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difflib.go
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difflib.go
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// 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"
"errors"
"fmt"
"io"
"strings"
"unicode"
)
func calculateRatio(matches, length int) float64 {
if length > 0 {
return 2.0 * float64(matches) / float64(length)
}
return 1.0
}
func listifyString(str string) (lst []string) {
lst = make([]string, len(str))
for i, c := range str {
lst[i] = string(c)
}
return lst
}
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]bool
matchingBlocks []Match
fullBCount map[string]int
bPopular map[string]bool
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
}
// SetSeqs sets two sequences to be compared.
func (m *SequenceMatcher) SetSeqs(a, b []string) {
m.SetSeq1(a)
m.SetSeq2(b)
}
// SetSeq1 sets 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
}
// SetSeq2 sets 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{}
junk := map[string]bool{}
popular := map[string]bool{}
ntest := len(m.b)
if m.autoJunk && ntest >= 200 {
ntest = ntest/100 + 1
}
for i, s := range m.b {
if !junk[s] {
if m.IsJunk != nil && m.IsJunk(s) {
junk[s] = true
} else if !popular[s] {
ids := append(b2j[s], i)
if len(ids) <= ntest {
b2j[s] = ids
} else {
delete(b2j, s)
popular[s] = true
}
}
}
}
m.b2j = b2j
m.bJunk = junk
m.bPopular = popular
}
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]
N := bhi - blo
j2len := make([]int, N)
newj2len := make([]int, N)
var indices []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
newindices := m.b2j[m.a[i]]
for _, j := range newindices {
// a[i] matches b[j]
if j < blo {
continue
}
if j >= bhi {
break
}
k := 1
if j > blo {
k = j2len[j-1-blo] + 1
}
newj2len[j-blo] = k
if k > bestsize {
besti, bestj, bestsize = i-k+1, j-k+1, k
}
}
// j2len = newj2len, clear and reuse j2len as newj2len
for _, j := range indices {
if j < blo {
continue
}
if j >= bhi {
break
}
j2len[j-blo] = 0
}
indices = newindices
j2len, newj2len = newj2len, j2len
}
// 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}
}
// GetMatchingBlocks returns a 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.
var 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
}
// GetOpCodes returns a 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
}
// GetGroupedOpCodes isolates 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{{'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
var (
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
}
// Ratio returns 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))
}
// QuickRatio returns 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))
}
// RealQuickRatio returns 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)
}
func count_leading(line string, ch byte) (count int) {
// Return number of `ch` characters at the start of `line`.
count = 0
n := len(line)
for (count < n) && (line[count] == ch) {
count++
}
return count
}
type DiffLine struct {
Tag byte
Line string
}
func NewDiffLine(tag byte, line string) (l DiffLine) {
l = DiffLine{}
l.Tag = tag
l.Line = line
return l
}
type Differ struct {
Linejunk func(string) bool
Charjunk func(string) bool
}
func NewDiffer() *Differ {
return &Differ{}
}
func (d *Differ) Compare(a []string, b []string) (diffs []string, err error) {
// Compare two sequences of lines; generate the resulting delta.
// Each sequence must contain individual single-line strings ending with
// newlines. Such sequences can be obtained from the `readlines()` method
// of file-like objects. The delta generated also consists of newline-
// terminated strings, ready to be printed as-is via the writeline()
// method of a file-like object.
diffs = []string{}
cruncher := NewMatcherWithJunk(a, b, true, d.Linejunk)
opcodes := cruncher.GetOpCodes()
for _, current := range opcodes {
alo := current.I1
ahi := current.I2
blo := current.J1
bhi := current.J2
var g []string
if current.Tag == 'r' {
g, _ = d.FancyReplace(a, alo, ahi, b, blo, bhi)
} else if current.Tag == 'd' {
g = d.Dump("-", a, alo, ahi)
} else if current.Tag == 'i' {
g = d.Dump("+", b, blo, bhi)
} else if current.Tag == 'e' {
g = d.Dump(" ", a, alo, ahi)
} else {
return nil, fmt.Errorf("unknown tag %q", current.Tag)
}
diffs = append(diffs, g...)
