==== Wikka Mod 013 ====
Type: Feature Addition
----
===Credit:===
**[[JsnX | Jason Tourtelotte]]**
----

Added "Page History" link in footer.php to make this addition easily accessible.

----

handlers/page/history.php

%%(php)
<div class="page">
<?php
if ($this->HasAccess("read")) {
// load revisions for this page
if ($pages = $this->LoadRevisions($this->tag))
{
if ($user = $this->GetUser())
{
$max = $user["revisioncount"];
}
else
{
$max = 20;
}

$c = 0;
foreach ($pages as $page)
{
$c++;
if (($c <= $max) || !$max)
{

$pageB = $this->LoadPageById($page["id"]);
$bodyB = explode("\n", $pageB["body"]);

if ($pageA)
{
// show by default. We'll do security checks next.
$allowed = 1;

// check if the loaded pages are actually revisions of the current page! (fixes #0000046)
//print_r($pageA); print_r($this->page); exit;
if (($pageA['tag'] != $this->page['tag']) || ($pageB['tag'] != $this->page['tag'])) {
$allowed = 0;
}
// show if we're still allowed to see the diff
if ($allowed) {

// prepare bodies
$bodyA = explode("\n", $pageA["body"]);
// $bodyB = explode("\n", $pageB["body"]);

$added = array_diff($bodyA, $bodyB);
$deleted = array_diff($bodyB, $bodyA);

if ($c == 2) {
$output .= "<strong>Most recent edit on <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span></strong><br />\n";
}
else {
$output .= "<strong>Edited on <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span><br />\n";
}

if ($added)
{
// remove blank lines
$output .= "<br />\n<strong>Additions:</strong><br />\n";
$output .= "<div class=\"additions\">".$this->Format(implode("\n", $added))."</div>";
}

if ($deleted)
{
$output .= "<br />\n<strong>Deletions:</strong><br />\n";
$output .= "<div class=\"deletions\">".$this->Format(implode("\n", $deleted))."</div>";
}

if (!$added && !$deleted)
{
$output .= "<br />\nNo differences.";
}
$output .= "<br />\n<HR><br />\n";
}
}
else {
// $output .= "<DIV class=\"revisioninfo\">Current page:</div>".$this->Format($pageB["body"])."<br />\n<HR><br />\n";
}
$pageA = $this->LoadPageById($page["id"]);
$EditedByUser = $this->Format($page["user"]);
}
}
$output .= "<strong>Oldest known version of this page was edited on <a href=\"".$this->href("", "", "time=".urlencode($pageB["time"]))."\">".$pageB["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span></strong><br />\n";
$output .= "<DIV class=\"revisioninfo\">Page view:</div>".$this->Format(implode("\n", $bodyB));
}
print($output);

} else {
print("<em>You aren't allowed to read this page.</em>");
}
?>
</div>
%%


handlers/page/history2.php

%%(php)
<div class="page">
<?php
if ($this->HasAccess("read")) {
// load revisions for this page
if ($pages = $this->LoadRevisions($this->tag))
{
if ($user = $this->GetUser())
{
$max = $user["revisioncount"];
}
else
{
$max = 20;
}

$c = 0;
foreach ($pages as $page)
{
$c++;
if (($c <= $max) || !$max)
{

$pageA = $this->LoadPageById($page["id"]);
$bodyB = explode("\n", $pageB["body"]);

if ($pageB)
{
// show by default. We'll do security checks next.
$allowed = 1;

// check if the loaded pages are actually revisions of the current page! (fixes #0000046)
//print_r($pageA); print_r($this->page); exit;
if (($pageA['tag'] != $this->page['tag']) || ($pageB['tag'] != $this->page['tag'])) {
$allowed = 0;
}
// show if we're still allowed to see the diff
if ($allowed) {


// extract text from bodies
$textA = $pageA["body"];
$textB = $pageB["body"];

$sideA = new Side($textA);
$sideB = new Side($textB);

$bodyA='';
$sideA->split_file_into_words($bodyA);

$bodyB='';
$sideB->split_file_into_words($bodyB);

// diff on these two file
$diff = new Diff(split("\n",$bodyA),split("\n",$bodyB));

// format output
$fmt = new DiffFormatter();

