--- /dev/null
+<?php
+/* Copyright (C) 2008 Guy Van den Broeck <guy@guyvdb.eu>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ * or see http://www.gnu.org/
+ */
+
+/**
+ * This diff implementation is mainly lifted from the LCS algorithm of the Eclipse project which
+ * in turn is based on Myers' "An O(ND) difference algorithm and its variations"
+ * (http://citeseer.ist.psu.edu/myers86ond.html) with range compression (see Wu et al.'s
+ * "An O(NP) Sequence Comparison Algorithm").
+ *
+ * This implementation supports an upper bound on the excution time.
+ *
+ * Complexity: O((M + N)D) worst case time, O(M + N + D^2) expected time, O(M + N) space
+ *
+ * @author Guy Van den Broeck
+ * @ingroup DifferenceEngine
+ */
+class WikiDiff3 {
+
+ //Input variables
+ private $from;
+ private $to;
+ private $m;
+ private $n;
+
+ private $tooLong;
+ private $powLimit;
+
+ //State variables
+ private $maxDifferences;
+ private $lcsLengthCorrectedForHeuristic = false;
+
+ //Output variables
+ public $length;
+ public $removed;
+ public $added;
+ public $heuristicUsed;
+
+ function __construct($tooLong = 2000000, $powLimit = 1.45){
+ $this->tooLong = $tooLong;
+ $this->powLimit = $powLimit;
+ }
+
+ public function diff(/*array*/ $from, /*array*/ $to){
+ //remember initial lengths
+ $m = sizeof($from);
+ $n = count($to);
+
+ $this->heuristicUsed = false;
+
+ //output
+ $removed = $m > 0 ? array_fill(0, $m, true) : array();
+ $added = $n > 0 ? array_fill(0, $n, true) : array();
+
+ //reduce the complexity for the next step (intentionally done twice)
+ //remove common tokens at the start
+ $i = 0;
+ while($i < $m && $i < $n && $from[$i] === $to[$i]) {
+ $removed[$i] = $added[$i] = false;
+ unset($from[$i], $to[$i]);
+ ++$i;
+ }
+
+ //remove common tokens at the end
+ $j = 1;
+ while($i + $j <= $m && $i + $j <= $n && $from[$m - $j] === $to[$n - $j]) {
+ $removed[$m - $j] = $added[$n - $j] = false;
+ unset($from[$m - $j], $to[$n - $j]);
+ ++$j;
+ }
+
+ $this->from = $newFromIndex = $this->to = $newToIndex = array();
+
+ //remove tokens not in both sequences
+ $shared = array();
+ foreach( $from as $key ) {
+ $shared[$key] = false;
+ }
+
+ foreach($to as $index => &$el) {
+ if(array_key_exists($el, $shared)) {
+ //keep it
+ $this->to[] = $el;
+ $shared[$el] = true;
+ $newToIndex[] = $index;
+ }
+ }
+ foreach($from as $index => &$el) {
+ if($shared[$el]) {
+ //keep it
+ $this->from[] = $el;
+ $newFromIndex[] = $index;
+ }
+ }
+
+ unset($shared, $from, $to);
+
+ $this->m = count($this->from);
+ $this->n = count($this->to);
+
+ $this->removed = $this->m > 0 ? array_fill(0, $this->m, true) : array();
+ $this->added = $this->n > 0 ? array_fill(0, $this->n, true) : array();
+
+ if ($this->m == 0 || $this->n == 0) {
+ $this->length = 0;
+ } else {
+ $this->maxDifferences = ceil(($this->m + $this->n) / 2.0);
+ if ($this->m * $this->n > $this->tooLong) {
+ // limit complexity to D^POW_LIMIT for long sequences
+ $this->maxDifferences = floor(pow($this->maxDifferences, $this->powLimit - 1.0));
