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+<?php
+
+/*
+
+class.Diff.php
+
+A class containing a diff implementation
+
+Created by Stephen Morley - http://stephenmorley.org/ - and released under the
+terms of the CC0 1.0 Universal legal code:
+
+http://creativecommons.org/publicdomain/zero/1.0/legalcode
+
+*/
+
+// A class containing functions for computing diffs and formatting the output.
+class Diff{
+
+ // define the constants
+ const UNMODIFIED = 0;
+ const DELETED = 1;
+ const INSERTED = 2;
+
+ /* Returns the diff for two strings. The return value is an array, each of
+ * whose values is an array containing two values: a line (or character, if
+ * $compareCharacters is true), and one of the constants DIFF::UNMODIFIED (the
+ * line or character is in both strings), DIFF::DELETED (the line or character
+ * is only in the first string), and DIFF::INSERTED (the line or character is
+ * only in the second string). The parameters are:
+ *
+ * $string1 - the first string
+ * $string2 - the second string
+ * $compareCharacters - true to compare characters, and false to compare
+ * lines; this optional parameter defaults to false
+ */
+ public static function compare(
+ $string1, $string2, $compareCharacters = false){
+
+ // initialise the sequences and comparison start and end positions
+ $start = 0;
+ if ($compareCharacters){
+ $sequence1 = $string1;
+ $sequence2 = $string2;
+ $end1 = strlen($string1) - 1;
+ $end2 = strlen($string2) - 1;
+ }else{
+ $sequence1 = preg_split('/\R/', $string1);
+ $sequence2 = preg_split('/\R/', $string2);
+ $end1 = count($sequence1) - 1;
+ $end2 = count($sequence2) - 1;
+ }
+
+ // skip any common prefix
+ while ($start <= $end1 && $start <= $end2
+ && $sequence1[$start] == $sequence2[$start]){
+ $start ++;
+ }
+
+ // skip any common suffix
+ while ($end1 >= $start && $end2 >= $start
+ && $sequence1[$end1] == $sequence2[$end2]){
+ $end1 --;
+ $end2 --;
+ }
+
+ // compute the table of longest common subsequence lengths
+ $table = self::computeTable($sequence1, $sequence2, $start, $end1, $end2);
+
+ // generate the partial diff
+ $partialDiff =
+ self::generatePartialDiff($table, $sequence1, $sequence2, $start);
+
+ // generate the full diff
+ $diff = array();
+ for ($index = 0; $index < $start; $index ++){
+ $diff[] = array($sequence1[$index], self::UNMODIFIED);
+ }
+ while (count($partialDiff) > 0) $diff[] = array_pop($partialDiff);
+ for ($index = $end1 + 1;
+ $index < ($compareCharacters ? strlen($sequence1) : count($sequence1));
+ $index ++){
+ $diff[] = array($sequence1[$index], self::UNMODIFIED);
+ }
+
+ // return the diff
+ return $diff;
+
+ }
+
+ /* Returns the diff for two files. The parameters are:
+ *
+ * $file1 - the path to the first file
+ * $file2 - the path to the second file
+ * $compareCharacters - true to compare characters, and false to compare
+ * lines; this optional parameter defaults to false
+ */
+ public static function compareFiles(
+ $file1, $file2, $compareCharacters = false){
+
+ // return the diff of the files
+ return self::compare(
+ file_get_contents($file1),
+ file_get_contents($file2),
+ $compareCharacters);
+
+ }
+
+ /* Returns the table of longest common subsequence lengths for the specified
+ * sequences. The parameters are:
+ *
+ * $sequence1 - the first sequence
+ * $sequence2 - the second sequence
+ * $start - the starting index
+ * $end1 - the ending index for the first sequence
+ * $end2 - the ending index for the second sequence
+ */
+ private static function computeTable(
+ $sequence1, $sequence2, $start, $end1, $end2){
+
+ // determine the lengths to be compared
+ $length1 = $end1 - $start + 1;
+ $length2 = $end2 - $start + 1;
+
+ // initialise the table
+ $table = array(array_fill(0, $length2 + 1, 0));
+
+ // loop over the rows
+ for ($index1 = 1; $index1 <= $length1; $index1 ++){
+
+ // create the new row
+ $table[$index1] = array(0);
+
+ // loop over the columns
+ for ($index2 = 1; $index2 <= $length2; $index2 ++){
+
+ // store the longest common subsequence length
+ if ($sequence1[$index1 + $start - 1]
+ == $sequence2[$index2 + $start - 1]){
+ $table[$index1][$index2] = $table[$index1 - 1][$index2 - 1] + 1;
+ }else{
+ $table[$index1][$index2] =
+ max($table[$index1 - 1][$index2], $table[$index1][$index2 - 1]);
+ }
+
+ }
+ }
+
+ // return the table
+ return $table;
+
+ }
+
+ /* Returns the partial diff for the specificed sequences, in reverse order.
