summaryrefslogtreecommitdiff
path: root/libgo/go/bytes/bytes.go
blob: 644bf75b894336ea9f7dae7c60ecd73e840d15e4 (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
// Copyright 2009 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 bytes implements functions for the manipulation of byte slices.
// It is analogous to the facilities of the strings package.
package bytes

import (
	"unicode"
	"unicode/utf8"
)

func equalPortable(a, b []byte) bool {
	if len(a) != len(b) {
		return false
	}
	for i, c := range a {
		if c != b[i] {
			return false
		}
	}
	return true
}

// explode splits s into a slice of UTF-8 sequences, one per Unicode character (still slices of bytes),
// up to a maximum of n byte slices. Invalid UTF-8 sequences are chopped into individual bytes.
func explode(s []byte, n int) [][]byte {
	if n <= 0 {
		n = len(s)
	}
	a := make([][]byte, n)
	var size int
	na := 0
	for len(s) > 0 {
		if na+1 >= n {
			a[na] = s
			na++
			break
		}
		_, size = utf8.DecodeRune(s)
		a[na] = s[0:size]
		s = s[size:]
		na++
	}
	return a[0:na]
}

// Count counts the number of non-overlapping instances of sep in s.
func Count(s, sep []byte) int {
	n := len(sep)
	if n == 0 {
		return utf8.RuneCount(s) + 1
	}
	if n > len(s) {
		return 0
	}
	count := 0
	c := sep[0]
	i := 0
	t := s[:len(s)-n+1]
	for i < len(t) {
		if t[i] != c {
			o := IndexByte(t[i:], c)
			if o < 0 {
				break
			}
			i += o
		}
		if n == 1 || Equal(s[i:i+n], sep) {
			count++
			i += n
			continue
		}
		i++
	}
	return count
}

// Contains reports whether subslice is within b.
func Contains(b, subslice []byte) bool {
	return Index(b, subslice) != -1
}

// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
func Index(s, sep []byte) int {
	n := len(sep)
	if n == 0 {
		return 0
	}
	if n > len(s) {
		return -1
	}
	c := sep[0]
	if n == 1 {
		return IndexByte(s, c)
	}
	i := 0
	t := s[:len(s)-n+1]
	for i < len(t) {
		if t[i] != c {
			o := IndexByte(t[i:], c)
			if o < 0 {
				break
			}
			i += o
		}
		if Equal(s[i:i+n], sep) {
			return i
		}
		i++
	}
	return -1
}

func indexBytePortable(s []byte, c byte) int {
	for i, b := range s {
		if b == c {
			return i
		}
	}
	return -1
}

// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
func LastIndex(s, sep []byte) int {
	n := len(sep)
	if n == 0 {
		return len(s)
	}
	c := sep[0]
	for i := len(s) - n; i >= 0; i-- {
		if s[i] == c && (n == 1 || Equal(s[i:i+n], sep)) {
			return i
		}
	}
	return -1
}

// IndexRune interprets s as a sequence of UTF-8-encoded Unicode code points.
// It returns the byte index of the first occurrence in s of the given rune.
// It returns -1 if rune is not present in s.
func IndexRune(s []byte, r rune) int {
	for i := 0; i < len(s); {
		r1, size := utf8.DecodeRune(s[i:])
		if r == r1 {
			return i
		}
		i += size
	}
	return -1
}

// IndexAny interprets s as a sequence of UTF-8-encoded Unicode code points.
// It returns the byte index of the first occurrence in s of any of the Unicode
// code points in chars.  It returns -1 if chars is empty or if there is no code
// point in common.
func IndexAny(s []byte, chars string) int {
	if len(chars) > 0 {
		var r rune
		var width int
		for i := 0; i < len(s); i += width {
			r = rune(s[i])
			if r < utf8.RuneSelf {
				width = 1
			} else {
				r, width = utf8.DecodeRune(s[i:])
			}
			for _, ch := range chars {
				if r == ch {
					return i
				}
			}
		}
	}
	return -1
}

