MemoryPool.h

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// Copyright Onix Solutions Limited [OnixS]. All rights reserved.
//
// This software owned by Onix Solutions Limited [OnixS] and is
// protected by copyright law and international copyright treaties.
//
// Access to and use of the software is governed by the terms of the applicable
// OnixS Software Services Agreement (the Agreement) and Customer end user license
// agreements granting a non-assignable, non-transferable and non-exclusive license
// to use the software for it's own data processing purposes under the terms defined
// in the Agreement.
//
// Except as otherwise granted within the terms of the Agreement, copying or
// reproduction of any part of this source code or associated reference material
// to any other location for further reproduction or redistribution, and any
// amendments to this copyright notice, are expressly prohibited.
//
// Any reproduction or redistribution for sale or hiring of the Software not in
// accordance with the terms of the Agreement is a violation of copyright law.
//

#pragma once

#if defined(ONIXS_CMEMDH_ENABLE_TRACING)
#  include <ostream>
#endif

#include <OnixS/CME/MDH/Bootstrap.h>

ONIXS_CMEMDH_NAMESPACE_BEGIN

/// Memory pool abstraction.
///
/// Defines interface for memory block
/// allocation and disposing.
class ONIXS_CMEMDH_EXPORTED MemoryPool
{
public:
    /// Releases given instance.
    virtual void release() = 0;

    /// Allocates memory block of given size.
    virtual void* allocate(size_t) = 0;

    /// Releases previously allocated memory block.
    virtual void deallocate(void*) = 0;

#if defined(ONIXS_CMEMDH_ENABLE_TRACING)
    virtual void trace(std::ostream&) = 0;
#endif

protected:
    /// Default initialization.
    ///
    /// Instance construction is
    /// assumed through descendants.
    MemoryPool() {}

    /// Destruction is through descendants.
    virtual ~MemoryPool() {}

private:
    // Copies are disallowed.
    MemoryPool(const MemoryPool&) {}

    // Assignment is disallowed.
    MemoryPool& operator=(const MemoryPool&)
    {
        return *this;
    }
};

// Implements STL allocator over MemoryPool.
template <class Object>
class MemoryPoolAllocator
{
public:
    typedef Object value_type;
    typedef Object* pointer;
    typedef const Object* const_pointer;

    typedef Object& reference;
    typedef const Object& const_reference;

    typedef std::size_t size_type;
    typedef std::ptrdiff_t difference_type;

    template <class Other>
    struct rebind
    {
        typedef MemoryPoolAllocator<Other> other;
    };

    MemoryPoolAllocator()
        : pool_(ONIXS_CMEMDH_NULLPTR)
    {
    }

    MemoryPoolAllocator(MemoryPool& memoryPool)
        : pool_(&memoryPool)
    {
    }

    MemoryPoolAllocator(const MemoryPoolAllocator& other)
        : pool_(other.pool_)
    {
    }

    template <class Other>
    MemoryPoolAllocator(const MemoryPoolAllocator<Other>& other)
        : pool_(&other.memoryPool())
    {
    }

    ~MemoryPoolAllocator() {}

    MemoryPool& memoryPool() const
    {
        return *pool_;
    }

    pointer address(reference obj) const
    {
        return &obj;
    }

    const_pointer address(const_reference x) const
    {
        return &x;
    }

    pointer allocate(size_type qty)
    {
        assert(ONIXS_CMEMDH_NULLPTR != pool_);

        return static_cast<pointer>(pool_->allocate(qty * sizeof(value_type)));
    }

    void deallocate(pointer block, size_type)
    {
        assert(ONIXS_CMEMDH_NULLPTR != pool_);

        pool_->deallocate(block);
    }

    void construct(pointer block, const value_type& obj)
    {
        new (block) value_type(obj);
    }

    void destroy(pointer obj)
    {
        obj->~value_type();
        (void) obj;
    }

    size_type max_size() const
    {
        return static_cast<size_type>(-1) / sizeof(value_type);
    }

    MemoryPoolAllocator& operator=(const MemoryPoolAllocator& other)
    {
        pool_ = other.pool_;

        return *this;
    }

    template <class Other>
    MemoryPoolAllocator& operator=(const MemoryPoolAllocator<Other>& other)
    {
        pool_ = &other.memoryPool();

        return *this;
    }

private:
    MemoryPool* pool_;
};

template <class Object, class OtherObject>
inline bool operator==(const MemoryPoolAllocator<Object>& left, const MemoryPoolAllocator<OtherObject>& right)
{
    return (&left.memoryPool() == &right.memoryPool());
}

template <class Object, class OtherObject>
inline bool operator!=(const MemoryPoolAllocator<Object>& left, const MemoryPoolAllocator<OtherObject>& right)
{
    return (&left.memoryPool() != &right.memoryPool());
}

/// Constructs a memory pool instance
/// according to the given configuration.
ONIXS_CMEMDH_EXPORTED
MemoryPool* makeMemoryPool(size_t, size_t, size_t, size_t);

ONIXS_CMEMDH_NAMESPACE_END