ladybird/AK/Checked.h
Andreas Kling a264cf79c4 AK: Use fallback builtins for overflow checks in AK::Checked
If we don't have __builtin_add_overflow_p(), we can also try using
__builtin_add_overflow(). This makes debug builds with Clang
significantly faster since they no longer need to use the generic
implementation. Same for multiplication.
2023-12-21 15:31:32 +01:00

541 lines
13 KiB
C++

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