Büyük veri (ole db)

Bu örnek, blob veri kümesi, tablo oluşturma, örnek kayıt, kayıt kümesi içinde ve daha sonra blob alanının değeri fetches eklemek gösterilmiştir. Bu örnek, IA64 üzerinde desteklenmiyor.

Kendi depolama nesneye bir işaretçi geçmek tüketici erişenine blob sütun ve ardından arama değeri bağlar oluşturur IRowsetChange::SetDataya IRowsetChange::InsertRowyöntemleri.

Bu örneği, sen-ebilmek download--dan AdventureWorks örnek veritabanını gerektirir Microsoft SQL Server örnekleri ve topluluk projeler Ana sayfa.

Güvenlik Notu
Mümkünse Windows Kimlik Doğrulaması kullanın. Windows kimlik doğrulaması kimlik bilgilerini zamanında kullanılabilir, istem girmelerini değilse. Kimlik bilgileri bir dosyada saklamak kaçının. Kimlik ederse gerekir, onlarla şifrelemek Win32 şifreleme API.

Yordamlar

blob verileri için

1. blob sütun nasıl erişileceğini açıklayan bir dbobject yapısı oluşturun. Set dwFlag öğesi dbobject yapısı için stgm_read ve IID öğeyi ayarlamak IID_ISequentialStream(maruz arabirim).

2. Satır kümesi güncelleştirilebilir yani dbpropset_rowset özelliği Grup özelliklerini ayarlama.

3. Kümesi oluşturma DBBINDING yapıları dizisi kullanarak bağları (bir her sütun). Set wType dbtype_ıunknown, DBBINDING yapısı öğesi ve pObject öğesi oluşturduğunuz dbobject yapısı üzerine gelin.

4. Bağlama bilgileri yapıları DBBINDINGS dizisi kullanarak erişenine oluşturun.

5. Arama GetNextRowssonraki satır satır getirmek için. Arama GetDatasatır kümesi veri okumaya.

6. Veri kümesi için verileri (ve ayrıca uzunluğu göstergesi) içeren bir depolama nesnesi oluşturun ve sonra arama IRowsetChange::SetData(veya IRowsetChange::InsertRow) blob sütun bağlar erişeni ile.

Örnek

Açıklama

Ole32.lib oleaut32.lib ile derlemek ve c++ aşağıdaki kod listesi yürütün. Bu uygulama için bilgisayarınızın varsayılan bağlar SQL Serverörneği. Bazı Windows işletim sistemlerinde değişiklik (localhost) ya da (Yerel) adına ihtiyacınız olacak, SQL Serverörneği. Adlandırılmış bir örneğine bağlanmak için L"(local) bağlantı dizesini değiştirin" l "(Yerel) \\name" , burada adıdır adlı örneği. Varsayılan olarak, SQL ServerExpress yükler adlandırılmış bir örneğine. Sqlncli.h içeren dizinin, INCLUDE çevre değişkeni içerdiğinden emin olun.

Kodu

// compile with: ole32.lib oleaut32.lib
#define UNICODE
#define DBINITCONSTANTS
#define INITGID
#define OLEDBVER 0x0250  // to include correct interfaces

#include <windows.h>
#include <stdio.h>
#include <stddef.h>
#include <iostream>
#include <oledb.h>
#include <oledberr.h>
#include <SQLNCLI.h>

using namespace std;

#define SAFE_RELEASE(pIUnknown) if(pIUnknown) (pIUnknown)->Release();
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown);
HRESULT CreateTable(ICommandText* pICommandText);

class CSeqStream : public ISequentialStream {
public:
   // Constructors
   CSeqStream();
   virtual ~CSeqStream();

   virtual BOOL Seek(ULONG iPos);
   virtual BOOL Clear();
   virtual BOOL CompareData(void* pBuffer);
   virtual ULONG Length() { return m_cBufSize; };

   virtual operator void* const() { return m_pBuffer; };

   STDMETHODIMP_(ULONG) AddRef(void);
   STDMETHODIMP_(ULONG) Release(void);
   STDMETHODIMP QueryInterface(REFIID riid, LPVOID *ppv);

   STDMETHODIMP Read( 
      /* [out] */ void __RPC_FAR *pv,
      /* [in]  */ ULONG cb,
      /* [out] */ ULONG __RPC_FAR *pcbRead);

   STDMETHODIMP Write( 
      /* [in] */ const void __RPC_FAR *pv,
      /* [in] */ ULONG cb,
      /* [out]*/ ULONG __RPC_FAR *pcbWritten);

private:
   ULONG m_cRef;   // reference count
   void* m_pBuffer;   // buffer
   ULONG m_cBufSize;   // buffer size
   ULONG m_iPos;   // current index position in the buffer
};

// class implementation
CSeqStream::CSeqStream() {
   m_iPos = 0;
   m_cRef = 0;
   m_pBuffer = NULL;
   m_cBufSize = 0;

   // The constructor AddRef's
   AddRef();
}

CSeqStream::~CSeqStream() {
   // Shouldn't have any references left ASSERT(m_cRef == 0);
   CoTaskMemFree(m_pBuffer);
}

