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filecache.cpp：源码内容
							/* ***** BEGIN LICENSE BLOCK ***** 
 * Version: RCSL 1.0/RPSL 1.0 
 *  
 * Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved. 
 *      
 * The contents of this file, and the files included with this file, are 
 * subject to the current version of the RealNetworks Public Source License 
 * Version 1.0 (the "RPSL") available at 
 * http://www.helixcommunity.org/content/rpsl unless you have licensed 
 * the file under the RealNetworks Community Source License Version 1.0 
 * (the "RCSL") available at http://www.helixcommunity.org/content/rcsl, 
 * in which case the RCSL will apply. You may also obtain the license terms 
 * directly from RealNetworks.  You may not use this file except in 
 * compliance with the RPSL or, if you have a valid RCSL with RealNetworks 
 * applicable to this file, the RCSL.  Please see the applicable RPSL or 
 * RCSL for the rights, obligations and limitations governing use of the 
 * contents of the file.  
 *  
 * This file is part of the Helix DNA Technology. RealNetworks is the 
 * developer of the Original Code and owns the copyrights in the portions 
 * it created. 
 *  
 * This file, and the files included with this file, is distributed and made 
 * available on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 
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 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS 
 * FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 
 * 
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 * 
 * Contributor(s): 
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 * ***** END LICENSE BLOCK ***** */ 
#include "hxtypes.h"
#include "hxcom.h"      // IUnknown
#include "hxiids.h"     // GUIDs
#include "hxslist.h"    // CHXSimpleList
#include "hxthread.h"   // HXMutex
#include "hxstring.h"   // memcpy()
#include "hxcomm.h"     // IHXCommonClassFactory
#include "ihxpckts.h"   // IHXBuffer
#include "hxcache2.h"   // IHXCache2, IHXCacheObject, IHXCacheObjectResponse
#include "filecache.h"
#include "multilog.h"   
#include "mlog_http.h"  // MLOG_HTTP()
/****************************************************************************
 *  CHXFileCacheObject::CHXFileCacheObject
 *
 *  Constructor
 */
CHXFileCacheObject::CHXFileCacheObject(IHXCommonClassFactory* /*IN*/ pClassFactory,
                                       UINT32   /*IN*/      ulFileLength,
                                       char*   /*IN*/       pFileName)
    : m_RefCount                (0),
      m_pCacheObjectResponse    (NULL),
      m_pClassFactory           (NULL),
      m_ulCapacity              (0),
      m_lThreshold              (50),
      m_ulUsedCapacity          (0),
      m_pList                   (NULL),
      m_ulCurrentWriteOffset    (0),
      m_pPendingAddBlock        (NULL),
      m_bInAddBlockDone         (FALSE),
      m_bInReadBlockDone        (FALSE),
      m_pMutex                  (NULL),
      m_ulCurrentReadOffset     (0),
      m_ulFileLength            (0),
      m_pFileName               (NULL),
      m_ulFileWriteOffset       (0),
      m_pCacheFileHandle        (NULL),
      m_ulHighestByteNotRead    (0)
{
    MLOG_HTTP("CHXFileCacheObject::CHXFileCacheObject(FileLen = %u, FileName = %s)n", ulFileLength, pFileName);
    m_pPendingReadInfo.ulOffset = 0;
    m_pPendingReadInfo.ulLength = 0;
    m_pPendingReadInfo.pBlock = NULL;
    if(pClassFactory != NULL)
    {
        m_pClassFactory = pClassFactory;
        m_pClassFactory->AddRef();
    }
    m_ulFileLength = ulFileLength;
    m_pFileName = pFileName;
    m_pList = new CHXSimpleList;
    #if defined(THREADS_SUPPORTED) || defined(_UNIX_THREADS_SUPPORTED)
        HXMutex::MakeMutex(m_pMutex);
    #else
        HXMutex::MakeStubMutex(m_pMutex);
    #endif
}
/****************************************************************************
 *  CHXFileCacheObject::~CHXFileCacheObject
 *
 *  Destructor
 */
CHXFileCacheObject::~CHXFileCacheObject()
{
    MLOG_HTTP("CHXFileCacheObject::~CHXFileCacheObject()n");
    m_pMutex->Lock();
    // Close the cache file and delete if necessary
    if(m_pCacheFileHandle != NULL)
    {
        // If full media clip not played, delete cache file
        if(m_ulHighestByteNotRead != m_ulFileLength)
        {
            fclose(m_pCacheFileHandle);
            remove(m_pFileName);
        }
        else
        {
            _CopyAllDataToFile();
            fclose(m_pCacheFileHandle);
        }
    }
    // Destroy the list
    if(m_pList)
    {
        LISTPOSITION currPos = m_pList->GetHeadPosition();
        Info* currInfo;
        while(currPos != NULL)
        {
            currInfo = (Info *)m_pList->GetNext(currPos);
            currInfo->pBlock->Release();
            delete currInfo;
        }
        delete m_pList;
    }
    m_pMutex->Unlock();
    HX_DELETE(m_pMutex);
} // ~CHXFileCacheObject()
// IUnknown COM Interface Methods
/****************************************************************************
 *  IUnknown::AddRef
 *
 *  This routine increases the object reference count in a thread safe
 *  manner. The reference count is used to manage the lifetime of an object.
 *  This method must be explicitly called by the user whenever a new
 *  reference to an object is used.
 */
STDMETHODIMP_(UINT32) CHXFileCacheObject::AddRef(void)
{
    MLOG_HTTP("CHXFileCacheObject::AddRef()n");
    return InterlockedIncrement(&m_RefCount);
}
/****************************************************************************
 *  IUnknown::Release
 *
 *  This routine decreases the object reference count in a thread safe
 *  manner, and deletes the object if no more references to it exist. It must
 *  be called explicitly by the user whenever an object is no longer needed.
 */
STDMETHODIMP_(UINT32) CHXFileCacheObject::Release(void)
{
    MLOG_HTTP("CHXFileCacheObject::Release()n");
    if (InterlockedDecrement(&m_RefCount) > 0)
    {
	return m_RefCount;
    }
    delete this;
    return 0;
}
/****************************************************************************
 *  IUnknown::QueryInterface
 *
 *  This routine indicates which interfaces this object supports. If a given
 *  interface is supported, the object's reference count is incremented, and
 *  a reference to that interface is returned. Otherwise a NULL object and
 *  error code are returned. This method is called by other objects to
 *  discover the functionality of this object.
 */
STDMETHODIMP CHXFileCacheObject::QueryInterface(REFIID interfaceID,
					       void** ppInterfaceObj)
{
    MLOG_HTTP("CHXFileCacheObject::QueryInterface()n");
    // By definition all COM objects support the IUnknown interface
    if (IsEqualIID(interfaceID, IID_IUnknown))
    {
	AddRef();
	*ppInterfaceObj = (IUnknown*)(IHXCacheObject*)this;
	return HXR_OK;
    }
    // IHXCacheObject interface is supported
    else if (IsEqualIID(interfaceID, IID_IHXCacheObject))
    {
	AddRef();
	*ppInterfaceObj = (IHXCacheObject*)this;
	return HXR_OK;
    }
    // No other interfaces are supported
    *ppInterfaceObj = NULL;
    return HXR_NOINTERFACE;
}
//IHXCacheObject methods
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::Init
 *
 *	Purpose:
 *
 *	    Associates a cache object with the response object
 *	    it should notify of operation completeness.
 */
STDMETHODIMP
CHXFileCacheObject::Init(IHXCacheObjectResponse*   /*IN*/  pCacheObjectResponse,
                         UINT32   /*IN*/      ulCapacity,
                         UINT32   /*IN*/      lThreshold)
{
    MLOG_HTTP("CHXFileCacheObject::Init(Capacity = %u, Threshold = %d)n", ulCapacity, lThreshold);
    HX_RESULT res = HXR_OK;
    if(pCacheObjectResponse != NULL)
    {
        // Release any previous response objects
        if(m_pCacheObjectResponse != NULL)
        {
            m_pCacheObjectResponse->Release();
        }
        m_pCacheObjectResponse = pCacheObjectResponse;
        pCacheObjectResponse->AddRef();
    
