Remove product literal strings in "pht()", part 5

[phabricator.git] / externals / diff_match_patch / diff_match_patch.php

<?php
/**
 * Diff Match and Patch
 *
 * Copyright 2006 Google Inc.
 * http://code.google.com/p/google-diff-match-patch/
 *
 * php port by Tobias Buschor shwups.ch
 *
 * 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
 */
class 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).
        public $Diff_Timeout = 1.0;
        // Cost of an empty edit operation in terms of edit characters.
        public $Diff_EditCost = 4;
        // The size beyond which the double-ended diff activates.
        // Double-ending is twice as fast, but less accurate.
        public $Diff_DualThreshold = 32;
        // At what point is no match declared (0.0 = perfection, 1.0 = very loose).
        public $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).
        public $Match_Distance = 1000;
        // When deleting a large block of text (over ~64 characters), how close does
        // the contents have 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.
        public $Patch_DeleteThreshold = 0.5;
        // Chunk size for context length.
        public $Patch_Margin = 4;

        /**
         * Compute the number of bits in an int.
         * The normal answer for JavaScript is 32.
         * @return {number} Max bits

        function getMaxBits() {
                var maxbits = 0;
                var oldi = 1;
                var newi = 2;
                while (oldi != newi) {
                        maxbits++;
                        oldi = newi;
                        newi = newi << 1;
                }
                return maxbits;
        }
        // How many bits in a number?
        this.Match_MaxBits = getMaxBits();
        */
        //  DIFF FUNCTIONS

        /**
         * 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
         * @return {Array.<Array.<number|string>>} Array of diff tuples.
         */
        function diff_main($text1, $text2, $checklines = true) {
                // Check for equality (speedup)
                if ($text1 === $text2) {
                        return array ( array ( DIFF_EQUAL, $text1) );
                }

                // Trim off common prefix (speedup)
                $commonlength = $this->diff_commonPrefix($text1, $text2);
                $commonprefix = mb_substr($text1, 0, $commonlength);
                $text1 = mb_substr($text1, $commonlength);
                $text2 = mb_substr($text2, $commonlength);

                // Trim off common suffix (speedup)
                $commonlength = $this->diff_commonSuffix($text1, $text2);
                $commonsuffix = mb_substr($text1, mb_strlen($text1) - $commonlength);
                $text1 = mb_substr($text1, 0, mb_strlen($text1) - $commonlength);
                $text2 = mb_substr($text2, 0, mb_strlen($text2) - $commonlength);

                // Compute the diff on the middle block
                $diffs = $this->diff_compute($text1, $text2, $checklines);

                // Restore the prefix and suffix
                if ($commonprefix !== '') {
                        array_unshift($diffs, array ( DIFF_EQUAL, $commonprefix ));
                }
                if ($commonsuffix !== '') {
                        array_push($diffs, array ( 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
         * @return {Array.<Array.<number|string>>} Array of diff tuples.
         * @private
         */
        function diff_compute($text1, $text2, $checklines) {

                if ($text1 === '') {
                        // Just add some text (speedup)
                        return array ( array ( DIFF_INSERT, $text2 ) );
                }

                if ($text2 === '') {
                        // Just delete some text (speedup)
                        return array ( array ( DIFF_DELETE, $text1 ) );
                }

                $longtext = mb_strlen($text1) > mb_strlen($text2) ? $text1 : $text2;
                $shorttext = mb_strlen($text1) > mb_strlen($text2) ? $text2 : $text1;
                $i = mb_strpos($longtext, $shorttext);
                if ($i !== false) {
                        // Shorter text is inside the longer text (speedup)
                        $diffs = array (
                                array ( DIFF_INSERT, mb_substr($longtext, 0, $i) ),
                                array ( DIFF_EQUAL, $shorttext ),
                                array ( DIFF_INSERT, mb_substr($longtext, $i +mb_strlen($shorttext)) )
                        );

                        // Swap insertions for deletions if diff is reversed.
                        if (mb_strlen($text1) > mb_strlen($text2)) {
                                $diffs[0][0] = $diffs[2][0] = DIFF_DELETE;
                        }
                        return $diffs;
                }
                $longtext = $shorttext = null; // Garbage collect

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

                // Perform a real diff.
                if ($checklines && (mb_strlen($text1) < 100 || mb_strlen($text2) < 100)) {
                        // Too trivial for the overhead.
                        $checklines = false;
                }
                $linearray = null;
                if ($checklines) {
                        // Scan the text on a line-by-line basis first.
                        $a = $this->diff_linesToChars($text1, $text2);
                        $text1 = $a[0];
                        $text2 = $a[1];
                        $linearray = $a[2];
                }
                $diffs = $this->diff_map($text1, $text2);
                if (!$diffs) {
                        // No acceptable result.
                        $diffs = array (
                                array (
                                        DIFF_DELETE,
                                        $text1
                                ),
                                array (
                                        DIFF_INSERT,
                                        $text2
                                )
                        );
                }
                if ($checklines) {
                        // 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.
                        array_push($diffs, array (
                                DIFF_EQUAL,
                                ''
                        ));
                        $pointer = 0;
                        $count_delete = 0;
                        $count_insert = 0;
                        $text_delete = '';
                        $text_insert = '';
                        while ($pointer < count($diffs)) {
                                switch ($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.
                                                        $a = $this->diff_main($text_delete, $text_insert, false);
                                                        array_splice($diffs, $pointer - $count_delete - $count_insert, $count_delete + $count_insert);

                                                        $pointer = $pointer - $count_delete - $count_insert;
                                                        for ($j = count($a) - 1; $j >= 0; $j--) {
                                                                array_splice($diffs, $pointer, 0, array($a[$j]));
                                                        }
                                                        $pointer = $pointer +count($a);
                                                }
                                                $count_insert = 0;
                                                $count_delete = 0;
                                                $text_delete = '';
                                                $text_insert = '';
                                                break;
                                }
                                $pointer++;
                        }
                        array_pop($diffs); // Remove the dummy entry at the end.
                }
                return $diffs;
        }

        /**
         * 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 {Array.<string|Array.<string>>} Three element Array, 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
         */
        function diff_linesToChars($text1, $text2) {
                $lineArray = array(); // e.g. lineArray[4] == 'Hello\n'
                $lineHash = array(); // 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] = '';

                $chars1 = $this->diff_linesToCharsMunge($text1, $lineArray, $lineHash);
                $chars2 = $this->diff_linesToCharsMunge($text2, $lineArray, $lineHash);
                return array (
                        $chars1,
                        $chars2,
                        $lineArray
                );
        }

        /**
         * 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($text, &$lineArray, &$lineHash) {
                $chars = '';
                // Walk the text, pulling out a mb_substring for each line.
                // text.split('\n') would would temporarily double our memory footprint.
                // Modifying text would create many large strings to garbage collect.
                $lineStart = 0;
                $lineEnd = -1;
                // Keeping our own length variable is faster than looking it up.
                $lineArrayLength = count($lineArray);
                while ($lineEnd < mb_strlen($text) - 1) {
                        $lineEnd = mb_strpos($text, "\n", $lineStart);
                        if ($lineEnd === false) {
                                $lineEnd = mb_strlen($text) - 1;
                        }
                        $line = mb_substr($text, $lineStart, $lineEnd +1 -$lineStart);
                        $lineStart = $lineEnd +1;

                        if ( isset($lineHash[$line]) ) {
                                $chars .= mb_chr($lineHash[$line]);
                        } else {
                                $chars .= mb_chr($lineArrayLength);
                                $lineHash[$line] = $lineArrayLength;
                                $lineArray[$lineArrayLength++] = $line;
                        }
                }
                return $chars;
        }
        /**
         * Rehydrate the text in a diff from a string of line hashes to real lines of
         * text.
         * @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
         * @param {Array.<string>} lineArray Array of unique strings.
         * @private
         */
        function diff_charsToLines(&$diffs, $lineArray) {
                for ($x = 0; $x < count($diffs); $x++) {
                        $chars = $diffs[$x][1];
                        $text = array ();
                        for ($y = 0; $y < mb_strlen($chars); $y++) {
                                $text[$y] = $lineArray[charCodeAt($chars, $y)];
                        }
                        $diffs[$x][1] = implode('',$text);
                }
        }

        /**
         * Explore the intersection points between the two texts.
         * @param {string} text1 Old string to be diffed.
         * @param {string} text2 New string to be diffed.
         * @return {Array.<Array.<number|string>>?} Array of diff tuples or null if no
         *     diff available.
         * @private
         */
        function diff_map($text1, $text2) {
                // Don't run for too long.
                $ms_end = microtime(true) + $this->Diff_Timeout;
                
                // Cache the text lengths to prevent multiple calls.
                $text1_length = mb_strlen($text1);
                $text2_length = mb_strlen($text2);
                $max_d = $text1_length + $text2_length -1;
                $doubleEnd = $this->Diff_DualThreshold * 2 < $max_d;
                $v_map1 = array();
                $v_map2 = array();
                $v1 = array();
                $v2 = array();
                $v1[1] = 0;
                $v2[1] = 0;
                $x = null;
                $y = null;
                $footstep = null; // Used to track overlapping paths.
                $footsteps = array();
                $done = false;
                // Safari 1.x doesn't have hasOwnProperty
                //?    $hasOwnProperty = !!(footsteps.hasOwnProperty);
                // If the total number of characters is odd, then the front path will collide
                // with the reverse path.
                $front = ($text1_length + $text2_length) % 2;
                for ($d = 0; $d < $max_d; $d++) {
                        // Bail out if timeout reached.
                        if ($this->Diff_Timeout > 0 && microtime(true) > $ms_end) {
                                return null; // zzz
                        }