// LastIndexAny interprets s as a sequence of UTF-8-encoded Unicode code
// points.  It returns the byte index of the last occurrence in s of any of
// the Unicode code points in chars.  It returns -1 if chars is empty or if
// there is no code point in common.
func LastIndexAny(s []byte, chars string) int {
	if len(chars) > 0 {
		for i := len(s); i > 0; {
			r, size := utf8.DecodeLastRune(s[0:i])
			i -= size
			for _, ch := range chars {
				if r == ch {
					return i
				}
			}
		}
	}
	return -1
}

// Generic split: splits after each instance of sep,
// including sepSave bytes of sep in the subslices.
func genSplit(s, sep []byte, sepSave, n int) [][]byte {
	if n == 0 {
		return nil
	}
	if len(sep) == 0 {
		return explode(s, n)
	}
	if n < 0 {
		n = Count(s, sep) + 1
	}
	c := sep[0]
	start := 0
	a := make([][]byte, n)
	na := 0
	for i := 0; i+len(sep) <= len(s) && na+1 < n; i++ {
		if s[i] == c && (len(sep) == 1 || Equal(s[i:i+len(sep)], sep)) {
			a[na] = s[start : i+sepSave]
			na++
			start = i + len(sep)
			i += len(sep) - 1
		}
	}
	a[na] = s[start:]
	return a[0 : na+1]
}

// SplitN slices s into subslices separated by sep and returns a slice of
// the subslices between those separators.
// If sep is empty, SplitN splits after each UTF-8 sequence.
// The count determines the number of subslices to return:
//   n > 0: at most n subslices; the last subslice will be the unsplit remainder.
//   n == 0: the result is nil (zero subslices)
//   n < 0: all subslices
func SplitN(s, sep []byte, n int) [][]byte { return genSplit(s, sep, 0, n) }

// SplitAfterN slices s into subslices after each instance of sep and
// returns a slice of those subslices.
// If sep is empty, SplitAfterN splits after each UTF-8 sequence.
// The count determines the number of subslices to return:
//   n > 0: at most n subslices; the last subslice will be the unsplit remainder.
//   n == 0: the result is nil (zero subslices)
//   n < 0: all subslices
func SplitAfterN(s, sep []byte, n int) [][]byte {
	return genSplit(s, sep, len(sep), n)
}

// Split slices s into all subslices separated by sep and returns a slice of
// the subslices between those separators.
// If sep is empty, Split splits after each UTF-8 sequence.
// It is equivalent to SplitN with a count of -1.
func Split(s, sep []byte) [][]byte { return genSplit(s, sep, 0, -1) }

// SplitAfter slices s into all subslices after each instance of sep and
// returns a slice of those subslices.
// If sep is empty, SplitAfter splits after each UTF-8 sequence.
// It is equivalent to SplitAfterN with a count of -1.
func SplitAfter(s, sep []byte) [][]byte {
	return genSplit(s, sep, len(sep), -1)
}

// Fields splits the slice s around each instance of one or more consecutive white space
// characters, returning a slice of subslices of s or an empty list if s contains only white space.
func Fields(s []byte) [][]byte {
	return FieldsFunc(s, unicode.IsSpace)
}

// FieldsFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
// It splits the slice s at each run of code points c satisfying f(c) and
// returns a slice of subslices of s.  If all code points in s satisfy f(c), or
// len(s) == 0, an empty slice is returned.
func FieldsFunc(s []byte, f func(rune) bool) [][]byte {
	n := 0
	inField := false
	for i := 0; i < len(s); {
		r, size := utf8.DecodeRune(s[i:])
		wasInField := inField
		inField = !f(r)
		if inField && !wasInField {
			n++
		}
		i += size
	}

	a := make([][]byte, n)
	na := 0
	fieldStart := -1
	for i := 0; i <= len(s) && na < n; {
		r, size := utf8.DecodeRune(s[i:])
		if fieldStart < 0 && size > 0 && !f(r) {
			fieldStart = i
			i += size
			continue
		}
		if fieldStart >= 0 && (size == 0 || f(r)) {
			a[na] = s[fieldStart:i]
			na++
			fieldStart = -1
		}
		if size == 0 {
			break
		}
		i += size
	}
	return a[0:na]
}

