使用ADO实现vc中二进制文件数据的存取

来源：互联网发布：js currenttime 编辑：程序博客网时间：2024/05/22 13:33

转自：http://home.kaoyan.com/home.php?mod=space&uid=2820987&do=blog&id=46560

简述关键代码如下：
1、保存图片数据到数据库
以下是代码片段：
//JPG图片保存到数据库
try
{
_RecordsetPtr pRecordset;
pRecordset.CreateInstance(__uuidof(Recordset));
pRecordset->Open("SELECT * FROM jpg",_variant_t((IDispatch*)pConnection),adOpenStatic,adLockOptimistic,adCmdText);
pRecordset->AddNew();
pRecordset->Fields->Item["jpgid"]->Value = (_variant_t)m_JPGId;//jpgid
VARIANT pvList;
SetPictureToVariant(pvList,(unsigned char *)m_pJPGBuffer);
pRecordset->Fields->Item["jpgimage"]->AppendChunk(pvList); //JPG图像文件
VariantClear(&pvList);

pRecordset->Update();
pRecordset->Close();
AfxMessageBox("JPG图像保存成功！");
m_JPGId == "";
UpdateData(false);
}
catch(...)
{
AfxMessageBox("数据库读取失败");
return;
}

其中SetPictureToVariant如下：
以下是代码片段：
void CBMPinDBDlg::SetPictureToVariant(VARIANT &pvList, unsigned char *sPicture)
{
SAFEARRAYBOUND saBound[1];
saBound[0].cElements = m_nFileLen;
saBound[0].lLbound = 0;
SAFEARRAY *pSA = SafeArrayCreate(VT_UI1, 1, saBound);
for (long l = 0; l < (long)m_nFileLen; l ++)
{
SafeArrayPutElement( pSA, &l, (void*)&sPicture[l]);
}
VariantClear(&pvList);
pvList.vt = VT_UI1 | VT_ARRAY;
pvList.parray = pSA;
}

2、从数据库读取图像文件并且显示在界面
以下是代码片段：
//从数据库里取JPG图像文件
try
{
_RecordsetPtr pRecordset;
char sSql[129];
sprintf(sSql,"SELECT *FROM jpg WHERE jpgid=’%s’",m_JPGId);
pRecordset.CreateInstance(__uuidof(Recordset));
pRecordset->Open(sSql,_variant_t((IDispatch*)pConnection),adOpenStatic,adLockOptimistic,adCmdText);
if (pRecordset->adoEOF)
{
CString str;
str.Format("没有JPGid为: %s 的JPG图像!",m_JPGId );
AfxMessageBox(str);
Invalidate();
m_JPGId = "";
UpdateData(false);
m_EidtJPGId.SetFocus();
return;
}
_variant_t pvList ;
long lDataSize = pRecordset->GetFields()->GetItem("jpgimage")->ActualSize;
m_nFileLen = (DWORD)lDataSize;
if(lDataSize > 0)
{
_variant_t varBLOB;
varBLOB = pRecordset->GetFields()->GetItem("jpgimage")->GetChunk(lDataSize);
//把二进制格式的图片转为图片格式
try
{
if(varBLOB.vt == (VT_ARRAY | VT_UI1))
{
if(m_pJPGBuffer = new char[lDataSize+1])
{
char *pBuf = NULL;
SafeArrayAccessData(varBLOB.parray,(void **)&pBuf);
memcpy(m_pJPGBuffer,pBuf,lDataSize);
SafeArrayUnaccessData (varBLOB.parray);
m_nFileLen = lDataSize;

//m_pJPGBuffer -> pPicture
HGLOBAL hMem = ::GlobalAlloc( GMEM_MOVEABLE, m_nFileLen );
LPVOID lpBuf = ::GlobalLock( hMem );
memcpy(lpBuf,m_pJPGBuffer,m_nFileLen);

::GlobalUnlock( hMem );

if ( CreateStreamOnHGlobal( hMem, TRUE, &pStream ) !=S_OK )
return ;

if ( OleLoadPicture( pStream, m_nFileLen, TRUE, IID_IPicture, ( LPVOID * )&pPicture ) !=S_OK )
return ;

Invalidate();//在界面显示
}
}
}
catch(...)
{
AfxMessageBox("从数据库中读取jpg图像有错！");
return;
}

}

}
catch(...)
{
AfxMessageBox("数据库读取失败");
return;
}

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