palVector.h

/*
 ***********************************************************************************************************************
 *
 *  Copyright (c) 2015-2021 Advanced Micro Devices, Inc. All Rights Reserved.
 *
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 *  of this software and associated documentation files (the "Software"), to deal
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 **********************************************************************************************************************/
/**
***********************************************************************************************************************
* @file  palVector.h
* @brief PAL utility collection Vector and VectorIterator class declarations.
***********************************************************************************************************************
*/

#pragma once

#include "palUtil.h"
#include "palAssert.h"
#include "palSysMemory.h"
#include <type_traits>

namespace Util
{

// Forward declarations.
template<typename T, uint32 defaultCapacity, typename Allocator> class Vector;

/**
 ***********************************************************************************************************************
 * @brief  Iterator for traversal of elements in Vector.
 *
 * Supports forward traversal.
 ***********************************************************************************************************************
 */
template<typename T, uint32 defaultCapacity, typename Allocator>
class VectorIterator
{
public:
    ~VectorIterator() { }

    /// Checks if the current index is within bounds of the number of elements in the vector.
    ///
    /// @returns True if the current element this iterator is pointing to is within the permitted range.
    bool IsValid() const { return (m_curIndex < m_srcVector.m_numElements); }

    /// Returns the element the iterator is currently pointing to as a reference.
    ///
    /// @warning This may cause an access violation if the iterator is not valid.
    ///
    /// @returns The element the iterator is currently pointing to.
    T& Get() const
    {
        PAL_ASSERT(IsValid());
        return (*(m_srcVector.m_pData + m_curIndex));
    }

    /// Advances the iterator to point to the next element.
    ///
    /// @warning Does not do bounds checking.
    void Next() { ++m_curIndex; }

    /// Retrieves the current vector position of this iterator.
    ///
    /// @returns The location in the vector of the element the iterator is currently pointing to.
    uint32 Position() const { return m_curIndex; }

private:
    VectorIterator(uint32 index, const Vector<T, defaultCapacity, Allocator>& srcVec);

    uint32                                        m_curIndex;  // The current index of the vector iterator.
    const Vector<T, defaultCapacity, Allocator>&  m_srcVector; // The vector container this iterator is used for.

    PAL_DISALLOW_DEFAULT_CTOR(VectorIterator);

    // Although this is a transgression of coding standards, it means that Vector does not need to have a public
    // interface specifically to implement this class. The added encapsulation this provides is worthwhile.
    friend class Vector<T, defaultCapacity, Allocator>;
};

/**
 ***********************************************************************************************************************
 * @brief Vector container.
 *
 * Vector is a templated array based storage that starts with a default-size allocation in the stack. If more space is
 * needed it then resorts to dynamic allocation by doubling the size every time the capacity is exceeded.
 * Operations which this class supports are:
 *
 * - Insertion at the end of the array.
 * - Forward iteration.
 * - Random access.
 *
 * @warning This class is not thread-safe.
 ***********************************************************************************************************************
 */
template<typename T, uint32 defaultCapacity, typename Allocator>
class Vector
{
public:
    /// A convenient shorthand for VectorIterator.
    typedef VectorIterator<T, defaultCapacity, Allocator> Iter;

    /// Constructor.
    ///
    /// @param [in] pAllocator The allocator that will allocate memory if required.
    Vector(Allocator*const pAllocator);

    /// Destructor.
    virtual ~Vector();

    /// Move constructor.
    ///
    /// @param [in] vector Reference to a dying vector, from which resources will be stolen.
    Vector(Vector&& vector);

    /// Increases maximal capacity to value grater or equal to the newCapacity.
    /// If newCapacity is greater than the maximal capacity, new storage is allocated,
    /// otherwise the method does nothing.
    ///
    /// @note All existing iterators will not get invalidated, even in case new storage is allocated,
    ///       because iterators are referencing vector, rather than elements of that vector.
    ///
    /// @warning All pointers and references to elements of a vector will be invalidated,
    ///          in case new storage is allocated.
    ///
    /// @param [in] newCapacity The new capacity of a vector, which is lower limit of the maximal capacity.
    ///
    /// @returns Result ErrorOutOfMemory if the operation failed.
    Result Reserve(uint32 newCapacity);

    /// Set size to newSize.
    /// If size is decreased, elements at the end of the vector will be removed.
    /// If size is increased, new elements will be set to newVal.
    /// If newSize requires a higher capacity, a new allocation is made.  See notes on Reserve.
    ///
    /// @note If size is decreased, any iterators referencing removed elements will become invalid.  All other
    ///       iterators will remain valid.  Otherwise, all iterators will still be valid.
    ///
    /// @warning All pointers and references to elements of a vector will be invalidated,
    ///          in case new storage is allocated.
    ///
    /// @param [in] newSize The new size of a vector.
    ///
    /// @returns Result ErrorOutOfMemory if the operation failed.
    Result Resize(uint32 newSize, const T& newVal = T());

