104 lines
2.1 KiB
Go
104 lines
2.1 KiB
Go
// Paul's Simple Diff Algorithm v 0.1
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// (C) Paul Butler 2007 <http://www.paulbutler.org/>
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// May be used and distributed under the zlib/libpng license.
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// https://github.com/paulgb/simplediff/
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package diff
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import (
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"html"
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"io"
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"strings"
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)
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var Separator string = "\n"
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type Operation int8
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const (
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OP_INSERTED Operation = 1
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OP_UNCHANGED = 2
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OP_REMOVED = 3
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)
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type Instruction struct {
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Op Operation
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Content []string
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}
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func (this *Instruction) RenderHTML() string {
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sc := strings.Join(this.Content, Separator)
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if len(sc) == 0 {
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return ""
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}
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switch this.Op {
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case OP_INSERTED:
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return `<ins>` + sc + `</ins>`
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case OP_REMOVED:
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return `<del>` + sc + `</del>`
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default: //OP_UNCHANGED:
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return sc
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}
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}
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type twoints struct {
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O, N int
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}
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func Diff(o, n []string) []Instruction {
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if len(o) == 0 && len(n) == 0 {
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return []Instruction{}
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}
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maxl := 0
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omax := 0
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nmax := 0
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matrix := make(map[twoints]int, len(o)+1)
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for oindex, ovalue := range o {
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// Find keys in new, where value matchines ovalue
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nkeys := make([]int, 0)
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for nindex, nvalue := range n {
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if nvalue == ovalue {
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nkeys = append(nkeys, nindex)
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}
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}
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// Build diff matrix
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for _, nindex := range nkeys {
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matrix[twoints{oindex, nindex}] = matrix[twoints{oindex - 1, nindex - 1}] + 1
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if matrix[twoints{oindex, nindex}] > maxl {
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maxl = matrix[twoints{oindex, nindex}]
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omax = oindex + 1 - maxl
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nmax = nindex + 1 - maxl
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}
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}
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}
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if maxl == 0 {
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return []Instruction{
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Instruction{OP_REMOVED, o},
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Instruction{OP_INSERTED, n},
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}
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}
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ret := Diff(o[:omax], n[:nmax])
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if maxl != nmax {
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ret = append(ret, Instruction{OP_UNCHANGED, n[nmax : maxl-nmax]})
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}
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ret = append(ret, Diff(o[omax+maxl:], n[nmax+maxl:])...)
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return ret
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}
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// HtmlDiff splits o and n by newlines, and writes an HTML-safe version to the dest writer.
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func HtmlDiff(o, n string, dest io.Writer) {
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ops := Diff(strings.Split(html.EscapeString(o), Separator), strings.Split(html.EscapeString(n), Separator))
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for _, op := range ops {
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dest.Write([]byte(op.RenderHTML()))
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}
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}
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