text: // Copyright 2011 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 aix darwin dragonfly freebsd linux,!appengine netbsd openbsd
  
  // Package terminal provides support functions for dealing with terminals, as
  // commonly found on UNIX systems.
  //
  // Putting a terminal into raw mode is the most common requirement:
  //
  // 	oldState, err := terminal.MakeRaw(0)
  // 	if err != nil {
  // 	        panic(err)
  // 	}
  // 	defer terminal.Restore(0, oldState)
  package terminal // import "golang.org/x/crypto/ssh/terminal"
  
  import (
  	"golang.org/x/sys/unix"
  )
  
  // State contains the state of a terminal.
  type State struct {
  	termios unix.Termios
  }
  
  // IsTerminal returns whether the given file descriptor is a terminal.
  func IsTerminal(fd int) bool {
  	_, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
  	return err == nil
  }
  
  // MakeRaw put the terminal connected to the given file descriptor into raw
  // mode and returns the previous state of the terminal so that it can be
  // restored.
  func MakeRaw(fd int) (*State, error) {
  	termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
  	if err != nil {
  		return nil, err
  	}
  
  	oldState := State{termios: *termios}
  
  	// This attempts to replicate the behaviour documented for cfmakeraw in
  	// the termios(3) manpage.
  	termios.Iflag &^= unix.IGNBRK | unix.BRKINT | unix.PARMRK | unix.ISTRIP | unix.INLCR | unix.IGNCR | unix.ICRNL | unix.IXON
  	termios.Oflag &^= unix.OPOST
  	termios.Lflag &^= unix.ECHO | unix.ECHONL | unix.ICANON | unix.ISIG | unix.IEXTEN
  	termios.Cflag &^= unix.CSIZE | unix.PARENB
  	termios.Cflag |= unix.CS8
  	termios.Cc[unix.VMIN] = 1
  	termios.Cc[unix.VTIME] = 0
  	if err := unix.IoctlSetTermios(fd, ioctlWriteTermios, termios); err != nil {
  		return nil, err
  	}
  
  	return &oldState, nil
  }
  
  // GetState returns the current state of a terminal which may be useful to
  // restore the terminal after a signal.
  func GetState(fd int) (*State, error) {
  	termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
  	if err != nil {
  		return nil, err
  	}
  
  	return &State{termios: *termios}, nil
  }
  
  // Restore restores the terminal connected to the given file descriptor to a
  // previous state.
  func Restore(fd int, state *State) error {
  	return unix.IoctlSetTermios(fd, ioctlWriteTermios, &state.termios)
  }
  
  // GetSize returns the dimensions of the given terminal.
  func GetSize(fd int) (width, height int, err error) {
  	ws, err := unix.IoctlGetWinsize(fd, unix.TIOCGWINSZ)
  	if err != nil {
  		return -1, -1, err
  	}
  	return int(ws.Col), int(ws.Row), nil
  }
  
  // passwordReader is an io.Reader that reads from a specific file descriptor.
  type passwordReader int
  
  func (r passwordReader) Read(buf []byte) (int, error) {
  	return unix.Read(int(r), buf)
  }
  
  // ReadPassword reads a line of input from a terminal without local echo.  This
  // is commonly used for inputting passwords and other sensitive data. The slice
  // returned does not include the \n.
  func ReadPassword(fd int) ([]byte, error) {
  	termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
  	if err != nil {
  		return nil, err
  	}
  
  	newState := *termios
  	newState.Lflag &^= unix.ECHO
  	newState.Lflag |= unix.ICANON | unix.ISIG
  	newState.Iflag |= unix.ICRNL
  	if err := unix.IoctlSetTermios(fd, ioctlWriteTermios, &newState); err != nil {
  		return nil, err
  	}
  
  	defer unix.IoctlSetTermios(fd, ioctlWriteTermios, termios)
  
  	return readPasswordLine(passwordReader(fd))
  }
  