    /// Copy an element to end of the vector. If not enough space is available, new space will be allocated and the old
    /// data will be copied to the new space.
    ///
    /// @param [in] data The element to be pushed to the vector. The element will become the last element.
    ///
    /// @returns Result ErrorOutOfMemory if the operation failed.
    Result PushBack(const T& data);

    /// Returns the element at the end of the vector and destroys it.
    ///
    /// @param [out] pData The element at the end of the vector
    void PopBack(T* pData);

    /// Destroys all elements stored in the vector. All dynamically allocated memory will be saved for reuse.
    void Clear();

    ///@{
    /// Returns the element at the location specified.
    ///
    /// @warning Calling this function with an out-of-bounds index will cause an access violation!
    ///
    /// @param [in] index Integer location of the element needed.
    ///
    /// @returns The element at location specified by index by reference
    T& At(uint32 index)
    {
        PAL_ASSERT(index < m_numElements);
        return *(m_pData + index);
    }

    const T& At(uint32 index) const
    {
        PAL_ASSERT(index < m_numElements);
        return *(m_pData + index);
    }

    T&       operator[](uint32 index) noexcept       { return At(index); }
    const T& operator[](uint32 index) const noexcept { return At(index); }
    ///@}

    /// Returns the data at the front of the vector.
    ///
    /// @warning Calling this function on an empty vector will cause an access violation!
    ///
    /// @returns The data at the front of the vector.
    T& Front() const
    {
        PAL_ASSERT(IsEmpty() == false);
        return *m_pData;
    }

    /// Returns the data at the back of the vector.
    ///
    /// @warning Calling this function on an empty vector will cause an access violation!
    ///
    /// @returns The data at the back of the vector.
    T& Back() const
    {
        PAL_ASSERT(IsEmpty() == false);
        return *(m_pData + (m_numElements - 1));
    }

    /// Returns an iterator to the first element of the vector.
    ///
    /// @warning Accessing an element using an iterator of an empty vector will cause an access violation!
    ///
    /// @returns An iterator to first element of the vector.
    Iter Begin() const { return Iter(0, *this); }

    /// Returns an iterator to the last element of the vector.
    ///
    /// @warning Accessing an element using an iterator of an empty vector will cause an access violation!
    ///
    /// @returns VectorIterator An iterator to last element of the vector.
    Iter End() const { return Iter((m_numElements - 1), *this); }

    /// Returns pointer to the underlying buffer serving as data storage.
    /// The returned pointer defines always valid range [Data(), Data() + NumElements()),
    /// even if the container is empty (Data() is not dereferenceable in that case).
    ///
    /// @warning Dereferencing pointer returned by Data() from an empty vector will cause an access violation!
    ///
    /// @returns Pointer to the underlying data storage for read & write access.
    ///          For a non-empty vector, the returned pointer contains address of the first element.
    ///          For an empty vector, the returned pointer may or may not be a null pointer.
    T* Data() { return m_pData; }

    /// Returns pointer to the underlying buffer serving as data storage.
    /// The returned pointer defines always valid range [Data(), Data() + NumElements()),
    /// even if the container is empty (Data() is not dereferenceable in that case).
    ///
    /// @warning Dereferencing pointer returned by Data() from an empty vector will cause an access violation!
    ///
    /// @returns Pointer to the underlying data storage for read only access.
    ///          For a non-empty vector, the returned pointer contains address of the first element.
    ///          For an empty vector, the returned pointer may or may not be a null pointer.
    const T* Data() const { return m_pData; }

    /// Returns the size of the vector.
    ///
    /// @returns An unsigned integer equal to the number of elements currently present in the vector.
    uint32 NumElements() const { return m_numElements; }

    /// Returns true if the number of elements present in the vector is equal to zero.
    ///
    /// @returns True if the vector is empty.
    bool IsEmpty() const { return (m_numElements == 0); }

