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- /*
- * Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
- #include <AK/String.h>
- #include <LibJS/Runtime/AbstractOperations.h>
- #include <LibJS/Runtime/BigInt.h>
- #include <LibJS/Runtime/BigIntConstructor.h>
- #include <LibJS/Runtime/BigIntObject.h>
- #include <LibJS/Runtime/Error.h>
- #include <LibJS/Runtime/GlobalObject.h>
- #include <LibJS/Runtime/VM.h>
- namespace JS {
- static const Crypto::SignedBigInteger BIGINT_ONE { 1 };
- BigIntConstructor::BigIntConstructor(Realm& realm)
- : NativeFunction(vm().names.BigInt.as_string(), *realm.global_object().function_prototype())
- {
- }
- void BigIntConstructor::initialize(Realm& realm)
- {
- auto& vm = this->vm();
- NativeFunction::initialize(realm);
- // 21.2.2.3 BigInt.prototype, https://tc39.es/ecma262/#sec-bigint.prototype
- define_direct_property(vm.names.prototype, realm.global_object().bigint_prototype(), 0);
- u8 attr = Attribute::Writable | Attribute::Configurable;
- define_native_function(vm.names.asIntN, as_int_n, 2, attr);
- define_native_function(vm.names.asUintN, as_uint_n, 2, attr);
- define_direct_property(vm.names.length, Value(1), Attribute::Configurable);
- }
- // 21.2.1.1 BigInt ( value ), https://tc39.es/ecma262/#sec-bigint-constructor-number-value
- ThrowCompletionOr<Value> BigIntConstructor::call()
- {
- auto& vm = this->vm();
- auto& global_object = this->global_object();
- auto value = vm.argument(0);
- // 2. Let prim be ? ToPrimitive(value, number).
- auto primitive = TRY(value.to_primitive(global_object, Value::PreferredType::Number));
- // 3. If Type(prim) is Number, return ? NumberToBigInt(prim).
- if (primitive.is_number())
- return TRY(number_to_bigint(global_object, primitive));
- // 4. Otherwise, return ? ToBigInt(prim).
- return TRY(primitive.to_bigint(global_object));
- }
- // 21.2.1.1 BigInt ( value ), https://tc39.es/ecma262/#sec-bigint-constructor-number-value
- ThrowCompletionOr<Object*> BigIntConstructor::construct(FunctionObject&)
- {
- return vm().throw_completion<TypeError>(global_object(), ErrorType::NotAConstructor, "BigInt");
- }
- // 21.2.2.1 BigInt.asIntN ( bits, bigint ), https://tc39.es/ecma262/#sec-bigint.asintn
- JS_DEFINE_NATIVE_FUNCTION(BigIntConstructor::as_int_n)
- {
- // 1. Set bits to ? ToIndex(bits).
- auto bits = TRY(vm.argument(0).to_index(global_object));
- // 2. Set bigint to ? ToBigInt(bigint).
- auto* bigint = TRY(vm.argument(1).to_bigint(global_object));
- // 3. Let mod be ℝ(bigint) modulo 2^bits.
- // FIXME: For large values of `bits`, this can likely be improved with a SignedBigInteger API to
- // drop the most significant bits.
- auto bits_shift_left = BIGINT_ONE.shift_left(bits);
- auto mod = modulo(bigint->big_integer(), bits_shift_left);
- // 4. If mod ≥ 2^(bits-1), return ℤ(mod - 2^bits); otherwise, return ℤ(mod).
- // NOTE: Some of the below conditionals are non-standard, but are to protect SignedBigInteger from
- // allocating an absurd amount of memory if `bits - 1` overflows to NumericLimits<size_t>::max.
- if ((bits == 0) && (mod >= BIGINT_ONE))
- return js_bigint(vm, mod.minus(bits_shift_left));
- if ((bits > 0) && (mod >= BIGINT_ONE.shift_left(bits - 1)))
- return js_bigint(vm, mod.minus(bits_shift_left));
- return js_bigint(vm, mod);
- }
- // 21.2.2.2 BigInt.asUintN ( bits, bigint ), https://tc39.es/ecma262/#sec-bigint.asuintn
- JS_DEFINE_NATIVE_FUNCTION(BigIntConstructor::as_uint_n)
- {
- // 1. Set bits to ? ToIndex(bits).
- auto bits = TRY(vm.argument(0).to_index(global_object));
- // 2. Set bigint to ? ToBigInt(bigint).
- auto* bigint = TRY(vm.argument(1).to_bigint(global_object));
- // 3. Return the BigInt value that represents ℝ(bigint) modulo 2bits.
- // FIXME: For large values of `bits`, this can likely be improved with a SignedBigInteger API to
- // drop the most significant bits.
- return js_bigint(vm, modulo(bigint->big_integer(), BIGINT_ONE.shift_left(bits)));
- }
- }
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