src: refactor WriteWrap and ShutdownWraps

Encapsulate stream requests more:

- `WriteWrap` and `ShutdownWrap` classes are now tailored to the
  streams on which they are used. In particular, for most streams
  these are now plain `AsyncWrap`s and do not carry the overhead
  of unused libuv request data.
- Provide generic `Write()` and `Shutdown()` methods that wrap
  around the actual implementations, and make *usage* of streams
  easier, rather than implementing; for example, wrap objects
  don’t need to be provided by callers anymore.
- Use `EmitAfterWrite()` and `EmitAfterShutdown()` handlers to
  call the corresponding JS handlers, rather than always trying
  to call them. This makes usage of streams by other C++ code
  easier and leaner.

Also fix up some tests that were previously not actually testing
asynchronicity when the comments indicated that they would.

PR-URL: #18676
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

benchmark/net/tcp-raw-c2s.js

@@ -118,7 +118,7 @@ function client(type, len) {
       fail(err, 'write');
   }
 
-  function afterWrite(err, handle, req) {
+  function afterWrite(err, handle) {
     if (err)
       fail(err, 'write');
 

benchmark/net/tcp-raw-pipe.js

@@ -51,7 +51,7 @@ function main({ dur, len, type }) {
       if (err)
         fail(err, 'write');
 
-      writeReq.oncomplete = function(status, handle, req, err) {
+      writeReq.oncomplete = function(status, handle, err) {
         if (err)
           fail(err, 'write');
       };
@@ -130,7 +130,7 @@ function main({ dur, len, type }) {
       fail(err, 'write');
   }
 
-  function afterWrite(err, handle, req) {
+  function afterWrite(err, handle) {
     if (err)
       fail(err, 'write');
 

benchmark/net/tcp-raw-s2c.js

@@ -74,14 +74,14 @@ function main({ dur, len, type }) {
         fail(err, 'write');
       } else if (!writeReq.async) {
         process.nextTick(function() {
-          afterWrite(null, clientHandle, writeReq);
+          afterWrite(0, clientHandle);
         });
       }
     }
 
-    function afterWrite(status, handle, req, err) {
-      if (err)
-        fail(err, 'write');
+    function afterWrite(status, handle) {
+      if (status)
+        fail(status, 'write');
 
       while (clientHandle.writeQueueSize === 0)
         write();

lib/internal/http2/core.js

@@ -1396,20 +1396,19 @@ function trackWriteState(stream, bytes) {
   session[kHandle].chunksSentSinceLastWrite = 0;
 }
 
-function afterDoStreamWrite(status, handle, req) {
+function afterDoStreamWrite(status, handle) {
   const stream = handle[kOwner];
   const session = stream[kSession];
 
   stream[kUpdateTimer]();
 
-  const { bytes } = req;
+  const { bytes } = this;
   stream[kState].writeQueueSize -= bytes;
 
   if (session !== undefined)
     session[kState].writeQueueSize -= bytes;
-  if (typeof req.callback === 'function')
-    req.callback(null);
-  req.handle = undefined;
+  if (typeof this.callback === 'function')
+    this.callback(null);
 }
 
 function streamOnResume() {

lib/internal/wrap_js_stream.js

@@ -115,9 +115,9 @@ class JSStreamWrap extends Socket {
 
     const handle = this._handle;
 
-    this.stream.end(() => {
-      // Ensure that write was dispatched
-      setImmediate(() => {
+    setImmediate(() => {
+      // Ensure that write is dispatched asynchronously.
+      this.stream.end(() => {
         this.finishShutdown(handle, 0);
       });
     });

lib/net.js

@@ -323,7 +323,7 @@ function onSocketFinish() {
 }
 
 
-function afterShutdown(status, handle, req) {
+function afterShutdown(status, handle) {
   var self = handle.owner;
 
   debug('afterShutdown destroyed=%j', self.destroyed,
@@ -842,12 +842,12 @@ protoGetter('bytesWritten', function bytesWritten() {
 });
 
