Use transferable objects for signing worker communication

Transfer content buffer to worker and signature buffer back to main
thread instead of copying, improving performance for large messages.

Author: mondoreale

packages/sdk/src/signature/SigningService.ts

@@ -5,7 +5,7 @@
  * 
  * The worker is lazily initialized on first use and shared across all MessageSigner instances.
  */
-import { wrap, releaseProxy, type Remote } from 'comlink'
+import { wrap, releaseProxy, transfer, type Remote } from 'comlink'
 import { Lifecycle, scoped } from 'tsyringe'
 import { createSigningWorker } from '@/createSigningWorker'
 import { SigningResult, SigningRequest } from './signingUtils'
@@ -30,7 +30,9 @@ export class SigningService {
     }
 
     async sign(request: SigningRequest): Promise<SigningResult> {
-        return this.getWorkerApi().createSignature(request)
+        return this.getWorkerApi().createSignature(
+            transfer(request, [request.payloadInput.content.buffer])
+        )
     }
 
     destroy(): void {

packages/sdk/src/signature/SigningWorker.ts

@@ -1,4 +1,4 @@
-import { expose } from 'comlink'
+import { expose, transfer } from 'comlink'
 import {
     createSignatureFromData,
     SigningResult,
@@ -9,7 +9,11 @@ const workerApi = {
     createSignature: async (
         request: SigningRequest
     ): Promise<SigningResult> => {
-        return createSignatureFromData(request)
+        const result = await createSignatureFromData(request)
+        if (result.type === 'success') {
+            return transfer(result, [result.signature.buffer])
+        }
+        return result
     },
 }
 

packages/sdk/test/unit/SigningService.test.ts

@@ -26,25 +26,29 @@ describe('SigningService', () => {
         const privateKey = identity.getPrivateKey()
         const publisherId = await identity.getUserId()
 
-        const payloadInput = {
-            messageId: {
-                streamId: toStreamID('test-stream'),
-                streamPartition: 0,
-                timestamp: Date.now(),
-                sequenceNumber: 0,
-                publisherId,
-                msgChainId: 'test-chain'
-            },
-            content: utf8ToBinary(JSON.stringify({ hello: 'world' })),
-            messageType: StreamMessageType.MESSAGE
+        const content = utf8ToBinary(JSON.stringify({ hello: 'world' }))
+        const messageId = {
+            streamId: toStreamID('test-stream'),
+            streamPartition: 0,
+            timestamp: Date.now(),
+            sequenceNumber: 0,
+            publisherId,
+            msgChainId: 'test-chain'
         }
 
         const request: SigningRequest = {
-            payloadInput,
+            payloadInput: {
+                messageId,
+                content,
+                messageType: StreamMessageType.MESSAGE
+            },
             privateKey,
             signatureType: SignatureType.ECDSA_SECP256K1_EVM
         }
 
+        // Copy content before signing since the buffer is transferred to the worker
+        const contentCopy = new Uint8Array(content)
+
         const result = await signingService.sign(request)
 
         if (result.type !== 'success') {
@@ -54,7 +58,11 @@ describe('SigningService', () => {
         expect(result.signature.length).toBeGreaterThan(0)
 
         // Verify the signature is valid by checking it against the payload
-        const payload = createSignaturePayload(payloadInput)
+        const payload = createSignaturePayload({
+            messageId,
+            content: contentCopy,
+            messageType: StreamMessageType.MESSAGE
+        })
         const signingUtil = new EcdsaSecp256k1Evm()
         const isValid = await signingUtil.verifySignature(await identity.getUserIdRaw(), payload, result.signature)
         expect(isValid).toBe(true)