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// 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
import (
"io"
"gvisor.dev/gvisor/pkg/usermem"
)
// Task provides a subset of kernel.Task, used in marshalling. We don't import
// the kernel package directly to avoid circular dependency.
type Task interface {
// CopyScratchBuffer provides a task goroutine-local scratch buffer. See
// kernel.CopyScratchBuffer.
CopyScratchBuffer(size int) []byte
// CopyOutBytes writes the contents of b to the task's memory. See
// kernel.CopyOutBytes.
CopyOutBytes(addr usermem.Addr, b []byte) (int, error)
// CopyInBytes reads the contents of the task's memory to b. See
// kernel.CopyInBytes.
CopyInBytes(addr usermem.Addr, b []byte) (int, error)
}
// Marshallable represents a type that can be marshalled to and from memory.
type Marshallable interface {
io.WriterTo
// SizeBytes is the size of the memory representation of a type in
// marshalled form.
//
// SizeBytes must handle a nil receiver. Practically, this means SizeBytes
// cannot deference any fields on the object implementing it (but will
// likely make use of the type of these fields).
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 by directly copying 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.
UnmarshalUnsafe(src []byte)
// CopyIn deserializes a Marshallable type from a task's memory. This may
// only be called from a task goroutine. This is more efficient than calling
// UnmarshalUnsafe on Marshallable.Packed types, as the type being
// marshalled does not escape. The implementation should avoid creating
// extra copies in memory by directly deserializing to the object's
// underlying memory.
CopyIn(task Task, addr usermem.Addr) error
// CopyOut serializes a Marshallable type to a task's memory. This may only
// be called from a task goroutine. This is more efficient than calling
// MarshalUnsafe on Marshallable.Packed types, as the type being serialized
// does not escape. The implementation should avoid creating extra copies in
// memory by directly serializing from the object's underlying memory.
CopyOut(task Task, addr usermem.Addr) error
}
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