$sideO = new Side($fmt->format($diff));

$resync_left=0;
$resync_right=0;

$count_total_right=$sideB->getposition() ;

$sideA->init();
$sideB->init();

$output='';


if ($c == 2) {
echo "<strong>Most recent edit on <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span></strong><br /><br />\n";
}
else {
// $output .= "<strong>Comparing <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> to <a href=\"".$this->href("", "", "time=".urlencode($pageB["time"]))."\">".$pageB["time"]."</a></strong><br />\n";
echo "<strong>Edited on <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span><br /><br />\n";
}


while (1) {

$sideO->skip_line();
if ($sideO->isend()) {
break;
}

if ($sideO->decode_directive_line()) {
$argument=$sideO->getargument();
$letter=$sideO->getdirective();
switch ($letter) {
case 'a':
$resync_left = $argument[0];
$resync_right = $argument[2] - 1;
break;

case 'd':
$resync_left = $argument[0] - 1;
$resync_right = $argument[2];
break;

case 'c':
$resync_left = $argument[0] - 1;
$resync_right = $argument[2] - 1;
break;

}

$sideA->skip_until_ordinal($resync_left);
$sideB->copy_until_ordinal($resync_right,$output);

// deleted word

if (($letter=='d') || ($letter=='c')) {
$sideA->copy_whitespace($output);
$output .="++";
$sideA->copy_word($output);
$sideA->copy_until_ordinal($argument[1],$output);
$output .="++";
}

// inserted word
if ($letter == 'a' || $letter == 'c') {
$sideB->copy_whitespace($output);
$output .="+££";
$sideB->copy_word($output);
$sideB->copy_until_ordinal($argument[3],$output);
$output .="+££";
}

}

}

$sideB->copy_until_ordinal($count_total_right,$output);
$sideB->copy_whitespace($output);
$out=$this->Format($output);
echo $out;
echo "<BR><BR>";
echo "<HR>";


}
}
else {
// $output .= "<DIV class=\"revisioninfo\">Current page:</div>".$this->Format($pageB["body"])."<br />\n<HR><br />\n";
}
$pageB = $this->LoadPageById($page["id"]);
$EditedByUser = $this->Format($page["user"]);
}
}
$bodyE = explode("\n", $pageB["body"]);
$end_output .= "<strong>Oldest known version of this page was edited on <a href=\"".$this->href("", "", "time=".urlencode($pageB["time"]))."\">".$pageB["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span></strong><br /><br />\n";
$end_output .= $this->Format(implode("\n", $bodyE));
}
print($end_output);

} else {
print("<em>You aren't allowed to read this page.</em>");
}


// Side : a string for wdiff

class Side {
var $position;
var $cursor;
var $content;
var $character;
var $directive;
var $argument;
var $length;

function Side($content) {
$this->content=$content;
$this->position=0;
$this->cursor=0;
$this->directive='';
$this->argument=array();
$this->length=strlen($this->content);
$this->character=substr($this->content,0,1);

}

function getposition() {
return $this->position;
}

function getcharacter() {
return $this->character;
}

function getdirective() {
return $this->directive;
}

function getargument() {
return $this->argument;
}

function nextchar() {
$this->cursor++;
$this->character=substr($this->content,$this->cursor,1);
}

function copy_until_ordinal($ordinal,&$out) {
while ($this->position < $ordinal) {
$this->copy_whitespace($out);
$this->copy_word($out);
}
}

function skip_until_ordinal($ordinal) {
while ($this->position < $ordinal) {
$this->skip_whitespace();
$this->skip_word();
}
}

function split_file_into_words (&$out) {
while (!$this->isend()) {
$this->skip_whitespace();
if ($this->isend()) {
break;
}
$this->copy_word($out);
$out .="\n";
}
}

function init() {
$this->position=0;
$this->cursor=0;
$this->directive='';
$this->argument=array();
$this->character=substr($this->content,0,1);
}

function isspace($char) {
if (ereg('[[:space:]]',$char)) {
return true;
}
else {
return false;
}
}

function isdigit($char) {
if (ereg('[[:digit:]]',$char)) {
return true;
}
else {
return false;
}
}

function isend() {
if (($this->cursor)>=($this->length)) {
return true;
}
else {
return false;
}
}



