Implement TypedArray.prototype.toReversed

include/hermes/VM/NativeFunctions.def

@@ -392,6 +392,7 @@ NATIVE_FUNCTION(typedArrayPrototypeSort)
 NATIVE_FUNCTION(typedArrayPrototypeSubarray)
 NATIVE_FUNCTION(typedArrayPrototypeSymbolToStringTag)
 NATIVE_FUNCTION(typedArrayPrototypeToLocaleString)
+NATIVE_FUNCTION(typedArrayPrototypeToReversed)
 NATIVE_FUNCTION(unescape)
 NATIVE_FUNCTION(weakMapConstructor)
 NATIVE_FUNCTION(weakMapPrototypeDelete)

lib/VM/JSLib/TypedArray.cpp

@@ -1746,6 +1746,53 @@ typedArrayPrototypeToLocaleString(void *, Runtime &runtime, NativeArgs args) {
   return HermesValue::encodeStringValue(*builder->getStringPrimitive());
 }
 
+/// ES14.0 23.2.3.32
+CallResult<HermesValue>
+typedArrayPrototypeToReversed(void *, Runtime &runtime, NativeArgs args) {
+  GCScope gcScope{runtime};
+
+  // 2. Perform ? ValidateTypedArray(O).
+  if (JSTypedArrayBase::validateTypedArray(runtime, args.getThisHandle()) ==
+      ExecutionStatus::EXCEPTION) {
+    return ExecutionStatus::EXCEPTION;
+  }
+
+  // 1. Let O be this value
+  auto self = args.vmcastThis<JSTypedArrayBase>();
+
+  // 3. Let len be O.[[ArrayLength]].
+  auto len = self->getLength();
+  auto byteLength = self->getByteLength();
+  auto byteWidth = self->getByteWidth();
+
+  // 4. Let A be ? TypedArrayCreateSameType(O, « 𝔽(len) »).
+  auto aRes = JSTypedArrayBase::allocateSpecies(runtime, self, len);
+  if (LLVM_UNLIKELY(aRes == ExecutionStatus::EXCEPTION)) {
+    return ExecutionStatus::EXCEPTION;
+  }
+  auto A = aRes.getValue();
+
+  // 5. Let k be 0.
+  JSArrayBuffer::size_type k = 0;
+
+  auto dstBlock = A->getBuffer(runtime)->getDataBlock(runtime);
+  auto srcBlock = self->getBuffer(runtime)->getDataBlock(runtime);
+
+  // 6. Repeat, while k < len,
+  while (k < byteLength) {
+    // 6a. Let from be ! ToString(𝔽(length - k - 1)).
+    size_t from = byteLength - k - byteWidth;
+
+    // 6d. Perform ! Set(A, Pk, fromValue, true).
+    memcpy(dstBlock + k, srcBlock + from, byteWidth);
+
+    // 6e. Set k to k + 1.
+    k += byteWidth;
+  }
+
+  return A.getHermesValue();
+}
+
 Handle<JSObject> createTypedArrayBaseConstructor(Runtime &runtime) {
   auto proto = Handle<JSObject>::vmcast(&runtime.typedArrayBasePrototype);
 
@@ -2044,6 +2091,14 @@ Handle<JSObject> createTypedArrayBaseConstructor(Runtime &runtime) {
       typedArrayPrototypeToLocaleString,
       0);
 
+  defineMethod(
+      runtime,
+      proto,
+      Predefined::getSymbolID(Predefined::toReversed),
+      nullptr,
+      typedArrayPrototypeToReversed,
+      0);
+
   // TypedArrayBase.xxx
   defineMethod(
       runtime,

test/hermes/TypedArray.js

@@ -1438,6 +1438,16 @@ cons.forEach(function(TypedArray) {
 });
 /// @}
 
+/// @name TypedArray.prototype.toReversed
+/// @{
+cons.forEach(function(TypedArray) {
+  var arr = new TypedArray([ 0, 1, 2, 3 ]);
+
+  assert.arrayEqual(arr.toReversed(), [ 3, 2, 1, 0 ]);
+  assert.arrayEqual(new TypedArray([]).toReversed(), []);
+});
+/// @}
+
 /// @name Exception cases
 /// @{