src/v8/src/builtins/typed-array-filter.tq

// Copyright 2019 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

namespace typed_array_filter {
  const kBuiltinName: constexpr string = '%TypedArray%.prototype.filter';

  extern runtime TypedArrayCopyElements(Context, JSTypedArray, Object, Number):
      void;

  // https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.filter
  transitioning javascript builtin TypedArrayPrototypeFilter(
      js-implicit context: Context, receiver: Object)(...arguments): Object {
    // arguments[0] = callback
    // arguments[1] = thisArg
    try {
      // 1. Let O be the this value.
      // 2. Perform ? ValidateTypedArray(O).
      const array: JSTypedArray = Cast<JSTypedArray>(receiver)
          otherwise ThrowTypeError(kNotTypedArray, kBuiltinName);
      const src = typed_array::EnsureAttached(array) otherwise IsDetached;

      // 3. Let len be O.[[ArrayLength]].
      // TODO(v8:4153): Support huge TypedArrays here.
      const len = Cast<Smi>(Convert<Number>(src.length)) otherwise unreachable;

      // 4. If IsCallable(callbackfn) is false, throw a TypeError exception.
      const callbackfn = Cast<Callable>(arguments[0])
          otherwise ThrowTypeError(kCalledNonCallable, arguments[0]);

      // 5. If thisArg is present, let T be thisArg; else let T be undefined.
      const thisArg: Object = arguments[1];

      // 6. Let kept be a new empty List.
      let kept = growable_fixed_array::NewGrowableFixedArray();
      let witness = typed_array::NewAttachedJSTypedArrayWitness(src);

      // 7. Let k be 0.
      // 8. Let captured be 0.
      // 9. Repeat, while k < len
      for (let k: Smi = 0; k < len; k++) {
        witness.Recheck() otherwise IsDetached;

        // a. Let Pk be ! ToString(k).
        // b. Let kValue be ? Get(O, Pk).
        const value: Object = witness.Load(k);

        // c. Let selected be ToBoolean(? Call(callbackfn, T, « kValue, k, O
        // »)).
        const selected: Object =
            Call(context, callbackfn, thisArg, value, k, witness.GetStable());

        // d. If selected is true, then
        //    i. Append kValue to the end of kept.
        //   ii. Increase captured by 1.
        if (BranchIfToBooleanIsTrue(selected)) kept.Push(value);

        // e.Increase k by 1.
      }

      // 10. Let A be ? TypedArraySpeciesCreate(O, captured).
      const lengthSmi = Convert<PositiveSmi>(kept.length);
      const typedArray: JSTypedArray =
          typed_array_createtypedarray::TypedArraySpeciesCreateByLength(
              kBuiltinName, array, lengthSmi);

      // 11. Let n be 0.
      // 12. For each element e of kept, do
      //   a. Perform ! Set(A, ! ToString(n), e, true).
      //   b. Increment n by 1.
      TypedArrayCopyElements(context, typedArray, kept.ToJSArray(), lengthSmi);

      // 13. Return A.
      return typedArray;
    }
    label IsDetached deferred {
      ThrowTypeError(kDetachedOperation, kBuiltinName);
    }
  }
}