summaryrefslogtreecommitdiff
path: root/vendor/golang.org/x/term/terminal.go
blob: 535ab8257c415b552ab6aa92bcd7e196e783dbf2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
// 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 term

import (
	"bytes"
	"io"
	"runtime"
	"strconv"
	"sync"
	"unicode/utf8"
)

// 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 (in
	// bytes, as an index into |line|). If it returns ok=false, the key
	// press is processed normally. Otherwise it returns a replacement line
	// and the new cursor position.
	AutoCompleteCallback func(line string, pos int, key rune) (newLine string, newPos int, ok bool)

	// 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 []rune

	// line is the current line being entered.
	line []rune
	// pos is the logical position of the cursor in line
	pos int
	// echo is true if local echo is enabled
	echo bool
	// pasteActive is true iff there is a bracketed paste operation in
	// progress.
	pasteActive 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

	// history contains previously entered commands so that they can be
	// accessed with the up and down keys.
	history stRingBuffer
	// historyIndex stores the currently accessed history entry, where zero
	// means the immediately previous entry.
	historyIndex int
	// When navigating up and down the history it's possible to return to
	// the incomplete, initial line. That value is stored in
	// historyPending.
	historyPending string
}

// 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:       []rune(prompt),
		termWidth:    80,
		termHeight:   24,
		echo:         true,
		historyIndex: -1,
	}
}

const (
	keyCtrlC     = 3
	keyCtrlD     = 4
	keyCtrlU     = 21
	keyEnter     = '\r'
	keyEscape    = 27
	keyBackspace = 127
	keyUnknown   = 0xd800 /* UTF-16 surrogate area */ + iota
	keyUp
	keyDown
	keyLeft
	keyRight
	keyAltLeft
	keyAltRight
	keyHome
	keyEnd
	keyDeleteWord
	keyDeleteLine
	keyClearScreen
	keyPasteStart
	keyPasteEnd
)

var (
	crlf       = []byte{'\r', '\n'}
	pasteStart = []byte{keyEscape, '[', '2', '0', '0', '~'}
	pasteEnd   = []byte{keyEscape, '[', '2', '0', '1', '~'}
)

// bytesToKey tries to parse a key sequence from b. If successful, it returns
// the key and the remainder of the input. Otherwise it returns utf8.RuneError.
func bytesToKey(b []byte, pasteActive bool) (rune, []byte) {
	if len(b) == 0 {
		return utf8.RuneError, nil
	}

	if !pasteActive {
		switch b[0] {
		case 1: // ^A
			return keyHome, b[1:]
		case 2: // ^B
			return keyLeft, b[1:]
		case 5: // ^E
			return keyEnd, b[1:]
		case 6: // ^F
			return keyRight, b[1:]
		case 8: // ^H
			return keyBackspace, b[1:]
		case 11: // ^K
			return keyDeleteLine, b[1:]
		case 12: // ^L
			return keyClearScreen, b[1:]
		case 23: // ^W
			return keyDeleteWord, b[1:]
		case 14: // ^N
			return keyDown, b[1:]
		case 16: // ^P
			return keyUp, b[1:]
		}
	}

	if b[0] != keyEscape {
		if !utf8.FullRune(b) {
			return utf8.RuneError, b
		}
		r, l := utf8.DecodeRune(b)
		return r, b[l:]
	}

	if !pasteActive && 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:]
		case 'H':
			return keyHome, b[3:]
		case 'F':
			return keyEnd, b[3:]
		}
	}

	if !pasteActive && 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 !pasteActive && len(b) >= 6 && bytes.Equal(b[:6], pasteStart) {
		return keyPasteStart, b[6:]
	}

	if pasteActive && len(b) >= 6 && bytes.Equal(b[:6], pasteEnd) {
		return keyPasteEnd, 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' || c == '~' {
			return keyUnknown, b[i+1:]
		}
	}

	return utf8.RuneError, b
}

// queue appends data to the end of t.outBuf
func (t *Terminal) queue(data []rune) {
	t.outBuf = append(t.outBuf, []byte(string(data))...)
}

var eraseUnderCursor = []rune{' ', keyEscape, '[', 'D'}
var space = []rune{' '}

func isPrintable(key rune) bool {
	isInSurrogateArea := key >= 0xd800 && key <= 0xdbff
	return key >= 32 && !isInSurrogateArea
}

