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ralph/diff.js

Created June 20, 2014 16:41
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  1. ralph created this gist Jun 20, 2014.
    1,392 changes: 1,392 additions & 0 deletions diff.js
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    Original file line number Diff line number Diff line change
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    /**
    * Diff Match and Patch
    *
    * Copyright 2006 Google Inc.
    * http://code.google.com/p/google-diff-match-patch/
    *
    * 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.
    */

    /**
    * @fileoverview Computes the difference between two texts to create a patch.
    * Applies the patch onto another text, allowing for errors.
    * @author fraser@google.com (Neil Fraser)
    */

    /**
    * Class containing the diff, match and patch methods.
    * @constructor
    */
    function diff_match_patch() {

    // Defaults.
    // Redefine these in your program to override the defaults.

    // Number of seconds to map a diff before giving up (0 for infinity).
    this.Diff_Timeout = 1.0;
    // Cost of an empty edit operation in terms of edit characters.
    this.Diff_EditCost = 4;
    // At what point is no match declared (0.0 = perfection, 1.0 = very loose).
    this.Match_Threshold = 0.5;
    // How far to search for a match (0 = exact location, 1000+ = broad match).
    // A match this many characters away from the expected location will add
    // 1.0 to the score (0.0 is a perfect match).
    this.Match_Distance = 1000;
    // When deleting a large block of text (over ~64 characters), how close do
    // the contents have to be to match the expected contents. (0.0 = perfection,
    // 1.0 = very loose). Note that Match_Threshold controls how closely the
    // end points of a delete need to match.
    this.Patch_DeleteThreshold = 0.5;
    // Chunk size for context length.
    this.Patch_Margin = 4;

    // The number of bits in an int.
    this.Match_MaxBits = 32;
    }


    // DIFF FUNCTIONS


    /**
    * The data structure representing a diff is an array of tuples:
    * [[DIFF_DELETE, 'Hello'], [DIFF_INSERT, 'Goodbye'], [DIFF_EQUAL, ' world.']]
    * which means: delete 'Hello', add 'Goodbye' and keep ' world.'
    */
    var DIFF_DELETE = -1;
    var DIFF_INSERT = 1;
    var DIFF_EQUAL = 0;

    /** @typedef {{0: number, 1: string}} */
    diff_match_patch.Diff;


    /**
    * Find the differences between two texts. Simplifies the problem by stripping
    * any common prefix or suffix off the texts before diffing.
    * @param {string} text1 Old string to be diffed.
    * @param {string} text2 New string to be diffed.
    * @param {boolean=} opt_checklines Optional speedup flag. If present and false,
    * then don't run a line-level diff first to identify the changed areas.
    * Defaults to true, which does a faster, slightly less optimal diff.
    * @param {number} opt_deadline Optional time when the diff should be complete
    * by. Used internally for recursive calls. Users should set DiffTimeout
    * instead.
    * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
    */
    diff_match_patch.prototype.diff_main = function(text1, text2, opt_checklines,
    opt_deadline) {
    // Set a deadline by which time the diff must be complete.
    if (typeof opt_deadline == 'undefined') {
    if (this.Diff_Timeout <= 0) {
    opt_deadline = Number.MAX_VALUE;
    } else {
    opt_deadline = (new Date).getTime() + this.Diff_Timeout * 1000;
    }
    }
    var deadline = opt_deadline;

    // Check for null inputs.
    if (text1 == null || text2 == null) {
    throw new Error('Null input. (diff_main)');
    }

    // Check for equality (speedup).
    if (text1 == text2) {
    if (text1) {
    return [[DIFF_EQUAL, text1]];
    }
    return [];
    }

    if (typeof opt_checklines == 'undefined') {
    opt_checklines = true;
    }
    var checklines = opt_checklines;

    // Trim off common prefix (speedup).
    var commonlength = this.diff_commonPrefix(text1, text2);
    var commonprefix = text1.substring(0, commonlength);
    text1 = text1.substring(commonlength);
    text2 = text2.substring(commonlength);

    // Trim off common suffix (speedup).
    commonlength = this.diff_commonSuffix(text1, text2);
    var commonsuffix = text1.substring(text1.length - commonlength);
    text1 = text1.substring(0, text1.length - commonlength);
    text2 = text2.substring(0, text2.length - commonlength);

    // Compute the diff on the middle block.
    var diffs = this.diff_compute_(text1, text2, checklines, deadline);

    // Restore the prefix and suffix.
    if (commonprefix) {
    diffs.unshift([DIFF_EQUAL, commonprefix]);
    }
    if (commonsuffix) {
    diffs.push([DIFF_EQUAL, commonsuffix]);
    }
    this.diff_cleanupMerge(diffs);
    return diffs;
    };


