_DiffEngine Class Reference

Collaboration diagram for _DiffEngine:

Public Member Functions
	diff ($from_lines, $to_lines)
	_line_hash ( $line)
	Returns the whole line if it's small enough, or the MD5 hash otherwise. More...
	_diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
	_lcs_pos ($ypos)
	_compareseq ($xoff, $xlim, $yoff, $ylim)
	_shift_boundaries ($lines, &$changed, $other_changed)

Data Fields
const	MAX_XREF_LENGTH = 10000

Detailed Description

Definition at line 781 of file class.WordLevelDiff.php.

Member Function Documentation

_compareseq()

_DiffEngine::_compareseq	(		$xoff,
			$xlim,
			$yoff,
			$ylim
	)

Definition at line 1025 of file class.WordLevelDiff.php.

                                                          {
                $fname = '_DiffEngine::_compareseq';
                //wfProfileIn( $fname );
 
                // 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;
                        }
                }
                //wfProfileOut( $fname );
        }

References _compareseq(), and _diag().

Referenced by _compareseq(), and diff().

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_diag()

_DiffEngine::_diag	(		$xoff,
			$xlim,
			$yoff,
			$ylim,
			$nchunks
	)

Definition at line 906 of file class.WordLevelDiff.php.

                                                              {
                $fname = '_DiffEngine::_diag';
                //wfProfileIn( $fname );
                $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; $chunk++) {
                        //wfProfileIn( "$fname-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];
                                        }
                                }
                        }
                        //wfProfileOut( "$fname-chunk" );
                }
 
                $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);
 
                //wfProfileOut( $fname );
                return array($this->lcs, $seps);
        }

References $n, _lcs_pos(), and USE_ASSERTS.

Referenced by _compareseq().

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_lcs_pos()

_DiffEngine::_lcs_pos

(

$ypos

)

Definition at line 984 of file class.WordLevelDiff.php.

                                  {
                $fname = '_DiffEngine::_lcs_pos';
                //wfProfileIn( $fname );
 
                $end = $this->lcs;
                if ($end == 0 || $ypos > $this->seq[$end]) {
                        $this->seq[++$this->lcs] = $ypos;
                        $this->in_seq[$ypos] = 1;
                        //wfProfileOut( $fname );
                        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;
                //wfProfileOut( $fname );
                return $end;
        }

References USE_ASSERTS.

Referenced by _diag().

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_line_hash()

_DiffEngine::_line_hash

(

$line

)

Returns the whole line if it's small enough, or the MD5 hash otherwise.

Definition at line 881 of file class.WordLevelDiff.php.

                                     {
                if ( strlen( $line ) > self::MAX_XREF_LENGTH ) {
                        return md5( $line );
                } else {
                        return $line;
                }
        }

Referenced by diff().

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_shift_boundaries()

_DiffEngine::_shift_boundaries	(		$lines,
		&	$changed,
			$other_changed
	)

Definition at line 1085 of file class.WordLevelDiff.php.

                                                                       {
                $fname = '_DiffEngine::_shift_boundaries';
                //wfProfileIn( $fname );
                $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]');
                        }
                }
                //wfProfileOut( $fname );
        }

References $changed, and USE_ASSERTS.

Referenced by diff().

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diff()

_DiffEngine::diff	(		$from_lines,
			$to_lines
	)

Definition at line 785 of file class.WordLevelDiff.php.

                                               {
                $fname = '_DiffEngine::diff';
                //wfProfileIn( $fname );
 
                $n_from = sizeof($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++) {
                        $xhash[$this->_line_hash($from_lines[$xi])] = 1;
                }
 
                for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
                        $line = $to_lines[$yi];
                        if ( ($this->ychanged[$yi] = empty($xhash[$this->_line_hash($line)])) )
                                continue;
                        $yhash[$this->_line_hash($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($yhash[$this->_line_hash($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);
                }
                //wfProfileOut( $fname );
                return $edits;
        }

References _compareseq(), _line_hash(), _shift_boundaries(), and USE_ASSERTS.

Referenced by Diff\Diff().

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Field Documentation

MAX_XREF_LENGTH

const _DiffEngine::MAX_XREF_LENGTH = 10000

Definition at line 783 of file class.WordLevelDiff.php.

---

The documentation for this class was generated from the following file:

• Services/COPage/mediawikidiff/class.WordLevelDiff.php