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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 linux

// 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 (

        "io"

        "syscall"

        "unsafe"

)

// State contains the state of a terminal.

type State struct {

        termios syscall.Termios

}

// IsTerminal returns true if the given file descriptor is a terminal.

func IsTerminal(fd int) bool {

        var termios syscall.Termios

        err := syscall.Tcgetattr(fd, &termios)

        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) {

        var oldState State

        if err := syscall.Tcgetattr(fd, &oldState.termios); err != nil {

                return nil, err

        }

        newState := oldState.termios

        newState.Iflag &^= syscall.ISTRIP | syscall.INLCR | syscall.ICRNL | syscall.IGNCR | syscall.IXON | syscall.IXOFF

        newState.Lflag &^= syscall.ECHO | syscall.ICANON | syscall.ISIG

        if err := syscall.Tcsetattr(fd, syscall.TCSANOW, &newState); err != nil {

                return nil, err

        }

        return &oldState, nil

}

// Restore restores the terminal connected to the given file descriptor to a

// previous state.

func Restore(fd int, state *State) error {

        err := syscall.Tcsetattr(fd, syscall.TCSANOW, &state.termios)

        return err

}

//extern ioctl

func ioctl(int, int, unsafe.Pointer) int

// GetSize returns the dimensions of the given terminal.

func GetSize(fd int) (width, height int, err error) {

        var dimensions [4]uint16

        if ioctl(fd, syscall.TIOCGWINSZ, unsafe.Pointer(&dimensions)) < 0 {

                return -1, -1, syscall.GetErrno()

        }

        return int(dimensions[1]), int(dimensions[0]), nil

}

// 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) {

        var oldState syscall.Termios

        if err := syscall.Tcgetattr(fd, &oldState); err != nil {

                return nil, err

        }

        newState := oldState

        newState.Lflag &^= syscall.ECHO

        if err := syscall.Tcsetattr(fd, syscall.TCSANOW, &newState); err != nil {

                return nil, err

        }

        defer func() {

                syscall.Tcsetattr(fd, syscall.TCSANOW, &oldState)

        }()

        var buf [16]byte

        var ret []byte

        for {

                n, err := syscall.Read(fd, buf[:])

                if err != nil {

                        return nil, err

                }

                if n == 0 {

                        if len(ret) == 0 {

                                return nil, io.EOF

                        }

                        break

                }

                if buf[n-1] == '\n' {

                        n--

                }

                ret = append(ret, buf[:n]...)

                if n < len(buf) {

                        break

                }

        }

        return ret, nil

}