+ wfDebug("Limiting max number of differences to $this->maxDifferences\n");
+ }
+
+ /*
+ * The common prefixes and suffixes are always part of some LCS, include
+ * them now to reduce our search space
+ */
+ $max = min($this->m, $this->n);
+ for ($forwardBound = 0; $forwardBound < $max
+ && $this->from[$forwardBound] === $this->to[$forwardBound];
+ ++$forwardBound) {
+ $this->removed[$forwardBound] = $this->added[$forwardBound] = false;
+ }
+
+ $backBoundL1 = $this->m - 1;
+ $backBoundL2 = $this->n - 1;
+
+ while ($backBoundL1 >= $forwardBound && $backBoundL2 >= $forwardBound
+ && $this->from[$backBoundL1] === $this->to[$backBoundL2]) {
+ $this->removed[$backBoundL1--] = $this->added[$backBoundL2--] = false;
+ }
+
+ $temp = array_fill(0, $this->m + $this->n + 1, 0);
+ $V = array($temp, $temp);
+ $snake = array(0, 0, 0);
+
+ $this->length = $forwardBound + $this->m - $backBoundL1 - 1
+ + $this->lcs_rec($forwardBound, $backBoundL1,
+ $forwardBound, $backBoundL2, $V, $snake);
+ }
+
+ $this->m = $m;
+ $this->n = $n;
+
+ $this->length += $i + $j - 1;
+
+ foreach($this->removed as $key => &$removed_elem) {
+ if(!$removed_elem) {
+ $removed[$newFromIndex[$key]] = false;
+ }
+ }
+ foreach($this->added as $key => &$added_elem) {
+ if(!$added_elem) {
+ $added[$newToIndex[$key]] = false;
+ }
+ }
+ $this->removed = $removed;
+ $this->added = $added;
+ }
+
+ function diff_range($from_lines, $to_lines) {
+ // Diff and store locally
+ $this->diff($from_lines, $to_lines);
+ unset($from_lines, $to_lines);
+
+ $ranges = array();
+ $xi = $yi = 0;
+ while ($xi < $this->m || $yi < $this->n) {
+ // Matching "snake".
+ while ($xi < $this->m && $yi < $this->n
+ && !$this->removed[$xi]
+ && !$this->added[$yi]) {
+ ++$xi;
+ ++$yi;
+ }
+ // Find deletes & adds.
+ $xstart = $xi;
+ while ($xi < $this->m && $this->removed[$xi]) {
+ ++$xi;
+ }
+
+ $ystart = $yi;
+ while ($yi < $this->n && $this->added[$yi]) {
+ ++$yi;
+ }
+
+ if ($xi > $xstart || $yi > $ystart) {
+ $ranges[] = new RangeDifference($xstart, $xi,
+ $ystart, $yi);
+ }
+ }
+ return $ranges;
+ }
+
+ private function lcs_rec($bottoml1, $topl1, $bottoml2, $topl2, &$V, &$snake) {
+ // check that both sequences are non-empty
+ if ($bottoml1 > $topl1 || $bottoml2 > $topl2) {
+ return 0;
+ }
+
+ $d = $this->find_middle_snake($bottoml1, $topl1, $bottoml2,
+ $topl2, $V, $snake);
+
+ // need to store these so we don't lose them when they're
+ // overwritten by the recursion
+ $len = $snake[2];
+ $startx = $snake[0];
+ $starty = $snake[1];
+
+ // the middle snake is part of the LCS, store it
+ for ($i = 0; $i < $len; ++$i) {
+ $this->removed[$startx + $i] = $this->added[$starty + $i] = false;
+ }
+
+ if ($d > 1) {
+ return $len
+ + $this->lcs_rec($bottoml1, $startx - 1, $bottoml2,
+ $starty - 1, $V, $snake)
+ + $this->lcs_rec($startx + $len, $topl1, $starty + $len,
+ $topl2, $V, $snake);
+ } else if ($d == 1) {
+ /*
+ * In this case the sequences differ by exactly 1 line. We have
+ * already saved all the lines after the difference in the for loop
+ * above, now we need to save all the lines before the difference.