    }
    else
    {
        res = HXR_INVALID_PARAMETER;
    }
    m_ulCapacity = ulCapacity;
    if( (lThreshold < 0) || (lThreshold >= 100) ) 
    {
        res = HXR_INVALID_PARAMETER;
    }
    else
    {
        m_lThreshold = lThreshold;
    }
    // Open the cache file for writing.
    m_pCacheFileHandle = fopen(m_pFileName, "wb+");
    if( m_pCacheFileHandle == NULL )
        res = HXR_FAIL;
    m_pCacheObjectResponse->InitDone(res);
    // HXR_OK from this function indicates InitDone() will be called.
    // Since this statement is executed only after the above InitDone()
    // we return HXR_OK instead of res. 
    return HXR_OK;
} // Init()
/************************************************************************
     *	Method:
     *
     *	    IHXCacheObject::GetThreshold
     *
     *	Purpose:
     *
     *	    Obtain the threshold of the cache object.
     */
STDMETHODIMP_(UINT32)
CHXFileCacheObject::GetThreshold(void)
{
    MLOG_HTTP("CHXFileCacheObject::GetThreshold()n"); 
    return m_lThreshold;
} // GetThreshold()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::ChangeThreshold
 *
 *	Purpose:
 *
 *	    The object keeps caching data until it is full (exhausts its 
 *      capacity). Once it is full, it will overwite existing cached data
 *      with new data ONLY if the percentage of cached data which has been
 *      read from the cache using the ReadBlock() method is *greater* than a
 *      given percentage of Capacity.. This percentage is set using the SetThreshold()
 *      method. In case the threshold is exceeded, the oldest added data
 *      (the data with the the least offset) will be discarded and the 
 *      amount of data discarded is so that the remaining cached data just
 *      satisfies the threshold condidtion (approximately).
 *
 *      This cache object is used in the HTTP/1.0 file system plugin for
 *      mobile devices and in this case, the threshold is set to 70%
 *      i.e., utilizedDataPercentage = 0.7
 *
 */
STDMETHODIMP
CHXFileCacheObject::ChangeThreshold(UINT32  /*IN*/	lNewThreshold)
{
    MLOG_HTTP("CHXFileCacheObject::ChangeThreshold(%d)n", lNewThreshold);
    if( (lNewThreshold < 0) || (lNewThreshold >= 100) )
    {
        return HXR_INVALID_PARAMETER;
    }
    m_pMutex->Lock();
    UINT32 lOldThreshold = m_lThreshold;
    m_lThreshold = lNewThreshold;
    HX_RESULT res = _CheckForThresholdCondition();
    if(HXR_OK != res)
    {
        // Revert back as something got messed up.
        m_lThreshold = lOldThreshold;
    }
    m_pMutex->Unlock();
    return res;
} // ChangeThreshold()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::GetCapacity
 *
 *	Purpose:
 *
 *	    Obtain the capacity in bytes of the cache object.
 */
STDMETHODIMP_(UINT32)
CHXFileCacheObject::GetCapacity(void)
{
    MLOG_HTTP("CHXFileCacheObject::GetCapacity()n"); 
    return m_ulCapacity;
} // GetCapacity()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::ChangeCapacity
 *
 *	Purpose:
 *
 *	    Change the capacity of the cache object.
 */
STDMETHODIMP
CHXFileCacheObject::ChangeCapacity(UINT32  /*IN*/	newByteCount) 
{
   MLOG_HTTP("CHXFileCacheObject::ChangeCapacity(%u)n", newByteCount);
   HX_RESULT res = HXR_OK;
    
