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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
// Package binstruct implements simple struct-tag-based conversion
// between Go structures and binary on-disk representations of that
// data.
package binstruct
import (
"encoding/binary"
"errors"
"fmt"
"reflect"
"git.lukeshu.com/btrfs-progs-ng/lib/binstruct/binutil"
)
type Unmarshaler interface {
UnmarshalBinary([]byte) (int, error)
}
func Unmarshal(dat []byte, dstPtr any) (int, error) {
if unmar, ok := dstPtr.(Unmarshaler); ok {
n, err := unmar.UnmarshalBinary(dat)
if err != nil {
err = &UnmarshalError{
Type: reflect.TypeOf(dstPtr),
Method: "UnmarshalBinary",
Err: err,
}
}
return n, err
}
return UnmarshalWithoutInterface(dat, dstPtr)
}
// unmarshal is like Unmarshal, but for internal use to avoid some
// slow round-tripping between `any` and `reflect.Value`.
func unmarshal(dat []byte, dst reflect.Value, isUnmarshaler bool) (int, error) {
if isUnmarshaler {
n, err := dst.Addr().Interface().(Unmarshaler).UnmarshalBinary(dat)
if err != nil {
err = &UnmarshalError{
Type: reflect.PtrTo(dst.Type()),
Method: "UnmarshalBinary",
Err: err,
}
}
return n, err
}
return unmarshalWithoutInterface(dat, dst)
}
func UnmarshalWithoutInterface(dat []byte, dstPtr any) (int, error) {
_dstPtr := reflect.ValueOf(dstPtr)
if _dstPtr.Kind() != reflect.Ptr {
panic(&InvalidTypeError{
Type: _dstPtr.Type(),
Err: errors.New("not a pointer"),
})
}
return unmarshalWithoutInterface(dat, _dstPtr.Elem())
}
func unmarshalWithoutInterface(dat []byte, dst reflect.Value) (int, error) {
switch dst.Kind() {
case reflect.Uint8:
if err := binutil.NeedNBytes(dat, sizeof8); err != nil {
return 0, err
}
dst.SetUint(uint64(dat[0]))
return sizeof8, nil
case reflect.Int8:
if err := binutil.NeedNBytes(dat, sizeof8); err != nil {
return 0, err
}
dst.SetInt(int64(dat[0]))
return sizeof8, nil
case reflect.Uint16:
if err := binutil.NeedNBytes(dat, sizeof16); err != nil {
return 0, err
}
dst.SetUint(uint64(binary.LittleEndian.Uint16(dat[:sizeof16])))
return sizeof16, nil
case reflect.Int16:
if err := binutil.NeedNBytes(dat, sizeof16); err != nil {
return 0, err
}
dst.SetInt(int64(binary.LittleEndian.Uint16(dat[:sizeof16])))
return sizeof16, nil
case reflect.Uint32:
if err := binutil.NeedNBytes(dat, sizeof32); err != nil {
return 0, err
}
dst.SetUint(uint64(binary.LittleEndian.Uint32(dat[:sizeof32])))
return sizeof32, nil
case reflect.Int32:
if err := binutil.NeedNBytes(dat, sizeof32); err != nil {
return 0, err
}
dst.SetInt(int64(binary.LittleEndian.Uint32(dat[:sizeof32])))
return sizeof32, nil
case reflect.Uint64:
if err := binutil.NeedNBytes(dat, sizeof64); err != nil {
return 0, err
}
dst.SetUint(binary.LittleEndian.Uint64(dat[:sizeof64]))
return sizeof64, nil
case reflect.Int64:
if err := binutil.NeedNBytes(dat, sizeof64); err != nil {
return 0, err
}
dst.SetInt(int64(binary.LittleEndian.Uint64(dat[:sizeof64])))
return sizeof64, nil
case reflect.Ptr:
typ := dst.Type()
elemPtr := reflect.New(typ.Elem())
n, err := unmarshal(dat, elemPtr.Elem(), typ.Implements(unmarshalerType))
dst.SetPointer(elemPtr.UnsafePointer())
return n, err
case reflect.Array:
isUnmarshaler := dst.Type().Elem().Implements(unmarshalerType)
var n int
for i := 0; i < dst.Len(); i++ {
_n, err := unmarshal(dat[n:], dst.Index(i), isUnmarshaler)
n += _n
if err != nil {
return n, err
}
}
return n, nil
case reflect.Struct:
return getStructHandler(dst.Type()).Unmarshal(dat, dst)
default:
panic(&InvalidTypeError{
Type: reflect.PtrTo(dst.Type()),
Err: fmt.Errorf("does not implement binfmt.Unmarshaler and kind=%v is not a supported statically-sized kind",
dst.Kind()),
})
}
}
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