    /**
    * Find the differences between two texts. Assumes that the texts do not
    * have any common prefix or suffix.
    * @param {string} text1 Old string to be diffed.
    * @param {string} text2 New string to be diffed.
    * @param {boolean} 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 {number} deadline Time when the diff should be complete by.
    * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
    * @private
    */
    diff_match_patch.prototype.diff_compute_ = function(text1, text2, checklines,
    deadline) {
    var diffs;

    if (!text1) {
    // Just add some text (speedup).
    return [[DIFF_INSERT, text2]];
    }

    if (!text2) {
    // Just delete some text (speedup).
    return [[DIFF_DELETE, text1]];
    }

    var longtext = text1.length > text2.length ? text1 : text2;
    var shorttext = text1.length > text2.length ? text2 : text1;
    var i = longtext.indexOf(shorttext);
    if (i != -1) {
    // Shorter text is inside the longer text (speedup).
    diffs = [[DIFF_INSERT, longtext.substring(0, i)],
    [DIFF_EQUAL, shorttext],
    [DIFF_INSERT, longtext.substring(i + shorttext.length)]];
    // Swap insertions for deletions if diff is reversed.
    if (text1.length > text2.length) {
    diffs[0][0] = diffs[2][0] = DIFF_DELETE;
    }
    return diffs;
    }

    if (shorttext.length == 1) {
    // Single character string.
    // After the previous speedup, the character can't be an equality.
    return [[DIFF_DELETE, text1], [DIFF_INSERT, text2]];
    }

    // Check to see if the problem can be split in two.
    var hm = this.diff_halfMatch_(text1, text2);
    if (hm) {
    // A half-match was found, sort out the return data.
    var text1_a = hm[0];
    var text1_b = hm[1];
    var text2_a = hm[2];
    var text2_b = hm[3];
    var mid_common = hm[4];
    // Send both pairs off for separate processing.
    var diffs_a = this.diff_main(text1_a, text2_a, checklines, deadline);
    var diffs_b = this.diff_main(text1_b, text2_b, checklines, deadline);
    // Merge the results.
    return diffs_a.concat([[DIFF_EQUAL, mid_common]], diffs_b);
    }

    if (checklines && text1.length > 100 && text2.length > 100) {
    return this.diff_lineMode_(text1, text2, deadline);
    }

    return this.diff_bisect_(text1, text2, deadline);
    };


    /**
    * Do a quick line-level diff on both strings, then rediff the parts for
    * greater accuracy.
    * This speedup can produce non-minimal diffs.
    * @param {string} text1 Old string to be diffed.
    * @param {string} text2 New string to be diffed.
    * @param {number} deadline Time when the diff should be complete by.
    * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
    * @private
    */
    diff_match_patch.prototype.diff_lineMode_ = function(text1, text2, deadline) {
    // Scan the text on a line-by-line basis first.
    var a = this.diff_linesToChars_(text1, text2);
    text1 = a.chars1;
    text2 = a.chars2;
    var linearray = a.lineArray;

    var diffs = this.diff_main(text1, text2, false, deadline);

    // Convert the diff back to original text.
    this.diff_charsToLines_(diffs, linearray);
    // Eliminate freak matches (e.g. blank lines)
    this.diff_cleanupSemantic(diffs);

    // Rediff any replacement blocks, this time character-by-character.
    // Add a dummy entry at the end.
    diffs.push([DIFF_EQUAL, '']);
    var pointer = 0;
    var count_delete = 0;
    var count_insert = 0;
    var text_delete = '';
    var text_insert = '';
    while (pointer < diffs.length) {
    switch (diffs[pointer][0]) {
    case DIFF_INSERT:
    count_insert++;
    text_insert += diffs[pointer][1];
    break;
    case DIFF_DELETE:
    count_delete++;
    text_delete += diffs[pointer][1];
    break;
    case DIFF_EQUAL:
    // Upon reaching an equality, check for prior redundancies.
    if (count_delete >= 1 && count_insert >= 1) {
    // Delete the offending records and add the merged ones.
    diffs.splice(pointer - count_delete - count_insert,
    count_delete + count_insert);
    pointer = pointer - count_delete - count_insert;
    var a = this.diff_main(text_delete, text_insert, false, deadline);
    for (var j = a.length - 1; j >= 0; j--) {
    diffs.splice(pointer, 0, a[j]);
    }
    pointer = pointer + a.length;
    }
    count_insert = 0;
    count_delete = 0;
    text_delete = '';
    text_insert = '';
    break;
    }
    pointer++;
    }
    diffs.pop(); // Remove the dummy entry at the end.

    return diffs;
    };


    /**
    * Find the 'middle snake' of a diff, split the problem in two
    * and return the recursively constructed diff.
    * See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
    * @param {string} text1 Old string to be diffed.
    * @param {string} text2 New string to be diffed.
    * @param {number} deadline Time at which to bail if not yet complete.
    * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
    * @private
    */
    diff_match_patch.prototype.diff_bisect_ = function(text1, text2, deadline) {
    // Cache the text lengths to prevent multiple calls.
    var text1_length = text1.length;
    var text2_length = text2.length;
    var max_d = Math.ceil((text1_length + text2_length) / 2);
    var v_offset = max_d;
    var v_length = 2 * max_d;
    var v1 = new Array(v_length);
    var v2 = new Array(v_length);
    // Setting all elements to -1 is faster in Chrome & Firefox than mixing
    // integers and undefined.
    for (var x = 0; x < v_length; x++) {
    v1[x] = -1;
    v2[x] = -1;
    }
    v1[v_offset + 1] = 0;
    v2[v_offset + 1] = 0;
    var delta = text1_length - text2_length;
    // If the total number of characters is odd, then the front path will collide
    // with the reverse path.
    var front = (delta % 2 != 0);
    // Offsets for start and end of k loop.
    // Prevents mapping of space beyond the grid.
    var k1start = 0;
    var k1end = 0;
    var k2start = 0;
    var k2end = 0;
    for (var d = 0; d < max_d; d++) {
    // Bail out if deadline is reached.
    if ((new Date()).getTime() > deadline) {
    break;
    }