   m_pMutex->Lock();
   UINT32 ulOldCapacity = m_ulCapacity;
   m_ulCapacity = newByteCount;
   int nExcessData = m_ulUsedCapacity - newByteCount;
   
   if(nExcessData > 0)
   {
       // Discard the excess data writing to the cache file if necessary
       res = _DiscardDataFromHead((UINT32)nExcessData, TRUE);
       if(HXR_OK != res)
       {
           // Revert back to old capacity if you couldn't
           // discard data.
           m_ulCapacity = ulOldCapacity;    
       }
       else
       {
           // Capacity has changed, so threshold might have been exceeded.
           res = _CheckForThresholdCondition();
       }
   }
   m_pMutex->Unlock();
   m_pCacheObjectResponse->ChangeCapacityDone(res);
   
   // HXR_OK from this function indicates ChangeCapacityDone() will be called.
   // Since this statement is executed only after the above ChangeCapacityDone()
   // we return HXR_OK instead of res. 
   return HXR_OK;
} // ChangeCapacity()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::GetUnusedCapacity
 *
 *	Purpose:
 *
 *	    Obtain the unused capacity in bytes of the cache object.
 */
STDMETHODIMP_(UINT32)
CHXFileCacheObject::GetUnusedCapacity()
{
    MLOG_HTTP("CHXFileCacheObject::GetUnusedCapacity()n");
    UINT32 ulUnusedCapacity = 0;
    m_pMutex->Lock();
    // There's data in the cache file which will be used to
    // populate the list. Will accept more data from outside
    // once I use up all data in the file.
    if(m_ulFileWriteOffset > m_ulCurrentWriteOffset)
    {
        ulUnusedCapacity = 0;
    }
    else
    {
        ulUnusedCapacity = m_ulCapacity - m_ulUsedCapacity;
    }
    
    m_pMutex->Unlock();
    return ulUnusedCapacity;
} // GetUnusedCapacity()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::AddBlock
 *
 *	Purpose:
 *
 *	    Adds a block of data to the cache.
 */
STDMETHODIMP
CHXFileCacheObject::AddBlock(IHXBuffer*	/*IN*/	pBlock) 
{
    MLOG_HTTP("CHXFileCacheObject::AddBlock()n");
    if(pBlock == NULL)
    {
        return HXR_INVALID_PARAMETER;
    }
    if(m_pList == NULL)
        return HXR_UNEXPECTED;
            
    if(m_pPendingAddBlock != NULL)
    {
        return HXR_UNEXPECTED;
    }
    else
    {
        m_pPendingAddBlock = pBlock;
        m_pPendingAddBlock->AddRef();
    }
    if(!m_bInAddBlockDone)
    {
        while(m_pPendingAddBlock)
        {
            IHXBuffer* pTempBlock = m_pPendingAddBlock;
            m_pPendingAddBlock = NULL;
            UINT32 ulBlockSize = pTempBlock->GetSize();
            Info *pNewInfo = NULL;
            HX_RESULT res = HXR_OK;
            if(ulBlockSize != 0)
            {
                m_pMutex->Lock(); 
           
                // Can you accomodate this data?
                if(m_ulUsedCapacity + ulBlockSize > m_ulCapacity)
                {
                    pTempBlock->Release();
                    res = HXR_OUTOFMEMORY;
                }
                else
                {
                    pNewInfo = new Info;
                    if(pNewInfo == NULL)
                        res = HXR_OUTOFMEMORY;
                }
                if(HXR_OK == res)
                {
                    // The new block should be contiguous
                    pNewInfo->ulOffset = m_ulCurrentWriteOffset;
                    pNewInfo->ulSize = ulBlockSize;
                    pNewInfo->pBlock = pTempBlock;
                    m_ulUsedCapacity += ulBlockSize;
                    m_ulCurrentWriteOffset += ulBlockSize;
                    m_pList->AddTail( (void *)pNewInfo );
                }
            
                m_pMutex->Unlock();
            }
            else
            {
                pTempBlock->Release();
            }
            m_bInAddBlockDone = TRUE;
            m_pCacheObjectResponse->AddBlockDone(res);
            m_bInAddBlockDone = FALSE;
        } // while
    }
    return HXR_OK;
} // AddBlock()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::VerifyBlock
 *
 *	Purpose:
 *
 *	    Verify that a block of data is in the cache.
 */
STDMETHODIMP
CHXFileCacheObject::VerifyBlock(UINT32	/*IN*/	ulBlockOffset,
			 UINT32	/*IN*/	ulBlockLength)
{
    MLOG_HTTP("CHXFileCacheObject::VeifyBlock()n");
    if(m_pList == NULL)
        return HXR_UNEXPECTED;
    m_pMutex->Lock();
    
    // Critical Section starts
    BOOL bExists = TRUE;
    if(m_ulUsedCapacity == 0)
    {
        bExists = FALSE;
    }
    else
    {
        UINT32 ulLeastOffset = m_ulCurrentWriteOffset - m_ulUsedCapacity;
        UINT32 ulHighestOffset = m_ulCurrentWriteOffset - 1;
        
