includes/diffengine/Engine/native.php
author Dan
Sun, 11 May 2008 16:59:45 -0400
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parent 1 fe660c52c48f
child 1227 bdac73ed481e
permissions -rw-r--r--
Moved some more images into sprites for Oxygen
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<?php
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/**
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 * Class used internally by Diff to actually compute the diffs.  This class is
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 * implemented using native PHP code.
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 *
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 * The algorithm used here is mostly lifted from the perl module
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 * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
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 * http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
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 *
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 * More ideas are taken from:
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 * http://www.ics.uci.edu/~eppstein/161/960229.html
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 *
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 * Some ideas (and a bit of code) are taken from analyze.c, of GNU
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 * diffutils-2.7, which can be found at:
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 * ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
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 *
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 * Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from
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 * Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this
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 * code was written by him, and is used/adapted with his permission.
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 *
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 * $Horde: framework/Text_Diff/Diff/Engine/native.php,v 1.3 2006/01/06 15:56:52 jan Exp $
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 *
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 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
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 * @package Text_Diff
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 *
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 * @access private
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 */
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class Text_Diff_Engine_native {
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    function diff($from_lines, $to_lines)
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    {
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        array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
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        array_walk($to_lines, array('Text_Diff', 'trimNewlines'));
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        $n_from = count($from_lines);
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        $n_to = count($to_lines);
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        $this->xchanged = $this->ychanged = array();
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        $this->xv = $this->yv = array();
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        $this->xind = $this->yind = array();
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        unset($this->seq);
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        unset($this->in_seq);
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        unset($this->lcs);
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        // Skip leading common lines.
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        for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
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            if ($from_lines[$skip] !== $to_lines[$skip]) {
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                break;
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            }
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            $this->xchanged[$skip] = $this->ychanged[$skip] = false;
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        }
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        // Skip trailing common lines.
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        $xi = $n_from; $yi = $n_to;
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        for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
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            if ($from_lines[$xi] !== $to_lines[$yi]) {
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                break;
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            }
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            $this->xchanged[$xi] = $this->ychanged[$yi] = false;
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        }
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        // Ignore lines which do not exist in both files.
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        for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
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            $xhash[$from_lines[$xi]] = 1;
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        }
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        for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
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            $line = $to_lines[$yi];
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            if (($this->ychanged[$yi] = empty($xhash[$line]))) {
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                continue;
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            }
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            $yhash[$line] = 1;
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            $this->yv[] = $line;
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            $this->yind[] = $yi;
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        }
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        for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
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            $line = $from_lines[$xi];
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            if (($this->xchanged[$xi] = empty($yhash[$line]))) {
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                continue;
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            }
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            $this->xv[] = $line;
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            $this->xind[] = $xi;
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        }
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        // Find the LCS.
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        $this->_compareseq(0, count($this->xv), 0, count($this->yv));
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        // Merge edits when possible.
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        $this->_shiftBoundaries($from_lines, $this->xchanged, $this->ychanged);
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        $this->_shiftBoundaries($to_lines, $this->ychanged, $this->xchanged);
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        // Compute the edit operations.
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        $edits = array();
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        $xi = $yi = 0;
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        while ($xi < $n_from || $yi < $n_to) {
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            assert($yi < $n_to || $this->xchanged[$xi]);
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            assert($xi < $n_from || $this->ychanged[$yi]);
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            // Skip matching "snake".
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            $copy = array();
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            while ($xi < $n_from && $yi < $n_to
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                   && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
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                $copy[] = $from_lines[$xi++];
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                ++$yi;
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            }
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            if ($copy) {
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                $edits[] = &new Text_Diff_Op_copy($copy);
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            }
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            // Find deletes & adds.
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            $delete = array();
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            while ($xi < $n_from && $this->xchanged[$xi]) {
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                $delete[] = $from_lines[$xi++];
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            }
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            $add = array();
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            while ($yi < $n_to && $this->ychanged[$yi]) {
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                $add[] = $to_lines[$yi++];
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            }
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            if ($delete && $add) {
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                $edits[] = &new Text_Diff_Op_change($delete, $add);
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            } elseif ($delete) {
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                $edits[] = &new Text_Diff_Op_delete($delete);
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            } elseif ($add) {
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                $edits[] = &new Text_Diff_Op_add($add);
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            }
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        }
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        return $edits;
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    }
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    /**
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     * Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
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     * XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized
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     * segments.
