quic: apply multiple quic performance and packet handling improvements

.gitignore

@@ -31,6 +31,7 @@
 /tags
 /tags.*
 /doc/api.xml
+/docs/
 /node
 /node_g
 /gon-config.json

doc/api/quic.md

@@ -2094,6 +2094,20 @@ added: v23.8.0
 
 * Type: {bigint}
 
+### `streamStats.bytesAccumulated`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* Type: {bigint}
+
+The current number of bytes sitting in the stream's receive accumulation
+buffer, awaiting delivery to the application. A value near zero indicates
+the reader is keeping up with incoming data. A value near the stream's
+flow control window indicates the application is not consuming data fast
+enough.
+
 ### `streamStats.bytesReceived`
 
 <!-- YAML
@@ -2142,6 +2156,20 @@ added: v23.8.0
 
 * Type: {bigint}
 
+### `streamStats.maxBytesAccumulated`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* Type: {bigint}
+
+The peak number of bytes that were accumulated in the stream's receive
+buffer at any point during the stream's lifetime. This value only
+increases monotonically. It is useful for diagnosing whether a stream
+experienced backpressure episodes and whether the accumulation buffer
+sizing is appropriate for the workload.
+
 ### `streamStats.maxOffset`
 
 <!-- YAML

lib/internal/fs/promises.js

@@ -178,6 +178,12 @@ function handleErrorFromBinding(error) {
 }
 
 class FileHandle extends EventEmitter {
+  #brandCheck = undefined;
+
+  static isFileHandle(value) {
+    return (value != null && typeof value === 'object' && #brandCheck in value);
+  }
+
   /**
    * @param {InternalFSBinding.FileHandle | undefined} filehandle
    */