src/syscall/zx/fidl/message.go

// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build fuchsia

package fidl

import (
	"sync"

	"syscall/zx"
)

// messageBytesPool is a pool of buffers that can fit the data part of any
// FIDL message.
var messageBytesPool = sync.Pool{
	New: func() interface{} {
		return make([]byte, zx.ChannelMaxMessageBytes)
	},
}

// messageHandlesPool is a pool of buffers that can fit the handles part of
// any FIDL message.
var messageHandlesPool = sync.Pool{
	New: func() interface{} {
		return make([]zx.Handle, zx.ChannelMaxMessageHandles)
	},
}

// MessageHeaderSize is the size of the encoded message header.
const MessageHeaderSize int = 16

// MessageHeader is a header information for a message. This struct
// corresponds to the C type fidl_message_header_t.
type MessageHeader struct {
	Txid     uint32
	Reserved uint32
	Flags    uint32
	Ordinal  uint32
}

// Payload is an interface implemented by every FIDL structure.
type Payload interface {
	// InlineSize returns the inline size of the structure, without any
	// out-of-line structures.
	InlineSize() int

	// InlineAlignment returns the alignment of the structure.
	InlineAlignment() int
}

// MarshalMessage is a convenience function for marshalling a full FIDL message,
// that is, header and payload.
func MarshalMessage(header *MessageHeader, s Payload, data []byte, handles []zx.Handle) (int, int, error) {
	MarshalHeader(header, data[:MessageHeaderSize])
	nb, nh, err := Marshal(s, data[MessageHeaderSize:], handles[:])
	return nb + MessageHeaderSize, nh, err
}

// UnmarshalMessage is a convenience function for unmarshalling a full FIDL message,
// that is, header and payload.
func UnmarshalMessage(data []byte, handles []zx.Handle, header *MessageHeader, s Payload) error {
	if err := UnmarshalHeader(data[:MessageHeaderSize], header); err != nil {
		return err
	}
	return Unmarshal(data[MessageHeaderSize:], handles[:], s)
}