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+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

pkg/terminal/terminal.go

+// 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.
+
+package terminal
+
+import (
+	"io"
+	"sync"
+)
+
+// EscapeCodes contains escape sequences that can be written to the terminal in
+// order to achieve different styles of text.
+type EscapeCodes struct {
+	// Foreground colors
+	Black, Red, Green, Yellow, Blue, Magenta, Cyan, White []byte
+
+	// Reset all attributes
+	Reset []byte
+}
+
+var vt100EscapeCodes = EscapeCodes{
+	Black:   []byte{keyEscape, '[', '3', '0', 'm'},
+	Red:     []byte{keyEscape, '[', '3', '1', 'm'},
+	Green:   []byte{keyEscape, '[', '3', '2', 'm'},
+	Yellow:  []byte{keyEscape, '[', '3', '3', 'm'},
+	Blue:    []byte{keyEscape, '[', '3', '4', 'm'},
+	Magenta: []byte{keyEscape, '[', '3', '5', 'm'},
+	Cyan:    []byte{keyEscape, '[', '3', '6', 'm'},
+	White:   []byte{keyEscape, '[', '3', '7', 'm'},
+
+	Reset: []byte{keyEscape, '[', '0', 'm'},
+}
+
+// Terminal contains the state for running a VT100 terminal that is capable of
+// reading lines of input.
+type Terminal struct {
+	// AutoCompleteCallback, if non-null, is called for each keypress
+	// with the full input line and the current position of the cursor.
+	// If it returns a nil newLine, the key press is processed normally.
+	// Otherwise it returns a replacement line and the new cursor position.
+	AutoCompleteCallback func(line []byte, pos, key int) (newLine []byte, newPos int)
+
+	// Escape contains a pointer to the escape codes for this terminal.
+	// It's always a valid pointer, although the escape codes themselves
+	// may be empty if the terminal doesn't support them.
+	Escape *EscapeCodes
+
+	// lock protects the terminal and the state in this object from
+	// concurrent processing of a key press and a Write() call.
+	lock sync.Mutex
+
+	c      io.ReadWriter
+	prompt string
+
+	// line is the current line being entered.
+	line []byte
+	// pos is the logical position of the cursor in line
+	pos int
+	// echo is true if local echo is enabled
+	echo bool
+
+	// cursorX contains the current X value of the cursor where the left
+	// edge is 0. cursorY contains the row number where the first row of
+	// the current line is 0.
+	cursorX, cursorY int
+	// maxLine is the greatest value of cursorY so far.
+	maxLine int
+
+	termWidth, termHeight int
+
+	// outBuf contains the terminal data to be sent.
+	outBuf []byte
+	// remainder contains the remainder of any partial key sequences after
+	// a read. It aliases into inBuf.
+	remainder []byte
+	inBuf     [256]byte
+}
+
+// NewTerminal runs a VT100 terminal on the given ReadWriter. If the ReadWriter is
+// a local terminal, that terminal must first have been put into raw mode.
+// prompt is a string that is written at the start of each input line (i.e.
+// "> ").
+func NewTerminal(c io.ReadWriter, prompt string) *Terminal {
+	return &Terminal{
+		Escape:     &vt100EscapeCodes,
+		c:          c,
+		prompt:     prompt,
+		termWidth:  80,
+		termHeight: 24,
+		echo:       true,
+	}
+}
+
+const (
+	keyCtrlD     = 4
+	keyEnter     = '\r'
+	keyEscape    = 27
+	keyBackspace = 127
+	keyUnknown   = 256 + iota
+	keyUp
+	keyDown
+	keyLeft
+	keyRight
+	keyAltLeft
+	keyAltRight
+)
+
+// bytesToKey tries to parse a key sequence from b. If successful, it returns
+// the key and the remainder of the input. Otherwise it returns -1.
+func bytesToKey(b []byte) (int, []byte) {
+	if len(b) == 0 {
+		return -1, nil
+	}
+
+	if b[0] != keyEscape {
+		return int(b[0]), b[1:]
+	}
+
+	if len(b) >= 3 && b[0] == keyEscape && b[1] == '[' {
+		switch b[2] {
+		case 'A':
+			return keyUp, b[3:]
+		case 'B':
+			return keyDown, b[3:]
+		case 'C':
+			return keyRight, b[3:]
+		case 'D':
+			return keyLeft, b[3:]
+		}
+	}
+
+	if len(b) >= 6 && b[0] == keyEscape && b[1] == '[' && b[2] == '1' && b[3] == ';' && b[4] == '3' {