                        // Walk the front path one step.
                        $v_map1[$d] = array ();
                        for ($k = -$d; $k <= $d; $k += 2) {
                                if ($k == -$d || $k != $d && $v1[$k -1] < $v1[$k +1]) {
                                        $x = $v1[$k +1];
                                } else {
                                        $x = $v1[$k -1] + 1;
                                }
                                $y = $x - $k;
                                if ($doubleEnd) {
                                        $footstep = $x . ',' . $y;
                                        if ($front && isset ($footsteps[$footstep])) {
                                                $done = true;
                                        }
                                        if (!$front) {
                                                $footsteps[$footstep] = $d;
                                        }
                                }
                                while (!$done && ($x < $text1_length) && ($y < $text2_length) && (mb_substr($text1, $x, 1) == mb_substr($text2, $y, 1)) ) {
                                        $x++;
                                        $y++;
                                        if ($doubleEnd) {
                                                $footstep = $x . ',' . $y;
                                                if ($front && isset ($footsteps[$footstep])) {
                                                        $done = true;
                                                }
                                                if (!$front) {
                                                        $footsteps[$footstep] = $d;
                                                }
                                        }
                                }
                                $v1[$k] = $x;
                                $v_map1[$d][$x . ',' . $y] = true;
                                if ($x == $text1_length && $y == $text2_length) {
                                        // Reached the end in single-path mode.
                                        return $this->diff_path1($v_map1, $text1, $text2);
                                }
                                elseif ($done) {
                                        // Front path ran over reverse path.

                                        $v_map2 = array_slice($v_map2, 0, $footsteps[$footstep] + 1);
                                        $a = $this->diff_path1($v_map1, mb_substr($text1, 0, $x), mb_substr($text2, 0, $y));

                                        return array_merge($a, $this->diff_path2($v_map2, mb_substr($text1, $x), mb_substr($text2, $y)));
                                }
                        }

                        if ($doubleEnd) {
                                // Walk the reverse path one step.
                                $v_map2[$d] = array();
                                for ($k = -$d; $k <= $d; $k += 2) {
                                        if ($k == -$d || $k != $d && $v2[$k -1] < $v2[$k +1]) {
                                                $x = $v2[$k +1];
                                        } else {
                                                $x = $v2[$k -1] + 1;
                                        }
                                        $y = $x - $k;
                                        $footstep = ($text1_length - $x) . ',' . ($text2_length - $y);
                                        if (!$front && isset ($footsteps[$footstep])) {
                                                $done = true;
                                        }
                                        if ($front) {
                                                $footsteps[$footstep] = $d;
                                        }
                                        while (!$done && $x < $text1_length && $y < $text2_length && mb_substr($text1, $text1_length - $x -1, 1) == mb_substr($text2, $text2_length - $y -1, 1) ) {
                                                $x++;
                                                $y++;
                                                $footstep = ($text1_length - $x) . ',' . ($text2_length - $y);
                                                if (!$front && isset ($footsteps[$footstep])) {
                                                        $done = true;
                                                }
                                                if ($front) {
                                                        $footsteps[$footstep] = $d;
                                                }
                                        }
                                        $v2[$k] = $x;
                                        $v_map2[$d][$x . ',' . $y] = true;
                                        if ($done) {
                                                // Reverse path ran over front path.
                                                $v_map1 = array_slice($v_map1, 0, $footsteps[$footstep] + 1);
                                                $a = $this->diff_path1($v_map1, mb_substr($text1, 0, $text1_length - $x), mb_substr($text2, 0, $text2_length - $y));
                                                return array_merge($a, $this->diff_path2($v_map2, mb_substr($text1, $text1_length - $x), mb_substr($text2, $text2_length - $y)));
                                        }
                                }
                        }
                }
                // Number of diffs equals number of characters, no commonality at all.
                return null;
        }

        /**
         * Work from the middle back to the start to determine the path.
         * @param {Array.<Object>} v_map Array of paths.ers
         * @param {string} text1 Old string fragment to be diffed.
         * @param {string} text2 New string fragment to be diffed.
         * @return {Array.<Array.<number|string>>} Array of diff tuples.
         * @private
         */
        function diff_path1($v_map, $text1, $text2) {
                $path = array ();
                $x = mb_strlen($text1);
                $y = mb_strlen($text2);
                /** @type {number?} */
                $last_op = null;
                for ($d = count($v_map) - 2; $d >= 0; $d--) {
                        while (1) {
                                if (isset ($v_map[$d][($x -1) . ',' . $y])) {
                                        $x--;
                                        if ($last_op === DIFF_DELETE) {
                                                $path[0][1] = mb_substr($text1, $x, 1) . $path[0][1];
                                        } else {
                                                array_unshift($path, array (
                                                        DIFF_DELETE,
                                                        mb_substr($text1, $x, 1)
                                                ));
                                        }
                                        $last_op = DIFF_DELETE;
                                        break;
                                } elseif (isset ($v_map[$d][$x . ',' . ($y -1)])) {
                                        $y--;
                                        if ($last_op === DIFF_INSERT) {
                                                $path[0][1] = mb_substr($text2, $y, 1) . $path[0][1];
                                        } else {
                                                array_unshift($path, array (
                                                        DIFF_INSERT,
                                                        mb_substr($text2, $y, 1)
                                                ));
                                        }
                                        $last_op = DIFF_INSERT;
                                        break;
                                } else {
                                        $x--;
                                        $y--;
                                        //if (text1.charAt(x) != text2.charAt(y)) {
                                        //  throw new Error('No diagonal.  Can\'t happen. (diff_path1)');
                                        //}
                                        if ($last_op === DIFF_EQUAL) {
                                                $path[0][1] = mb_substr($text1, $x, 1) . $path[0][1];
                                        } else {
                                                array_unshift($path, array (
                                                        DIFF_EQUAL,
                                                        mb_substr($text1, $x, 1)
                                                ));
                                        }
                                        $last_op = DIFF_EQUAL;
                                }
                        }
                }
                return $path;
        }

        /**
         * Work from the middle back to the end to determine the path.
         * @param {Array.<Object>} v_map Array of paths.
         * @param {string} text1 Old string fragment to be diffed.
         * @param {string} text2 New string fragment to be diffed.
         * @return {Array.<Array.<number|string>>} Array of diff tuples.
         * @private
         */
        function diff_path2($v_map, $text1, $text2) {
                $path = array ();
                $pathLength = 0;
                $x = mb_strlen($text1);
                $y = mb_strlen($text2);
                /** @type {number?} */
                $last_op = null;
                for ($d = count($v_map) - 2; $d >= 0; $d--) {
                        while (1) {
                                if (isset ($v_map[$d][($x -1) . ',' . $y])) {
                                        $x--;
                                        if ($last_op === DIFF_DELETE) {
                                                $path[$pathLength -1][1] .= $text1[mb_strlen($text1) - $x -1];
                                        } else {
                                                $path[$pathLength++] = array (
                                                        DIFF_DELETE,
                                                        $text1[mb_strlen($text1) - $x -1]
                                                );
                                        }
                                        $last_op = DIFF_DELETE;
                                        break;
                                }
                                elseif (isset ($v_map[$d][$x . ',' . ($y -1)])) {
                                        $y--;
                                        if ($last_op === DIFF_INSERT) {
                                                $path[$pathLength -1][1] .= $text2[mb_strlen($text2) - $y -1];
                                        } else {
                                                $path[$pathLength++] = array (
                                                        DIFF_INSERT,
                                                        $text2[mb_strlen($text2) - $y -1]
                                                );
                                        }
                                        $last_op = DIFF_INSERT;
                                        break;
                                } else {
                                        $x--;
                                        $y--;
                                        //if (text1.charAt(text1.length - x - 1) !=
                                        //    text2.charAt(text2.length - y - 1)) {
                                        //  throw new Error('No diagonal.  Can\'t happen. (diff_path2)');
                                        //}
                                        if ($last_op === DIFF_EQUAL) {
                                                $path[$pathLength -1][1] .= $text1[mb_strlen($text1) - $x -1];
                                        } else {
                                                $path[$pathLength++] = array (
                                                        DIFF_EQUAL,
                                                        $text1[mb_strlen($text1) - $x -1]
                                                );
                                        }
                                        $last_op = DIFF_EQUAL;
                                }
                        }
                }
                return $path;
        }

        /**
         * 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.
         */
        function diff_commonPrefix($text1, $text2) {
                for ($i = 0; 1; $i++) {
                        $t1 = mb_substr($text1, $i, 1);
                        $t2 = mb_substr($text2, $i, 1);
                        if($t1==='' || $t2==='' || $t1 !== $t2 ){
                                return $i;
                        }
                }
        }

