Piwik\Http::downloadChunk PHP Method

    public static function downloadChunk($url, $outputPath, $isContinuation)
    {
        // make sure file doesn't already exist if we're starting a new download
        if (!$isContinuation && file_exists($outputPath)) {
            throw new Exception(Piwik::translate('General_DownloadFail_FileExists', "'" . $outputPath . "'") . ' ' . Piwik::translate('General_DownloadPleaseRemoveExisting'));
        }
        // if we're starting a download, get the expected file size & save as an option
        $downloadOption = $outputPath . '_expectedDownloadSize';
        if (!$isContinuation) {
            $expectedFileSizeResult = Http::sendHttpRequest($url, $timeout = 300, $userAgent = null, $destinationPath = null, $followDepth = 0, $acceptLanguage = false, $byteRange = false, $getExtendedInfo = true, $httpMethod = 'HEAD');
            $expectedFileSize = 0;
            if (isset($expectedFileSizeResult['headers']['Content-Length'])) {
                $expectedFileSize = (int) $expectedFileSizeResult['headers']['Content-Length'];
            }
            if ($expectedFileSize == 0) {
                Log::info("HEAD request for '%s' failed, got following: %s", $url, print_r($expectedFileSizeResult, true));
                throw new Exception(Piwik::translate('General_DownloadFail_HttpRequestFail'));
            }
            Option::set($downloadOption, $expectedFileSize);
        } else {
            $expectedFileSize = (int) Option::get($downloadOption);
            if ($expectedFileSize === false) {
                // sanity check
                throw new Exception("Trying to continue a download that never started?! That's not supposed to happen...");
            }
        }
        // if existing file is already big enough, then fail so we don't accidentally overwrite
        // existing DB
        $existingSize = file_exists($outputPath) ? filesize($outputPath) : 0;
        if ($existingSize >= $expectedFileSize) {
            throw new Exception(Piwik::translate('General_DownloadFail_FileExistsContinue', "'" . $outputPath . "'") . ' ' . Piwik::translate('General_DownloadPleaseRemoveExisting'));
        }
        // download a chunk of the file
        $result = Http::sendHttpRequest($url, $timeout = 300, $userAgent = null, $destinationPath = null, $followDepth = 0, $acceptLanguage = false, $byteRange = array($existingSize, min($existingSize + 1024 * 1024 - 1, $expectedFileSize)), $getExtendedInfo = true);
        if ($result === false || $result['status'] < 200 || $result['status'] > 299) {
            $result['data'] = self::truncateStr($result['data'], 1024);
            Log::info("Failed to download range '%s-%s' of file from url '%s'. Got result: %s", $byteRange[0], $byteRange[1], $url, print_r($result, true));
            throw new Exception(Piwik::translate('General_DownloadFail_HttpRequestFail'));
        }
        // write chunk to file
        $f = fopen($outputPath, 'ab');
        fwrite($f, $result['data']);
        fclose($f);
        clearstatcache($clear_realpath_cache = true, $outputPath);
        return array('current_size' => filesize($outputPath), 'expected_file_size' => $expectedFileSize);
    }

 /**
  * Starts or continues a download for a missing GeoIP database. A database is missing if
  * it has an update URL configured, but the actual database is not available in the misc
  * directory.
  *
  * Input:
  *   'url' - The URL to download the database from.
  *   'continue' - 1 if we're continuing a download, 0 if we're starting one.
  *
  * Output:
  *   'error' - If an error occurs this describes the error.
  *   'to_download' - The URL of a missing database that should be downloaded next (if any).
  *   'to_download_label' - The label to use w/ the progress bar that describes what we're
  *                         downloading.
  *   'current_size' - Size of the current file on disk.
  *   'expected_file_size' - Size of the completely downloaded file.
  */
 public function downloadMissingGeoIpDb()
 {
     $this->dieIfGeolocationAdminIsDisabled();
     Piwik::checkUserHasSuperUserAccess();
     if ($_SERVER["REQUEST_METHOD"] == "POST") {
         try {
             $this->checkTokenInUrl();
             Json::sendHeaderJSON();
             // based on the database type (provided by the 'key' query param) determine the
             // url & output file name
             $key = Common::getRequestVar('key', null, 'string');
             $url = GeoIPAutoUpdater::getConfiguredUrl($key);
             $ext = GeoIPAutoUpdater::getGeoIPUrlExtension($url);
             $filename = GeoIp::$dbNames[$key][0] . '.' . $ext;
             if (substr($filename, 0, 15) == 'GeoLiteCity.dat') {
                 $filename = 'GeoIPCity.dat' . substr($filename, 15);
             }
             $outputPath = GeoIp::getPathForGeoIpDatabase($filename);
             // download part of the file
             $result = Http::downloadChunk($url, $outputPath, Common::getRequestVar('continue', true, 'int'));
             // if the file is done
             if ($result['current_size'] >= $result['expected_file_size']) {
                 GeoIPAutoUpdater::unzipDownloadedFile($outputPath, $unlink = true);
                 $info = $this->getNextMissingDbUrlInfo();
                 if ($info !== false) {
                     return json_encode($info);
                 }
             }
             return json_encode($result);
         } catch (Exception $ex) {
             return json_encode(array('error' => $ex->getMessage()));
         }
     }
 }