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
|
// Package difflib is a partial port of Python difflib module.
//
// It provides tools to compare sequences of strings and generate textual diffs.
//
// The following class and functions have been ported:
//
// - SequenceMatcher
//
// - unified_diff
//
// - context_diff
//
// Getting unified diffs was the main goal of the port. Keep in mind this code
// is mostly suitable to output text differences in a human friendly way, there
// are no guarantees generated diffs are consumable by patch(1).
package difflib
import (
"bufio"
"bytes"
"fmt"
"io"
"strings"
)
func min(a, b int) int {
if a < b {
return a
}
return b
}
func max(a, b int) int {
if a > b {
return a
}
return b
}
func calculateRatio(matches, length int) float64 {
if length > 0 {
return 2.0 * float64(matches) / float64(length)
}
return 1.0
}
type Match struct {
A int
B int
Size int
}
type OpCode struct {
Tag byte
I1 int
I2 int
J1 int
J2 int
}
// SequenceMatcher compares sequence of strings. The basic
// algorithm predates, and is a little fancier than, an algorithm
// published in the late 1980's by Ratcliff and Obershelp under the
// hyperbolic name "gestalt pattern matching". The basic idea is to find
// the longest contiguous matching subsequence that contains no "junk"
// elements (R-O doesn't address junk). The same idea is then applied
// recursively to the pieces of the sequences to the left and to the right
// of the matching subsequence. This does not yield minimal edit
// sequences, but does tend to yield matches that "look right" to people.
//
// SequenceMatcher tries to compute a "human-friendly diff" between two
// sequences. Unlike e.g. UNIX(tm) diff, the fundamental notion is the
// longest *contiguous* & junk-free matching subsequence. That's what
// catches peoples' eyes. The Windows(tm) windiff has another interesting
// notion, pairing up elements that appear uniquely in each sequence.
// That, and the method here, appear to yield more intuitive difference
// reports than does diff. This method appears to be the least vulnerable
// to synching up on blocks of "junk lines", though (like blank lines in
// ordinary text files, or maybe "<P>" lines in HTML files). That may be
// because this is the only method of the 3 that has a *concept* of
// "junk" <wink>.
//
// Timing: Basic R-O is cubic time worst case and quadratic time expected
// case. SequenceMatcher is quadratic time for the worst case and has
// expected-case behavior dependent in a complicated way on how many
// elements the sequences have in common; best case time is linear.
type SequenceMatcher struct {
a []string
b []string
b2j map[string][]int
IsJunk func(string) bool
autoJunk bool
bJunk map[string]struct{}
matchingBlocks []Match
fullBCount map[string]int
bPopular map[string]struct{}
opCodes []OpCode
}
func NewMatcher(a, b []string) *SequenceMatcher {
m := SequenceMatcher{autoJunk: true}
m.SetSeqs(a, b)
return &m
}
func NewMatcherWithJunk(a, b []string, autoJunk bool,
isJunk func(string) bool) *SequenceMatcher {
m := SequenceMatcher{IsJunk: isJunk, autoJunk: autoJunk}
m.SetSeqs(a, b)
return &m
}
// Set two sequences to be compared.
func (m *SequenceMatcher) SetSeqs(a, b []string) {
m.SetSeq1(a)
m.SetSeq2(b)
}
// Set the first sequence to be compared. The second sequence to be compared is
// not changed.
//
// SequenceMatcher computes and caches detailed information about the second
// sequence, so if you want to compare one sequence S against many sequences,
// use .SetSeq2(s) once and call .SetSeq1(x) repeatedly for each of the other
// sequences.