        BOOL bStartExists = (ulBlockOffset >= ulLeastOffset) && 
                            (ulBlockOffset <= ulHighestOffset);
        BOOL bEndExists = (ulBlockOffset + ulBlockLength - 1 >= ulLeastOffset) &&
                          (ulBlockOffset + ulBlockLength - 1 <= ulHighestOffset);
        bExists = bStartExists && bEndExists;
    }
    // Critical section ends
    m_pMutex->Unlock();
    m_pCacheObjectResponse->VerifyBlockDone(bExists);
    return HXR_OK;
} // VerifyBlock()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::ReadBlock
 *
 *	Purpose:
 *
 *	    Read a block out of the cache.
 */
STDMETHODIMP
CHXFileCacheObject::ReadBlock(UINT32    /*IN*/	ulBlockOffset,
			      UINT32    /*IN*/	ulBlockLength)
{
    MLOG_HTTP("CHXFileCacheObject::ReadBlock(Offset = %u, Length = %u)n", ulBlockOffset, ulBlockLength);
    if(m_pList == NULL)
        return HXR_UNEXPECTED;
    if(m_pPendingReadInfo.pBlock != NULL)
        return HXR_UNEXPECTED;
    m_pClassFactory->CreateInstance(CLSID_IHXBuffer,
                     (void **) &m_pPendingReadInfo.pBlock);
    if(m_pPendingReadInfo.pBlock == NULL)
        return HXR_OUTOFMEMORY;
    HX_RESULT res = m_pPendingReadInfo.pBlock->SetSize(ulBlockLength);
    if(res != HXR_OK)
    {
        m_pPendingReadInfo.pBlock->Release();
        m_pPendingReadInfo.pBlock = NULL;
        return res;
    }
    m_pPendingReadInfo.ulLength = ulBlockLength;
    m_pPendingReadInfo.ulOffset = ulBlockOffset;
    if(!m_bInReadBlockDone)
    {
        while(m_pPendingReadInfo.pBlock)
        {
            HX_RESULT res2 = HXR_OK;
            // To prepare for the possibilty of ReadBlock()
            // being called from ReadBlockDone()
            IHXBuffer* pTempBlock = m_pPendingReadInfo.pBlock;
            m_pPendingReadInfo.pBlock = NULL;
            UINT32 ulTempLength = m_pPendingReadInfo.ulLength;
            m_pPendingReadInfo.ulLength = 0;
            UINT32 ulTempOffset = m_pPendingReadInfo.ulOffset;
            m_pPendingReadInfo.ulOffset = 0;
            m_pMutex->Lock();
            UINT32 ulLeastOffset = m_ulCurrentWriteOffset - m_ulUsedCapacity; 
            UINT32 ulHighestOffset = m_ulCurrentWriteOffset - 1;
            if( (m_ulUsedCapacity == 0) && (m_ulCurrentWriteOffset == 0) )
            {
                res2 = HXR_INCOMPLETE;
                HX_RELEASE(pTempBlock);
                pTempBlock = NULL;
            }
            else if(ulTempOffset < ulLeastOffset)
            {
                res2 = HXR_INCOMPLETE;
                HX_RELEASE(pTempBlock);
                pTempBlock = NULL;
                // Flush data to file and then read the required (past)
                // data from the file.
                _CopyAllDataToFile();
                UINT32 ulGap = ulLeastOffset - ulTempOffset;
                UINT32 ulDiscardData = 0;
                if(ulGap >= m_ulCapacity)
                    ulDiscardData = m_ulUsedCapacity;
                else
                {
                    int nRemovableData = m_ulCurrentWriteOffset - 
                                         (ulTempOffset + m_ulCapacity);
                    ulDiscardData = (nRemovableData > 0)? (UINT32)nRemovableData: 0;
                }
                if(ulDiscardData >0)
                {
                    _DiscardDataFromTail(ulDiscardData, FALSE);
                }
                if(ulGap >= m_ulCapacity)
                {
                    _CopyFromFileToHead(ulTempOffset, m_ulCapacity);
                    m_ulCurrentWriteOffset = ulTempOffset + m_ulCapacity;
                    m_ulCurrentReadOffset = ulTempOffset;
                    m_ulUsedCapacity = m_ulCapacity;
                }
                else
                {
                    m_ulCurrentWriteOffset = ulTempOffset + ulGap + m_ulUsedCapacity;
                    //if(ulDiscardData != 0)
                    //{
                        _CopyFromFileToHead(ulTempOffset, ulGap);
                    //}
                    
                    m_ulCurrentReadOffset = ulTempOffset;
                }
            }
            else if(ulTempOffset > ulHighestOffset)
            {
                res2 = HXR_INCOMPLETE;
                HX_RELEASE(pTempBlock);
                pTempBlock = NULL;
                // If 'forward data' requested, mark all data as read so
                // that old data can be discarded to make space for new data.
                m_ulCurrentReadOffset = ulTempOffset;
                _CheckForThresholdCondition();
            }
            else
            {
                // Fill the pTempBlock with data from the list
            
                UCHAR* ucTempBlockData = pTempBlock->GetBuffer();
                UINT32 ulBytesReadFromList = 0;
                LISTPOSITION currPos = m_pList->GetHeadPosition();
                Info* currInfo;
                while(currPos != NULL)
                {   
                    currInfo = (Info *)m_pList->GetNext(currPos);
                    UINT32 ulCurrLowOffset = currInfo->ulOffset;
                    UINT32 ulCurrHighOffset = currInfo->ulOffset + currInfo->ulSize - 1;
                    UCHAR* ucCurrBlockData = currInfo->pBlock->GetBuffer();
                    if( (ulTempOffset >= ulCurrLowOffset) && (ulTempOffset <= ulCurrHighOffset) )
                    {
                        UINT32 ulMatchSize = ( (ulCurrHighOffset - ulTempOffset + 1) < ulTempLength ) ?
                                                ulCurrHighOffset - ulTempOffset + 1 : ulTempLength;
                        memcpy((void*)(ucTempBlockData + ulBytesReadFromList),
                                (void*)(ucCurrBlockData + ulTempOffset - ulCurrLowOffset), ulMatchSize);
                        ulBytesReadFromList += ulMatchSize;
                        ulTempOffset += ulMatchSize;
                        ulTempLength -= ulMatchSize;
                        if(0 == ulTempLength)
                            break;
                    }
                }
                if(ulTempLength > 0)
                {
                    res2 = HXR_INCOMPLETE;
                    pTempBlock->SetSize(ulBytesReadFromList);   
                }
                else
                {
                    res2 = HXR_OK;
                }
                m_ulCurrentReadOffset = ulTempOffset;
                _CheckForThresholdCondition();
            }
            m_pMutex->Unlock();
            if(m_ulHighestByteNotRead < m_ulCurrentReadOffset)
                m_ulHighestByteNotRead = m_ulCurrentReadOffset;
            m_bInReadBlockDone = TRUE;
            m_pCacheObjectResponse->ReadBlockDone(res2, pTempBlock);
            m_bInReadBlockDone = FALSE;
            