    // Walk the front path one step.
    for (var k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
    var k1_offset = v_offset + k1;
    var 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;
    }
    var y1 = x1 - k1;
    while (x1 < text1_length && y1 < text2_length &&
    text1.charAt(x1) == text2.charAt(y1)) {
    x1++;
    y1++;
    }
    v1[k1_offset] = x1;
    if (x1 > text1_length) {
    // Ran off the right of the graph.
    k1end += 2;
    } else if (y1 > text2_length) {
    // Ran off the bottom of the graph.
    k1start += 2;
    } else if (front) {
    var k2_offset = v_offset + delta - k1;
    if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {
    // Mirror x2 onto top-left coordinate system.
    var x2 = text1_length - v2[k2_offset];
    if (x1 >= x2) {
    // Overlap detected.
    return this.diff_bisectSplit_(text1, text2, x1, y1, deadline);
    }
    }
    }
    }

    // Walk the reverse path one step.
    for (var k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
    var k2_offset = v_offset + k2;
    var 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;
    }
    var y2 = x2 - k2;
    while (x2 < text1_length && y2 < text2_length &&
    text1.charAt(text1_length - x2 - 1) ==
    text2.charAt(text2_length - y2 - 1)) {
    x2++;
    y2++;
    }
    v2[k2_offset] = x2;
    if (x2 > text1_length) {
    // Ran off the left of the graph.
    k2end += 2;
    } else if (y2 > text2_length) {
    // Ran off the top of the graph.
    k2start += 2;
    } else if (!front) {
    var k1_offset = v_offset + delta - k2;
    if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {
    var x1 = v1[k1_offset];
    var y1 = v_offset + x1 - k1_offset;
    // Mirror x2 onto top-left coordinate system.
    x2 = text1_length - x2;
    if (x1 >= x2) {
    // Overlap detected.
    return this.diff_bisectSplit_(text1, text2, x1, y1, deadline);
    }
    }
    }
    }
    }
    // Diff took too long and hit the deadline or
    // number of diffs equals number of characters, no commonality at all.
    return [[DIFF_DELETE, text1], [DIFF_INSERT, text2]];
    };


    /**
    * Given the location of the 'middle snake', split the diff in two parts
    * and recurse.
    * @param {string} text1 Old string to be diffed.
    * @param {string} text2 New string to be diffed.
    * @param {number} x Index of split point in text1.
    * @param {number} y Index of split point in text2.
    * @param {number} deadline Time at which to bail if not yet complete.
    * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
    * @private
    */
    diff_match_patch.prototype.diff_bisectSplit_ = function(text1, text2, x, y,
    deadline) {
    var text1a = text1.substring(0, x);
    var text2a = text2.substring(0, y);
    var text1b = text1.substring(x);
    var text2b = text2.substring(y);

    // Compute both diffs serially.
    var diffs = this.diff_main(text1a, text2a, false, deadline);
    var diffsb = this.diff_main(text1b, text2b, false, deadline);

    return diffs.concat(diffsb);
    };


    /**
    * Split two texts into an array of strings. Reduce the texts to a string of
    * hashes where each Unicode character represents one line.
    * @param {string} text1 First string.
    * @param {string} text2 Second string.
    * @return {{chars1: string, chars2: string, lineArray: !Array.<string>}}
    * An object containing the encoded text1, the encoded text2 and
    * the array of unique strings.
    * The zeroth element of the array of unique strings is intentionally blank.
    * @private
    */
    diff_match_patch.prototype.diff_linesToChars_ = function(text1, text2) {
    var lineArray = []; // e.g. lineArray[4] == 'Hello\n'
    var lineHash = {}; // e.g. lineHash['Hello\n'] == 4

    // '\x00' is a valid character, but various debuggers don't like it.
    // So we'll insert a junk entry to avoid generating a null character.
    lineArray[0] = '';

    /**
    * Split a text into an array of strings. Reduce the texts to a string of
    * hashes where each Unicode character represents one line.
    * Modifies linearray and linehash through being a closure.
    * @param {string} text String to encode.
    * @return {string} Encoded string.
    * @private
    */
    function diff_linesToCharsMunge_(text) {
    var chars = '';
    // Walk the text, pulling out a substring for each line.
    // text.split('\n') would would temporarily double our memory footprint.
    // Modifying text would create many large strings to garbage collect.
    var lineStart = 0;
    var lineEnd = -1;
    // Keeping our own length variable is faster than looking it up.
    var lineArrayLength = lineArray.length;
    while (lineEnd < text.length - 1) {
    lineEnd = text.indexOf('\n', lineStart);
    if (lineEnd == -1) {
    lineEnd = text.length - 1;
    }
    var line = text.substring(lineStart, lineEnd + 1);
    lineStart = lineEnd + 1;

    if (lineHash.hasOwnProperty ? lineHash.hasOwnProperty(line) :
    (lineHash[line] !== undefined)) {
    chars += String.fromCharCode(lineHash[line]);
    } else {
    chars += String.fromCharCode(lineArrayLength);
    lineHash[line] = lineArrayLength;
    lineArray[lineArrayLength++] = line;
    }
    }
    return chars;
    }

    var chars1 = diff_linesToCharsMunge_(text1);
    var chars2 = diff_linesToCharsMunge_(text2);
    return {chars1: chars1, chars2: chars2, lineArray: lineArray};
    };


