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/* * Copyright 2008 Google Inc. All Rights Reserved. * Copyright 2013-2014 Jan Krüger. All Rights Reserved. * Author: fraser@google.com (Neil Fraser) * Author: anteru@developer.shelter13.net (Matthaeus G. Chajdas) * Author: jan@jandoe.de (Jan Krüger) * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * Diff Match and Patch * http://code.google.com/p/google-diff-match-patch/ */ module ddmp.diff; import ddmp.util; import std.array; import std.conv; import std.datetime : SysTime, Clock, UTC; import std.exception : enforce; import std.string : indexOf, endsWith, startsWith; import std.uni; import std.regex; import std.algorithm : min, max; import std.digest.sha; import core.time; Duration diffTimeout = 1.seconds; int DIFF_EDIT_COST = 4; /** * Compute and return the source text (all equalities and deletions). * @param diffs List of Diff objects. * @return Source text. */ string diff_text1(Diff[] diffs) { auto text = appender!string(); foreach ( d; diffs ) { if (d.operation != Operation.INSERT) { text.put(d.text); } } return text.data(); } /** * Compute and return the destination text (all equalities and insertions). * @param diffs List of Diff objects. * @return Destination text. */ string diff_text2(Diff[] diffs) { auto text = appender!string(); foreach ( d; diffs ) { if (d.operation != Operation.DELETE) { text.put(d.text); } } return text.data(); } /** * Compute the Levenshtein distance; the number of inserted, deleted or * substituted characters. * @param diffs List of Diff objects. * @return Number of changes. */ int levenshtein(Diff[] diffs) { int levenshtein = 0; int insertions = 0; int deletions = 0; foreach ( d ; diffs ) { final switch (d.operation) { case Operation.INSERT: insertions += d.text.length; break; case Operation.DELETE: deletions += d.text.length; break; case Operation.EQUAL: // A deletion and an insertion is one substitution. levenshtein += max(insertions, deletions); insertions = 0; deletions = 0; break; } } levenshtein += max(insertions, deletions); return levenshtein; } /** * Crush 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. * @param diffs Array of Diff objects. * @return Delta text. */ string toDelta(in Diff[] diffs) { import std.range : walkLength; import std.format : formattedWrite; import std.uri : encode; auto text = appender!string; foreach (aDiff; diffs) { final switch (aDiff.operation) { case Operation.INSERT: text.formattedWrite("+%s\t", encode(aDiff.text).replace("%20", " ")); break; case Operation.DELETE: text.formattedWrite("-%s\t", aDiff.text.walkLength); break; case Operation.EQUAL: text.formattedWrite("=%s\t", aDiff.text.walkLength); break; } } string delta = text.data; if (delta.length != 0) { // Strip off trailing tab character. delta = delta[0 .. $-1]; delta = unescapeForEncodeUriCompatibility(delta); } return delta; } /** * Given the original text1, and an encoded string which describes the * operations required to transform text1 into text2, comAdde the full diff. * @param text1 Source string for the diff. * @param delta Delta text. * @return Array of Diff objects or null if invalid. * @throws ArgumentException If invalid input. */ Diff[] fromDelta(string text1, string delta) { import std.algorithm; import std.range; import std.string : format; import std.uri : decodeComponent; auto diffs = appender!(Diff[]); foreach (token; delta.splitter("\t")) { if (token.length == 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). string param = token[1 .. $]; switch (token[0]) { case '+': // decode would change all "+" to " " param = param.replace("+", "%2b"); param = decodeComponent(param); //} catch (UnsupportedEncodingException e) { // // Not likely on modern system. // throw new Error("This system does not support UTF-8.", e); //} catch (IllegalArgumentException e) { // // Malformed URI sequence. // throw new IllegalArgumentException( // "Illegal escape in diff_fromDelta: " + param, e); //} diffs ~= Diff(Operation.INSERT, param); break; case '-': // Fall through. case '=': int n; try { n = param.to!int; } catch (ConvException e) { throw new Exception("Invalid number in diff_fromDelta: " ~ param); } enforce (n >= 0, "Negative number in diff_fromDelta: " ~ param); string text; enforce (n <= text1.walkLength, "Delta length larger than source text length."); text = text1.takeExactly(n).array.to!string; text1.popFrontN(n); if (token[0] == '=') { diffs ~= Diff(Operation.EQUAL, text); } else { diffs ~= Diff(Operation.DELETE, text); } break; default: // Anything else is an error. throw new Exception( "Invalid diff operation in diff_fromDelta: " ~ token[0]); } } if (text1.length > 0) throw new Exception("Delta length smaller than source text length."); return diffs.data; } struct LinesToCharsResult { string text1; string text2; string[] uniqueStrings; bool opEquals()(auto ref const LinesToCharsResult other) const { return text1 == other.text1 && text2 == other.text2 && uniqueStrings == other.uniqueStrings; } } LinesToCharsResult linesToChars(string text1, string text2) { size_t[string] lineHash; LinesToCharsResult res; res.uniqueStrings = [""]; res.text1 = linesToCharsMunge(text1, res.uniqueStrings, lineHash); res.text2 = linesToCharsMunge(text2, res.uniqueStrings, lineHash); return res; } string linesToCharsMunge(string text, ref string[] lines, ref size_t[string] linehash) { sizediff_t lineStart = 0; sizediff_t lineEnd = -1; string line; auto chars = appender!string(); while( lineEnd+1 < text.length ){ lineEnd = text.indexOfAlt("\n", lineStart); if( lineEnd == -1 ) lineEnd = text.length - 1; line = text[lineStart..lineEnd + 1]; lineStart = lineEnd + 1; if (auto pv = line in linehash) { chars ~= cast(dchar)*pv; } else { lines ~= line; linehash[line] = lines.length - 1; chars ~= cast(dchar)(lines.length -1); } } return chars.data(); } void charsToLines(Diff[] diffs, string[] lineArray) { foreach (ref d; diffs) { auto str = appender!string(); foreach (dchar ch; d.text) str.put(lineArray[ch]); d.text = str.data(); } } size_t commonPrefix(string text1, string text2) { auto n = min(text1.length, text2.length); foreach (i; 0 .. n) if (text1[i] != text2[i]) return i; return n; } size_t commonSuffix(string text1, string text2) { auto n = min(text1.length, text2.length); foreach (i; 1 .. n+1) if (text1[$-i] != text2[$-i]) return i-1; return n; } /** * Determine if the suffix of one string is the prefix of another. * @param text1 First string. * @param text2 Second string. * @return The number of characters common to the end of the first * string and the start of the second string. */ size_t commonOverlap(string text1, string text2) { // Cache the text lengths to prevent multiple calls. auto text1_length = text1.length; auto text2_length = text2.length; // Eliminate the null case. if (text1_length == 0 || text2_length == 0) return 0; // Truncate the longer string. if (text1_length > text2_length) { text1 = text1[$ - text2_length .. $]; } else if (text1_length < text2_length) { text2 = text2[0 .. text1_length]; } auto text_length = min(text1_length, text2_length); // Quick check for the worst case. if (text1 == text2) { return text_length; } // 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/ int best = 0; int length = 1; while (true) { string pattern = text1[text_length - length .. $]; auto found = text2.indexOf(pattern); if (found == -1) { return best; } length += found; if (found == 0 || text1[text_length - length .. $] == text2[0 .. length]) { best = length; length++; } } } /**- * The data structure representing a diff is a List of Diff objects: * {Diff(Operation.DELETE, "Hello"), Diff(Operation.INSERT, "Goodbye"), * Diff(Operation.EQUAL, " world.")