Large file download fails

[jukkakangas]

Only file is only partially downloaded. A possible solution:

diff --git a/src/Q/WebServer.php b/src/Q/WebServer.php
index 7760a3c..cd53ec9 100644
--- a/src/Q/WebServer.php
+++ b/src/Q/WebServer.php
@@ -17,6 +17,55 @@
 class Q_WebServer
 {
 
+	/**
+	 * Write a string to a stream socket in full, looping over partial writes.
+	 *
+	 * PHP's fwrite() on a stream socket (plain TCP or TLS) is NOT guaranteed
+	 * to write the entire buffer in one call, even in blocking mode: once the
+	 * kernel/OpenSSL send buffer fills up, fwrite() returns the number of
+	 * bytes it actually managed to write (which can be far less than
+	 * requested for large buffers, e.g. multi-megabyte response bodies) and
+	 * the remainder is silently dropped by every call site in this file that
+	 * did a single unchecked `@fwrite($client, $largeString)` — truncating
+	 * any response body larger than roughly one send-buffer's worth (in
+	 * practice, a few hundred KB to a few MB depending on the OS/TLS stack).
+	 * This was reproduced with plain HTTP (no TLS involved) on a ~47MB file:
+	 * only the first ~3MB reached the client even though the server logged a
+	 * clean 200 in a few seconds. Every response-writing call site must loop
+	 * until all bytes are written (or the stream errors out) instead of
+	 * trusting a single fwrite() to finish the job.
+	 *
+	 * @method writeAll
+	 * @static
+	 * @param {resource} $stream
+	 * @param {string} $data
+	 * @return {boolean} true if all bytes were written, false on a write error
+	 */
+	static function writeAll($stream, $data)
+	{
+		$length = strlen($data);
+		$written = 0;
+		while ($written < $length) {
+			$chunk = @fwrite($stream, substr($data, $written));
+			if ($chunk === false) {
+				return false;
+			}
+			if ($chunk === 0) {
+				// Stream buffer is temporarily full (non-blocking mode) or the
+				// peer stopped reading; avoid a tight busy-loop and give the
+				// OS a moment before retrying, but bail out if the stream has
+				// gone away in the meantime.
+				if (feof($stream)) {
+					return false;
+				}
+				usleep(1000);
+				continue;
+			}
+			$written += $chunk;
+		}
+		return true;
+	}
+
 	/**
 	 * Search paths for app/user files.
 	 *
@@ -631,7 +680,7 @@ class Q_WebServer
 
 		// Rate limit check
 		if (!self::checkRateLimit($ip)) {
-			@fwrite($client, "HTTP/1.1 429 Too Many Requests\r\n"
+			self::writeAll($client, "HTTP/1.1 429 Too Many Requests\r\n"
 				. "Retry-After: 60\r\nConnection: close\r\nContent-Length: 0\r\n\r\n");
 			@fclose($client);
 			unset(self::$clients[$key], self::$buffers[$key], self::$keepAliveCount[$key],
@@ -1853,7 +1902,7 @@ class Q_WebServer
 					// If streaming already sent headers, just terminate and close
 					if (Q_WebServer_State::isStreaming()
 						&& !empty($parsed['_streamingSent'])) {
-						@fwrite($client, "0\r\n\r\n"); // chunked terminator
+						self::writeAll($client, "0\r\n\r\n"); // chunked terminator
 						@fclose($client);
 						return;
 					}
@@ -2332,7 +2381,7 @@ WORKER;
 		foreach ($extraHeaders as $pair) {
 			$out .= $pair[0] . ': ' . $pair[1] . "\r\n";
 		}
-		@fwrite($client, $out . "\r\n" . $body);
+		self::writeAll($client, $out . "\r\n" . $body);
 
 		self::$lastStatus = $status;
 		return false;
@@ -2396,9 +2445,9 @@ WORKER;
 			self::$lastStatus = 200;
 			self::$lastBytes = $cached['bodyLen'];
 			if ($method === 'HEAD') {
-				@fwrite($client, $cached['head'][$connKey]);
+				self::writeAll($client, $cached['head'][$connKey]);
 			} else {
-				@fwrite($client, $cached['full'][$connKey]);
+				self::writeAll($client, $cached['full'][$connKey]);
 			}
 			return;
 		}
@@ -2449,7 +2498,7 @@ WORKER;
 				. "Connection: $connHeader\r\n\r\n";
 			self::$lastStatus = 200;
 			self::$lastBytes = $preComp['size'];
-			@fwrite($client, $method === 'HEAD' ? $out : $out . file_get_contents($preComp['path']));
+			self::writeAll($client, $method === 'HEAD' ? $out : $out . file_get_contents($preComp['path']));
 			return;
 		}
 
@@ -2479,7 +2528,7 @@ WORKER;
 					. "Connection: $connHeader\r\n\r\n";
 				self::$lastStatus = 200;
 				self::$lastBytes = strlen($body);
-				@fwrite($client, $method === 'HEAD' ? $out : $out . $body);
+				self::writeAll($client, $method === 'HEAD' ? $out : $out . $body);
 				return;
 			}
 		}
@@ -2494,7 +2543,7 @@ WORKER;
 		self::$lastStatus = 200;
 		self::$lastBytes = $size;
 		$headStr = $keepAlive ? $kaHead : $clHead;
-		@fwrite($client, $method === 'HEAD' ? $headStr : $headStr . $body);
+		self::writeAll($client, $method === 'HEAD' ? $headStr : $headStr . $body);
 
 		// Cache if small enough
 		if ($size <= self::$fileCacheMaxFile
@@ -3708,19 +3757,19 @@ HTML;
 			. "\r\nContent-Type: $type\r\nContent-Length: " . strlen($body)
 			. "\r\nConnection: $conn\r\n";
 		foreach ($extra as $k => $v) $out .= "$k: $v\r\n";
-		@fwrite($client, $out . "\r\n" . $body);
+		self::writeAll($client, $out . "\r\n" . $body);
 	}
 
 	static function sendRedirect($client, $loc, $permanent = false) {
 		$code = $permanent ? 301 : 302;
 		$text = $permanent ? 'Moved Permanently' : 'Found';
-		@fwrite($client, "HTTP/1.1 $code $text\r\nLocation: $loc\r\nContent-Length: 0\r\nConnection: close\r\n\r\n");
+		self::writeAll($client, "HTTP/1.1 $code $text\r\nLocation: $loc\r\nContent-Length: 0\r\nConnection: close\r\n\r\n");
 		self::$lastStatus = $code;
 	}
 
 	private static function sendNotModified($client, $etag, $mtime, $keepAlive = false) {
 		$conn = $keepAlive ? 'keep-alive' : 'close';
-		@fwrite($client, "HTTP/1.1 304 Not Modified\r\nETag: $etag\r\n"
+		self::writeAll($client, "HTTP/1.1 304 Not Modified\r\nETag: $etag\r\n"
 			. "Last-Modified: " . gmdate('D, d M Y H:i:s', $mtime) . " GMT\r\n"
 			. "Cache-Control: public, max-age=0, must-revalidate\r\nContent-Length: 0\r\nConnection: $conn\r\n\r\n");
 		self::$lastStatus = 304;