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FBX SDK Reference Guide: kcontainerallocators.h Source File

#ifndef _FBXSDK_KCONTAINERALLOCATORS_H_
#define _FBXSDK_KCONTAINERALLOCATORS_H_


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 (collectively the "Data") in these files contain unpublished information 
 proprietary to Autodesk, Inc. and/or its licensors, which is protected by 
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#include <kbaselib_h.h>

#include <klib/kdebug.h>

#include <stdlib.h>

#include <kbaselib_nsbegin.h>

/*

An allocator class for use as a template parameter to one of the
container class (KMap, KSet2, KDynamicArray...) must implement these
methods:

    Constructor(size_t pRecordSize)
        The class constructor. The parameter pRecordSize is the
        size of one record held by the container. This is not
        necessarily the same size as of the value type, since the
        container may wrap the value into a private class.

    void* AllocateRecords(size_t pRecordCount)
        Returns a pointer to a uninitialized continuous block of memory
        able to hold pRecordCount * pRecordSize  bytes. pRecordSize was
        defined in the Constructor description, above.

    void FreeMemory(void* pRecord)
        Frees a block of memory returned by AllocateRecords.

    void Reserve(size_t pRecordCount)
        This tells the allocator that we are about to call AllocateRecords
        one or many times to allocate pRecordCount records.
        This gives the allocator a chance to do whatever it deems necessary
        to optimize subsequent allocations, for example, by preallocating a
        sufficiently large pool of memory.

    size_t GetRecordSize() const
        Returns the size of each record allocated.

    operator=()
        The allocator must have appropriate copy semantics; does not need to
        copy its allocated blocks, but it should adjust its record size.
*/


class KBASELIB_DLL KBaseAllocator
{
public:
    KBaseAllocator(size_t const pRecordSize)
        : mRecordSize(pRecordSize)
    {
    }

    void Reserve(size_t const pRecordCount)
    {
    }

    void* AllocateRecords(size_t const pRecordCount = 1)
    {
        return malloc(pRecordCount * mRecordSize);
    }

    void FreeMemory(void* pRecord)
    {
        free(pRecord);
    }

    size_t GetRecordSize() const
    {
        return mRecordSize;
    }

    // Use default copy / assignment

private:
    size_t mRecordSize;
};

/*
This allocator only frees the allocated memory when it is deleted.
This is a good allocator for building dictionaries, where we only
add things to a container, but never remove them.
*/
class KHungryAllocator
{
public:
    KHungryAllocator(size_t pRecordSize)
        : mRecordSize(pRecordSize)
        , mData(NULL)
        , mRecordPoolSize(0)
    {
    }

    KHungryAllocator(const KHungryAllocator& pOther)
        : mRecordSize(pOther.mRecordSize)
        , mData(0)
        , mRecordPoolSize(pOther.mRecordPoolSize)
    {
    }

    ~KHungryAllocator()
    {
        MemoryBlock* lCurrent = mData;
        MemoryBlock* lNext = lCurrent ? lCurrent->mNextBlock : 0;
        while (lCurrent)
        {
            delete lCurrent;
            lCurrent = lNext;
            lNext = lCurrent ? lCurrent->mNextBlock : 0;
        }
    }

    void Reserve(size_t const pRecordCount)
    {
        MemoryBlock* lMem = new MemoryBlock(pRecordCount * mRecordSize);
        lMem->mNextBlock = mData;
        mData = lMem;
        mRecordPoolSize += pRecordCount;
    }

    void* AllocateRecords(size_t const pRecordCount = 1)
    {
        MemoryBlock* lBlock = mData;
        void* lRecord = NULL;

        while ((lBlock != NULL) &&
            ((lRecord = lBlock->GetChunk(pRecordCount * mRecordSize)) == NULL))
        {
            lBlock = lBlock->mNextBlock;
        }

        if (lRecord == NULL)
        {
            size_t lNumRecordToAllocate = mRecordPoolSize / 8 == 0 ? 2 : mRecordPoolSize / 8;
            if (lNumRecordToAllocate < pRecordCount)
            {
                lNumRecordToAllocate = pRecordCount;
            }
            Reserve(lNumRecordToAllocate);
            lRecord = AllocateRecords(pRecordCount);
        }

        return lRecord;
    }

    void FreeMemory(void* pRecord)
    {
    }

    size_t GetRecordSize() const
    {
        return mRecordSize;
    }

    KHungryAllocator& operator=(const KHungryAllocator& pOther)
    {
        if( this != &pOther )
        {
            // The next call to AllocateRecords() may skip over currently reserved
            // records if the size changes drastically, but otherwise GetChunk()
            // is size-oblivious.
            if( mRecordSize < pOther.mRecordSize )
            {
                mRecordPoolSize = 0;
            }

            mRecordSize = pOther.mRecordSize;
        }

        return(*this);
    }

private:
    class MemoryBlock
    {
    public:
        MemoryBlock(size_t pSize)
            : mNextBlock(NULL)
            , mData(NULL)
            , mFreeData(NULL)
            , mEnd(NULL)
        {
            mData = malloc(pSize);
            mFreeData = mData;
            mEnd = reinterpret_cast<char*>(mData) + pSize;
        };

        ~MemoryBlock()
        {
            free(mData);
        }

        void* GetChunk(size_t const pSize)
        {
            if (reinterpret_cast<char*>(mFreeData) + pSize < mEnd)
            {
                void* lChunk = mFreeData;
                mFreeData = reinterpret_cast<char*>(mFreeData) + pSize;
                return lChunk;
            }

            return NULL;
        }

        MemoryBlock* mNextBlock;
        void* mData;
        void* mFreeData;
        void* mEnd;
    };

    size_t mRecordSize;
    MemoryBlock* mData;
    size_t mRecordPoolSize;
};



#include <kbaselib_nsend.h>

#endif // _FBXSDK_KMAP_H_