+		switch b[5] {
+		case 'C':
+			return keyAltRight, b[6:]
+		case 'D':
+			return keyAltLeft, b[6:]
+		}
+	}
+
+	// If we get here then we have a key that we don't recognise, or a
+	// partial sequence. It's not clear how one should find the end of a
+	// sequence without knowing them all, but it seems that [a-zA-Z] only
+	// appears at the end of a sequence.
+	for i, c := range b[0:] {
+		if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' {
+			return keyUnknown, b[i+1:]
+		}
+	}
+
+	return -1, b
+}
+
+// queue appends data to the end of t.outBuf
+func (t *Terminal) queue(data []byte) {
+	t.outBuf = append(t.outBuf, data...)
+}
+
+var eraseUnderCursor = []byte{' ', keyEscape, '[', 'D'}
+var space = []byte{' '}
+
+func isPrintable(key int) bool {
+	return key >= 32 && key < 127
+}
+
+// moveCursorToPos appends data to t.outBuf which will move the cursor to the
+// given, logical position in the text.
+func (t *Terminal) moveCursorToPos(pos int) {
+	if !t.echo {
+		return
+	}
+
+	x := len(t.prompt) + pos
+	y := x / t.termWidth
+	x = x % t.termWidth
+
+	up := 0
+	if y < t.cursorY {
+		up = t.cursorY - y
+	}
+
+	down := 0
+	if y > t.cursorY {
+		down = y - t.cursorY
+	}
+
+	left := 0
+	if x < t.cursorX {
+		left = t.cursorX - x
+	}
+
+	right := 0
+	if x > t.cursorX {
+		right = x - t.cursorX
+	}
+
+	t.cursorX = x
+	t.cursorY = y
+	t.move(up, down, left, right)
+}
+
+func (t *Terminal) move(up, down, left, right int) {
+	movement := make([]byte, 3*(up+down+left+right))
+	m := movement
+	for i := 0; i < up; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'A'
+		m = m[3:]
+	}
+	for i := 0; i < down; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'B'
+		m = m[3:]
+	}
+	for i := 0; i < left; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'D'
+		m = m[3:]
+	}
+	for i := 0; i < right; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'C'
+		m = m[3:]
+	}
+
+	t.queue(movement)
+}
+
+func (t *Terminal) clearLineToRight() {
+	op := []byte{keyEscape, '[', 'K'}
+	t.queue(op)
+}
+
+const maxLineLength = 4096
+
+// handleKey processes the given key and, optionally, returns a line of text
+// that the user has entered.
+func (t *Terminal) handleKey(key int) (line string, ok bool) {
+	switch key {
+	case keyBackspace:
+		if t.pos == 0 {
+			return
+		}
+		t.pos--
+		t.moveCursorToPos(t.pos)
+
+		copy(t.line[t.pos:], t.line[1+t.pos:])
+		t.line = t.line[:len(t.line)-1]
+		if t.echo {
+			t.writeLine(t.line[t.pos:])
+		}
+		t.queue(eraseUnderCursor)
+		t.moveCursorToPos(t.pos)
+	case keyAltLeft:
+		// move left by a word.
+		if t.pos == 0 {
+			return
+		}
+		t.pos--
+		for t.pos > 0 {
+			if t.line[t.pos] != ' ' {
+				break
+			}
+			t.pos--
+		}
+		for t.pos > 0 {
+			if t.line[t.pos] == ' ' {
+				t.pos++
+				break
+			}
+			t.pos--
+		}
+		t.moveCursorToPos(t.pos)
+	case keyAltRight:
+		// move right by a word.
+		for t.pos < len(t.line) {
+			if t.line[t.pos] == ' ' {
+				break
+			}
+			t.pos++
+		}
+		for t.pos < len(t.line) {
+			if t.line[t.pos] != ' ' {
+				break
+			}
+			t.pos++
+		}
+		t.moveCursorToPos(t.pos)
+	case keyLeft:
+		if t.pos == 0 {
+			return
+		}
+		t.pos--
+		t.moveCursorToPos(t.pos)
+	case keyRight:
+		if t.pos == len(t.line) {
+			return
+		}
+		t.pos++
+		t.moveCursorToPos(t.pos)
+	case keyEnter:
+		t.moveCursorToPos(len(t.line))
+		t.queue([]byte("\r\n"))
+		line = string(t.line)
+		ok = true
+		t.line = t.line[:0]
+		t.pos = 0
+		t.cursorX = 0
+		t.cursorY = 0
+		t.maxLine = 0
+	default:
+		if t.AutoCompleteCallback != nil {
+			t.lock.Unlock()
+			newLine, newPos := t.AutoCompleteCallback(t.line, t.pos, key)
+			t.lock.Lock()
+
+			if newLine != nil {
+				if t.echo {
+					t.moveCursorToPos(0)
+					t.writeLine(newLine)
+					for i := len(newLine); i < len(t.line); i++ {
+						t.writeLine(space)
+					}
+					t.moveCursorToPos(newPos)
+				}