+ */
+ $max = min($startx - $bottoml1, $starty - $bottoml2);
+ for ($i = 0; $i < $max; ++$i) {
+ $this->removed[$bottoml1 + $i] =
+ $this->added[$bottoml2 + $i] = false;
+ }
+ return $max + $len;
+ }
+ return $len;
+ }
+
+ private function find_middle_snake($bottoml1, $topl1, $bottoml2,$topl2, &$V, &$snake) {
+ $from = &$this->from;
+ $to = &$this->to;
+ $V0 = &$V[0];
+ $V1 = &$V[1];
+ $snake0 = &$snake[0];
+ $snake1 = &$snake[1];
+ $snake2 = &$snake[2];
+ $bottoml1_min_1 = $bottoml1-1;
+ $bottoml2_min_1 = $bottoml2-1;
+ $N = $topl1 - $bottoml1_min_1;
+ $M = $topl2 - $bottoml2_min_1;
+ $delta = $N - $M;
+ $maxabsx = $N+$bottoml1;
+ $maxabsy = $M+$bottoml2;
+ $limit = min($this->maxDifferences, ceil(($N + $M ) / 2));
+
+ //value_to_add_forward: a 0 or 1 that we add to the start
+ // offset to make it odd/even
+ if (($M & 1) == 1) {
+ $value_to_add_forward = 1;
+ } else {
+ $value_to_add_forward = 0;
+ }
+
+ if (($N & 1) == 1) {
+ $value_to_add_backward = 1;
+ } else {
+ $value_to_add_backward = 0;
+ }
+
+ $start_forward = -$M;
+ $end_forward = $N;
+ $start_backward = -$N;
+ $end_backward = $M;
+
+ $limit_min_1 = $limit - 1;
+ $limit_plus_1 = $limit + 1;
+
+ $V0[$limit_plus_1] = 0;
+ $V1[$limit_min_1] = $N;
+ $limit = min($this->maxDifferences, ceil(($N + $M ) / 2));
+
+ if (($delta & 1) == 1) {
+ for ($d = 0; $d <= $limit; ++$d) {
+ $start_diag = max($value_to_add_forward + $start_forward, -$d);
+ $end_diag = min($end_forward, $d);
+ $value_to_add_forward = 1 - $value_to_add_forward;
+
+ // compute forward furthest reaching paths
+ for ($k = $start_diag; $k <= $end_diag; $k += 2) {
+ if ($k == -$d || ($k < $d
+ && $V0[$limit_min_1 + $k] < $V0[$limit_plus_1 + $k])) {
+ $x = $V0[$limit_plus_1 + $k];
+ } else {
+ $x = $V0[$limit_min_1 + $k] + 1;
+ }
+
+ $absx = $snake0 = $x + $bottoml1;
+ $absy = $snake1 = $x - $k + $bottoml2;
+
+ while ($absx < $maxabsx && $absy < $maxabsy && $from[$absx] === $to[$absy]) {
+ ++$absx;
+ ++$absy;
+ }
+ $x = $absx-$bottoml1;
+
+ $snake2 = $absx -$snake0;
+ $V0[$limit + $k] = $x;
+ if ($k >= $delta - $d + 1 && $k <= $delta + $d - 1
+ && $x >= $V1[$limit + $k - $delta]) {
+ return 2 * $d - 1;
+ }
+
+ // check to see if we can cut down the diagonal range
+ if ($x >= $N && $end_forward > $k - 1) {
+ $end_forward = $k - 1;
+ } else if ($absy - $bottoml2 >= $M) {
+ $start_forward = $k + 1;
+ $value_to_add_forward = 0;
+ }
+ }
+
+ $start_diag = max($value_to_add_backward + $start_backward, -$d);
+ $end_diag = min($end_backward, $d);
+ $value_to_add_backward = 1 - $value_to_add_backward;
+
+ // compute backward furthest reaching paths
+ for ($k = $start_diag; $k <= $end_diag; $k += 2) {
+ if ($k == $d