//
// See also SetSeqs() and SetSeq2().
func (m *SequenceMatcher) SetSeq1(a []string) {
if &a == &m.a {
return
}
m.a = a
m.matchingBlocks = nil
m.opCodes = nil
}
// Set the second sequence to be compared. The first sequence to be compared is
// not changed.
func (m *SequenceMatcher) SetSeq2(b []string) {
if &b == &m.b {
return
}
m.b = b
m.matchingBlocks = nil
m.opCodes = nil
m.fullBCount = nil
m.chainB()
}
func (m *SequenceMatcher) chainB() {
// Populate line -> index mapping
b2j := map[string][]int{}
for i, s := range m.b {
indices := b2j[s]
indices = append(indices, i)
b2j[s] = indices
}
// Purge junk elements
m.bJunk = map[string]struct{}{}
if m.IsJunk != nil {
junk := m.bJunk
for s, _ := range b2j {
if m.IsJunk(s) {
junk[s] = struct{}{}
}
}
for s, _ := range junk {
delete(b2j, s)
}
}
// Purge remaining popular elements
popular := map[string]struct{}{}
n := len(m.b)
if m.autoJunk && n >= 200 {
ntest := n/100 + 1
for s, indices := range b2j {
if len(indices) > ntest {
popular[s] = struct{}{}
}
}
for s, _ := range popular {
delete(b2j, s)
}
}
m.bPopular = popular
m.b2j = b2j
}
func (m *SequenceMatcher) isBJunk(s string) bool {
_, ok := m.bJunk[s]
return ok
}
// Find longest matching block in a[alo:ahi] and b[blo:bhi].
//
// If IsJunk is not defined:
//
// Return (i,j,k) such that a[i:i+k] is equal to b[j:j+k], where
// alo <= i <= i+k <= ahi
// blo <= j <= j+k <= bhi
// and for all (i',j',k') meeting those conditions,
// k >= k'
// i <= i'
// and if i == i', j <= j'
//
// In other words, of all maximal matching blocks, return one that
// starts earliest in a, and of all those maximal matching blocks that
// start earliest in a, return the one that starts earliest in b.
//
// If IsJunk is defined, first the longest matching block is
// determined as above, but with the additional restriction that no
// junk element appears in the block. Then that block is extended as
// far as possible by matching (only) junk elements on both sides. So
// the resulting block never matches on junk except as identical junk
// happens to be adjacent to an "interesting" match.
//
// If no blocks match, return (alo, blo, 0).
func (m *SequenceMatcher) findLongestMatch(alo, ahi, blo, bhi int) Match {
// CAUTION: stripping common prefix or suffix would be incorrect.
// E.g.,
// ab
// acab
// Longest matching block is "ab", but if common prefix is
// stripped, it's "a" (tied with "b"). UNIX(tm) diff does so
// strip, so ends up claiming that ab is changed to acab by
// inserting "ca" in the middle. That's minimal but unintuitive:
// "it's obvious" that someone inserted "ac" at the front.
// Windiff ends up at the same place as diff, but by pairing up
// the unique 'b's and then matching the first two 'a's.
besti, bestj, bestsize := alo, blo, 0
// find longest junk-free match
// during an iteration of the loop, j2len[j] = length of longest
// junk-free match ending with a[i-1] and b[j]
j2len := map[int]int{}
for i := alo; i != ahi; i++ {
// look at all instances of a[i] in b; note that because
// b2j has no junk keys, the loop is skipped if a[i] is junk
newj2len := map[int]int{}
for _, j := range m.b2j[m.a[i]] {
// a[i] matches b[j]
if j < blo {
continue
}
if j >= bhi {
break
}
k := j2len[j-1] + 1
newj2len[j] = k
if k > bestsize {
besti, bestj, bestsize = i-k+1, j-k+1, k
}
}
j2len = newj2len
}
// Extend the best by non-junk elements on each end. In particular,
// "popular" non-junk elements aren't in b2j, which greatly speeds
// the inner loop above, but also means "the best" match so far
// doesn't contain any junk *or* popular non-junk elements.
for besti > alo && bestj > blo && !m.isBJunk(m.b[bestj-1]) &&
m.a[besti-1] == m.b[bestj-1] {
besti, bestj, bestsize = besti-1, bestj-1, bestsize+1
}
for besti+bestsize < ahi && bestj+bestsize < bhi &&
!m.isBJunk(m.b[bestj+bestsize]) &&
m.a[besti+bestsize] == m.b[bestj+bestsize] {
bestsize += 1
}
// Now that we have a wholly interesting match (albeit possibly
// empty!), we may as well suck up the matching junk on each
// side of it too. Can't think of a good reason not to, and it
// saves post-processing the (possibly considerable) expense of
// figuring out what to do with it. In the case of an empty
// interesting match, this is clearly the right thing to do,
// because no other kind of match is possible in the regions.