        /**
         * 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.
         */
        function diff_commonSuffix($text1, $text2) {
                return $this->diff_commonPrefix( strrev($text1), strrev($text2) );
        }

        /**
         * Do the two texts share a mb_substring which is at least half the length of the
         * longer text?
         * @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.
         */
        function diff_halfMatch($text1, $text2) {
                $longtext = mb_strlen($text1) > mb_strlen($text2) ? $text1 : $text2;
                $shorttext = mb_strlen($text1) > mb_strlen($text2) ? $text2 : $text1;
                if (mb_strlen($longtext) < 10 || mb_strlen($shorttext) < 1) {
                        return null; // Pointless.
                }

                // First check if the second quarter is the seed for a half-match.
                $hm1 = $this->diff_halfMatchI($longtext, $shorttext, ceil(mb_strlen($longtext) / 4));
                // Check again based on the third quarter.
                $hm2 = $this->diff_halfMatchI($longtext, $shorttext, ceil(mb_strlen($longtext) / 2));

                if (!$hm1 && !$hm2) {
                        return null;
                } elseif (!$hm2) {
                        $hm = $hm1;
                } elseif (!$hm1) {
                        $hm = $hm2;
                } else {
                        // Both matched.  Select the longest.
                        $hm = mb_strlen($hm1[4]) > mb_strlen($hm2[4]) ? $hm1 : $hm2;
                }

                // A half-match was found, sort out the return data.
                if (mb_strlen($text1) > mb_strlen($text2)) {
                        $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];
                }
                $mid_common = $hm[4];
                return array( $text1_a, $text1_b, $text2_a, $text2_b, $mid_common );
        }

        /**
         * Does a mb_substring of shorttext exist within longtext such that the mb_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 mb_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 mb_substring at position i as a seed.
                $seed = mb_substr($longtext, $i, floor(mb_strlen($longtext) / 4));

                $j = -1;
                $best_common = '';
                $best_longtext_a = null;
                $best_longtext_b = null;
                $best_shorttext_a = null;
                $best_shorttext_b = null;
                while ( ($j = mb_strpos($shorttext, $seed, $j + 1)) !== false ) {
                        $prefixLength = $this->diff_commonPrefix(mb_substr($longtext, $i), mb_substr($shorttext, $j));
                        $suffixLength = $this->diff_commonSuffix(mb_substr($longtext, 0, $i), mb_substr($shorttext, 0, $j));
                        if (mb_strlen($best_common) < $suffixLength + $prefixLength) {
                                $best_common = mb_substr($shorttext, $j - $suffixLength, $suffixLength) . mb_substr($shorttext, $j, $prefixLength);
                                $best_longtext_a = mb_substr($longtext, 0, $i - $suffixLength);
                                $best_longtext_b = mb_substr($longtext, $i + $prefixLength);
                                $best_shorttext_a = mb_substr($shorttext, 0, $j - $suffixLength);
                                $best_shorttext_b = mb_substr($shorttext, $j + $prefixLength);
                        }
                }
                if (mb_strlen($best_common) >= mb_strlen($longtext) / 2) {
                        return array (
                                $best_longtext_a,
                                $best_longtext_b,
                                $best_shorttext_a,
                                $best_shorttext_b,
                                $best_common
                        );
                } else {
                        return null;
                }
        }

        /**
         * Reduce the number of edits by eliminating semantically trivial equalities.
         * @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
         */
        function diff_cleanupSemantic(&$diffs) {
                $changes = false;
                $equalities = array (); // Stack of indices where equalities are found.
                $equalitiesLength = 0; // Keeping our own length var is faster in JS.
                $lastequality = null; // Always equal to equalities[equalitiesLength-1][1]
                $pointer = 0; // Index of current position.
                // Number of characters that changed prior to the equality.
                $length_changes1 = 0;
                // Number of characters that changed after the equality.
                $length_changes2 = 0;
                while ($pointer < count($diffs)) {
                        if ($diffs[$pointer][0] == DIFF_EQUAL) { // equality found
                                $equalities[$equalitiesLength++] = $pointer;
                                $length_changes1 = $length_changes2;
                                $length_changes2 = 0;
                                $lastequality = $diffs[$pointer][1];
                        } else { // an insertion or deletion
                                $length_changes2 += mb_strlen($diffs[$pointer][1]);
                                if ($lastequality !== null && (mb_strlen($lastequality) <= $length_changes1) && (mb_strlen($lastequality) <= $length_changes2)) {
                                        // Duplicate record
                                        $zzz_diffs = array_splice($diffs, $equalities[$equalitiesLength -1], 0, array(array (
                                                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_changes1 = 0; // Reset the counters.
                                        $length_changes2 = 0;
                                        $lastequality = null;
                                        $changes = true;
                                }
                        }
                        $pointer++;
                }
                if ($changes) {
                        $this->diff_cleanupMerge($diffs);
                }
                $this->diff_cleanupSemanticLossless($diffs);
        }

        /**
         * 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.<Array.<number|string>>} diffs Array of diff tuples.
         */
        function diff_cleanupSemanticLossless(&$diffs) {

                $pointer = 1;
                // Intentionally ignore the first and last element (don't need checking).
                while ($pointer < count($diffs) - 1) {
                        if ($diffs[$pointer -1][0] == DIFF_EQUAL && $diffs[$pointer +1][0] == DIFF_EQUAL) {
                                // This is a single edit surrounded by equalities.
                                $equality1 = $diffs[$pointer -1][1];
                                $edit = $diffs[$pointer][1];
                                $equality2 = $diffs[$pointer +1][1];

                                // First, shift the edit as far left as possible.
                                $commonOffset = $this->diff_commonSuffix($equality1, $edit);
                                if ($commonOffset !== '') {
                                        $commonString = mb_substr($edit, mb_strlen($edit) - $commonOffset);
                                        $equality1 = mb_substr($equality1, 0, mb_strlen($equality1) - $commonOffset);
                                        $edit = $commonString . mb_substr($edit, 0, mb_strlen($edit) - $commonOffset);
                                        $equality2 = $commonString . $equality2;
                                }

                                // Second, step character by character right, looking for the best fit.
                                $bestEquality1 = $equality1;
                                $bestEdit = $edit;
                                $bestEquality2 = $equality2;
                                $bestScore = $this->diff_cleanupSemanticScore($equality1, $edit) + $this->diff_cleanupSemanticScore($edit, $equality2);
                                while (isset($equality2[0]) && $edit[0] === $equality2[0]) {
                                        $equality1 .= $edit[0];
                                        $edit = mb_substr($edit, 1) . $equality2[0];
                                        $equality2 = mb_substr($equality2, 1);
                                        $score = $this->diff_cleanupSemanticScore($equality1, $edit) + $this->diff_cleanupSemanticScore($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 {
                                                $zzz_diffs = array_splice($diffs, $pointer -1, 1);
                                                $pointer--;
                                        }
                                        $diffs[$pointer][1] = $bestEdit;
                                        if ($bestEquality2) {
                                                $diffs[$pointer +1][1] = $bestEquality2;
                                        } else {
                                                $zzz_diffs = array_splice($diffs, $pointer +1, 1);
                                                $pointer--;
                                        }
                                }
                        }
                        $pointer++;
                }
        }

        /**
         * Given two strings, compute a score representing whether the internal
         * boundary falls on logical boundaries.
         * Scores range from 5 (best) to 0 (worst).
         * Closure, makes reference to regex patterns defined above.
         * @param {string} one First string
         * @param {string} two Second string
         * @return {number} The score.
         */
        function diff_cleanupSemanticScore($one, $two) {
                // Define some regex patterns for matching boundaries.
                $punctuation = '/[^a-zA-Z0-9]/';
                $whitespace = '/\s/';
                $linebreak = '/[\r\n]/';
                $blanklineEnd = '/\n\r?\n$/';
                $blanklineStart = '/^\r?\n\r?\n/';

                if (!$one || !$two) {
                        // Edges are the best.
                        return 5;
                }

                // 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.
                $score = 0;
                // One point for non-alphanumeric.
                if (preg_match($punctuation, $one[mb_strlen($one) - 1]) || preg_match($punctuation, $two[0])) {
                        $score++;
                        // Two points for whitespace.
                        if (preg_match($whitespace, $one[mb_strlen($one) - 1] ) || preg_match($whitespace, $two[0])) {
                                $score++;
                                // Three points for line breaks.
                                if (preg_match($linebreak, $one[mb_strlen($one) - 1]) || preg_match($linebreak, $two[0])) {
                                        $score++;
                                        // Four points for blank lines.
                                        if (preg_match($blanklineEnd, $one) || preg_match($blanklineStart, $two)) {
                                                $score++;
                                        }
                                }
                        }
                }
                return $score;
        }

