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/*
* Copyright (C) 2021 Apple Inc. 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 APPLE INC. ``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 APPLE INC. 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 <concepts>
#include <type_traits>
#include <wtf/StdLibExtras.h>
#include <wtf/Vector.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace WTF {
// TrailingArray offers the feature trailing array in the derived class.
// We can allocate a memory like the following layout.
//
// [ DerivedClass ][ Trailing Array ]
//
// And trailing array offers appropriate methods for accessing and destructions.
template<typename Derived, typename T>
class TrailingArray {
WTF_MAKE_NONCOPYABLE(TrailingArray);
friend class JSC::LLIntOffsetsExtractor;
public:
using value_type = T;
using pointer = T*;
using reference = T&;
using const_reference = const T&;
using const_pointer = const T*;
using size_type = unsigned;
using difference_type = std::make_signed_t<size_type>;
using iterator = T*;
using const_iterator = const T*;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
protected:
explicit TrailingArray(unsigned size)
: m_size(size)
{
static_assert(std::is_final_v<Derived>);
VectorTypeOperations<T>::initializeIfNonPOD(begin(), end());
}
template<typename InputIterator>
TrailingArray(unsigned size, InputIterator first, InputIterator last)
: m_size(size)
{
static_assert(std::is_final_v<Derived>);
ASSERT(static_cast<size_t>(std::distance(first, last)) == size);
std::uninitialized_copy(first, last, begin());
}
template<typename... Args>
TrailingArray(unsigned size, Args&&... args) // create with given size and constructor arguments for all elements
: m_size(size)
{
static_assert(std::is_final_v<Derived>);
VectorTypeOperations<T>::initializeWithArgs(begin(), end(), std::forward<Args>(args)...);
}
// This constructor, which is used via the `Failable` token, will attempt
// to initialize the array from the generator. The generator returns
// `std::optional` values, and if one is `nullopt`, that indicates a failure.
// The constructor sets `m_size` to the index of the most recently successful
// item to be added in order for the destructor to destroy the right number
// of elements.
//
// It is the responsibility of the caller to check that `size()` is equal
// to the `size` the caller passed in. If it is not, that is failure, and
// should be used as appropriate.
struct Failable { };
template<std::invocable<size_t> Generator>
explicit TrailingArray(Failable, unsigned size, NOESCAPE Generator&& generator)
: m_size(size)
{
static_assert(std::is_final_v<Derived>);
for (size_t i = 0; i < m_size; ++i) {
if (auto value = generator(i))
new (NotNull, std::addressof(begin()[i])) T(WTFMove(*value));
else {
m_size = i;
return;
}
}
}
~TrailingArray()
{
VectorTypeOperations<T>::destruct(begin(), end());
}
public:
static constexpr size_t allocationSize(unsigned size)
{
return offsetOfData() + size * sizeof(T);
}
unsigned size() const { return m_size; }
bool isEmpty() const { return !size(); }
unsigned byteSize() const { return size() * sizeof(T); }
pointer data() LIFETIME_BOUND { return std::bit_cast<T*>(std::bit_cast<uint8_t*>(static_cast<Derived*>(this)) + offsetOfData()); }
const_pointer data() const LIFETIME_BOUND { return std::bit_cast<const T*>(std::bit_cast<const uint8_t*>(static_cast<const Derived*>(this)) + offsetOfData()); }
std::span<T> span() LIFETIME_BOUND { return { data(), size() }; }
std::span<const T> span() const LIFETIME_BOUND { return { data(), size() }; }
iterator begin() LIFETIME_BOUND { return data(); }
iterator end() LIFETIME_BOUND { return data() + size(); }
const_iterator begin() const LIFETIME_BOUND { return cbegin(); }
const_iterator end() const LIFETIME_BOUND { return cend(); }
const_iterator cbegin() const LIFETIME_BOUND { return data(); }
const_iterator cend() const LIFETIME_BOUND { return data() + size(); }
reverse_iterator rbegin() LIFETIME_BOUND { return reverse_iterator(end()); }
reverse_iterator rend() LIFETIME_BOUND { return reverse_iterator(begin()); }
const_reverse_iterator rbegin() const LIFETIME_BOUND { return crbegin(); }
const_reverse_iterator rend() const LIFETIME_BOUND { return crend(); }
const_reverse_iterator crbegin() const LIFETIME_BOUND { return const_reverse_iterator(end()); }
const_reverse_iterator crend() const LIFETIME_BOUND { return const_reverse_iterator(begin()); }
reference at(unsigned i) LIFETIME_BOUND
{
RELEASE_ASSERT(i < size());
return begin()[i];
}
const_reference at(unsigned i) const LIFETIME_BOUND
{
RELEASE_ASSERT(i < size());
return begin()[i];
}
reference operator[](unsigned i) LIFETIME_BOUND { return at(i); }
const_reference operator[](unsigned i) const LIFETIME_BOUND { return at(i); }
T& first() LIFETIME_BOUND { return (*this)[0]; }
const T& first() const LIFETIME_BOUND { return (*this)[0]; }
T& last() LIFETIME_BOUND { return (*this)[size() - 1]; }
const T& last() const LIFETIME_BOUND { return (*this)[size() - 1]; }
void fill(const T& val)
{
std::fill(begin(), end(), val);
}
static constexpr ptrdiff_t offsetOfSize() { return OBJECT_OFFSETOF(Derived, m_size); }
static constexpr ptrdiff_t offsetOfData()
{
return WTF::roundUpToMultipleOf<alignof(T)>(sizeof(Derived));
}
protected:
unsigned m_size { 0 };
};
} // namespace WTF
using WTF::TrailingArray;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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