} * which means: delete "Hello", add "Goodbye" and keep " world." */ enum Operation { DELETE, INSERT, EQUAL } /** * Struct representing one diff operation. */ struct Diff { Operation operation; string text; this(Operation operation, string text) { this.operation = operation; this.text = text; } string toString() { //string prettyText = text.replace('\n', '\u00b6'); string op; final switch(operation) { case Operation.DELETE: op = "DELETE"; break; case Operation.INSERT: op = "INSERT"; break; case Operation.EQUAL: op = "EQUAL"; break; } return "Diff(" ~ op ~ ",\"" ~ text ~ "\")"; } bool opEquals(const Diff other) const { return operation == other.operation && text == other.text; } } /** * Find the differences between two texts. * Run a faster, slightly less optimal diff. * This method allows the 'checklines' of diff_main() to be optional. * Most of the time checklines is wanted, so default to true. * @param text1 Old string to be diffed. * @param text2 New string to be diffed. * @return List of Diff objects. */ Diff[] diff_main(string text1, string text2) { return diff_main(text1, text2, true); } /** * Find the differences between two texts. * @param text1 Old string to be diffed. * @param text2 New string to be diffed. * @param checklines Speedup flag. If false, then don't run a * line-level diff first to identify the changed areas. * If true, then run a faster slightly less optimal diff. * @return List of Diff objects. */ Diff[] diff_main(string text1, string text2, bool checklines) { // Set a deadline by which time the diff must be complete. SysTime deadline; if (diffTimeout <= 0.seconds) { deadline = SysTime.max; } else { deadline = Clock.currTime(UTC()) + diffTimeout; } return diff_main(text1, text2, checklines, deadline); } /** * Find the differences between two texts. Simplifies the problem by * stripping any common prefix or suffix off the texts before diffing. * @param text1 Old string to be diffed. * @param text2 New string to be diffed. * @param checklines Speedup flag. If false, then don't run a * line-level diff first to identify the changed areas. * If true, then run a faster slightly less optimal diff. * @param deadline Time when the diff should be complete by. Used * internally for recursive calls. Users should set DiffTimeout * instead. * @return List of Diff objects. */ Diff[] diff_main(string text1, string text2, bool checklines, SysTime deadline) { Diff[] diffs; if( text1 == text2 ){ if( text1.length != 0 ) diffs ~= Diff(Operation.EQUAL, text1); return diffs; } auto pos = commonPrefix(text1, text2); auto prefix = text1[0 .. pos]; text1 = text1[pos .. $]; text2 = text2[pos .. $]; pos = commonSuffix(text1, text2); auto suffix = text1[$ - pos .. $]; text1 = text1[0 .. $ - pos]; text2 = text2[0 .. $ - pos]; // Compute the diff on the middle block. diffs = computeDiffs(text1, text2, checklines, deadline); // Restore the prefix and suffix. if( prefix.length != 0 ) { diffs.insert(0, [Diff(Operation.EQUAL, prefix)]); } if( suffix.length != 0 ) { diffs ~= Diff(Operation.EQUAL, suffix); } cleanupMerge(diffs); return diffs; } struct HalfMatch { string prefix1; string suffix1; string suffix2; string prefix2; string commonMiddle; bool opEquals()(auto ref const HalfMatch other) const { return prefix1 == other.prefix1 && suffix1 == other.suffix1 && prefix2 == other.prefix2 && suffix2 == other.suffix2; } } /* * Do the two texts share a Substring which is at least half the length of * the longer text? * This speedup can produce non-minimal diffs. * @param text1 First string. * @param text2 Second string. * @return Five element String array, containing the prefix of text1, the * suffix of text1, the prefix of text2, the suffix of text2 and the * common middle. Or null if there was no match. */ bool halfMatch(string text1, string text2, out HalfMatch halfmatch){ if (diffTimeout <= 0.seconds) { // Don't risk returning a non-optimal diff if we have unlimited time. return false; } string longtext = text1.length > text2.length ? text1 : text2; string shorttext = text1.length > text2.length ? text2 : text1; if( longtext.length < 4 || shorttext.length * 2 < longtext.length ) return false; //pointless HalfMatch hm1; HalfMatch hm2; auto is_hm1 = halfMatchI(longtext, shorttext, (longtext.length + 3) / 4, hm1); auto is_hm2 = halfMatchI(longtext, shorttext, (longtext.length + 1) / 2, hm2); HalfMatch hm; if( !is_hm1 && !is_hm2 ){ return false; } else if( !is_hm2 ){ hm = hm1; } else if( !is_hm1 ){ hm = hm2; } else { hm = hm1.commonMiddle.length > hm2.commonMiddle.length ? hm1 : hm2; } if( text1.length > text2.length ) { halfmatch = hm; return true; } halfmatch.prefix1 = hm.prefix2; halfmatch.suffix1 = hm.suffix2; halfmatch.prefix2 = hm.prefix1; halfmatch.suffix2 = hm.suffix1; halfmatch.commonMiddle = hm.commonMiddle; return true; } bool halfMatchI(string longtext, string shorttext, sizediff_t i, out HalfMatch hm){ auto seed = longtext.substr(i, longtext.length / 4); sizediff_t j = -1; string best_common; string best_longtext_a; string best_longtext_b; string best_shorttext_a; string best_shorttext_b; while( j < cast(sizediff_t)shorttext.length && ( j = shorttext.indexOfAlt(seed, j + 1)) != -1 ){ auto prefixLen = commonPrefix(longtext[i .. $], shorttext[j .. $]); auto suffixLen = commonSuffix(longtext[0 .. i], shorttext[0 .. j]); if( best_common.length < suffixLen + prefixLen ) { best_common = shorttext.substr(j - suffixLen, suffixLen) ~ shorttext.substr(j, prefixLen); best_longtext_a = longtext[0 .. i - suffixLen]; best_longtext_b = longtext[i + prefixLen .. $]; best_shorttext_a = shorttext[0 .. j - suffixLen]; best_shorttext_b = shorttext[j + prefixLen .. $]; } } if( best_common.length * 2 >= longtext.length ) { hm.prefix1 = best_longtext_a; hm.suffix1 = best_longtext_b; hm.prefix2 = best_shorttext_a; hm.suffix2 = best_shorttext_b; hm.commonMiddle = best_common; return true; } else { return false; } } /** * Find the differences between two texts. Assumes that the texts do not * have any common prefix or suffix. * @param text1 Old string to be diffed. * @param text2 New string to be diffed. * @param checklines Speedup flag. If false, then don't run a * line-level diff first to identify the changed areas. * If true, then run a faster slightly less optimal diff. * @param deadline Time when the diff should be complete by. * @return List of Diff objects. */ Diff[] computeDiffs(string text1, string text2, bool checklines, SysTime deadline) { Diff[] diffs; if( text1.length == 0 ){ diffs ~= Diff(Operation.INSERT, text2); return diffs; } if( text2.length == 0 ){ diffs ~= Diff(Operation.DELETE, text1); return diffs; } auto longtext = text1.length > text2.length ? text1 : text2; auto shorttext = text1.length > text2.length ? text2 : text1; auto i = longtext.indexOf(shorttext); if( i != -1 ){ Operation op = (text1.length > text2.length) ? Operation.DELETE : Operation.INSERT; diffs ~= Diff(op, longtext[0 .. i]); diffs ~= Diff(Operation.EQUAL, shorttext); diffs ~= Diff(op, longtext[i + shorttext.length .. $]); return diffs; } if( shorttext.length == 1 ){ diffs ~= Diff(Operation.DELETE, text1); diffs ~= Diff(Operation.INSERT, text2); return diffs; } HalfMatch hm; auto is_hm = halfMatch(text1, text2, hm); if( is_hm ){ auto diffs_a = diff_main(hm.prefix1, hm.prefix2, checklines, deadline); auto diffs_b = diff_main(hm.suffix1, hm.suffix2, checklines, deadline); diffs = diffs_a; diffs ~= Diff(Operation.EQUAL, hm.commonMiddle); diffs ~= diffs_b; return diffs; } if( checklines && text1.length > 100 && text2.length > 100 ){ return diff_lineMode(text1, text2, deadline); } return bisect(text1, text2, deadline); } Diff[] diff_lineMode(string text1, string text2, SysTime deadline) { auto b = linesToChars(text1, text2); auto diffs = diff_main(b.text1, b.text2, false, deadline); charsToLines(diffs, b.uniqueStrings); cleanupSemantic(diffs); diffs ~= Diff(Operation.EQUAL, ""); auto pointer = 0; auto count_delete = 0; auto count_insert = 0; string text_delete; string text_insert; while( pointer < diffs.length ){ final switch( diffs[pointer].operation ) { case Operation.INSERT: count_insert++; text_insert ~= diffs[pointer].text; break; case Operation.DELETE: count_delete++; text_delete ~= diffs[pointer].text; break; case Operation.EQUAL: if( count_delete >= 1 && count_insert >= 1 ){ diffs.remove(pointer - count_delete - count_insert, count_delete + count_insert); pointer = pointer - count_delete - count_insert; auto a = diff_main(text_delete, text_insert, false, deadline); diffs.insert(pointer, a); pointer += a.length; } count_insert = 0; count_delete = 0; text_delete = ""; text_insert = ""; break; } pointer++; } diffs.remove(diffs.length - 1); return diffs; } Diff[] bisect(string text1, string text2, SysTime deadline) { auto text1_len = text1.length; auto text2_len = text2.length; auto max_d = (text1_len + text2_len + 1) / 2; auto v_offset = max_d; auto v_len = 2 * max_d; sizediff_t[] v1; sizediff_t[] v2; for( auto x = 0; x < v_len; x++ ){ v1 ~= -1; v2 ~= -1; } v1[v_offset + 1] = 0; v2[v_offset + 1] = 0; auto delta = text1_len - text2_len; bool front = (delta % 2 != 0); auto k1start = 0; auto k1end = 0; auto k2start = 0; auto k2end = 0; for( auto d = 0; d < max_d; d++ ){ // Bail out if deadline is reached. if (Clock.currTime(UTC()) > deadline) { break; } for( auto k1 = -d + k1start; k1 <= d - k1end; k1 += 2 ){ auto k1_offset = v_offset + k1; sizediff_t x1; if( k1 == -d || k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1] ) { x1 = v1[k1_offset + 1]; } else { x1 = v1[k1_offset - 1] + 1; } auto y1 = x1 - k1; while( x1 < text1_len && y1 < text2_len && text1[x1] == text2[y1] ){ x1++; y1++; } v1[k1_offset] = x1; if( x1 > text1_len) { k1end += 2; } else if( y1 > text2_len ){ k1start += 2; } else if( front ){ auto k2_offset = v_offset + delta - k1; if( k2_offset >= 0 && k2_offset < v_len && v2[k2_offset] != -1) { auto x2 = text1_len - v2[k2_offset]; if( x1 >= x2 ) return bisectSplit(text1, text2, x1, y1, deadline); } } } for( auto k2 = -d + k2start; k2 <= d - k2end; k2 += 2) { auto k2_offset = v_offset + k2; sizediff_t x2; if (k2 == -d || k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1]) { x2 = v2[k2_offset + 1]; } else { x2 = v2[k2_offset - 1] + 1; } auto y2 = x2 - k2; while( x2 < text1_len && y2 < text2_len && text1[text1_len - x2 - 1] == text2[text2_len - y2 - 1] ){ x2++; y2++; } v2[k2_offset] = x2; if (x2 > text1_len) { // Ran off the left of the graph. k2end += 2; } else if (y2 > text2_len) { // Ran off the top of the graph. k2start += 2; } else if (!front) { auto k1_offset = v_offset + delta - k2; if (k1_offset >= 0 && k1_offset < v_len && v1[k1_offset] != -1) { auto x1 = v1[k1_offset]; auto y1 = v_offset + x1 - k1_offset; // Mirror x2 onto top-left coordinate system. x2 = text1_len - v2[k2_offset]; if (x1 >= x2) { // Overlap detected. return bisectSplit(text1, text2, x1, y1, deadline); } } } } } Diff[] diffs; diffs ~= Diff(Operation.DELETE, text1); diffs ~= Diff(Operation.INSERT, text2); return diffs; } Diff[] bisectSplit(string text1, string text2, sizediff_t x, sizediff_t y, SysTime deadline) { auto text1a = text1[0 .. x]; auto text2a = text2[0 .. y]; auto text1b = text1[x .. $]; auto text2b = text2[y .. $]; Diff[] diffs = diff_main(text1a, text2a, false, deadline); Diff[] diffsb = diff_main(text1b, text2b, false, deadline); diffs ~= diffsb; return diffs; } void cleanupSemantic(ref Diff[] diffs) { bool changes = false; size_t[] equalities; string last_equality = null; size_t pointer = 0; size_t length_insertions1 = 0; size_t length_deletions1 = 0; size_t length_insertions2 = 0; size_t length_deletions2 = 0; while( pointer < diffs.length) { if( diffs[pointer].operation == Operation.EQUAL ){ equalities ~= pointer; length_insertions1 = length_insertions2; length_deletions1 = length_deletions2; length_insertions2 = 0; length_deletions2 = 0; last_equality = diffs[pointer].text; } else { if( diffs[pointer].operation == Operation.INSERT ){ length_insertions2 += diffs[pointer].text.length; } else { length_deletions2 += diffs[pointer].text.length; } if( last_equality !is null && (last_equality.length <= max(length_insertions1, length_deletions1)) && (last_equality.length <= max(length_insertions2, length_deletions2))) { // Duplicate record. diffs.insert(equalities[$-1], [Diff(Operation.DELETE, last_equality)]); diffs[equalities[$-1]+1] = Diff(Operation.INSERT, diffs[equalities[$-1]+1].text); // Throw away the equality we just deleted. equalities.length--; if (equalities.length > 0) { // Throw away the previous equality (it needs to be reevaluated). equalities.length--; } equalities.assumeSafeAppend(); pointer = equalities.length > 0 ? equalities[$-1] : -1; length_insertions1 = 0; length_deletions1 = 0; length_insertions2 = 0; length_deletions2 = 0; last_equality = null; changes = true; } } pointer++; } if( changes ) { cleanupMerge(diffs); } cleanupSemanticLossless(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; while( pointer < diffs.length ){ if( diffs[pointer - 1].operation == Operation.DELETE && diffs[pointer].operation == Operation.INSERT) { auto deletion = diffs[pointer - 1].text; auto insertion = diffs[pointer].text; auto overlap_len1 = commonOverlap(deletion, insertion); auto overlap_len2 = commonOverlap(insertion, deletion); if( overlap_len1 >= overlap_len2 ){ if( overlap_len1 * 2 >= deletion.length || overlap_len1 * 2 >= insertion.length) { //Overlap found. //Insert an equality and trim the surrounding edits. diffs.insert(pointer, [Diff(Operation.EQUAL, insertion[0 .. overlap_len1])]); diffs[pointer - 1].text = deletion[0 .. $ - overlap_len1]; diffs[pointer + 1].text = insertion[overlap_len1 .. $]; pointer++; } } else { if( overlap_len2 * 2 >= deletion.length || overlap_len2 * 2 >= insertion.length) { diffs.insert(pointer, [Diff(Operation.EQUAL, deletion[0 .. overlap_len2])]); diffs[pointer - 1].operation = Operation.INSERT; diffs[pointer - 1].text = insertion[0 .. $ - overlap_len2]; diffs[pointer + 1].operation = Operation.DELETE; diffs[pointer + 1].text = deletion[overlap_len2 .. $]; pointer++; } } pointer++; } pointer++; } } /** * Look for single edits surrounded on both sides by equalities * which can be shifted sideways to align the edit to a word boundary. * e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came. * @param diffs List of Diff objects. */ void cleanupSemanticLossless(ref Diff[] diffs) { auto pointer = 1; // Intentionally ignore the first and last element (don't need checking). while( pointer < cast(sizediff_t)(diffs.length) - 1 ){ if( diffs[pointer-1].operation == Operation.EQUAL && diffs[pointer+1].operation == Operation.EQUAL) { // This is a single edit surrounded by equalities. auto equality1 = diffs[pointer-1].text; auto edit = diffs[pointer].text; auto equality2 = diffs[pointer+1].text; // First, shift the edit as far left as possible auto commonOffset = commonSuffix(equality1, edit); if( commonOffset > 0 ){ auto commonString = edit[$ - commonOffset .. $]; equality1 = equality1[0 .. $ - commonOffset]; edit = commonString ~ edit[0 .. $ - commonOffset]; equality2 = commonString ~ equality2; } // Second, step character by character right, // looking for the best fit. auto best_equality1 = equality1; auto best_edit = edit; auto best_equality2 = equality2; auto best_score = cleanupSemanticScore(equality1, edit) + cleanupSemanticScore(edit, equality2); while( edit.length != 0 && equality2.length != 0 && edit[0] == equality2[0]){ equality1 ~= edit[0]; edit = edit[1 .. $] ~ equality2[0]; equality2 = equality2[1 .. $]; auto score = cleanupSemanticScore(equality1, edit) + cleanupSemanticScore(edit, equality2); // The >= encourages trailing rather than leading whitespace on // edits. if (score >= best_score) { best_score = score; best_equality1 = equality1; best_edit = edit; best_equality2 = equality2; } } if( diffs[pointer-1].text != best_equality1 ){ // We have an improvement, save it back to the diff. if( best_equality1.length != 0) { diffs[pointer-1].text = best_equality1; } else { diffs.remove(pointer - 1); pointer--; } diffs[pointer].text = best_edit; if( best_equality2.length != 0 ){ diffs[pointer+1].text = best_equality2; } else { diffs.remove(pointer + 1); pointer--; } } } pointer++; } } /** * Reorder and merge like edit sections. Merge equalities. * Any edit section can move as sizediff_t as it doesn't cross an equality. * @param diffs List of Diff objects. */ void cleanupMerge(ref Diff[] diffs) { diffs ~= Diff(Operation.EQUAL, ""); size_t pointer = 0; size_t count_delete = 0; size_t count_insert = 0; string text_delete; string text_insert; while(pointer < diffs.length) { final switch(diffs[pointer].operation){ case Operation.INSERT: count_insert++; text_insert ~= diffs[pointer].text; pointer++; break; case Operation.DELETE: count_delete++; text_delete ~= diffs[pointer].text; pointer++; break; case Operation.EQUAL: // Upon reaching an equality, check for prior redundancies. if (count_delete + count_insert > 1) { if (count_delete != 0 && count_insert != 0) { // Factor out any common prefixies. if (auto commonlength = commonPrefix(text_insert, text_delete)) { if (pointer > count_delete + count_insert && diffs[pointer - count_delete - count_insert - 1].operation == Operation.EQUAL) { diffs[pointer - count_delete - count_insert - 1].text ~= text_insert[0 .. commonlength]; } else { diffs.insert(0, [Diff(Operation.EQUAL, text_insert[0 .. commonlength])]); pointer++; } text_insert = text_insert[commonlength .. $]; text_delete = text_delete[commonlength .. $]; } // Factor out any common suffixies. if (auto commonlength = commonSuffix(text_insert, text_delete)) { diffs[pointer].text = text_insert[$ - commonlength .. $] ~ diffs[pointer].text; text_insert = text_insert[0 .. $ - commonlength]; text_delete = text_delete[0 .. $ - commonlength]; } } // Delete the offending records and add the merged ones. if (count_delete == 0) { diffs.splice(pointer - count_insert, count_delete + count_insert, [Diff(Operation.INSERT, text_insert)]); } else if (count_insert == 0) { diffs.splice(pointer - count_delete, count_delete + count_insert, [Diff(Operation.DELETE, text_delete)]); } else { diffs.splice(pointer - count_delete - count_insert, count_delete + count_insert, [Diff(Operation.DELETE, text_delete), Diff(Operation.INSERT, text_insert)]); } pointer = pointer - count_delete - count_insert + (count_delete != 0 ? 1 : 0) + (count_insert != 0 ? 1 : 0) + 1; } else if( pointer != 0 && diffs[pointer-1].operation == Operation.EQUAL ){ diffs[pointer - 1].text ~= diffs[pointer].text; diffs.remove(pointer); } else { pointer++; } count_insert = 0; count_delete = 0; text_delete = ""; text_insert = ""; break; } } if( diffs[$-1].text.length == 0){ diffs.length--; } bool changes = false; pointer = 1; while( pointer + 1 < diffs.length ) { if( diffs[pointer - 1].operation == Operation.EQUAL && diffs[pointer + 1].operation == Operation.EQUAL) { if( diffs[pointer].text.endsWith(diffs[pointer - 1].text)) { diffs[pointer].text = diffs[pointer - 1].text ~ diffs[pointer].text[0 .. $ - diffs[pointer - 1].text.length]; diffs[pointer + 1].text = diffs[pointer - 1].text ~ diffs[pointer + 1].text; diffs.splice(pointer - 1, 1); changes = true; } else if( diffs[pointer].text.startsWith(diffs[pointer + 1].text)) { diffs[pointer - 1].text ~= diffs[pointer + 1].text; diffs[pointer].text = diffs[pointer].text[diffs[pointer + 1].text.length .. $] ~ diffs[pointer + 1].text; diffs.splice(pointer + 1, 1); changes = true; } } pointer++; } if( changes ) cleanupMerge(diffs); } /** * Given two strings, comAdde a score representing whether the internal * boundary falls on logical boundaries. * Scores range from 6 (best) to 0 (worst). * @param one First string. * @param two Second string. * @return The score. */ int cleanupSemanticScore(string one, string two) { if( one.length == 0 || two.length == 0) return 6; //Edges are the best auto char1 = one[$-1]; auto char2 = two[0]; auto nonAlphaNumeric1 = !(isAlpha(char1) || isNumber(char1)); auto nonAlphaNumeric2 = !