699 lines
24 KiB
JavaScript
699 lines
24 KiB
JavaScript
/**
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* This library modifies the diff-patch-match library by Neil Fraser
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* by removing the patch and match functionality and certain advanced
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* options in the diff function. The original license is as follows:
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*
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* ===
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*
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* Diff Match and Patch
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*
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* Copyright 2006 Google Inc.
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* http://code.google.com/p/google-diff-match-patch/
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* The data structure representing a diff is an array of tuples:
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* [[DIFF_DELETE, 'Hello'], [DIFF_INSERT, 'Goodbye'], [DIFF_EQUAL, ' world.']]
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* which means: delete 'Hello', add 'Goodbye' and keep ' world.'
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*/
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var DIFF_DELETE = -1;
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var DIFF_INSERT = 1;
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var DIFF_EQUAL = 0;
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/**
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* Find the differences between two texts. Simplifies the problem by stripping
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* any common prefix or suffix off the texts before diffing.
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* @param {string} text1 Old string to be diffed.
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* @param {string} text2 New string to be diffed.
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* @param {Int} cursor_pos Expected edit position in text1 (optional)
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* @return {Array} Array of diff tuples.
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*/
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function diff_main(text1, text2, cursor_pos) {
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// Check for equality (speedup).
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if (text1 == text2) {
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if (text1) {
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return [[DIFF_EQUAL, text1]];
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}
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return [];
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}
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// Check cursor_pos within bounds
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if (cursor_pos < 0 || text1.length < cursor_pos) {
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cursor_pos = null;
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}
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// Trim off common prefix (speedup).
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var commonlength = diff_commonPrefix(text1, text2);
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var commonprefix = text1.substring(0, commonlength);
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text1 = text1.substring(commonlength);
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text2 = text2.substring(commonlength);
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// Trim off common suffix (speedup).
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commonlength = diff_commonSuffix(text1, text2);
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var commonsuffix = text1.substring(text1.length - commonlength);
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text1 = text1.substring(0, text1.length - commonlength);
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text2 = text2.substring(0, text2.length - commonlength);
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// Compute the diff on the middle block.
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var diffs = diff_compute_(text1, text2);
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// Restore the prefix and suffix.
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if (commonprefix) {
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diffs.unshift([DIFF_EQUAL, commonprefix]);
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}
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if (commonsuffix) {
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diffs.push([DIFF_EQUAL, commonsuffix]);
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}
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diff_cleanupMerge(diffs);
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if (cursor_pos != null) {
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diffs = fix_cursor(diffs, cursor_pos);
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}
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return diffs;
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};
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/**
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* Find the differences between two texts. Assumes that the texts do not
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* have any common prefix or suffix.
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* @param {string} text1 Old string to be diffed.
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* @param {string} text2 New string to be diffed.
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* @return {Array} Array of diff tuples.
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*/
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function diff_compute_(text1, text2) {
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var diffs;
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if (!text1) {
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// Just add some text (speedup).
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return [[DIFF_INSERT, text2]];
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}
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if (!text2) {
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// Just delete some text (speedup).
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return [[DIFF_DELETE, text1]];
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}
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var longtext = text1.length > text2.length ? text1 : text2;
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var shorttext = text1.length > text2.length ? text2 : text1;
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var i = longtext.indexOf(shorttext);
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if (i != -1) {
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// Shorter text is inside the longer text (speedup).
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diffs = [[DIFF_INSERT, longtext.substring(0, i)],
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[DIFF_EQUAL, shorttext],
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[DIFF_INSERT, longtext.substring(i + shorttext.length)]];
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// Swap insertions for deletions if diff is reversed.
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if (text1.length > text2.length) {
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diffs[0][0] = diffs[2][0] = DIFF_DELETE;
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}
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return diffs;
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}
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if (shorttext.length == 1) {
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// Single character string.
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// After the previous speedup, the character can't be an equality.
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return [[DIFF_DELETE, text1], [DIFF_INSERT, text2]];
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}
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// Check to see if the problem can be split in two.
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var hm = diff_halfMatch_(text1, text2);
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if (hm) {
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// A half-match was found, sort out the return data.
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var text1_a = hm[0];
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var text1_b = hm[1];
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var text2_a = hm[2];
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var text2_b = hm[3];
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var mid_common = hm[4];
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// Send both pairs off for separate processing.
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var diffs_a = diff_main(text1_a, text2_a);
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var diffs_b = diff_main(text1_b, text2_b);
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// Merge the results.
