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It wasn't safe to use addition_would_overflow(a, -b) to check if subtraction (a - b) would overflow, since it doesn't cover this case. I don't know why we didn't have subtraction_would_overflow(), so this patch adds it. :^)
557 lines
14 KiB
C++
557 lines
14 KiB
C++
/*
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* Copyright (C) 2011-2019 Apple Inc. All rights reserved.
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* Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/Concepts.h>
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#include <AK/NumericLimits.h>
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#include <AK/StdLibExtras.h>
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namespace AK {
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template<typename Destination, typename Source, bool destination_is_wider = (sizeof(Destination) >= sizeof(Source)), bool destination_is_signed = NumericLimits<Destination>::is_signed(), bool source_is_signed = NumericLimits<Source>::is_signed()>
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struct TypeBoundsChecker;
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template<typename Destination, typename Source>
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struct TypeBoundsChecker<Destination, Source, false, false, false> {
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static constexpr bool is_within_range(Source value)
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{
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return value <= NumericLimits<Destination>::max();
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}
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};
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template<typename Destination, typename Source>
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struct TypeBoundsChecker<Destination, Source, false, true, true> {
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static constexpr bool is_within_range(Source value)
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{
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return value <= NumericLimits<Destination>::max()
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&& NumericLimits<Destination>::min() <= value;
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}
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};
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template<typename Destination, typename Source>
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struct TypeBoundsChecker<Destination, Source, false, false, true> {
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static constexpr bool is_within_range(Source value)
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{
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return value >= 0 && value <= NumericLimits<Destination>::max();
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}
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};
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template<typename Destination, typename Source>
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struct TypeBoundsChecker<Destination, Source, false, true, false> {
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static constexpr bool is_within_range(Source value)
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{
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return value <= static_cast<Source>(NumericLimits<Destination>::max());
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}
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};
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template<typename Destination, typename Source>
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struct TypeBoundsChecker<Destination, Source, true, false, false> {
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static constexpr bool is_within_range(Source)
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{
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return true;
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}
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};
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template<typename Destination, typename Source>
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struct TypeBoundsChecker<Destination, Source, true, true, true> {
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static constexpr bool is_within_range(Source)
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{
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return true;
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}
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};
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template<typename Destination, typename Source>
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struct TypeBoundsChecker<Destination, Source, true, false, true> {
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static constexpr bool is_within_range(Source value)
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{
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return value >= 0;
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}
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};
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template<typename Destination, typename Source>
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struct TypeBoundsChecker<Destination, Source, true, true, false> {
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static constexpr bool is_within_range(Source value)
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{
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if (sizeof(Destination) > sizeof(Source))
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return true;
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return value <= static_cast<Source>(NumericLimits<Destination>::max());
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}
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};
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template<typename Destination, typename Source>
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[[nodiscard]] constexpr bool is_within_range(Source value)
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{
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return TypeBoundsChecker<Destination, Source>::is_within_range(value);
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}
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template<Integral T>
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class Checked {
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public:
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constexpr Checked() = default;
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explicit constexpr Checked(T value)
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: m_value(value)
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{
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}
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template<Integral U>
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constexpr Checked(U value)
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{
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m_overflow = !is_within_range<T>(value);
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m_value = value;
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}
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constexpr Checked(Checked const&) = default;
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constexpr Checked(Checked&& other)
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: m_value(exchange(other.m_value, 0))
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, m_overflow(exchange(other.m_overflow, false))
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{
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}
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template<typename U>
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constexpr Checked& operator=(U value)
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{
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*this = Checked(value);
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return *this;
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}
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constexpr Checked& operator=(Checked const& other) = default;
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constexpr Checked& operator=(Checked&& other)
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{
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m_value = exchange(other.m_value, 0);
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m_overflow = exchange(other.m_overflow, false);
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return *this;
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}
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[[nodiscard]] constexpr bool has_overflow() const
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{
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return m_overflow;
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}
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ALWAYS_INLINE constexpr bool operator!() const
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{
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VERIFY(!m_overflow);
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return !m_value;
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}
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ALWAYS_INLINE constexpr T value() const
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{
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VERIFY(!m_overflow);
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return m_value;
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}
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ALWAYS_INLINE constexpr T value_unchecked() const
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{
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return m_value;
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}
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constexpr void add(T other)
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{
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m_overflow |= __builtin_add_overflow(m_value, other, &m_value);
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}
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constexpr void sub(T other)
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{
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m_overflow |= __builtin_sub_overflow(m_value, other, &m_value);
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}
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constexpr void mul(T other)
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{
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m_overflow |= __builtin_mul_overflow(m_value, other, &m_value);
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}
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constexpr void div(T other)
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{
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if constexpr (IsSigned<T>) {
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// Ensure that the resulting value won't be out of range, this can only happen when dividing by -1.
