Buffer.h

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//==============================================================================================
//  FILENAME    :   Base.h
//  AUTHOR      :   Wayne Li
//  CREATION    :   9/26/1996
//  Copyright (C) MicroStrategy Incorporated 1996
//  All Rights Reserved
//==============================================================================================
#ifndef MBase_Buffer_h
#define MBase_Buffer_h

#include "PDCHeader/PDCstddef.h"
#include "Base.h"
#ifndef __ANDROID__
#include "Base/Interfaces/BaseException.h"
#endif
#include "Base/Defines/StrongPtr.h"

#include "Base/Base/NewOperator.h"

// Ensure that the new operator for buffer has been defined, and that the new
// operator that reports leaks has been defined.
// If the new operator of buffer is used, but is not defined, it will call the
// placement new operator (MBase::Buffer* will be implicitly upcasted to void*),
// and we will get an AV.
#ifdef WIN32
    #ifndef _BUFFER_NEW_OPERATOR_DEFINED_
        #ifndef _OBJECT_DUMP_NEW_OPERATOR_DEFINED_
            #define _NEW_OPERATOR_UNDEFINED_
            #define new _NEW_OPERATOR_NOT_DEFINED_
        #endif
    #endif
#endif

namespace MBase 
{
    class Buffer
    {
    public:
        enum BlockSizes
        {
            MIN_BLOCK_SIZE = 256,
            NT_BLOCK_SIZE = 4096
        };

        virtual void Delete() throw() = 0;
        
        // Allocates a chunk of memory according to the size. 
        // Any further memory request will be allocated from this chunk until the chunk is used up. 
        // return true if success
        virtual bool Reserve(size_t iSize) = 0;

        // Returns a pointer to the memory (equivalent of doing a new)
        // throws BufferException if buffer was previously locked
        // throws ContractManagerException (defined in BaseMemoryContract.h)
        virtual void* GetMem(size_t iSize) = 0;

        // returns the total memory reserved by the buffer, in KB
        virtual unsigned Int32 GetTotalMemSize() const = 0;

        // returns the total memory reserved AND used by the buffer, in KB
        virtual unsigned Int32 GetAllocMemSize() const = 0;

        //xfan. 4/13/09, TQMS 354241. Add new interface
        virtual unsigned Int64 GetTotalMemSizeInBytes() const = 0;
        virtual unsigned Int64 GetAllocMemSizeInBytes() const = 0;

        // Use this function to make the buffer "read-only"
        // when this function is called the memory contained by the
        // the buffer gets locked from writes
        // throws BufferException if unable to lock
        virtual void WriteLock() = 0;

        // set the maxium limit for the total allocated space size, if the size is over the limit, 
        // the buffer.GetMem operation will throw an BufferException
        // it is currently to be used by SQL Engine only
        virtual void SetTotalAllocatedSpaceLimit(Int64 iLimit) = 0;

//  protected:
        virtual ~Buffer() throw()
        {
        };
    };

    class MemoryContract;

    // Factory Functions

    // xfan, add comments. 12/06/07
    // iSize is the initial block number, iExtSize is each incremental block number. 
    // iBlkSize is block size. 
    // if ibOnPageBoundary is set to true, it will allocate/return memory directly from OS;
    // and the memory will be allocated at least one page.
    // if ibOnPageBoundary is false, it will though the memory menager such as smartheap
    DLL_BASE_EXIM Buffer* CreateBuffer(Int32 iSize,Int32 iExtSize,
                                       Int32 iBlkSize = Buffer::NT_BLOCK_SIZE, 
                                       bool ibOnPageBoundary = false);

    DLL_BASE_EXIM Buffer* CreateBuffer(Int32 iSize,Int32 iExtSize,
                                       MBase::MemoryContract* ipMemoryContract,
                                       Int32 iBlkSize = Buffer::NT_BLOCK_SIZE,
                                       bool ibOnPageBoundary = false);

    typedef StrongPtr<Buffer,DeleteOperatorGeneric<Buffer> > BufferPtr;
#ifndef __ANDROID__
    class BufferException: public BaseException
    {
    };
#endif
}

#endif // MBase_Buffer_h