+ * The parameters are:
+ *
+ * $table - the table returned by the computeTable function
+ * $sequence1 - the first sequence
+ * $sequence2 - the second sequence
+ * $start - the starting index
+ */
+ private static function generatePartialDiff(
+ $table, $sequence1, $sequence2, $start){
+
+ // initialise the diff
+ $diff = array();
+
+ // initialise the indices
+ $index1 = count($table) - 1;
+ $index2 = count($table[0]) - 1;
+
+ // loop until there are no items remaining in either sequence
+ while ($index1 > 0 || $index2 > 0){
+
+ // check what has happened to the items at these indices
+ if ($index1 > 0 && $index2 > 0
+ && $sequence1[$index1 + $start - 1]
+ == $sequence2[$index2 + $start - 1]){
+
+ // update the diff and the indices
+ $diff[] = array($sequence1[$index1 + $start - 1], self::UNMODIFIED);
+ $index1 --;
+ $index2 --;
+
+ }elseif ($index2 > 0
+ && $table[$index1][$index2] == $table[$index1][$index2 - 1]){
+
+ // update the diff and the indices
+ $diff[] = array($sequence2[$index2 + $start - 1], self::INSERTED);
+ $index2 --;
+
+ }else{
+
+ // update the diff and the indices
+ $diff[] = array($sequence1[$index1 + $start - 1], self::DELETED);
+ $index1 --;
+
+ }
+
+ }
+
+ // return the diff
+ return $diff;
+
+ }
+
+ /* Returns a diff as a string, where unmodified lines are prefixed by ' ',
+ * deletions are prefixed by '- ', and insertions are prefixed by '+ '. The
+ * parameters are:
+ *
+ * $diff - the diff array
+ * $separator - the separator between lines; this optional parameter defaults
+ * to "\n"
+ */
+ public static function toString($diff, $separator = "\n"){
+
+ // initialise the string
+ $string = '';
+
+ // loop over the lines in the diff
+ foreach ($diff as $line){
+
+ // extend the string with the line
+ switch ($line[1]){
+ case self::UNMODIFIED : $string .= ' ' . $line[0];break;
+ case self::DELETED : $string .= '- ' . $line[0];break;
+ case self::INSERTED : $string .= '+ ' . $line[0];break;
+ }
+
+ // extend the string with the separator
+ $string .= $separator;
+
+ }
+
+ // return the string
+ return $string;
+
+ }
+
+ /* Returns a diff as an HTML string, where unmodified lines are contained
+ * within 'span' elements, deletions are contained within 'del' elements, and
+ * insertions are contained within 'ins' elements. The parameters are:
+ *
+ * $diff - the diff array
+ * $separator - the separator between lines; this optional parameter defaults
+ * to '<br>'
+ */
+ public static function toHTML($diff, $separator = '<br>'){
+
+ // initialise the HTML
+ $html = '';
+
+ // loop over the lines in the diff
+ foreach ($diff as $line){
+
+ // extend the HTML with the line
+ switch ($line[1]){
+ case self::UNMODIFIED : $element = 'span'; break;
+ case self::DELETED : $element = 'del'; break;
+ case self::INSERTED : $element = 'ins'; break;
+ }
+ $html .=
+ '<' . $element . '>'
+ . htmlspecialchars($line[0])
+ . '</' . $element . '>';
+
+ // extend the HTML with the separator
+ $html .= $separator;
+
+ }
+
+ // return the HTML
+ return $html;
+
+ }
+
+ /* Returns a diff as an HTML table. The parameters are:
+ *
+ * $diff - the diff array
+ * $indentation - indentation to add to every line of the generated HTML; this
+ * optional parameter defaults to ''
+ * $separator - the separator between lines; this optional parameter
+ * defaults to '<br>'
+ */
+ public static function toTable($diff, $indentation = '', $separator = '<br>'){
+
+ // initialise the HTML
+ $html = $indentation . "<table class=\"diff\">\n";
+
+ // loop over the lines in the diff
+ $index = 0;
+ while ($index < count($diff)){
+
+ // determine the line type
+ switch ($diff[$index][1]){
+
+ // display the content on the left and right
+ case self::UNMODIFIED:
+ $leftCell =
+ self::getCellContent(
+ $diff, $indentation, $separator, $index, self::UNMODIFIED);
+ $rightCell = $leftCell;
+ break;
+
+ // display the deleted on the left and inserted content on the right
+ case self::DELETED:
+ $leftCell =
+ self::getCellContent(
+ $diff, $indentation, $separator, $index, self::DELETED);
+ $rightCell =
+ self::getCellContent(
+ $diff, $indentation, $separator, $index, self::INSERTED);
+ break;
+
+ // display the inserted content on the right
+ case self::INSERTED:
+ $leftCell = '';
+ $rightCell =
+ self::getCellContent(
+ $diff, $indentation, $separator, $index, self::INSERTED);
+ break;
+
+ }
+
+ // extend the HTML with the new row
+ $html .=
+ $indentation
+ . " <tr>\n"
+ . $indentation
+ . ' <td class="diff'
+ . ($leftCell == $rightCell
+ ? 'Unmodified'
+ : ($leftCell == '' ? 'Blank' : 'Deleted'))
+ . '">'
+ . $leftCell
+ . "</td>\n"
+ . $indentation
+ . ' <td class="diff'
+ . ($leftCell == $rightCell
+ ? 'Unmodified'
+ : ($rightCell == '' ? 'Blank' : 'Inserted'))
+ . '">'
+ . $rightCell
+ . "</td>\n"
+ . $indentation
+ . " </tr>\n";
+
+ }
+
+ // return the HTML
+ return $html . $indentation . "</table>\n";
+
+ }
+
+ /* Returns the content of the cell, for use in the toTable function. The
+ * parameters are:
+ *
+ * $diff - the diff array
+ * $indentation - indentation to add to every line of the generated HTML
+ * $separator - the separator between lines
+ * $index - the current index, passes by reference
+ * $type - the type of line
+ */
+ private static function getCellContent(
+ $diff, $indentation, $separator, &$index, $type){
+
+ // initialise the HTML
+ $html = '';
+
+ // loop over the matching lines, adding them to the HTML
+ while ($index < count($diff) && $diff[$index][1] == $type){
+ $html .=
+ '<span>'
+ . htmlspecialchars($diff[$index][0])
+ . '</span>'
+ . $separator;
+ $index ++;
+ }
+
+ // return the HTML
+ return $html;
+
+ }
+
+}
+
+?>