            HX_RELEASE(pTempBlock);
        }
    }
    return HXR_OK;
} // ReadBlock()
/************************************************************************
 *	Method:
 *	    IHXCacheObject::Flush
 *
 *	Purpose:
 *
 *	    Flushes all data to the cache file AND releases all data buffers 
 *          in the memory.After flushing, the object can be used for reading/writing
 *          as before.
 */
STDMETHODIMP
CHXFileCacheObject::Flush(void) 
{
    MLOG_HTTP("CHXFileCacheObject::Flush()n");
    
    if(!m_pList)
        return HXR_UNEXPECTED;
    
    m_pMutex->Lock();
    _DiscardDataFromHead(m_ulUsedCapacity, TRUE);
    m_ulUsedCapacity = 0;
    m_pMutex->Unlock();
    m_pCacheObjectResponse->FlushDone(HXR_OK);
    return HXR_OK;
} // Flush()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::IsFull
 *
 *	Purpose:
 *
 *	    Can the cache object accept any more data for storage?
 */
STDMETHODIMP_(BOOL)
CHXFileCacheObject::IsFull()
{
    MLOG_HTTP("CHXFileCacheObject::IsFull()n");
    if(GetUnusedCapacity() == 0)
        return TRUE;
    else
        return FALSE;
} // IsFull()
/************************************************************************
 *	Method:
 *
 *	    IHXCacheObject::IsEmpty
 *
 *	Purpose:
 *
 *	    Does the cache object have any data stored?
 */
STDMETHODIMP_(BOOL)
CHXFileCacheObject::IsEmpty()
{
    MLOG_HTTP("CHXFileCacheObject::IsEmpty()n");
    if(m_ulUsedCapacity == 0)
        return TRUE;
    else
        return FALSE;
} // IsEmpty()
// Discards exactly 'byteCount' amount of data from the head.
// Note that this method is not thread safe. The caller has to take 
// care of locking common data structures before calling this method.
HX_RESULT CHXFileCacheObject::_DiscardDataFromHead(UINT32 byteCount, BOOL bWriteToFile)
{
    MLOG_HTTP("CHXFileCacheObject::_DiscardDataFromHead(%u, %d)n", byteCount, bWriteToFile);
    HX_RESULT res = HXR_UNEXPECTED;
    UINT32 ulDiscardedData = 0;
    Info *headInfo = NULL;
    LISTPOSITION currHead = m_pList->GetHeadPosition();
    while(currHead != NULL) 
    {
        headInfo = (Info*)m_pList->RemoveHead();
        UINT32 ulHeadBlockOffset = headInfo->ulOffset;
        UINT32 ulHeadBlockSize = headInfo->ulSize;
        // This whole block should be discarded
        if(ulDiscardedData + ulHeadBlockSize <= byteCount)
        {
            if(bWriteToFile == TRUE)
            {
                // If data already written to file, no need to write again.
                if( (m_ulFileWriteOffset >= ulHeadBlockOffset) &&
                    (m_ulFileWriteOffset <= ulHeadBlockOffset + ulHeadBlockSize - 1) )
                {
                    UINT32 ulDataAlreadyWritten = m_ulFileWriteOffset - ulHeadBlockOffset;
                    UINT32 ulDataToWrite = ulHeadBlockSize - ulDataAlreadyWritten;
                    fseek(m_pCacheFileHandle, m_ulFileWriteOffset, SEEK_SET);
                    int nBytesWritten = fwrite( (void*)(headInfo->pBlock->GetBuffer() + ulDataAlreadyWritten),
                                sizeof(UCHAR), ulDataToWrite, m_pCacheFileHandle);
                    fflush(m_pCacheFileHandle);
                    m_ulFileWriteOffset += ulDataToWrite;
                }
            }
            headInfo->pBlock->Release();
            delete headInfo;
            
            ulDiscardedData += ulHeadBlockSize;
        }
        else // Only part of the block needs to be discarded.
        {
            if(ulDiscardedData + ulHeadBlockSize > byteCount) // >>> Redundant condition
            {
                UINT32 ulValidDataSize = (ulDiscardedData + ulHeadBlockSize - byteCount);
                UINT32 ulInvalidDataSize = ulHeadBlockSize - ulValidDataSize;
                if(bWriteToFile == TRUE)
                {
                    // If data already written to file, no need to write again.
                    if( (m_ulFileWriteOffset >= ulHeadBlockOffset) && 
                        (m_ulFileWriteOffset <= ulHeadBlockOffset + ulInvalidDataSize - 1) )
                    {
                        UINT32 ulDataAlreadyWritten = m_ulFileWriteOffset - ulHeadBlockOffset;
                        UINT32 ulDataToWrite = ulInvalidDataSize - ulDataAlreadyWritten;
                        fseek(m_pCacheFileHandle, m_ulFileWriteOffset, SEEK_SET);
                        int nBytesWritten = fwrite( (void*)(headInfo->pBlock->GetBuffer() + ulDataAlreadyWritten),
                                    sizeof(UCHAR), ulDataToWrite, m_pCacheFileHandle);
                        fflush(m_pCacheFileHandle);
                        m_ulFileWriteOffset += ulDataToWrite;
                    }
                    
