PoolAllocator.h

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/*
 * Copyright (C) 2012 by
 *   MetraLabs GmbH (MLAB), GERMANY
 * and
 *   Neuroinformatics and Cognitive Robotics Labs (NICR) at TU Ilmenau, GERMANY
 * All rights reserved.
 *
 * Contact: info@mira-project.org
 *
 * Commercial Usage:
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 *   accordance with the commercial license agreement provided with the
 *   software or, alternatively, in accordance with the terms contained in
 *   a written agreement between you and MLAB or NICR.
 *
 * GNU General Public License Usage:
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 *   Foundation and appearing in the file LICENSE.GPL3 included in the
 *   packaging of this file. Please review the following information to
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 *   met: http://www.gnu.org/copyleft/gpl.html.
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#ifndef _MIRA_POOLALLOCATOR_H_
#define _MIRA_POOLALLOCATOR_H_

#include <assert.h>
#include <malloc.h> // for malloc and free

#ifndef Q_MOC_RUN
#include <boost/noncopyable.hpp>
#endif

#include <platform/Types.h>
#include <utils/Foreach.h>
#include <error/Exceptions.h>

namespace mira {


template <typename T>
class PoolAllocator : boost::noncopyable
{
public:

    // STL conform typedefs

    typedef T value_type;

    typedef std::size_t size_type;

    typedef std::ptrdiff_t difference_type;

    typedef T* pointer;

    typedef T& reference;

    typedef const T* const_pointer;

    typedef const T& const_reference;


public:

    PoolAllocator(size_type poolCapacity=32, bool growPools=true, size_type itemSize=sizeof(T)) :
        mFreeList(NULL), mNextCapacity(poolCapacity), mAllocatedBytes(0), mGrowPools(growPools) {
        mItemSize = itemSize > sizeof(FreeListItem*) ? itemSize : sizeof(FreeListItem*);
        newBlock();
    }

    ~PoolAllocator() {
        // free our memory blocks
        foreach(uint8* p, mMemoryBlocks)
            free(p);
    }

    PoolAllocator(PoolAllocator&& other) noexcept :
        mFreeList(NULL), mItemSize(0), mNextCapacity(0), mAllocatedBytes(0), mGrowPools(false) {
        swap(other);
    }

    PoolAllocator& operator=(PoolAllocator&& other) noexcept  {
        swap(other);
        return *this;
    }


    void swap(PoolAllocator& other)
    {
        std::swap(mMemoryBlocks, other.mMemoryBlocks);
        std::swap(mFreeList, other.mFreeList);
        std::swap(mItemSize, other.mItemSize);
        std::swap(mNextCapacity, other.mNextCapacity);
        std::swap(mAllocatedBytes, other.mAllocatedBytes);
        std::swap(mGrowPools, other.mGrowPools);
    }

public: // Interface to get memory usage
    size_type allocatedMemory() const
    {
        return mAllocatedBytes;
    }

    size_type usedMemory() const
    {
        return mAllocatedBytes - unusedMemory();
    }

    size_type unusedMemory() const
    {
        size_type freeBytes = 0;
        FreeListItem* curr = mFreeList;
        while(curr)
        {
            freeBytes += mItemSize;
            curr = curr->next;
        }
        return freeBytes;
    }

public:

    // STL conform interface:

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

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

    size_type max_size() const MIRA_NOEXCEPT_OR_NOTHROW {
        return 1;
    }

    size_type itemSize() const MIRA_NOEXCEPT_OR_NOTHROW {
        return mItemSize;
    }

    pointer allocate (size_type n, const void* hint = 0) {
        if(n!=1)
            return NULL;

        uint8* memory = NULL;

        // we have no more free chunks, reserve a new block
        if(mFreeList==NULL)
            newBlock();

        assert(mFreeList!=NULL);

        // take first element of free list
        memory = reinterpret_cast<uint8*>(mFreeList);
        // next element becomes new head
        mFreeList = mFreeList->next;

        return (pointer) memory;
    }

    void construct (pointer p, const_reference val) {
        T* obj = new(p) T(val); // placement new
    }

    void destroy(T* p) {
        p->~T();
    }

    void deallocate (pointer p, size_type n) {
        if(p==NULL)
            return;
        assert(n==1);
        // the deallocated memory will become a free list item
        FreeListItem* item = reinterpret_cast<FreeListItem*>(p);
    
        // and it becomes the new head of that list (next points to the current head)
        item->next = mFreeList;
        mFreeList = item;
    }

    T* construct() {
        T* obj = allocate(1);
        return new(obj) T();
    }

    T* construct(const_reference val) {
        T* obj = allocate(1);
        return new(obj) T(val);
    }

    void destruct(pointer p) {
        if(p==NULL)
            return;
        destroy(p);
        deallocate(p,1);
    }

private:

    // creates a new big memory block
    void newBlock() {
        const size_type blockSize = mNextCapacity * mItemSize;
        uint8* currentBlock = (uint8*) malloc(blockSize);
        if(currentBlock==NULL)
            MIRA_THROW(XBadAlloc, "Failed to allocate "
                    << blockSize << " bytes of memory");

        // build free list within the allocated block
        FreeListItem* oldHead = mFreeList;

        // head of new free list
        uint8* p = currentBlock;
        FreeListItem* l = reinterpret_cast<FreeListItem*>(p);
        mFreeList = l;
        p+=mItemSize;

        // each element links to the next one
        for(size_type i=1; i<mNextCapacity; ++i, p+=mItemSize)
        {
            l->next = reinterpret_cast<FreeListItem*>(p);
            l = l->next;
        }
        l->next = oldHead;

        mMemoryBlocks.push_back(currentBlock);
        mAllocatedBytes += blockSize;

        if(mGrowPools)
            mNextCapacity = mNextCapacity*2;
    }

private:

    std::list<uint8*> mMemoryBlocks;

    struct FreeListItem {
        FreeListItem* next;
    };
    FreeListItem* mFreeList;

    size_type mItemSize;
    size_type mNextCapacity;
    size_type mAllocatedBytes;
    bool mGrowPools;
};


} // namespace

#endif