src: minor refactoring to StreamBase writes

Instead of having per-request callbacks, always call a callback
on the `StreamBase` instance itself for `WriteWrap` and `ShutdownWrap`.

This makes `WriteWrap` cleanup consistent for all stream classes,
since the after-write callback is always the same now.

If special handling is needed for writes that happen to a sub-class,
`AfterWrite` can be overridden by that class, rather than that
class providing its own callback (e.g. updating the write
queue size for libuv streams).

If special handling is needed for writes that happen on another
stream instance, the existing `after_write_cb()` callback
is used for that (e.g. custom code after writing to the
transport from a TLS stream).

As a nice bonus, this also makes `WriteWrap` and `ShutdownWrap`
instances slightly smaller.

PR-URL: #17564
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: addaleax

src/js_stream.cc

@@ -176,7 +176,7 @@ void JSStream::DoAfterWrite(const FunctionCallbackInfo<Value>& args) {
   ASSIGN_OR_RETURN_UNWRAP(&wrap, args.Holder());
   ASSIGN_OR_RETURN_UNWRAP(&w, args[0].As<Object>());
 
-  wrap->OnAfterWrite(w);
+  w->Done(0);
 }
 
 

src/node_http2.cc

@@ -975,9 +975,6 @@ inline void Http2Session::SetChunksSinceLastWrite(size_t n) {
 
 WriteWrap* Http2Session::AllocateSend() {
   HandleScope scope(env()->isolate());
-  auto AfterWrite = [](WriteWrap* req, int status) {
-    req->Dispose();
-  };
   Local<Object> obj =
       env()->write_wrap_constructor_function()
           ->NewInstance(env()->context()).ToLocalChecked();
@@ -987,7 +984,7 @@ WriteWrap* Http2Session::AllocateSend() {
           session(),
           NGHTTP2_SETTINGS_MAX_FRAME_SIZE);
   // Max frame size + 9 bytes for the header
-  return WriteWrap::New(env(), obj, stream_, AfterWrite, size + 9);
+  return WriteWrap::New(env(), obj, stream_, size + 9);
 }
 
 void Http2Session::Send(WriteWrap* req, char* buf, size_t length) {

src/stream_base-inl.h

@@ -143,15 +143,19 @@ void StreamBase::JSMethod(const FunctionCallbackInfo<Value>& args) {
 }
 
 
+inline void ShutdownWrap::OnDone(int status) {
+  stream()->AfterShutdown(this, status);
+}
+
+
 WriteWrap* WriteWrap::New(Environment* env,
                           Local<Object> obj,
                           StreamBase* wrap,
-                          DoneCb cb,
                           size_t extra) {
   size_t storage_size = ROUND_UP(sizeof(WriteWrap), kAlignSize) + extra;
   char* storage = new char[storage_size];
 
-  return new(storage) WriteWrap(env, obj, wrap, cb, storage_size);
+  return new(storage) WriteWrap(env, obj, wrap, storage_size);
 }
 
 
@@ -171,6 +175,10 @@ size_t WriteWrap::ExtraSize() const {
   return storage_size_ - ROUND_UP(sizeof(*this), kAlignSize);
 }
 
+inline void WriteWrap::OnDone(int status) {
+  stream()->AfterWrite(this, status);
+}
+
 }  // namespace node
 
 #endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

src/stream_base.cc

@@ -55,8 +55,7 @@ int StreamBase::Shutdown(const FunctionCallbackInfo<Value>& args) {
   env->set_init_trigger_async_id(wrap->get_async_id());
   ShutdownWrap* req_wrap = new ShutdownWrap(env,
                                             req_wrap_obj,
-                                            this,
-                                            AfterShutdown);
+                                            this);
 
   int err = DoShutdown(req_wrap);
   if (err)
@@ -66,7 +65,6 @@ int StreamBase::Shutdown(const FunctionCallbackInfo<Value>& args) {
 
 
 void StreamBase::AfterShutdown(ShutdownWrap* req_wrap, int status) {
-  StreamBase* wrap = req_wrap->wrap();
   Environment* env = req_wrap->env();
 
   // The wrap and request objects should still be there.
@@ -78,7 +76,7 @@ void StreamBase::AfterShutdown(ShutdownWrap* req_wrap, int status) {
   Local<Object> req_wrap_obj = req_wrap->object();
   Local<Value> argv[3] = {
     Integer::New(env->isolate(), status),
-    wrap->GetObject(),
+    GetObject(),
     req_wrap_obj
   };
 