    /**
    * Rehydrate the text in a diff from a string of line hashes to real lines of
    * text.
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    * @param {!Array.<string>} lineArray Array of unique strings.
    * @private
    */
    diff_match_patch.prototype.diff_charsToLines_ = function(diffs, lineArray) {
    for (var x = 0; x < diffs.length; x++) {
    var chars = diffs[x][1];
    var text = [];
    for (var y = 0; y < chars.length; y++) {
    text[y] = lineArray[chars.charCodeAt(y)];
    }
    diffs[x][1] = text.join('');
    }
    };


    /**
    * Determine the common prefix of two strings.
    * @param {string} text1 First string.
    * @param {string} text2 Second string.
    * @return {number} The number of characters common to the start of each
    * string.
    */
    diff_match_patch.prototype.diff_commonPrefix = function(text1, text2) {
    // Quick check for common null cases.
    if (!text1 || !text2 || text1.charAt(0) != text2.charAt(0)) {
    return 0;
    }
    // Binary search.
    // Performance analysis: http://neil.fraser.name/news/2007/10/09/
    var pointermin = 0;
    var pointermax = Math.min(text1.length, text2.length);
    var pointermid = pointermax;
    var pointerstart = 0;
    while (pointermin < pointermid) {
    if (text1.substring(pointerstart, pointermid) ==
    text2.substring(pointerstart, pointermid)) {
    pointermin = pointermid;
    pointerstart = pointermin;
    } else {
    pointermax = pointermid;
    }
    pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
    }
    return pointermid;
    };


    /**
    * Determine the common suffix of two strings.
    * @param {string} text1 First string.
    * @param {string} text2 Second string.
    * @return {number} The number of characters common to the end of each string.
    */
    diff_match_patch.prototype.diff_commonSuffix = function(text1, text2) {
    // Quick check for common null cases.
    if (!text1 || !text2 ||
    text1.charAt(text1.length - 1) != text2.charAt(text2.length - 1)) {
    return 0;
    }
    // Binary search.
    // Performance analysis: http://neil.fraser.name/news/2007/10/09/
    var pointermin = 0;
    var pointermax = Math.min(text1.length, text2.length);
    var pointermid = pointermax;
    var pointerend = 0;
    while (pointermin < pointermid) {
    if (text1.substring(text1.length - pointermid, text1.length - pointerend) ==
    text2.substring(text2.length - pointermid, text2.length - pointerend)) {
    pointermin = pointermid;
    pointerend = pointermin;
    } else {
    pointermax = pointermid;
    }
    pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
    }
    return pointermid;
    };


    /**
    * Determine if the suffix of one string is the prefix of another.
    * @param {string} text1 First string.
    * @param {string} text2 Second string.
    * @return {number} The number of characters common to the end of the first
    * string and the start of the second string.
    * @private
    */
    diff_match_patch.prototype.diff_commonOverlap_ = function(text1, text2) {
    // Cache the text lengths to prevent multiple calls.
    var text1_length = text1.length;
    var 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.substring(text1_length - text2_length);
    } else if (text1_length < text2_length) {
    text2 = text2.substring(0, text1_length);
    }
    var text_length = Math.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/
    var best = 0;
    var length = 1;
    while (true) {
    var pattern = text1.substring(text_length - length);
    var found = text2.indexOf(pattern);
    if (found == -1) {
    return best;
    }
    length += found;
    if (found == 0 || text1.substring(text_length - length) ==
    text2.substring(0, length)) {
    best = length;
    length++;
    }
    }
    };


    /**
    * 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 {string} text1 First string.
    * @param {string} text2 Second string.
    * @return {Array.<string>} Five element 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.
    * @private
    */
    diff_match_patch.prototype.diff_halfMatch_ = function(text1, text2) {
    if (this.Diff_Timeout <= 0) {
    // Don't risk returning a non-optimal diff if we have unlimited time.
    return null;
    }
    var longtext = text1.length > text2.length ? text1 : text2;
    var shorttext = text1.length > text2.length ? text2 : text1;
    if (longtext.length < 4 || shorttext.length * 2 < longtext.length) {
    return null; // Pointless.
    }
    var dmp = this; // 'this' becomes 'window' in a closure.

