Refactor dispatch handling (#2452)

Promise id is now created in core and passed back to JS.

1 files changed, 15 insertions, 2 deletions

diff --git a/core/shared_queue.js b/core/shared_queue.js
index 75f370ce4..b413f011e 100644
--- a/core/shared_queue.js
+++ b/core/shared_queue.js
@@ -151,14 +151,27 @@ SharedQueue Binary Layout
 
   function handleAsyncMsgFromRust(buf) {
     if (buf) {
-      asyncHandler(buf);
+      handleAsyncMsgFromRustInner(buf);
     } else {
       while ((buf = shift()) != null) {
-        asyncHandler(buf);
+        handleAsyncMsgFromRustInner(buf);
       }
     }
   }
 
+  function handleAsyncMsgFromRustInner(buf) {
+    // DataView to extract cmdId value.
+    const dataView = new DataView(buf.buffer, buf.byteOffset, 4);
+    const promiseId = dataView.getInt32(0);
+    // Uint8 buffer view shifted right and shortened 4 bytes to remove cmdId from view window.
+    const bufViewFinal = new Uint8Array(
+      buf.buffer,
+      buf.byteOffset + 4,
+      buf.byteLength - 4
+    );
+    asyncHandler(promiseId, bufViewFinal);
+  }
+
   function dispatch(control, zeroCopy = null) {
     maybeInit();
     // First try to push control to shared.