@@ -158,7 +156,7 @@ int StreamBase::Writev(const FunctionCallbackInfo<Value>& args) {
   wrap = GetAsyncWrap();
   CHECK_NE(wrap, nullptr);
   env->set_init_trigger_async_id(wrap->get_async_id());
-  req_wrap = WriteWrap::New(env, req_wrap_obj, this, AfterWrite, storage_size);
+  req_wrap = WriteWrap::New(env, req_wrap_obj, this, storage_size);
 
   offset = 0;
   if (!all_buffers) {
@@ -248,7 +246,7 @@ int StreamBase::WriteBuffer(const FunctionCallbackInfo<Value>& args) {
   if (wrap != nullptr)
     env->set_init_trigger_async_id(wrap->get_async_id());
   // Allocate, or write rest
-  req_wrap = WriteWrap::New(env, req_wrap_obj, this, AfterWrite);
+  req_wrap = WriteWrap::New(env, req_wrap_obj, this);
 
   err = DoWrite(req_wrap, bufs, count, nullptr);
   req_wrap_obj->Set(env->async(), True(env->isolate()));
@@ -332,7 +330,7 @@ int StreamBase::WriteString(const FunctionCallbackInfo<Value>& args) {
   wrap = GetAsyncWrap();
   if (wrap != nullptr)
     env->set_init_trigger_async_id(wrap->get_async_id());
-  req_wrap = WriteWrap::New(env, req_wrap_obj, this, AfterWrite, storage_size);
+  req_wrap = WriteWrap::New(env, req_wrap_obj, this, storage_size);
 
   data = req_wrap->Extra();
 
@@ -393,7 +391,6 @@ int StreamBase::WriteString(const FunctionCallbackInfo<Value>& args) {
 
 
 void StreamBase::AfterWrite(WriteWrap* req_wrap, int status) {
-  StreamBase* wrap = req_wrap->wrap();
   Environment* env = req_wrap->env();
 
   HandleScope handle_scope(env->isolate());
@@ -405,19 +402,19 @@ void StreamBase::AfterWrite(WriteWrap* req_wrap, int status) {
   // Unref handle property
   Local<Object> req_wrap_obj = req_wrap->object();
   req_wrap_obj->Delete(env->context(), env->handle_string()).FromJust();
-  wrap->OnAfterWrite(req_wrap);
+  OnAfterWrite(req_wrap, status);
 
   Local<Value> argv[] = {
     Integer::New(env->isolate(), status),
-    wrap->GetObject(),
+    GetObject(),
     req_wrap_obj,
     Undefined(env->isolate())
   };
 
-  const char* msg = wrap->Error();
+  const char* msg = Error();
   if (msg != nullptr) {
     argv[3] = OneByteString(env->isolate(), msg);
-    wrap->ClearError();
+    ClearError();
   }
 
   if (req_wrap_obj->Has(env->context(), env->oncomplete_string()).FromJust())

src/stream_base.h

@@ -16,39 +16,37 @@ namespace node {
 // Forward declarations
 class StreamBase;
 
-template <class Req>
+template<typename Base>
 class StreamReq {
  public:
-  typedef void (*DoneCb)(Req* req, int status);
-
-  explicit StreamReq(DoneCb cb) : cb_(cb) {
+  explicit StreamReq(StreamBase* stream) : stream_(stream) {
   }
 
   inline void Done(int status, const char* error_str = nullptr) {
-    Req* req = static_cast<Req*>(this);
+    Base* req = static_cast<Base*>(this);
     Environment* env = req->env();
     if (error_str != nullptr) {
       req->object()->Set(env->error_string(),
                          OneByteString(env->isolate(), error_str));
     }
 
-    cb_(req, status);
+    req->OnDone(status);
   }
 
+  inline StreamBase* stream() const { return stream_; }
+
  private:
-  DoneCb cb_;
+  StreamBase* const stream_;
 };
 
 class ShutdownWrap : public ReqWrap<uv_shutdown_t>,
                      public StreamReq<ShutdownWrap> {
  public:
   ShutdownWrap(Environment* env,
                v8::Local<v8::Object> req_wrap_obj,
-               StreamBase* wrap,
-               DoneCb cb)
+               StreamBase* stream)
       : ReqWrap(env, req_wrap_obj, AsyncWrap::PROVIDER_SHUTDOWNWRAP),
-        StreamReq<ShutdownWrap>(cb),
-        wrap_(wrap) {
+        StreamReq<ShutdownWrap>(stream) {
     Wrap(req_wrap_obj, this);
   }
 