}
return diffs, nil
}
func (d *Differ) StructuredDump(tag byte, x []string, low int, high int) (out []DiffLine) {
size := high - low
out = make([]DiffLine, size)
for i := 0; i < size; i++ {
out[i] = NewDiffLine(tag, x[i+low])
}
return out
}
func (d *Differ) Dump(tag string, x []string, low int, high int) (out []string) {
// Generate comparison results for a same-tagged range.
sout := d.StructuredDump(tag[0], x, low, high)
out = make([]string, len(sout))
var bld strings.Builder
bld.Grow(1024)
for i, line := range sout {
bld.Reset()
bld.WriteByte(line.Tag)
bld.WriteString(" ")
bld.WriteString(line.Line)
out[i] = bld.String()
}
return out
}
func (d *Differ) PlainReplace(a []string, alo int, ahi int, b []string, blo int, bhi int) (out []string, err error) {
if !(alo < ahi) || !(blo < bhi) { // assertion
return nil, errors.New("low greater than or equal to high")
}
// dump the shorter block first -- reduces the burden on short-term
// memory if the blocks are of very different sizes
if bhi-blo < ahi-alo {
out = d.Dump("+", b, blo, bhi)
out = append(out, d.Dump("-", a, alo, ahi)...)
} else {
out = d.Dump("-", a, alo, ahi)
out = append(out, d.Dump("+", b, blo, bhi)...)
}
return out, nil
}
func (d *Differ) FancyReplace(a []string, alo int, ahi int, b []string, blo int, bhi int) (out []string, err error) {
// When replacing one block of lines with another, search the blocks
// for *similar* lines; the best-matching pair (if any) is used as a
// synch point, and intraline difference marking is done on the
// similar pair. Lots of work, but often worth it.
// don't synch up unless the lines have a similarity score of at
// least cutoff; best_ratio tracks the best score seen so far
best_ratio := 0.74
cutoff := 0.75
cruncher := NewMatcherWithJunk(a, b, true, d.Charjunk)
eqi := -1 // 1st indices of equal lines (if any)
eqj := -1
out = []string{}
// search for the pair that matches best without being identical
// (identical lines must be junk lines, & we don't want to synch up
// on junk -- unless we have to)
var best_i, best_j int
for j := blo; j < bhi; j++ {
bj := b[j]
cruncher.SetSeq2(listifyString(bj))
for i := alo; i < ahi; i++ {
ai := a[i]
if ai == bj {
if eqi == -1 {
eqi = i
eqj = j
}
continue
}
cruncher.SetSeq1(listifyString(ai))
// computing similarity is expensive, so use the quick
// upper bounds first -- have seen this speed up messy
// compares by a factor of 3.
// note that ratio() is only expensive to compute the first
// time it's called on a sequence pair; the expensive part
// of the computation is cached by cruncher
if cruncher.RealQuickRatio() > best_ratio &&
cruncher.QuickRatio() > best_ratio &&
cruncher.Ratio() > best_ratio {
best_ratio = cruncher.Ratio()
best_i = i
best_j = j
}
}
}
if best_ratio < cutoff {
// no non-identical "pretty close" pair
if eqi == -1 {
// no identical pair either -- treat it as a straight replace
out, _ = d.PlainReplace(a, alo, ahi, b, blo, bhi)
return out, nil
}
// no close pair, but an identical pair -- synch up on that
best_i = eqi
best_j = eqj
best_ratio = 1.0
} else {
// there's a close pair, so forget the identical pair (if any)
eqi = -1
}
// a[best_i] very similar to b[best_j]; eqi is None iff they're not
// identical
// pump out diffs from before the synch point
out = append(out, d.fancyHelper(a, alo, best_i, b, blo, best_j)...)
// do intraline marking on the synch pair
aelt, belt := a[best_i], b[best_j]
if eqi == -1 {
// pump out a '-', '?', '+', '?' quad for the synched lines
var atags, btags string
cruncher.SetSeqs(listifyString(aelt), listifyString(belt))
opcodes := cruncher.GetOpCodes()
for _, current := range opcodes {
ai1 := current.I1
ai2 := current.I2
bj1 := current.J1
bj2 := current.J2
la, lb := ai2-ai1, bj2-bj1
if current.Tag == 'r' {
atags += strings.Repeat("^", la)
btags += strings.Repeat("^", lb)
} else if current.Tag == 'd' {
atags += strings.Repeat("-", la)
} else if current.Tag == 'i' {
btags += strings.Repeat("+", lb)
} else if current.Tag == 'e' {
atags += strings.Repeat(" ", la)
btags += strings.Repeat(" ", lb)
} else {
return nil, fmt.Errorf("unknown tag %q",
current.Tag)
}
}
out = append(out, d.QFormat(aelt, belt, atags, btags)...)