// 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 := visualLength(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) {
	m := []rune{}

	// 1 unit up can be expressed as ^[[A or ^[A
	// 5 units up can be expressed as ^[[5A

	if up == 1 {
		m = append(m, keyEscape, '[', 'A')
	} else if up > 1 {
		m = append(m, keyEscape, '[')
		m = append(m, []rune(strconv.Itoa(up))...)
		m = append(m, 'A')
	}

	if down == 1 {
		m = append(m, keyEscape, '[', 'B')
	} else if down > 1 {
		m = append(m, keyEscape, '[')
		m = append(m, []rune(strconv.Itoa(down))...)
		m = append(m, 'B')
	}

	if right == 1 {
		m = append(m, keyEscape, '[', 'C')
	} else if right > 1 {
		m = append(m, keyEscape, '[')
		m = append(m, []rune(strconv.Itoa(right))...)
		m = append(m, 'C')
	}

	if left == 1 {
		m = append(m, keyEscape, '[', 'D')
	} else if left > 1 {
		m = append(m, keyEscape, '[')
		m = append(m, []rune(strconv.Itoa(left))...)
		m = append(m, 'D')
	}

	t.queue(m)
}

func (t *Terminal) clearLineToRight() {
	op := []rune{keyEscape, '[', 'K'}
	t.queue(op)
}

const maxLineLength = 4096

func (t *Terminal) setLine(newLine []rune, newPos int) {
	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
}

func (t *Terminal) advanceCursor(places int) {
	t.cursorX += places
	t.cursorY += t.cursorX / t.termWidth
	if t.cursorY > t.maxLine {
		t.maxLine = t.cursorY
	}
	t.cursorX = t.cursorX % t.termWidth

	if places > 0 && t.cursorX == 0 {
		// Normally terminals will advance the current position
		// when writing a character. But that doesn't happen
		// for the last character in a line. However, when
		// writing a character (except a new line) that causes
		// a line wrap, the position will be advanced two
		// places.
		//
		// So, if we are stopping at the end of a line, we
		// need to write a newline so that our cursor can be
		// advanced to the next line.
		t.outBuf = append(t.outBuf, '\r', '\n')
	}
}

func (t *Terminal) eraseNPreviousChars(n int) {
	if n == 0 {
		return
	}

	if t.pos < n {
		n = t.pos
	}
	t.pos -= n
	t.moveCursorToPos(t.pos)

	copy(t.line[t.pos:], t.line[n+t.pos:])
	t.line = t.line[:len(t.line)-n]
	if t.echo {
		t.writeLine(t.line[t.pos:])
		for i := 0; i < n; i++ {
			t.queue(space)
		}
		t.advanceCursor(n)
		t.moveCursorToPos(t.pos)
	}
}

// countToLeftWord returns then number of characters from the cursor to the
// start of the previous word.
func (t *Terminal) countToLeftWord() int {
	if t.pos == 0 {
		return 0
	}

	pos := t.pos - 1
	for pos > 0 {
		if t.line[pos] != ' ' {
			break
		}
		pos--
	}
	for pos > 0 {
		if t.line[pos] == ' ' {
			pos++
			break
		}
		pos--
	}

	return t.pos - pos
}

// countToRightWord returns then number of characters from the cursor to the
// start of the next word.
func (t *Terminal) countToRightWord() int {
	pos := t.pos
	for pos < len(t.line) {
		if t.line[pos] == ' ' {
			break
		}
		pos++
	}
	for pos < len(t.line) {
		if t.line[pos] != ' ' {
			break
		}
		pos++
	}
	return pos - t.pos
}

