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gitea/vendor/github.com/sergi/go-diff/diffmatchpatch/dmp.go

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Go

/**
* dmp.go
*
* Go language implementation of Google Diff, Match, and Patch library
*
* Original library is Copyright (c) 2006 Google Inc.
* http://code.google.com/p/google-diff-match-patch/
*
* Copyright (c) 2012 Sergi Mansilla <sergi.mansilla@gmail.com>
* https://github.com/sergi/go-diff
*
* See included LICENSE file for license details.
*/
// Package diffmatchpatch offers robust algorithms to perform the
// operations required for synchronizing plain text.
package diffmatchpatch
import (
"bytes"
"errors"
"fmt"
"html"
"math"
"net/url"
"regexp"
"strconv"
"strings"
"time"
"unicode/utf8"
)
// The data structure representing a diff is an array of tuples:
// [[DiffDelete, 'Hello'], [DiffInsert, 'Goodbye'], [DiffEqual, ' world.']]
// which means: delete 'Hello', add 'Goodbye' and keep ' world.'
// Operation defines the operation of a diff item.
type Operation int8
const (
// DiffDelete item represents a delete diff.
DiffDelete Operation = -1
// DiffInsert item represents an insert diff.
DiffInsert Operation = 1
// DiffEqual item represents an equal diff.
DiffEqual Operation = 0
)
// unescaper unescapes selected chars for compatibility with JavaScript's encodeURI.
// In speed critical applications this could be dropped since the
// receiving application will certainly decode these fine.
// Note that this function is case-sensitive. Thus "%3F" would not be
// unescaped. But this is ok because it is only called with the output of
// HttpUtility.UrlEncode which returns lowercase hex.
//
// Example: "%3f" -> "?", "%24" -> "$", etc.
var unescaper = strings.NewReplacer(
"%21", "!", "%7E", "~", "%27", "'",
"%28", "(", "%29", ")", "%3B", ";",
"%2F", "/", "%3F", "?", "%3A", ":",
"%40", "@", "%26", "&", "%3D", "=",
"%2B", "+", "%24", "$", "%2C", ",", "%23", "#", "%2A", "*")
// Define some regex patterns for matching boundaries.
var (
nonAlphaNumericRegex = regexp.MustCompile(`[^a-zA-Z0-9]`)
whitespaceRegex = regexp.MustCompile(`\s`)
linebreakRegex = regexp.MustCompile(`[\r\n]`)
blanklineEndRegex = regexp.MustCompile(`\n\r?\n$`)
blanklineStartRegex = regexp.MustCompile(`^\r?\n\r?\n`)
)
func splice(slice []Diff, index int, amount int, elements ...Diff) []Diff {
return append(slice[:index], append(elements, slice[index+amount:]...)...)
}
// indexOf returns the first index of pattern in str, starting at str[i].
func indexOf(str string, pattern string, i int) int {
if i > len(str)-1 {
return -1
}
if i <= 0 {
return strings.Index(str, pattern)
}
ind := strings.Index(str[i:], pattern)
if ind == -1 {
return -1
}
return ind + i
}
// lastIndexOf returns the last index of pattern in str, starting at str[i].
func lastIndexOf(str string, pattern string, i int) int {
if i < 0 {
return -1
}
if i >= len(str) {
return strings.LastIndex(str, pattern)
}
_, size := utf8.DecodeRuneInString(str[i:])
return strings.LastIndex(str[:i+size], pattern)
}
// Return the index of pattern in target, starting at target[i].
func runesIndexOf(target, pattern []rune, i int) int {
if i > len(target)-1 {
return -1
}
if i <= 0 {
return runesIndex(target, pattern)
}
ind := runesIndex(target[i:], pattern)
if ind == -1 {
return -1
}
return ind + i
}
func min(x, y int) int {
if x < y {
return x
}
return y
}
func max(x, y int) int {
if x > y {
return x
}
return y
}
func runesEqual(r1, r2 []rune) bool {
if len(r1) != len(r2) {
return false
}
for i, c := range r1 {
if c != r2[i] {
return false
}
}
return true
}
// The equivalent of strings.Index for rune slices.
func runesIndex(r1, r2 []rune) int {
last := len(r1) - len(r2)
for i := 0; i <= last; i++ {
if runesEqual(r1[i:i+len(r2)], r2) {
return i
}
}
return -1
}
// Diff represents one diff operation
type Diff struct {
Type Operation
Text string
}
// Patch represents one patch operation.
type Patch struct {
diffs []Diff
start1 int
start2 int
length1 int
length2 int
}
// String emulates GNU diff's format.
// Header: @@ -382,8 +481,9 @@
// Indicies are printed as 1-based, not 0-based.
func (p *Patch) String() string {
var coords1, coords2 string
if p.length1 == 0 {
coords1 = strconv.Itoa(p.start1) + ",0"
} else if p.length1 == 1 {
coords1 = strconv.Itoa(p.start1 + 1)
} else {
coords1 = strconv.Itoa(p.start1+1) + "," + strconv.Itoa(p.length1)
}
if p.length2 == 0 {
coords2 = strconv.Itoa(p.start2) + ",0"
} else if p.length2 == 1 {
coords2 = strconv.Itoa(p.start2 + 1)
} else {
coords2 = strconv.Itoa(p.start2+1) + "," + strconv.Itoa(p.length2)
}
var text bytes.Buffer
_, _ = text.WriteString("@@ -" + coords1 + " +" + coords2 + " @@\n")
// Escape the body of the patch with %xx notation.
for _, aDiff := range p.diffs {
switch aDiff.Type {
case DiffInsert:
_, _ = text.WriteString("+")
case DiffDelete:
_, _ = text.WriteString("-")
case DiffEqual:
_, _ = text.WriteString(" ")
}
_, _ = text.WriteString(strings.Replace(url.QueryEscape(aDiff.Text), "+", " ", -1))
_, _ = text.WriteString("\n")
}
return unescaper.Replace(text.String())
}
// DiffMatchPatch holds the configuration for diff-match-patch operations.
type DiffMatchPatch struct {
// Number of seconds to map a diff before giving up (0 for infinity).
DiffTimeout time.Duration
// Cost of an empty edit operation in terms of edit characters.
DiffEditCost int
// How far to search for a match (0 = exact location, 1000+ = broad match).
// A match this many characters away from the expected location will add
// 1.0 to the score (0.0 is a perfect match).
MatchDistance int
// When deleting a large block of text (over ~64 characters), how close do
// the contents have to be to match the expected contents. (0.0 = perfection,
// 1.0 = very loose). Note that MatchThreshold controls how closely the
// end points of a delete need to match.
PatchDeleteThreshold float64
// Chunk size for context length.
PatchMargin int
// The number of bits in an int.
MatchMaxBits int
// At what point is no match declared (0.0 = perfection, 1.0 = very loose).
MatchThreshold float64
}
// New creates a new DiffMatchPatch object with default parameters.
func New() *DiffMatchPatch {
// Defaults.
return &DiffMatchPatch{
DiffTimeout: time.Second,
DiffEditCost: 4,
MatchThreshold: 0.5,
MatchDistance: 1000,
PatchDeleteThreshold: 0.5,
PatchMargin: 4,
MatchMaxBits: 32,
}
}
// DiffMain finds the differences between two texts.
func (dmp *DiffMatchPatch) DiffMain(text1, text2 string, checklines bool) []Diff {
return dmp.DiffMainRunes([]rune(text1), []rune(text2), checklines)
}
// DiffMainRunes finds the differences between two rune sequences.
func (dmp *DiffMatchPatch) DiffMainRunes(text1, text2 []rune, checklines bool) []Diff {
var deadline time.Time
if dmp.DiffTimeout > 0 {
deadline = time.Now().Add(dmp.DiffTimeout)
}
return dmp.diffMainRunes(text1, text2, checklines, deadline)
}
func (dmp *DiffMatchPatch) diffMainRunes(text1, text2 []rune, checklines bool, deadline time.Time) []Diff {
if runesEqual(text1, text2) {
var diffs []Diff
if len(text1) > 0 {
diffs = append(diffs, Diff{DiffEqual, string(text1)})
}
return diffs
}
// Trim off common prefix (speedup).
commonlength := commonPrefixLength(text1, text2)
commonprefix := text1[:commonlength]
text1 = text1[commonlength:]
text2 = text2[commonlength:]
// Trim off common suffix (speedup).
commonlength = commonSuffixLength(text1, text2)
commonsuffix := text1[len(text1)-commonlength:]
text1 = text1[:len(text1)-commonlength]
text2 = text2[:len(text2)-commonlength]
// Compute the diff on the middle block.
diffs := dmp.diffCompute(text1, text2, checklines, deadline)
// Restore the prefix and suffix.
if len(commonprefix) != 0 {
diffs = append([]Diff{Diff{DiffEqual, string(commonprefix)}}, diffs...)
