStruct(v interface{}) ([]byte, error) {
buf := bytes.NewBuffer([]byte{})
vv := reflect.ValueOf(v)
for i := 0; i < vv.NumField(); i++ {
s, err := Marshal(reflect.Indirect(vv.Field(i)).Interface())
if err != nil {
f := reflect.TypeOf(v).Field(i).Name
return nil, fmt.Errorf("failed to marshal field %s: %v", f, err)
}
if _, err := buf.Write(s); err != nil {
return nil, err
}
}
return buf.Bytes(), nil
}