// visualLength returns the number of visible glyphs in s.
func visualLength(runes []rune) int {
	inEscapeSeq := false
	length := 0

	for _, r := range runes {
		switch {
		case inEscapeSeq:
			if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') {
				inEscapeSeq = false
			}
		case r == '\x1b':
			inEscapeSeq = true
		default:
			length++
		}
	}

	return length
}

// handleKey processes the given key and, optionally, returns a line of text
// that the user has entered.
func (t *Terminal) handleKey(key rune) (line string, ok bool) {
	if t.pasteActive && key != keyEnter {
		t.addKeyToLine(key)
		return
	}

	switch key {
	case keyBackspace:
		if t.pos == 0 {
			return
		}
		t.eraseNPreviousChars(1)
	case keyAltLeft:
		// move left by a word.
		t.pos -= t.countToLeftWord()
		t.moveCursorToPos(t.pos)
	case keyAltRight:
		// move right by a word.
		t.pos += t.countToRightWord()
		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 keyHome:
		if t.pos == 0 {
			return
		}
		t.pos = 0
		t.moveCursorToPos(t.pos)
	case keyEnd:
		if t.pos == len(t.line) {
			return
		}
		t.pos = len(t.line)
		t.moveCursorToPos(t.pos)
	case keyUp:
		entry, ok := t.history.NthPreviousEntry(t.historyIndex + 1)
		if !ok {
			return "", false
		}
		if t.historyIndex == -1 {
			t.historyPending = string(t.line)
		}
		t.historyIndex++
		runes := []rune(entry)
		t.setLine(runes, len(runes))
	case keyDown:
		switch t.historyIndex {
		case -1:
			return
		case 0:
			runes := []rune(t.historyPending)
			t.setLine(runes, len(runes))
			t.historyIndex--
		default:
			entry, ok := t.history.NthPreviousEntry(t.historyIndex - 1)
			if ok {
				t.historyIndex--
				runes := []rune(entry)
				t.setLine(runes, len(runes))
			}
		}
	case keyEnter:
		t.moveCursorToPos(len(t.line))
		t.queue([]rune("\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
	case keyDeleteWord:
		// Delete zero or more spaces and then one or more characters.
		t.eraseNPreviousChars(t.countToLeftWord())
	case keyDeleteLine:
		// Delete everything from the current cursor position to the
		// end of line.
		for i := t.pos; i < len(t.line); i++ {
			t.queue(space)
			t.advanceCursor(1)
		}
		t.line = t.line[:t.pos]
		t.moveCursorToPos(t.pos)
	case keyCtrlD:
		// Erase the character under the current position.
		// The EOF case when the line is empty is handled in
		// readLine().
		if t.pos < len(t.line) {
			t.pos++
			t.eraseNPreviousChars(1)
		}
	case keyCtrlU:
		t.eraseNPreviousChars(t.pos)
	case keyClearScreen:
		// Erases the screen and moves the cursor to the home position.
		t.queue([]rune("\x1b[2J\x1b[H"))
		t.queue(t.prompt)
		t.cursorX, t.cursorY = 0, 0
		t.advanceCursor(visualLength(t.prompt))
		t.setLine(t.line, t.pos)
	default:
		if t.AutoCompleteCallback != nil {
			prefix := string(t.line[:t.pos])
			suffix := string(t.line[t.pos:])

			t.lock.Unlock()
			newLine, newPos, completeOk := t.AutoCompleteCallback(prefix+suffix, len(prefix), key)
			t.lock.Lock()

			if completeOk {
				t.setLine([]rune(newLine), utf8.RuneCount([]byte(newLine)[:newPos]))
				return
			}
		}
		if !isPrintable(key) {
			return
		}
		if len(t.line) == maxLineLength {
			return
		}
		t.addKeyToLine(key)
	}
	return
}