}
if len(commonsuffix) != 0 {
diffs = append(diffs, Diff{DiffEqual, string(commonsuffix)})
}
return dmp.DiffCleanupMerge(diffs)
}
// diffCompute finds the differences between two rune slices. Assumes that the texts do not
// have any common prefix or suffix.
func (dmp *DiffMatchPatch) diffCompute(text1, text2 []rune, checklines bool, deadline time.Time) []Diff {
diffs := []Diff{}
if len(text1) == 0 {
// Just add some text (speedup).
return append(diffs, Diff{DiffInsert, string(text2)})
} else if len(text2) == 0 {
// Just delete some text (speedup).
return append(diffs, Diff{DiffDelete, string(text1)})
}
var longtext, shorttext []rune
if len(text1) > len(text2) {
longtext = text1
shorttext = text2
} else {
longtext = text2
shorttext = text1
}
if i := runesIndex(longtext, shorttext); i != -1 {
op := DiffInsert
// Swap insertions for deletions if diff is reversed.
if len(text1) > len(text2) {
op = DiffDelete
}
// Shorter text is inside the longer text (speedup).
return []Diff{
Diff{op, string(longtext[:i])},
Diff{DiffEqual, string(shorttext)},
Diff{op, string(longtext[i+len(shorttext):])},
}
} else if len(shorttext) == 1 {
// Single character string.
// After the previous speedup, the character can't be an equality.
return []Diff{
Diff{DiffDelete, string(text1)},
Diff{DiffInsert, string(text2)},
}
// Check to see if the problem can be split in two.
} else if hm := dmp.diffHalfMatch(text1, text2); hm != nil {
// A half-match was found, sort out the return data.
text1A := hm[0]
text1B := hm[1]
text2A := hm[2]
text2B := hm[3]
midCommon := hm[4]
// Send both pairs off for separate processing.
diffsA := dmp.diffMainRunes(text1A, text2A, checklines, deadline)
diffsB := dmp.diffMainRunes(text1B, text2B, checklines, deadline)
// Merge the results.
return append(diffsA, append([]Diff{Diff{DiffEqual, string(midCommon)}}, diffsB...)...)
} else if checklines && len(text1) > 100 && len(text2) > 100 {
return dmp.diffLineMode(text1, text2, deadline)
}
return dmp.diffBisect(text1, text2, deadline)
}
// diffLineMode does a quick line-level diff on both []runes, then rediff the parts for
// greater accuracy. This speedup can produce non-minimal diffs.
func (dmp *DiffMatchPatch) diffLineMode(text1, text2 []rune, deadline time.Time) []Diff {
// Scan the text on a line-by-line basis first.
text1, text2, linearray := dmp.diffLinesToRunes(text1, text2)
diffs := dmp.diffMainRunes(text1, text2, false, deadline)
// Convert the diff back to original text.
diffs = dmp.DiffCharsToLines(diffs, linearray)
// Eliminate freak matches (e.g. blank lines)
diffs = dmp.DiffCleanupSemantic(diffs)
// Rediff any replacement blocks, this time character-by-character.
// Add a dummy entry at the end.
diffs = append(diffs, Diff{DiffEqual, ""})
pointer := 0
countDelete := 0
countInsert := 0
// NOTE: Rune slices are slower than using strings in this case.
textDelete := ""
textInsert := ""
for pointer < len(diffs) {
switch diffs[pointer].Type {
case DiffInsert:
countInsert++
textInsert += diffs[pointer].Text
case DiffDelete:
countDelete++
textDelete += diffs[pointer].Text
case DiffEqual:
// Upon reaching an equality, check for prior redundancies.
if countDelete >= 1 && countInsert >= 1 {
// Delete the offending records and add the merged ones.
diffs = splice(diffs, pointer-countDelete-countInsert,
countDelete+countInsert)
pointer = pointer - countDelete - countInsert
a := dmp.diffMainRunes([]rune(textDelete), []rune(textInsert), false, deadline)
for j := len(a) - 1; j >= 0; j-- {
diffs = splice(diffs, pointer, 0, a[j])
}
pointer = pointer + len(a)
}
countInsert = 0
countDelete = 0
textDelete = ""
textInsert = ""
}
pointer++
}
return diffs[:len(diffs)-1] // Remove the dummy entry at the end.
}
// DiffBisect finds the 'middle snake' of a diff, split the problem in two
// and return the recursively constructed diff.
// See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
func (dmp *DiffMatchPatch) DiffBisect(text1, text2 string, deadline time.Time) []Diff {
// Unused in this code, but retained for interface compatibility.
return dmp.diffBisect([]rune(text1), []rune(text2), deadline)
}
// diffBisect finds the 'middle snake' of a diff, splits the problem in two
// and returns the recursively constructed diff.
// See Myers's 1986 paper: An O(ND) Difference Algorithm and Its Variations.
func (dmp *DiffMatchPatch) diffBisect(runes1, runes2 []rune, deadline time.Time) []Diff {
// Cache the text lengths to prevent multiple calls.
runes1Len, runes2Len := len(runes1), len(runes2)
maxD := (runes1Len + runes2Len + 1) / 2
vOffset := maxD
vLength := 2 * maxD
v1 := make([]int, vLength)
v2 := make([]int, vLength)
for i := range v1 {
v1[i] = -1
v2[i] = -1
}
v1[vOffset+1] = 0
v2[vOffset+1] = 0
delta := runes1Len - runes2Len
// If the total number of characters is odd, then the front path will collide
// with the reverse path.
front := (delta%2 != 0)
// Offsets for start and end of k loop.
// Prevents mapping of space beyond the grid.
k1start := 0
k1end := 0
k2start := 0
k2end := 0
for d := 0; d < maxD; d++ {
// Bail out if deadline is reached.
if !deadline.IsZero() && time.Now().After(deadline) {
break
}
// Walk the front path one step.
for k1 := -d + k1start; k1 <= d-k1end; k1 += 2 {
k1Offset := vOffset + k1
var x1 int
if k1 == -d || (k1 != d && v1[k1Offset-1] < v1[k1Offset+1]) {
x1 = v1[k1Offset+1]
} else {
x1 = v1[k1Offset-1] + 1
}
y1 := x1 - k1
for x1 < runes1Len && y1 < runes2Len {
if runes1[x1] != runes2[y1] {
break
}
x1++
y1++
}
v1[k1Offset] = x1
if x1 > runes1Len {
// Ran off the right of the graph.
k1end += 2
} else if y1 > runes2Len {
// Ran off the bottom of the graph.
k1start += 2
} else if front {
k2Offset := vOffset + delta - k1
if k2Offset >= 0 && k2Offset < vLength && v2[k2Offset] != -1 {
// Mirror x2 onto top-left coordinate system.
x2 := runes1Len - v2[k2Offset]
if x1 >= x2 {
// Overlap detected.
return dmp.diffBisectSplit(runes1, runes2, x1, y1, deadline)
}
}
}
}
// Walk the reverse path one step.
for k2 := -d + k2start; k2 <= d-k2end; k2 += 2 {
k2Offset := vOffset + k2
var x2 int
if k2 == -d || (k2 != d && v2[k2Offset-1] < v2[k2Offset+1]) {
x2 = v2[k2Offset+1]
} else {
x2 = v2[k2Offset-1] + 1
}
var y2 = x2 - k2
for x2 < runes1Len && y2 < runes2Len {
if runes1[runes1Len-x2-1] != runes2[runes2Len-y2-1] {
break
}
x2++
y2++
}
v2[k2Offset] = x2
if x2 > runes1Len {
// Ran off the left of the graph.
k2end += 2
} else if y2 > runes2Len {
// Ran off the top of the graph.
k2start += 2
} else if !front {
k1Offset := vOffset + delta - k2
if k1Offset >= 0 && k1Offset < vLength && v1[k1Offset] != -1 {
x1 := v1[k1Offset]
y1 := vOffset + x1 - k1Offset
// Mirror x2 onto top-left coordinate system.
x2 = runes1Len - x2
if x1 >= x2 {
// Overlap detected.
return dmp.diffBisectSplit(runes1, runes2, x1, y1, deadline)
}
}
}
}
}
// Diff took too long and hit the deadline or
// number of diffs equals number of characters, no commonality at all.
return []Diff{
Diff{DiffDelete, string(runes1)},
Diff{DiffInsert, string(runes2)},
}
}
func (dmp *DiffMatchPatch) diffBisectSplit(runes1, runes2 []rune, x, y int,
deadline time.Time) []Diff {
runes1a := runes1[:x]
runes2a := runes2[:y]
runes1b := runes1[x:]
runes2b := runes2[y:]
// Compute both diffs serially.
diffs := dmp.diffMainRunes(runes1a, runes2a, false, deadline)
diffsb := dmp.diffMainRunes(runes1b, runes2b, false, deadline)
return append(diffs, diffsb...)
}
// DiffLinesToChars splits two texts into a list of strings. Reduces the texts to a string of
// hashes where each Unicode character represents one line.
// It's slightly faster to call DiffLinesToRunes first, followed by DiffMainRunes.
func (dmp *DiffMatchPatch) DiffLinesToChars(text1, text2 string) (string, string, []string) {
chars1, chars2, lineArray := dmp.DiffLinesToRunes(text1, text2)
return string(chars1), string(chars2), lineArray
}
// DiffLinesToRunes splits two texts into a list of runes. Each rune represents one line.
func (dmp *DiffMatchPatch) DiffLinesToRunes(text1, text2 string) ([]rune, []rune, []string) {
// '\x00' is a valid character, but various debuggers don't like it.