function copy_whitespace(&$out) {
while (!$this->isend() && $this->isspace($this->character)) {
$out .=$this->character;
$this->nextchar();
}
}

function skip_whitespace() {
while (!$this->isend() && $this->isspace($this->character)) {
$this->nextchar();
}
}

function skip_line() {
while (!$this->isend() && !$this->isdigit($this->character)) {
while (!$this->isend() && $this->character!="\n")
$this->nextchar();
if($this->character=="\n")
$this->nextchar();
}
}



function copy_word(&$out) {
while (!$this->isend() && !($this->isspace($this->character))) {
$out.=$this->character;
$this->nextchar();
}
$this->position++;
}

function skip_word() {

while (!$this->isend() && !($this->isspace($this->character))) {
$this->nextchar();
}
$this->position++;
}


function decode_directive_line() {

$value=0;
$state=0;
$error=0;

while (!$error && $state < 4) {
if ($this->isdigit($this->character)) {
$value = 0;
while($this->isdigit($this->character)) {
$value = 10 * $value + $this->character - '0';
$this->nextchar();
}
}
else if ($state != 1 && $state != 3)
$error = 1;

/* Assign the proper value. */

$this->argument[$state] = $value;

/* Skip the following character. */

switch ($state) {
case 0:
case 2:
if ($this->character == ',')
$this->nextchar();
break;

case 1:
if ($this->character == 'a' || $this->character == 'd' || $this->character == 'c') {
$this->directive = $this->character;
$this->nextchar();
}
else
$error = 1;
break;

case 3:
if ($this->character != "\n")
$error = 1;
break;
}
$state++;
}

/* Complete reading of the line and return success value. */

while ((!$this->isend()) && ($this->character != "\n")) {
$this->nextchar();
}
if ($this->character == "\n")
$this->nextchar();

return !$error;
}



}

// difflib
//
// A PHP diff engine for phpwiki.
//
// Copyright (C) 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
// You may copy this code freely under the conditions of the GPL.
//


// PHP3 does not have assert()
define('USE_ASSERTS', function_exists('assert'));

class _DiffOp {
var $type;
var $orig;
var $final;


function norig() {
return $this->orig ? sizeof($this->orig) : 0;
}

function nfinal() {
return $this->final ? sizeof($this->final) : 0;
}
}

class _DiffOp_Copy extends _DiffOp {
var $type = 'copy';

function _DiffOp_Copy ($orig, $final = false) {
if (!is_array($final))
$final = $orig;
$this->orig = $orig;
$this->final = $final;
}

}

class _DiffOp_Delete extends _DiffOp {
var $type = 'delete';

function _DiffOp_Delete ($lines) {
$this->orig = $lines;
$this->final = false;
}

}

class _DiffOp_Add extends _DiffOp {
var $type = 'add';

function _DiffOp_Add ($lines) {
$this->final = $lines;
$this->orig = false;
}

}

class _DiffOp_Change extends _DiffOp {
var $type = 'change';

function _DiffOp_Change ($orig, $final) {
$this->orig = $orig;
$this->final = $final;
}

}


/**
* Class used internally by Diff to actually compute the diffs.
*
* The algorithm used here is mostly lifted from the perl module
* Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
* http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
*
* More ideas are taken from:
* http://www.ics.uci.edu/~eppstein/161/960229.html
*
* Some ideas are (and a bit of code) are from from analyze.c, from GNU
* diffutils-2.7, which can be found at:
* ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
*
* Finally, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
* are my own.
*
* @author Geoffrey T. Dairiki
* @access private
*/
class _DiffEngine
{
function diff ($from_lines, $to_lines) {
$n_from = sizeof($from_lines);
$n_to = sizeof($to_lines);

$this->xchanged = $this->ychanged = array();
$this->xv = $this->yv = array();
$this->xind = $this->yind = array();
unset($this->seq);
unset($this->in_seq);
unset($this->lcs);

// Skip leading common lines.
for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
if ($from_lines[$skip] != $to_lines[$skip])
break;
$this->xchanged[$skip] = $this->ychanged[$skip] = false;
}
// Skip trailing common lines.
$xi = $n_from; $yi = $n_to;
for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
if ($from_lines[$xi] != $to_lines[$yi])
break;
$this->xchanged[$xi] = $this->ychanged[$yi] = false;
}