// Join concatenates the elements of s to create a new byte slice. The separator
// sep is placed between elements in the resulting slice.
func Join(s [][]byte, sep []byte) []byte {
	if len(s) == 0 {
		return []byte{}
	}
	if len(s) == 1 {
		// Just return a copy.
		return append([]byte(nil), s[0]...)
	}
	n := len(sep) * (len(s) - 1)
	for _, v := range s {
		n += len(v)
	}

	b := make([]byte, n)
	bp := copy(b, s[0])
	for _, v := range s[1:] {
		bp += copy(b[bp:], sep)
		bp += copy(b[bp:], v)
	}
	return b
}

// HasPrefix tests whether the byte slice s begins with prefix.
func HasPrefix(s, prefix []byte) bool {
	return len(s) >= len(prefix) && Equal(s[0:len(prefix)], prefix)
}

// HasSuffix tests whether the byte slice s ends with suffix.
func HasSuffix(s, suffix []byte) bool {
	return len(s) >= len(suffix) && Equal(s[len(s)-len(suffix):], suffix)
}

// Map returns a copy of the byte slice s with all its characters modified
// according to the mapping function. If mapping returns a negative value, the character is
// dropped from the string with no replacement.  The characters in s and the
// output are interpreted as UTF-8-encoded Unicode code points.
func Map(mapping func(r rune) rune, s []byte) []byte {
	// In the worst case, the slice can grow when mapped, making
	// things unpleasant.  But it's so rare we barge in assuming it's
	// fine.  It could also shrink but that falls out naturally.
	maxbytes := len(s) // length of b
	nbytes := 0        // number of bytes encoded in b
	b := make([]byte, maxbytes)
	for i := 0; i < len(s); {
		wid := 1
		r := rune(s[i])
		if r >= utf8.RuneSelf {
			r, wid = utf8.DecodeRune(s[i:])
		}
		r = mapping(r)
		if r >= 0 {
			if nbytes+utf8.RuneLen(r) > maxbytes {
				// Grow the buffer.
				maxbytes = maxbytes*2 + utf8.UTFMax
				nb := make([]byte, maxbytes)
				copy(nb, b[0:nbytes])
				b = nb
			}
			nbytes += utf8.EncodeRune(b[nbytes:maxbytes], r)
		}
		i += wid
	}
	return b[0:nbytes]
}

// Repeat returns a new byte slice consisting of count copies of b.
func Repeat(b []byte, count int) []byte {
	nb := make([]byte, len(b)*count)
	bp := 0
	for i := 0; i < count; i++ {
		bp += copy(nb[bp:], b)
	}
	return nb
}

// ToUpper returns a copy of the byte slice s with all Unicode letters mapped to their upper case.
func ToUpper(s []byte) []byte { return Map(unicode.ToUpper, s) }

// ToLower returns a copy of the byte slice s with all Unicode letters mapped to their lower case.
func ToLower(s []byte) []byte { return Map(unicode.ToLower, s) }

// ToTitle returns a copy of the byte slice s with all Unicode letters mapped to their title case.
func ToTitle(s []byte) []byte { return Map(unicode.ToTitle, s) }

// ToUpperSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
// upper case, giving priority to the special casing rules.
func ToUpperSpecial(_case unicode.SpecialCase, s []byte) []byte {
	return Map(func(r rune) rune { return _case.ToUpper(r) }, s)
}

// ToLowerSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
// lower case, giving priority to the special casing rules.
func ToLowerSpecial(_case unicode.SpecialCase, s []byte) []byte {
	return Map(func(r rune) rune { return _case.ToLower(r) }, s)
}

// ToTitleSpecial returns a copy of the byte slice s with all Unicode letters mapped to their
// title case, giving priority to the special casing rules.
func ToTitleSpecial(_case unicode.SpecialCase, s []byte) []byte {
	return Map(func(r rune) rune { return _case.ToTitle(r) }, s)
}