// So we'll insert a junk entry to avoid generating a null character.
lineArray := []string{""} // e.g. lineArray[4] == 'Hello\n'
lineHash := map[string]int{} // e.g. lineHash['Hello\n'] == 4
chars1 := dmp.diffLinesToRunesMunge(text1, &lineArray, lineHash)
chars2 := dmp.diffLinesToRunesMunge(text2, &lineArray, lineHash)
return chars1, chars2, lineArray
}
func (dmp *DiffMatchPatch) diffLinesToRunes(text1, text2 []rune) ([]rune, []rune, []string) {
return dmp.DiffLinesToRunes(string(text1), string(text2))
}
// diffLinesToRunesMunge splits a text into an array of strings. Reduces the
// texts to a []rune where each Unicode character represents one line.
// We use strings instead of []runes as input mainly because you can't use []rune as a map key.
func (dmp *DiffMatchPatch) diffLinesToRunesMunge(text string, lineArray *[]string, lineHash map[string]int) []rune {
// Walk the text, pulling out a substring for each line.
// text.split('\n') would would temporarily double our memory footprint.
// Modifying text would create many large strings to garbage collect.
lineStart := 0
lineEnd := -1
runes := []rune{}
for lineEnd < len(text)-1 {
lineEnd = indexOf(text, "\n", lineStart)
if lineEnd == -1 {
lineEnd = len(text) - 1
}
line := text[lineStart : lineEnd+1]
lineStart = lineEnd + 1
lineValue, ok := lineHash[line]
if ok {
runes = append(runes, rune(lineValue))
} else {
*lineArray = append(*lineArray, line)
lineHash[line] = len(*lineArray) - 1
runes = append(runes, rune(len(*lineArray)-1))
}
}
return runes
}
// DiffCharsToLines rehydrates the text in a diff from a string of line hashes to real lines of
// text.
func (dmp *DiffMatchPatch) DiffCharsToLines(diffs []Diff, lineArray []string) []Diff {
hydrated := make([]Diff, 0, len(diffs))
for _, aDiff := range diffs {
chars := aDiff.Text
text := make([]string, len(chars))
for i, r := range chars {
text[i] = lineArray[r]
}
aDiff.Text = strings.Join(text, "")
hydrated = append(hydrated, aDiff)
}
return hydrated
}
// DiffCommonPrefix determines the common prefix length of two strings.
func (dmp *DiffMatchPatch) DiffCommonPrefix(text1, text2 string) int {
// Unused in this code, but retained for interface compatibility.
return commonPrefixLength([]rune(text1), []rune(text2))
}
// DiffCommonSuffix determines the common suffix length of two strings.
func (dmp *DiffMatchPatch) DiffCommonSuffix(text1, text2 string) int {
// Unused in this code, but retained for interface compatibility.
return commonSuffixLength([]rune(text1), []rune(text2))
}
// commonPrefixLength returns the length of the common prefix of two rune slices.
func commonPrefixLength(text1, text2 []rune) int {
short, long := text1, text2
if len(short) > len(long) {
short, long = long, short
}
for i, r := range short {
if r != long[i] {
return i
}
}
return len(short)
}
// commonSuffixLength returns the length of the common suffix of two rune slices.
func commonSuffixLength(text1, text2 []rune) int {
n := min(len(text1), len(text2))
for i := 0; i < n; i++ {
if text1[len(text1)-i-1] != text2[len(text2)-i-1] {
return i
}
}
return n
// Binary search.
// Performance analysis: http://neil.fraser.name/news/2007/10/09/
/*
pointermin := 0
pointermax := math.Min(len(text1), len(text2))
pointermid := pointermax
pointerend := 0
for pointermin < pointermid {
if text1[len(text1)-pointermid:len(text1)-pointerend] ==
text2[len(text2)-pointermid:len(text2)-pointerend] {
pointermin = pointermid
pointerend = pointermin
} else {
pointermax = pointermid
}
pointermid = math.Floor((pointermax-pointermin)/2 + pointermin)
}
return pointermid
*/
}
// DiffCommonOverlap determines if the suffix of one string is the prefix of another.
func (dmp *DiffMatchPatch) DiffCommonOverlap(text1 string, text2 string) int {
// Cache the text lengths to prevent multiple calls.
text1Length := len(text1)
text2Length := len(text2)
// Eliminate the null case.
if text1Length == 0 || text2Length == 0 {
return 0
}
// Truncate the longer string.
if text1Length > text2Length {
text1 = text1[text1Length-text2Length:]
} else if text1Length < text2Length {
text2 = text2[0:text1Length]
}
textLength := int(math.Min(float64(text1Length), float64(text2Length)))
// Quick check for the worst case.
if text1 == text2 {
return textLength
}
// Start by looking for a single character match
// and increase length until no match is found.
// Performance analysis: http://neil.fraser.name/news/2010/11/04/
best := 0
length := 1
for {
pattern := text1[textLength-length:]
found := strings.Index(text2, pattern)
if found == -1 {
break
}
length += found
if found == 0 || text1[textLength-length:] == text2[0:length] {
best = length
length++
}
}
return best
}
// DiffHalfMatch checks whether the two texts share a substring which is at
// least half the length of the longer text. This speedup can produce non-minimal diffs.
func (dmp *DiffMatchPatch) DiffHalfMatch(text1, text2 string) []string {
// Unused in this code, but retained for interface compatibility.
runeSlices := dmp.diffHalfMatch([]rune(text1), []rune(text2))
if runeSlices == nil {
return nil
}
result := make([]string, len(runeSlices))
for i, r := range runeSlices {
result[i] = string(r)
}
return result
}
func (dmp *DiffMatchPatch) diffHalfMatch(text1, text2 []rune) [][]rune {
if dmp.DiffTimeout <= 0 {
// Don't risk returning a non-optimal diff if we have unlimited time.
return nil
}
var longtext, shorttext []rune
if len(text1) > len(text2) {
longtext = text1
shorttext = text2
} else {
longtext = text2
shorttext = text1
}
if len(longtext) < 4 || len(shorttext)*2 < len(longtext) {
return nil // Pointless.
}
// First check if the second quarter is the seed for a half-match.
hm1 := dmp.diffHalfMatchI(longtext, shorttext, int(float64(len(longtext)+3)/4))
// Check again based on the third quarter.
hm2 := dmp.diffHalfMatchI(longtext, shorttext, int(float64(len(longtext)+1)/2))
hm := [][]rune{}
if hm1 == nil && hm2 == nil {
return nil
} else if hm2 == nil {
hm = hm1
} else if hm1 == nil {
hm = hm2
} else {
// Both matched. Select the longest.
if len(hm1[4]) > len(hm2[4]) {
hm = hm1
} else {
hm = hm2
}
}
// A half-match was found, sort out the return data.
if len(text1) > len(text2) {
return hm
}
return [][]rune{hm[2], hm[3], hm[0], hm[1], hm[4]}
}
// diffHalfMatchI checks if a substring of shorttext exist within longtext such that the substring is at least half the length of longtext?
// @param {string} longtext Longer string.
// @param {string} shorttext Shorter string.
// @param {number} i Start index of quarter length substring within longtext.
// @return {Array.<string>} Five element Array, containing the prefix of
// longtext, the suffix of longtext, the prefix of shorttext, the suffix
// of shorttext and the common middle. Or null if there was no match.
func (dmp *DiffMatchPatch) diffHalfMatchI(l, s []rune, i int) [][]rune {
var bestCommonA []rune
var bestCommonB []rune
var bestCommonLen int
var bestLongtextA []rune
var bestLongtextB []rune
var bestShorttextA []rune
var bestShorttextB []rune
// Start with a 1/4 length substring at position i as a seed.
seed := l[i : i+len(l)/4]
for j := runesIndexOf(s, seed, 0); j != -1; j = runesIndexOf(s, seed, j+1) {
prefixLength := commonPrefixLength(l[i:], s[j:])
suffixLength := commonSuffixLength(l[:i], s[:j])
if bestCommonLen < suffixLength+prefixLength {
bestCommonA = s[j-suffixLength : j]
bestCommonB = s[j : j+prefixLength]
bestCommonLen = len(bestCommonA) + len(bestCommonB)
bestLongtextA = l[:i-suffixLength]
bestLongtextB = l[i+prefixLength:]
bestShorttextA = s[:j-suffixLength]
bestShorttextB = s[j+prefixLength:]
}
}
if bestCommonLen*2 < len(l) {
return nil
}
return [][]rune{
bestLongtextA,
bestLongtextB,
bestShorttextA,
bestShorttextB,
append(bestCommonA, bestCommonB...),
}
}
// DiffCleanupSemantic reduces the number of edits by eliminating
// semantically trivial equalities.
func (dmp *DiffMatchPatch) DiffCleanupSemantic(diffs []Diff) []Diff {
changes := false
// Stack of indices where equalities are found.
type equality struct {
data int
next *equality
}
var equalities *equality
var lastequality string
// Always equal to diffs[equalities[equalitiesLength - 1]][1]
var pointer int // Index of current position.