+				t.line = newLine
+				t.pos = newPos
+				return
+			}
+		}
+		if !isPrintable(key) {
+			return
+		}
+		if len(t.line) == maxLineLength {
+			return
+		}
+		if len(t.line) == cap(t.line) {
+			newLine := make([]byte, len(t.line), 2*(1+len(t.line)))
+			copy(newLine, t.line)
+			t.line = newLine
+		}
+		t.line = t.line[:len(t.line)+1]
+		copy(t.line[t.pos+1:], t.line[t.pos:])
+		t.line[t.pos] = byte(key)
+		if t.echo {
+			t.writeLine(t.line[t.pos:])
+		}
+		t.pos++
+		t.moveCursorToPos(t.pos)
+	}
+	return
+}
+
+func (t *Terminal) writeLine(line []byte) {
+	for len(line) != 0 {
+		remainingOnLine := t.termWidth - t.cursorX
+		todo := len(line)
+		if todo > remainingOnLine {
+			todo = remainingOnLine
+		}
+		t.queue(line[:todo])
+		t.cursorX += todo
+		line = line[todo:]
+
+		if t.cursorX == t.termWidth {
+			t.cursorX = 0
+			t.cursorY++
+			if t.cursorY > t.maxLine {
+				t.maxLine = t.cursorY
+			}
+		}
+	}
+}
+
+func (t *Terminal) Write(buf []byte) (n int, err error) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	if t.cursorX == 0 && t.cursorY == 0 {
+		// This is the easy case: there's nothing on the screen that we
+		// have to move out of the way.
+		return t.c.Write(buf)
+	}
+
+	// We have a prompt and possibly user input on the screen. We
+	// have to clear it first.
+	t.move(0 /* up */, 0 /* down */, t.cursorX /* left */, 0 /* right */)
+	t.cursorX = 0
+	t.clearLineToRight()
+
+	for t.cursorY > 0 {
+		t.move(1 /* up */, 0, 0, 0)
+		t.cursorY--
+		t.clearLineToRight()
+	}
+
+	if _, err = t.c.Write(t.outBuf); err != nil {
+		return
+	}
+	t.outBuf = t.outBuf[:0]
+
+	if n, err = t.c.Write(buf); err != nil {
+		return
+	}
+
+	t.queue([]byte(t.prompt))
+	chars := len(t.prompt)
+	if t.echo {
+		t.queue(t.line)
+		chars += len(t.line)
+	}
+	t.cursorX = chars % t.termWidth
+	t.cursorY = chars / t.termWidth
+	t.moveCursorToPos(t.pos)
+
+	if _, err = t.c.Write(t.outBuf); err != nil {
+		return
+	}
+	t.outBuf = t.outBuf[:0]
+	return
+}
+
+// ReadPassword temporarily changes the prompt and reads a password, without
+// echo, from the terminal.
+func (t *Terminal) ReadPassword(prompt string) (line string, err error) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	oldPrompt := t.prompt
+	t.prompt = prompt
+	t.echo = false
+
+	line, err = t.readLine()
+
+	t.prompt = oldPrompt
+	t.echo = true
+
+	return
+}
+
+// ReadLine returns a line of input from the terminal.
+func (t *Terminal) ReadLine() (line string, err error) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	return t.readLine()
+}
+
+func (t *Terminal) readLine() (line string, err error) {
+	// t.lock must be held at this point
+
+	if t.cursorX == 0 && t.cursorY == 0 {
+		t.writeLine([]byte(t.prompt))
+		t.c.Write(t.outBuf)
+		t.outBuf = t.outBuf[:0]
+	}
+
+	for {
+		rest := t.remainder
+		lineOk := false
+		for !lineOk {
+			var key int
+			key, rest = bytesToKey(rest)
+			if key < 0 {
+				break
+			}
+			if key == keyCtrlD {
+				return "", io.EOF
+			}
+			line, lineOk = t.handleKey(key)
+		}
+		if len(rest) > 0 {
+			n := copy(t.inBuf[:], rest)
+			t.remainder = t.inBuf[:n]
+		} else {
+			t.remainder = nil
+		}
+		t.c.Write(t.outBuf)
+		t.outBuf = t.outBuf[:0]
+		if lineOk {
+			return
+		}
+
+		// t.remainder is a slice at the beginning of t.inBuf
+		// containing a partial key sequence
+		readBuf := t.inBuf[len(t.remainder):]
+		var n int
+
+		t.lock.Unlock()
+		n, err = t.c.Read(readBuf)
+		t.lock.Lock()
+
+		if err != nil {
+			return
+		}
+
+		t.remainder = t.inBuf[:n+len(t.remainder)]
+	}
+	panic("unreachable")
+}
+
+// SetPrompt sets the prompt to be used when reading subsequent lines.
+func (t *Terminal) SetPrompt(prompt string) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	t.prompt = prompt
+}
+
+func (t *Terminal) SetSize(width, height int) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	t.termWidth, t.termHeight = width, height
+}