// addKeyToLine inserts the given key at the current position in the current
// line.
func (t *Terminal) addKeyToLine(key rune) {
	if len(t.line) == cap(t.line) {
		newLine := make([]rune, 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] = key
	if t.echo {
		t.writeLine(t.line[t.pos:])
	}
	t.pos++
	t.moveCursorToPos(t.pos)
}

func (t *Terminal) writeLine(line []rune) {
	for len(line) != 0 {
		remainingOnLine := t.termWidth - t.cursorX
		todo := len(line)
		if todo > remainingOnLine {
			todo = remainingOnLine
		}
		t.queue(line[:todo])
		t.advanceCursor(visualLength(line[:todo]))
		line = line[todo:]
	}
}

// writeWithCRLF writes buf to w but replaces all occurrences of \n with \r\n.
func writeWithCRLF(w io.Writer, buf []byte) (n int, err error) {
	for len(buf) > 0 {
		i := bytes.IndexByte(buf, '\n')
		todo := len(buf)
		if i >= 0 {
			todo = i
		}

		var nn int
		nn, err = w.Write(buf[:todo])
		n += nn
		if err != nil {
			return n, err
		}
		buf = buf[todo:]

		if i >= 0 {
			if _, err = w.Write(crlf); err != nil {
				return n, err
			}
			n++
			buf = buf[1:]
		}
	}

	return n, nil
}

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 writeWithCRLF(t.c, 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 = writeWithCRLF(t.c, buf); err != nil {
		return
	}

	t.writeLine(t.prompt)
	if t.echo {
		t.writeLine(t.line)
	}

	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 = []rune(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(t.prompt)
		t.c.Write(t.outBuf)
		t.outBuf = t.outBuf[:0]
	}

	lineIsPasted := t.pasteActive

	for {
		rest := t.remainder
		lineOk := false
		for !lineOk {
			var key rune
			key, rest = bytesToKey(rest, t.pasteActive)
			if key == utf8.RuneError {
				break
			}
			if !t.pasteActive {
				if key == keyCtrlD {
					if len(t.line) == 0 {
						return "", io.EOF
					}
				}
				if key == keyCtrlC {
					return "", io.EOF
				}
				if key == keyPasteStart {
					t.pasteActive = true
					if len(t.line) == 0 {
						lineIsPasted = true
					}
					continue
				}
			} else if key == keyPasteEnd {
				t.pasteActive = false
				continue
			}
			if !t.pasteActive {
				lineIsPasted = false
			}
			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 {
			if t.echo {
				t.historyIndex = -1
				t.history.Add(line)
			}
			if lineIsPasted {
				err = ErrPasteIndicator
			}
			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)]
	}
}

// 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 = []rune(prompt)
}

func (t *Terminal) clearAndRepaintLinePlusNPrevious(numPrevLines int) {
	// Move cursor to column zero at the start of the line.
	t.move(t.cursorY, 0, t.cursorX, 0)
	t.cursorX, t.cursorY = 0, 0
	t.clearLineToRight()
	for t.cursorY < numPrevLines {
		// Move down a line
		t.move(0, 1, 0, 0)
		t.cursorY++
		t.clearLineToRight()
	}
	// Move back to beginning.
	t.move(t.cursorY, 0, 0, 0)
	t.cursorX, t.cursorY = 0, 0

	t.queue(t.prompt)
	t.advanceCursor(visualLength(t.prompt))
	t.writeLine(t.line)
	t.moveCursorToPos(t.pos)
}

func (t *Terminal) SetSize(width, height int) error {
	t.lock.Lock()
	defer t.lock.Unlock()

	if width == 0 {
		width = 1
	}

	oldWidth := t.termWidth
	t.termWidth, t.termHeight = width, height

	switch {
	case width == oldWidth:
		// If the width didn't change then nothing else needs to be
		// done.
		return nil
	case len(t.line) == 0 && t.cursorX == 0 && t.cursorY == 0:
		// If there is nothing on current line and no prompt printed,
		// just do nothing
		return nil
	case width < oldWidth:
		// Some terminals (e.g. xterm) will truncate lines that were
		// too long when shinking. Others, (e.g. gnome-terminal) will
		// attempt to wrap them. For the former, repainting t.maxLine
		// works great, but that behaviour goes badly wrong in the case
		// of the latter because they have doubled every full line.

