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	// 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))
	}

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