        /**
         * Reduce the number of edits by eliminating operationally trivial equalities.
         * @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
         */
        function diff_cleanupEfficiency(&$diffs) {
                $changes = false;
                $equalities = array (); // Stack of indices where equalities are found.
                $equalitiesLength = 0; // Keeping our own length var is faster in JS.
                $lastequality = ''; // Always equal to equalities[equalitiesLength-1][1]
                $pointer = 0; // Index of current position.
                // Is there an insertion operation before the last equality.
                $pre_ins = false;
                // Is there a deletion operation before the last equality.
                $pre_del = false;
                // Is there an insertion operation after the last equality.
                $post_ins = false;
                // Is there a deletion operation after the last equality.
                $post_del = false;
                while ($pointer < count($diffs)) {
                        if ($diffs[$pointer][0] == DIFF_EQUAL) { // equality found
                                if (mb_strlen($diffs[$pointer][1]) < $this->Diff_EditCost && ($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 = '';
                                }
                                $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 && $post_del) || ((mb_strlen($lastequality) < $this->Diff_EditCost / 2) && ($pre_ins + $pre_del + $post_ins + $post_del) == 3))) {
                                        // Duplicate record
                                        $zzz_diffs = array_splice($diffs, $equalities[$equalitiesLength -1], 0, array(array (
                                                DIFF_DELETE,
                                                $lastequality
                                        )));
                                        // Change second copy to insert.
                                        $diffs[$equalities[$equalitiesLength -1] + 1][0] = DIFF_INSERT;
                                        $equalitiesLength--; // Throw away the equality we just deleted;
                                        $lastequality = '';
                                        if ($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.<Array.<number|string>>} diffs Array of diff tuples.
         */
        function diff_cleanupMerge(&$diffs) {
                array_push($diffs, array ( DIFF_EQUAL, '' )); // Add a dummy entry at the end.
                $pointer = 0;
                $count_delete = 0;
                $count_insert = 0;
                $text_delete = '';
                $text_insert = '';
                $commonlength = null;
                while ($pointer < count($diffs)) {
                        switch ($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 !== 0 || $count_insert !== 0) {
                                                if ($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 - $count_insert -1][1] .= mb_substr($text_insert, 0, $commonlength);
                                                                } else {
                                                                        array_splice($diffs, 0, 0, array(array (
                                                                                DIFF_EQUAL,
                                                                                mb_substr($text_insert, 0, $commonlength)
                                                                        )));
                                                                        $pointer++;
                                                                }
                                                                $text_insert = mb_substr($text_insert, $commonlength);
                                                                $text_delete = mb_substr($text_delete, $commonlength);
                                                        }
                                                        // Factor out any common suffixies.
                                                        $commonlength = $this->diff_commonSuffix($text_insert, $text_delete);
                                                        if ($commonlength !== 0) {
                                                                $diffs[$pointer][1] = mb_substr($text_insert, mb_strlen($text_insert) - $commonlength) . $diffs[$pointer][1];
                                                                $text_insert = mb_substr($text_insert, 0, mb_strlen($text_insert) - $commonlength);
                                                                $text_delete = mb_substr($text_delete, 0, mb_strlen($text_delete) - $commonlength);
                                                        }
                                                }
                                                // Delete the offending records and add the merged ones.
                                                if ($count_delete === 0) {
                                                        array_splice($diffs, $pointer-$count_delete-$count_insert, $count_delete+$count_insert, array(array(
                                                                DIFF_INSERT,
                                                                $text_insert
                                                        )));
                                                } elseif ($count_insert === 0) {
                                                        array_splice($diffs, $pointer-$count_delete-$count_insert, $count_delete+$count_insert, array(array(
                                                                DIFF_DELETE,
                                                                $text_delete
                                                        )));
                                                } else {
                                                        array_splice($diffs, $pointer-$count_delete-$count_insert, $count_delete+$count_insert, array(array(
                                                                DIFF_DELETE,
                                                                $text_delete
                                                        ), array (
                                                                DIFF_INSERT,
                                                                $text_insert
                                                        )));
                                                }
                                                $pointer = $pointer - $count_delete - $count_insert + ($count_delete ? 1 : 0) + ($count_insert ? 1 : 0) + 1;
                                        } elseif ($pointer !== 0 && $diffs[$pointer -1][0] == DIFF_EQUAL) {
                                                // Merge this equality with the previous one.
                                                $diffs[$pointer -1][1] .= $diffs[$pointer][1];
                                                array_splice($diffs, $pointer, 1);
                                        } else {
                                                $pointer++;
                                        }
                                        $count_insert = 0;
                                        $count_delete = 0;
                                        $text_delete = '';
                                        $text_insert = '';
                                        break;
                        }
                }
                if ($diffs[count($diffs) - 1][1] === '') {
                        array_pop($diffs); // 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
                $changes = false;
                $pointer = 1;
                // Intentionally ignore the first and last element (don't need checking).
                while ($pointer < count($diffs) - 1) {
                        if ($diffs[$pointer-1][0] == DIFF_EQUAL && $diffs[$pointer+1][0] == DIFF_EQUAL) {
                                // This is a single edit surrounded by equalities.
                                if ( mb_substr($diffs[$pointer][1], mb_strlen($diffs[$pointer][1]) - mb_strlen($diffs[$pointer -1][1])) == $diffs[$pointer -1][1]) {
                                        // Shift the edit over the previous equality.
                                        $diffs[$pointer][1] = $diffs[$pointer -1][1] . mb_substr($diffs[$pointer][1], 0, mb_strlen($diffs[$pointer][1]) - mb_strlen($diffs[$pointer -1][1]));
                                        $diffs[$pointer +1][1] = $diffs[$pointer -1][1] . $diffs[$pointer +1][1];
                                        array_splice($diffs, $pointer -1, 1);
                                        $changes = true;
                                } elseif (mb_substr($diffs[$pointer][1], 0, mb_strlen($diffs[$pointer +1][1])) == $diffs[$pointer +1][1]) {
                                        // Shift the edit over the next equality.
                                        $diffs[$pointer -1][1] .= $diffs[$pointer +1][1];

                                        $diffs[$pointer][1] = mb_substr($diffs[$pointer][1], mb_strlen($diffs[$pointer +1][1])) . $diffs[$pointer +1][1];
                                        array_splice($diffs, $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.<Array.<number|string>>} diffs Array of diff tuples.
         * @param {number} loc Location within text1.
         * @return {number} Location within text2.
         */
        function diff_xIndex($diffs, $loc) {
                $chars1 = 0;
                $chars2 = 0;
                $last_chars1 = 0;
                $last_chars2 = 0;
                for ($x = 0; $x < count($diffs); $x++) {
                        if ($diffs[$x][0] !== DIFF_INSERT) { // Equality or deletion.
                                $chars1 += mb_strlen($diffs[$x][1]);
                        }
                        if ($diffs[$x][0] !== DIFF_DELETE) { // Equality or insertion.
                                $chars2 += mb_strlen($diffs[$x][1]);
                        }
                        if ($chars1 > $loc) { // Overshot the location.
                                break;
                        }
                        $last_chars1 = $chars1;
                        $last_chars2 = $chars2;
                }
                // Was the location was deleted?
                if (count($diffs) != $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.<Array.<number|string>>} diffs Array of diff tuples.
         * @return {string} HTML representation.
         */
        function diff_prettyHtml($diffs) {
                $html = array ();
                $i = 0;
                for ($x = 0; $x < count($diffs); $x++) {
                        $op = $diffs[$x][0]; // Operation (insert, delete, equal)
                        $data = $diffs[$x][1]; // Text of change.
                        $text = preg_replace(array (
                                '/&/',
                                '/</',
                                '/>/',
                                "/\n/"
                        ), array (
                                '&amp;',
                                '&lt;',
                                '&gt;',
                                '&para;<BR>'
                        ), $data);

                        switch ($op) {
                                case DIFF_INSERT :
                                        $html[$x] = '<INS STYLE="background:#E6FFE6;" TITLE="i=' . $i . '">' . $text . '</INS>';
                                        break;
                                case DIFF_DELETE :
                                        $html[$x] = '<DEL STYLE="background:#FFE6E6;" TITLE="i=' . $i . '">' . $text . '</DEL>';
                                        break;
                                case DIFF_EQUAL :
                                        $html[$x] = '<SPAN TITLE="i=' . $i . '">' . $text . '</SPAN>';
                                        break;
                        }
                        if ($op !== DIFF_DELETE) {
                                $i += mb_strlen($data);
                        }
                }
                return implode('',$html);
        }

        /**
         * Compute and return the source text (all equalities and deletions).
         * @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
         * @return {string} Source text.
         */
        function diff_text1($diffs) {
                $text = array ();
                for ($x = 0; $x < count($diffs); $x++) {
                        if ($diffs[$x][0] !== DIFF_INSERT) {
                                $text[$x] = $diffs[$x][1];
                        }
                }
                return implode('',$text);
        }

        /**
         * Compute and return the destination text (all equalities and insertions).
         * @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
         * @return {string} Destination text.
         */
        function diff_text2($diffs) {
                $text = array ();
                for ($x = 0; $x < count($diffs); $x++) {
                        if ($diffs[$x][0] !== DIFF_DELETE) {
                                $text[$x] = $diffs[$x][1];
                        }
                }
                return implode('',$text);
        }