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     *
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     * Returns (LCS, PTS).  LCS is the length of the LCS. PTS is an array of
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     * NCHUNKS+1 (X, Y) indexes giving the diving points between sub
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     * sequences.  The first sub-sequence is contained in (X0, X1), (Y0, Y1),
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     * the second in (X1, X2), (Y1, Y2) and so on.  Note that (X0, Y0) ==
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     * (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
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     *
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     * This function assumes that the first lines of the specified portions of
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     * the two files do not match, and likewise that the last lines do not
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     * match.  The caller must trim matching lines from the beginning and end
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     * of the portions it is going to specify.
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     */
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    function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
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    {
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        $flip = false;
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        if ($xlim - $xoff > $ylim - $yoff) {
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            /* Things seems faster (I'm not sure I understand why) when the
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             * shortest sequence is in X. */
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            $flip = true;
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            list ($xoff, $xlim, $yoff, $ylim)
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                = array($yoff, $ylim, $xoff, $xlim);
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        }
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        if ($flip) {
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            for ($i = $ylim - 1; $i >= $yoff; $i--) {
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                $ymatches[$this->xv[$i]][] = $i;
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            }
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        } else {
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            for ($i = $ylim - 1; $i >= $yoff; $i--) {
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                $ymatches[$this->yv[$i]][] = $i;
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            }
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        }
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   169
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        $this->lcs = 0;
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        $this->seq[0]= $yoff - 1;
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        $this->in_seq = array();
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        $ymids[0] = array();
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   174
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        $numer = $xlim - $xoff + $nchunks - 1;
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        $x = $xoff;
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        for ($chunk = 0; $chunk < $nchunks; $chunk++) {
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            if ($chunk > 0) {
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                for ($i = 0; $i <= $this->lcs; $i++) {
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                    $ymids[$i][$chunk - 1] = $this->seq[$i];
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   181
                }
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            }
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   183
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            $x1 = $xoff + (int)(($numer + ($xlim-$xoff)*$chunk) / $nchunks);
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   185
            for (; $x < $x1; $x++) {
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   186
                $line = $flip ? $this->yv[$x] : $this->xv[$x];
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   187
                if (empty($ymatches[$line])) {
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                    continue;
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   189
                }
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                $matches = $ymatches[$line];
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   191
                foreach ($matches as $y) {
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   192
                    if (empty($this->in_seq[$y])) {
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                        $k = $this->_lcsPos($y);
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                        assert($k > 0);
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                        $ymids[$k] = $ymids[$k - 1];
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                        break;
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   197
                    }
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   198
                }
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   199
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                while (list($junk, $y) = each($matches)) {
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   201
                    if ($y > $this->seq[$k - 1]) {
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                        assert($y < $this->seq[$k]);
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                        /* Optimization: this is a common case: next match is
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                         * just replacing previous match. */
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                        $this->in_seq[$this->seq[$k]] = false;
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   206
                        $this->seq[$k] = $y;
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                        $this->in_seq[$y] = 1;
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   208
                    } elseif (empty($this->in_seq[$y])) {
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                        $k = $this->_lcsPos($y);
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                        assert($k > 0);
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                        $ymids[$k] = $ymids[$k - 1];
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diff changeset
   212
                    }
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   213
                }
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   214
            }
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   215
        }
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   216
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        $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
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        $ymid = $ymids[$this->lcs];
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   219
        for ($n = 0; $n < $nchunks - 1; $n++) {
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            $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
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   221
            $y1 = $ymid[$n] + 1;
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   222
            $seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
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   223
        }
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   224
        $seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
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   225
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        return array($this->lcs, $seps);
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   227
    }
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   228
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   229
    function _lcsPos($ypos)
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diff changeset
   230
    {
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   231
        $end = $this->lcs;
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diff changeset
   232
        if ($end == 0 || $ypos > $this->seq[$end]) {
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diff changeset
   233
            $this->seq[++$this->lcs] = $ypos;
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diff changeset
   234
            $this->in_seq[$ypos] = 1;
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   235
            return $this->lcs;
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   236
        }
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   237
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   238
        $beg = 1;
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diff changeset
   239
        while ($beg < $end) {
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   240
            $mid = (int)(($beg + $end) / 2);
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diff changeset
   241
            if ($ypos > $this->seq[$mid]) {
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diff changeset
   242
                $beg = $mid + 1;
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diff changeset
   243
            } else {
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diff changeset
   244
                $end = $mid;
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diff changeset
   245
            }
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diff changeset
   246
        }
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diff changeset
   247
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diff changeset
   248
        assert($ypos != $this->seq[$end]);
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diff changeset
   249
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   250
        $this->in_seq[$this->seq[$end]] = false;
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diff changeset
   251
        $this->seq[$end] = $ypos;
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diff changeset
   252
        $this->in_seq[$ypos] = 1;
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diff changeset
   253
        return $end;
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diff changeset
   254
    }
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   255
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diff changeset
   256
    /**
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diff changeset
   257
     * Finds LCS of two sequences.