ULONG CSeqStream::AddRef() {
   return ++m_cRef;
}

ULONG CSeqStream::Release() {
   // ASSERT(m_cRef);
   if (--m_cRef)
      return m_cRef;

   delete this;
   return 0;
}

HRESULT CSeqStream::QueryInterface(REFIID riid, void** ppv) {
   // ASSERT(ppv);
   *ppv = NULL;

   if (riid == IID_IUnknown)
      *ppv = this;

   if (riid == IID_ISequentialStream)
      *ppv = this;

   if(*ppv) {
      ((IUnknown*)*ppv)->AddRef();
      return S_OK;
   }

   return E_NOINTERFACE;
}

BOOL CSeqStream::Seek(ULONG iPos) {
   // Make sure the desired position is within the buffer
   // ASSERT(iPos == 0 || iPos < m_cBufSize);

   // Reset the current buffer position
   m_iPos = iPos;
   return TRUE;
}

BOOL CSeqStream::Clear() {
   // Frees the buffer
   m_iPos = 0;
   m_cBufSize = 0;

   CoTaskMemFree(m_pBuffer);
   m_pBuffer = NULL;

   return TRUE;
}

BOOL CSeqStream::CompareData(void* pBuffer) {
   // ASSERT(pBuffer);

   // Quick and easy way to compare user buffer with the stream
   return memcmp(pBuffer, m_pBuffer, m_cBufSize) == 0;
}

HRESULT CSeqStream::Read(void *pv, ULONG cb, ULONG* pcbRead) {
   // Parameter checking
   if (pcbRead)
      *pcbRead = 0;

   if (!pv)
      return STG_E_INVALIDPOINTER;

   if (cb == 0)
      return S_OK;

   // Actual code
   ULONG cBytesLeft = m_cBufSize - m_iPos;
   ULONG cBytesRead = cb > cBytesLeft ? cBytesLeft : cb;

   // if no more bytes to retrieve return 
   if (cBytesLeft == 0)
      return S_FALSE; 

   // Copy to users buffer the number of bytes requested or remaining
   memcpy(pv, (void*)((BYTE*)m_pBuffer + m_iPos), cBytesRead);
   m_iPos += cBytesRead;

   if (pcbRead)
      *pcbRead = cBytesRead;

   if (cb != cBytesRead)
      return S_FALSE; 

   return S_OK;
}

HRESULT CSeqStream::Write(const void *pv, ULONG cb, ULONG* pcbWritten) {
   // Parameter checking
   if (!pv)
      return STG_E_INVALIDPOINTER;

   if (pcbWritten)
      *pcbWritten = 0;

   if (cb == 0)
      return S_OK;

   // Enlarge the current buffer
   m_cBufSize += cb;

   // Need to append to the end of the stream
   m_pBuffer = CoTaskMemRealloc(m_pBuffer, m_cBufSize);
   memcpy((void*)((BYTE*)m_pBuffer + m_iPos), pv, cb);
   // m_iPos += cb;

   if (pcbWritten)
      *pcbWritten = cb;

   return S_OK;
}

int main() {
   CoInitialize(NULL);

   DBOBJECT ObjectStruct;
   ObjectStruct.dwFlags = STGM_READ;
   ObjectStruct.iid = IID_ISequentialStream;

   struct BLOBDATA {
      DBSTATUS dwStatus;   
      DBLENGTH dwLength; 
      ISequentialStream* pISeqStream;
   };

   BLOBDATA BLOBGetData;
   BLOBDATA BLOBSetData;

   const ULONG cBindings = 1;
   DBBINDING rgBindings[cBindings]; 
   HRESULT hr = S_OK;

   IAccessor* pIAccessor = NULL;
   ICommandText* pICommandText = NULL;
   ICommandProperties* pICommandProperties = NULL;
   IRowsetChange* pIRowsetChange = NULL;
   IRowset* pIRowset = NULL;
   CSeqStream* pMySeqStream = NULL;

   DBCOUNTITEM cRowsObtained = 0;
   HACCESSOR hAccessor = DB_NULL_HACCESSOR;
   DBBINDSTATUS rgBindStatus[cBindings];
   HROW* rghRows = NULL;

   const ULONG cPropSets = 1;
   DBPROPSET rgPropSets[cPropSets];
   const ULONG cProperties = 1;
   DBPROP rgProperties[cProperties];
   const ULONG cBytes = 10;

   BYTE pBuffer[cBytes];
   ULONG cBytesRead = 0;

   BYTE pReadData[cBytes];   // read BLOB data in this array
   memset(pReadData, 0xAA, cBytes);

   BYTE pWriteData[cBytes];   // write BLOB data from this array
   memset(pWriteData, 'D', cBytes);

   // Get Command object
   hr = GetCommandObject(IID_ICommandText, (IUnknown**)&pICommandText);
   if (FAILED(hr)) {
      printf("Failed to get ICommandText interface.\n");
      // Release any references and return.
      goto Exit;
   }

   // Create table with image column and index
   hr = CreateTable(pICommandText);
   if (FAILED(hr)) {
      printf("Failed to create table.\n");
      // Release any references and return.
      goto Exit;
   }

