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1. Principle of resumed transfer at breakpoint
The so-called resumed transfer at breakpoint means Continue downloading from where the file was already downloaded. Breakpoints were not supported in previous versions of the HTTP protocol, but have been supported since HTTP/1.1. Generally, the Range and Content-Range entity headers are only used for breakpoint downloading.
Do not use breakpoint resumption
get /down.zip http/1.1 accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.ms- excel, application/msword, application/vnd.ms-powerpoint, */* accept-language: zh-cn accept-encoding: gzip, deflate user-agent: mozilla/4.0 (compatible; msie 5.01; windows nt 5.0) connection: keep-alive
After the server receives the request, it searches for the requested file as required, extracts the file information, and then returns it to the browser. The return information is as follows:
HTTP/1.1 200 Ok content-length=106786028 accept-ranges=bytes date=mon, 30 apr 2001 12:56:11 gmt etag=w/"02ca57e173c11:95b" content-type=application/octet-stream server=microsoft-iis/5.0 last-modified=mon, 30 apr 2001 12:56:11 gmt
Use breakpoint resume transmission
GET /down.zip HTTP/1.0 User-Agent: NetFox RANGE: bytes=2000070- Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
There is an extra lineRange: bytes=2000070-
This line means to tell the server to down. The zip file is transmitted starting from 2000070 bytes, and the previous bytes do not need to be transmitted. The complete format of
Range is:
Range: bytes=startOffset-targetOffset/sum [表示从startOffset读取,一直读取到targetOffset位置,读取总数为sum直接] Range: bytes=startOffset-targetOffset [字节总数也可以去掉]
After the server receives this request, the information returned is as follows:
HTTP/1.1 206 Partial Content content-length=106786028 content-range=bytes 2000070-106786027/106786028 date=mon, 30 apr 2001 12:55:20 gmt etag=w/"02ca57e173c11:95b" content-type=application/octet-stream server=microsoft-iis/5.0 last-modified=mon, 30 apr 2001 12:55:20 gmt
Compare it with the information returned by the previous server, and you will find that an extra line has been added. :
Content-Range=bytes 2000070-106786027/106786028
The returned code has also been changed to 206 instead of 200.
HTTP/1.1 206 Partial Content
After knowing the above principles, you can program the breakpoint resume download.
2. PHP implementation
/** php下载类,支持断点续传 * download: 下载文件 * setSpeed: 设置下载速度 * getRange: 获取header中Range */ class FileDownload{ /** 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='', $reload=false){ $fp = @fopen($file, 'rb'); if($fp){ if($name==''){ $name = basename($file); } $header_array = get_headers($file, true); //var_dump($header_array);die; // 下载本地文件,获取文件大小 if (!$header_array) { $file_size = filesize($file); } else { $file_size = $header_array['Content-Length']; } $ranges = $this->getRange($file_size); $ua = $_SERVER["HTTP_USER_AGENT"];//判断是什么类型浏览器 header('cache-control:public'); header('content-type:application/octet-stream'); $encoded_filename = urlencode($name); $encoded_filename = str_replace("+", "%20", $encoded_filename); //解决下载文件名乱码 if (preg_match("/MSIE/", $ua) || preg_match("/Trident/", $ua) ){ header('Content-Disposition: attachment; filename="' .$encoded_filename . '"'); } else if (preg_match("/Firefox/", $ua)) { header('Content-Disposition: attachment; filename*="utf8\'\'' . $name . '"'); }else if (preg_match("/Chrome/", $ua)) { header('Content-Disposition: attachment; filename="' . $encoded_filename . '"'); } else { header('Content-Disposition: attachment; filename="' . $name . '"'); } //header('Content-Disposition: attachment; filename="' . $name . '"'); if($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'])); // range信息 header(sprintf('content-range:bytes %s-%s/%s', $ranges['start'], $ranges['end'], $file_size)); //file_put_contents('test.log',sprintf('content-length:%u',$ranges['end']-$ranges['start']),FILE_APPEND); // fp指针跳到断点位置 fseek($fp, sprintf('%u', $ranges['start'])); }else{ file_put_contents('test.log','2222',FILE_APPEND); header('HTTP/1.1 200 OK'); header('content-length:'.$file_size); } while(!feof($fp)){ //echo fread($fp, round($this->_speed*1024,0)); //echo fread($fp, $file_size); echo fread($fp, 4096); ob_flush(); } ($fp!=null) && fclose($fp); }else{ return ''; } } /** 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){ //file_put_contents('range.log', json_encode($_SERVER), FILE_APPEND); if(isset($_SERVER['HTTP_RANGE']) && !empty($_SERVER['HTTP_RANGE'])){ $range = $_SERVER['HTTP_RANGE']; $range = preg_replace('/[\s|,].*/', '', $range); $range = explode('-', substr($range, 6)); if(count($range)<2){ $range[1] = $file_size; } $range = array_combine(array('start','end'), $range); if(empty($range['start'])){ $range['start'] = 0; } if(empty($range['end'])){ $range['end'] = $file_size; } return $range; } return null; } } $obj = new FileDownload(); $obj->download('http://down.golaravel.com/laravel/laravel-master.zip','', true);
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php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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