From 516b4f0ff82c31d325d9d899091ed6165d45c9b1 Mon Sep 17 00:00:00 2001
From: Michael Weimann <michaelw@matrix.org>
Date: Wed, 21 Sep 2022 20:06:05 +0200
Subject: [PATCH] Add array concat util (#9306)

---
 src/audio/VoiceMessageRecording.ts |  6 ++----
 src/utils/arrays.ts                |  9 +++++++++
 test/utils/arrays-test.ts          | 28 ++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/src/audio/VoiceMessageRecording.ts b/src/audio/VoiceMessageRecording.ts
index 39951ff278e..2e101f903a5 100644
--- a/src/audio/VoiceMessageRecording.ts
+++ b/src/audio/VoiceMessageRecording.ts
@@ -18,6 +18,7 @@ import { IEncryptedFile, MatrixClient } from "matrix-js-sdk/src/matrix";
 import { SimpleObservable } from "matrix-widget-api";
 
 import { uploadFile } from "../ContentMessages";
+import { concat } from "../utils/arrays";
 import { IDestroyable } from "../utils/IDestroyable";
 import { Singleflight } from "../utils/Singleflight";
 import { Playback } from "./Playback";
@@ -148,10 +149,7 @@ export class VoiceMessageRecording implements IDestroyable {
 
     private onDataAvailable = (data: ArrayBuffer) => {
         const buf = new Uint8Array(data);
-        const newBuf = new Uint8Array(this.buffer.length + buf.length);
-        newBuf.set(this.buffer, 0);
-        newBuf.set(buf, this.buffer.length);
-        this.buffer = newBuf;
+        this.buffer = concat(this.buffer, buf);
     };
 
     private get audioBuffer(): Uint8Array {
diff --git a/src/utils/arrays.ts b/src/utils/arrays.ts
index a0fddde45cd..b82be21443a 100644
--- a/src/utils/arrays.ts
+++ b/src/utils/arrays.ts
@@ -304,3 +304,12 @@ export class GroupedArray<K, T> {
         return new ArrayUtil(a);
     }
 }
+
+export const concat = (...arrays: Uint8Array[]): Uint8Array => {
+    return arrays.reduce((concatenatedSoFar: Uint8Array, toBeConcatenated: Uint8Array) => {
+        const concatenated = new Uint8Array(concatenatedSoFar.length + toBeConcatenated.length);
+        concatenated.set(concatenatedSoFar, 0);
+        concatenated.set(toBeConcatenated, concatenatedSoFar.length);
+        return concatenated;
+    }, new Uint8Array(0));
+};
diff --git a/test/utils/arrays-test.ts b/test/utils/arrays-test.ts
index 7dabbb2981a..f0cc52e0a99 100644
--- a/test/utils/arrays-test.ts
+++ b/test/utils/arrays-test.ts
@@ -28,6 +28,7 @@ import {
     arrayIntersection,
     ArrayUtil,
     GroupedArray,
+    concat,
 } from "../../src/utils/arrays";
 
 type TestParams = { input: number[], output: number[] };
@@ -375,5 +376,32 @@ describe('arrays', () => {
             expect(result.value).toEqual(output);
         });
     });
+
+    describe("concat", () => {
+        const emptyArray = () => new Uint8Array(0);
+        const array1 = () => new Uint8Array([1, 2, 3]);
+        const array2 = () => new Uint8Array([4, 5, 6]);
+        const array3 = () => new Uint8Array([7, 8, 9]);
+
+        it("should work for empty arrays", () => {
+            expect(concat(emptyArray(), emptyArray())).toEqual(emptyArray());
+        });
+
+        it("should concat an empty and non-empty array", () => {
+            expect(concat(emptyArray(), array1())).toEqual(array1());
+        });
+
+        it("should concat an non-empty and empty array", () => {
+            expect(concat(array1(), emptyArray())).toEqual(array1());
+        });
+
+        it("should concat two arrays", () => {
+            expect(concat(array1(), array2())).toEqual(new Uint8Array([1, 2, 3, 4, 5, 6]));
+        });
+
+        it("should concat three arrays", () => {
+            expect(concat(array1(), array2(), array3())).toEqual(new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8, 9]));
+        });
+    });
 });