// Number of characters that changed prior to the equality.
var lengthInsertions1, lengthDeletions1 int
// Number of characters that changed after the equality.
var lengthInsertions2, lengthDeletions2 int
for pointer < len(diffs) {
if diffs[pointer].Type == DiffEqual { // Equality found.
equalities = &equality{
data: pointer,
next: equalities,
}
lengthInsertions1 = lengthInsertions2
lengthDeletions1 = lengthDeletions2
lengthInsertions2 = 0
lengthDeletions2 = 0
lastequality = diffs[pointer].Text
} else { // An insertion or deletion.
if diffs[pointer].Type == DiffInsert {
lengthInsertions2 += len(diffs[pointer].Text)
} else {
lengthDeletions2 += len(diffs[pointer].Text)
}
// Eliminate an equality that is smaller or equal to the edits on both
// sides of it.
difference1 := int(math.Max(float64(lengthInsertions1), float64(lengthDeletions1)))
difference2 := int(math.Max(float64(lengthInsertions2), float64(lengthDeletions2)))
if len(lastequality) > 0 &&
(len(lastequality) <= difference1) &&
(len(lastequality) <= difference2) {
// Duplicate record.
insPoint := equalities.data
diffs = append(
diffs[:insPoint],
append([]Diff{Diff{DiffDelete, lastequality}}, diffs[insPoint:]...)...)
// Change second copy to insert.
diffs[insPoint+1].Type = DiffInsert
// Throw away the equality we just deleted.
equalities = equalities.next
if equalities != nil {
equalities = equalities.next
}
if equalities != nil {
pointer = equalities.data
} else {
pointer = -1
}
lengthInsertions1 = 0 // Reset the counters.
lengthDeletions1 = 0
lengthInsertions2 = 0
lengthDeletions2 = 0
lastequality = ""
changes = true
}
}
pointer++
}
// Normalize the diff.
if changes {
diffs = dmp.DiffCleanupMerge(diffs)
}
diffs = dmp.DiffCleanupSemanticLossless(diffs)
// Find any overlaps between deletions and insertions.
// e.g: <del>abcxxx</del><ins>xxxdef</ins>
// -> <del>abc</del>xxx<ins>def</ins>
// e.g: <del>xxxabc</del><ins>defxxx</ins>
// -> <ins>def</ins>xxx<del>abc</del>
// Only extract an overlap if it is as big as the edit ahead or behind it.
pointer = 1
for pointer < len(diffs) {
if diffs[pointer-1].Type == DiffDelete &&
diffs[pointer].Type == DiffInsert {
deletion := diffs[pointer-1].Text
insertion := diffs[pointer].Text
overlapLength1 := dmp.DiffCommonOverlap(deletion, insertion)
overlapLength2 := dmp.DiffCommonOverlap(insertion, deletion)
if overlapLength1 >= overlapLength2 {
if float64(overlapLength1) >= float64(len(deletion))/2 ||
float64(overlapLength1) >= float64(len(insertion))/2 {
// Overlap found. Insert an equality and trim the surrounding edits.
diffs = append(
diffs[:pointer],
append([]Diff{Diff{DiffEqual, insertion[:overlapLength1]}}, diffs[pointer:]...)...)
//diffs.splice(pointer, 0,
// [DiffEqual, insertion[0 : overlapLength1)]]
diffs[pointer-1].Text =
deletion[0 : len(deletion)-overlapLength1]
diffs[pointer+1].Text = insertion[overlapLength1:]
pointer++
}
} else {
if float64(overlapLength2) >= float64(len(deletion))/2 ||
float64(overlapLength2) >= float64(len(insertion))/2 {
// Reverse overlap found.
// Insert an equality and swap and trim the surrounding edits.
overlap := Diff{DiffEqual, deletion[:overlapLength2]}
diffs = append(
diffs[:pointer],
append([]Diff{overlap}, diffs[pointer:]...)...)
// diffs.splice(pointer, 0,
// [DiffEqual, deletion[0 : overlapLength2)]]
diffs[pointer-1].Type = DiffInsert
diffs[pointer-1].Text = insertion[0 : len(insertion)-overlapLength2]
diffs[pointer+1].Type = DiffDelete
diffs[pointer+1].Text = deletion[overlapLength2:]
pointer++
}
}
pointer++
}
pointer++
}
return diffs
}
// DiffCleanupSemanticLossless looks for single edits surrounded on both sides by equalities
// which can be shifted sideways to align the edit to a word boundary.
// e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
func (dmp *DiffMatchPatch) DiffCleanupSemanticLossless(diffs []Diff) []Diff {
/**
* Given two strings, compute a score representing whether the internal
* boundary falls on logical boundaries.
* Scores range from 6 (best) to 0 (worst).
* Closure, but does not reference any external variables.
* @param {string} one First string.
* @param {string} two Second string.
* @return {number} The score.
* @private
*/
diffCleanupSemanticScore := func(one, two string) int {
if len(one) == 0 || len(two) == 0 {
// Edges are the best.
return 6
}
// Each port of this function behaves slightly differently due to
// subtle differences in each language's definition of things like
// 'whitespace'. Since this function's purpose is largely cosmetic,
// the choice has been made to use each language's native features
// rather than force total conformity.
rune1, _ := utf8.DecodeLastRuneInString(one)
rune2, _ := utf8.DecodeRuneInString(two)
char1 := string(rune1)
char2 := string(rune2)
nonAlphaNumeric1 := nonAlphaNumericRegex.MatchString(char1)
nonAlphaNumeric2 := nonAlphaNumericRegex.MatchString(char2)
whitespace1 := nonAlphaNumeric1 && whitespaceRegex.MatchString(char1)
whitespace2 := nonAlphaNumeric2 && whitespaceRegex.MatchString(char2)
lineBreak1 := whitespace1 && linebreakRegex.MatchString(char1)
lineBreak2 := whitespace2 && linebreakRegex.MatchString(char2)
blankLine1 := lineBreak1 && blanklineEndRegex.MatchString(one)
blankLine2 := lineBreak2 && blanklineEndRegex.MatchString(two)
if blankLine1 || blankLine2 {
// Five points for blank lines.
return 5
} else if lineBreak1 || lineBreak2 {
// Four points for line breaks.
return 4
} else if nonAlphaNumeric1 && !whitespace1 && whitespace2 {
// Three points for end of sentences.
return 3
} else if whitespace1 || whitespace2 {
// Two points for whitespace.
return 2
} else if nonAlphaNumeric1 || nonAlphaNumeric2 {
// One point for non-alphanumeric.
return 1
}
return 0
}
pointer := 1
// Intentionally ignore the first and last element (don't need checking).
for pointer < len(diffs)-1 {
if diffs[pointer-1].Type == DiffEqual &&
diffs[pointer+1].Type == DiffEqual {
// This is a single edit surrounded by equalities.
equality1 := diffs[pointer-1].Text
edit := diffs[pointer].Text
equality2 := diffs[pointer+1].Text
// First, shift the edit as far left as possible.
commonOffset := dmp.DiffCommonSuffix(equality1, edit)
if commonOffset > 0 {
commonString := edit[len(edit)-commonOffset:]
equality1 = equality1[0 : len(equality1)-commonOffset]
edit = commonString + edit[:len(edit)-commonOffset]
equality2 = commonString + equality2
}
// Second, step character by character right, looking for the best fit.
bestEquality1 := equality1
bestEdit := edit
bestEquality2 := equality2
bestScore := diffCleanupSemanticScore(equality1, edit) +
diffCleanupSemanticScore(edit, equality2)
for len(edit) != 0 && len(equality2) != 0 {
_, sz := utf8.DecodeRuneInString(edit)
if len(equality2) < sz || edit[:sz] != equality2[:sz] {
break
}
equality1 += edit[:sz]
edit = edit[sz:] + equality2[:sz]
equality2 = equality2[sz:]
score := diffCleanupSemanticScore(equality1, edit) +
diffCleanupSemanticScore(edit, equality2)
// The >= encourages trailing rather than leading whitespace on
// edits.
if score >= bestScore {
bestScore = score
bestEquality1 = equality1
bestEdit = edit
bestEquality2 = equality2
}
}
if diffs[pointer-1].Text != bestEquality1 {
// We have an improvement, save it back to the diff.
if len(bestEquality1) != 0 {
diffs[pointer-1].Text = bestEquality1
} else {
diffs = splice(diffs, pointer-1, 1)
pointer--
}
diffs[pointer].Text = bestEdit
if len(bestEquality2) != 0 {
diffs[pointer+1].Text = bestEquality2
} else {
//splice(diffs, pointer+1, 1)
diffs = append(diffs[:pointer+1], diffs[pointer+2:]...)
pointer--
}
}
}
pointer++
}
return diffs
}
// DiffCleanupEfficiency reduces the number of edits by eliminating
// operationally trivial equalities.
func (dmp *DiffMatchPatch) DiffCleanupEfficiency(diffs []Diff) []Diff {
changes := false
// Stack of indices where equalities are found.
type equality struct {
data int
next *equality
}
var equalities *equality
// Always equal to equalities[equalitiesLength-1][1]
lastequality := ""
pointer := 0 // Index of current position.