@@ -60,27 +58,22 @@ class ShutdownWrap : public ReqWrap<uv_shutdown_t>,
     return ContainerOf(&ShutdownWrap::req_, req);
   }
 
-  inline StreamBase* wrap() const { return wrap_; }
   size_t self_size() const override { return sizeof(*this); }
 
- private:
-  StreamBase* const wrap_;
+  inline void OnDone(int status);  // Just calls stream()->AfterShutdown()
 };
 
-class WriteWrap: public ReqWrap<uv_write_t>,
-                 public StreamReq<WriteWrap> {
+class WriteWrap : public ReqWrap<uv_write_t>,
+                  public StreamReq<WriteWrap> {
  public:
   static inline WriteWrap* New(Environment* env,
                                v8::Local<v8::Object> obj,
-                               StreamBase* wrap,
-                               DoneCb cb,
+                               StreamBase* stream,
                                size_t extra = 0);
   inline void Dispose();
   inline char* Extra(size_t offset = 0);
   inline size_t ExtraSize() const;
 
-  inline StreamBase* wrap() const { return wrap_; }
-
   size_t self_size() const override { return storage_size_; }
 
   static WriteWrap* from_req(uv_write_t* req) {
@@ -91,24 +84,22 @@ class WriteWrap: public ReqWrap<uv_write_t>,
 
   WriteWrap(Environment* env,
             v8::Local<v8::Object> obj,
-            StreamBase* wrap,
-            DoneCb cb)
+            StreamBase* stream)
       : ReqWrap(env, obj, AsyncWrap::PROVIDER_WRITEWRAP),
-        StreamReq<WriteWrap>(cb),
-        wrap_(wrap),
+        StreamReq<WriteWrap>(stream),
         storage_size_(0) {
     Wrap(obj, this);
   }
 
+  inline void OnDone(int status);  // Just calls stream()->AfterWrite()
+
  protected:
   WriteWrap(Environment* env,
             v8::Local<v8::Object> obj,
-            StreamBase* wrap,
-            DoneCb cb,
+            StreamBase* stream,
             size_t storage_size)
       : ReqWrap(env, obj, AsyncWrap::PROVIDER_WRITEWRAP),
-        StreamReq<WriteWrap>(cb),
-        wrap_(wrap),
+        StreamReq<WriteWrap>(stream),
         storage_size_(storage_size) {
     Wrap(obj, this);
   }
@@ -129,7 +120,6 @@ class WriteWrap: public ReqWrap<uv_write_t>,
   // WriteWrap. Ensure this never happens.
   void operator delete(void* ptr) { UNREACHABLE(); }
 
-  StreamBase* const wrap_;
   const size_t storage_size_;
 };
 
@@ -151,7 +141,7 @@ class StreamResource {
     void* ctx;
   };
 
-  typedef void (*AfterWriteCb)(WriteWrap* w, void* ctx);
+  typedef void (*AfterWriteCb)(WriteWrap* w, int status, void* ctx);
   typedef void (*AllocCb)(size_t size, uv_buf_t* buf, void* ctx);
   typedef void (*ReadCb)(ssize_t nread,
                          const uv_buf_t* buf,
@@ -176,9 +166,9 @@ class StreamResource {
   virtual void ClearError();
 
   // Events
-  inline void OnAfterWrite(WriteWrap* w) {
+  inline void OnAfterWrite(WriteWrap* w, int status) {
     if (!after_write_cb_.is_empty())
-      after_write_cb_.fn(w, after_write_cb_.ctx);
+      after_write_cb_.fn(w, status, after_write_cb_.ctx);
   }
 
   inline void OnAlloc(size_t size, uv_buf_t* buf) {
@@ -208,14 +198,12 @@ class StreamResource {
   inline Callback<ReadCb> read_cb() { return read_cb_; }
   inline Callback<DestructCb> destruct_cb() { return destruct_cb_; }
 
