Fix TextDecoder for SharedArrayBuffer backed TypedArray (denoland#1940)

js/text_encoding.ts

@@ -356,6 +356,13 @@ export interface TextDecoderOptions {
  ignoreBOM?: false;
 }
 
+type EitherArrayBuffer = SharedArrayBuffer | ArrayBuffer;
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function isEitherArrayBuffer(x: any): x is EitherArrayBuffer {
+ return x instanceof SharedArrayBuffer || x instanceof ArrayBuffer;
+}
+
 export class TextDecoder {
  private _encoding: string;
 
@@ -400,12 +407,14 @@ export class TextDecoder {
  }
 
  let bytes: Uint8Array;
- if (typeof input === "object" && input instanceof ArrayBuffer) {
+ if (input instanceof Uint8Array) {
+ bytes = input;
+ } else if (isEitherArrayBuffer(input)) {
  bytes = new Uint8Array(input);
  } else if (
  typeof input === "object" &&
  "buffer" in input &&
- input.buffer instanceof ArrayBuffer
+ isEitherArrayBuffer(input.buffer)
  ) {
  bytes = new Uint8Array(input.buffer, input.byteOffset, input.byteLength);
  } else {

js/text_encoding_test.ts

@@ -65,3 +65,29 @@ test(function textEncoder2() {
  0xf0, 0x9d, 0x93, 0xbd
  ]);
 });
+
+test(function textDecoderSharedUint8Array() {
+ const ab = new SharedArrayBuffer(6);
+ const dataView = new DataView(ab);
+ const charCodeA = "A".charCodeAt(0);
+ for (let i = 0; i < ab.byteLength; i++) {
+ dataView.setUint8(i, charCodeA + i);
+ }
+ const ui8 = new Uint8Array(ab);
+ const decoder = new TextDecoder();
+ const actual = decoder.decode(ui8);
+ assertEquals(actual, "ABCDEF");
+});
+
+test(function textDecoderSharedInt32Array() {
+ const ab = new SharedArrayBuffer(8);
+ const dataView = new DataView(ab);
+ const charCodeA = "A".charCodeAt(0);
+ for (let i = 0; i < ab.byteLength; i++) {
+ dataView.setUint8(i, charCodeA + i);
+ }
+ const i32 = new Int32Array(ab);
+ const decoder = new TextDecoder();
+ const actual = decoder.decode(i32);
+ assertEquals(actual, "ABCDEFGH");
+});