total size of the .zip, default 25000000 // ?delay_ms= spread the body over this many ms, as attachment_csv does // ?type=pptx serve as .pptx with the PowerPoint content type. The // bytes are still a ZIP container, which is what a .pptx // is. Default is a plain .zip. // ?name= override the attachment filename (no extension) set_time_limit(0); $target_size = isset($_GET['size']) ? intval($_GET['size']) : 25000000; $delay_ms = isset($_GET['delay_ms']) ? intval($_GET['delay_ms']) : 0; $is_pptx = (isset($_GET['type']) && $_GET['type'] === 'pptx'); $base_name = isset($_GET['name']) && $_GET['name'] !== '' ? $_GET['name'] : 'Create your PR (v182) - 20250523'; $ext = $is_pptx ? '.pptx' : '.zip'; $download_name = $base_name . $ext; // Name of the single entry inside the archive. $entry_name = 'course/content.txt'; $name_len = strlen($entry_name); // A single stored entry lays out as: // local header (30 + name) + data + central directory (46 + name) + EOCD (22) // so the payload size follows from the total the caller asked for. $overhead = 30 + $name_len + 46 + $name_len + 22; $data_size = $target_size - $overhead; if ($data_size < 1) { $data_size = 1; $target_size = $overhead + 1; } // Deterministic, incompressible-enough filler. Built in one pass; 25 MB costs // a fraction of a second and well under the default memory limit. $row = "course-material-line,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-\n"; $data = str_repeat($row, intdiv($data_size, strlen($row)) + 1); $data = substr($data, 0, $data_size); $crc = crc32($data); // DOS timestamp for the entry. $now = getdate(); $dos_time = ($now['hours'] << 11) | ($now['minutes'] << 5) | ($now['seconds'] >> 1); $dos_date = (($now['year'] - 1980) << 9) | ($now['mon'] << 5) | $now['mday']; // Local file header: signature, version, flags, method=0 (stored), time, date, // crc, compressed size, uncompressed size, name length, extra length. $local = pack('VvvvvvVVVvv', 0x04034b50, 20, 0, 0, $dos_time, $dos_date, $crc, $data_size, $data_size, $name_len, 0) . $entry_name; // Central directory header, then end-of-central-directory. $central = pack('VvvvvvvVVVvvvvvVV', 0x02014b50, 20, 20, 0, 0, $dos_time, $dos_date, $crc, $data_size, $data_size, $name_len, 0, 0, 0, 0, 0, 0) . $entry_name; $eocd = pack('VvvvvVVv', 0x06054b50, 0, 0, 1, 1, strlen($central), strlen($local) + $data_size, 0); $total = strlen($local) + $data_size + strlen($central) + strlen($eocd); header('HTTP/1.1 200 OK'); header('Content-Type: ' . ($is_pptx ? 'application/vnd.openxmlformats-officedocument.presentationml.presentation' : 'application/zip')); // ?nocd=1 omits Content-Disposition entirely, so the response is a download // only because application/zip is not renderable and the name has to be // derived from the URL path. The field log's surrogate-download-requested line // has no filename= field, and that field is printed with if_truthy() -- so // GetSuggestedFilename() was empty there, which is what this reproduces. if (!isset($_GET['nocd']) || !$_GET['nocd']) { header('Content-Disposition: attachment; filename="' . $download_name . '"'); } header('Content-Length: ' . $total); header('Cache-Control: no-cache'); echo $local; if ($delay_ms <= 0) { echo $data; } else { // Same pacing as attachment_csv.php: twenty chunks, evenly spread, so the // transfer occupies the requested wall-clock time. $chunks = 20; $chunk_size = (int)ceil($data_size / $chunks); $chunk_delay_us = intval($delay_ms * 1000 / $chunks); for ($offset = 0; $offset < $data_size; $offset += $chunk_size) { echo substr($data, $offset, $chunk_size); flush(); usleep($chunk_delay_us); } } echo $central; echo $eocd; ?>