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