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return diffs_a.concat([[DIFF_EQUAL, mid_common]], diffs_b);
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}
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return diff_bisect_(text1, text2);
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};
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/**
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* Find the 'middle snake' of a diff, split the problem in two
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* and return the recursively constructed diff.
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* See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
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* @param {string} text1 Old string to be diffed.
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* @param {string} text2 New string to be diffed.
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* @return {Array} Array of diff tuples.
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* @private
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*/
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function diff_bisect_(text1, text2) {
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// Cache the text lengths to prevent multiple calls.
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var text1_length = text1.length;
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var text2_length = text2.length;
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var max_d = Math.ceil((text1_length + text2_length) / 2);
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var v_offset = max_d;
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var v_length = 2 * max_d;
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var v1 = new Array(v_length);
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var v2 = new Array(v_length);
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// Setting all elements to -1 is faster in Chrome & Firefox than mixing
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// integers and undefined.
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for (var x = 0; x < v_length; x++) {
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v1[x] = -1;
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v2[x] = -1;
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}
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v1[v_offset + 1] = 0;
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v2[v_offset + 1] = 0;
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var delta = text1_length - text2_length;
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// If the total number of characters is odd, then the front path will collide
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// with the reverse path.
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var front = (delta % 2 != 0);
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// Offsets for start and end of k loop.
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// Prevents mapping of space beyond the grid.
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var k1start = 0;
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var k1end = 0;
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var k2start = 0;
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var k2end = 0;
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for (var d = 0; d < max_d; d++) {
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// Walk the front path one step.
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for (var k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
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var k1_offset = v_offset + k1;
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var x1;
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if (k1 == -d || (k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1])) {
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x1 = v1[k1_offset + 1];
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} else {
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x1 = v1[k1_offset - 1] + 1;
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}
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var y1 = x1 - k1;
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while (x1 < text1_length && y1 < text2_length &&
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text1.charAt(x1) == text2.charAt(y1)) {
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x1++;
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y1++;
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}
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v1[k1_offset] = x1;
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if (x1 > text1_length) {
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// Ran off the right of the graph.
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k1end += 2;
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} else if (y1 > text2_length) {
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// Ran off the bottom of the graph.
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k1start += 2;
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} else if (front) {
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var k2_offset = v_offset + delta - k1;
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if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {
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// Mirror x2 onto top-left coordinate system.
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var x2 = text1_length - v2[k2_offset];
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if (x1 >= x2) {
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// Overlap detected.
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return diff_bisectSplit_(text1, text2, x1, y1);
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}
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}
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}
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}
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// Walk the reverse path one step.
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for (var k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
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var k2_offset = v_offset + k2;
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var x2;
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if (k2 == -d || (k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1])) {
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x2 = v2[k2_offset + 1];
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} else {
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x2 = v2[k2_offset - 1] + 1;
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}
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var y2 = x2 - k2;
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while (x2 < text1_length && y2 < text2_length &&
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text1.charAt(text1_length - x2 - 1) ==
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text2.charAt(text2_length - y2 - 1)) {
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x2++;
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y2++;
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}
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v2[k2_offset] = x2;
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if (x2 > text1_length) {
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// Ran off the left of the graph.
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k2end += 2;
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} else if (y2 > text2_length) {
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// Ran off the top of the graph.
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k2start += 2;
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} else if (!front) {
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var k1_offset = v_offset + delta - k2;
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if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {
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var x1 = v1[k1_offset];
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var y1 = v_offset + x1 - k1_offset;
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// Mirror x2 onto top-left coordinate system.
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x2 = text1_length - x2;
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if (x1 >= x2) {
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// Overlap detected.
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return diff_bisectSplit_(text1, text2, x1, y1);
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}
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}
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}
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}
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}
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// Diff took too long and hit the deadline or
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// number of diffs equals number of characters, no commonality at all.
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return [[DIFF_DELETE, text1], [DIFF_INSERT, text2]];
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};
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/**
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* Given the location of the 'middle snake', split the diff in two parts
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* and recurse.
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* @param {string} text1 Old string to be diffed.
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* @param {string} text2 New string to be diffed.
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* @param {number} x Index of split point in text1.
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* @param {number} y Index of split point in text2.
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* @return {Array} Array of diff tuples.