    /**
    * Does a substring of shorttext exist within longtext such that the substring
    * is at least half the length of longtext?
    * Closure, but does not reference any external variables.
    * @param {string} longtext Longer string.
    * @param {string} shorttext Shorter string.
    * @param {number} i Start index of quarter length substring within longtext.
    * @return {Array.<string>} Five element Array, containing the prefix of
    * longtext, the suffix of longtext, the prefix of shorttext, the suffix
    * of shorttext and the common middle. Or null if there was no match.
    * @private
    */
    function diff_halfMatchI_(longtext, shorttext, i) {
    // Start with a 1/4 length substring at position i as a seed.
    var seed = longtext.substring(i, i + Math.floor(longtext.length / 4));
    var j = -1;
    var best_common = '';
    var best_longtext_a, best_longtext_b, best_shorttext_a, best_shorttext_b;
    while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
    var prefixLength = dmp.diff_commonPrefix(longtext.substring(i),
    shorttext.substring(j));
    var suffixLength = dmp.diff_commonSuffix(longtext.substring(0, i),
    shorttext.substring(0, j));
    if (best_common.length < suffixLength + prefixLength) {
    best_common = shorttext.substring(j - suffixLength, j) +
    shorttext.substring(j, j + prefixLength);
    best_longtext_a = longtext.substring(0, i - suffixLength);
    best_longtext_b = longtext.substring(i + prefixLength);
    best_shorttext_a = shorttext.substring(0, j - suffixLength);
    best_shorttext_b = shorttext.substring(j + prefixLength);
    }
    }
    if (best_common.length * 2 >= longtext.length) {
    return [best_longtext_a, best_longtext_b,
    best_shorttext_a, best_shorttext_b, best_common];
    } else {
    return null;
    }
    }

    // First check if the second quarter is the seed for a half-match.
    var hm1 = diff_halfMatchI_(longtext, shorttext,
    Math.ceil(longtext.length / 4));
    // Check again based on the third quarter.
    var hm2 = diff_halfMatchI_(longtext, shorttext,
    Math.ceil(longtext.length / 2));
    var hm;
    if (!hm1 && !hm2) {
    return null;
    } else if (!hm2) {
    hm = hm1;
    } else if (!hm1) {
    hm = hm2;
    } else {
    // Both matched. Select the longest.
    hm = hm1[4].length > hm2[4].length ? hm1 : hm2;
    }

    // A half-match was found, sort out the return data.
    var text1_a, text1_b, text2_a, text2_b;
    if (text1.length > text2.length) {
    text1_a = hm[0];
    text1_b = hm[1];
    text2_a = hm[2];
    text2_b = hm[3];
    } else {
    text2_a = hm[0];
    text2_b = hm[1];
    text1_a = hm[2];
    text1_b = hm[3];
    }
    var mid_common = hm[4];
    return [text1_a, text1_b, text2_a, text2_b, mid_common];
    };


    /**
    * Reduce the number of edits by eliminating semantically trivial equalities.
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    */
    diff_match_patch.prototype.diff_cleanupSemantic = function(diffs) {
    var changes = false;
    var equalities = []; // Stack of indices where equalities are found.
    var equalitiesLength = 0; // Keeping our own length var is faster in JS.
    /** @type {?string} */
    var lastequality = null;
    // Always equal to diffs[equalities[equalitiesLength - 1]][1]
    var pointer = 0; // Index of current position.
    // Number of characters that changed prior to the equality.
    var length_insertions1 = 0;
    var length_deletions1 = 0;
    // Number of characters that changed after the equality.
    var length_insertions2 = 0;
    var length_deletions2 = 0;
    while (pointer < diffs.length) {
    if (diffs[pointer][0] == DIFF_EQUAL) { // Equality found.
    equalities[equalitiesLength++] = pointer;
    length_insertions1 = length_insertions2;
    length_deletions1 = length_deletions2;
    length_insertions2 = 0;
    length_deletions2 = 0;
    lastequality = diffs[pointer][1];
    } else { // An insertion or deletion.
    if (diffs[pointer][0] == DIFF_INSERT) {
    length_insertions2 += diffs[pointer][1].length;
    } else {
    length_deletions2 += diffs[pointer][1].length;
    }
    // Eliminate an equality that is smaller or equal to the edits on both
    // sides of it.
    if (lastequality && (lastequality.length <=
    Math.max(length_insertions1, length_deletions1)) &&
    (lastequality.length <= Math.max(length_insertions2,
    length_deletions2))) {
    // Duplicate record.
    diffs.splice(equalities[equalitiesLength - 1], 0,
    [DIFF_DELETE, lastequality]);
    // Change second copy to insert.
    diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
    // Throw away the equality we just deleted.
    equalitiesLength--;
    // Throw away the previous equality (it needs to be reevaluated).
    equalitiesLength--;
    pointer = equalitiesLength > 0 ? equalities[equalitiesLength - 1] : -1;
    length_insertions1 = 0; // Reset the counters.
    length_deletions1 = 0;
    length_insertions2 = 0;
    length_deletions2 = 0;
    lastequality = null;
    changes = true;
    }
    }
    pointer++;
    }

