niki/vendor/github.com/pmezard/go-difflib/difflib/difflib.go

// 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()

	wf := func(format string, args ...interface{}) error {

		_, err := buf.WriteString(fmt.Sprintf(format, args...))

		return err

	}

	ws := func(s string) error {

		_, err := buf.WriteString(s)

		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

			}

			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

					}

				}

			}

		}

	}

	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

	wf := func(format string, args ...interface{}) {

		_, 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)

	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' {

				for _, cc := range g {

					if cc.Tag == 'i' {

						continue

					}

					for _, line := range diff.A[cc.I1:cc.I2] {

						ws(prefix[cc.Tag] + line)

					}

				}

				break

			}

		}

		range2 := formatRangeContext(first.J1, last.J2)

		wf("--- %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] {

						ws(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

}