// Copyright 2019 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package marshal defines the Marshallable interface for
// serialize/deserializing go data structures to/from memory, according to the
// Linux ABI.
//
// Implementations of this interface are typically automatically generated by
// tools/go_marshal. See the go_marshal README for details.
package marshal

// Marshallable represents a type that can be marshalled to and from memory.
type Marshallable interface {
	// SizeBytes is the size of the memory representation of a type in
	// marshalled form.
	SizeBytes() int

	// MarshalBytes serializes a copy of a type to dst. dst must be at least
	// SizeBytes() long.
	MarshalBytes(dst []byte)

	// UnmarshalBytes deserializes a type from src. src must be at least
	// SizeBytes() long.
	UnmarshalBytes(src []byte)

	// Packed returns true if the marshalled size of the type is the same as the
	// size it occupies in memory. This happens when the type has no fields
	// starting at unaligned addresses (should always be true by default for ABI
	// structs, verified by automatically generated tests when using
	// go_marshal), and has no fields marked `marshal:"unaligned"`.
	Packed() bool

	// MarshalUnsafe serializes a type by bulk copying its in-memory
	// representation to the dst buffer. This is only safe to do when the type
	// has no implicit padding, see Marshallable.Packed. When Packed would
	// return false, MarshalUnsafe should fall back to the safer but slower
	// MarshalBytes.
	MarshalUnsafe(dst []byte)

	// UnmarshalUnsafe deserializes a type directly to the underlying memory
	// allocated for the object by the runtime.
	//
	// This allows much faster unmarshalling of types which have no implicit
	// padding, see Marshallable.Packed. When Packed would return false,
	// UnmarshalUnsafe should fall back to the safer but slower unmarshal
	// mechanism implemented in UnmarshalBytes (usually by calling
	// UnmarshalBytes directly).
	UnmarshalUnsafe(src []byte)
}