tty.go

// Copyright (c) 2018 SUSE LLC. 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 main

import (
	"context"
	"log"
	"syscall"
	"unsafe"

	"github.com/docker/docker/api/types"
)

// Resize the TTY of the container with the given id to the size of the current
// TTY.
func resizeTty(id string) {
	height, width := getTtySize()
	if height == 0 && width == 0 {
		return
	}

	client := getDockerClient()
	err := client.ContainerResize(context.Background(), id, types.ResizeOptions{
		Height: height,
		Width:  width,
	})

	if err != nil {
		log.Printf("Could not resize container: %v", err)
	}
}

// Get the size of the current TTY. On error, the returned values will be zero
// and the error itself will be logged.
func getTtySize() (uint, uint) {
	size := &struct {
		Height uint
		Width  uint

		// Not needed but we may avoid some random crashes.
		x uint
		y uint
	}{}

	// Call ioctl, requesting the size of the window.
	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, 1,
		uintptr(syscall.TIOCGWINSZ), uintptr(unsafe.Pointer(size)))

	if errno != 0 {
		return 0, 0
	}
	return uint(size.Height), uint(size.Width)
}