[php]多数据源串行分页算法

<?php
/**
 * 多数据源串行分页算法
 * @param arr $arrSourceCount 数据源标识=>元素数量
 * @param int $offset 起始位置
 * @param int $length 长度
 * @return arr 数据源标识=>array('offset'=>起始位置, 'length'=>长度)
 * @author flynetcn
 */
function multiSerialPaging($arrSourceCount, $offset=0, $length=10)
{
    $start = 0;
    $end = $offset + $length;
    $scopeList = array();
    foreach ($arrSourceCount as $k => $count) {
        $start += $count;
        if ($offset<$start && $offset>=$start-$count) {
            $scopeList[$k] = array(
                'offset'=>$offset-($start-$count),
            );
            if ($end > $start) {
                $scopeList[$k]['length'] = $count - $scopeList[$k]['offset'];
            }
        }
        if ($end<=$start && $end>$start-$count) {
            if ($offset >= $start-$count) {
                $scopeList[$k]['length'] = $length;
            } else {
                $scopeList[$k]['offset'] = 0;
                $scopeList[$k]['length'] = $length-($start-$count-$offset);
            }
        }
        if ($start<$end && $start-$count>$offset) {
            $scopeList[$k]['offset'] = 0;
            $scopeList[$k]['length'] = $count;
        }
    }
    return $scopeList;
}