        /**
         * Compute the Levenshtein distance; the number of inserted, deleted or
         * substituted characters.
         * @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
         * @return {number} Number of changes.
         */
        function diff_levenshtein($diffs) {
                $levenshtein = 0;
                $insertions = 0;
                $deletions = 0;
                for ($x = 0; $x < count($diffs); $x++) {
                        $op = $diffs[$x][0];
                        $data = $diffs[$x][1];
                        switch ($op) {
                                case DIFF_INSERT :
                                        $insertions += mb_strlen($data);
                                        break;
                                case DIFF_DELETE :
                                        $deletions += mb_strlen($data);
                                        break;
                                case DIFF_EQUAL :
                                        // A deletion and an insertion is one substitution.
                                        $levenshtein += max($insertions, $deletions);
                                        $insertions = 0;
                                        $deletions = 0;
                                        break;
                        }
                }
                $levenshtein += max($insertions, $deletions);
                return $levenshtein;
        }

        /**
         * Crush the diff into an encoded string which describes the operations
         * required to transform text1 into text2.
         * E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.
         * Operations are tab-separated.  Inserted text is escaped using %xx notation.
         * @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
         * @return {string} Delta text.
         */
        function diff_toDelta($diffs) {
                $text = array ();
                for ($x = 0; $x < count($diffs); $x++) {
                        switch ($diffs[$x][0]) {
                                case DIFF_INSERT :
                                        $text[$x] = '+' .encodeURI($diffs[$x][1]);
                                        break;
                                case DIFF_DELETE :
                                        $text[$x] = '-' .mb_strlen($diffs[$x][1]);
                                        break;
                                case DIFF_EQUAL :
                                        $text[$x] = '=' .mb_strlen($diffs[$x][1]);
                                        break;
                        }
                }
                return str_replace('%20', ' ', implode("\t", $text));
        }

        /**
         * 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.<Array.<number|string>>} Array of diff tuples.
         * @throws {Error} If invalid input.
         */
        function diff_fromDelta($text1, $delta) {
                $diffs = array ();
                $diffsLength = 0; // Keeping our own length var is faster in JS.
                $pointer = 0; // Cursor in text1
                $tokens = preg_split("/\t/", $delta);

                for ($x = 0; $x < count($tokens); $x++) {
                        // Each token begins with a one character parameter which specifies the
                        // operation of this token (delete, insert, equality).
                        $param = mb_substr($tokens[$x], 1);
                        switch ($tokens[$x][0]) {
                                case '+' :
                                        try {
                                                $diffs[$diffsLength++] = array (
                                                        DIFF_INSERT,
                                                        decodeURI($param)
                                                );
                                        } catch (Exception $ex) {
                                                echo_Exception('Illegal escape in diff_fromDelta: ' . $param);
                                                // Malformed URI sequence.
                                        }
                                        break;
                                case '-' :
                                        // Fall through.
                                case '=' :
                                        $n = (int) $param;
                                        if ($n < 0) {
                                                echo_Exception('Invalid number in diff_fromDelta: ' . $param);
                                        }
                                        $text = mb_substr($text1, $pointer, $n);
                                        $pointer += $n;
                                        if ($tokens[$x][0] == '=') {
                                                $diffs[$diffsLength++] = array (
                                                        DIFF_EQUAL,
                                                        $text
                                                );
                                        } else {
                                                $diffs[$diffsLength++] = array (
                                                        DIFF_DELETE,
                                                        $text
                                                );
                                        }
                                        break;
                                default :
                                        // Blank tokens are ok (from a trailing \t).
                                        // Anything else is an error.
                                        if ($tokens[$x]) {
                                                echo_Exception('Invalid diff operation in diff_fromDelta: ' . $tokens[$x]);
                                        }
                        }
                }
                if ($pointer != mb_strlen($text1)) {
//                      throw new Exception('Delta length (' . $pointer . ') does not equal source text length (' . mb_strlen($text1) . ').');
                        echo_Exception('Delta length (' . $pointer . ') does not equal source text length (' . mb_strlen($text1) . ').');
                }
                return $diffs;
        }

        //  MATCH FUNCTIONS

        /**
         * Locate the best instance of 'pattern' in 'text' near 'loc'.
         * @param {string} text The text to search.
         * @param {string} pattern The pattern to search for.
         * @param {number} loc The location to search around.
         * @return {number} Best match index or -1.
         */
        function match_main($text, $pattern, $loc) {
                $loc = max(0, min($loc, mb_strlen($text)));
                if ($text == $pattern) {
                        // Shortcut (potentially not guaranteed by the algorithm)
                        return 0;
                }
                elseif (!mb_strlen($text)) {
                        // Nothing to match.
                        return -1;
                }
                elseif (mb_substr($text, $loc, mb_strlen($pattern)) == $pattern) {
                        // Perfect match at the perfect spot!  (Includes case of null pattern)
                        return $loc;
                } else {
                        // Do a fuzzy compare.
                        return $this->match_bitap($text, $pattern, $loc);
                }
        }

        /**
         * Locate the best instance of 'pattern' in 'text' near 'loc' using the
         * Bitap algorithm.
         * @param {string} text The text to search.
         * @param {string} pattern The pattern to search for.
         * @param {number} loc The location to search around.
         * @return {number} Best match index or -1.
         * @private
         */
        function match_bitap($text, $pattern, $loc) {
                if (mb_strlen($pattern) > Match_MaxBits) {
                        echo_Exception('Pattern too long for this browser.');
                }

                // Initialise the alphabet.
                $s = $this->match_alphabet($pattern);

                // Highest score beyond which we give up.
                $score_threshold = $this->Match_Threshold;

                // Is there a nearby exact match? (speedup)
                $best_loc = mb_strpos($text, $pattern, $loc);
                if ($best_loc !== false) {
                        $score_threshold = min($this->match_bitapScore(0, $best_loc, $pattern, $loc), $score_threshold);
                }

                // What about in the other direction? (speedup)
                $best_loc = mb_strrpos( $text, $pattern, min($loc + mb_strlen($pattern), mb_strlen($text)) );
                if ($best_loc !== false) {
                        $score_threshold = min($this->match_bitapScore(0, $best_loc, $pattern, $loc), $score_threshold);
                }

                // Initialise the bit arrays.
                $matchmask = 1 << (mb_strlen($pattern) - 1);
                $best_loc = -1;

                $bin_min = null;
                $bin_mid = null;
                $bin_max = mb_strlen($pattern) + mb_strlen($text);
                $last_rd = null;
                for ($d = 0; $d < mb_strlen($pattern); $d++) {
                        // Scan for the best match; each iteration allows for one more error.
                        // Run a binary search to determine how far from 'loc' we can stray at this
                        // error level.
                        $bin_min = 0;
                        $bin_mid = $bin_max;
                        while ($bin_min < $bin_mid) {
                                if ($this->match_bitapScore($d, $loc + $bin_mid, $pattern, $loc) <= $score_threshold) {
                                        $bin_min = $bin_mid;
                                } else {
                                        $bin_max = $bin_mid;
                                }
                                $bin_mid = floor(($bin_max - $bin_min) / 2 + $bin_min);
                        }
                        // Use the result from this iteration as the maximum for the next.
                        $bin_max = $bin_mid;
                        $start = max(1, $loc - $bin_mid +1);
                        $finish = min($loc + $bin_mid, mb_strlen($text)) + mb_strlen($pattern);

                        $rd = Array (
                                $finish +2
                        );
                        $rd[$finish +1] = (1 << $d) - 1;
                        for ($j = $finish; $j >= $start; $j--) {
                                // The alphabet (s) is a sparse hash, so the following line generates
                                // warnings.
@                               $charMatch = $s[ $text[$j -1] ];
                                if ($d === 0) { // First pass: exact match.
                                        $rd[$j] = (($rd[$j +1] << 1) | 1) & $charMatch;
                                } else { // Subsequent passes: fuzzy match.
                                        $rd[$j] = (($rd[$j +1] << 1) | 1) & $charMatch | ((($last_rd[$j +1] | $last_rd[$j]) << 1) | 1) | $last_rd[$j +1];
                                }
                                if ($rd[$j] & $matchmask) {
                                        $score = $this->match_bitapScore($d, $j -1, $pattern, $loc);
                                        // This match will almost certainly be better than any existing match.
                                        // But check anyway.
                                        if ($score <= $score_threshold) {
                                                // Told you so.
                                                $score_threshold = $score;
                                                $best_loc = $j -1;
                                                if ($best_loc > $loc) {
                                                        // When passing loc, don't exceed our current distance from loc.
                                                        $start = max(1, 2 * $loc - $best_loc);
                                                } else {
                                                        // Already passed loc, downhill from here on in.
                                                        break;
                                                }
                                        }
                                }
                        }
                        // No hope for a (better) match at greater error levels.
                        if ($this->match_bitapScore($d +1, $loc, $pattern, $loc) > $score_threshold) {
                                break;
                        }
                        $last_rd = $rd;
                }
                return (int)$best_loc;
        }

        /**
         * Compute and return the score for a match with e errors and x location.
         * Accesses loc and pattern through being a closure.
         * @param {number} e Number of errors in match.
         * @param {number} x Location of match.
         * @return {number} Overall score for match (0.0 = good, 1.0 = bad).
         * @private
         */
        function match_bitapScore($e, $x, $pattern, $loc) {
                $accuracy = $e / mb_strlen($pattern);
                $proximity = abs($loc - $x);
                if (!$this->Match_Distance) {
                        // Dodge divide by zero error.
                        return $proximity ? 1.0 : $accuracy;
                }
                return $accuracy + ($proximity / $this->Match_Distance);
        }

