Text_Diff_Engine_string::parseContextDiff

    function parseContextDiff(&$diff)
    {
        $edits = array();
        $i = $max_i = $j = $max_j = 0;
        $end = count($diff) - 1;
        while ($i < $end && $j < $end) {
            while ($i >= $max_i && $j >= $max_j) {
                // Find the boundaries of the diff output of the two files
                for ($i = $j;
                     $i < $end && substr($diff[$i], 0, 3) == '***';
                     $i++);
                for ($max_i = $i;
                     $max_i < $end && substr($diff[$max_i], 0, 3) != '---';
                     $max_i++);
                for ($j = $max_i;
                     $j < $end && substr($diff[$j], 0, 3) == '---';
                     $j++);
                for ($max_j = $j;
                     $max_j < $end && substr($diff[$max_j], 0, 3) != '***';
                     $max_j++);
            }

            // find what hasn't been changed
            $array = array();
            while ($i < $max_i &&
                   $j < $max_j &&
                   strcmp($diff[$i], $diff[$j]) == 0) {
                $array[] = substr($diff[$i], 2);
                $i++;
                $j++;
            }

            while ($i < $max_i && ($max_j-$j) <= 1) {
                if ($diff[$i] != '' && substr($diff[$i], 0, 1) != ' ') {
                    break;
                }
                $array[] = substr($diff[$i++], 2);
            }

            while ($j < $max_j && ($max_i-$i) <= 1) {
                if ($diff[$j] != '' && substr($diff[$j], 0, 1) != ' ') {
                    break;
                }
                $array[] = substr($diff[$j++], 2);
            }
            if (count($array) > 0) {
                $edits[] = new Text_Diff_Op_copy($array);
            }

            if ($i < $max_i) {
                $diff1 = array();
                switch (substr($diff[$i], 0, 1)) {
                case '!':
                    $diff2 = array();
                    do {
                        $diff1[] = substr($diff[$i], 2);
                        if ($j < $max_j && substr($diff[$j], 0, 1) == '!') {
                            $diff2[] = substr($diff[$j++], 2);
                        }
                    } while (++$i < $max_i && substr($diff[$i], 0, 1) == '!');
                    $edits[] = new Text_Diff_Op_change($diff1, $diff2);
                    break;

                case '+':
                    do {
                        $diff1[] = substr($diff[$i], 2);
                    } while (++$i < $max_i && substr($diff[$i], 0, 1) == '+');
                    $edits[] = new Text_Diff_Op_add($diff1);
                    break;

                case '-':
                    do {
                        $diff1[] = substr($diff[$i], 2);
                    } while (++$i < $max_i && substr($diff[$i], 0, 1) == '-');
                    $edits[] = new Text_Diff_Op_delete($diff1);
                    break;
                }
            }

            if ($j < $max_j) {
                $diff2 = array();
                switch (substr($diff[$j], 0, 1)) {
                case '+':
                    do {
                        $diff2[] = substr($diff[$j++], 2);
                    } while ($j < $max_j && substr($diff[$j], 0, 1) == '+');
                    $edits[] = new Text_Diff_Op_add($diff2);
                    break;

                case '-':
                    do {
                        $diff2[] = substr($diff[$j++], 2);
                    } while ($j < $max_j && substr($diff[$j], 0, 1) == '-');
                    $edits[] = new Text_Diff_Op_delete($diff2);
                    break;
                }
            }
        }

        return $edits;
    }