src: add AliasedStruct utility

For http2 (and eventually QUIC) we have a struct that is backed
by a v8::BackingStore and exposed to the JavaScript side as an
ArrayBuffer and TypedArray. This is similar to AliasedBuffer
except that it is fronted by a struct on the C++ side.

```c++
struct foo {
  uint32_t ex1;
  uint32_t ex2;
};

AliasedStruct<foo> foo_;

foo_->ex1 = 1;
foo_->ex2 = 2;

foo_.GetArrayBuffer();
```

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/32778
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/node_http2.h b/src/node_http2.h
index f9a0cae85ff..1e5f99acfac 100644
--- a/src/node_http2.h
+++ b/src/node_http2.h
@@ -7,6 +7,7 @@
 #include <cstdint>
 #include "nghttp2/nghttp2.h"
 
+#include "aliased_struct.h"
 #include "node_http2_state.h"
 #include "node_http_common.h"
 #include "node_mem.h"
@@ -823,8 +824,7 @@ class Http2Session : public AsyncWrap,
   Nghttp2SessionPointer session_;
 
   // JS-accessible numeric fields, as indexed by SessionUint8Fields.
-  SessionJSFields* js_fields_ = nullptr;
-  std::shared_ptr<v8::BackingStore> js_fields_store_;
+  AliasedStruct<SessionJSFields> js_fields_;
 
   // The session type: client or server
   nghttp2_session_type session_type_;