                }
                Info *pNewInfo = new Info;
                if(pNewInfo == NULL)
                {
                   res = HXR_OUTOFMEMORY;
                   break;
                }
                m_pClassFactory->CreateInstance(CLSID_IHXBuffer,
                                               (void **) &(pNewInfo->pBlock));
                if(pNewInfo->pBlock == NULL)
                    break;
                res = pNewInfo->pBlock->SetSize(ulValidDataSize);
                if(res != HXR_OK)
                    break;
                memcpy( (void*)(pNewInfo->pBlock->GetBuffer()),
                        (void*)(headInfo->pBlock->GetBuffer()+ ulInvalidDataSize),
                        ulValidDataSize );
                pNewInfo->ulOffset = headInfo->ulOffset + ulInvalidDataSize;
                pNewInfo->ulSize = ulValidDataSize;
                m_pList->AddHead( (void *)pNewInfo );
                headInfo->pBlock->Release();
                delete headInfo;
            }
            ulDiscardedData = byteCount;
            headInfo = NULL;
            res = HXR_OK;
            break;
        }
        currHead = m_pList->GetHeadPosition();
    }
    m_ulUsedCapacity -= ulDiscardedData;
    return res;
} // _DiscardDataFromHead()
// Check if utilizedData has exceeded THRESHOLD. If yes, discard 
// appropriate amount of data. Note that this
// method is not thread safe. The caller has to take care of 
// locking common data structures before calling this method.
HX_RESULT CHXFileCacheObject::_CheckForThresholdCondition()
{
    MLOG_HTTP("CHXFileCacheObject::_CheckForThresholdCondition()n");
    if(m_ulUsedCapacity == 0)
    {
        return HXR_OK;
    }
    UINT32 ulLeastOffset = m_ulCurrentWriteOffset - m_ulUsedCapacity;
    UINT32 ulHighestOffset = m_ulCurrentWriteOffset - 1;
    HX_RESULT res = HXR_OK;
    INT32 nExcess = (m_ulCurrentReadOffset - ulLeastOffset) - 
                      (INT32)(m_lThreshold * m_ulCapacity * 0.01);
    if(nExcess > 0)
    {
        if(nExcess > m_ulUsedCapacity)
            nExcess = m_ulUsedCapacity; 
        res = _DiscardDataFromHead(nExcess, TRUE);
        INT32 nExtraFileData = m_ulFileWriteOffset - m_ulCurrentWriteOffset;
        if(nExtraFileData > 0)
        {
            UINT32 ulUnusedCapacity = m_ulCapacity - m_ulUsedCapacity;
            UINT32 ulFileReadData = ((UINT32)nExtraFileData > ulUnusedCapacity) ?
                                      ulUnusedCapacity: nExtraFileData;
            res = _CopyFromFileToTail(m_ulCurrentWriteOffset, ulFileReadData);
        }
    }
    return res;
} // _CheckForThresholdCondition()
// Discards exactly 'byteCount' amount of data from the tail.
// Note that this method is not thread safe. The caller has to take 
// care of locking common data structures before calling this method.
HX_RESULT CHXFileCacheObject::_DiscardDataFromTail(UINT32 byteCount, BOOL bWriteToFile)
{
    MLOG_HTTP("CHXFileCacheObject::_DiscardDataFromTail(%u, %d)n", byteCount, bWriteToFile);
    HX_RESULT res = HXR_OK;
    if( (bWriteToFile) && (m_ulFileWriteOffset < m_ulCurrentWriteOffset) )
    {
        LISTPOSITION currPos = m_pList->GetTailPosition();
        while(currPos != NULL)
        {
            Info* pCurrInfo = (Info*)(m_pList->GetPrev(currPos));
            if( (m_ulFileWriteOffset >= pCurrInfo->ulOffset) &&
                (m_ulFileWriteOffset >= pCurrInfo->ulOffset + pCurrInfo->ulSize - 1) )
            {
                break;
            }
        }
        if(currPos != NULL)
        {
            Info* pCurrInfo = (Info*)(m_pList->GetAtNext(currPos));
            UINT32 ulValidData = m_ulFileWriteOffset - (pCurrInfo->ulOffset);
            UINT32 ulInvalidData = pCurrInfo->ulSize - ulValidData;
            fseek(m_pCacheFileHandle, m_ulFileWriteOffset, SEEK_SET);
            int nBytesWritten = fwrite( (void*)(pCurrInfo->pBlock->GetBuffer() + ulValidData),
                                sizeof(UCHAR), ulInvalidData, m_pCacheFileHandle);
            fflush(m_pCacheFileHandle);
            m_ulFileWriteOffset += ulInvalidData;
            pCurrInfo = (Info*)(m_pList->GetNext(currPos));
            while(pCurrInfo != NULL)
            {
                int nBytesWritten = fwrite( (void*)(pCurrInfo->pBlock->GetBuffer()),
                                sizeof(UCHAR), pCurrInfo->ulSize, m_pCacheFileHandle);
                fflush(m_pCacheFileHandle);
                m_ulFileWriteOffset += pCurrInfo->ulSize;
                pCurrInfo = (Info*)(m_pList->GetNext(currPos));
            }
        }
        else
        {
            res = HXR_UNEXPECTED;
        }
    }
    if(res != HXR_OK)
        return res;
    UINT32 ulDiscardedData = 0;
    Info *tailInfo = NULL;
    res = HXR_UNEXPECTED;
    LISTPOSITION currTail = m_pList->GetTailPosition();
    while(currTail != NULL)
    {
        tailInfo = (Info*)(m_pList->RemoveTail());
        UINT32 ulTailBlockSize = tailInfo->ulSize;
        if(ulDiscardedData + ulTailBlockSize <= byteCount)
        {
            tailInfo->pBlock->Release();
            delete tailInfo;
            