    // Normalize the diff.
    if (changes) {
    this.diff_cleanupMerge(diffs);
    }
    this.diff_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][0] == DIFF_DELETE &&
    diffs[pointer][0] == DIFF_INSERT) {
    var deletion = diffs[pointer - 1][1];
    var insertion = diffs[pointer][1];
    var overlap_length1 = this.diff_commonOverlap_(deletion, insertion);
    var overlap_length2 = this.diff_commonOverlap_(insertion, deletion);
    if (overlap_length1 >= overlap_length2) {
    if (overlap_length1 >= deletion.length / 2 ||
    overlap_length1 >= insertion.length / 2) {
    // Overlap found. Insert an equality and trim the surrounding edits.
    diffs.splice(pointer, 0,
    [DIFF_EQUAL, insertion.substring(0, overlap_length1)]);
    diffs[pointer - 1][1] =
    deletion.substring(0, deletion.length - overlap_length1);
    diffs[pointer + 1][1] = insertion.substring(overlap_length1);
    pointer++;
    }
    } else {
    if (overlap_length2 >= deletion.length / 2 ||
    overlap_length2 >= insertion.length / 2) {
    // Reverse overlap found.
    // Insert an equality and swap and trim the surrounding edits.
    diffs.splice(pointer, 0,
    [DIFF_EQUAL, deletion.substring(0, overlap_length2)]);
    diffs[pointer - 1][0] = DIFF_INSERT;
    diffs[pointer - 1][1] =
    insertion.substring(0, insertion.length - overlap_length2);
    diffs[pointer + 1][0] = DIFF_DELETE;
    diffs[pointer + 1][1] =
    deletion.substring(overlap_length2);
    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 {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    */
    diff_match_patch.prototype.diff_cleanupSemanticLossless = function(diffs) {
    /**
    * Given two strings, compute a score representing whether the internal
    * boundary falls on logical boundaries.
    * Scores range from 6 (best) to 0 (worst).
    * Closure, but does not reference any external variables.
    * @param {string} one First string.
    * @param {string} two Second string.
    * @return {number} The score.
    * @private
    */
    function diff_cleanupSemanticScore_(one, two) {
    if (!one || !two) {
    // Edges are the best.
    return 6;
    }

    // Each port of this function behaves slightly differently due to
    // subtle differences in each language's definition of things like
    // 'whitespace'. Since this function's purpose is largely cosmetic,
    // the choice has been made to use each language's native features
    // rather than force total conformity.
    var char1 = one.charAt(one.length - 1);
    var char2 = two.charAt(0);
    var nonAlphaNumeric1 = char1.match(diff_match_patch.nonAlphaNumericRegex_);
    var nonAlphaNumeric2 = char2.match(diff_match_patch.nonAlphaNumericRegex_);
    var whitespace1 = nonAlphaNumeric1 &&
    char1.match(diff_match_patch.whitespaceRegex_);
    var whitespace2 = nonAlphaNumeric2 &&
    char2.match(diff_match_patch.whitespaceRegex_);
    var lineBreak1 = whitespace1 &&
    char1.match(diff_match_patch.linebreakRegex_);
    var lineBreak2 = whitespace2 &&
    char2.match(diff_match_patch.linebreakRegex_);
    var blankLine1 = lineBreak1 &&
    one.match(diff_match_patch.blanklineEndRegex_);
    var blankLine2 = lineBreak2 &&
    two.match(diff_match_patch.blanklineStartRegex_);

    if (blankLine1 || blankLine2) {
    // Five points for blank lines.
    return 5;
    } else if (lineBreak1 || lineBreak2) {
    // Four points for line breaks.
    return 4;
    } else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) {
    // Three points for end of sentences.
    return 3;
    } else if (whitespace1 || whitespace2) {
    // Two points for whitespace.
    return 2;
    } else if (nonAlphaNumeric1 || nonAlphaNumeric2) {
    // One point for non-alphanumeric.
    return 1;
    }
    return 0;
    }

    var 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.
    var equality1 = diffs[pointer - 1][1];
    var edit = diffs[pointer][1];
    var equality2 = diffs[pointer + 1][1];

    // First, shift the edit as far left as possible.
    var commonOffset = this.diff_commonSuffix(equality1, edit);
    if (commonOffset) {
    var commonString = edit.substring(edit.length - commonOffset);
    equality1 = equality1.substring(0, equality1.length - commonOffset);
    edit = commonString + edit.substring(0, edit.length - commonOffset);
    equality2 = commonString + equality2;
    }

    // Second, step character by character right, looking for the best fit.
    var bestEquality1 = equality1;
    var bestEdit = edit;
    var bestEquality2 = equality2;
    var bestScore = diff_cleanupSemanticScore_(equality1, edit) +
    diff_cleanupSemanticScore_(edit, equality2);
    while (edit.charAt(0) === equality2.charAt(0)) {
    equality1 += edit.charAt(0);
    edit = edit.substring(1) + equality2.charAt(0);
    equality2 = equality2.substring(1);
    var score = diff_cleanupSemanticScore_(equality1, edit) +
    diff_cleanupSemanticScore_(edit, equality2);
    // The >= encourages trailing rather than leading whitespace on edits.
    if (score >= bestScore) {
    bestScore = score;
    bestEquality1 = equality1;
    bestEdit = edit;
    bestEquality2 = equality2;
    }
    }

    if (diffs[pointer - 1][1] != bestEquality1) {
    // We have an improvement, save it back to the diff.
    if (bestEquality1) {
    diffs[pointer - 1][1] = bestEquality1;
    } else {
    diffs.splice(pointer - 1, 1);
    pointer--;
    }
    diffs[pointer][1] = bestEdit;
    if (bestEquality2) {
    diffs[pointer + 1][1] = bestEquality2;
    } else {
    diffs.splice(pointer + 1, 1);
    pointer--;
    }
    }
    }
    pointer++;
    }
    };