} else {
// the synch pair is identical
out = append(out, " "+aelt)
}
// pump out diffs from after the synch point
out = append(out, d.fancyHelper(a, best_i+1, ahi, b, best_j+1, bhi)...)
return out, nil
}
func (d *Differ) fancyHelper(a []string, alo int, ahi int, b []string, blo int, bhi int) (out []string) {
if alo < ahi {
if blo < bhi {
out, _ = d.FancyReplace(a, alo, ahi, b, blo, bhi)
} else {
out = d.Dump("-", a, alo, ahi)
}
} else if blo < bhi {
out = d.Dump("+", b, blo, bhi)
} else {
out = []string{}
}
return out
}
func (d *Differ) QFormat(aline string, bline string, atags string, btags string) (out []string) {
// Format "?" output and deal with leading tabs.
// Can hurt, but will probably help most of the time.
common := min(count_leading(aline, '\t'), count_leading(bline, '\t'))
common = min(common, count_leading(atags[:common], ' '))
common = min(common, count_leading(btags[:common], ' '))
atags = strings.TrimRightFunc(atags[common:], unicode.IsSpace)
btags = strings.TrimRightFunc(btags[common:], unicode.IsSpace)
out = []string{"- " + aline}
if len(atags) > 0 {
out = append(out, fmt.Sprintf("? %s%s\n",
strings.Repeat("\t", common), atags))
}
out = append(out, "+ "+bline)
if len(btags) > 0 {
out = append(out, fmt.Sprintf("? %s%s\n",
strings.Repeat("\t", common), btags))
}
return out
}
// 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)
}
// LineDiffParams contains unified diff parameters
type LineDiffParams 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
AutoJunk bool // If true, use autojunking
IsJunkLine func(string) bool // How to spot junk lines
}
// WriteUnifiedDiff compares two sequences of lines and generates 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 LineDiffParams) error {
//buf := bufio.NewWriter(writer)
//defer buf.Flush()
var bld strings.Builder
bld.Reset()
wf := func(format string, args ...any) error {
_, err := fmt.Fprintf(&bld, format, args...)
return err
}
ws := func(s string) error {
_, err := bld.WriteString(s)
return err
}
if len(diff.Eol) == 0 {
diff.Eol = "\n"
}
started := false
m := NewMatcher(diff.A, diff.B)
if diff.AutoJunk || diff.IsJunkLine != nil {
m = NewMatcherWithJunk(diff.A, diff.B, diff.AutoJunk, diff.IsJunkLine)
}
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
}
if diff.FromFile != "" || diff.ToFile != "" {
err := wf("--- %s%s%s", diff.FromFile, fromDate, diff.Eol)
if err != nil {
return err
}
err = wf("+++ %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 := wf("@@ -%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 := ws(" " + line); err != nil {
return err
}
}
continue
}
if c.Tag == 'r' || c.Tag == 'd' {
for _, line := range diff.A[i1:i2] {
if err := ws("-" + line); err != nil {
return err
}
}
}
if c.Tag == 'r' || c.Tag == 'i' {
for _, line := range diff.B[j1:j2] {
if err := ws("+" + line); err != nil {
return err
}
}
}
}
}
buf := bufio.NewWriter(writer)
buf.WriteString(bld.String())
buf.Flush()
return nil
}
// GetUnifiedDiffString is like WriteUnifiedDiff but returns the diff a string.
func GetUnifiedDiffString(diff LineDiffParams) (string, error) {
w := &bytes.Buffer{}
err := WriteUnifiedDiff(w, diff)
return w.String(), 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)
}
// ContextDiff is for backward compatibility. Ugh.
type ContextDiff = LineDiffParams
type UnifiedDiff = LineDiffParams
// WriteContextDiff compares two sequences of lines and generates 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 LineDiffParams) error {
buf := bufio.NewWriter(writer)
defer buf.Flush()
var diffErr error
wf := func(format string, args ...any) {
_, err := buf.WriteString(fmt.Sprintf(format, args...))
if diffErr == nil && err != nil {
diffErr = err
}
}
ws := func(s string) {
_, err := buf.WriteString(s)
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)
if diff.AutoJunk || diff.IsJunkLine != nil {
m = NewMatcherWithJunk(diff.A, diff.B, diff.AutoJunk, diff.IsJunkLine)
}
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
}
if diff.FromFile != "" || diff.ToFile != "" {
wf("*** %s%s%s", diff.FromFile, fromDate, diff.Eol)
wf("--- %s%s%s", diff.ToFile, toDate, diff.Eol)
}
}
first, last := g[0], g[len(g)-1]
ws("***************" + diff.Eol)
range1 := formatRangeContext(first.I1, last.I2)
wf("*** %s ****%s", range1, diff.Eol)
for _, c := range g {
if c.Tag == 'r' || c.Tag == 'd' {