php 超大文件下载程序[http 缓存协商，Etag标记，断点续传]

php教程 

002 $file_path = './download/download_cn.rar'; 

003   

004 //使用方法 

005 downFile($file_path); 

006   

007 // 服务器文件路径，下载文件名字(默认为服务器文件名)，是否许可用户下载方式(默认可选)，速度限制(默认自动)，文件类型(默认所有) 

008 function downFile($fileName, $fancyName = '', $forceDownload = true, $speedLimit = 0, $contentType = '') {  

009     if (!is_readable($fileName))  

010     {  

011         header("HTTP/1.1 404 Not Found");  

012         return false;  

013     }  

014     

015     $fileStat = stat($fileName);  

016     $lastModified = $fileStat['mtime'];  

017     

018     $md5 = md5($fileStat['mtime'] .'='. $fileStat['ino'] .'='. $fileStat['size']);  

019     $etag = '"' . $md5 . '-' . crc32($md5) . '"';  

020     

021     header('Last-Modified: ' . gmdate("D, d M Y H:i:s", $lastModified) . ' GMT');  

022     header("ETag: $etag");  

023     

024     if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) >= $lastModified)  

025     {  

026         header("HTTP/1.1 304 Not Modified");  

027         return true;  

028     }  

029     

030     if (isset($_SERVER['HTTP_IF_UNMODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_UNMODIFIED_SINCE']) < $lastModified)  

031     {  

032         header("HTTP/1.1 304 Not Modified");  

033         return true;  

034     }  

035     

036     if (isset($_SERVER['HTTP_IF_NONE_MATCH']) &&  $_SERVER['HTTP_IF_NONE_MATCH'] == $etag)  

037     {  

038         header("HTTP/1.1 304 Not Modified");  

039         return true;  

040     }  

041     

042     if ($fancyName == '')  

043     {  

044         $fancyName = basename($fileName);  

045     }  

046     

047     if ($contentType == '')  

048     {  

049         $contentType = 'application/octet-stream';  

050     }  

051     

052     $fileSize = $fileStat['size'];  

053     

054     $contentLength = $fileSize;  

055     $isPartial = false;  

056     

057     if (isset($_SERVER['HTTP_RANGE']))  

058     {  

059         if (preg_match('/^bytes=(d*)-(d*)$/', $_SERVER['HTTP_RANGE'], $matches))  

060         {  

061             $startPos = $matches[1];  

062             $endPos = $matches[2];  

063     

064             if ($startPos == '' && $endPos == '')  

065             {  

066                 return false;  

067             }  

068     

069             if ($startPos == '')  

070             {  

071                 $startPos = $fileSize - $endPos;  

072                 $endPos = $fileSize - 1;  

073             }  

074             else if ($endPos == '')  

075             {  

076                 $endPos = $fileSize - 1;  

077             }  

078     

079             $startPos = $startPos < 0 ? 0 : $startPos;  

080             $endPos = $endPos > $fileSize - 1 ? $fileSize - 1 : $endPos;  

081     

082             $length = $endPos - $startPos + 1;  

083     

084             if ($length < 0)  

085             {  

086                 return false;  

087             }  

088     

089             $contentLength = $length;  

090             $isPartial = true;  

091         }  

092     }  

093     

094     // send headers  

095     if ($isPartial)  

096     {  

097         header('HTTP/1.1 206 Partial Content');  

098         header("Content-Range: bytes $startPos-$endPos/$fileSize");  

099     

100     }  

101     else 

102     {  

103         header("HTTP/1.1 200 OK");  

104         $startPos = 0;  

105         $endPos = $contentLength - 1;  

106     }  

107     

108     header('Pragma: cache');  

109     header('Cache-Control: public, must-revalidate, max-age=0');  

110     header('Accept-Ranges: bytes');  

111     header('Content-type: ' . $contentType);  

112     header('Content-Length: ' . $contentLength);  

113     

114     if ($forceDownload)  

115     {  

116         header('Content-Disposition: attachment; filename="' . rawurlencode($fancyName). '"');  

117     }  

118     

119     header("Content-Transfer-Encoding: binary");  

120     

121     $bufferSize = 2048;  

122     

123     if ($speedLimit != 0)  

124     {  

125         $packetTime = floor($bufferSize * 1000000 / $speedLimit);  

126     }  

127     

128     $bytesSent = 0;  

129     $fp = fopen($fileName, "rb");  

130     fseek($fp, $startPos);  

131     while ($bytesSent < $contentLength && !feof($fp) && connection_status() == 0 )  

132     {  

133         if ($speedLimit != 0)  

134         {  

135             list($usec, $sec) = explode(" ", microtime());  

136             $outputTimeStart = ((float)$usec + (float)$sec);  

137         }  

138     

139         $readBufferSize = $contentLength - $bytesSent < $bufferSize ? $contentLength - $bytesSent : $bufferSize;  

140         $buffer = fread($fp, $readBufferSize);  

141     

142         echo $buffer;  

143     

144         ob_flush();  

145         flush();  

146     

147         $bytesSent += $readBufferSize;  

148     

149         if ($speedLimit != 0)  

150         {  

151             list($usec, $sec) = explode(" ", microtime());  

152             $outputTimeEnd = ((float)$usec + (float)$sec);  

153     

154             $useTime = ((float) $outputTimeEnd - (float) $outputTimeStart) * 1000000;  

155             $sleepTime = round($packetTime - $useTime);  

156             if ($sleepTime > 0)  

157             {  

158                 usleep($sleepTime);  

159             }  

160         }  

161     }  

162     return true;  

163 }  

164 ?>