http: add optimized sendFile

Author: ronag

lib/_http_server.js

@@ -88,6 +88,7 @@ const {
   validateObject,
 } = require('internal/validators');
 const Buffer = require('buffer').Buffer;
+const { pipeline } = require('stream');
 const { setInterval, clearInterval } = require('timers');
 let debug = require('internal/util/debuglog').debuglog('http', (fn) => {
   debug = fn;
@@ -225,6 +226,30 @@ function ServerResponse(req) {
 ObjectSetPrototypeOf(ServerResponse.prototype, OutgoingMessage.prototype);
 ObjectSetPrototypeOf(ServerResponse, OutgoingMessage);
 
+ServerResponse.prototype.sendFile = function(file, options, callback) {
+  if (typeof options === 'function') {
+    callback = options;
+    options = null;
+  }
+
+  validateObject(options, 'options', { nullable: true });
+  validateCallback(callback, 'callback');
+
+  const { start, end, highWaterMark } = options ?? {};
+
+  let path
+  let fd
+
+  if (file instanceof FileHandle || Number.isInteger(file)) {
+    fd = file
+  } else {
+    path = file
+  }
+
+  // TODO (perf): Optimize this...
+  pipeline(fs.createReadStream(path, { fd, start, end, highWaterMark }), callback);
+};
+
 ServerResponse.prototype._finish = function _finish() {
   if (this[kServerResponseStatistics] && hasObserver('http')) {
     stopPerf(this, kServerResponseStatistics, {