 
-function afterWrite(status, handle, req, err) {
+function afterWrite(status, handle, err) {
   var self = handle.owner;
   if (self !== process.stderr && self !== process.stdout)
     debug('afterWrite', status);
 
-  if (req.async)
+  if (this.async)
     self[kLastWriteQueueSize] = 0;
 
   // callback may come after call to destroy.
@@ -857,9 +857,9 @@ function afterWrite(status, handle, req, err) {
   }
 
   if (status < 0) {
-    var ex = errnoException(status, 'write', req.error);
+    var ex = errnoException(status, 'write', this.error);
     debug('write failure', ex);
-    self.destroy(ex, req.cb);
+    self.destroy(ex, this.cb);
     return;
   }
 
@@ -868,8 +868,8 @@ function afterWrite(status, handle, req, err) {
   if (self !== process.stderr && self !== process.stdout)
     debug('afterWrite call cb');
 
-  if (req.cb)
-    req.cb.call(undefined);
+  if (this.cb)
+    this.cb.call(undefined);
 }
 
 

src/env.h

@@ -303,6 +303,7 @@ class ModuleWrap;
   V(script_context_constructor_template, v8::FunctionTemplate)                \
   V(script_data_constructor_function, v8::Function)                           \
   V(secure_context_constructor_template, v8::FunctionTemplate)                \
+  V(shutdown_wrap_constructor_function, v8::Function)                         \
   V(tcp_constructor_template, v8::FunctionTemplate)                           \
   V(tick_callback_function, v8::Function)                                     \
   V(tls_wrap_constructor_function, v8::Function)                              \

src/js_stream.cc

@@ -91,8 +91,6 @@ int JSStream::DoShutdown(ShutdownWrap* req_wrap) {
     req_wrap->object()
   };
 
-  req_wrap->Dispatched();
-
   TryCatch try_catch(env()->isolate());
   Local<Value> value;
   int value_int = UV_EPROTO;
@@ -127,8 +125,6 @@ int JSStream::DoWrite(WriteWrap* w,
     bufs_arr
   };
 
-  w->Dispatched();
-
   TryCatch try_catch(env()->isolate());
   Local<Value> value;
   int value_int = UV_EPROTO;
@@ -154,9 +150,8 @@ void JSStream::New(const FunctionCallbackInfo<Value>& args) {
 
 template <class Wrap>
 void JSStream::Finish(const FunctionCallbackInfo<Value>& args) {
-  Wrap* w;
   CHECK(args[0]->IsObject());
-  ASSIGN_OR_RETURN_UNWRAP(&w, args[0].As<Object>());
+  Wrap* w = static_cast<Wrap*>(StreamReq::FromObject(args[0].As<Object>()));
 
   w->Done(args[1]->Int32Value());
 }

src/node_http2.cc

@@ -1552,18 +1552,9 @@ void Http2Session::SendPendingData() {
 
   chunks_sent_since_last_write_++;
 
-  // DoTryWrite may modify both the buffer list start itself and the
-  // base pointers/length of the individual buffers.
-  uv_buf_t* writebufs = *bufs;
-  if (stream_->DoTryWrite(&writebufs, &count) != 0 || count == 0) {
-    // All writes finished synchronously, nothing more to do here.
-    ClearOutgoing(0);
-    return;
-  }
-
-  WriteWrap* req = AllocateSend();
-  if (stream_->DoWrite(req, writebufs, count, nullptr) != 0) {
-    req->Dispose();
+  StreamWriteResult res = underlying_stream()->Write(*bufs, count);
+  if (!res.async) {
+    ClearOutgoing(res.err);
   }
 
   DEBUG_HTTP2SESSION2(this, "wants data in return? %d",
@@ -1649,15 +1640,6 @@ inline void Http2Session::SetChunksSinceLastWrite(size_t n) {
   chunks_sent_since_last_write_ = n;
 }
 
