PoolAllocator.h

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/*  Copyright (C) 2003-2021 Free Electron Organization
    Any use of this software requires a license.  If a valid license
    was not distributed with this file, visit freeelectron.org. */

/** @file */

#ifndef __core_PoolAllocator_h__
#define __core_PoolAllocator_h__

namespace fe
{

struct FE_PA_FREE
{
    void *m_next;
};

struct FE_PA_USED
{
    size_t m_s;
};

#define HDR_TO_BLK(x) ((void *)((char *)x + sizeof(size_t)))
#define BLK_TO_HDR(x) ((void *)((char *)x - sizeof(size_t)))

class FE_DL_EXPORT PoolAllocator : public Allocator
{
    public:
                PoolAllocator(void);
                PoolAllocator(FE_UWORD stride, FE_UWORD slots);
virtual         ~PoolAllocator(void);
virtual void    *allocate(FE_UWORD byteCount);
virtual void    deallocate(void* pMemory);
    private:
        FE_UWORD        m_max;
        void        **m_nfList;
        FE_UWORD        m_stride;
};

inline void *PoolAllocator::allocate(FE_UWORD byteCount)
{
    if(byteCount == 0) { return NULL; }
    size_t s = (byteCount-1)/m_stride;
    if(s < m_max && m_nfList[s])
    {
        void *pBase = m_nfList[s];
        m_nfList[s] = ((FE_PA_FREE *)(pBase))->m_next;
        ((FE_PA_USED *)(pBase))->m_s = s;
        return (void *)(HDR_TO_BLK(pBase));
    }
    else
    {
        void *pBase = fe::allocate(((s+1)*m_stride)+sizeof(FE_UWORD));
        ((FE_PA_USED *)(pBase))->m_s = s;
        return (void *)(HDR_TO_BLK(pBase));
    }
}

inline void PoolAllocator::deallocate(void* pMemory)
{
    FE_UWORD s = ((FE_PA_USED *)BLK_TO_HDR(pMemory))->m_s;
    if(s < m_max)
    {
        void *pBase = BLK_TO_HDR(pMemory);
        ((FE_PA_FREE *)(pBase))->m_next = m_nfList[s];
        m_nfList[s] = pBase;
    }
    else
    {
        fe::deallocate(BLK_TO_HDR(pMemory));
    }
}


} /* namespace */

#endif /* __core_PoolAllocator_h__ */