    // Define some regex patterns for matching boundaries.
    diff_match_patch.nonAlphaNumericRegex_ = /[^a-zA-Z0-9]/;
    diff_match_patch.whitespaceRegex_ = /\s/;
    diff_match_patch.linebreakRegex_ = /[\r\n]/;
    diff_match_patch.blanklineEndRegex_ = /\n\r?\n$/;
    diff_match_patch.blanklineStartRegex_ = /^\r?\n\r?\n/;

    /**
    * Reduce the number of edits by eliminating operationally trivial equalities.
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    */
    diff_match_patch.prototype.diff_cleanupEfficiency = function(diffs) {
    var changes = false;
    var equalities = []; // Stack of indices where equalities are found.
    var equalitiesLength = 0; // Keeping our own length var is faster in JS.
    /** @type {?string} */
    var lastequality = null;
    // Always equal to diffs[equalities[equalitiesLength - 1]][1]
    var pointer = 0; // Index of current position.
    // Is there an insertion operation before the last equality.
    var pre_ins = false;
    // Is there a deletion operation before the last equality.
    var pre_del = false;
    // Is there an insertion operation after the last equality.
    var post_ins = false;
    // Is there a deletion operation after the last equality.
    var post_del = false;
    while (pointer < diffs.length) {
    if (diffs[pointer][0] == DIFF_EQUAL) { // Equality found.
    if (diffs[pointer][1].length < this.Diff_EditCost &&
    (post_ins || post_del)) {
    // Candidate found.
    equalities[equalitiesLength++] = pointer;
    pre_ins = post_ins;
    pre_del = post_del;
    lastequality = diffs[pointer][1];
    } else {
    // Not a candidate, and can never become one.
    equalitiesLength = 0;
    lastequality = null;
    }
    post_ins = post_del = false;
    } else { // An insertion or deletion.
    if (diffs[pointer][0] == DIFF_DELETE) {
    post_del = true;
    } else {
    post_ins = true;
    }
    /*
    * Five types to be split:
    * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
    * <ins>A</ins>X<ins>C</ins><del>D</del>
    * <ins>A</ins><del>B</del>X<ins>C</ins>
    * <ins>A</del>X<ins>C</ins><del>D</del>
    * <ins>A</ins><del>B</del>X<del>C</del>
    */
    if (lastequality && ((pre_ins && pre_del && post_ins && post_del) ||
    ((lastequality.length < this.Diff_EditCost / 2) &&
    (pre_ins + pre_del + post_ins + post_del) == 3))) {
    // Duplicate record.
    diffs.splice(equalities[equalitiesLength - 1], 0,
    [DIFF_DELETE, lastequality]);
    // Change second copy to insert.
    diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
    equalitiesLength--; // Throw away the equality we just deleted;
    lastequality = null;
    if (pre_ins && pre_del) {
    // No changes made which could affect previous entry, keep going.
    post_ins = post_del = true;
    equalitiesLength = 0;
    } else {
    equalitiesLength--; // Throw away the previous equality.
    pointer = equalitiesLength > 0 ?
    equalities[equalitiesLength - 1] : -1;
    post_ins = post_del = false;
    }
    changes = true;
    }
    }
    pointer++;
    }

    if (changes) {
    this.diff_cleanupMerge(diffs);
    }
    };


    /**
    * Reorder and merge like edit sections. Merge equalities.
    * Any edit section can move as long as it doesn't cross an equality.
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    */
    diff_match_patch.prototype.diff_cleanupMerge = function(diffs) {
    diffs.push([DIFF_EQUAL, '']); // Add a dummy entry at the end.
    var pointer = 0;
    var count_delete = 0;
    var count_insert = 0;
    var text_delete = '';
    var text_insert = '';
    var commonlength;
    while (pointer < diffs.length) {
    switch (diffs[pointer][0]) {
    case DIFF_INSERT:
    count_insert++;
    text_insert += diffs[pointer][1];
    pointer++;
    break;
    case DIFF_DELETE:
    count_delete++;
    text_delete += diffs[pointer][1];
    pointer++;
    break;
    case DIFF_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.
    commonlength = this.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 = this.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) {
    this.diff_cleanupMerge(diffs);
    }
    };


    /**
    * loc is a location in text1, compute and return the equivalent location in
    * text2.
    * e.g. 'The cat' vs 'The big cat', 1->1, 5->8
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    * @param {number} loc Location within text1.
    * @return {number} Location within text2.
    */
    diff_match_patch.prototype.diff_xIndex = function(diffs, loc) {
    var chars1 = 0;
    var chars2 = 0;
    var last_chars1 = 0;
    var last_chars2 = 0;
    var x;
    for (x = 0; x < diffs.length; x++) {
    if (diffs[x][0] !== DIFF_INSERT) { // Equality or deletion.
    chars1 += diffs[x][1].length;
    }
    if (diffs[x][0] !== DIFF_DELETE) { // Equality or insertion.
    chars2 += diffs[x][1].length;
    }
    if (chars1 > loc) { // Overshot the location.
    break;
    }
    last_chars1 = chars1;
    last_chars2 = chars2;
    }
    // Was the location was deleted?
    if (diffs.length != x && diffs[x][0] === DIFF_DELETE) {
    return last_chars2;
    }
    // Add the remaining character length.
    return last_chars2 + (loc - last_chars1);
    };