-// Allocates the data buffer used to pass outbound data to the i/o stream.
-WriteWrap* Http2Session::AllocateSend() {
-  HandleScope scope(env()->isolate());
-  Local<Object> obj =
-      env()->write_wrap_constructor_function()
-          ->NewInstance(env()->context()).ToLocalChecked();
-  return WriteWrap::New(env(), obj, static_cast<StreamBase*>(stream_));
-}
-
 // Callback used to receive inbound data from the i/o stream
 void Http2Session::OnStreamRead(ssize_t nread, const uv_buf_t& buf) {
   Http2Scope h2scope(this);
@@ -1833,20 +1815,15 @@ inline void Http2Stream::Close(int32_t code) {
   DEBUG_HTTP2STREAM2(this, "closed with code %d", code);
 }
 
-
-inline void Http2Stream::Shutdown() {
-  CHECK(!this->IsDestroyed());
-  Http2Scope h2scope(this);
-  flags_ |= NGHTTP2_STREAM_FLAG_SHUT;
-  CHECK_NE(nghttp2_session_resume_data(session_->session(), id_),
-           NGHTTP2_ERR_NOMEM);
-  DEBUG_HTTP2STREAM(this, "writable side shutdown");
-}
-
 int Http2Stream::DoShutdown(ShutdownWrap* req_wrap) {
   CHECK(!this->IsDestroyed());
-  req_wrap->Dispatched();
-  Shutdown();
+  {
+    Http2Scope h2scope(this);
+    flags_ |= NGHTTP2_STREAM_FLAG_SHUT;
+    CHECK_NE(nghttp2_session_resume_data(session_->session(), id_),
+             NGHTTP2_ERR_NOMEM);
+    DEBUG_HTTP2STREAM(this, "writable side shutdown");
+  }
   req_wrap->Done(0);
   return 0;
 }
@@ -2038,7 +2015,6 @@ inline int Http2Stream::DoWrite(WriteWrap* req_wrap,
   CHECK_EQ(send_handle, nullptr);
   Http2Scope h2scope(this);
   session_->SetChunksSinceLastWrite();
-  req_wrap->Dispatched();
   if (!IsWritable()) {
     req_wrap->Done(UV_EOF);
     return 0;

src/node_http2.h

@@ -605,9 +605,6 @@ class Http2Stream : public AsyncWrap,
 
   inline void Close(int32_t code);
 
-  // Shutdown the writable side of the stream
-  inline void Shutdown();
-
   // Destroy this stream instance and free all held memory.
   inline void Destroy();
 
@@ -822,6 +819,10 @@ class Http2Session : public AsyncWrap, public StreamListener {
 
   inline void EmitStatistics();
 
+  inline StreamBase* underlying_stream() {
+    return static_cast<StreamBase*>(stream_);
+  }
+
   void Start();
   void Stop();
   void Close(uint32_t code = NGHTTP2_NO_ERROR,
@@ -911,8 +912,6 @@ class Http2Session : public AsyncWrap, public StreamListener {
   template <get_setting fn>
   static void GetSettings(const FunctionCallbackInfo<Value>& args);
 
-  WriteWrap* AllocateSend();
-
   uv_loop_t* event_loop() const {
     return env()->event_loop();
   }

src/req_wrap-inl.h

@@ -33,6 +33,11 @@ void ReqWrap<T>::Dispatched() {
   req_.data = this;
 }
 
+template <typename T>
+ReqWrap<T>* ReqWrap<T>::from_req(T* req) {
+  return ContainerOf(&ReqWrap<T>::req_, req);
+}
+
 }  // namespace node
 
 #endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

src/req_wrap.h

@@ -20,6 +20,8 @@ class ReqWrap : public AsyncWrap {
   inline void Dispatched();  // Call this after the req has been dispatched.
   T* req() { return &req_; }
 
+  static ReqWrap* from_req(T* req);
+
  private:
   friend class Environment;
   friend int GenDebugSymbols();