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123 lines
4 KiB
Go
123 lines
4 KiB
Go
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// Copyright 2017, The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE.md file.
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// +build debug
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package diff
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import (
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"fmt"
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"strings"
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"sync"
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"time"
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)
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// The algorithm can be seen running in real-time by enabling debugging:
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// go test -tags=debug -v
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//
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// Example output:
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// === RUN TestDifference/#34
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// ┌───────────────────────────────┐
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// │ \ · · · · · · · · · · · · · · │
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// │ · # · · · · · · · · · · · · · │
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// │ · \ · · · · · · · · · · · · · │
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// │ · · \ · · · · · · · · · · · · │
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// │ · · · X # · · · · · · · · · · │
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// │ · · · # \ · · · · · · · · · · │
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// │ · · · · · # # · · · · · · · · │
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// │ · · · · · # \ · · · · · · · · │
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// │ · · · · · · · \ · · · · · · · │
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// │ · · · · · · · · \ · · · · · · │
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// │ · · · · · · · · · \ · · · · · │
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// │ · · · · · · · · · · \ · · # · │
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// │ · · · · · · · · · · · \ # # · │
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// │ · · · · · · · · · · · # # # · │
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// │ · · · · · · · · · · # # # # · │
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// │ · · · · · · · · · # # # # # · │
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// │ · · · · · · · · · · · · · · \ │
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// └───────────────────────────────┘
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// [.Y..M.XY......YXYXY.|]
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//
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// The grid represents the edit-graph where the horizontal axis represents
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// list X and the vertical axis represents list Y. The start of the two lists
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// is the top-left, while the ends are the bottom-right. The '·' represents
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// an unexplored node in the graph. The '\' indicates that the two symbols
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// from list X and Y are equal. The 'X' indicates that two symbols are similar
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// (but not exactly equal) to each other. The '#' indicates that the two symbols
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// are different (and not similar). The algorithm traverses this graph trying to
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// make the paths starting in the top-left and the bottom-right connect.
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//
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// The series of '.', 'X', 'Y', and 'M' characters at the bottom represents
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// the currently established path from the forward and reverse searches,
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// separated by a '|' character.
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const (
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updateDelay = 100 * time.Millisecond
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finishDelay = 500 * time.Millisecond
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ansiTerminal = true // ANSI escape codes used to move terminal cursor
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)
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var debug debugger
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type debugger struct {
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sync.Mutex
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p1, p2 EditScript
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fwdPath, revPath *EditScript
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grid []byte
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lines int
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}
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func (dbg *debugger) Begin(nx, ny int, f EqualFunc, p1, p2 *EditScript) EqualFunc {
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dbg.Lock()
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dbg.fwdPath, dbg.revPath = p1, p2
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top := "┌─" + strings.Repeat("──", nx) + "┐\n"
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row := "│ " + strings.Repeat("· ", nx) + "│\n"
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btm := "└─" + strings.Repeat("──", nx) + "┘\n"
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dbg.grid = []byte(top + strings.Repeat(row, ny) + btm)
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dbg.lines = strings.Count(dbg.String(), "\n")
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fmt.Print(dbg)
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// Wrap the EqualFunc so that we can intercept each result.
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return func(ix, iy int) (r Result) {
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cell := dbg.grid[len(top)+iy*len(row):][len("│ ")+len("· ")*ix:][:len("·")]
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for i := range cell {
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cell[i] = 0 // Zero out the multiple bytes of UTF-8 middle-dot
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}
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switch r = f(ix, iy); {
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case r.Equal():
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cell[0] = '\\'
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case r.Similar():
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cell[0] = 'X'
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default:
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cell[0] = '#'
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}
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return
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}
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}
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func (dbg *debugger) Update() {
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dbg.print(updateDelay)
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}
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func (dbg *debugger) Finish() {
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dbg.print(finishDelay)
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dbg.Unlock()
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}
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func (dbg *debugger) String() string {
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dbg.p1, dbg.p2 = *dbg.fwdPath, dbg.p2[:0]
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for i := len(*dbg.revPath) - 1; i >= 0; i-- {
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dbg.p2 = append(dbg.p2, (*dbg.revPath)[i])
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}
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return fmt.Sprintf("%s[%v|%v]\n\n", dbg.grid, dbg.p1, dbg.p2)
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}
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func (dbg *debugger) print(d time.Duration) {
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if ansiTerminal {
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fmt.Printf("\x1b[%dA", dbg.lines) // Reset terminal cursor
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}
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fmt.Print(dbg)
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time.Sleep(d)
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}
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