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|
package binstruct
import (
"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()
)
func staticSize(typ reflect.Type) (int, error) {
if typ.Implements(staticSizerType) {
return reflect.New(typ).Elem().Interface().(StaticSizer).BinaryStaticSize(), nil
}
switch typ.Kind() {
case reflect.Uint8, reflect.Int8:
return 1, nil
case reflect.Uint16, reflect.Int16:
return 2, nil
case reflect.Uint32, reflect.Int32:
return 4, nil
case reflect.Uint64, reflect.Int64:
return 8, 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:
if !(typ.Implements(marshalerType) || typ.Implements(unmarshalerType)) {
return getStructHandler(typ).Size, nil
}
return 0, fmt.Errorf("type=%v (kind=%v) does not implement binfmt.StaticSizer but does implement binfmt.Marshaler or binfmt.Unmarshaler",
typ, typ.Kind())
default:
return 0, fmt.Errorf("type=%v does not implement binfmt.StaticSizer and kind=%v is not a supported statically-sized kind",
typ, typ.Kind())
}
}
|
