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/*
* Copyright (c) 2020-2022, 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>(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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