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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package binstruct
import (
"errors"
"fmt"
"reflect"
)
type StaticSizer interface {
BinaryStaticSize() int
}
func StaticSize(obj any) int {
sz, err := staticSize(reflect.TypeOf(obj))
if err != nil {
panic(err)
}
return sz
}
var (
staticSizerType = reflect.TypeOf((*StaticSizer)(nil)).Elem()
marshalerType = reflect.TypeOf((*Marshaler)(nil)).Elem()
unmarshalerType = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
)
const (
sizeof8 = 1
sizeof16 = 2
sizeof32 = 4
sizeof64 = 8
)
func staticSize(typ reflect.Type) (int, error) {
if typ.Implements(staticSizerType) {
//nolint:forcetypeassert // Already did a type check via reflection.
return reflect.New(typ).Elem().Interface().(StaticSizer).BinaryStaticSize(), nil
}
if typ.Implements(marshalerType) || typ.Implements(unmarshalerType) {
// If you implement binstruct.Marshaler or binstruct.Unmarshaler,
// then you must implement if you wish to be statically sized.
return 0, &InvalidTypeError{
Type: typ,
Err: errors.New("does not implement binstruct.StaticSizer but does implement binstruct.Marshaler or binstruct.Unmarshaler"),
}
}
switch typ.Kind() {
case reflect.Uint8, reflect.Int8:
return sizeof8, nil
case reflect.Uint16, reflect.Int16:
return sizeof16, nil
case reflect.Uint32, reflect.Int32:
return sizeof32, nil
case reflect.Uint64, reflect.Int64:
return sizeof64, nil
case reflect.Ptr:
return staticSize(typ.Elem())
case reflect.Array:
elemSize, err := staticSize(typ.Elem())
if err != nil {
return 0, err
}
return elemSize * typ.Len(), nil
case reflect.Struct:
return getStructHandler(typ).Size, nil
default:
return 0, &InvalidTypeError{
Type: typ,
Err: fmt.Errorf("does not implement binfmt.StaticSizer and kind=%v is not a supported statically-sized kind",
typ.Kind()),
}
}
}
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