            ulDiscardedData += ulTailBlockSize;
        }
        else
        {
            if(ulDiscardedData + ulTailBlockSize > byteCount)
            {
                UINT32 ulValidDataSize = (ulDiscardedData + ulTailBlockSize - byteCount);
                Info *pNewInfo = new Info;
                if(pNewInfo == NULL)
                {
                   res = HXR_OUTOFMEMORY;
                   break;
                }
                m_pClassFactory->CreateInstance(CLSID_IHXBuffer,
                                               (void **) &(pNewInfo->pBlock));
                if(pNewInfo->pBlock == NULL)
                    break;
                res = pNewInfo->pBlock->SetSize(ulValidDataSize);
                if(res != HXR_OK)
                    break;
                memcpy( (void*)(pNewInfo->pBlock->GetBuffer()),
                        (void*)(tailInfo->pBlock->GetBuffer()),
                        ulValidDataSize );
                pNewInfo->ulOffset = tailInfo->ulOffset;
                pNewInfo->ulSize = ulValidDataSize;
                m_pList->AddTail( (void *)pNewInfo );
                tailInfo->pBlock->Release();
                delete tailInfo;
            }
            ulDiscardedData = byteCount;
            tailInfo = NULL;
            res = HXR_OK;
            break;
        }
        currTail = m_pList->GetTailPosition();
    }
    m_ulUsedCapacity -= ulDiscardedData;
    m_ulCurrentWriteOffset -= ulDiscardedData; 
    return res;
} // _DiscardDataFromTail()
// Copies 'ulSize' amount of data from offset 'ulOffset' from
// the cache file. The blocks are added to the Tail of the list.
// The data is copied in blocks of size determined
// by CAPACITY_BLOCKSIZE_RATIO. Requires that the data is present
// in the file.
HX_RESULT CHXFileCacheObject::_CopyFromFileToTail(UINT32 ulOffset, UINT32 ulSize)
{
    MLOG_HTTP("CHXFileCacheObject::_CopyFromFileToTail(Offset = %u, Size = %u)n", ulOffset, ulSize);
    if(ulSize == 0)
        return HXR_OK;
    m_ulCurrentWriteOffset = ulOffset;
    UINT32 ulBlockSize = m_ulCapacity/CAPACITY_BLOCKSIZE_RATIO;
    UINT32 ulRemainderBlockSize = 0;
    UINT32 ulNumFullBlocks = ulSize/ulBlockSize;
    if((ulSize%ulBlockSize) > 0)
    {
        ulRemainderBlockSize = ulSize - ulNumFullBlocks * ulBlockSize;
    }
    HX_RESULT res = HXR_OK;
    fseek(m_pCacheFileHandle, ulOffset, SEEK_SET);
    if(ulRemainderBlockSize > 0)
    {
        IHXBuffer* pRemainderBlock = NULL;
        m_pClassFactory->CreateInstance(CLSID_IHXBuffer,
                         (void **) &pRemainderBlock);
        if(pRemainderBlock != NULL)
        {
            res = pRemainderBlock->SetSize(ulRemainderBlockSize);
        }
        else
        {
            res = HXR_OUTOFMEMORY;
        }
        if(res == HXR_OK)
        {
            fread( (void*)(pRemainderBlock->GetBuffer()),
                                    sizeof(UCHAR), ulRemainderBlockSize, m_pCacheFileHandle );
            Info* pNewInfo = new Info;
            if(pNewInfo == NULL)
            {
                res = HXR_OUTOFMEMORY;
            }
            else
            {
                // The new block should be contiguous
                pNewInfo->ulOffset = m_ulCurrentWriteOffset;
                pNewInfo->ulSize = ulRemainderBlockSize;
                pNewInfo->pBlock = pRemainderBlock;
                m_pList->AddTail( (void *)pNewInfo );
                m_ulUsedCapacity += ulRemainderBlockSize;
                m_ulCurrentWriteOffset += ulRemainderBlockSize;
            }
        }
    }
    if(res != HXR_OK)
        return res;
    for(int i = 0; i < ulNumFullBlocks; i++)
    {
        IHXBuffer* pTempBlock = NULL;
        m_pClassFactory->CreateInstance(CLSID_IHXBuffer,
                         (void **) &pTempBlock);
        if(pTempBlock != NULL)
        {
            res = pTempBlock->SetSize(ulBlockSize);
        }
        else
        {
            res = HXR_OUTOFMEMORY;
        }
        if(res == HXR_OK)
        {
            fread( (void*)(pTempBlock->GetBuffer()),
                                    sizeof(UCHAR), ulBlockSize, m_pCacheFileHandle );
            Info* pNewInfo = new Info;
            if(pNewInfo == NULL)
            {
                res = HXR_OUTOFMEMORY;
            }
            else
            {
                // The new block should be contiguous
                pNewInfo->ulOffset = m_ulCurrentWriteOffset;
                pNewInfo->ulSize = ulBlockSize;
                pNewInfo->pBlock = pTempBlock;
                m_ulUsedCapacity += ulBlockSize;
                m_ulCurrentWriteOffset += ulBlockSize;
                m_pList->AddTail( (void *)pNewInfo );
            }
        }
    }
    return res;
} // _CopyFromFileToTail()
// Copies 'ulSize' amount of data from offset 'ulOffset' from