        /**
         * Initialise the alphabet for the Bitap algorithm.
         * @param {string} pattern The text to encode.
         * @return {Object} Hash of character locations.
         * @private
         */
        function match_alphabet($pattern) {
                $s = array ();
                for ($i = 0; $i < mb_strlen($pattern); $i++) {
                        $s[ $pattern[$i] ] = 0;
                }
                for ($i = 0; $i < mb_strlen($pattern); $i++) {
                        $s[ $pattern[$i] ] |= 1 << (mb_strlen($pattern) - $i - 1);
                }
                return $s;
        }

        //  PATCH FUNCTIONS

        /**
         * Increase the context until it is unique,
         * but don't let the pattern expand beyond Match_MaxBits.
         * @param {patch_obj} patch The patch to grow.
         * @param {string} text Source text.
         * @private
         */
        function patch_addContext($patch, $text) {
                $pattern = mb_substr($text, $patch->start2, $patch->length1 );
                $previousPattern = null;
                $padding = 0;
                $i = 0;
                while (
                        (   mb_strlen($pattern) === 0 // Javascript's indexOf/lastIndexOd return 0/strlen respectively if pattern = ''
                         || mb_strpos($text, $pattern) !== mb_strrpos($text, $pattern)
                        )
                        && $pattern !== $previousPattern // avoid infinte loop
                        && mb_strlen($pattern) < Match_MaxBits - $this->Patch_Margin - $this->Patch_Margin ) {
                        $padding += $this->Patch_Margin;
                        $previousPattern = $pattern;
                        $pattern = mb_substr($text, max($patch->start2 - $padding,0), ($patch->start2 + $patch->length1 + $padding) - max($patch->start2 - $padding,0) );
                }
                // Add one chunk for good luck.
                $padding += $this->Patch_Margin;
                // Add the prefix.
                $prefix = mb_substr($text, max($patch->start2 - $padding,0), $patch->start2 - max($patch->start2 - $padding,0) );
                if ($prefix!=='') {
                        array_unshift($patch->diffs, array (
                                DIFF_EQUAL,
                                $prefix
                        ));
                }
                // Add the suffix.
                $suffix = mb_substr($text, $patch->start2 + $patch->length1, ($patch->start2 + $patch->length1 + $padding) - ($patch->start2 + $patch->length1) );
                if ($suffix!=='') {
                        array_push($patch->diffs, array (
                                DIFF_EQUAL,
                                $suffix
                        ));
                }

                // Roll back the start points.
                $patch->start1 -= mb_strlen($prefix);
                $patch->start2 -= mb_strlen($prefix);
                // Extend the lengths.
                $patch->length1 += mb_strlen($prefix) + mb_strlen($suffix);
                $patch->length2 += mb_strlen($prefix) + mb_strlen($suffix);
        }

        /**
         * Compute a list of patches to turn text1 into text2.
         * Use diffs if provided, otherwise compute it ourselves.
         * There are four ways to call this function, depending on what data is
         * available to the caller:
         * Method 1:
         * a = text1, b = text2
         * Method 2:
         * a = diffs
         * Method 3 (optimal):
         * a = text1, b = diffs
         * Method 4 (deprecated, use method 3):
         * a = text1, b = text2, c = diffs
         *
         * @param {string|Array.<Array.<number|string>>} a text1 (methods 1,3,4) or
         * Array of diff tuples for text1 to text2 (method 2).
         * @param {string|Array.<Array.<number|string>>} opt_b text2 (methods 1,4) or
         * Array of diff tuples for text1 to text2 (method 3) or undefined (method 2).
         * @param {string|Array.<Array.<number|string>>} opt_c Array of diff tuples for
         * text1 to text2 (method 4) or undefined (methods 1,2,3).
         * @return {Array.<patch_obj>} Array of patch objects.
         */
        function patch_make($a, $opt_b = null, $opt_c = null ) {
                if (is_string($a) && is_string($opt_b) && $opt_c === null ) {
                        // Method 1: text1, text2
                        // Compute diffs from text1 and text2.
                        $text1 = $a;
                        $diffs = $this->diff_main($text1, $opt_b, true);
                        if ( count($diffs) > 2) {
                                $this->diff_cleanupSemantic($diffs);
                                $this->diff_cleanupEfficiency($diffs);
                        }
                } elseif ( is_array($a) && $opt_b === null && $opt_c === null) {
                        // Method 2: diffs
                        // Compute text1 from diffs.
                        $diffs = $a;
                        $text1 = $this->diff_text1($diffs);
                } elseif ( is_string($a) && is_array($opt_b) && $opt_c === null) {
                        // Method 3: text1, diffs
                        $text1 = $a;
                        $diffs = $opt_b;
                } elseif ( is_string($a) && is_string($opt_b) && is_array($opt_c) ) {
                        // Method 4: text1, text2, diffs
                        // text2 is not used.
                        $text1 = $a;
                        $diffs = $opt_c;
                } else {
                        echo_Exception('Unknown call format to patch_make.');
                }

                if ( count($diffs) === 0) {
                        return array(); // Get rid of the null case.
                }
                $patches = array();
                $patch = new patch_obj();
                $patchDiffLength = 0; // Keeping our own length var is faster in JS.
                $char_count1 = 0; // Number of characters into the text1 string.
                $char_count2 = 0; // Number of characters into the text2 string.
                // Start with text1 (prepatch_text) and apply the diffs until we arrive at
                // text2 (postpatch_text).  We recreate the patches one by one to determine
                // context info.
                $prepatch_text = $text1;
                $postpatch_text = $text1;
                for ($x = 0; $x < count($diffs); $x++) {
                        $diff_type = $diffs[$x][0];
                        $diff_text = $diffs[$x][1];

                        if (!$patchDiffLength && $diff_type !== DIFF_EQUAL) {
                                // A new patch starts here.
                                $patch->start1 = $char_count1;
                                $patch->start2 = $char_count2;
                        }

                        switch ($diff_type) {
                                case DIFF_INSERT :
                                        $patch->diffs[$patchDiffLength++] = $diffs[$x];
                                        $patch->length2 += mb_strlen($diff_text);
                                        $postpatch_text = mb_substr($postpatch_text, 0, $char_count2) . $diff_text . mb_substr($postpatch_text,$char_count2);
                                        break;
                                case DIFF_DELETE :
                                        $patch->length1 += mb_strlen($diff_text);
                                        $patch->diffs[$patchDiffLength++] = $diffs[$x];
                                        $postpatch_text = mb_substr($postpatch_text, 0, $char_count2) . mb_substr($postpatch_text, $char_count2 + mb_strlen($diff_text) );
                                        break;
                                case DIFF_EQUAL :
                                        if ( mb_strlen($diff_text) <= 2 * $this->Patch_Margin && $patchDiffLength && count($diffs) != $x + 1) {
                                                // Small equality inside a patch.
                                                $patch->diffs[$patchDiffLength++] = $diffs[$x];
                                                $patch->length1 += mb_strlen($diff_text);
                                                $patch->length2 += mb_strlen($diff_text);
                                        } elseif ( mb_strlen($diff_text) >= 2 * $this->Patch_Margin ) {
                                                // Time for a new patch.
                                                if ($patchDiffLength) {
                                                        $this->patch_addContext($patch, $prepatch_text);
                                                        array_push($patches,$patch);
                                                        $patch = new patch_obj();
                                                        $patchDiffLength = 0;
                                                        // Unlike Unidiff, our patch lists have a rolling context.
                                                        // http://code.google.com/p/google-diff-match-patch/wiki/Unidiff
                                                        // Update prepatch text & pos to reflect the application of the
                                                        // just completed patch.
                                                        $prepatch_text = $postpatch_text;
                                                        $char_count1 = $char_count2;
                                                }
                                        }
                                        break;
                        }

                        // Update the current character count.
                        if ($diff_type !== DIFF_INSERT) {
                                $char_count1 += mb_strlen($diff_text);
                        }
                        if ($diff_type !== DIFF_DELETE) {
                                $char_count2 += mb_strlen($diff_text);
                        }
                }
                // Pick up the leftover patch if not empty.
                if ($patchDiffLength) {
                        $this->patch_addContext($patch, $prepatch_text);
                        array_push($patches, $patch);
                }

                return $patches;
        }

        /**
         * Given an array of patches, return another array that is identical.
         * @param {Array.<patch_obj>} patches Array of patch objects.
         * @return {Array.<patch_obj>} Array of patch objects.
         */
        function patch_deepCopy($patches) {
                // Making deep copies is hard in JavaScript.
                $patchesCopy = array();
                for ($x = 0; $x < count($patches); $x++) {
                        $patch = $patches[$x];
                        $patchCopy = new patch_obj();
                        for ($y = 0; $y < count($patch->diffs); $y++) {
                                $patchCopy->diffs[$y] = $patch->diffs[$y]; // ?? . slice();
                        }
                        $patchCopy->start1 = $patch->start1;
                        $patchCopy->start2 = $patch->start2;
                        $patchCopy->length1 = $patch->length1;
                        $patchCopy->length2 = $patch->length2;
                        $patchesCopy[$x] = $patchCopy;
                }
                return $patchesCopy;
        }