for besti > alo && bestj > blo && m.isBJunk(m.b[bestj-1]) &&
m.a[besti-1] == m.b[bestj-1] {
besti, bestj, bestsize = besti-1, bestj-1, bestsize+1
}
for besti+bestsize < ahi && bestj+bestsize < bhi &&
m.isBJunk(m.b[bestj+bestsize]) &&
m.a[besti+bestsize] == m.b[bestj+bestsize] {
bestsize += 1
}
return Match{A: besti, B: bestj, Size: bestsize}
}
// Return list of triples describing matching subsequences.
//
// Each triple is of the form (i, j, n), and means that
// a[i:i+n] == b[j:j+n]. The triples are monotonically increasing in
// i and in j. It's also guaranteed that if (i, j, n) and (i', j', n') are
// adjacent triples in the list, and the second is not the last triple in the
// list, then i+n != i' or j+n != j'. IOW, adjacent triples never describe
// adjacent equal blocks.
//
// The last triple is a dummy, (len(a), len(b), 0), and is the only
// triple with n==0.
func (m *SequenceMatcher) GetMatchingBlocks() []Match {
if m.matchingBlocks != nil {
return m.matchingBlocks
}
var matchBlocks func(alo, ahi, blo, bhi int, matched []Match) []Match
matchBlocks = func(alo, ahi, blo, bhi int, matched []Match) []Match {
match := m.findLongestMatch(alo, ahi, blo, bhi)
i, j, k := match.A, match.B, match.Size
if match.Size > 0 {
if alo < i && blo < j {
matched = matchBlocks(alo, i, blo, j, matched)
}
matched = append(matched, match)
if i+k < ahi && j+k < bhi {
matched = matchBlocks(i+k, ahi, j+k, bhi, matched)
}
}
return matched
}
matched := matchBlocks(0, len(m.a), 0, len(m.b), nil)
// It's possible that we have adjacent equal blocks in the
// matching_blocks list now.
nonAdjacent := []Match{}
i1, j1, k1 := 0, 0, 0
for _, b := range matched {
// Is this block adjacent to i1, j1, k1?
i2, j2, k2 := b.A, b.B, b.Size
if i1+k1 == i2 && j1+k1 == j2 {
// Yes, so collapse them -- this just increases the length of
// the first block by the length of the second, and the first
// block so lengthened remains the block to compare against.
k1 += k2
} else {
// Not adjacent. Remember the first block (k1==0 means it's
// the dummy we started with), and make the second block the
// new block to compare against.
if k1 > 0 {
nonAdjacent = append(nonAdjacent, Match{i1, j1, k1})
}
i1, j1, k1 = i2, j2, k2
}
}
if k1 > 0 {
nonAdjacent = append(nonAdjacent, Match{i1, j1, k1})
}
nonAdjacent = append(nonAdjacent, Match{len(m.a), len(m.b), 0})
m.matchingBlocks = nonAdjacent
return m.matchingBlocks
}
// Return list of 5-tuples describing how to turn a into b.
//
// Each tuple is of the form (tag, i1, i2, j1, j2). The first tuple
// has i1 == j1 == 0, and remaining tuples have i1 == the i2 from the
// tuple preceding it, and likewise for j1 == the previous j2.
//
// The tags are characters, with these meanings:
//
// 'r' (replace): a[i1:i2] should be replaced by b[j1:j2]
//
// 'd' (delete): a[i1:i2] should be deleted, j1==j2 in this case.
//
// 'i' (insert): b[j1:j2] should be inserted at a[i1:i1], i1==i2 in this case.