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diff changeset
   258
     *
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   259
     * The results are recorded in the vectors $this->{x,y}changed[], by
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diff changeset
   260
     * storing a 1 in the element for each line that is an insertion or
fe660c52c48f Adding /includes
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diff changeset
   261
     * deletion (ie. is not in the LCS).
fe660c52c48f Adding /includes
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diff changeset
   262
     *
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diff changeset
   263
     * The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
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diff changeset
   264
     *
fe660c52c48f Adding /includes
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diff changeset
   265
     * Note that XLIM, YLIM are exclusive bounds.  All line numbers are
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diff changeset
   266
     * origin-0 and discarded lines are not counted.
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diff changeset
   267
     */
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diff changeset
   268
    function _compareseq ($xoff, $xlim, $yoff, $ylim)
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diff changeset
   269
    {
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   270
        /* Slide down the bottom initial diagonal. */
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diff changeset
   271
        while ($xoff < $xlim && $yoff < $ylim
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diff changeset
   272
               && $this->xv[$xoff] == $this->yv[$yoff]) {
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diff changeset
   273
            ++$xoff;
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diff changeset
   274
            ++$yoff;
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diff changeset
   275
        }
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diff changeset
   276
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   277
        /* Slide up the top initial diagonal. */
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diff changeset
   278
        while ($xlim > $xoff && $ylim > $yoff
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diff changeset
   279
               && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
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diff changeset
   280
            --$xlim;
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diff changeset
   281
            --$ylim;
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diff changeset
   282
        }
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parents:
diff changeset
   283
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diff changeset
   284
        if ($xoff == $xlim || $yoff == $ylim) {
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parents:
diff changeset
   285
            $lcs = 0;
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parents:
diff changeset
   286
        } else {
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diff changeset
   287
            /* This is ad hoc but seems to work well.  $nchunks =
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parents:
diff changeset
   288
             * sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5); $nchunks =
fe660c52c48f Adding /includes
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parents:
diff changeset
   289
             * max(2,min(8,(int)$nchunks)); */
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parents:
diff changeset
   290
            $nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
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diff changeset
   291
            list($lcs, $seps)
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diff changeset
   292
                = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
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parents:
diff changeset
   293
        }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   294
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   295
        if ($lcs == 0) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   296
            /* X and Y sequences have no common subsequence: mark all
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   297
             * changed. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   298
            while ($yoff < $ylim) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   299
                $this->ychanged[$this->yind[$yoff++]] = 1;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   300
            }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   301
            while ($xoff < $xlim) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   302
                $this->xchanged[$this->xind[$xoff++]] = 1;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   303
            }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   304
        } else {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   305
            /* Use the partitions to split this problem into subproblems. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   306
            reset($seps);
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   307
            $pt1 = $seps[0];
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   308
            while ($pt2 = next($seps)) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   309
                $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   310
                $pt1 = $pt2;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   311
            }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   312
        }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   313
    }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   314
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   315
    /**
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   316
     * Adjusts inserts/deletes of identical lines to join changes as much as
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   317
     * possible.