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*/
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function diff_bisectSplit_(text1, text2, x, y) {
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var text1a = text1.substring(0, x);
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var text2a = text2.substring(0, y);
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var text1b = text1.substring(x);
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var text2b = text2.substring(y);
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// Compute both diffs serially.
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var diffs = diff_main(text1a, text2a);
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var diffsb = diff_main(text1b, text2b);
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return diffs.concat(diffsb);
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};
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/**
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* Determine the common prefix of two strings.
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* @param {string} text1 First string.
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* @param {string} text2 Second string.
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* @return {number} The number of characters common to the start of each
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* string.
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*/
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function diff_commonPrefix(text1, text2) {
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// Quick check for common null cases.
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if (!text1 || !text2 || text1.charAt(0) != text2.charAt(0)) {
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return 0;
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}
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// Binary search.
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// Performance analysis: http://neil.fraser.name/news/2007/10/09/
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var pointermin = 0;
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var pointermax = Math.min(text1.length, text2.length);
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var pointermid = pointermax;
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var pointerstart = 0;
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while (pointermin < pointermid) {
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if (text1.substring(pointerstart, pointermid) ==
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text2.substring(pointerstart, pointermid)) {
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pointermin = pointermid;
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pointerstart = pointermin;
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} else {
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pointermax = pointermid;
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}
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pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
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}
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return pointermid;
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};
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/**
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* Determine the common suffix of two strings.
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* @param {string} text1 First string.
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* @param {string} text2 Second string.
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* @return {number} The number of characters common to the end of each string.
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*/
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function diff_commonSuffix(text1, text2) {
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// Quick check for common null cases.
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if (!text1 || !text2 ||
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text1.charAt(text1.length - 1) != text2.charAt(text2.length - 1)) {
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return 0;
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}
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// Binary search.
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// Performance analysis: http://neil.fraser.name/news/2007/10/09/
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var pointermin = 0;
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var pointermax = Math.min(text1.length, text2.length);
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var pointermid = pointermax;
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var pointerend = 0;
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while (pointermin < pointermid) {
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if (text1.substring(text1.length - pointermid, text1.length - pointerend) ==
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text2.substring(text2.length - pointermid, text2.length - pointerend)) {
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pointermin = pointermid;
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pointerend = pointermin;
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} else {
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pointermax = pointermid;
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}
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pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
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}
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return pointermid;
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};
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/**
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* Do the two texts share a substring which is at least half the length of the
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* longer text?
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* This speedup can produce non-minimal diffs.
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* @param {string} text1 First string.
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* @param {string} text2 Second string.
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* @return {Array.<string>} Five element Array, containing the prefix of
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* text1, the suffix of text1, the prefix of text2, the suffix of
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* text2 and the common middle. Or null if there was no match.
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*/
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function diff_halfMatch_(text1, text2) {
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var longtext = text1.length > text2.length ? text1 : text2;
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var shorttext = text1.length > text2.length ? text2 : text1;
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if (longtext.length < 4 || shorttext.length * 2 < longtext.length) {
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return null; // Pointless.
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}
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/**
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* Does a substring of shorttext exist within longtext such that the substring
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* is at least half the length of longtext?
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* Closure, but does not reference any external variables.
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* @param {string} longtext Longer string.
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* @param {string} shorttext Shorter string.
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* @param {number} i Start index of quarter length substring within longtext.
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* @return {Array.<string>} Five element Array, containing the prefix of
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* longtext, the suffix of longtext, the prefix of shorttext, the suffix
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* of shorttext and the common middle. Or null if there was no match.
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* @private
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*/
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function diff_halfMatchI_(longtext, shorttext, i) {
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// Start with a 1/4 length substring at position i as a seed.
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var seed = longtext.substring(i, i + Math.floor(longtext.length / 4));
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var j = -1;
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var best_common = '';
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var best_longtext_a, best_longtext_b, best_shorttext_a, best_shorttext_b;
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while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
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var prefixLength = diff_commonPrefix(longtext.substring(i),
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shorttext.substring(j));
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var suffixLength = diff_commonSuffix(longtext.substring(0, i),
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shorttext.substring(0, j));
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if (best_common.length < suffixLength + prefixLength) {
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best_common = shorttext.substring(j - suffixLength, j) +
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shorttext.substring(j, j + prefixLength);
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best_longtext_a = longtext.substring(0, i - suffixLength);
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best_longtext_b = longtext.substring(i + prefixLength);
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best_shorttext_a = shorttext.substring(0, j - suffixLength);
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best_shorttext_b = shorttext.substring(j + prefixLength);
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}
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}
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if (best_common.length * 2 >= longtext.length) {
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return [best_longtext_a, best_longtext_b,
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best_shorttext_a, best_shorttext_b, best_common];
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} else {
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return null;
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}
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}
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// First check if the second quarter is the seed for a half-match.