// isSeparator reports whether the rune could mark a word boundary.
// TODO: update when package unicode captures more of the properties.
func isSeparator(r rune) bool {
	// ASCII alphanumerics and underscore are not separators
	if r <= 0x7F {
		switch {
		case '0' <= r && r <= '9':
			return false
		case 'a' <= r && r <= 'z':
			return false
		case 'A' <= r && r <= 'Z':
			return false
		case r == '_':
			return false
		}
		return true
	}
	// Letters and digits are not separators
	if unicode.IsLetter(r) || unicode.IsDigit(r) {
		return false
	}
	// Otherwise, all we can do for now is treat spaces as separators.
	return unicode.IsSpace(r)
}

// Title returns a copy of s with all Unicode letters that begin words
// mapped to their title case.
//
// BUG: The rule Title uses for word boundaries does not handle Unicode punctuation properly.
func Title(s []byte) []byte {
	// Use a closure here to remember state.
	// Hackish but effective. Depends on Map scanning in order and calling
	// the closure once per rune.
	prev := ' '
	return Map(
		func(r rune) rune {
			if isSeparator(prev) {
				prev = r
				return unicode.ToTitle(r)
			}
			prev = r
			return r
		},
		s)
}

// TrimLeftFunc returns a subslice of s by slicing off all leading UTF-8-encoded
// Unicode code points c that satisfy f(c).
func TrimLeftFunc(s []byte, f func(r rune) bool) []byte {
	i := indexFunc(s, f, false)
	if i == -1 {
		return nil
	}
	return s[i:]
}

// TrimRightFunc returns a subslice of s by slicing off all trailing UTF-8
// encoded Unicode code points c that satisfy f(c).
func TrimRightFunc(s []byte, f func(r rune) bool) []byte {
	i := lastIndexFunc(s, f, false)
	if i >= 0 && s[i] >= utf8.RuneSelf {
		_, wid := utf8.DecodeRune(s[i:])
		i += wid
	} else {
		i++
	}
	return s[0:i]
}

// TrimFunc returns a subslice of s by slicing off all leading and trailing
// UTF-8-encoded Unicode code points c that satisfy f(c).
func TrimFunc(s []byte, f func(r rune) bool) []byte {
	return TrimRightFunc(TrimLeftFunc(s, f), f)
}

// TrimPrefix returns s without the provided leading prefix string.
// If s doesn't start with prefix, s is returned unchanged.
func TrimPrefix(s, prefix []byte) []byte {
	if HasPrefix(s, prefix) {
		return s[len(prefix):]
	}
	return s
}

// TrimSuffix returns s without the provided trailing suffix string.
// If s doesn't end with suffix, s is returned unchanged.
func TrimSuffix(s, suffix []byte) []byte {
	if HasSuffix(s, suffix) {
		return s[:len(s)-len(suffix)]
	}
	return s
}

// IndexFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
// It returns the byte index in s of the first Unicode
// code point satisfying f(c), or -1 if none do.
func IndexFunc(s []byte, f func(r rune) bool) int {
	return indexFunc(s, f, true)
}

// LastIndexFunc interprets s as a sequence of UTF-8-encoded Unicode code points.
// It returns the byte index in s of the last Unicode
// code point satisfying f(c), or -1 if none do.
func LastIndexFunc(s []byte, f func(r rune) bool) int {
	return lastIndexFunc(s, f, true)
}

// indexFunc is the same as IndexFunc except that if
// truth==false, the sense of the predicate function is
// inverted.
func indexFunc(s []byte, f func(r rune) bool, truth bool) int {
	start := 0
	for start < len(s) {
		wid := 1
		r := rune(s[start])
		if r >= utf8.RuneSelf {
			r, wid = utf8.DecodeRune(s[start:])
		}
		if f(r) == truth {
			return start
		}
		start += wid
	}
	return -1
}

// lastIndexFunc is the same as LastIndexFunc except that if
// truth==false, the sense of the predicate function is
// inverted.
func lastIndexFunc(s []byte, f func(r rune) bool, truth bool) int {
	for i := len(s); i > 0; {
		r, size := rune(s[i-1]), 1
		if r >= utf8.RuneSelf {
			r, size = utf8.DecodeLastRune(s[0:i])
		}
		i -= size
		if f(r) == truth {
			return i
		}
	}
	return -1
}

func makeCutsetFunc(cutset string) func(r rune) bool {
	return func(r rune) bool {
		for _, c := range cutset {
			if c == r {
				return true
			}
		}
		return false
	}
}

