StaticArray.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include <Jolt/Core/HashCombine.h>
 
JPH_NAMESPACE_BEGIN
 
template <class T, uint N>
class [[nodiscard]] StaticArray
{
public:
    using value_type = T;
 
    using size_type = uint;
 
    static constexpr uint Capacity = N;
 
                        StaticArray() = default;
 
    explicit            StaticArray(std::initializer_list<T> inList)
    {
        JPH_ASSERT(inList.size() <= N);
        for (const T &v : inList)
            ::new (reinterpret_cast<T *>(&mElements[mSize++])) T(v);
    }
 
                        StaticArray(const StaticArray<T, N> &inRHS)
    {
        while (mSize < inRHS.mSize)
        {
            ::new (&mElements[mSize]) T(inRHS[mSize]);
            ++mSize;
        }
    }
 
                        ~StaticArray()
    {
        if constexpr (!is_trivially_destructible<T>())
            for (T *e = reinterpret_cast<T *>(mElements), *end = e + mSize; e < end; ++e)
                e->~T();
    }
 
    void                clear()
    {
        if constexpr (!is_trivially_destructible<T>())
            for (T *e = reinterpret_cast<T *>(mElements), *end = e + mSize; e < end; ++e)
                e->~T();
        mSize = 0;
    }
 
    void                push_back(const T &inElement)
    {
        JPH_ASSERT(mSize < N);
        ::new (&mElements[mSize++]) T(inElement);
    }
 
    template <class... A>
    void                emplace_back(A &&... inElement)
    {
        JPH_ASSERT(mSize < N);
        ::new (&mElements[mSize++]) T(std::forward<A>(inElement)...);
    }
 
    void                pop_back()
    {
        JPH_ASSERT(mSize > 0);
        reinterpret_cast<T &>(mElements[--mSize]).~T();
    }
 
    bool                empty() const
    {
        return mSize == 0;
    }
 
    size_type           size() const
    {
        return mSize;
    }
 
    size_type           capacity() const
    {
        return N;
    }
 
    void                resize(size_type inNewSize)
    {
        JPH_ASSERT(inNewSize <= N);
        if constexpr (!is_trivially_constructible<T>())
            for (T *element = reinterpret_cast<T *>(mElements) + mSize, *element_end = reinterpret_cast<T *>(mElements) + inNewSize; element < element_end; ++element)
                ::new (element) T;
        if constexpr (!is_trivially_destructible<T>())
            for (T *element = reinterpret_cast<T *>(mElements) + inNewSize, *element_end = reinterpret_cast<T *>(mElements) + mSize; element < element_end; ++element)
                element->~T();
        mSize = inNewSize;
    }
 
    using const_iterator = const T *;
 
    const_iterator      begin() const
    {
        return reinterpret_cast<const T *>(mElements);
    }
 
    const_iterator      end() const
    {
        return reinterpret_cast<const T *>(mElements + mSize);
    }
 
    using iterator = T *;
 
    iterator            begin()
    {
        return reinterpret_cast<T *>(mElements);
    }
 
    iterator            end()
    {
        return reinterpret_cast<T *>(mElements + mSize);
    }
 
    const T *           data() const
    {
        return reinterpret_cast<const T *>(mElements);
    }
 
    T *                 data()
    {
        return reinterpret_cast<T *>(mElements);
    }
 
    T &                 operator [] (size_type inIdx)
    {
        JPH_ASSERT(inIdx < mSize);
        return reinterpret_cast<T &>(mElements[inIdx]);
    }
 
    const T &           operator [] (size_type inIdx) const
    {
        JPH_ASSERT(inIdx < mSize);
        return reinterpret_cast<const T &>(mElements[inIdx]);
    }
 
    T &                 at(size_type inIdx)
    {
        JPH_ASSERT(inIdx < mSize);
        return reinterpret_cast<T &>(mElements[inIdx]);
    }
 
    const T &           at(size_type inIdx) const
    {
        JPH_ASSERT(inIdx < mSize);
        return reinterpret_cast<const T &>(mElements[inIdx]);
    }
 
    const T &           front() const
    {
        JPH_ASSERT(mSize > 0);
        return reinterpret_cast<const T &>(mElements[0]);
    }
 