+ || ($k != -$d && $V1[$limit_min_1 + $k] < $V1[$limit_plus_1 + $k])) {
+ $x = $V1[$limit_min_1 + $k];
+ } else {
+ $x = $V1[$limit_plus_1 + $k] - 1;
+ }
+
+ $y = $x - $k - $delta;
+
+ $snake2 = 0;
+ while ($x > 0 && $y > 0
+ && $from[$x +$bottoml1_min_1] === $to[$y + $bottoml2_min_1]) {
+ --$x;
+ --$y;
+ ++$snake2;
+ }
+ $V1[$limit + $k] = $x;
+
+ // check to see if we can cut down our diagonal range
+ if ($x <= 0) {
+ $start_backward = $k + 1;
+ $value_to_add_backward = 0;
+ } else if ($y <= 0 && $end_backward > $k - 1) {
+ $end_backward = $k - 1;
+ }
+ }
+ }
+ } else {
+ for ($d = 0; $d <= $limit; ++$d) {
+ $start_diag = max($value_to_add_forward + $start_forward, -$d);
+ $end_diag = min($end_forward, $d);
+ $value_to_add_forward = 1 - $value_to_add_forward;
+
+ // compute forward furthest reaching paths
+ for ($k = $start_diag; $k <= $end_diag; $k += 2) {
+ if ($k == -$d
+ || ($k < $d && $V0[$limit_min_1 + $k] < $V0[$limit_plus_1 + $k])) {
+ $x = $V0[$limit_plus_1 + $k];
+ } else {
+ $x = $V0[$limit_min_1 + $k] + 1;
+ }
+
+ $absx = $snake0 = $x + $bottoml1;
+ $absy = $snake1 = $x - $k + $bottoml2;
+
+ while ($absx < $maxabsx && $absy < $maxabsy && $from[$absx] === $to[$absy]) {
+ ++$absx;
+ ++$absy;
+ }
+ $x = $absx-$bottoml1;
+ $snake2 = $absx -$snake0;
+ $V0[$limit + $k] = $x;
+
+ // check to see if we can cut down the diagonal range
+ if ($x >= $N && $end_forward > $k - 1) {
+ $end_forward = $k - 1;
+ } else if ($absy-$bottoml2 >= $M) {
+ $start_forward = $k + 1;
+ $value_to_add_forward = 0;
+ }
+ }
+
+ $start_diag = max($value_to_add_backward + $start_backward, -$d);
+ $end_diag = min($end_backward, $d);
+ $value_to_add_backward = 1 - $value_to_add_backward;
+
+ // compute backward furthest reaching paths
+ for ($k = $start_diag; $k <= $end_diag; $k += 2) {
+ if ($k == $d
+ || ($k != -$d && $V1[$limit_min_1 + $k] < $V1[$limit_plus_1 + $k])) {
+ $x = $V1[$limit_min_1 + $k];
+ } else {
+ $x = $V1[$limit_plus_1 + $k] - 1;
+ }
+
+ $y = $x - $k - $delta;
+
+ $snake2 = 0;
+ while ($x > 0 && $y > 0
+ && $from[$x +$bottoml1_min_1] === $to[$y + $bottoml2_min_1]) {
+ --$x;
+ --$y;
+ ++$snake2;
+ }
+ $V1[$limit + $k] = $x;
+
+ if ($k >= -$delta - $d && $k <= $d - $delta
+ && $x <= $V0[$limit + $k + $delta]) {
+ $snake0 = $bottoml1 + $x;
+ $snake1 = $bottoml2 + $y;
+ return 2 * $d;
+ }
+
+ // check to see if we can cut down our diagonal range
+ if ($x <= 0) {
+ $start_backward = $k + 1;
+ $value_to_add_backward = 0;
+ } else if ($y <= 0 && $end_backward > $k - 1) {
+ $end_backward = $k - 1;
+ }
+ }
+ }
+ }
+ /*
+ * computing the true LCS is too expensive, instead find the diagonal
+ * with the most progress and pretend a midle snake of length 0 occurs
+ * there.