// Trim returns a subslice of s by slicing off all leading and
// trailing UTF-8-encoded Unicode code points contained in cutset.
func Trim(s []byte, cutset string) []byte {
	return TrimFunc(s, makeCutsetFunc(cutset))
}

// TrimLeft returns a subslice of s by slicing off all leading
// UTF-8-encoded Unicode code points contained in cutset.
func TrimLeft(s []byte, cutset string) []byte {
	return TrimLeftFunc(s, makeCutsetFunc(cutset))
}

// TrimRight returns a subslice of s by slicing off all trailing
// UTF-8-encoded Unicode code points that are contained in cutset.
func TrimRight(s []byte, cutset string) []byte {
	return TrimRightFunc(s, makeCutsetFunc(cutset))
}

// TrimSpace returns a subslice of s by slicing off all leading and
// trailing white space, as defined by Unicode.
func TrimSpace(s []byte) []byte {
	return TrimFunc(s, unicode.IsSpace)
}

// Runes returns a slice of runes (Unicode code points) equivalent to s.
func Runes(s []byte) []rune {
	t := make([]rune, utf8.RuneCount(s))
	i := 0
	for len(s) > 0 {
		r, l := utf8.DecodeRune(s)
		t[i] = r
		i++
		s = s[l:]
	}
	return t
}

// Replace returns a copy of the slice s with the first n
// non-overlapping instances of old replaced by new.
// If n < 0, there is no limit on the number of replacements.
func Replace(s, old, new []byte, n int) []byte {
	m := 0
	if n != 0 {
		// Compute number of replacements.
		m = Count(s, old)
	}
	if m == 0 {
		// Just return a copy.
		return append([]byte(nil), s...)
	}
	if n < 0 || m < n {
		n = m
	}

	// Apply replacements to buffer.
	t := make([]byte, len(s)+n*(len(new)-len(old)))
	w := 0
	start := 0
	for i := 0; i < n; i++ {
		j := start
		if len(old) == 0 {
			if i > 0 {
				_, wid := utf8.DecodeRune(s[start:])
				j += wid
			}
		} else {
			j += Index(s[start:], old)
		}
		w += copy(t[w:], s[start:j])
		w += copy(t[w:], new)
		start = j + len(old)
	}
	w += copy(t[w:], s[start:])
	return t[0:w]
}

// EqualFold reports whether s and t, interpreted as UTF-8 strings,
// are equal under Unicode case-folding.
func EqualFold(s, t []byte) bool {
	for len(s) != 0 && len(t) != 0 {
		// Extract first rune from each.
		var sr, tr rune
		if s[0] < utf8.RuneSelf {
			sr, s = rune(s[0]), s[1:]
		} else {
			r, size := utf8.DecodeRune(s)
			sr, s = r, s[size:]
		}
		if t[0] < utf8.RuneSelf {
			tr, t = rune(t[0]), t[1:]
		} else {
			r, size := utf8.DecodeRune(t)
			tr, t = r, t[size:]
		}

		// If they match, keep going; if not, return false.

		// Easy case.
		if tr == sr {
			continue
		}

		// Make sr < tr to simplify what follows.
		if tr < sr {
			tr, sr = sr, tr
		}
		// Fast check for ASCII.
		if tr < utf8.RuneSelf && 'A' <= sr && sr <= 'Z' {
			// ASCII, and sr is upper case.  tr must be lower case.
			if tr == sr+'a'-'A' {
				continue
			}
			return false
		}

		// General case.  SimpleFold(x) returns the next equivalent rune > x
		// or wraps around to smaller values.
		r := unicode.SimpleFold(sr)
		for r != sr && r < tr {
			r = unicode.SimpleFold(r)
		}
		if r == tr {
			continue
		}
		return false
	}

	// One string is empty.  Are both?
	return len(s) == len(t)
}