// Is there an insertion operation before the last equality.
preIns := false
// Is there a deletion operation before the last equality.
preDel := false
// Is there an insertion operation after the last equality.
postIns := false
// Is there a deletion operation after the last equality.
postDel := false
for pointer < len(diffs) {
if diffs[pointer].Type == DiffEqual { // Equality found.
if len(diffs[pointer].Text) < dmp.DiffEditCost &&
(postIns || postDel) {
// Candidate found.
equalities = &equality{
data: pointer,
next: equalities,
}
preIns = postIns
preDel = postDel
lastequality = diffs[pointer].Text
} else {
// Not a candidate, and can never become one.
equalities = nil
lastequality = ""
}
postIns = false
postDel = false
} else { // An insertion or deletion.
if diffs[pointer].Type == DiffDelete {
postDel = true
} else {
postIns = true
}
/*
* Five types to be split:
* <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
* <ins>A</ins>X<ins>C</ins><del>D</del>
* <ins>A</ins><del>B</del>X<ins>C</ins>
* <ins>A</del>X<ins>C</ins><del>D</del>
* <ins>A</ins><del>B</del>X<del>C</del>
*/
var sumPres int
if preIns {
sumPres++
}
if preDel {
sumPres++
}
if postIns {
sumPres++
}
if postDel {
sumPres++
}
if len(lastequality) > 0 &&
((preIns && preDel && postIns && postDel) ||
((len(lastequality) < dmp.DiffEditCost/2) && sumPres == 3)) {
insPoint := equalities.data
// Duplicate record.
diffs = append(diffs[:insPoint],
append([]Diff{Diff{DiffDelete, lastequality}}, diffs[insPoint:]...)...)
// Change second copy to insert.
diffs[insPoint+1].Type = DiffInsert
// Throw away the equality we just deleted.
equalities = equalities.next
lastequality = ""
if preIns && preDel {
// No changes made which could affect previous entry, keep going.
postIns = true
postDel = true
equalities = nil
} else {
if equalities != nil {
equalities = equalities.next
}
if equalities != nil {
pointer = equalities.data
} else {
pointer = -1
}
postIns = false
postDel = false
}
changes = true
}
}
pointer++
}
if changes {
diffs = dmp.DiffCleanupMerge(diffs)
}
return diffs
}
// DiffCleanupMerge reorders and merges like edit sections. Merge equalities.
// Any edit section can move as long as it doesn't cross an equality.
func (dmp *DiffMatchPatch) DiffCleanupMerge(diffs []Diff) []Diff {
// Add a dummy entry at the end.
diffs = append(diffs, Diff{DiffEqual, ""})
pointer := 0
countDelete := 0
countInsert := 0
commonlength := 0
textDelete := []rune(nil)
textInsert := []rune(nil)
for pointer < len(diffs) {
switch diffs[pointer].Type {
case DiffInsert:
countInsert++
textInsert = append(textInsert, []rune(diffs[pointer].Text)...)
pointer++
break
case DiffDelete:
countDelete++
textDelete = append(textDelete, []rune(diffs[pointer].Text)...)
pointer++
break
case DiffEqual:
// Upon reaching an equality, check for prior redundancies.
if countDelete+countInsert > 1 {
if countDelete != 0 && countInsert != 0 {
// Factor out any common prefixies.
commonlength = commonPrefixLength(textInsert, textDelete)
if commonlength != 0 {
x := pointer - countDelete - countInsert
if x > 0 && diffs[x-1].Type == DiffEqual {
diffs[x-1].Text += string(textInsert[:commonlength])
} else {
diffs = append([]Diff{Diff{DiffEqual, string(textInsert[:commonlength])}}, diffs...)
pointer++
}
textInsert = textInsert[commonlength:]
textDelete = textDelete[commonlength:]
}
// Factor out any common suffixies.
commonlength = commonSuffixLength(textInsert, textDelete)
if commonlength != 0 {
insertIndex := len(textInsert) - commonlength
deleteIndex := len(textDelete) - commonlength
diffs[pointer].Text = string(textInsert[insertIndex:]) + diffs[pointer].Text
textInsert = textInsert[:insertIndex]
textDelete = textDelete[:deleteIndex]
}
}
// Delete the offending records and add the merged ones.
if countDelete == 0 {
diffs = splice(diffs, pointer-countInsert,
countDelete+countInsert,
Diff{DiffInsert, string(textInsert)})
} else if countInsert == 0 {
diffs = splice(diffs, pointer-countDelete,
countDelete+countInsert,
Diff{DiffDelete, string(textDelete)})
} else {
diffs = splice(diffs, pointer-countDelete-countInsert,
countDelete+countInsert,
Diff{DiffDelete, string(textDelete)},
Diff{DiffInsert, string(textInsert)})
}
pointer = pointer - countDelete - countInsert + 1
if countDelete != 0 {
pointer++
}
if countInsert != 0 {
pointer++
}
} else if pointer != 0 && diffs[pointer-1].Type == DiffEqual {
// Merge this equality with the previous one.
diffs[pointer-1].Text += diffs[pointer].Text
diffs = append(diffs[:pointer], diffs[pointer+1:]...)
} else {
pointer++
}
countInsert = 0
countDelete = 0
textDelete = nil
textInsert = nil
break
}
}
if len(diffs[len(diffs)-1].Text) == 0 {
diffs = diffs[0 : len(diffs)-1] // Remove the dummy entry at the end.
}
// Second pass: look for single edits surrounded on both sides by
// equalities which can be shifted sideways to eliminate an equality.
// e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
changes := false
pointer = 1
// Intentionally ignore the first and last element (don't need checking).
for pointer < (len(diffs) - 1) {
if diffs[pointer-1].Type == DiffEqual &&
diffs[pointer+1].Type == DiffEqual {
// This is a single edit surrounded by equalities.
if strings.HasSuffix(diffs[pointer].Text, diffs[pointer-1].Text) {
// Shift the edit over the previous equality.
diffs[pointer].Text = diffs[pointer-1].Text +
diffs[pointer].Text[:len(diffs[pointer].Text)-len(diffs[pointer-1].Text)]
diffs[pointer+1].Text = diffs[pointer-1].Text + diffs[pointer+1].Text
diffs = splice(diffs, pointer-1, 1)
changes = true
} else if strings.HasPrefix(diffs[pointer].Text, diffs[pointer+1].Text) {
// Shift the edit over the next equality.
diffs[pointer-1].Text += diffs[pointer+1].Text
diffs[pointer].Text =
diffs[pointer].Text[len(diffs[pointer+1].Text):] + diffs[pointer+1].Text
diffs = splice(diffs, pointer+1, 1)
changes = true
}
}
pointer++
}
// If shifts were made, the diff needs reordering and another shift sweep.
if changes {
diffs = dmp.DiffCleanupMerge(diffs)
}
return diffs
}
// DiffXIndex returns the equivalent location in s2.
// loc is a location in text1, comAdde and return the equivalent location in
// text2.
// e.g. "The cat" vs "The big cat", 1->1, 5->8
func (dmp *DiffMatchPatch) DiffXIndex(diffs []Diff, loc int) int {
chars1 := 0
chars2 := 0
lastChars1 := 0
lastChars2 := 0
lastDiff := Diff{}
for i := 0; i < len(diffs); i++ {
aDiff := diffs[i]
if aDiff.Type != DiffInsert {
// Equality or deletion.
chars1 += len(aDiff.Text)
}
if aDiff.Type != DiffDelete {
// Equality or insertion.
chars2 += len(aDiff.Text)
}
if chars1 > loc {
// Overshot the location.
lastDiff = aDiff
break
}
lastChars1 = chars1
lastChars2 = chars2
}
if lastDiff.Type == DiffDelete {
// The location was deleted.
return lastChars2
}
// Add the remaining character length.
return lastChars2 + (loc - lastChars1)
}
// DiffPrettyHtml converts a []Diff into a pretty HTML report.
