fix: yield single buffers (libp2p#233)

* fix: yield single buffers

Messages are serialized to multiple buffers, intsead of yield each
buffer one by one, create single buffers that contain the whole
serialized message. This greatly improves transport performance as
writing one big buffer is a lot faster than writing lots of small
buffers to network sockets etc.

Before:

```
testing 0.40.x-mplex
sender 3276811 messages 17 invocations
sender 6553636 bufs 17 b 24197 ms
105 MB in 32 B chunks in 24170ms
```

After:

```
testing 0.40.x-mplex
sender 3276811 messages 1638408 invocations
1638411 bufs 68 b 8626 ms
105 MB in 32 B chunks in 8611ms
```

* chore: update comment

src/encode.ts

@@ -1,5 +1,6 @@
 import type { Source } from 'it-stream-types'
 import varint from 'varint'
+import { Uint8ArrayList } from 'uint8arraylist'
 import { allocUnsafe } from './alloc-unsafe.js'
 import { Message, MessageTypes } from './message-types.js'
 
@@ -15,9 +16,9 @@ class Encoder {
   }
 
   /**
-   * Encodes the given message and returns it and its header
+   * Encodes the given message and adds it to the passed list
    */
-  write (msg: Message): Uint8Array[] {
+  write (msg: Message, list: Uint8ArrayList): void {
     const pool = this._pool
     let offset = this._poolOffset
 
@@ -41,16 +42,11 @@ class Encoder {
       this._poolOffset = offset
     }
 
+    list.append(header)
+
     if ((msg.type === MessageTypes.NEW_STREAM || msg.type === MessageTypes.MESSAGE_INITIATOR || msg.type === MessageTypes.MESSAGE_RECEIVER) && msg.data != null) {
-      return [
-        header,
-        ...(msg.data instanceof Uint8Array ? [msg.data] : msg.data)
-      ]
+      list.append(msg.data)
     }
-
-    return [
-      header
-    ]
   }
 }
 
@@ -61,12 +57,16 @@ const encoder = new Encoder()
  */
 export async function * encode (source: Source<Message | Message[]>) {
   for await (const msg of source) {
+    const list = new Uint8ArrayList()
+
     if (Array.isArray(msg)) {
       for (const m of msg) {
-        yield * encoder.write(m)
+        encoder.write(m, list)
       }
     } else {
-      yield * encoder.write(msg)
+      encoder.write(msg, list)
     }
+
+    yield list.subarray()
   }
 }

src/mplex.ts

@@ -155,7 +155,7 @@ export class MplexStreamMuxer implements StreamMuxer {
   _newStream (options: { id: number, name: string, type: 'initiator' | 'receiver', registry: Map<number, MplexStream> }) {
     const { id, name, type, registry } = options
 
-    log('new %s stream %s %s', type, id)
+    log('new %s stream %s', type, id)
 
     if (type === 'initiator' && this._streams.initiators.size === (this._init.maxOutboundStreams ?? MAX_STREAMS_OUTBOUND_STREAMS_PER_CONNECTION)) {
       throw errCode(new Error('Too many outbound streams open'), 'ERR_TOO_MANY_OUTBOUND_STREAMS')

src/stream.ts

@@ -171,24 +171,15 @@ export function createStream (options: Options): MplexStream {
           send({ id, type: InitiatorMessageTypes.NEW_STREAM, data: new Uint8ArrayList(uint8ArrayFromString(streamName)) })
         }
 
-        const uint8ArrayList = new Uint8ArrayList()
-
-        for await (const data of source) {
-          if (data.length <= maxMsgSize) {
-            send({ id, type: Types.MESSAGE, data: data instanceof Uint8ArrayList ? data : new Uint8ArrayList(data) })
-          } else {
-            uint8ArrayList.append(data)
-
-            while (uint8ArrayList.length !== 0) {
-              // eslint-disable-next-line max-depth
-              if (uint8ArrayList.length <= maxMsgSize) {
-                send({ id, type: Types.MESSAGE, data: uint8ArrayList.sublist() })
-                uint8ArrayList.consume(uint8ArrayList.length)
-                break
-              }
-              send({ id, type: Types.MESSAGE, data: uint8ArrayList.sublist(0, maxMsgSize) })
-              uint8ArrayList.consume(maxMsgSize)
+        for await (let data of source) {
+          while (data.length > 0) {
+            if (data.length <= maxMsgSize) {
+              send({ id, type: Types.MESSAGE, data: data instanceof Uint8Array ? new Uint8ArrayList(data) : data })
+              break
             }
+            data = data instanceof Uint8Array ? new Uint8ArrayList(data) : data
+            send({ id, type: Types.MESSAGE, data: data.sublist(0, maxMsgSize) })
+            data.consume(maxMsgSize)
           }
         }
       } catch (err: any) {