程序问题:可以从SQL数据库中获取图片字段的,但获取以后的文件和存放在数据库字段中的文件的前2个字节(16位)不同,其他都相同,请问这是什么原因?程序如下
::CoInitialize(NULL);
_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=kn;Data Source=andrew");
try
{
//Open a connection
pConnection.CreateInstance(__uuidof(Connection));
hr = pConnection->Open(strCnn,"","",NULL);
pRs.CreateInstance(__uuidof(Recordset));
pRs->Open("select * from users where id=2",_variant_t((IDispatch *) pConnection,true),adOpenKeyset,adLockOptimistic,adCmdText);
//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);
CFile outFile("d:\\3.TXT",CFile::modeCreate|CFile::modeWrite);
LPSTR buffer = (LPSTR)GlobalLock((HGLOBAL)pBuf);
outFile.WriteHuge(buffer,lDataLength);
GlobalUnlock((HGLOBAL)pBuf);
outFile.Close();
SafeArrayUnaccessData (varBLOB.parray);
}
}
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);
}
pRs->Close();
pConnection->Close();
::CoUninitialize();
::CoInitialize(NULL);
_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=kn;Data Source=andrew");
try
{
//Open a connection
pConnection.CreateInstance(__uuidof(Connection));
hr = pConnection->Open(strCnn,"","",NULL);
pRs.CreateInstance(__uuidof(Recordset));
pRs->Open("select * from users where id=2",_variant_t((IDispatch *) pConnection,true),adOpenKeyset,adLockOptimistic,adCmdText);
//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);
CFile outFile("d:\\3.TXT",CFile::modeCreate|CFile::modeWrite);
LPSTR buffer = (LPSTR)GlobalLock((HGLOBAL)pBuf);
outFile.WriteHuge(buffer,lDataLength);
GlobalUnlock((HGLOBAL)pBuf);
outFile.Close();
SafeArrayUnaccessData (varBLOB.parray);
}
}
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);
}
pRs->Close();
pConnection->Close();
::CoUninitialize();
放到if循环的里面