    T &                 front()
    {
        JPH_ASSERT(mSize > 0);
        return reinterpret_cast<T &>(mElements[0]);
    }
 
    const T &           back() const
    {
        JPH_ASSERT(mSize > 0);
        return reinterpret_cast<const T &>(mElements[mSize - 1]);
    }
 
    T &                 back()
    {
        JPH_ASSERT(mSize > 0);
        return reinterpret_cast<T &>(mElements[mSize - 1]);
    }
 
    void                erase(const_iterator inIter)
    {
        size_type p = size_type(inIter - begin());
        JPH_ASSERT(p < mSize);
        reinterpret_cast<T &>(mElements[p]).~T();
        if (p + 1 < mSize)
            memmove(mElements + p, mElements + p + 1, (mSize - p - 1) * sizeof(T));
        --mSize;
    }
 
    void                erase(const_iterator inBegin, const_iterator inEnd)
    {
        size_type p = size_type(inBegin - begin());
        size_type n = size_type(inEnd - inBegin);
        JPH_ASSERT(inEnd <= end());
        for (size_type i = 0; i < n; ++i)
            reinterpret_cast<T &>(mElements[p + i]).~T();
        if (p + n < mSize)
            memmove(mElements + p, mElements + p + n, (mSize - p - n) * sizeof(T));
        mSize -= n;
    }
 
    StaticArray<T, N> & operator = (const StaticArray<T, N> &inRHS)
    {
        size_type rhs_size = inRHS.size();
 
        if (static_cast<const void *>(this) != static_cast<const void *>(&inRHS))
        {
            clear();
 
            while (mSize < rhs_size)
            {
                ::new (&mElements[mSize]) T(inRHS[mSize]);
                ++mSize;
            }
        }
 
        return *this;
    }
 
    template <uint M>
    StaticArray<T, N> & operator = (const StaticArray<T, M> &inRHS)
    {
        size_type rhs_size = inRHS.size();
        JPH_ASSERT(rhs_size <= N);
 
        if (static_cast<const void *>(this) != static_cast<const void *>(&inRHS))
        {
            clear();
 
            while (mSize < rhs_size)
            {
                ::new (&mElements[mSize]) T(inRHS[mSize]);
                ++mSize;
            }
        }
 
        return *this;
    }
 
    bool                operator == (const StaticArray<T, N> &inRHS) const
    {
        if (mSize != inRHS.mSize)
            return false;
        for (size_type i = 0; i < mSize; ++i)
            if (!(reinterpret_cast<const T &>(mElements[i]) == reinterpret_cast<const T &>(inRHS.mElements[i])))
                return false;
        return true;
    }
 
    bool                operator != (const StaticArray<T, N> &inRHS) const
    {
        if (mSize != inRHS.mSize)
            return true;
        for (size_type i = 0; i < mSize; ++i)
            if (reinterpret_cast<const T &>(mElements[i]) != reinterpret_cast<const T &>(inRHS.mElements[i]))
                return true;
        return false;
    }
 
    uint64                  GetHash() const
    {
        // Hash length first
        uint64 ret = Hash<uint32> { } (uint32(size()));
 
        // Then hash elements
        for (const T *element = reinterpret_cast<const T *>(mElements), *element_end = reinterpret_cast<const T *>(mElements) + mSize; element < element_end; ++element)
            HashCombine(ret, *element);
 
        return ret;
    }
 
protected:
    struct alignas(T) Storage
    {
        uint8           mData[sizeof(T)];
    };
 
    static_assert(sizeof(T) == sizeof(Storage), "Mismatch in size");
    static_assert(alignof(T) == alignof(Storage), "Mismatch in alignment");
 
    size_type           mSize = 0;
    Storage             mElements[N];
};
 
JPH_NAMESPACE_END
 
JPH_SUPPRESS_WARNING_PUSH
JPH_CLANG_SUPPRESS_WARNING("-Wc++98-compat")
 
namespace std
{
    template <class T, JPH::uint N>
    struct hash<JPH::StaticArray<T, N>>
    {
        size_t operator () (const JPH::StaticArray<T, N> &inRHS) const
        {
            return std::size_t(inRHS.GetHash());
        }
    };
}
 
JPH_SUPPRESS_WARNING_POP