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var hm1 = diff_halfMatchI_(longtext, shorttext,
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Math.ceil(longtext.length / 4));
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// Check again based on the third quarter.
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var hm2 = diff_halfMatchI_(longtext, shorttext,
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Math.ceil(longtext.length / 2));
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var hm;
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if (!hm1 && !hm2) {
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return null;
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} else if (!hm2) {
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hm = hm1;
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} else if (!hm1) {
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hm = hm2;
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} else {
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// Both matched. Select the longest.
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hm = hm1[4].length > hm2[4].length ? hm1 : hm2;
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}
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// A half-match was found, sort out the return data.
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var text1_a, text1_b, text2_a, text2_b;
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if (text1.length > text2.length) {
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text1_a = hm[0];
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text1_b = hm[1];
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text2_a = hm[2];
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text2_b = hm[3];
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} else {
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text2_a = hm[0];
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text2_b = hm[1];
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text1_a = hm[2];
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text1_b = hm[3];
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}
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var mid_common = hm[4];
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return [text1_a, text1_b, text2_a, text2_b, mid_common];
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};
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/**
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* Reorder and merge like edit sections. Merge equalities.
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* Any edit section can move as long as it doesn't cross an equality.
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* @param {Array} diffs Array of diff tuples.
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*/
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function diff_cleanupMerge(diffs) {
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diffs.push([DIFF_EQUAL, '']); // Add a dummy entry at the end.
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var pointer = 0;
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var count_delete = 0;
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var count_insert = 0;
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var text_delete = '';
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var text_insert = '';
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var commonlength;
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while (pointer < diffs.length) {
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switch (diffs[pointer][0]) {
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case DIFF_INSERT:
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count_insert++;
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text_insert += diffs[pointer][1];
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pointer++;
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break;
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case DIFF_DELETE:
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count_delete++;
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text_delete += diffs[pointer][1];
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pointer++;
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break;
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case DIFF_EQUAL:
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// Upon reaching an equality, check for prior redundancies.
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if (count_delete + count_insert > 1) {
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if (count_delete !== 0 && count_insert !== 0) {
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// Factor out any common prefixies.
|
|
commonlength = diff_commonPrefix(text_insert, text_delete);
|
|
if (commonlength !== 0) {
|
|
if ((pointer - count_delete - count_insert) > 0 &&
|
|
diffs[pointer - count_delete - count_insert - 1][0] ==
|
|
DIFF_EQUAL) {
|
|
diffs[pointer - count_delete - count_insert - 1][1] +=
|
|
text_insert.substring(0, commonlength);
|
|
} else {
|
|
diffs.splice(0, 0, [DIFF_EQUAL,
|
|
text_insert.substring(0, commonlength)]);
|
|
pointer++;
|
|
}
|
|
text_insert = text_insert.substring(commonlength);
|
|
text_delete = text_delete.substring(commonlength);
|
|
}
|
|
// Factor out any common suffixies.
|
|
commonlength = diff_commonSuffix(text_insert, text_delete);
|
|
if (commonlength !== 0) {
|
|
diffs[pointer][1] = text_insert.substring(text_insert.length -
|
|
commonlength) + diffs[pointer][1];
|
|
text_insert = text_insert.substring(0, text_insert.length -
|
|
commonlength);
|
|
text_delete = text_delete.substring(0, text_delete.length -
|
|
commonlength);
|
|
}
|
|
}
|
|
// Delete the offending records and add the merged ones.
|
|
if (count_delete === 0) {
|
|
diffs.splice(pointer - count_insert,
|
|
count_delete + count_insert, [DIFF_INSERT, text_insert]);
|
|
} else if (count_insert === 0) {
|
|
diffs.splice(pointer - count_delete,
|
|
count_delete + count_insert, [DIFF_DELETE, text_delete]);
|
|
} else {
|
|
diffs.splice(pointer - count_delete - count_insert,
|
|
count_delete + count_insert, [DIFF_DELETE, text_delete],
|
|
[DIFF_INSERT, text_insert]);
|
|
}
|
|
pointer = pointer - count_delete - count_insert +
|
|
(count_delete ? 1 : 0) + (count_insert ? 1 : 0) + 1;
|
|
} else if (pointer !== 0 && diffs[pointer - 1][0] == DIFF_EQUAL) {
|
|
// Merge this equality with the previous one.
