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AK: Add a Checked<T> template

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A Checked<T> is a boxed integer type that asserts if you try to use its
value after an arithmetic overflow.
This commit is contained in:
Andreas Kling 2020-04-15 16:53:09 +02:00
parent 3cdf4cd204
commit 9c54bad241
Notes: sideshowbarker 2024-07-19 07:34:24 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/9c54bad2415
1 changed files with 347 additions and 0 deletions
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/*
* Copyright (C) 2011-2019 Apple Inc. All rights reserved.
* Copyright (c) 2020, 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/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 static_cast<MakeUnsigned<Source>>(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>
inline constexpr bool is_within_range(Source value)
{
return TypeBoundsChecker<Destination, Source>::is_within_range(value);
}
template<typename T>
class Checked {
public:
Checked()
: m_value(0)
{
}
Checked(T value)
: m_value(value)
{
}
template<typename U>
Checked(U value)
{
m_overflow = !is_within_range<T>(value);
m_value = value;
}
Checked(const Checked& other)
: m_value(other.m_value)
, m_overflow(other.m_overflow)
{
}
Checked(Checked&& other)
: m_value(exchange(other.m_value, 0))
, m_overflow(exchange(other.m_overflow, false))
{
}
template<typename U>
Checked& operator=(U value)
{
return *this = Checked(value);
}
Checked& operator=(const Checked& other)
{
m_value = other.value();
m_overflow = other.m_overflow;
return *this;
}
Checked& operator=(Checked&& other)
{
m_value = exchange(other.m_value, 0);
m_overflow = exchange(other.m_overflow, false);
return *this;
}
bool has_overflow() const
{
return m_overflow;
}
bool operator!() const
{
ASSERT(!m_overflow);
return !m_value;
}
T value() const
{
ASSERT(!m_overflow);
return m_value;
}
void add(T other)
{
m_overflow |= __builtin_add_overflow(m_value, other, &m_value);
}
void sub(T other)
{
m_overflow |= __builtin_sub_overflow(m_value, other, &m_value);
}
void mul(T other)
{
m_overflow |= __builtin_mul_overflow(m_value, other, &m_value);
}
void div(T other)
{
m_value /= other;
}
Checked& operator+=(T other)
{
add(other);
return *this;
}
Checked& operator-=(T other)
{
sub(other);
return *this;
}
Checked& operator*=(T other)
{
mul(other);
return *this;
}
Checked& operator/=(T other)
{
div(other);
return *this;
}
Checked& operator++()
{
add(1);
return *this;
}
Checked& operator++(int)
{
add(1);
return *this;
}
private:
T m_value;
bool m_overflow { false };
};
template<typename T>
inline Checked<T> operator+(const Checked<T>& a, const Checked<T>& b)
{
return Checked<T>(a).add(b);
}
template<typename T>
inline Checked<T> operator-(const Checked<T>& a, const Checked<T>& b)
{
return Checked<T>(a).sub(b);
}
template<typename T>
inline Checked<T> operator*(const Checked<T>& a, const Checked<T>& b)
{
return Checked<T>(a).mul(b);
}
template<typename T>
inline Checked<T> operator/(const Checked<T>& a, const Checked<T>& b)
{
return Checked<T>(a).div(b);
}
template<typename T>
inline bool operator<(const Checked<T>& a, T b)
{
return a.value() < b;
}
template<typename T>
inline bool operator>(const Checked<T>& a, T b)
{
return a.value() > b;
}
template<typename T>
inline bool operator>=(const Checked<T>& a, T b)
{
return a.value() >= b;
}
template<typename T>
inline bool operator<=(const Checked<T>& a, T b)
{
return a.value() <= b;
}
template<typename T>
inline bool operator==(const Checked<T>& a, T b)
{
return a.value() == b;
}
template<typename T>
inline bool operator!=(const Checked<T>& a, T b)
{
return a.value() != b;
}
template<typename T>
inline bool operator<(T a, const Checked<T>& b)
{
return a < b.value();
}
template<typename T>
inline bool operator>(T a, const Checked<T>& b)
{
return a > b.value();
}
template<typename T>
inline bool operator>=(T a, const Checked<T>& b)
{
return a >= b.value();
}
template<typename T>
inline bool operator<=(T a, const Checked<T>& b)
{
return a <= b.value();
}
template<typename T>
inline bool operator==(T a, const Checked<T>& b)
{
return a == b.value();
}
template<typename T>
inline bool operator!=(T a, const Checked<T>& b)
{
return a != b.value();
}
template<typename T>
inline Checked<T> make_checked(T value)
{
return Checked<T>(value);
}
}
using AK::Checked;
using AK::make_checked;