// Ignore lines which do not exist in both files.
for ($xi = $skip; $xi < $n_from - $endskip; $xi++)
$xhash[$from_lines[$xi]] = 1;
for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
$line = $to_lines[$yi];
if ( ($this->ychanged[$yi] = empty($xhash[$line])) )
continue;
$yhash[$line] = 1;
$this->yv[] = $line;
$this->yind[] = $yi;
}
for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
$line = $from_lines[$xi];
if ( ($this->xchanged[$xi] = empty($yhash[$line])) )
continue;
$this->xv[] = $line;
$this->xind[] = $xi;
}

// Find the LCS.
$this->_compareseq(0, sizeof($this->xv), 0, sizeof($this->yv));

// Merge edits when possible
$this->_shift_boundaries($from_lines, $this->xchanged, $this->ychanged);
$this->_shift_boundaries($to_lines, $this->ychanged, $this->xchanged);

// Compute the edit operations.
$edits = array();
$xi = $yi = 0;
while ($xi < $n_from || $yi < $n_to) {
USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
USE_ASSERTS && assert($xi < $n_from || $this->ychanged[$yi]);

// Skip matching "snake".
$copy = array();
while ( $xi < $n_from && $yi < $n_to
&& !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
$copy[] = $from_lines[$xi++];
++$yi;
}
if ($copy)
$edits[] = new _DiffOp_Copy($copy);

// Find deletes & adds.
$delete = array();
while ($xi < $n_from && $this->xchanged[$xi])
$delete[] = $from_lines[$xi++];

$add = array();
while ($yi < $n_to && $this->ychanged[$yi])
$add[] = $to_lines[$yi++];

if ($delete && $add)
$edits[] = new _DiffOp_Change($delete, $add);
elseif ($delete)
$edits[] = new _DiffOp_Delete($delete);
elseif ($add)
$edits[] = new _DiffOp_Add($add);
}
return $edits;
}


/* Divide the Largest Common Subsequence (LCS) of the sequences
* [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
* sized segments.
*
* Returns (LCS, PTS). LCS is the length of the LCS. PTS is an
* array of NCHUNKS+1 (X, Y) indexes giving the diving points between
* sub sequences. The first sub-sequence is contained in [X0, X1),
* [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on. Note
* that (X0, Y0) == (XOFF, YOFF) and
* (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
*
* This function assumes that the first lines of the specified portions
* of the two files do not match, and likewise that the last lines do not
* match. The caller must trim matching lines from the beginning and end
* of the portions it is going to specify.
*/
function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks) {
$flip = false;

if ($xlim - $xoff > $ylim - $yoff) {
// Things seems faster (I'm not sure I understand why)
// when the shortest sequence in X.
$flip = true;
list ($xoff, $xlim, $yoff, $ylim)
= array( $yoff, $ylim, $xoff, $xlim);
}

if ($flip)
for ($i = $ylim - 1; $i >= $yoff; $i--)
$ymatches[$this->xv[$i]][] = $i;
else
for ($i = $ylim - 1; $i >= $yoff; $i--)
$ymatches[$this->yv[$i]][] = $i;

$this->lcs = 0;
$this->seq[0]= $yoff - 1;
$this->in_seq = array();
$ymids[0] = array();

$numer = $xlim - $xoff + $nchunks - 1;
$x = $xoff;
for ($chunk = 0; $chunk < $nchunks; $chunk++) {
if ($chunk > 0)
for ($i = 0; $i <= $this->lcs; $i++)
$ymids[$i][$chunk-1] = $this->seq[$i];

