glmemorypool.h

/*
Copyright (c) 2000-2003 Lee Thomason (www.grinninglizard.com)
Grinning Lizard Utilities.

This software is provided 'as-is', without any express or implied 
warranty. In no event will the authors be held liable for any 
damages arising from the use of this software.

Permission is granted to anyone to use this software for any 
purpose, including commercial applications, and to alter it and 
redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must 
not claim that you wrote the original software. If you use this 
software in a product, an acknowledgment in the product documentation 
would be appreciated but is not required.

2. Altered source versions must be plainly marked as such, and 
must not be misrepresented as being the original software.

3. This notice may not be removed or altered from any source 
distribution.
*/


#ifndef GRINLIZ_MEMORY_POOL
#define GRINLIZ_MEMORY_POOL

#include <string.h>
#include "gldebug.h"

namespace grinliz {

/*      A memory pool that will dynamically grow as memory is needed.
*/
class MemoryPool
{
  public:
        MemoryPool( const char* _name, unsigned objectSize, unsigned blockSize = 4096 );
        ~MemoryPool();

        void* Alloc() {
                void* ret = 0;

                if ( !head ) {
                        NewBlock();
                        GLASSERT( head );
                }

                ret = head;
                head = head->nextChunk;

                #ifdef DEBUG
                        ++numChunks;
                        memset( ret, 0xaa, chunkSize );
                #endif

                return ret;
        }

        void Free( void* mem ) {
                if ( !mem )
                        return;

                Chunk* chunk = (Chunk*) mem;

                #ifdef DEBUG
                        --numChunks;
                        memset( mem, 0xbb, chunkSize );
                #endif

                chunk->nextChunk = head;
                head = chunk;
        }

        void FreePool();

        #ifdef DEBUG
        unsigned Blocks()       { return numBlocks; }
        unsigned Chunks()       { return numChunks; }
        unsigned MemoryUsed()   { return numBlocks * blockSize; }
        #endif

  private:
        struct Chunk
        {
                Chunk* nextChunk;
        };

        struct Block
        {
                Block* nextBlock;
                Chunk* chunk;           // treated as an array of chunks.
        };

        void NewBlock();

        unsigned chunkSize;                     // size of chunk in bytes
        unsigned blockSize;                     // size of block in bytes
        unsigned chunksPerBlock;
        
        #ifdef DEBUG
        unsigned numBlocks;
        unsigned numChunks;
        #endif
        
        Block* rootBlock;
        Chunk* head;

        const char* name;
};

/*      A memory pool that has a fixed allocation.
        Essentially a cross between a linked list and an array.
*/
template < class T, int COUNT >
class FixedMemoryPool
{
  private:
        struct Chunk
        {
                Chunk* next;
        };

  public:
        FixedMemoryPool()
        {
                GLASSERT( sizeof( T ) >= sizeof( Chunk* ) );
                for( int i=0; i<COUNT-1; ++i )
                {
                        ( (Chunk*)(&memory[i]) )->next = (Chunk*)(&memory[i+1]);
                }
                ( (Chunk*)(&memory[COUNT-1]) )->next = 0;
                root = ( (Chunk*)(&memory[0]) );
                inUse = 0;
        }

        ~FixedMemoryPool()      {}

        T* Alloc()
        {
                T* ret = 0;
                if ( root )
                {
                        ret = (T*) root;
                        root = root->next;
                        ++inUse;
                }
                return ret;
        }

        void Free( T* _mem )
        {
                if ( _mem )
                {
                        Chunk* mem = (Chunk*) _mem;
                        #ifdef DEBUG
                                memset( mem, 0xfe, sizeof( T ) );
                        #endif
                        mem->next = root;
                        root = mem;
                        --inUse;
                }
        }

        unsigned InUse()        {       return inUse; }
        unsigned Remain()       {       return COUNT - inUse; }
        bool     Contains( T* mem )     { return mem >= memory && mem < &memory[COUNT]; }

  private:
        T memory[ COUNT ];
        unsigned inUse;
        Chunk* root;
};


/*      This is memory allocation for when you know exactly how much 
        memory is going to be needed. So it's a way to pre-allocate 
        while still using the new and delete operators.
*/

class LinearMemoryPool
{
  public:
        LinearMemoryPool( unsigned totalMemory );

        ~LinearMemoryPool();

        void* Alloc( unsigned allocate );

        void Free( void* mem )          {}

        bool OutOfMemory()                      { return current == end; }

  public:
        char*   base;
        char*   current;
        char*   end;
};

};

#endif

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