(isAlpha(char2) || isNumber(char2)); auto whitespace1 = nonAlphaNumeric1 && isWhite(char1); auto whitespace2 = nonAlphaNumeric2 && isWhite(char2); auto lineBreak1 = whitespace1 && isControl(char1); auto lineBreak2 = whitespace2 && isControl(char2); auto blankLine1 = lineBreak1 && match(one, `\n\r?\n\Z`); auto blankLine2 = lineBreak2 && match(two, `\A\r?\n\r?\n`); if (blankLine1 || blankLine2) return 5; else if (lineBreak1 || lineBreak2) return 4; else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) return 3; else if (whitespace1 || whitespace2) return 2; else if (nonAlphaNumeric1 || nonAlphaNumeric2) return 1; return 0; } /** * Reduce the number of edits by eliminating operationally trivial * equalities. * @param diffs List of Diff objects. */ void cleanupEfficiency(ref Diff[] diffs) { bool changes = false; size_t[] equalities; string lastequality; size_t pointer = 0; auto pre_ins = false; auto pre_del = false; auto post_ins = false; auto post_del = false; while( pointer < diffs.length ){ if( diffs[pointer].operation == Operation.EQUAL ){ if( diffs[pointer].text.length < DIFF_EDIT_COST && (post_ins || post_del)) { equalities ~= pointer; pre_ins = post_ins; pre_del = post_del; lastequality = diffs[pointer].text; } else { equalities.length = 0; equalities.assumeSafeAppend; lastequality = ""; } post_ins = false; post_del = false; } else { if( diffs[pointer].operation == Operation.DELETE ){ post_del = true; } else { post_ins = true; } if( lastequality.length != 0 && ( (pre_ins && pre_del && post_ins && post_del) || ((lastequality.length < DIFF_EDIT_COST / 2) && ((pre_ins ? 1 : 0) + (pre_del ? 1 : 0) + (post_ins ? 1 : 0) + (post_del ? 1 : 0)) == 3) ) ) { diffs.insert(equalities[$-1], [Diff(Operation.DELETE, lastequality)]); diffs[equalities[$-1] + 1].operation = Operation.INSERT; equalities.length--; equalities.assumeSafeAppend; lastequality = ""; if( pre_ins && pre_del ){ post_ins = true; post_del = true; equalities.length = 0; equalities.assumeSafeAppend; } else { if( equalities.length > 0 ) { equalities.length--; equalities.assumeSafeAppend; } pointer = equalities.length > 0 ? equalities[$-1] : -1; post_ins = false; post_del = false; } changes = true; } } pointer++; } if( changes ){ cleanupMerge(diffs); } } /** * loc is a location in text1, comAdde and return the equivalent location in * text2. * e.g. "The cat" vs "The big cat", 1->1, 5->8 * @param diffs List of Diff objects. * @param loc Location within text1. * @return Location within text2. */ sizediff_t xIndex(Diff[] diffs, sizediff_t loc){ auto chars1 = 0; auto chars2 = 0; auto last_chars1 = 0; auto last_chars2 = 0; Diff lastDiff; foreach ( diff; diffs) { if (diff.operation != Operation.INSERT) { // Equality or deletion. chars1 += diff.text.length; } if (diff.operation != Operation.DELETE) { // Equality or insertion. chars2 += diff.text.length; } if (chars1 > loc) { // Overshot the location. lastDiff = diff; break; } last_chars1 = chars1; last_chars2 = chars2; } if (lastDiff.operation == Operation.DELETE) { // The location was deleted. return last_chars2; } // Add the remaining character length. return last_chars2 + (loc - last_chars1); } /** * Unescape selected chars for compatability with JavaScript's encodeURI. * In speed critical applications this could be dropped since the * receiving application will certainly decode these fine. * Note that this function is case-sensitive. Thus "%3F" would not be * unescaped. But this is ok because it is only called with the output of * HttpUtility.UrlEncode which returns lowercase hex. * * Example: "%3f" -> "?", "%24" -> "$", etc. * * @param str The string to escape. * @return The escaped string. */ public static string unescapeForEncodeUriCompatibility(string str) { // FIXME: this is ridiculously inefficient return str.replace("%21", "!").replace("%7e", "~") .replace("%27", "'").replace("%28", "(").replace("%29", ")") .replace("%3b", ";").replace("%2f", "/").replace("%3f", "?") .replace("%3a", ":").replace("%40", "@").replace("%26", "&") .replace("%3d", "=").replace("%2b", "+").replace("%24", "$") .replace("%2c", ",").replace("%23", "#"); }