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if (other == -1 && m_value == NumericLimits<T>::min()) {
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m_overflow = true;
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return;
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}
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}
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if (other == 0) {
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m_overflow = true;
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return;
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}
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m_value /= other;
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}
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constexpr void mod(T other)
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{
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auto initial = m_value;
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div(other);
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m_value *= other;
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m_value = initial - m_value;
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}
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constexpr void saturating_sub(T other)
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{
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sub(other);
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// Depending on whether other was positive or negative, we have to saturate to min or max.
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if (m_overflow && other <= 0)
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m_value = NumericLimits<T>::max();
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else if (m_overflow)
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m_value = NumericLimits<T>::min();
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m_overflow = false;
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}
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constexpr void saturating_add(T other)
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{
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add(other);
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// Depending on whether other was positive or negative, we have to saturate to max or min.
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if (m_overflow && other >= 0)
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m_value = NumericLimits<T>::max();
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else if (m_overflow)
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m_value = NumericLimits<T>::min();
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m_overflow = false;
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}
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constexpr void saturating_mul(T other)
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{
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// Figure out if the result is positive, negative or zero beforehand.
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auto either_is_zero = this->m_value == 0 || other == 0;
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auto result_is_positive = (this->m_value > 0) == (other > 0);
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mul(other);
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if (m_overflow) {
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if (either_is_zero)
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m_value = 0;
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else if (result_is_positive)
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m_value = NumericLimits<T>::max();
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else
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m_value = NumericLimits<T>::min();
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}
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m_overflow = false;
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}
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constexpr Checked& operator+=(Checked const& other)
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{
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m_overflow |= other.m_overflow;
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add(other.value());
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return *this;
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}
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constexpr Checked& operator+=(T other)
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{
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add(other);
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return *this;
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}
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constexpr Checked& operator-=(Checked const& other)
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{
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m_overflow |= other.m_overflow;
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sub(other.value());
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return *this;
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}
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constexpr Checked& operator-=(T other)
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{
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sub(other);
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return *this;
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}
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constexpr Checked& operator*=(Checked const& other)
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{
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m_overflow |= other.m_overflow;
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mul(other.value());
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return *this;
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}
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constexpr Checked& operator*=(T other)
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{
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mul(other);
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return *this;
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}
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constexpr Checked& operator/=(Checked const& other)
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{
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m_overflow |= other.m_overflow;
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div(other.value());
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return *this;
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}
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constexpr Checked& operator/=(T other)
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{
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div(other);
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return *this;
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}
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constexpr Checked& operator%=(Checked const& other)
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{
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m_overflow |= other.m_overflow;
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mod(other.value());
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return *this;
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}
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constexpr Checked& operator%=(T other)
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{
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mod(other);
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return *this;
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}
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constexpr Checked& operator++()
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{
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add(1);
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return *this;
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}
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constexpr Checked operator++(int)
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{
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Checked old { *this };
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add(1);
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return old;
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}
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constexpr Checked& operator--()
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{
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sub(1);
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return *this;
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}
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constexpr Checked operator--(int)
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{
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Checked old { *this };
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sub(1);
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return old;
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}
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template<typename U, typename V>
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[[nodiscard]] static constexpr bool addition_would_overflow(U u, V v)
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{
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#if __has_builtin(__builtin_add_overflow_p)
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return __builtin_add_overflow_p(u, v, (T)0);
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#elif __has_builtin(__builtin_add_overflow)
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T result;
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return __builtin_add_overflow(u, v, &result);
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#else
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Checked checked;
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checked = u;
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checked += v;
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return checked.has_overflow();
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#endif
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}
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template<typename U, typename V>
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[[nodiscard]] static constexpr bool subtraction_would_overflow(U u, V v)
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{
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#if __has_builtin(__builtin_sub_overflow_p)
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return __builtin_sub_overflow_p(u, v, (T)0);
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#elif __has_builtin(__builtin_sub_overflow)
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T result;
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return __builtin_sub_overflow(u, v, &result);
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#else
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Checked checked;
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checked = u;
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checked -= v;
