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// Copyright 2022 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 array {
transitioning macro TryFastPackedArrayWith(implicit context: Context)(
receiver: JSReceiver, len: Number, actualIndex: Number,
value: JSAny): JSArray labels Slow {
// Array#with does not preserve holes and always creates packed Arrays. Holes
// in the source array-like are treated like any other element and the value
// is computed with Get. So, there are only fast paths for packed elements.
const array: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
if (IsFastPackedElementsKind(array.map.elements_kind)) {
const lenSmi = Cast<Smi>(len) otherwise Slow;
// It is possible that the index coercion shrunk the source array, in which
// case go to the slow case.
if (lenSmi > array.length) goto Slow;
// Steps 7-9 done by copying and overriding the value at index.
const copy = ExtractFastJSArray(context, array, 0, lenSmi);
FastCreateDataProperty(copy, actualIndex, value);
// 10. Return A.
return copy;
}
goto Slow;
}
transitioning builtin GenericArrayWith(
context: Context, receiver: JSReceiver, len: Number, actualIndex: Number,
value: JSAny): JSArray {
// 7. Let A be ? ArrayCreate(𝔽(len)).
const copy = ArrayCreate(len);
// 8. Let k be 0.
let k: Number = 0;
// 9. Repeat, while k < len,
while (k < len) {
// a. Let Pk be ! ToString(𝔽(k)).
// b. If k is actualIndex, let fromValue be value.
// c. Else, let fromValue be ? Get(O, Pk).
const fromValue = k == actualIndex ? value : GetProperty(receiver, k);
// d. Perform ! CreateDataPropertyOrThrow(A, Pk, fromValue).
FastCreateDataProperty(copy, k, fromValue);
// e. Set k to k + 1.
++k;
}
// 10. Return A.
return copy;
}
// https://tc39.es/proposal-change-array-by-copy/#sec-array.prototype.with
transitioning javascript builtin ArrayPrototypeWith(
js-implicit context: NativeContext, receiver: JSAny)(...arguments): JSAny {
const index = arguments[0];
const value = arguments[1];
// 1. Let O be ? ToObject(this value).
const object: JSReceiver = ToObject_Inline(context, receiver);
// 2. Let len be ? LengthOfArrayLike(O).
const len: Number = GetLengthProperty(object);
try {
// 3. Let relativeIndex be ? ToIntegerOrInfinity(index).
const relativeIndex = ToInteger_Inline(index);
// 4. If relativeIndex ≥ 0, let actualIndex be relativeIndex.
// 5. Else, let actualIndex be len + relativeIndex.
// 6. If actualIndex ≥ len or actualIndex < 0, throw a RangeError exception.
const actualIndex =
ConvertRelativeIndex(relativeIndex, len) otherwise OutOfBounds,
OutOfBounds;
try {
return TryFastPackedArrayWith(object, len, actualIndex, value)
otherwise Slow;
} label Slow {
return GenericArrayWith(context, object, len, actualIndex, value);
}
} label OutOfBounds deferred {
ThrowRangeError(MessageTemplate::kInvalid, 'index', index);
}
}
}
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