        /**
         * Merge a set of patches onto the text.  Return a patched text, as well
         * as a list of true/false values indicating which patches were applied.
         * @param {Array.<patch_obj>} patches Array of patch objects.
         * @param {string} text Old text.
         * @return {Array.<string|Array.<boolean>>} Two element Array, containing the
         *      new text and an array of boolean values.
         */
        function patch_apply($patches, $text) {
                if ( count($patches) == 0) {
                        return array($text,array());
                }

                // Deep copy the patches so that no changes are made to originals.
                $patches = $this->patch_deepCopy($patches);

                $nullPadding = $this->patch_addPadding($patches);
                $text = $nullPadding . $text . $nullPadding;

                $this->patch_splitMax($patches);
                // delta keeps track of the offset between the expected and actual location
                // of the previous patch.  If there are patches expected at positions 10 and
                // 20, but the first patch was found at 12, delta is 2 and the second patch
                // has an effective expected position of 22.
                $delta = 0;
                $results = array();
                for ($x = 0; $x < count($patches) ; $x++) {
                        $expected_loc = $patches[$x]->start2 + $delta;
                        $text1 = $this->diff_text1($patches[$x]->diffs);
                        $start_loc = null;
                        $end_loc = -1;
                        if (mb_strlen($text1) > Match_MaxBits) {
                                // patch_splitMax will only provide an oversized pattern in the case of
                                // a monster delete.
                                $start_loc = $this->match_main($text, mb_substr($text1, 0, Match_MaxBits ), $expected_loc);
                                if ($start_loc != -1) {
                                        $end_loc = $this->match_main($text, mb_substr($text1,mb_strlen($text1) - Match_MaxBits), $expected_loc + mb_strlen($text1) - Match_MaxBits);
                                        if ($end_loc == -1 || $start_loc >= $end_loc) {
                                                // Can't find valid trailing context.  Drop this patch.
                                                $start_loc = -1;
                                        }
                                }
                        } else {
                                $start_loc = $this->match_main($text, $text1, $expected_loc);
                        }
                        if ($start_loc == -1) {
                                // No match found.  :(
                                $results[$x] = false;
                                // Subtract the delta for this failed patch from subsequent patches.
                                $delta -= $patches[$x]->length2 - $patches[$x]->length1;
                        } else {
                                // Found a match.  :)
                                $results[$x] = true;
                                $delta = $start_loc - $expected_loc;
                                $text2 = null;
                                if ($end_loc == -1) {
                                        $text2 = mb_substr($text, $start_loc, mb_strlen($text1) );
                                } else {
                                        $text2 = mb_substr($text, $start_loc, $end_loc + Match_MaxBits - $start_loc);
                                }
                                if ($text1 == $text2) {
                                        // Perfect match, just shove the replacement text in.
                                        $text = mb_substr($text, 0, $start_loc) . $this->diff_text2($patches[$x]->diffs) . mb_substr($text,$start_loc + mb_strlen($text1) );
                                } else {
                                        // Imperfect match.  Run a diff to get a framework of equivalent
                                        // indices.
                                        $diffs = $this->diff_main($text1, $text2, false);
                                        if ( mb_strlen($text1) > Match_MaxBits && $this->diff_levenshtein($diffs) / mb_strlen($text1) > $this->Patch_DeleteThreshold) {
                                                // The end points match, but the content is unacceptably bad.
                                                $results[$x] = false;
                                        } else {
                                                $this->diff_cleanupSemanticLossless($diffs);
                                                $index1 = 0;
                                                $index2 = NULL;
                                                for ($y = 0; $y < count($patches[$x]->diffs); $y++) {
                                                        $mod = $patches[$x]->diffs[$y];
                                                        if ($mod[0] !== DIFF_EQUAL) {
                                                                $index2 = $this->diff_xIndex($diffs, $index1);
                                                        }
                                                        if ($mod[0] === DIFF_INSERT) { // Insertion
                                                                $text = mb_substr($text, 0, $start_loc + $index2) . $mod[1] . mb_substr($text, $start_loc + $index2);
                                                        } elseif ($mod[0] === DIFF_DELETE) { // Deletion
                                                                $text = mb_substr($text, 0, $start_loc + $index2) . mb_substr($text,$start_loc + $this->diff_xIndex($diffs, $index1 + mb_strlen($mod[1]) ));
                                                        }
                                                        if ($mod[0] !== DIFF_DELETE) {
                                                                $index1 += mb_strlen($mod[1]);
                                                        }
                                                }
                                        }
                                }
                        }
                }
                // Strip the padding off.
                $text = mb_substr($text, mb_strlen($nullPadding), mb_strlen($text) - 2*mb_strlen($nullPadding) );
                return array($text, $results);
        }

        /**
         * Add some padding on text start and end so that edges can match something.
         * Intended to be called only from within patch_apply.
         * @param {Array.<patch_obj>} patches Array of patch objects.
         * @return {string} The padding string added to each side.
         */
        function patch_addPadding(&$patches){
                $paddingLength = $this->Patch_Margin;
                $nullPadding = '';
                for ($x = 1; $x <= $paddingLength; $x++) {
                        $nullPadding .= mb_chr($x);
                }

                // Bump all the patches forward.
                for ($x = 0; $x < count($patches); $x++) {
                        $patches[$x]->start1 += $paddingLength;
                        $patches[$x]->start2 += $paddingLength;
                }

                // Add some padding on start of first diff.
                $patch = &$patches[0];
                $diffs = &$patch->diffs;
                if (count($diffs) == 0 || $diffs[0][0] != DIFF_EQUAL) {
                        // Add nullPadding equality.
                        array_unshift($diffs, array(DIFF_EQUAL, $nullPadding));
                        $patch->start1 -= $paddingLength; // Should be 0.
                        $patch->start2 -= $paddingLength; // Should be 0.
                        $patch->length1 += $paddingLength;
                        $patch->length2 += $paddingLength;
                } elseif ($paddingLength > mb_strlen($diffs[0][1]) ) {
                        // Grow first equality.
                        $extraLength = $paddingLength - mb_strlen($diffs[0][1]);
                        $diffs[0][1] = mb_substr( $nullPadding , mb_strlen($diffs[0][1]) ) . $diffs[0][1];
                        $patch->start1 -= $extraLength;
                        $patch->start2 -= $extraLength;
                        $patch->length1 += $extraLength;
                        $patch->length2 += $extraLength;
                }

                // Add some padding on end of last diff.
                $patch = &$patches[count($patches) - 1];
                $diffs = &$patch->diffs;
                if ( count($diffs) == 0 || $diffs[ count($diffs) - 1][0] != DIFF_EQUAL) {
                        // Add nullPadding equality.
                        array_push($diffs, array(DIFF_EQUAL, $nullPadding) );
                        $patch->length1 += $paddingLength;
                        $patch->length2 += $paddingLength;
                } elseif ($paddingLength > mb_strlen( $diffs[count($diffs)-1][1] ) ) {
                        // Grow last equality.
                        $extraLength = $paddingLength - mb_strlen( $diffs[count($diffs)-1][1] );
                        $diffs[ count($diffs)-1][1] .= mb_substr($nullPadding,0,$extraLength);
                        $patch->length1 += $extraLength;
                        $patch->length2 += $extraLength;
                }

