<?php
/** php下载类,支持断点续传
 *  Date:  2013-06-30
 *  Author: test
 *  Ver:  1.0
 *
 *  Func:
 *  download: 下载文件
 *  setSpeed: 设置下载速度
 *  getRange: 获取header中Range
 */

class FileDownload{ // class start 

    private $_speed = 512;  // 下载速度

    /** 下载
     * @param String $file  要下载的文件路径
     * @param String $name  文件名称,为空则与下载的文件名称一样
     * @param boolean $reload 是否开启断点续传
     */
    public function download($file, $name='',$file_size=0,$dateline=0, $reload=false){
        if($name==''){
            $name = basename($file);
        }
        if(!$dateline){
            $dataline=TIMESTAMP;
        }
        if(!$fp = fopen($file, 'rb')){
            topshowmessage(lang('file_not_exist1'));
        }
        $charset = CHARSET;
        $db = DB::object();
        $db->close();
        @ob_end_clean();
        if(getglobal('gzipcompress')) @ob_start('ob_gzhandler');
        if(!$file_size)   $file_size = filesize($file);
        $ranges = $this->getRange($file_size);

        header('cache-control:public');
        header('Date: '.gmdate('D, d M Y H:i:s', $dateline).' GMT');
        header('Last-Modified: '.gmdate('D, d M Y H:i:s', $dateline).' GMT');
        header('content-type:application/octet-stream');
        if (preg_match("/Firefox/", $_SERVER["HTTP_USER_AGENT"])) {
            $attachment = 'attachment; filename*='.$charset.'\'\'' . $name;
        } elseif (!preg_match("/Chrome/", $_SERVER["HTTP_USER_AGENT"]) && preg_match("/Safari/", $_SERVER["HTTP_USER_AGENT"])) {
            $filename = rawurlencode($name); // 注意：rawurlencode与urlencode的区别
            $attachment = 'attachment; filename*='.$charset.'\'\'' . $filename;
        } else{
            $attachment = 'attachment; filename='.$name;
        }
        //header('content-disposition:attachment; filename='.$name);
        header('content-disposition:'.$attachment);
        if($reload && $ranges!=null){ // 使用续传
            header('HTTP/1.1 206 Partial Content');
            header('Accept-Ranges:bytes');

            // 剩余长度
            header(sprintf('content-length:%u',$ranges['end']-$ranges['start']+1));

            // range信息
            header(sprintf('content-range:bytes %s-%s/%s', $ranges['start'], $ranges['end'], $file_size));

            // fp指针跳到断点位置
            fseek($fp, sprintf('%u', $ranges['start']));
        }else{
            header('HTTP/1.1 200 OK');
            header('content-length:'.$file_size);
        }

        while(!feof($fp)){
            echo fread($fp, round($this->_speed*1024,0));
            @flush(); @ob_flush();
            // usleep(500); // 用于测试,减慢下载速度
        }
        ($fp!=null) && fclose($fp);

    }

    /** 设置下载速度
     * @param int $speed
     */
    public function setSpeed($speed){
        if(is_numeric($speed) && $speed>16 && $speed<4096){
            $this->_speed = $speed;
        }
    }

    /** 获取header range信息
     * @param int  $file_size 文件大小
     * @return Array
     */
    private function getRange($file_size){

        if(isset($_SERVER['HTTP_RANGE'])){
            list($a, $range) = explode("=",$_SERVER['HTTP_RANGE'],2);
            list($range) = explode(",",$range,2);
            list($start, $range_end) = explode("-", $range);
            $start=intval($start);
            if(!$range_end) {
                $range_end=$file_size-1;
            } else {
                $range_end=intval($range_end);
            }
            $range = array('start'=>$start,'end'=>$range_end);
            return $range;
        }
        return null;
    }

} // class end 

?>