// It is intended as an example from which to write one's own
// display functions.
func (dmp *DiffMatchPatch) DiffPrettyHtml(diffs []Diff) string {
var buff bytes.Buffer
for _, diff := range diffs {
text := strings.Replace(html.EscapeString(diff.Text), "\n", "&para;<br>", -1)
switch diff.Type {
case DiffInsert:
_, _ = buff.WriteString("<ins style=\"background:#e6ffe6;\">")
_, _ = buff.WriteString(text)
_, _ = buff.WriteString("</ins>")
case DiffDelete:
_, _ = buff.WriteString("<del style=\"background:#ffe6e6;\">")
_, _ = buff.WriteString(text)
_, _ = buff.WriteString("</del>")
case DiffEqual:
_, _ = buff.WriteString("<span>")
_, _ = buff.WriteString(text)
_, _ = buff.WriteString("</span>")
}
}
return buff.String()
}
// DiffPrettyText converts a []Diff into a colored text report.
func (dmp *DiffMatchPatch) DiffPrettyText(diffs []Diff) string {
var buff bytes.Buffer
for _, diff := range diffs {
text := diff.Text
switch diff.Type {
case DiffInsert:
_, _ = buff.WriteString("\x1b[32m")
_, _ = buff.WriteString(text)
_, _ = buff.WriteString("\x1b[0m")
case DiffDelete:
_, _ = buff.WriteString("\x1b[31m")
_, _ = buff.WriteString(text)
_, _ = buff.WriteString("\x1b[0m")
case DiffEqual:
_, _ = buff.WriteString(text)
}
}
return buff.String()
}
// DiffText1 computes and returns the source text (all equalities and deletions).
func (dmp *DiffMatchPatch) DiffText1(diffs []Diff) string {
//StringBuilder text = new StringBuilder()
var text bytes.Buffer
for _, aDiff := range diffs {
if aDiff.Type != DiffInsert {
_, _ = text.WriteString(aDiff.Text)
}
}
return text.String()
}
// DiffText2 computes and returns the destination text (all equalities and insertions).
func (dmp *DiffMatchPatch) DiffText2(diffs []Diff) string {
var text bytes.Buffer
for _, aDiff := range diffs {
if aDiff.Type != DiffDelete {
_, _ = text.WriteString(aDiff.Text)
}
}
return text.String()
}
// DiffLevenshtein computes the Levenshtein distance; the number of inserted, deleted or
// substituted characters.
func (dmp *DiffMatchPatch) DiffLevenshtein(diffs []Diff) int {
levenshtein := 0
insertions := 0
deletions := 0
for _, aDiff := range diffs {
switch aDiff.Type {
case DiffInsert:
insertions += len(aDiff.Text)
case DiffDelete:
deletions += len(aDiff.Text)
case DiffEqual:
// A deletion and an insertion is one substitution.
levenshtein += max(insertions, deletions)
insertions = 0
deletions = 0
}
}
levenshtein += max(insertions, deletions)
return levenshtein
}
// DiffToDelta crushes the diff into an encoded string which describes the operations
// required to transform text1 into text2.
// E.g. =3\t-2\t+ing -> Keep 3 chars, delete 2 chars, insert 'ing'.
// Operations are tab-separated. Inserted text is escaped using %xx
// notation.
func (dmp *DiffMatchPatch) DiffToDelta(diffs []Diff) string {
var text bytes.Buffer
for _, aDiff := range diffs {
switch aDiff.Type {
case DiffInsert:
_, _ = text.WriteString("+")
_, _ = text.WriteString(strings.Replace(url.QueryEscape(aDiff.Text), "+", " ", -1))
_, _ = text.WriteString("\t")
break
case DiffDelete:
_, _ = text.WriteString("-")
_, _ = text.WriteString(strconv.Itoa(utf8.RuneCountInString(aDiff.Text)))
_, _ = text.WriteString("\t")
break
case DiffEqual:
_, _ = text.WriteString("=")
_, _ = text.WriteString(strconv.Itoa(utf8.RuneCountInString(aDiff.Text)))
_, _ = text.WriteString("\t")
break
}
}
delta := text.String()
if len(delta) != 0 {
// Strip off trailing tab character.
delta = delta[0 : utf8.RuneCountInString(delta)-1]
delta = unescaper.Replace(delta)
}
return delta
}
// DiffFromDelta given the original text1, and an encoded string which describes the
// operations required to transform text1 into text2, comAdde the full diff.
func (dmp *DiffMatchPatch) DiffFromDelta(text1, delta string) (diffs []Diff, err error) {
diffs = []Diff{}
defer func() {
if r := recover(); r != nil {
err = r.(error)
}
}()
pointer := 0 // Cursor in text1
tokens := strings.Split(delta, "\t")
for _, token := range tokens {
if len(token) == 0 {
// Blank tokens are ok (from a trailing \t).
continue
}
// Each token begins with a one character parameter which specifies the
// operation of this token (delete, insert, equality).
param := token[1:]
switch op := token[0]; op {
case '+':
// decode would Diff all "+" to " "
param = strings.Replace(param, "+", "%2b", -1)
param, err = url.QueryUnescape(param)
if err != nil {
return nil, err
}
if !utf8.ValidString(param) {
return nil, fmt.Errorf("invalid UTF-8 token: %q", param)
}
diffs = append(diffs, Diff{DiffInsert, param})
case '=', '-':
n, err := strconv.ParseInt(param, 10, 0)
if err != nil {
return diffs, err
} else if n < 0 {
return diffs, errors.New("Negative number in DiffFromDelta: " + param)
}
// remember that string slicing is by byte - we want by rune here.
text := string([]rune(text1)[pointer : pointer+int(n)])
pointer += int(n)
if op == '=' {
diffs = append(diffs, Diff{DiffEqual, text})
} else {
diffs = append(diffs, Diff{DiffDelete, text})
}
default:
// Anything else is an error.
return diffs, errors.New("Invalid diff operation in DiffFromDelta: " + string(token[0]))
}
}
if pointer != len([]rune(text1)) {
return diffs, fmt.Errorf("Delta length (%v) smaller than source text length (%v)", pointer, len(text1))
}
return diffs, err
}
// MATCH FUNCTIONS
// MatchMain locates the best instance of 'pattern' in 'text' near 'loc'.
// Returns -1 if no match found.
func (dmp *DiffMatchPatch) MatchMain(text, pattern string, loc int) int {
// Check for null inputs not needed since null can't be passed in C#.
loc = int(math.Max(0, math.Min(float64(loc), float64(len(text)))))
if text == pattern {
// Shortcut (potentially not guaranteed by the algorithm)
return 0
} else if len(text) == 0 {
// Nothing to match.
return -1
} else if loc+len(pattern) <= len(text) && text[loc:loc+len(pattern)] == pattern {
// Perfect match at the perfect spot! (Includes case of null pattern)
return loc
}
// Do a fuzzy compare.
return dmp.MatchBitap(text, pattern, loc)
}
// MatchBitap locates the best instance of 'pattern' in 'text' near 'loc' using the
// Bitap algorithm. Returns -1 if no match found.
func (dmp *DiffMatchPatch) MatchBitap(text, pattern string, loc int) int {
// Initialise the alphabet.
s := dmp.MatchAlphabet(pattern)
// Highest score beyond which we give up.
scoreThreshold := dmp.MatchThreshold
// Is there a nearby exact match? (speedup)
bestLoc := indexOf(text, pattern, loc)
if bestLoc != -1 {
scoreThreshold = math.Min(dmp.matchBitapScore(0, bestLoc, loc,
pattern), scoreThreshold)
// What about in the other direction? (speedup)
bestLoc = lastIndexOf(text, pattern, loc+len(pattern))
if bestLoc != -1 {
scoreThreshold = math.Min(dmp.matchBitapScore(0, bestLoc, loc,
pattern), scoreThreshold)
}
}
// Initialise the bit arrays.
matchmask := 1 << uint((len(pattern) - 1))
bestLoc = -1
var binMin, binMid int
binMax := len(pattern) + len(text)
lastRd := []int{}
for d := 0; d < len(pattern); d++ {
// Scan for the best match; each iteration allows for one more error.
// Run a binary search to determine how far from 'loc' we can stray at
// this error level.
binMin = 0
binMid = binMax
for binMin < binMid {
if dmp.matchBitapScore(d, loc+binMid, loc, pattern) <= scoreThreshold {
binMin = binMid
} else {
binMax = binMid
}
binMid = (binMax-binMin)/2 + binMin
}
// Use the result from this iteration as the maximum for the next.
binMax = binMid
start := int(math.Max(1, float64(loc-binMid+1)))
finish := int(math.Min(float64(loc+binMid), float64(len(text))) + float64(len(pattern)))
rd := make([]int, finish+2)
rd[finish+1] = (1 << uint(d)) - 1
for j := finish; j >= start; j-- {
var charMatch int
if len(text) <= j-1 {
// Out of range.
charMatch = 0
} else if _, ok := s[text[j-1]]; !ok {
charMatch = 0
} else {
charMatch = s[text[j-1]]
}
if d == 0 {
// First pass: exact match.
rd[j] = ((rd[j+1] << 1) | 1) & charMatch
} else {
// Subsequent passes: fuzzy match.
rd[j] = ((rd[j+1]<<1)|1)&charMatch | (((lastRd[j+1] | lastRd[j]) << 1) | 1) | lastRd[j+1]
}
if (rd[j] & matchmask) != 0 {
score := dmp.matchBitapScore(d, j-1, loc, pattern)
// This match will almost certainly be better than any existing
// match. But check anyway.
if score <= scoreThreshold {
// Told you so.
scoreThreshold = score
bestLoc = j - 1
if bestLoc > loc {
// When passing loc, don't exceed our current distance from loc.
start = int(math.Max(1, float64(2*loc-bestLoc)))
} else {
// Already passed loc, downhill from here on in.
break
}
}
}
}
if dmp.matchBitapScore(d+1, loc, loc, pattern) > scoreThreshold {
// No hope for a (better) match at greater error levels.
break
}
lastRd = rd
}
return bestLoc
}
// matchBitapScore computes and returns the score for a match with e errors and x location.
func (dmp *DiffMatchPatch) matchBitapScore(e, x, loc int, pattern string) float64 {
accuracy := float64(e) / float64(len(pattern))
proximity := math.Abs(float64(loc - x))
if dmp.MatchDistance == 0 {
// Dodge divide by zero error.