    /**
    * Convert a diff array into a pretty HTML report.
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    * @return {string} HTML representation.
    */
    diff_match_patch.prototype.diff_prettyHtml = function(diffs) {
    var html = [];
    var pattern_amp = /&/g;
    var pattern_lt = /</g;
    var pattern_gt = />/g;
    var pattern_para = /\n/g;
    for (var x = 0; x < diffs.length; x++) {
    var op = diffs[x][0]; // Operation (insert, delete, equal)
    var data = diffs[x][1]; // Text of change.
    var text = data.replace(pattern_amp, '&amp;').replace(pattern_lt, '&lt;')
    .replace(pattern_gt, '&gt;').replace(pattern_para, '&para;<br>');
    switch (op) {
    case DIFF_INSERT:
    html[x] = '<ins style="background:#e6ffe6;">' + text + '</ins>';
    break;
    case DIFF_DELETE:
    html[x] = '<del style="background:#ffe6e6;">' + text + '</del>';
    break;
    case DIFF_EQUAL:
    html[x] = '<span>' + text + '</span>';
    break;
    }
    }
    return html.join('');
    };


    /**
    * Compute and return the source text (all equalities and deletions).
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    * @return {string} Source text.
    */
    diff_match_patch.prototype.diff_text1 = function(diffs) {
    var text = [];
    for (var x = 0; x < diffs.length; x++) {
    if (diffs[x][0] !== DIFF_INSERT) {
    text[x] = diffs[x][1];
    }
    }
    return text.join('');
    };


    /**
    * Compute and return the destination text (all equalities and insertions).
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    * @return {string} Destination text.
    */
    diff_match_patch.prototype.diff_text2 = function(diffs) {
    var text = [];
    for (var x = 0; x < diffs.length; x++) {
    if (diffs[x][0] !== DIFF_DELETE) {
    text[x] = diffs[x][1];
    }
    }
    return text.join('');
    };


    /**
    * Compute the Levenshtein distance; the number of inserted, deleted or
    * substituted characters.
    * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    * @return {number} Number of changes.
    */
    diff_match_patch.prototype.diff_levenshtein = function(diffs) {
    var levenshtein = 0;
    var insertions = 0;
    var deletions = 0;
    for (var x = 0; x < diffs.length; x++) {
    var op = diffs[x][0];
    var data = diffs[x][1];
    switch (op) {
    case DIFF_INSERT:
    insertions += data.length;
    break;
    case DIFF_DELETE:
    deletions += data.length;
    break;
    case DIFF_EQUAL:
    // A deletion and an insertion is one substitution.
    levenshtein += Math.max(insertions, deletions);
    insertions = 0;
    deletions = 0;
    break;
    }
    }
    levenshtein += Math.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 {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
    * @return {string} Delta text.
    */
    diff_match_patch.prototype.diff_toDelta = function(diffs) {
    var text = [];
    for (var x = 0; x < diffs.length; x++) {
    switch (diffs[x][0]) {
    case DIFF_INSERT:
    text[x] = '+' + encodeURI(diffs[x][1]);
    break;
    case DIFF_DELETE:
    text[x] = '-' + diffs[x][1].length;
    break;
    case DIFF_EQUAL:
    text[x] = '=' + diffs[x][1].length;
    break;
    }
    }
    return text.join('\t').replace(/%20/g, ' ');
    };


    /**
    * Given the original text1, and an encoded string which describes the
    * operations required to transform text1 into text2, compute the full diff.
    * @param {string} text1 Source string for the diff.
    * @param {string} delta Delta text.
    * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
    * @throws {!Error} If invalid input.
    */
    diff_match_patch.prototype.diff_fromDelta = function(text1, delta) {
    var diffs = [];
    var diffsLength = 0; // Keeping our own length var is faster in JS.
    var pointer = 0; // Cursor in text1
    var tokens = delta.split(/\t/g);
    for (var x = 0; x < tokens.length; x++) {
    // Each token begins with a one character parameter which specifies the
    // operation of this token (delete, insert, equality).
    var param = tokens[x].substring(1);
    switch (tokens[x].charAt(0)) {
    case '+':
    try {
    diffs[diffsLength++] = [DIFF_INSERT, decodeURI(param)];
    } catch (ex) {
    // Malformed URI sequence.
    throw new Error('Illegal escape in diff_fromDelta: ' + param);
    }
    break;
    case '-':
    // Fall through.
    case '=':
    var n = parseInt(param, 10);
    if (isNaN(n) || n < 0) {
    throw new Error('Invalid number in diff_fromDelta: ' + param);
    }
    var text = text1.substring(pointer, pointer += n);
    if (tokens[x].charAt(0) == '=') {
    diffs[diffsLength++] = [DIFF_EQUAL, text];
    } else {
    diffs[diffsLength++] = [DIFF_DELETE, text];
    }
    break;
    default:
    // Blank tokens are ok (from a trailing \t).
    // Anything else is an error.
    if (tokens[x]) {
    throw new Error('Invalid diff operation in diff_fromDelta: ' +
    tokens[x]);
    }
    }
    }
    if (pointer != text1.length) {
    throw new Error('Delta length (' + pointer +
    ') does not equal source text length (' + text1.length + ').');
    }
    return diffs;
    };