includes/diffengine/Engine/native.php
author Dan
Fri, 05 Oct 2007 01:57:00 -0400
changeset 161 e1a22031b5bd
parent 1 fe660c52c48f
permissions -rw-r--r--
Major revamps to the template parser. Fixed a few security holes that could allow PHP to be injected in untimely places in TPL code. Improved Ux for XSS attempt in tplWikiFormat. Documented many functions. Backported much cleaner parser from 2.0 branch. Beautified a lot of code in the depths of the template class. Pretty much a small-scale Extreme Makeover.
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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]][] = $i;
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   163
            }
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        } else {
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            for ($i = $ylim - 1; $i >= $yoff; $i--) {
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                $ymatches[$this->yv[$i]][] = $i;
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   167
            }
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        }
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parents:
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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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   176
        $x = $xoff;
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   177
        for ($chunk = 0; $chunk < $nchunks; $chunk++) {
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   178
            if ($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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   182
            }
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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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   188
                    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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   205
                        $this->in_seq[$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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diff changeset
   208
                    } elseif (empty($this->in_seq[$y])) {
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   209
                        $k = $this->_lcsPos($y);
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   210
                        assert($k > 0);
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   211
                        $ymids[$k] = $ymids[$k - 1];
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diff changeset
   212
                    }
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   213
                }
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diff changeset
   214
            }
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diff changeset
   215
        }
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   216
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        $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
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   218
        $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, $seps);
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diff changeset
   227
    }
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   228
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   229
    function _lcsPos($ypos)
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diff changeset
   230
    {
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diff changeset
   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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diff changeset
   235
            return $this->lcs;
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diff changeset
   236
        }
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diff changeset
   237
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diff changeset
   238
        $beg = 1;
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diff changeset
   239
        while ($beg < $end) {
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diff changeset
   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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diff changeset
   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 $this->{x,y}changed[], by
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diff changeset
   260
     * storing a 1 in the element for each line that is an insertion or
fe660c52c48f Adding /includes
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diff changeset
   261
     * deletion (ie. is not in the LCS).
fe660c52c48f Adding /includes
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diff changeset
   262
     *
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diff changeset
   263
     * The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
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parents:
diff changeset
   264
     *
fe660c52c48f Adding /includes
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diff changeset
   265
     * Note that XLIM, YLIM are exclusive bounds.  All line numbers are
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diff changeset
   266
     * origin-0 and discarded lines are not counted.
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diff changeset
   267
     */
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diff changeset
   268
    function _compareseq ($xoff, $xlim, $yoff, $ylim)
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parents:
diff changeset
   269
    {
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diff changeset
   270
        /* Slide down the bottom initial diagonal. */
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diff changeset
   271
        while ($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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parents:
diff changeset
   276
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diff changeset
   277
        /* Slide up the top initial diagonal. */
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parents:
diff changeset
   278
        while ($xlim > $xoff && $ylim > $yoff
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parents:
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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parents:
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 - $yoff) + 1;
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parents:
diff changeset
   291
            list($lcs, $seps)
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parents:
diff changeset
   292
                = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   293
        }
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   294
fe660c52c48f Adding /includes
dan@scribus.fuhry.local.fuhry.local
parents:
diff changeset
   295
        if ($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
}