|
|
diffs[pointer - 1][1] += diffs[pointer][1];
|
|
diffs.splice(pointer, 1);
|
|
} else {
|
|
pointer++;
|
|
}
|
|
count_insert = 0;
|
|
count_delete = 0;
|
|
text_delete = '';
|
|
text_insert = '';
|
|
break;
|
|
}
|
|
}
|
|
if (diffs[diffs.length - 1][1] === '') {
|
|
diffs.pop(); // 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
|
|
var changes = false;
|
|
pointer = 1;
|
|
// Intentionally ignore the first and last element (don't need checking).
|
|
while (pointer < diffs.length - 1) {
|
|
if (diffs[pointer - 1][0] == DIFF_EQUAL &&
|
|
diffs[pointer + 1][0] == DIFF_EQUAL) {
|
|
// This is a single edit surrounded by equalities.
|
|
if (diffs[pointer][1].substring(diffs[pointer][1].length -
|
|
diffs[pointer - 1][1].length) == diffs[pointer - 1][1]) {
|
|
// Shift the edit over the previous equality.
|
|
diffs[pointer][1] = diffs[pointer - 1][1] +
|
|
diffs[pointer][1].substring(0, diffs[pointer][1].length -
|
|
diffs[pointer - 1][1].length);
|
|
diffs[pointer + 1][1] = diffs[pointer - 1][1] + diffs[pointer + 1][1];
|
|
diffs.splice(pointer - 1, 1);
|
|
changes = true;
|
|
} else if (diffs[pointer][1].substring(0, diffs[pointer + 1][1].length) ==
|
|
diffs[pointer + 1][1]) {
|
|
// Shift the edit over the next equality.
|
|
diffs[pointer - 1][1] += diffs[pointer + 1][1];
|
|
diffs[pointer][1] =
|
|
diffs[pointer][1].substring(diffs[pointer + 1][1].length) +
|
|
diffs[pointer + 1][1];
|
|
diffs.splice(pointer + 1, 1);
|
|
changes = true;
|
|
}
|
|
}
|
|
pointer++;
|
|
}
|
|
// If shifts were made, the diff needs reordering and another shift sweep.
|
|
if (changes) {
|
|
diff_cleanupMerge(diffs);
|
|
}
|
|
};
|
|
|
|
|
|
var diff = diff_main;
|
|
diff.INSERT = DIFF_INSERT;
|
|
diff.DELETE = DIFF_DELETE;
|
|
diff.EQUAL = DIFF_EQUAL;
|
|
|
|
module.exports = diff;
|
|
|
|
/*
|
|
* Modify a diff such that the cursor position points to the start of a change:
|
|
* E.g.
|
|
* cursor_normalize_diff([[DIFF_EQUAL, 'abc']], 1)
|
|
* => [1, [[DIFF_EQUAL, 'a'], [DIFF_EQUAL, 'bc']]]
|
|
* cursor_normalize_diff([[DIFF_INSERT, 'new'], [DIFF_DELETE, 'xyz']], 2)
|
|
* => [2, [[DIFF_INSERT, 'new'], [DIFF_DELETE, 'xy'], [DIFF_DELETE, 'z']]]
|
|
*
|
|
* @param {Array} diffs Array of diff tuples
|
|
* @param {Int} cursor_pos Suggested edit position. Must not be out of bounds!
|
|
* @return {Array} A tuple [cursor location in the modified diff, modified diff]
|
|
*/
|
|
function cursor_normalize_diff (diffs, cursor_pos) {
|
|
if (cursor_pos === 0) {
|
|
return [DIFF_EQUAL, diffs];
|
|
}
|
|
for (var current_pos = 0, i = 0; i < diffs.length; i++) {
|
|
var d = diffs[i];
|
|
if (d[0] === DIFF_DELETE || d[0] === DIFF_EQUAL) {
|
|
var next_pos = current_pos + d[1].length;
|
|
if (cursor_pos === next_pos) {
|
|
return [i + 1, diffs];
|
|
} else if (cursor_pos < next_pos) {
|
|
// copy to prevent side effects
|
|
diffs = diffs.slice();
|
|
// split d into two diff changes
|
|
var split_pos = cursor_pos - current_pos;
|
|
var d_left = [d[0], d[1].slice(0, split_pos)];
|
|
var d_right = [d[0], d[1].slice(split_pos)];
|
|
diffs.splice(i, 1, d_left, d_right);
|
|
return [i + 1, diffs];
|
|
} else {
|
|
current_pos = next_pos;
|
|
}
|
|
}
|
|
}
|
|
throw new Error('cursor_pos is out of bounds!')