                return $nullPadding;
        }

        /**
         * Look through the patches and break up any which are longer than the maximum
         * limit of the match algorithm.
         * @param {Array.<patch_obj>} patches Array of patch objects.
         */
        function patch_splitMax(&$patches) {
                for ($x = 0; $x < count($patches); $x++) {
                        if ( $patches[$x]->length1 > Match_MaxBits) {
                                $bigpatch = $patches[$x];
                                // Remove the big old patch.
                                array_splice($patches,$x--,1);
                                $patch_size = Match_MaxBits;
                                $start1 = $bigpatch->start1;
                                $start2 = $bigpatch->start2;
                                $precontext = '';
                                while ( count($bigpatch->diffs) !== 0) {
                                        // Create one of several smaller patches.
                                        $patch = new patch_obj();
                                        $empty = true;
                                        $patch->start1 = $start1 - mb_strlen($precontext);
                                        $patch->start2 = $start2 - mb_strlen($precontext);
                                        if ($precontext !== '') {
                                                $patch->length1 = $patch->length2 = mb_strlen($precontext);
                                                array_push($patch->diffs, array(DIFF_EQUAL, $precontext) );
                                        }
                                        while ( count($bigpatch->diffs) !== 0 && $patch->length1 < $patch_size - $this->Patch_Margin) {
                                                $diff_type = $bigpatch->diffs[0][0];
                                                $diff_text = $bigpatch->diffs[0][1];
                                                if ($diff_type === DIFF_INSERT) {
                                                        // Insertions are harmless.
                                                        $patch->length2 += mb_strlen($diff_text);
                                                        $start2 += mb_strlen($diff_text);
                                                        array_push($patch->diffs, array_shift($bigpatch->diffs) );
                                                        $empty = false;
                                                } else
                                                        if ($diff_type === DIFF_DELETE && count($patch->diffs) == 1 && $patch->diffs[0][0] == DIFF_EQUAL && (mb_strlen($diff_text) > 2 * $patch_size) ) {
                                                                // This is a large deletion.  Let it pass in one chunk.
                                                                $patch->length1 += mb_strlen($diff_text);
                                                                $start1 += mb_strlen($diff_text);
                                                                $empty = false;
                                                                array_push( $patch->diffs, array($diff_type, $diff_text) );
                                                                array_shift($bigpatch->diffs);
                                                        } else {
                                                                // Deletion or equality.  Only take as much as we can stomach.
                                                                $diff_text = mb_substr($diff_text, 0, $patch_size - $patch->length1 - $this->Patch_Margin);
                                                                $patch->length1 += mb_strlen($diff_text);
                                                                $start1 += mb_strlen($diff_text);
                                                                if ($diff_type === DIFF_EQUAL) {
                                                                        $patch->length2 += mb_strlen($diff_text);
                                                                        $start2 += mb_strlen($diff_text);
                                                                } else {
                                                                        $empty = false;
                                                                }
                                                                array_push($patch->diffs, array($diff_type, $diff_text) );
                                                                if ($diff_text == $bigpatch->diffs[0][1]) {
                                                                        array_shift($bigpatch->diffs);
                                                                } else {
                                                                        $bigpatch->diffs[0][1] = mb_substr( $bigpatch->diffs[0][1],mb_strlen($diff_text) );
                                                                }
                                                        }
                                        }
                                        // Compute the head context for the next patch.
                                        $precontext = $this->diff_text2($patch->diffs);
                                        $precontext = mb_substr($precontext, mb_strlen($precontext)-$this->Patch_Margin);
                                        // Append the end context for this patch.
                                        $postcontext = mb_substr( $this->diff_text1($bigpatch->diffs), 0, $this->Patch_Margin );
                                        if ($postcontext !== '') {
                                                $patch->length1 += mb_strlen($postcontext);
                                                $patch->length2 += mb_strlen($postcontext);
                                                if ( count($patch->diffs) !== 0 && $patch->diffs[ count($patch->diffs) - 1][0] === DIFF_EQUAL) {
                                                        $patch->diffs[ count($patch->diffs) - 1][1] .= $postcontext;
                                                } else {
                                                        array_push($patch->diffs, array(DIFF_EQUAL, $postcontext));
                                                }
                                        }
                                        if (!$empty) {
                                                array_splice($patches, ++$x, 0, array($patch));
                                        }
                                }
                        }
                }
        }

        /**
         * Take a list of patches and return a textual representation.
         * @param {Array.<patch_obj>} patches Array of patch objects.
         * @return {string} Text representation of patches.
         */
        function patch_toText($patches) {
                $text = array();
                for ($x = 0; $x < count($patches) ; $x++) {
                        $text[$x] = $patches[$x];
                }
                return implode('',$text);
        }

        /**
         * Parse a textual representation of patches and return a list of patch objects.
         * @param {string} textline Text representation of patches.
         * @return {Array.<patch_obj>} Array of patch objects.
         * @throws {Error} If invalid input.
         */
        function patch_fromText($textline) {
                $patches = array();
                if ($textline === '') {
                        return $patches;
                }
                $text = explode("\n",$textline);
                foreach($text as $i=>$t){ if($t===''){ unset($text[$i]); } }
                $textPointer = 0;
                while ($textPointer < count($text) ) {
                        $m = null;
                        preg_match('/^@@ -(\d+),?(\d*) \+(\d+),?(\d*) @@$/',$text[$textPointer],$m);
                        if (!$m) {
                                echo_Exception('Invalid patch string: ' . $text[$textPointer]);
                        }
                        $patch = new patch_obj();
                        array_push($patches, $patch);
                        @$patch->start1 = (int)$m[1];
                        if (@$m[2] === '') {
                                $patch->start1--;
                                $patch->length1 = 1;
                        } elseif ( @$m[2] == '0') {
                                $patch->length1 = 0;
                        } else {
                                $patch->start1--;
                                @$patch->length1 = (int)$m[2];
                        }

                        @$patch->start2 = (int)$m[3];
                        if (@$m[4] === '') {
                                $patch->start2--;
                                $patch->length2 = 1;
                        } elseif ( @$m[4] == '0') {
                                $patch->length2 = 0;
                        } else {
                                $patch->start2--;
                                @$patch->length2 = (int)$m[4];
                        }
                        $textPointer++;

                        while ($textPointer < count($text) ) {
                                $sign = $text[$textPointer][0];
                                try {
                                        $line = decodeURI( mb_substr($text[$textPointer],1) );
                                } catch (Exception $ex) {
                                        // Malformed URI sequence.
                                        throw new Exception('Illegal escape in patch_fromText: ' . $line);
                                }
                                if ($sign == '-') {
                                        // Deletion.
                                        array_push( $patch->diffs, array(DIFF_DELETE, $line) );
                                } elseif ($sign == '+') {
                                        // Insertion.
                                        array_push($patch->diffs, array(DIFF_INSERT, $line) );
                                } elseif ($sign == ' ') {
                                        // Minor equality.
                                        array_push($patch->diffs, array(DIFF_EQUAL, $line) );
                                } elseif ($sign == '@') {
                                        // Start of next patch.
                                        break;
                                } elseif ($sign === '') {
                                        // Blank line?  Whatever.
                                } else {
                                        // WTF?
                                        echo_Exception('Invalid patch mode "' . $sign . '" in: ' . $line);
                                }
                                $textPointer++;
                        }
                }
                return $patches;
        }
}

/**
 * Class representing one patch operation.
 * @constructor
 */
class patch_obj {
        /** @type {Array.<Array.<number|string>>} */
        public $diffs = array();
        /** @type {number?} */
        public $start1 = null;
        /** @type {number?} */
        public $start2 = null;
        /** @type {number} */
        public $length1 = 0;
        /** @type {number} */
        public $length2 = 0;

        /**
         * Emmulate GNU diff's format.
         * Header: @@ -382,8 +481,9 @@
         * Indicies are printed as 1-based, not 0-based.
         * @return {string} The GNU diff string.
         */
        function toString() {
                if ($this->length1 === 0) {
                        $coords1 = $this->start1 . ',0';
                } elseif ($this->length1 == 1) {
                        $coords1 = $this->start1 + 1;
                } else {
                        $coords1 = ($this->start1 + 1) . ',' . $this->length1;
                }
                if ($this->length2 === 0) {
                        $coords2 = $this->start2 . ',0';
                } elseif ($this->length2 == 1) {
                        $coords2 = $this->start2 + 1;
                } else {
                        $coords2 = ($this->start2 + 1) . ',' . $this->length2;
                }
                $text = array ( '@@ -' . $coords1 . ' +' . $coords2 . " @@\n" );

                // Escape the body of the patch with %xx notation.
                for ($x = 0; $x < count($this->diffs); $x++) {
                        switch ($this->diffs[$x][0]) {
                                case DIFF_INSERT :
                                        $op = '+';
                                        break;
                                case DIFF_DELETE :
                                        $op = '-';
                                        break;
                                case DIFF_EQUAL :
                                        $op = ' ';
                                        break;
                        }
                        $text[$x +1] = $op . encodeURI($this->diffs[$x][1]) . "\n";
                }
                return str_replace('%20', ' ', implode('',$text));
        }
        function __toString(){
                return $this->toString();
        }
}

define('DIFF_DELETE', -1);
define('DIFF_INSERT', 1);
define('DIFF_EQUAL', 0);

define('Match_MaxBits', PHP_INT_SIZE * 8);


function charCodeAt($str, $pos) {
        return mb_ord(mb_substr($str, $pos, 1));
}
function mb_ord($v) {
        $k = mb_convert_encoding($v, 'UCS-2LE', 'UTF-8'); 
        $k1 = ord(substr($k, 0, 1)); 
        $k2 = ord(substr($k, 1, 1)); 
        return $k2 * 256 + $k1; 
}
function mb_chr($num){
        return mb_convert_encoding('&#'.intval($num).';', 'UTF-8', 'HTML-ENTITIES');
}

/**
 * as in javascript encodeURI() following the MDN description
 *
 * @link https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/encodeURI
 * @param $url
 * @return string
 */
function encodeURI($url) {
    return strtr(rawurlencode($url), array (
        '%3B' => ';', '%2C' => ',', '%2F' => '/', '%3F' => '?', '%3A' => ':', '%40' => '@', '%26' => '&', '%3D' => '=',
        '%2B' => '+', '%24' => '$', '%21' => '!', '%2A' => '*', '%27' => '\'', '%28' => '(', '%29' => ')', '%23' => '#',
    ));
}

function decodeURI($encoded) {
        static $dontDecode;
        if (!$dontDecode) {
                $table = array (
                        '%3B' => ';', '%2C' => ',', '%2F' => '/', '%3F' => '?', '%3A' => ':', '%40' => '@', '%26' => '&', '%3D' => '=',
                        '%2B' => '+', '%24' => '$', '%21' => '!', '%2A' => '*', '%27' => '\'', '%28' => '(', '%29' => ')', '%23' => '#',
                );
                $dontDecode = array();
                foreach ($table as $k => $v) {
                        $dontDecode[$k] = encodeURI($k);
                }
        }
        return rawurldecode(strtr($encoded, $dontDecode));
}

function echo_Exception($str){
        global $lastException;
        $lastException = $str;
        echo $str;
}
//mb_internal_encoding("UTF-8");

?>