pkg/terminal/terminal_test.go

+// 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.
+
+package terminal
+
+import (
+	"io"
+	"testing"
+)
+
+type MockTerminal struct {
+	toSend       []byte
+	bytesPerRead int
+	received     []byte
+}
+
+func (c *MockTerminal) Read(data []byte) (n int, err error) {
+	n = len(data)
+	if n == 0 {
+		return
+	}
+	if n > len(c.toSend) {
+		n = len(c.toSend)
+	}
+	if n == 0 {
+		return 0, io.EOF
+	}
+	if c.bytesPerRead > 0 && n > c.bytesPerRead {
+		n = c.bytesPerRead
+	}
+	copy(data, c.toSend[:n])
+	c.toSend = c.toSend[n:]
+	return
+}
+
+func (c *MockTerminal) Write(data []byte) (n int, err error) {
+	c.received = append(c.received, data...)
+	return len(data), nil
+}
+
+func TestClose(t *testing.T) {
+	c := &MockTerminal{}
+	ss := NewTerminal(c, "> ")
+	line, err := ss.ReadLine()
+	if line != "" {
+		t.Errorf("Expected empty line but got: %s", line)
+	}
+	if err != io.EOF {
+		t.Errorf("Error should have been EOF but got: %s", err)
+	}
+}
+
+var keyPressTests = []struct {
+	in   string
+	line string
+	err  error
+}{
+	{
+		"",
+		"",
+		io.EOF,
+	},
+	{
+		"\r",
+		"",
+		nil,
+	},
+	{
+		"foo\r",
+		"foo",
+		nil,
+	},
+	{
+		"a\x1b[Cb\r", // right
+		"ab",
+		nil,
+	},
+	{
+		"a\x1b[Db\r", // left
+		"ba",
+		nil,
+	},
+	{
+		"a\177b\r", // backspace
+		"b",
+		nil,
+	},
+}
+
+func TestKeyPresses(t *testing.T) {
+	for i, test := range keyPressTests {
+		for j := 0; j < len(test.in); j++ {
+			c := &MockTerminal{
+				toSend:       []byte(test.in),
+				bytesPerRead: j,
+			}
+			ss := NewTerminal(c, "> ")
+			line, err := ss.ReadLine()
+			if line != test.line {
+				t.Errorf("Line resulting from test %d (%d bytes per read) was '%s', expected '%s'", i, j, line, test.line)
+				break
+			}
+			if err != test.err {
+				t.Errorf("Error resulting from test %d (%d bytes per read) was '%v', expected '%v'", i, j, err, test.err)
+				break
+			}
+		}
+	}
+}