//
// 'e' (equal): a[i1:i2] == b[j1:j2]
func (m *SequenceMatcher) GetOpCodes() []OpCode {
if m.opCodes != nil {
return m.opCodes
}
i, j := 0, 0
matching := m.GetMatchingBlocks()
opCodes := make([]OpCode, 0, len(matching))
for _, m := range matching {
// invariant: we've pumped out correct diffs to change
// a[:i] into b[:j], and the next matching block is
// a[ai:ai+size] == b[bj:bj+size]. So we need to pump
// out a diff to change a[i:ai] into b[j:bj], pump out
// the matching block, and move (i,j) beyond the match
ai, bj, size := m.A, m.B, m.Size
tag := byte(0)
if i < ai && j < bj {
tag = 'r'
} else if i < ai {
tag = 'd'
} else if j < bj {
tag = 'i'
}
if tag > 0 {
opCodes = append(opCodes, OpCode{tag, i, ai, j, bj})
}
i, j = ai+size, bj+size
// the list of matching blocks is terminated by a
// sentinel with size 0
if size > 0 {
opCodes = append(opCodes, OpCode{'e', ai, i, bj, j})
}
}
m.opCodes = opCodes
return m.opCodes
}
// Isolate change clusters by eliminating ranges with no changes.
//
// Return a generator of groups with up to n lines of context.
// Each group is in the same format as returned by GetOpCodes().
func (m *SequenceMatcher) GetGroupedOpCodes(n int) [][]OpCode {
if n < 0 {
n = 3
}
codes := m.GetOpCodes()
if len(codes) == 0 {
codes = []OpCode{OpCode{'e', 0, 1, 0, 1}}
}
// Fixup leading and trailing groups if they show no changes.
if codes[0].Tag == 'e' {
c := codes[0]
i1, i2, j1, j2 := c.I1, c.I2, c.J1, c.J2
codes[0] = OpCode{c.Tag, max(i1, i2-n), i2, max(j1, j2-n), j2}
}
if codes[len(codes)-1].Tag == 'e' {
c := codes[len(codes)-1]
i1, i2, j1, j2 := c.I1, c.I2, c.J1, c.J2
codes[len(codes)-1] = OpCode{c.Tag, i1, min(i2, i1+n), j1, min(j2, j1+n)}
}
nn := n + n
groups := [][]OpCode{}
group := []OpCode{}
for _, c := range codes {
i1, i2, j1, j2 := c.I1, c.I2, c.J1, c.J2
// End the current group and start a new one whenever
// there is a large range with no changes.
if c.Tag == 'e' && i2-i1 > nn {
group = append(group, OpCode{c.Tag, i1, min(i2, i1+n),
j1, min(j2, j1+n)})
groups = append(groups, group)
group = []OpCode{}
i1, j1 = max(i1, i2-n), max(j1, j2-n)
}
group = append(group, OpCode{c.Tag, i1, i2, j1, j2})
}
if len(group) > 0 && !(len(group) == 1 && group[0].Tag == 'e') {
groups = append(groups, group)
}
return groups
}
// Return a measure of the sequences' similarity (float in [0,1]).
//
// Where T is the total number of elements in both sequences, and
// M is the number of matches, this is 2.0*M / T.
// Note that this is 1 if the sequences are identical, and 0 if
// they have nothing in common.
//
// .Ratio() is expensive to compute if you haven't already computed
// .GetMatchingBlocks() or .GetOpCodes(), in which case you may
// want to try .QuickRatio() or .RealQuickRation() first to get an
// upper bound.
func (m *SequenceMatcher) Ratio() float64 {
matches := 0
for _, m := range m.GetMatchingBlocks() {
matches += m.Size
}
return calculateRatio(matches, len(m.a)+len(m.b))
}
// Return an upper bound on ratio() relatively quickly.