if proximity == 0 {
return accuracy
}
return 1.0
}
return accuracy + (proximity / float64(dmp.MatchDistance))
}
// MatchAlphabet initialises the alphabet for the Bitap algorithm.
func (dmp *DiffMatchPatch) MatchAlphabet(pattern string) map[byte]int {
s := map[byte]int{}
charPattern := []byte(pattern)
for _, c := range charPattern {
_, ok := s[c]
if !ok {
s[c] = 0
}
}
i := 0
for _, c := range charPattern {
value := s[c] | int(uint(1)<<uint((len(pattern)-i-1)))
s[c] = value
i++
}
return s
}
// PATCH FUNCTIONS
// PatchAddContext increases the context until it is unique,
// but doesn't let the pattern expand beyond MatchMaxBits.
func (dmp *DiffMatchPatch) PatchAddContext(patch Patch, text string) Patch {
if len(text) == 0 {
return patch
}
pattern := text[patch.start2 : patch.start2+patch.length1]
padding := 0
// Look for the first and last matches of pattern in text. If two
// different matches are found, increase the pattern length.
for strings.Index(text, pattern) != strings.LastIndex(text, pattern) &&
len(pattern) < dmp.MatchMaxBits-2*dmp.PatchMargin {
padding += dmp.PatchMargin
maxStart := max(0, patch.start2-padding)
minEnd := min(len(text), patch.start2+patch.length1+padding)
pattern = text[maxStart:minEnd]
}
// Add one chunk for good luck.
padding += dmp.PatchMargin
// Add the prefix.
prefix := text[max(0, patch.start2-padding):patch.start2]
if len(prefix) != 0 {
patch.diffs = append([]Diff{Diff{DiffEqual, prefix}}, patch.diffs...)
}
// Add the suffix.
suffix := text[patch.start2+patch.length1 : min(len(text), patch.start2+patch.length1+padding)]
if len(suffix) != 0 {
patch.diffs = append(patch.diffs, Diff{DiffEqual, suffix})
}
// Roll back the start points.
patch.start1 -= len(prefix)
patch.start2 -= len(prefix)
// Extend the lengths.
patch.length1 += len(prefix) + len(suffix)
patch.length2 += len(prefix) + len(suffix)
return patch
}
// PatchMake computes a list of patches.
func (dmp *DiffMatchPatch) PatchMake(opt ...interface{}) []Patch {
if len(opt) == 1 {
diffs, _ := opt[0].([]Diff)
text1 := dmp.DiffText1(diffs)
return dmp.PatchMake(text1, diffs)
} else if len(opt) == 2 {
text1 := opt[0].(string)
switch t := opt[1].(type) {
case string:
diffs := dmp.DiffMain(text1, t, true)
if len(diffs) > 2 {
diffs = dmp.DiffCleanupSemantic(diffs)
diffs = dmp.DiffCleanupEfficiency(diffs)
}
return dmp.PatchMake(text1, diffs)
case []Diff:
return dmp.patchMake2(text1, t)
}
} else if len(opt) == 3 {
return dmp.PatchMake(opt[0], opt[2])
}
return []Patch{}
}
// patchMake2 computes a list of patches to turn text1 into text2.
// text2 is not provided, diffs are the delta between text1 and text2.
func (dmp *DiffMatchPatch) patchMake2(text1 string, diffs []Diff) []Patch {
// Check for null inputs not needed since null can't be passed in C#.
patches := []Patch{}
if len(diffs) == 0 {
return patches // Get rid of the null case.
}
patch := Patch{}
charCount1 := 0 // Number of characters into the text1 string.
charCount2 := 0 // Number of characters into the text2 string.
// Start with text1 (prepatchText) and apply the diffs until we arrive at
// text2 (postpatchText). We recreate the patches one by one to determine
// context info.
prepatchText := text1
postpatchText := text1
for i, aDiff := range diffs {
if len(patch.diffs) == 0 && aDiff.Type != DiffEqual {
// A new patch starts here.
patch.start1 = charCount1
patch.start2 = charCount2
}
switch aDiff.Type {
case DiffInsert:
patch.diffs = append(patch.diffs, aDiff)
patch.length2 += len(aDiff.Text)
postpatchText = postpatchText[:charCount2] +
aDiff.Text + postpatchText[charCount2:]
case DiffDelete:
patch.length1 += len(aDiff.Text)
patch.diffs = append(patch.diffs, aDiff)
postpatchText = postpatchText[:charCount2] + postpatchText[charCount2+len(aDiff.Text):]
case DiffEqual:
if len(aDiff.Text) <= 2*dmp.PatchMargin &&
len(patch.diffs) != 0 && i != len(diffs)-1 {
// Small equality inside a patch.
patch.diffs = append(patch.diffs, aDiff)
patch.length1 += len(aDiff.Text)
patch.length2 += len(aDiff.Text)
}
if len(aDiff.Text) >= 2*dmp.PatchMargin {
// Time for a new patch.
if len(patch.diffs) != 0 {
patch = dmp.PatchAddContext(patch, prepatchText)
patches = append(patches, patch)
patch = Patch{}
// Unlike Unidiff, our patch lists have a rolling context.
// http://code.google.com/p/google-diff-match-patch/wiki/Unidiff
// Update prepatch text & pos to reflect the application of the
// just completed patch.
prepatchText = postpatchText
charCount1 = charCount2
}
}
}
// Update the current character count.
if aDiff.Type != DiffInsert {
charCount1 += len(aDiff.Text)
}
if aDiff.Type != DiffDelete {
charCount2 += len(aDiff.Text)
}
}
// Pick up the leftover patch if not empty.
if len(patch.diffs) != 0 {
patch = dmp.PatchAddContext(patch, prepatchText)
patches = append(patches, patch)
}
return patches
}
// PatchDeepCopy returns an array that is identical to a
// given an array of patches.
func (dmp *DiffMatchPatch) PatchDeepCopy(patches []Patch) []Patch {
patchesCopy := []Patch{}
for _, aPatch := range patches {
patchCopy := Patch{}
for _, aDiff := range aPatch.diffs {
patchCopy.diffs = append(patchCopy.diffs, Diff{
aDiff.Type,
aDiff.Text,
})
}
patchCopy.start1 = aPatch.start1
patchCopy.start2 = aPatch.start2
patchCopy.length1 = aPatch.length1
patchCopy.length2 = aPatch.length2
patchesCopy = append(patchesCopy, patchCopy)
}
return patchesCopy
}
// PatchApply merges a set of patches onto the text. Returns a patched text, as well
// as an array of true/false values indicating which patches were applied.
func (dmp *DiffMatchPatch) PatchApply(patches []Patch, text string) (string, []bool) {
if len(patches) == 0 {
return text, []bool{}
}
// Deep copy the patches so that no changes are made to originals.
patches = dmp.PatchDeepCopy(patches)
nullPadding := dmp.PatchAddPadding(patches)
text = nullPadding + text + nullPadding
patches = dmp.PatchSplitMax(patches)
x := 0
// delta keeps track of the offset between the expected and actual
// location of the previous patch. If there are patches expected at
// positions 10 and 20, but the first patch was found at 12, delta is 2
// and the second patch has an effective expected position of 22.
delta := 0
results := make([]bool, len(patches))
for _, aPatch := range patches {
expectedLoc := aPatch.start2 + delta
text1 := dmp.DiffText1(aPatch.diffs)
var startLoc int
endLoc := -1
if len(text1) > dmp.MatchMaxBits {
// PatchSplitMax will only provide an oversized pattern
// in the case of a monster delete.
startLoc = dmp.MatchMain(text, text1[:dmp.MatchMaxBits], expectedLoc)
if startLoc != -1 {
endLoc = dmp.MatchMain(text,
text1[len(text1)-dmp.MatchMaxBits:], expectedLoc+len(text1)-dmp.MatchMaxBits)
if endLoc == -1 || startLoc >= endLoc {
// Can't find valid trailing context. Drop this patch.
startLoc = -1
}
}
} else {
startLoc = dmp.MatchMain(text, text1, expectedLoc)
}
if startLoc == -1 {
// No match found. :(
results[x] = false
// Subtract the delta for this failed patch from subsequent patches.
delta -= aPatch.length2 - aPatch.length1
} else {
// Found a match. :)
results[x] = true
delta = startLoc - expectedLoc
var text2 string
if endLoc == -1 {
text2 = text[startLoc:int(math.Min(float64(startLoc+len(text1)), float64(len(text))))]
} else {
text2 = text[startLoc:int(math.Min(float64(endLoc+dmp.MatchMaxBits), float64(len(text))))]
}
if text1 == text2 {
// Perfect match, just shove the Replacement text in.
text = text[:startLoc] + dmp.DiffText2(aPatch.diffs) + text[startLoc+len(text1):]
} else {
// Imperfect match. Run a diff to get a framework of equivalent
// indices.
diffs := dmp.DiffMain(text1, text2, false)
if len(text1) > dmp.MatchMaxBits && float64(dmp.DiffLevenshtein(diffs))/float64(len(text1)) > dmp.PatchDeleteThreshold {
// The end points match, but the content is unacceptably bad.
results[x] = false
} else {
diffs = dmp.DiffCleanupSemanticLossless(diffs)
index1 := 0
for _, aDiff := range aPatch.diffs {
if aDiff.Type != DiffEqual {
index2 := dmp.DiffXIndex(diffs, index1)
if aDiff.Type == DiffInsert {
// Insertion
text = text[:startLoc+index2] + aDiff.Text + text[startLoc+index2:]
} else if aDiff.Type == DiffDelete {
// Deletion
startIndex := startLoc + index2
text = text[:startIndex] +
text[startIndex+dmp.DiffXIndex(diffs, index1+len(aDiff.Text))-index2:]
}
}
if aDiff.Type != DiffDelete {
index1 += len(aDiff.Text)
}
}
}
}
}
x++
}
// Strip the padding off.
text = text[len(nullPadding) : len(nullPadding)+(len(text)-2*len(nullPadding))]
return text, results
}
// PatchAddPadding adds some padding on text start and end so that edges can match something.