    ///@{
    /// @internal Satisfies concept `range_expression`, using T* as `iterator` and 32-bit size and difference types
    ///
    /// @note - These are a convenience intended to be used by c++ language features such as `range for`.
    ///         These should not be called directly as they do not adhere to PAL coding standards.
    using value_type      = T;
    using reference       = T&;
    using const_reference = const T&;
    using iterator        = T*;
    using const_iterator  = const T*;
    using difference_type = int32;
    using size_type       = uint32;

    iterator           begin()  noexcept       { return m_pData; }
    iterator           end()    noexcept       { return (m_pData + m_numElements); }
    const_iterator     begin()  const noexcept { return m_pData; }
    const_iterator     end()    const noexcept { return (m_pData + m_numElements); }
    const_iterator     cbegin() const noexcept { return m_pData; }
    const_iterator     cend()   const noexcept { return (m_pData + m_numElements); }
    PAL_NODISCARD bool empty()  const noexcept { return IsEmpty(); }
    size_type          size()   const noexcept { return m_numElements; }
    ///@}

private:
    // This is a POD-type that exactly fits one T value.
    typedef typename std::aligned_storage<sizeof(T), alignof(T)>::type ValueStorage;

    ValueStorage     m_data[defaultCapacity];  // The initial data buffer stored within the vector object.
    T*               m_pData;                  // Pointer to the current data buffer.
    uint32           m_numElements;            // Number of elements present.
    uint32           m_maxCapacity;            // Maximum size it can hold.
    Allocator*const  m_pAllocator;             // Allocator for this Vector.

    PAL_DISALLOW_COPY_AND_ASSIGN(Vector);

    // Although this is a transgression of coding standards, it prevents VectorIterator requiring a public constructor;
    // constructing a 'bare' VectorIterator (i.e. without calling Vector::GetIterator) can never be a legal operation,
    // so this means that these two classes are much safer to use.
    friend class VectorIterator<T, defaultCapacity, Allocator>;
};

// =====================================================================================================================
template<typename T, uint32 defaultCapacity, typename Allocator>
VectorIterator<T, defaultCapacity, Allocator>::VectorIterator(
    uint32                                       index,
    const Vector<T, defaultCapacity, Allocator>& srcVec)
    :
    m_curIndex(index),
    m_srcVector(srcVec)
 {
 }

// =====================================================================================================================
template<typename T, uint32 defaultCapacity, typename Allocator>
Vector<T, defaultCapacity, Allocator>::Vector(
    Allocator*const pAllocator)
    :
    m_pData(reinterpret_cast<T*>(m_data)),
    m_numElements(0),
    m_maxCapacity(defaultCapacity),
    m_pAllocator(pAllocator)
 {
 }

// =====================================================================================================================
template<typename T, uint32 defaultCapacity, typename Allocator>
Vector<T, defaultCapacity, Allocator>::~Vector()
{
    // Explicitly destroy all non-trivial types.
    if (!std::is_pod<T>::value)
    {
        for (uint32 idx = 0; idx < m_numElements; ++idx)
        {
            m_pData[idx].~T();
        }
    }

    // Check if we have dynamically allocated memory.
    if (m_pData != reinterpret_cast<T*>(m_data))
    {
        // Free the memory that was allocated dynamically.
        PAL_FREE(m_pData, m_pAllocator);
    }
}

// =====================================================================================================================
// Steals allocation from a dying vector, if data buffer uses storage from heap allocation.
// Moves objects between local buffers of new and dying vectors (for non-trivial types) or
// copies local buffer from a dying vector to a new vector (for trivial types),
// if data buffer uses storage from local buffer.
template<typename T, uint32 defaultCapacity, typename Allocator>
Vector<T, defaultCapacity, Allocator>::Vector(
    Vector&& vector)
    :
    m_numElements(vector.m_numElements),
    m_maxCapacity(vector.m_maxCapacity),
    m_pAllocator(vector.m_pAllocator)
{
    if (vector.m_pData == reinterpret_cast<T*>(vector.m_data)) // Local buffer
    {
        // Data buffer will be using storage from local buffer.
        m_pData = reinterpret_cast<T*>(m_data);

        if (std::is_pod<T>::value)
        {
            // Optimize trivial types by copying local buffer.
            std::memcpy(m_pData, vector.m_pData, sizeof(T) * m_numElements);
        }
        else
        {
            // Move objects from local buffer of a dying vector to local buffer of a new vector.
            for (uint32 idx = 0; idx < m_numElements; ++idx)
            {
                PAL_PLACEMENT_NEW(m_pData + idx) T(Move(vector.m_pData[idx]));
            }
        }
    }
    else // Heap allocation
    {
        // Steal heap allocation from dying vector.
        m_pData = vector.m_pData;

        // After the allocation has been stolen, dying vector is just an empty shell.
        vector.m_pData = nullptr;
        vector.m_numElements = 0;
        vector.m_maxCapacity = 0;
    }
}

} // Util