//
// This isn't defined beyond that it is an upper bound on .Ratio(), and
// is faster to compute.
func (m *SequenceMatcher) QuickRatio() float64 {
// viewing a and b as multisets, set matches to the cardinality
// of their intersection; this counts the number of matches
// without regard to order, so is clearly an upper bound
if m.fullBCount == nil {
m.fullBCount = map[string]int{}
for _, s := range m.b {
m.fullBCount[s] = m.fullBCount[s] + 1
}
}
// avail[x] is the number of times x appears in 'b' less the
// number of times we've seen it in 'a' so far ... kinda
avail := map[string]int{}
matches := 0
for _, s := range m.a {
n, ok := avail[s]
if !ok {
n = m.fullBCount[s]
}
avail[s] = n - 1
if n > 0 {
matches += 1
}
}
return calculateRatio(matches, len(m.a)+len(m.b))
}
// Return an upper bound on ratio() very quickly.
//
// This isn't defined beyond that it is an upper bound on .Ratio(), and
// is faster to compute than either .Ratio() or .QuickRatio().
func (m *SequenceMatcher) RealQuickRatio() float64 {
la, lb := len(m.a), len(m.b)
return calculateRatio(min(la, lb), la+lb)
}
// Convert range to the "ed" format
func formatRangeUnified(start, stop int) string {
// Per the diff spec at http://www.unix.org/single_unix_specification/
beginning := start + 1 // lines start numbering with one
length := stop - start
if length == 1 {
return fmt.Sprintf("%d", beginning)
}
if length == 0 {
beginning -= 1 // empty ranges begin at line just before the range
}
return fmt.Sprintf("%d,%d", beginning, length)
}
// Unified diff parameters
type UnifiedDiff struct {
A []string // First sequence lines
FromFile string // First file name
FromDate string // First file time
B []string // Second sequence lines
ToFile string // Second file name
ToDate string // Second file time
Eol string // Headers end of line, defaults to LF
Context int // Number of context lines
}
// Compare two sequences of lines; generate the delta as a unified diff.
//
// Unified diffs are a compact way of showing line changes and a few
// lines of context. The number of context lines is set by 'n' which
// defaults to three.
//
// By default, the diff control lines (those with ---, +++, or @@) are
// created with a trailing newline. This is helpful so that inputs
// created from file.readlines() result in diffs that are suitable for
// file.writelines() since both the inputs and outputs have trailing
// newlines.
//
// For inputs that do not have trailing newlines, set the lineterm
// argument to "" so that the output will be uniformly newline free.
//
// The unidiff format normally has a header for filenames and modification
// times. Any or all of these may be specified using strings for
// 'fromfile', 'tofile', 'fromfiledate', and 'tofiledate'.
// The modification times are normally expressed in the ISO 8601 format.
func WriteUnifiedDiff(writer io.Writer, diff UnifiedDiff) error {
buf := bufio.NewWriter(writer)
defer buf.Flush()
w := func(format string, args ...interface{}) error {
_, err := buf.WriteString(fmt.Sprintf(format, args...))
return err
}
if len(diff.Eol) == 0 {
diff.Eol = "\n"
}
started := false
m := NewMatcher(diff.A, diff.B)
for _, g := range m.GetGroupedOpCodes(diff.Context) {
if !started {
started = true
fromDate := ""
if len(diff.FromDate) > 0 {
fromDate = "\t" + diff.FromDate
}
toDate := ""
if len(diff.ToDate) > 0 {
toDate = "\t" + diff.ToDate
}
err := w("--- %s%s%s", diff.FromFile, fromDate, diff.Eol)
if err != nil {
return err
}
err = w("+++ %s%s%s", diff.ToFile, toDate, diff.Eol)
if err != nil {
return err
}
}
first, last := g[0], g[len(g)-1]
range1 := formatRangeUnified(first.I1, last.I2)
range2 := formatRangeUnified(first.J1, last.J2)
if err := w("@@ -%s +%s @@%s", range1, range2, diff.Eol); err != nil {
return err
}
for _, c := range g {
i1, i2, j1, j2 := c.I1, c.I2, c.J1, c.J2
if c.Tag == 'e' {
for _, line := range diff.A[i1:i2] {
if err := w(" " + line); err != nil {
return err
}
}
continue
}
if c.Tag == 'r' || c.Tag == 'd' {
for _, line := range diff.A[i1:i2] {
if err := w("-" + line); err != nil {
return err
}
}
}
if c.Tag == 'r' || c.Tag == 'i' {
for _, line := range diff.B[j1:j2] {
if err := w("+" + line); err != nil {
return err
}
}
}
}
}
return nil
}
// Like WriteUnifiedDiff but returns the diff a string.
