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encoding.go
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encoding.go
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package encoding
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"os"
"reflect"
)
// Endianness interface definition specifies the endianness used to decode
type Endianness binary.ByteOrder
var (
// ErrSeeking error definition
ErrSeeking = errors.New("Error seeking")
// ErrMultipleOffsets error definition
ErrMultipleOffsets = errors.New("Only one offset argument is allowed")
// ErrInvalidNilPointer
ErrInvalidNilPointer = errors.New("Nil pointer is invalid")
// No Pointer interface
ErrNoPointerInterface = errors.New("Interface expect to be a pointer")
)
// Unpack data type from reader object. An optional offset can be specified.
func Unpack(reader io.ReadSeeker, endianness Endianness, data interface{}, offsets ...int64) error {
switch {
// No offset to deal with
case len(offsets) == 0:
if err := binary.Read(reader, endianness, data); err != nil {
return err
}
// An offset to deal with
case len(offsets) == 1:
if soughtOffset, err := reader.Seek(offsets[0], os.SEEK_SET); soughtOffset != offsets[0] || err != nil {
switch {
case err != nil:
return err
case soughtOffset != offsets[0]:
return ErrSeeking
default:
if err := binary.Read(reader, endianness, data); err != nil {
return err
}
}
}
// Error if more than one offset
default:
return ErrMultipleOffsets
}
return nil
}
func marshalArray(data interface{}, endianness Endianness) ([]byte, error) {
var out []byte
val := reflect.ValueOf(data)
if val.IsNil() {
return out, ErrInvalidNilPointer
}
elem := val.Elem()
if elem.Kind() != reflect.Array {
return out, fmt.Errorf("Not an Array structure")
}
for k := 0; k < elem.Len(); k++ {
buff, err := Marshal(elem.Index(k).Addr().Interface(), endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
}
return out, nil
}
func marshalSlice(data interface{}, endianness Endianness) ([]byte, error) {
var out []byte
val := reflect.ValueOf(data)
if val.IsNil() {
return out, ErrInvalidNilPointer
}
elem := val.Elem()
if elem.Kind() != reflect.Slice {
return out, fmt.Errorf("Not a Slice object")
}
s := elem
// We first serialize slice length as a int64
sliceLen := int64(s.Len())
buff, err := Marshal(&sliceLen, endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
for k := 0; k < s.Len(); k++ {
buff, err := Marshal(s.Index(k).Addr().Interface(), endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
}
return out, nil
}
func Marshal(data interface{}, endianness Endianness) ([]byte, error) {
var out []byte
val := reflect.ValueOf(data)
if val.Kind() != reflect.Ptr {
return out, ErrNoPointerInterface
}
if val.IsNil() {
return out, ErrInvalidNilPointer
}
elem := val.Elem()
typ := elem.Type()
switch typ.Kind() {
case reflect.Struct:
for i := 0; i < typ.NumField(); i++ {
tField := typ.Field(i)
// Unmarshal recursively if field of struct is a struct
switch tField.Type.Kind() {
case reflect.Struct:
buff, err := Marshal(elem.Field(i).Addr().Interface(), endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
case reflect.Array:
buff, err := marshalArray(elem.Field(i).Addr().Interface(), endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
case reflect.Slice:
buff, err := marshalSlice(elem.Field(i).Addr().Interface(), endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
default:
buff, err := Marshal(elem.Field(i).Addr().Interface(), endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
}
}
case reflect.Array:
buff, err := marshalArray(elem.Addr().Interface(), endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
case reflect.Slice:
buff, err := marshalSlice(elem.Addr().Interface(), endianness)
if err != nil {
return out, err
}
out = append(out, buff...)
default:
writter := new(bytes.Buffer)
if err := binary.Write(writter, endianness, elem.Interface()); err != nil {
return out, err
}
out = append(out, writter.Bytes()...)
}
return out, nil
}
func UnmarshaInitSlice(reader io.Reader, data interface{}, endianness Endianness) error {
val := reflect.ValueOf(data)
if val.IsNil() {
return ErrInvalidNilPointer
}
slice := val.Elem()
if slice.Kind() != reflect.Slice {
return fmt.Errorf("Not a slice object")
}
if slice.Len() == 0 {
return fmt.Errorf("Not initialized slice")
}
for k := 0; k < slice.Len(); k++ {
err := Unmarshal(reader, slice.Index(k).Addr().Interface(), endianness)
if err != nil {
return err
}
}
return nil
}
func unmarshalArray(reader io.Reader, data interface{}, endianness Endianness) error {
val := reflect.ValueOf(data)
if val.IsNil() {
return ErrInvalidNilPointer
}
array := val.Elem()
if array.Kind() != reflect.Array {
return fmt.Errorf("Not an Array structure")
}
for k := 0; k < array.Len(); k++ {
err := Unmarshal(reader, array.Index(k).Addr().Interface(), endianness)
if err != nil {
return err
}
}
return nil
}
func unmarshalSlice(reader io.Reader, data interface{}, endianness Endianness) error {
var sliceLen int64
val := reflect.ValueOf(data)
if val.IsNil() {
return ErrInvalidNilPointer
}
elem := val.Elem()
if elem.Kind() != reflect.Slice {
return fmt.Errorf("Not a Slice object")
}
err := Unmarshal(reader, &sliceLen, endianness)
if err != nil {
return err
}
s := elem
newS := reflect.MakeSlice(s.Type(), int(sliceLen), int(sliceLen))
s.Set(newS)
//return UnmarshaInitSlice(reader, newS.Interface(), endianness)
for k := 0; k < s.Len(); k++ {
err := Unmarshal(reader, s.Index(k).Addr().Interface(), endianness)
if err != nil {
return err
}
}
return nil
}
func Unmarshal(reader io.Reader, data interface{}, endianness Endianness) error {
val := reflect.ValueOf(data)
if val.IsNil() {
return ErrInvalidNilPointer
}
elem := val.Elem()
typ := elem.Type()
switch typ.Kind() {
case reflect.Struct:
for i := 0; i < typ.NumField(); i++ {
tField := typ.Field(i)
// Unmarshal recursively if field of struct is a struct
switch tField.Type.Kind() {
case reflect.Struct:
err := Unmarshal(reader, elem.Field(i).Addr().Interface(), endianness)
if err != nil {
return err
}
case reflect.Array:
err := unmarshalArray(reader, elem.Field(i).Addr().Interface(), endianness)
if err != nil {
return err
}
case reflect.Slice:
err := unmarshalSlice(reader, elem.Field(i).Addr().Interface(), endianness)
if err != nil {
return err
}
default:
if err := Unmarshal(reader, elem.Field(i).Addr().Interface(), endianness); err != nil {
return err
}
}
}
case reflect.Array:
err := unmarshalArray(reader, elem.Addr().Interface(), endianness)
if err != nil {
return err
}
case reflect.Slice:
err := unmarshalSlice(reader, elem.Addr().Interface(), endianness)
if err != nil {
return err
}
default:
if err := binary.Read(reader, endianness, data); err != nil {
return err
}
}
return nil
}