Skip re-creating DataView in decodeArray

Runtime/src/js-value.ts

@@ -51,12 +51,18 @@ export const decode = (
 // Note:
 // `decodeValues` assumes that the size of RawJSValue is 16.
 export const decodeArray = (ptr: pointer, length: number, memory: Memory) => {
+ // fast path for empty array
+ if (length === 0) { return []; }
+
  let result = [];
+ // It's safe to hold DataView here because WebAssembly.Memory.buffer won't
+ // change within this function.
+ const view = memory.dataView();
  for (let index = 0; index < length; index++) {
  const base = ptr + 16 * index;
- const kind = memory.readUint32(base);
- const payload1 = memory.readUint32(base + 4);
- const payload2 = memory.readFloat64(base + 8);
+ const kind = view.getUint32(base, true);
+ const payload1 = view.getUint32(base + 4, true);
+ const payload2 = view.getFloat64(base + 8, true);
  result.push(decode(kind, payload1, payload2, memory));
  }
  return result;