// the cache file. The blocks are added to the Head of the list.
// The data is copied in blocks of size determined
// by CAPACITY_BLOCKSIZE_RATIO. Requires that the data is present
// in the file.
HX_RESULT CHXFileCacheObject::_CopyFromFileToHead(UINT32 ulOffset, UINT32 ulSize)
{
    MLOG_HTTP("CHXFileCacheObject::_CopyFromFileToHead(Offset = %u, Size = %u)n", ulOffset, ulSize);
    if(ulSize == 0)
        return HXR_OK;
    UINT32 ulBlockSize = m_ulCapacity/CAPACITY_BLOCKSIZE_RATIO;
    UINT32 ulRemainderBlockSize = 0;
    UINT32 ulNumFullBlocks = ulSize/ulBlockSize;
    if((ulSize%ulBlockSize) > 0)
    {
        ulRemainderBlockSize = ulSize - ulNumFullBlocks * ulBlockSize;
    }
    HX_RESULT res = HXR_OK;
    fseek(m_pCacheFileHandle, ulOffset + ulSize, SEEK_SET);
    UINT32 ulCurrBlockOffset = ulOffset + ulSize;
    if(ulRemainderBlockSize > 0)
    {
        IHXBuffer* pRemainderBlock = NULL;
        m_pClassFactory->CreateInstance(CLSID_IHXBuffer,
                         (void **) &pRemainderBlock);
        if(pRemainderBlock != NULL)
        {
            res = pRemainderBlock->SetSize(ulRemainderBlockSize);
        }
        else
        {
            res = HXR_OUTOFMEMORY;
        }
        if(res == HXR_OK)
        {
            ulCurrBlockOffset -= ulRemainderBlockSize;
            fseek(m_pCacheFileHandle, ulCurrBlockOffset , SEEK_SET);
            fread( (void*)(pRemainderBlock->GetBuffer()),
                                    sizeof(UCHAR), ulRemainderBlockSize, m_pCacheFileHandle );
            fseek(m_pCacheFileHandle, ulCurrBlockOffset , SEEK_SET);
            Info* pNewInfo = new Info;
            if(pNewInfo == NULL)
            {
                res = HXR_OUTOFMEMORY;
            }
            else
            {
                // The new block should be contiguous
                pNewInfo->ulOffset = ulCurrBlockOffset;
                pNewInfo->ulSize = ulRemainderBlockSize;
                pNewInfo->pBlock = pRemainderBlock;
                m_pList->AddHead( (void *)pNewInfo );
                m_ulUsedCapacity += ulRemainderBlockSize;
            }
        }
    }
    if(res != HXR_OK)
        return res;
    for(int i = 0; i < ulNumFullBlocks; i++)
    {
        IHXBuffer* pTempBlock = NULL;
        m_pClassFactory->CreateInstance(CLSID_IHXBuffer,
                         (void **) &pTempBlock);
        if(pTempBlock != NULL)
        {
            res = pTempBlock->SetSize(ulBlockSize);
        }
        else
        {
            res = HXR_OUTOFMEMORY;
        }
        if(res == HXR_OK)
        {
            ulCurrBlockOffset -= ulBlockSize;
            fseek(m_pCacheFileHandle, ulCurrBlockOffset, SEEK_SET);
            fread( (void*)(pTempBlock->GetBuffer()),
                                    sizeof(UCHAR), ulBlockSize, m_pCacheFileHandle );
            fseek(m_pCacheFileHandle, ulCurrBlockOffset, SEEK_SET);
            Info* pNewInfo = new Info;
            if(pNewInfo == NULL)
            {
                res = HXR_OUTOFMEMORY;
            }
            else
            {
                // The new block should be contiguous
                pNewInfo->ulOffset = ulCurrBlockOffset;
                pNewInfo->ulSize = ulBlockSize;
                pNewInfo->pBlock = pTempBlock;
                m_pList->AddHead( (void *)pNewInfo );
                m_ulUsedCapacity += ulBlockSize;
            }
        }
    }
    return res;
} // _CopyFromFileToHead()
// Copy all the data present in the list to the local file
HX_RESULT CHXFileCacheObject::_CopyAllDataToFile()
{
    MLOG_HTTP("CHXFileCacheObject::_CopyAllDataToFile()n");
    if(m_pList == NULL)
        return HXR_UNEXPECTED;
    LISTPOSITION currPos = m_pList->GetHeadPosition();
    Info* pCurrInfo;
    while(currPos != NULL)
    {
        pCurrInfo = (Info *)m_pList->GetNext(currPos);
        UINT32 ulCurrBlockOffset = pCurrInfo->ulOffset;
        UINT32 ulCurrBlockSize = pCurrInfo->ulSize;
        // If data already written to file, no need to write again.
        if( (m_ulFileWriteOffset >= ulCurrBlockOffset) &&
            (m_ulFileWriteOffset <= ulCurrBlockOffset + ulCurrBlockSize - 1) )
        {
            UINT32 ulDataAlreadyWritten = m_ulFileWriteOffset - ulCurrBlockOffset;
            UINT32 ulDataToWrite = ulCurrBlockSize - ulDataAlreadyWritten;
            fseek(m_pCacheFileHandle, m_ulFileWriteOffset, SEEK_SET);
            int nBytesWritten = fwrite( (void*)(pCurrInfo->pBlock->GetBuffer() +
                                        ulDataAlreadyWritten), sizeof(UCHAR), 
                                        ulDataToWrite, m_pCacheFileHandle);
            fflush(m_pCacheFileHandle);
            m_ulFileWriteOffset += ulDataToWrite;
        }
    }
    return HXR_OK;
} // _CopyAllDataToFile()

						