		// We assume that we are working on a terminal that wraps lines
		// and adjust the cursor position based on every previous line
		// wrapping and turning into two. This causes the prompt on
		// xterms to move upwards, which isn't great, but it avoids a
		// huge mess with gnome-terminal.
		if t.cursorX >= t.termWidth {
			t.cursorX = t.termWidth - 1
		}
		t.cursorY *= 2
		t.clearAndRepaintLinePlusNPrevious(t.maxLine * 2)
	case width > oldWidth:
		// If the terminal expands then our position calculations will
		// be wrong in the future because we think the cursor is
		// |t.pos| chars into the string, but there will be a gap at
		// the end of any wrapped line.
		//
		// But the position will actually be correct until we move, so
		// we can move back to the beginning and repaint everything.
		t.clearAndRepaintLinePlusNPrevious(t.maxLine)
	}

	_, err := t.c.Write(t.outBuf)
	t.outBuf = t.outBuf[:0]
	return err
}

type pasteIndicatorError struct{}

func (pasteIndicatorError) Error() string {
	return "terminal: ErrPasteIndicator not correctly handled"
}

// ErrPasteIndicator may be returned from ReadLine as the error, in addition
// to valid line data. It indicates that bracketed paste mode is enabled and
// that the returned line consists only of pasted data. Programs may wish to
// interpret pasted data more literally than typed data.
var ErrPasteIndicator = pasteIndicatorError{}

// SetBracketedPasteMode requests that the terminal bracket paste operations
// with markers. Not all terminals support this but, if it is supported, then
// enabling this mode will stop any autocomplete callback from running due to
// pastes. Additionally, any lines that are completely pasted will be returned
// from ReadLine with the error set to ErrPasteIndicator.
func (t *Terminal) SetBracketedPasteMode(on bool) {
	if on {
		io.WriteString(t.c, "\x1b[?2004h")
	} else {
		io.WriteString(t.c, "\x1b[?2004l")
	}
}

// stRingBuffer is a ring buffer of strings.
type stRingBuffer struct {
	// entries contains max elements.
	entries []string
	max     int
	// head contains the index of the element most recently added to the ring.
	head int
	// size contains the number of elements in the ring.
	size int
}

func (s *stRingBuffer) Add(a string) {
	if s.entries == nil {
		const defaultNumEntries = 100
		s.entries = make([]string, defaultNumEntries)
		s.max = defaultNumEntries
	}

	s.head = (s.head + 1) % s.max
	s.entries[s.head] = a
	if s.size < s.max {
		s.size++
	}
}

// NthPreviousEntry returns the value passed to the nth previous call to Add.
// If n is zero then the immediately prior value is returned, if one, then the
// next most recent, and so on. If such an element doesn't exist then ok is
// false.
func (s *stRingBuffer) NthPreviousEntry(n int) (value string, ok bool) {
	if n >= s.size {
		return "", false
	}
	index := s.head - n
	if index < 0 {
		index += s.max
	}
	return s.entries[index], true
}

// readPasswordLine reads from reader until it finds \n or io.EOF.
// The slice returned does not include the \n.
// readPasswordLine also ignores any \r it finds.
// Windows uses \r as end of line. So, on Windows, readPasswordLine
// reads until it finds \r and ignores any \n it finds during processing.
func readPasswordLine(reader io.Reader) ([]byte, error) {
	var buf [1]byte
	var ret []byte

	for {
		n, err := reader.Read(buf[:])
		if n > 0 {
			switch buf[0] {
			case '\b':
				if len(ret) > 0 {
					ret = ret[:len(ret)-1]
				}
			case '\n':
				if runtime.GOOS != "windows" {
					return ret, nil
				}
				// otherwise ignore \n
			case '\r':
				if runtime.GOOS == "windows" {
					return ret, nil
				}
				// otherwise ignore \r
			default:
				ret = append(ret, buf[0])
			}
			continue
		}
		if err != nil {
			if err == io.EOF && len(ret) > 0 {
				return ret, nil
			}
			return ret, err
		}
	}
}