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return checked.has_overflow();
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#endif
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}
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template<typename U, typename V>
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static constexpr T saturating_add(U a, V b)
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{
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Checked checked { a };
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checked.saturating_add(b);
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return checked.value();
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}
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template<typename U, typename V>
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static constexpr T saturating_sub(U a, V b)
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{
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Checked checked { a };
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checked.saturating_sub(b);
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return checked.value();
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}
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template<typename U, typename V>
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static constexpr T saturating_mul(U a, V b)
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{
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Checked checked { a };
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checked.saturating_mul(b);
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return checked.value();
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}
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template<typename U, typename V>
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[[nodiscard]] static constexpr bool multiplication_would_overflow(U u, V v)
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{
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#if __has_builtin(__builtin_mul_overflow_p)
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return __builtin_mul_overflow_p(u, v, (T)0);
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#elif __has_builtin(__builtin_mul_overflow)
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T result;
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return __builtin_mul_overflow(u, v, &result);
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#else
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Checked checked;
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checked = u;
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checked *= v;
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return checked.has_overflow();
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#endif
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}
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template<typename U, typename V, typename X>
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[[nodiscard]] static constexpr bool multiplication_would_overflow(U u, V v, X x)
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{
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Checked checked;
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checked = u;
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checked *= v;
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checked *= x;
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return checked.has_overflow();
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}
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private:
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T m_value {};
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bool m_overflow { false };
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};
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template<typename T>
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constexpr Checked<T> operator+(Checked<T> const& a, Checked<T> const& b)
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{
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Checked<T> c { a };
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c.add(b.value());
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return c;
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}
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template<typename T>
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constexpr Checked<T> operator-(Checked<T> const& a, Checked<T> const& b)
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{
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Checked<T> c { a };
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c.sub(b.value());
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return c;
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}
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template<typename T>
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constexpr Checked<T> operator*(Checked<T> const& a, Checked<T> const& b)
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{
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Checked<T> c { a };
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c.mul(b.value());
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return c;
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}
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template<typename T>
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constexpr Checked<T> operator/(Checked<T> const& a, Checked<T> const& b)
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{
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Checked<T> c { a };
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c.div(b.value());
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return c;
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}
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template<typename T>
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constexpr Checked<T> operator%(Checked<T> const& a, Checked<T> const& b)
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{
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Checked<T> c { a };
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c.mod(b.value());
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return c;
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}
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template<typename T>
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constexpr bool operator<(Checked<T> const& a, T b)
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{
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return a.value() < b;
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}
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template<typename T>
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constexpr bool operator>(Checked<T> const& a, T b)
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{
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return a.value() > b;
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}
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template<typename T>
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constexpr bool operator>=(Checked<T> const& a, T b)
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{
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return a.value() >= b;
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}
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template<typename T>
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constexpr bool operator<=(Checked<T> const& a, T b)
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{
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return a.value() <= b;
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}
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template<typename T>
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constexpr bool operator==(Checked<T> const& a, T b)
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{
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return a.value() == b;
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}
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template<typename T>
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constexpr bool operator!=(Checked<T> const& a, T b)
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{
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return a.value() != b;
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}
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template<typename T>
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constexpr bool operator<(T a, Checked<T> const& b)
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{
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return a < b.value();
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}
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template<typename T>
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constexpr bool operator>(T a, Checked<T> const& b)
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{
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return a > b.value();
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}
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template<typename T>
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constexpr bool operator>=(T a, Checked<T> const& b)
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{
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return a >= b.value();
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}
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template<typename T>
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constexpr bool operator<=(T a, Checked<T> const& b)
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{
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return a <= b.value();
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}
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template<typename T>
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constexpr bool operator==(T a, Checked<T> const& b)
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{
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return a == b.value();
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}
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template<typename T>
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constexpr bool operator!=(T a, Checked<T> const& b)
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{
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return a != b.value();
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}
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template<typename T>
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constexpr Checked<T> make_checked(T value)
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{
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return Checked<T>(value);
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}
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}
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#if USING_AK_GLOBALLY
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using AK::Checked;
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using AK::make_checked;
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#endif
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