- private:
+ protected:
   Callback<AfterWriteCb> after_write_cb_;
   Callback<AllocCb> alloc_cb_;
   Callback<ReadCb> read_cb_;
   Callback<DestructCb> destruct_cb_;
   uint64_t bytes_read_;
-
-  friend class StreamBase;
 };
 
 class StreamBase : public StreamResource {
@@ -253,6 +241,10 @@ class StreamBase : public StreamResource {
                 v8::Local<v8::Object> buf,
                 v8::Local<v8::Object> handle);
 
+  // These are called by the respective {Write,Shutdown}Wrap class.
+  virtual void AfterShutdown(ShutdownWrap* req, int status);
+  virtual void AfterWrite(WriteWrap* req, int status);
+
  protected:
   explicit StreamBase(Environment* env) : env_(env), consumed_(false) {
   }
@@ -263,10 +255,6 @@ class StreamBase : public StreamResource {
   virtual AsyncWrap* GetAsyncWrap() = 0;
   virtual v8::Local<v8::Object> GetObject();
 
-  // Libuv callbacks
-  static void AfterShutdown(ShutdownWrap* req, int status);
-  static void AfterWrite(WriteWrap* req, int status);
-
   // JS Methods
   int ReadStart(const v8::FunctionCallbackInfo<v8::Value>& args);
   int ReadStop(const v8::FunctionCallbackInfo<v8::Value>& args);

src/stream_wrap.cc

@@ -91,7 +91,6 @@ LibuvStreamWrap::LibuvStreamWrap(Environment* env,
                  provider),
       StreamBase(env),
       stream_(stream) {
-  set_after_write_cb({ OnAfterWriteImpl, this });
   set_alloc_cb({ OnAllocImpl, this });
   set_read_cb({ OnReadImpl, this });
 }
@@ -293,13 +292,13 @@ void LibuvStreamWrap::SetBlocking(const FunctionCallbackInfo<Value>& args) {
 
 int LibuvStreamWrap::DoShutdown(ShutdownWrap* req_wrap) {
   int err;
-  err = uv_shutdown(req_wrap->req(), stream(), AfterShutdown);
+  err = uv_shutdown(req_wrap->req(), stream(), AfterUvShutdown);
   req_wrap->Dispatched();
   return err;
 }
 
 
-void LibuvStreamWrap::AfterShutdown(uv_shutdown_t* req, int status) {
+void LibuvStreamWrap::AfterUvShutdown(uv_shutdown_t* req, int status) {
   ShutdownWrap* req_wrap = ShutdownWrap::from_req(req);
   CHECK_NE(req_wrap, nullptr);
   HandleScope scope(req_wrap->env()->isolate());
@@ -354,9 +353,9 @@ int LibuvStreamWrap::DoWrite(WriteWrap* w,
                         uv_stream_t* send_handle) {
   int r;
   if (send_handle == nullptr) {
-    r = uv_write(w->req(), stream(), bufs, count, AfterWrite);
+    r = uv_write(w->req(), stream(), bufs, count, AfterUvWrite);
   } else {
-    r = uv_write2(w->req(), stream(), bufs, count, send_handle, AfterWrite);
+    r = uv_write2(w->req(), stream(), bufs, count, send_handle, AfterUvWrite);
   }
 
   if (!r) {
@@ -377,7 +376,7 @@ int LibuvStreamWrap::DoWrite(WriteWrap* w,
 }
 
 
-void LibuvStreamWrap::AfterWrite(uv_write_t* req, int status) {
+void LibuvStreamWrap::AfterUvWrite(uv_write_t* req, int status) {
   WriteWrap* req_wrap = WriteWrap::from_req(req);
   CHECK_NE(req_wrap, nullptr);
   HandleScope scope(req_wrap->env()->isolate());
@@ -386,9 +385,9 @@ void LibuvStreamWrap::AfterWrite(uv_write_t* req, int status) {
 }
 
 
-void LibuvStreamWrap::OnAfterWriteImpl(WriteWrap* w, void* ctx) {
-  LibuvStreamWrap* wrap = static_cast<LibuvStreamWrap*>(ctx);
-  wrap->UpdateWriteQueueSize();
+void LibuvStreamWrap::AfterWrite(WriteWrap* w, int status) {
+  StreamBase::AfterWrite(w, status);
+  UpdateWriteQueueSize();
 }
 
 }  // namespace node