channel.go

/*
Copyright (c) 2017 VMware, Inc. All Rights Reserved.

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 toolbox

import (
	"bytes"
	"fmt"
)

// Channel abstracts the guest<->vmx RPC transport
type Channel interface {
	Start() error
	Stop() error
	Send([]byte) error
	Receive() ([]byte, error)
}

var (
	rpciOK  = []byte{'1', ' '}
	rpciERR = []byte{'0', ' '}
)

// ChannelOut extends Channel to provide RPCI protocol helpers
type ChannelOut struct {
	Channel
}

// Request sends an RPC command to the vmx and checks the return code for success or error
func (c *ChannelOut) Request(request []byte) ([]byte, error) {
	if err := c.Send(request); err != nil {
		return nil, err
	}

	reply, err := c.Receive()
	if err != nil {
		return nil, err
	}

	if bytes.HasPrefix(reply, rpciOK) {
		return reply[2:], nil
	}

	return nil, fmt.Errorf("request %q: %q", request, reply)
}