mirror of
https://gitea.com/Sirherobrine23/tea.git
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161 lines
4.7 KiB
Go
161 lines
4.7 KiB
Go
// Copyright (c) 2012-2016 The go-diff authors. All rights reserved.
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// https://github.com/sergi/go-diff
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// See the included LICENSE file for license details.
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//
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// go-diff is a Go implementation of Google's Diff, Match, and Patch library
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// Original library is Copyright (c) 2006 Google Inc.
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// http://code.google.com/p/google-diff-match-patch/
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package diffmatchpatch
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import (
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"math"
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)
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// MatchMain locates the best instance of 'pattern' in 'text' near 'loc'.
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// Returns -1 if no match found.
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func (dmp *DiffMatchPatch) MatchMain(text, pattern string, loc int) int {
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// Check for null inputs not needed since null can't be passed in C#.
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loc = int(math.Max(0, math.Min(float64(loc), float64(len(text)))))
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if text == pattern {
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// Shortcut (potentially not guaranteed by the algorithm)
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return 0
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} else if len(text) == 0 {
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// Nothing to match.
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return -1
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} else if loc+len(pattern) <= len(text) && text[loc:loc+len(pattern)] == pattern {
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// Perfect match at the perfect spot! (Includes case of null pattern)
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return loc
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}
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// Do a fuzzy compare.
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return dmp.MatchBitap(text, pattern, loc)
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}
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// MatchBitap locates the best instance of 'pattern' in 'text' near 'loc' using the Bitap algorithm.
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// Returns -1 if no match was found.
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func (dmp *DiffMatchPatch) MatchBitap(text, pattern string, loc int) int {
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// Initialise the alphabet.
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s := dmp.MatchAlphabet(pattern)
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// Highest score beyond which we give up.
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scoreThreshold := dmp.MatchThreshold
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// Is there a nearby exact match? (speedup)
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bestLoc := indexOf(text, pattern, loc)
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if bestLoc != -1 {
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scoreThreshold = math.Min(dmp.matchBitapScore(0, bestLoc, loc,
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pattern), scoreThreshold)
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// What about in the other direction? (speedup)
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bestLoc = lastIndexOf(text, pattern, loc+len(pattern))
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if bestLoc != -1 {
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scoreThreshold = math.Min(dmp.matchBitapScore(0, bestLoc, loc,
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pattern), scoreThreshold)
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}
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}
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// Initialise the bit arrays.
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matchmask := 1 << uint((len(pattern) - 1))
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bestLoc = -1
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var binMin, binMid int
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binMax := len(pattern) + len(text)
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lastRd := []int{}
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for d := 0; d < len(pattern); d++ {
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// 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.
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binMin = 0
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binMid = binMax
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for binMin < binMid {
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if dmp.matchBitapScore(d, loc+binMid, loc, pattern) <= scoreThreshold {
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binMin = binMid
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} else {
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binMax = binMid
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}
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binMid = (binMax-binMin)/2 + binMin
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}
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// Use the result from this iteration as the maximum for the next.
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binMax = binMid
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start := int(math.Max(1, float64(loc-binMid+1)))
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finish := int(math.Min(float64(loc+binMid), float64(len(text))) + float64(len(pattern)))
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rd := make([]int, finish+2)
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rd[finish+1] = (1 << uint(d)) - 1
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for j := finish; j >= start; j-- {
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var charMatch int
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if len(text) <= j-1 {
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// Out of range.
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charMatch = 0
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} else if _, ok := s[text[j-1]]; !ok {
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charMatch = 0
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} else {
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charMatch = s[text[j-1]]
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}
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if d == 0 {
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// First pass: exact match.
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rd[j] = ((rd[j+1] << 1) | 1) & charMatch
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} else {
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// Subsequent passes: fuzzy match.
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rd[j] = ((rd[j+1]<<1)|1)&charMatch | (((lastRd[j+1] | lastRd[j]) << 1) | 1) | lastRd[j+1]
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}
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if (rd[j] & matchmask) != 0 {
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score := dmp.matchBitapScore(d, j-1, loc, pattern)
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// This match will almost certainly be better than any existing match. But check anyway.
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if score <= scoreThreshold {
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// Told you so.
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scoreThreshold = score
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bestLoc = j - 1
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if bestLoc > loc {
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// When passing loc, don't exceed our current distance from loc.
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start = int(math.Max(1, float64(2*loc-bestLoc)))
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} else {
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// Already passed loc, downhill from here on in.
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break
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}
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}
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}
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}
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if dmp.matchBitapScore(d+1, loc, loc, pattern) > scoreThreshold {
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// No hope for a (better) match at greater error levels.
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break
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}
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lastRd = rd
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}
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return bestLoc
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}
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// matchBitapScore computes and returns the score for a match with e errors and x location.
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func (dmp *DiffMatchPatch) matchBitapScore(e, x, loc int, pattern string) float64 {
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accuracy := float64(e) / float64(len(pattern))
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proximity := math.Abs(float64(loc - x))
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if dmp.MatchDistance == 0 {
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// Dodge divide by zero error.
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if proximity == 0 {
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return accuracy
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}
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return 1.0
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}
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return accuracy + (proximity / float64(dmp.MatchDistance))
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}
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// MatchAlphabet initialises the alphabet for the Bitap algorithm.
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func (dmp *DiffMatchPatch) MatchAlphabet(pattern string) map[byte]int {
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s := map[byte]int{}
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charPattern := []byte(pattern)
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for _, c := range charPattern {
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_, ok := s[c]
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if !ok {
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s[c] = 0
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}
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}
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i := 0
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for _, c := range charPattern {
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value := s[c] | int(uint(1)<<uint((len(pattern)-i-1)))
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s[c] = value
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i++
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}
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return s
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}
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