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關于用VC進行圖像數據（二進制大對象）存儲數據庫的一點心得

下面給出用VC，VB如何操作圖像文件存取數據庫的原碼，幫助一些還沒有掌握方法的朋友，也請這方面的高手多多指教。（均用ADO連接數據庫）

1. VC把一個文件存入數據庫

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把數據庫中IMAGE字段取出存為文件

_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);

}