func GetUnifiedDiffString(diff UnifiedDiff) (string, error) {
w := &bytes.Buffer{}
err := WriteUnifiedDiff(w, diff)
return string(w.Bytes()), err
}
// Convert range to the "ed" format.
func formatRangeContext(start, stop int) string {
// Per the diff spec at http://www.unix.org/single_unix_specification/
beginning := start + 1 // lines start numbering with one
length := stop - start
if length == 0 {
beginning -= 1 // empty ranges begin at line just before the range
}
if length <= 1 {
return fmt.Sprintf("%d", beginning)
}
return fmt.Sprintf("%d,%d", beginning, beginning+length-1)
}
type ContextDiff UnifiedDiff
// Compare two sequences of lines; generate the delta as a context diff.
//
// Context diffs are a compact way of showing line changes and a few
// lines of context. The number of context lines is set by diff.Context
// which defaults to three.
//
// By default, the diff control lines (those with *** or ---) are
// created with a trailing newline.
//
// For inputs that do not have trailing newlines, set the diff.Eol
// argument to "" so that the output will be uniformly newline free.
//
// The context diff format normally has a header for filenames and
// modification times. Any or all of these may be specified using
// strings for diff.FromFile, diff.ToFile, diff.FromDate, diff.ToDate.
// The modification times are normally expressed in the ISO 8601 format.
// If not specified, the strings default to blanks.
func WriteContextDiff(writer io.Writer, diff ContextDiff) error {
buf := bufio.NewWriter(writer)
defer buf.Flush()
var diffErr error
w := func(format string, args ...interface{}) {
_, err := buf.WriteString(fmt.Sprintf(format, args...))
if diffErr == nil && err != nil {
diffErr = err
}
}
if len(diff.Eol) == 0 {
diff.Eol = "\n"
}
prefix := map[byte]string{
'i': "+ ",
'd': "- ",
'r': "! ",
'e': " ",
}
started := false
m := NewMatcher(diff.A, diff.B)
for _, g := range m.GetGroupedOpCodes(diff.Context) {
if !started {
started = true
fromDate := ""
if len(diff.FromDate) > 0 {
fromDate = "\t" + diff.FromDate
}
toDate := ""
if len(diff.ToDate) > 0 {
toDate = "\t" + diff.ToDate
}
w("*** %s%s%s", diff.FromFile, fromDate, diff.Eol)
w("--- %s%s%s", diff.ToFile, toDate, diff.Eol)
}
first, last := g[0], g[len(g)-1]
w("***************" + diff.Eol)
range1 := formatRangeContext(first.I1, last.I2)
w("*** %s ****%s", range1, diff.Eol)
for _, c := range g {
if c.Tag == 'r' || c.Tag == 'd' {
for _, cc := range g {
if cc.Tag == 'i' {
continue
}
for _, line := range diff.A[cc.I1:cc.I2] {
w(prefix[cc.Tag] + line)
}
}
break
}
}
range2 := formatRangeContext(first.J1, last.J2)
w("--- %s ----%s", range2, diff.Eol)
for _, c := range g {
if c.Tag == 'r' || c.Tag == 'i' {
for _, cc := range g {
if cc.Tag == 'd' {
continue
}
for _, line := range diff.B[cc.J1:cc.J2] {
w(prefix[cc.Tag] + line)
}
}
break
}
}
}
return diffErr
}
// Like WriteContextDiff but returns the diff a string.
func GetContextDiffString(diff ContextDiff) (string, error) {
w := &bytes.Buffer{}
err := WriteContextDiff(w, diff)
return string(w.Bytes()), err
}
// Split a string on "\n" while preserving them. The output can be used
// as input for UnifiedDiff and ContextDiff structures.
func SplitLines(s string) []string {
lines := strings.SplitAfter(s, "\n")
lines[len(lines)-1] += "\n"
return lines
}
|