关于用VC进行图像数据（二进制大对象）存储数据库的一点心得

关于用VC进行图像数据（二进制大对象）存储数据库的一点心得

下面给出用VC，VB如何操作图像文件存取数据库的原码，帮助一些还没有掌握方法的朋友，也请这方面的高手多多指教。（均用ADO连接数据库）

1. VC把一个文件存入数据库

CFile imagefile;
   if ( 0   ==  imagefile.Open( " d:\\user\\bmp.bmp " ,CFile::modeRead))
      return ;
  _RecordsetPtr pRs  =  NULL;             
  _ConnectionPtr pConnection  =  NULL;
  _variant_t varChunk;
  HRESULT hr;
  BYTE *  pbuf;
   long  nLength  =  imagefile.GetLength();
  pbuf  =   new  BYTE[nLength + 2 ];
   if (pbuf  ==  NULL)
      return ;                              // allocate memory error;
  imagefile.Read(pbuf,nLength);           // read the file into memory

  BYTE  * pBufEx;
  pBufEx  =  pbuf;
   // build a SAFFERRAY
  SAFEARRAY *  psa;
  SAFEARRAYBOUND rgsabound[ 1 ];
  rgsabound[ 0 ].lLbound  =   0 ;
  rgsabound[ 0 ].cElements  =  nLength;
  psa  =  SafeArrayCreate(VT_UI1,  1 , rgsabound);

   for  ( long  i  =   0 ; i  <  nLength; i ++ )
       SafeArrayPutElement (psa,  & i, pBufEx ++ );
  VARIANT varBLOB;
  varBLOB.vt  =  VT_ARRAY  |  VT_UI1;
  varBLOB.parray  =  psa;

  _bstr_t strCnn( " Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=CUSTOM;Data Source=SERVER " );    
     try
     {
        //Open a connection
        pConnection.CreateInstance(__uuidof(Connection));
        hr = pConnection->Open(strCnn,"","",NULL);   //Connect a DataBase
        pRs.CreateInstance(__uuidof(Recordset));
        pRs->Open("CustomInfo",_variant_t((IDispatch *) pConnection,true),adOpenKeyset,adLockOptimistic,adCmdTable);  //Open a Table
 
//      pRs->AddNew();        
        pRs->Fields->GetItem("Image")->AppendChunk(varBLOB);        
        pRs->Update();
        pRs->Close();
        pConnection->Close();
 }
     catch (_com_error  & e)
     {
        // Notify the user of errors if any.

        _bstr_t bstrSource(e.Source());
        _bstr_t bstrDescription(e.Description());
        CString sError;
        sError.Format("Source : %s \n Description : %s\n",(LPCSTR)bstrSource,(LPCSTR)bstrDescription);
        AfxMessageBox(sError);     
 }

 2. VC把数据库中IMAGE字段取出存为文件

    _RecordsetPtr pRs  =  NULL;
    _ConnectionPtr pConnection  =  NULL;
    _variant_t varChunk;
    HRESULT hr;
    VARIANT varBLOB;
    _bstr_t strCnn( " Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=CUSTOM;Data Source=SERVER " );    
     try
     {
        //Open a connection
        pConnection.CreateInstance(__uuidof(Connection));
        hr = pConnection->Open(strCnn,"","",NULL);        
        pRs.CreateInstance(__uuidof(Recordset));
        pRs->Open("CustomInfo",_variant_t((IDispatch *) pConnection,true),adOpenKeyset,adLockOptimistic,adCmdTable);
       //read  data  
       long lDataLength = pRs->Fields->GetItem("Image")->ActualSize;
       varBLOB = pRs->GetFields()->GetItem("Image")->GetChunk(lDataLength);
      if(varBLOB.vt == (VT_ARRAY | VT_UI1))        
     {
            BYTE *pBuf = NULL;   
            pBuf = (BYTE*)GlobalAlloc(GMEM_FIXED,lDataLength);
            SafeArrayAccessData(varBLOB.parray,(void **)pBuf); 
            //Build a File in Windows Temp Directory
            char tmpPath[_MAX_PATH+1];
            GetTempPath(_MAX_PATH,tmpPath);
            CString strFileName = "temp.bmp";
            strFileName = tmpPath+strFileName;
                                      
            CFile outFile(strFileName,CFile::modeCreate|CFile::modeWrite);

            LPSTR buffer = (LPSTR)GlobalLock((HGLOBAL)pBuf);
            outFile.WriteHuge(buffer,lDataLength);
            GlobalUnlock((HGLOBAL)pBuf);
            outFile.Close();           
            SafeArrayUnaccessData (varBLOB.parray);
       }

        pRs->Close();
        pConnection->Close();
     }
     catch (_com_error  & e)
     {
        // Notify the user of errors if any.
        _bstr_t bstrSource(e.Source());
        _bstr_t bstrDescription(e.Description());
        CString sError;
        sError.Format("Source : %s \n Description : %s\n",(LPCSTR)bstrSource,(LPCSTR)bstrDescription);
        AfxMessageBox(sError);     
 }  

转自： http://dev.rdxx.com/VC/VCDB/2001-10/6/024749171.shtml