$x1 = $xoff + (int)(($numer + ($xlim-$xoff)*$chunk) / $nchunks);
for ( ; $x < $x1; $x++) {
$line = $flip ? $this->yv[$x] : $this->xv[$x];
if (empty($ymatches[$line]))
continue;
$matches = $ymatches[$line];
reset($matches);
while (list ($junk, $y) = each($matches))
if (empty($this->in_seq[$y])) {
$k = $this->_lcs_pos($y);
USE_ASSERTS && assert($k > 0);
$ymids[$k] = $ymids[$k-1];
break;
}
while (list ($junk, $y) = each($matches)) {
if ($y > $this->seq[$k-1]) {
USE_ASSERTS && assert($y < $this->seq[$k]);
// Optimization: this is a common case:
// next match is just replacing previous match.
$this->in_seq[$this->seq[$k]] = false;
$this->seq[$k] = $y;
$this->in_seq[$y] = 1;
}
else if (empty($this->in_seq[$y])) {
$k = $this->_lcs_pos($y);
USE_ASSERTS && assert($k > 0);
$ymids[$k] = $ymids[$k-1];
}
}
}
}

$seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
$ymid = $ymids[$this->lcs];
for ($n = 0; $n < $nchunks - 1; $n++) {
$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
$y1 = $ymid[$n] + 1;
$seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
}
$seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);

return array($this->lcs, $seps);
}

function _lcs_pos ($ypos) {
$end = $this->lcs;
if ($end == 0 || $ypos > $this->seq[$end]) {
$this->seq[++$this->lcs] = $ypos;
$this->in_seq[$ypos] = 1;
return $this->lcs;
}

$beg = 1;
while ($beg < $end) {
$mid = (int)(($beg + $end) / 2);
if ( $ypos > $this->seq[$mid] )
$beg = $mid + 1;
else
$end = $mid;
}

USE_ASSERTS && assert($ypos != $this->seq[$end]);

$this->in_seq[$this->seq[$end]] = false;
$this->seq[$end] = $ypos;
$this->in_seq[$ypos] = 1;
return $end;
}

/* Find LCS of two sequences.
*
* The results are recorded in the vectors $this->{x,y}changed[], by
* storing a 1 in the element for each line that is an insertion
* or deletion (ie. is not in the LCS).
*
* The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
*
* Note that XLIM, YLIM are exclusive bounds.
* All line numbers are origin-0 and discarded lines are not counted.
*/
function _compareseq ($xoff, $xlim, $yoff, $ylim) {
// Slide down the bottom initial diagonal.
while ($xoff < $xlim && $yoff < $ylim
&& $this->xv[$xoff] == $this->yv[$yoff]) {
++$xoff;
++$yoff;
}

// Slide up the top initial diagonal.
while ($xlim > $xoff && $ylim > $yoff
&& $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
--$xlim;
--$ylim;
}

if ($xoff == $xlim || $yoff == $ylim)
$lcs = 0;
else {
// This is ad hoc but seems to work well.
//$nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
//$nchunks = max(2,min(8,(int)$nchunks));
$nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
list ($lcs, $seps)
= $this->_diag($xoff,$xlim,$yoff, $ylim,$nchunks);
}

if ($lcs == 0) {
// X and Y sequences have no common subsequence:
// mark all changed.
while ($yoff < $ylim)
$this->ychanged[$this->yind[$yoff++]] = 1;
while ($xoff < $xlim)
$this->xchanged[$this->xind[$xoff++]] = 1;
}
else {
// Use the partitions to split this problem into subproblems.
reset($seps);
$pt1 = $seps[0];
while ($pt2 = next($seps)) {
$this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
$pt1 = $pt2;
}
}
}

/* Adjust inserts/deletes of identical lines to join changes
* as much as possible.
*
* We do something when a run of changed lines include a
* line at one end and has an excluded, identical line at the other.
* We are free to choose which identical line is included.
* `compareseq' usually chooses the one at the beginning,
* but usually it is cleaner to consider the following identical line
* to be the "change".
*
* This is extracted verbatim from analyze.c (GNU diffutils-2.7).
*/
function _shift_boundaries ($lines, &$changed, $other_changed) {
$i = 0;
$j = 0;

USE_ASSERTS && assert('sizeof($lines) == sizeof($changed)');
$len = sizeof($lines);
$other_len = sizeof($other_changed);

while (1) {
/*
* Scan forwards to find beginning of another run of changes.
* Also keep track of the corresponding point in the other file.
*
* Throughout this code, $i and $j are adjusted together so that
* the first $i elements of $changed and the first $j elements
* of $other_changed both contain the same number of zeros
* (unchanged lines).
* Furthermore, $j is always kept so that $j == $other_len or
* $other_changed[$j] == false.
*/
while ($j < $other_len && $other_changed[$j])
$j++;

while ($i < $len && ! $changed[$i]) {
USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
$i++; $j++;
while ($j < $other_len && $other_changed[$j])
$j++;
}

if ($i == $len)
break;