+ */
+
+ $most_progress = self::findMostProgress($M, $N, $limit, $V);
+
+ $snake0 = $bottoml1 + $most_progress[0];
+ $snake1 = $bottoml2 + $most_progress[1];
+ $snake2 = 0;
+ wfDebug("Computing the LCS is too expensive. Using a heuristic.\n");
+ $this->heuristicUsed = true;
+ return 5; /*
+ * HACK: since we didn't really finish the LCS computation
+ * we don't really know the length of the SES. We don't do
+ * anything with the result anyway, unless it's <=1. We know
+ * for a fact SES > 1 so 5 is as good a number as any to
+ * return here
+ */
+ }
+
+ private static function findMostProgress($M, $N, $limit, $V) {
+ $delta = $N - $M;
+
+ if (($M & 1) == ($limit & 1)) {
+ $forward_start_diag = max(-$M, -$limit);
+ } else {
+ $forward_start_diag = max(1 - $M, -$limit);
+ }
+
+ $forward_end_diag = min($N, $limit);
+
+ if (($N & 1) == ($limit & 1)) {
+ $backward_start_diag = max(-$N, -$limit);
+ } else {
+ $backward_start_diag = max(1 - $N, -$limit);
+ }
+
+ $backward_end_diag = -min($M, $limit);
+
+ $temp = array(0, 0, 0);
+
+
+ $max_progress = array_fill(0, ceil(max($forward_end_diag - $forward_start_diag,
+ $backward_end_diag - $backward_start_diag) / 2), $temp);
+ $num_progress = 0; // the 1st entry is current, it is initialized
+ // with 0s
+
+ // first search the forward diagonals
+ for ($k = $forward_start_diag; $k <= $forward_end_diag; $k += 2) {
+ $x = $V[0][$limit + $k];
+ $y = $x - $k;
+ if ($x > $N || $y > $M) {
+ continue;
+ }
+
+ $progress = $x + $y;
+ if ($progress > $max_progress[0][2]) {
+ $num_progress = 0;
+ $max_progress[0][0] = $x;
+ $max_progress[0][1] = $y;
+ $max_progress[0][2] = $progress;
+ } else if ($progress == $max_progress[0][2]) {
+ ++$num_progress;
+ $max_progress[$num_progress][0] = $x;
+ $max_progress[$num_progress][1] = $y;
+ $max_progress[$num_progress][2] = $progress;
+ }
+ }
+
+ $max_progress_forward = true; // initially the maximum
+ // progress is in the forward
+ // direction
+
+ // now search the backward diagonals
+ for ($k = $backward_start_diag; $k <= $backward_end_diag; $k += 2) {
+ $x = $V[1][$limit + $k];
+ $y = $x - $k - $delta;
+ if ($x < 0 || $y < 0) {
+ continue;
+ }
+
+ $progress = $N - $x + $M - $y;
+ if ($progress > $max_progress[0][2]) {
+ $num_progress = 0;
+ $max_progress_forward = false;
+ $max_progress[0][0] = $x;
+ $max_progress[0][1] = $y;
+ $max_progress[0][2] = $progress;
+ } else if ($progress == $max_progress[0][2] && !$max_progress_forward) {
+ ++$num_progress;
+ $max_progress[$num_progress][0] = $x;
+ $max_progress[$num_progress][1] = $y;
+ $max_progress[$num_progress][2] = $progress;
+ }
+ }
+
+ // return the middle diagonal with maximal progress.
+ return $max_progress[floor($num_progress / 2)];
+ }
+
+ public function getLcsLength(){
+ if($this->heuristicUsed && !$this->lcsLengthCorrectedForHeuristic){
+ $this->lcsLengthCorrectedForHeuristic = true;
+ $this->length = $this->m-array_sum($this->added);
+ }
+ return $this->length;
+ }
+
+}
+
+/**
+ * Alternative representation of a set of changes, by the index
+ * ranges that are changed.
+ *
+ * @ingroup DifferenceEngine
+ */
+class RangeDifference {
+
+ public $leftstart;
+ public $leftend;
+ public $leftlength;
+
+ public $rightstart;
+ public $rightend;
+ public $rightlength;
+
+ function __construct($leftstart, $leftend, $rightstart, $rightend){
+ $this->leftstart = $leftstart;
+ $this->leftend = $leftend;
+ $this->leftlength = $leftend - $leftstart;
+ $this->rightstart = $rightstart;
+ $this->rightend = $rightend;
+ $this->rightlength = $rightend - $rightstart;
+ }
+}
scripts.mit.edu / autoinstalls / mediawiki.git / blobdiff