--- /dev/null
+// 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
+}
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