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Text_Diff_Engine_native::_compareseq() public WP 1.0

Finds LCS of two sequences.

The results are recorded in the vectors $this->{x,y}changed[], by storing a 1 in the element for each line that is an insertion or deletion (ie. is not in the LCS).

The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.

Note that XLIM, YLIM are exclusive bounds. All line numbers are origin-0 and discarded lines are not counted.

{} It's a method of the class: Text_Diff_Engine_native{}

No Hooks.

Return

Null. Nothing.

Usage

$Text_Diff_Engine_native = new Text_Diff_Engine_native();
$Text_Diff_Engine_native->_compareseq ( $xoff, $xlim, $yoff, $ylim );

Code of Text_Diff_Engine_native::_compareseq() WP 5.5.1

<?php
function _compareseq ($xoff, $xlim, $yoff, $ylim)
{
    /* Slide down the bottom initial diagonal. */
    while ($xoff < $xlim && $yoff < $ylim
           && $this->xv[$xoff] == $this->yv[$yoff]) {
        ++$xoff;
        ++$yoff;
    }

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

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

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