Text_Diff_Engine_native::_shiftBoundaries( $lines, $changed, $other_changed )

340    function _shiftBoundaries($lines, &$changed, $other_changed)341    {342        $i = 0;343        $j = 0;344 345        assert(count($lines) == count($changed));346        $len = count($lines);347        $other_len = count($other_changed);348 349        while (1) {350            /* Scan forward to find the beginning of another run of351             * changes. Also keep track of the corresponding point in the352             * other file.353             *354             * Throughout this code, $i and $j are adjusted together so that355             * the first $i elements of $changed and the first $j elements of356             * $other_changed both contain the same number of zeros (unchanged357             * lines).358             *359             * Furthermore, $j is always kept so that $j == $other_len or360             * $other_changed[$j] == false. */361            while ($j < $other_len && $other_changed[$j]) {362                $j++;363            }364 365            while ($i < $len && ! $changed[$i]) {366                assert($j < $other_len && ! $other_changed[$j]);367                $i++; $j++;368                while ($j < $other_len && $other_changed[$j]) {369                    $j++;370                }371            }372 373            if ($i == $len) {374                break;375            }376 377            $start = $i;378 379            /* Find the end of this run of changes. */380            while (++$i < $len && $changed[$i]) {381                continue;382            }383 384            do {385                /* Record the length of this run of changes, so that we can386                 * later determine whether the run has grown. */387                $runlength = $i - $start;388 389                /* Move the changed region back, so long as the previous390                 * unchanged line matches the last changed one.  This merges391                 * with previous changed regions. */392                while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {393                    $changed[--$start] = 1;394                    $changed[--$i] = false;395                    while ($start > 0 && $changed[$start - 1]) {396                        $start--;397                    }398                    assert($j > 0);399                    while ($other_changed[--$j]) {400                        continue;401                    }402                    assert($j >= 0 && !$other_changed[$j]);403                }404 405                /* Set CORRESPONDING to the end of the changed run, at the406                 * last point where it corresponds to a changed run in the407                 * other file. CORRESPONDING == LEN means no such point has408                 * been found. */409                $corresponding = $j < $other_len ? $i : $len;410 411                /* Move the changed region forward, so long as the first412                 * changed line matches the following unchanged one.  This413                 * merges with following changed regions.  Do this second, so414                 * that if there are no merges, the changed region is moved415                 * forward as far as possible. */416                while ($i < $len && $lines[$start] == $lines[$i]) {417                    $changed[$start++] = false;418                    $changed[$i++] = 1;419                    while ($i < $len && $changed[$i]) {