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   318
     *
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   319
     * We do something when a run of changed lines include a line at one end
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   320
     * and has an excluded, identical line at the other.  We are free to
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   321
     * choose which identical line is included.  `compareseq' usually chooses
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   322
     * the one at the beginning, but usually it is cleaner to consider the
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   323
     * following identical line to be the "change".
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   324
     *
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   325
     * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   326
     */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   327
    function _shiftBoundaries($lines, &$changed, $other_changed)
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   328
    {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   329
        $i = 0;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   330
        $j = 0;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   331
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   332
        assert('count($lines) == count($changed)');
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   333
        $len = count($lines);
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   334
        $other_len = count($other_changed);
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   335
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   336
        while (1) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   337
            /* Scan forward to find the beginning of another run of
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   338
             * changes. Also keep track of the corresponding point in the
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   339
             * other file.
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   340
             *
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   341
             * Throughout this code, $i and $j are adjusted together so that
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   342
             * the first $i elements of $changed and the first $j elements of
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   343
             * $other_changed both contain the same number of zeros (unchanged
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   344
             * lines).
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   345
             *
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   346
             * Furthermore, $j is always kept so that $j == $other_len or
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   347
             * $other_changed[$j] == false. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   348
            while ($j < $other_len && $other_changed[$j]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   349
                $j++;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   350
            }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   351
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   352
            while ($i < $len && ! $changed[$i]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   353
                assert('$j < $other_len && ! $other_changed[$j]');
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   354
                $i++; $j++;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   355
                while ($j < $other_len && $other_changed[$j]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   356
                    $j++;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   357
                }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   358
            }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   359
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   360
            if ($i == $len) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   361
                break;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   362
            }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   363
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   364
            $start = $i;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   365
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   366
            /* Find the end of this run of changes. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   367
            while (++$i < $len && $changed[$i]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   368
                continue;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   369
            }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   370
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   371
            do {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   372
                /* Record the length of this run of changes, so that we can
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   373
                 * later determine whether the run has grown. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   374
                $runlength = $i - $start;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   375
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   376
                /* Move the changed region back, so long as the previous
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   377
                 * unchanged line matches the last changed one.  This merges
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   378
                 * with previous changed regions. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   379
                while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   380
                    $changed[--$start] = 1;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   381
                    $changed[--$i] = false;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   382
                    while ($start > 0 && $changed[$start - 1]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   383
                        $start--;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   384
                    }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   385
                    assert('$j > 0');
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   386
                    while ($other_changed[--$j]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   387
                        continue;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   388
                    }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   389
                    assert('$j >= 0 && !$other_changed[$j]');
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   390
                }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   391
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   392
                /* Set CORRESPONDING to the end of the changed run, at the
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   393
                 * last point where it corresponds to a changed run in the
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   394
                 * other file. CORRESPONDING == LEN means no such point has
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   395
                 * been found. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   396
                $corresponding = $j < $other_len ? $i : $len;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   397
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   398
                /* Move the changed region forward, so long as the first
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   399
                 * changed line matches the following unchanged one.  This
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   400
                 * merges with following changed regions.  Do this second, so
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   401
                 * that if there are no merges, the changed region is moved
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   402
                 * forward as far as possible. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   403
                while ($i < $len && $lines[$start] == $lines[$i]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   404
                    $changed[$start++] = false;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   405
                    $changed[$i++] = 1;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   406
                    while ($i < $len && $changed[$i]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   407
                        $i++;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   408
                    }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   409
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   410
                    assert('$j < $other_len && ! $other_changed[$j]');
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   411
                    $j++;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   412
                    if ($j < $other_len && $other_changed[$j]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   413
                        $corresponding = $i;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   414
                        while ($j < $other_len && $other_changed[$j]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   415
                            $j++;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   416
                        }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   417
                    }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   418
                }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   419
            } while ($runlength != $i - $start);
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   420
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   421
            /* If possible, move the fully-merged run of changes back to a
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   422
             * corresponding run in the other file. */
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   423
            while ($corresponding < $i) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   424
                $changed[--$start] = 1;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   425
                $changed[--$i] = 0;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   426
                assert('$j > 0');
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   427
                while ($other_changed[--$j]) {
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   428
                    continue;
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   429
                }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   430
                assert('$j >= 0 && !$other_changed[$j]');
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   431
            }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   432
        }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   433
    }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   434
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   435
}