pkg/terminal/termios.go

+// +build ignore
+
+package terminal
+
+/*
+#include <termios.h>
+#include <sys/ioctl.h>
+*/
+import "C"
+
+type syscall_Termios C.struct_termios
+
+const (
+	syscall_IGNBRK = C.IGNBRK
+	syscall_BRKINT = C.BRKINT
+	syscall_PARMRK = C.PARMRK
+	syscall_ISTRIP = C.ISTRIP
+	syscall_INLCR  = C.INLCR
+	syscall_IGNCR  = C.IGNCR
+	syscall_ICRNL  = C.ICRNL
+	syscall_IXON   = C.IXON
+	syscall_IXOFF  = C.IXOFF
+	syscall_OPOST  = C.OPOST
+	syscall_ECHO   = C.ECHO
+	syscall_ECHONL = C.ECHONL
+	syscall_ICANON = C.ICANON
+	syscall_ISIG   = C.ISIG
+	syscall_IEXTEN = C.IEXTEN
+	syscall_CSIZE  = C.CSIZE
+	syscall_PARENB = C.PARENB
+	syscall_CS8    = C.CS8
+	syscall_VMIN   = C.VMIN
+	syscall_VTIME  = C.VTIME
+
+	// on darwin change these to (on *bsd too?):
+	// C.TIOCGETA
+	// C.TIOCSETA
+	syscall_TCGETS = C.TIOCGETA
+	syscall_TCSETS = C.TIOCSETA
+)

pkg/terminal/termios_darwin_amd64.go

+// Created by cgo -godefs - DO NOT EDIT
+// cgo -godefs termios.go
+
+package terminal
+
+type syscall_Termios struct {
+	Iflag		uint64
+	Oflag		uint64
+	Cflag		uint64
+	Lflag		uint64
+	Cc		[20]uint8
+	Pad_cgo_0	[4]byte
+	Ispeed		uint64
+	Ospeed		uint64
+}
+
+const (
+	syscall_IGNBRK	= 0x1
+	syscall_BRKINT	= 0x2
+	syscall_PARMRK	= 0x8
+	syscall_ISTRIP	= 0x20
+	syscall_INLCR	= 0x40
+	syscall_IGNCR	= 0x80
+	syscall_ICRNL	= 0x100
+	syscall_IXON	= 0x200
+	syscall_IXOFF	= 0x400
+	syscall_OPOST	= 0x1
+	syscall_ECHO	= 0x8
+	syscall_ECHONL	= 0x10
+	syscall_ICANON	= 0x100
+	syscall_ISIG	= 0x80
+	syscall_IEXTEN	= 0x400
+	syscall_CSIZE	= 0x300
+	syscall_PARENB	= 0x1000
+	syscall_CS8	= 0x300
+	syscall_VMIN	= 0x10
+	syscall_VTIME	= 0x11
+
+	syscall_TCGETS	= 0x40487413
+	syscall_TCSETS	= 0x80487414
+)

pkg/terminal/util.go

+// 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 darwin
+
+// 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.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall_TCGETS), uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
+	return err == 0
+}
+
+// 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.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall_TCGETS), uintptr(unsafe.Pointer(&oldState.termios)), 0, 0, 0); err != 0 {
+		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.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall_TCSETS), uintptr(unsafe.Pointer(&newState)), 0, 0, 0); err != 0 {
+		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.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall_TCSETS), uintptr(unsafe.Pointer(&state.termios)), 0, 0, 0)
+	return err
+}
+
+// GetSize returns the dimensions of the given terminal.
+func GetSize(fd int) (width, height int, err error) {
+	var dimensions [4]uint16
+
+	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall.TIOCGWINSZ), uintptr(unsafe.Pointer(&dimensions)), 0, 0, 0); err != 0 {
+		return -1, -1, err
+	}
+	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.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall_TCGETS), uintptr(unsafe.Pointer(&oldState)), 0, 0, 0); err != 0 {
+		return nil, err
+	}
+
+	newState := oldState
+	newState.Lflag &^= syscall.ECHO
+	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall_TCSETS), uintptr(unsafe.Pointer(&newState)), 0, 0, 0); err != 0 {
+		return nil, err
+	}
+
+	defer func() {
+		syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall_TCSETS), uintptr(unsafe.Pointer(&oldState)), 0, 0, 0)
+	}()
+
+	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
+}
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