$start = $i;

// Find the end of this run of changes.
while (++$i < $len && $changed[$i])
continue;

do {
/*
* Record the length of this run of changes, so that
* we can later determine whether the run has grown.
*/
$runlength = $i - $start;

/*
* Move the changed region back, so long as the
* previous unchanged line matches the last changed one.
* This merges with previous changed regions.
*/
while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
$changed[--$start] = 1;
$changed[--$i] = false;
while ($start > 0 && $changed[$start - 1])
$start--;
USE_ASSERTS && assert('$j > 0');
while ($other_changed[--$j])
continue;
USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
}

/*
* Set CORRESPONDING to the end of the changed run, at the last
* point where it corresponds to a changed run in the other file.
* CORRESPONDING == LEN means no such point has been found.
*/
$corresponding = $j < $other_len ? $i : $len;

/*
* Move the changed region forward, so long as the
* first changed line matches the following unchanged one.
* This merges with following changed regions.
* Do this second, so that if there are no merges,
* the changed region is moved forward as far as possible.
*/
while ($i < $len && $lines[$start] == $lines[$i]) {
$changed[$start++] = false;
$changed[$i++] = 1;
while ($i < $len && $changed[$i])
$i++;

USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
$j++;
if ($j < $other_len && $other_changed[$j]) {
$corresponding = $i;
while ($j < $other_len && $other_changed[$j])
$j++;
}
}
} while ($runlength != $i - $start);

/*
* If possible, move the fully-merged run of changes
* back to a corresponding run in the other file.
*/
while ($corresponding < $i) {
$changed[--$start] = 1;
$changed[--$i] = 0;
USE_ASSERTS && assert('$j > 0');
while ($other_changed[--$j])
continue;
USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
}
}
}
}

/**
* Class representing a 'diff' between two sequences of strings.
*/
class Diff
{
var $edits;

/**
* Constructor.
* Computes diff between sequences of strings.
*
* @param $from_lines array An array of strings.
* (Typically these are lines from a file.)
* @param $to_lines array An array of strings.
*/
function Diff($from_lines, $to_lines) {
$eng = new _DiffEngine;
$this->edits = $eng->diff($from_lines, $to_lines);
}

}



/**
* A class to format Diffs
*
* This class formats the diff in classic diff format.
* It is intended that this class be customized via inheritance,
* to obtain fancier outputs.
*/
class DiffFormatter
{

/**
* Format a diff.
*
* @param $diff object A Diff object.
* @return string The formatted output.
*/
function format($diff) {

$xi = $yi = 1;
$block = false;
$context = array();

$this->_start_diff();

foreach ($diff->edits as $edit) {
if ($edit->type == 'copy') {
if (is_array($block)) {
if (sizeof($edit->orig) <= 0) {
$block[] = $edit;
}
else{
$this->_block($x0, + $xi - $x0,
$y0, + $yi - $y0,
$block);
$block = false;
}
}
}
else {
if (! is_array($block)) {
$x0 = $xi;
$y0 = $yi;
$block = array();
}
$block[] = $edit;
}

if ($edit->orig)
$xi += sizeof($edit->orig);
if ($edit->final)
$yi += sizeof($edit->final);
}

if (is_array($block))
$this->_block($x0, $xi - $x0,
$y0, $yi - $y0,
$block);

return $this->_end_diff();
}

function _block($xbeg, $xlen, $ybeg, $ylen, &$edits) {
$this->_start_block($this->_block_header($xbeg, $xlen, $ybeg, $ylen));
}

function _start_diff() {
ob_start();
}

function _end_diff() {
$val = ob_get_contents();
ob_end_clean();
return $val;
}

function _block_header($xbeg, $xlen, $ybeg, $ylen) {
if ($xlen > 1)
$xbeg .= "," . ($xbeg + $xlen - 1);
if ($ylen > 1)
$ybeg .= "," . ($ybeg + $ylen - 1);

return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;
}

function _start_block($header) {
echo $header."\n";
}

}

?>
</div>
%%