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: https://github.com/nodejs/node/pull/18676
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/req_wrap.h b/src/req_wrap.h
index ddd0840aad..656be38dce 100644
--- a/src/req_wrap.h
+++ b/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();