JUCE/modules/juce_core/containers/juce_ArrayAllocationBase.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

//==============================================================================
/**
    Implements some basic array storage allocation functions.

    This class isn't really for public use - it's used by the other
    array classes, but might come in handy for some purposes.

    It inherits from a critical section class to allow the arrays to use
    the "empty base class optimisation" pattern to reduce their footprint.

    @see Array, OwnedArray, ReferenceCountedArray
*/
template <class ElementType, class TypeOfCriticalSectionToUse>
class ArrayAllocationBase  : public TypeOfCriticalSectionToUse
{
public:
    //==============================================================================
    /** Creates an empty array. */
    ArrayAllocationBase() noexcept
        : numAllocated (0)
    {
    }

    /** Destructor. */
    ~ArrayAllocationBase() noexcept
    {
    }

    ArrayAllocationBase (ArrayAllocationBase<ElementType, TypeOfCriticalSectionToUse>&& other) noexcept
        : elements (static_cast<HeapBlock<ElementType>&&> (other.elements)),
          numAllocated (other.numAllocated)
    {
    }

    ArrayAllocationBase& operator= (ArrayAllocationBase<ElementType, TypeOfCriticalSectionToUse>&& other) noexcept
    {
        elements = static_cast<HeapBlock<ElementType>&&> (other.elements);
        numAllocated = other.numAllocated;
        return *this;
    }

    //==============================================================================
    /** Changes the amount of storage allocated.

        This will retain any data currently held in the array, and either add or
        remove extra space at the end.

        @param numElements  the number of elements that are needed
    */
    void setAllocatedSize (const int numElements)
    {
        if (numAllocated != numElements)
        {
            if (numElements > 0)
                elements.realloc ((size_t) numElements);
            else
                elements.free();

            numAllocated = numElements;
        }
    }

    /** Increases the amount of storage allocated if it is less than a given amount.

        This will retain any data currently held in the array, but will add
        extra space at the end to make sure there it's at least as big as the size
        passed in. If it's already bigger, no action is taken.

        @param minNumElements  the minimum number of elements that are needed
    */
    void ensureAllocatedSize (const int minNumElements)
    {
        if (minNumElements > numAllocated)
            setAllocatedSize ((minNumElements + minNumElements / 2 + 8) & ~7);

        jassert (numAllocated <= 0 || elements != nullptr);
    }

    /** Minimises the amount of storage allocated so that it's no more than
        the given number of elements.
    */
    void shrinkToNoMoreThan (const int maxNumElements)
    {
        if (maxNumElements < numAllocated)
            setAllocatedSize (maxNumElements);
    }

    /** Swap the contents of two objects. */
    void swapWith (ArrayAllocationBase <ElementType, TypeOfCriticalSectionToUse>& other) noexcept
    {
        elements.swapWith (other.elements);
        std::swap (numAllocated, other.numAllocated);
    }

    //==============================================================================
    HeapBlock<ElementType> elements;
    int numAllocated;

private:
    JUCE_DECLARE_NON_COPYABLE (ArrayAllocationBase)
};

} // namespace juce