|
|
}
|
|
|
|
/*
|
|
* Modify a diff such that the edit position is "shifted" to the proposed edit location (cursor_position).
|
|
*
|
|
* Case 1)
|
|
* Check if a naive shift is possible:
|
|
* [0, X], [ 1, Y] -> [ 1, Y], [0, X] (if X + Y === Y + X)
|
|
* [0, X], [-1, Y] -> [-1, Y], [0, X] (if X + Y === Y + X) - holds same result
|
|
* Case 2)
|
|
* Check if the following shifts are possible:
|
|
* [0, 'pre'], [ 1, 'prefix'] -> [ 1, 'pre'], [0, 'pre'], [ 1, 'fix']
|
|
* [0, 'pre'], [-1, 'prefix'] -> [-1, 'pre'], [0, 'pre'], [-1, 'fix']
|
|
* ^ ^
|
|
* d d_next
|
|
*
|
|
* @param {Array} diffs Array of diff tuples
|
|
* @param {Int} cursor_pos Suggested edit position. Must not be out of bounds!
|
|
* @return {Array} Array of diff tuples
|
|
*/
|
|
function fix_cursor (diffs, cursor_pos) {
|
|
var norm = cursor_normalize_diff(diffs, cursor_pos);
|
|
var ndiffs = norm[1];
|
|
var cursor_pointer = norm[0];
|
|
var d = ndiffs[cursor_pointer];
|
|
var d_next = ndiffs[cursor_pointer + 1];
|
|
|
|
if (d == null) {
|
|
// Text was deleted from end of original string,
|
|
// cursor is now out of bounds in new string
|
|
return diffs;
|
|
} else if (d[0] !== DIFF_EQUAL) {
|
|
// A modification happened at the cursor location.
|
|
// This is the expected outcome, so we can return the original diff.
|
|
return diffs;
|
|
} else {
|
|
if (d_next != null && d[1] + d_next[1] === d_next[1] + d[1]) {
|
|
// Case 1)
|
|
// It is possible to perform a naive shift
|
|
ndiffs.splice(cursor_pointer, 2, d_next, d)
|
|
return merge_tuples(ndiffs, cursor_pointer, 2)
|
|
} else if (d_next != null && d_next[1].indexOf(d[1]) === 0) {
|
|
// Case 2)
|
|
// d[1] is a prefix of d_next[1]
|
|
// We can assume that d_next[0] !== 0, since d[0] === 0
|
|
// Shift edit locations..
|
|
ndiffs.splice(cursor_pointer, 2, [d_next[0], d[1]], [0, d[1]]);
|
|
var suffix = d_next[1].slice(d[1].length);
|
|
if (suffix.length > 0) {
|
|
ndiffs.splice(cursor_pointer + 2, 0, [d_next[0], suffix]);
|
|
}
|
|
return merge_tuples(ndiffs, cursor_pointer, 3)
|
|
} else {
|
|
// Not possible to perform any modification
|
|
return diffs;
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
/*
|
|
* Try to merge tuples with their neigbors in a given range.
|
|
* E.g. [0, 'a'], [0, 'b'] -> [0, 'ab']
|
|
*
|
|
* @param {Array} diffs Array of diff tuples.
|
|
* @param {Int} start Position of the first element to merge (diffs[start] is also merged with diffs[start - 1]).
|
|
* @param {Int} length Number of consecutive elements to check.
|
|
* @return {Array} Array of merged diff tuples.
|
|
*/
|
|
function merge_tuples (diffs, start, length) {
|
|
// Check from (start-1) to (start+length).
|
|
for (var i = start + length - 1; i >= 0 && i >= start - 1; i--) {
|
|
if (i + 1 < diffs.length) {
|
|
var left_d = diffs[i];
|
|
var right_d = diffs[i+1];
|
|
if (left_d[0] === right_d[1]) {
|
|
diffs.splice(i, 2, [left_d[0], left_d[1] + right_d[1]]);
|
|
}
|
|
}
|
|
}
|
|
return diffs;
|
|
}
|