tramp-blog/commands/stty.go

package commands

import (
	"errors"
	"log"
	"strconv"

	"golang.org/x/sys/unix"
)

func Control(c rune) rune {
	return c & 0x1f
}

func sttyCharFromDesc(c string) (rune, error) {
	if len(c) > 2 || len(c) < 1 {
		return 'i', errors.New(
			"stty char description has unsupported length: " +
				strconv.Itoa(len(c)),
		)
	}

	if rune(c[0]) == '^' {
		return Control(rune(c[1])), nil
	}

	return rune(c[0]), nil
}

const fakeUname = "Linux 5.16.19-76051619-generic"

type CommandExecutor interface {
	Execute(shell *Shell, args []string) error
}

type SttyCommand struct{}

func (c *SttyCommand) Execute(shell *Shell, args []string) error {
	// Tramp uses:
	// -inlcr: don't translate newline to carriage return
	// -onlcr: don't translate newline to carriage return-newline
	// -echo: echo input characters
	// kill CHAR: CHAR will erase the current line
	// erase CHAR: CHAR will erase the last character typed
	// icanon: enable special charactersq

	fd := int(shell.GetPty().Fd())
	const ioctlReadTermios = unix.TCGETS  // Linux
	const ioctlWriteTermios = unix.TCSETS // Linux

	termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
	if err != nil {
		panic(err)
	}

	newState := *termios

	var skipNext bool
	for i, arg := range args {
		if skipNext {
			skipNext = false
			continue
		}

		var disable bool
		if arg[0] == '-' {
			disable = true
			arg = arg[1:]
		}

		switch arg {
		case "onlcr":
			if disable {
				newState.Iflag &^= unix.ONLCR
				continue
			}

			newState.Iflag |= unix.ONLCR
		case "inlcr":
			if disable {
				newState.Iflag &^= unix.INLCR
				continue
			}

			newState.Iflag |= unix.INLCR
		case "echo":
			if disable {
				newState.Lflag &^= unix.ECHO
				continue
			}

			newState.Lflag |= unix.ECHO
		case "kill":
			skipNext = true

			char, err := sttyCharFromDesc(args[i+1])
			if err != nil {
				log.Printf(
					"Warning: Not applying unsupported character description for stty kill: %s",
					args[i+1],
				)
				continue
			}

			newState.Cc[unix.VKILL] = uint8(char)
		case "erase":
			skipNext = true

			char, err := sttyCharFromDesc(args[i+1])
			if err != nil {
				log.Printf(
					"Warning: Not applying unsupported character description for stty erase: %s",
					args[i+1],
				)
				continue
			}

			newState.Cc[unix.VERASE] = uint8(char)
		case "icanon":
			if disable {
				newState.Lflag &^= unix.ICANON
				continue
			}

			newState.Lflag |= unix.ICANON

		case "tab0":
			newState.Oflag = (newState.Oflag & ^uint32(unix.TABDLY)) | unix.TAB0
		case "iutf8":
			if disable {
				newState.Iflag &^= unix.IUTF8
				continue
			}

			newState.Iflag |= unix.IUTF8

		default:
			log.Printf(
				"Warning, tramp requested unexpected stty option %s",
				arg,
			)
		}
	}

	if err := unix.IoctlSetTermios(fd, ioctlWriteTermios, &newState); err != nil {
		return err
	}

	return nil
}