// Intended to be called only from within patchApply.
func (dmp *DiffMatchPatch) PatchAddPadding(patches []Patch) string {
paddingLength := dmp.PatchMargin
nullPadding := ""
for x := 1; x <= paddingLength; x++ {
nullPadding += string(x)
}
// Bump all the patches forward.
for i := range patches {
patches[i].start1 += paddingLength
patches[i].start2 += paddingLength
}
// Add some padding on start of first diff.
if len(patches[0].diffs) == 0 || patches[0].diffs[0].Type != DiffEqual {
// Add nullPadding equality.
patches[0].diffs = append([]Diff{Diff{DiffEqual, nullPadding}}, patches[0].diffs...)
patches[0].start1 -= paddingLength // Should be 0.
patches[0].start2 -= paddingLength // Should be 0.
patches[0].length1 += paddingLength
patches[0].length2 += paddingLength
} else if paddingLength > len(patches[0].diffs[0].Text) {
// Grow first equality.
extraLength := paddingLength - len(patches[0].diffs[0].Text)
patches[0].diffs[0].Text = nullPadding[len(patches[0].diffs[0].Text):] + patches[0].diffs[0].Text
patches[0].start1 -= extraLength
patches[0].start2 -= extraLength
patches[0].length1 += extraLength
patches[0].length2 += extraLength
}
// Add some padding on end of last diff.
last := len(patches) - 1
if len(patches[last].diffs) == 0 || patches[last].diffs[len(patches[last].diffs)-1].Type != DiffEqual {
// Add nullPadding equality.
patches[last].diffs = append(patches[last].diffs, Diff{DiffEqual, nullPadding})
patches[last].length1 += paddingLength
patches[last].length2 += paddingLength
} else if paddingLength > len(patches[last].diffs[len(patches[last].diffs)-1].Text) {
// Grow last equality.
lastDiff := patches[last].diffs[len(patches[last].diffs)-1]
extraLength := paddingLength - len(lastDiff.Text)
patches[last].diffs[len(patches[last].diffs)-1].Text += nullPadding[:extraLength]
patches[last].length1 += extraLength
patches[last].length2 += extraLength
}
return nullPadding
}
// PatchSplitMax looks through the patches and breaks up any which are longer than the
// maximum limit of the match algorithm.
// Intended to be called only from within patchApply.
func (dmp *DiffMatchPatch) PatchSplitMax(patches []Patch) []Patch {
patchSize := dmp.MatchMaxBits
for x := 0; x < len(patches); x++ {
if patches[x].length1 <= patchSize {
continue
}
bigpatch := patches[x]
// Remove the big old patch.
patches = append(patches[:x], patches[x+1:]...)
x--
start1 := bigpatch.start1
start2 := bigpatch.start2
precontext := ""
for len(bigpatch.diffs) != 0 {
// Create one of several smaller patches.
patch := Patch{}
empty := true
patch.start1 = start1 - len(precontext)
patch.start2 = start2 - len(precontext)
if len(precontext) != 0 {
patch.length1 = len(precontext)
patch.length2 = len(precontext)
patch.diffs = append(patch.diffs, Diff{DiffEqual, precontext})
}
for len(bigpatch.diffs) != 0 && patch.length1 < patchSize-dmp.PatchMargin {
diffType := bigpatch.diffs[0].Type
diffText := bigpatch.diffs[0].Text
if diffType == DiffInsert {
// Insertions are harmless.
patch.length2 += len(diffText)
start2 += len(diffText)
patch.diffs = append(patch.diffs, bigpatch.diffs[0])
bigpatch.diffs = bigpatch.diffs[1:]
empty = false
} else if diffType == DiffDelete && len(patch.diffs) == 1 && patch.diffs[0].Type == DiffEqual && len(diffText) > 2*patchSize {
// This is a large deletion. Let it pass in one chunk.
patch.length1 += len(diffText)
start1 += len(diffText)
empty = false
patch.diffs = append(patch.diffs, Diff{diffType, diffText})
bigpatch.diffs = bigpatch.diffs[1:]
} else {
// Deletion or equality. Only take as much as we can stomach.
diffText = diffText[:min(len(diffText), patchSize-patch.length1-dmp.PatchMargin)]
patch.length1 += len(diffText)
start1 += len(diffText)
if diffType == DiffEqual {
patch.length2 += len(diffText)
start2 += len(diffText)
} else {
empty = false
}
patch.diffs = append(patch.diffs, Diff{diffType, diffText})
if diffText == bigpatch.diffs[0].Text {
bigpatch.diffs = bigpatch.diffs[1:]
} else {
bigpatch.diffs[0].Text =
bigpatch.diffs[0].Text[len(diffText):]
}
}
}
// Compute the head context for the next patch.
precontext = dmp.DiffText2(patch.diffs)
precontext = precontext[max(0, len(precontext)-dmp.PatchMargin):]
postcontext := ""
// Append the end context for this patch.
if len(dmp.DiffText1(bigpatch.diffs)) > dmp.PatchMargin {
postcontext = dmp.DiffText1(bigpatch.diffs)[:dmp.PatchMargin]
} else {
postcontext = dmp.DiffText1(bigpatch.diffs)
}
if len(postcontext) != 0 {
patch.length1 += len(postcontext)
patch.length2 += len(postcontext)
if len(patch.diffs) != 0 && patch.diffs[len(patch.diffs)-1].Type == DiffEqual {
patch.diffs[len(patch.diffs)-1].Text += postcontext
} else {
patch.diffs = append(patch.diffs, Diff{DiffEqual, postcontext})
}
}
if !empty {
x++
patches = append(patches[:x], append([]Patch{patch}, patches[x:]...)...)
}
}
}
return patches
}
// PatchToText takes a list of patches and returns a textual representation.
func (dmp *DiffMatchPatch) PatchToText(patches []Patch) string {
var text bytes.Buffer
for _, aPatch := range patches {
_, _ = text.WriteString(aPatch.String())
}
return text.String()
}
// PatchFromText parses a textual representation of patches and returns a List of Patch
// objects.
func (dmp *DiffMatchPatch) PatchFromText(textline string) ([]Patch, error) {
patches := []Patch{}
if len(textline) == 0 {
return patches, nil
}
text := strings.Split(textline, "\n")
textPointer := 0
patchHeader := regexp.MustCompile("^@@ -(\\d+),?(\\d*) \\+(\\d+),?(\\d*) @@$")
var patch Patch
var sign uint8
var line string
for textPointer < len(text) {
if !patchHeader.MatchString(text[textPointer]) {
return patches, errors.New("Invalid patch string: " + text[textPointer])
}
patch = Patch{}
m := patchHeader.FindStringSubmatch(text[textPointer])
patch.start1, _ = strconv.Atoi(m[1])
if len(m[2]) == 0 {
patch.start1--
patch.length1 = 1
} else if m[2] == "0" {
patch.length1 = 0
} else {
patch.start1--
patch.length1, _ = strconv.Atoi(m[2])
}
patch.start2, _ = strconv.Atoi(m[3])
if len(m[4]) == 0 {
patch.start2--
patch.length2 = 1
} else if m[4] == "0" {
patch.length2 = 0
} else {
patch.start2--
patch.length2, _ = strconv.Atoi(m[4])
}
textPointer++
for textPointer < len(text) {
if len(text[textPointer]) > 0 {
sign = text[textPointer][0]
} else {
textPointer++
continue
}
line = text[textPointer][1:]
line = strings.Replace(line, "+", "%2b", -1)
line, _ = url.QueryUnescape(line)
if sign == '-' {
// Deletion.
patch.diffs = append(patch.diffs, Diff{DiffDelete, line})
} else if sign == '+' {
// Insertion.
patch.diffs = append(patch.diffs, Diff{DiffInsert, line})
} else if sign == ' ' {
// Minor equality.
patch.diffs = append(patch.diffs, Diff{DiffEqual, line})
} else if sign == '@' {
// Start of next patch.
break
} else {
// WTF?
return patches, errors.New("Invalid patch mode '" + string(sign) + "' in: " + string(line))
}
textPointer++
}
patches = append(patches, patch)
}
return patches, nil
}