   // Set the DBPROPSET structure.  It is used to pass an array 
   // of DBPROP structures to SetProperties().
   rgPropSets[0].guidPropertySet = DBPROPSET_ROWSET;
   rgPropSets[0].cProperties = cProperties;
   rgPropSets[0].rgProperties = rgProperties;

   // Now set properties in the property group (DBPROPSET_ROWSET)
   rgPropSets[0].rgProperties[0].dwPropertyID = DBPROP_UPDATABILITY;
   rgPropSets[0].rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
   rgPropSets[0].rgProperties[0].dwStatus = DBPROPSTATUS_OK;
   rgPropSets[0].rgProperties[0].colid = DB_NULLID;
   rgPropSets[0].rgProperties[0].vValue.vt = VT_I4;
   V_I4(&rgPropSets[0].rgProperties[0].vValue) = DBPROPVAL_UP_CHANGE;

   // Set the rowset properties
   hr = pICommandText->QueryInterface(IID_ICommandProperties,
      (void **)&pICommandProperties);

   if (FAILED(hr)) {
      printf("Failed to get ICommandProperties to set rowset properties.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);

   if (FAILED(hr)) {
      printf("Execute failed to set rowset properties.\n");
      // Release any references and return.
      goto Exit;
   }

   // Execute a command (SELECT * FROM TestISeqStream)
   hr = pICommandText->SetCommandText(DBGUID_DBSQL, L"SELECT * FROM TestISeqStream");

   if (FAILED(hr)) {
      printf("Failed to set command text SELECT * FROM.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandText->Execute(NULL, 
      IID_IRowsetChange, 
      NULL, 
      NULL,
      (IUnknown**)&pIRowsetChange);

   if (FAILED(hr)) {
      printf("Failed to execute the command SELECT * FROM.\n");
      // Release any references and return.
      goto Exit;
   }

   // Fill the DBBINDINGS array.
   rgBindings[0].iOrdinal = 2;   // ordinal position
   rgBindings[0].obValue = offsetof(BLOBDATA, pISeqStream);
   rgBindings[0].obLength = offsetof(BLOBDATA, dwLength);
   rgBindings[0].obStatus = offsetof(BLOBDATA, dwStatus);
   rgBindings[0].pTypeInfo = NULL;
   rgBindings[0].pObject = &ObjectStruct;
   rgBindings[0].pBindExt = NULL;
   rgBindings[0].dwPart =  DBPART_VALUE | DBPART_STATUS | DBPART_LENGTH;
   rgBindings[0].dwMemOwner = DBMEMOWNER_CLIENTOWNED;
   rgBindings[0].eParamIO = DBPARAMIO_NOTPARAM;
   rgBindings[0].cbMaxLen = 0; 
   rgBindings[0].dwFlags = 0;
   rgBindings[0].wType = DBTYPE_IUNKNOWN;
   rgBindings[0].bPrecision = 0;
   rgBindings[0].bScale = 0;

   // Create an accessor using the binding information.
   hr = pIRowsetChange->QueryInterface(IID_IAccessor, (void**)&pIAccessor);
   if (FAILED(hr)) {
      printf("Failed to get IAccessor interface.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,
      cBindings,
      rgBindings, 
      sizeof(BLOBDATA),
      &hAccessor,
      rgBindStatus);

   if (FAILED(hr)) {
      printf("Failed to create an accessor.\n");
      // Release any references and return.
      goto Exit;
   }

   // get the first row.
   hr = pIRowsetChange->QueryInterface(IID_IRowset, (void **)&pIRowset);
   if (FAILED(hr)) {
      printf("Failed to get IRowset interface.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIRowset->GetNextRows(NULL, 0, 1, &cRowsObtained, &rghRows);
   hr = pIRowset->GetData(rghRows[0], hAccessor, &BLOBGetData);

   // Verify the retrieved data, only if data is not null.
   if (BLOBGetData.dwStatus == DBSTATUS_S_ISNULL) {
      // Process null data
      printf("Provider returned a null value.\n");
   } 
   else if(BLOBGetData.dwStatus == DBSTATUS_S_OK) {
      // Provider returned a nonNULL value
      BLOBGetData.pISeqStream->Read( pBuffer, cBytes, &cBytesRead);

      if (memcmp(pBuffer, pReadData, cBytes) != 0) {
         // cleanup 
      }

      SAFE_RELEASE(BLOBGetData.pISeqStream);
   }

   // Set up data for SetData.
   pMySeqStream = new CSeqStream();

   // Put data into ISequentialStream object for the provider to write.
   pMySeqStream->Write(pWriteData, cBytes, NULL);

   BLOBSetData.pISeqStream = (ISequentialStream*)pMySeqStream;
   BLOBSetData.dwStatus = DBSTATUS_S_OK;
   BLOBSetData.dwLength = pMySeqStream->Length();

   // Set the data.
   hr = pIRowsetChange->SetData(rghRows[0], hAccessor, &BLOBSetData);
   if (FAILED(hr))     {
      printf("Failed to set data.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);
   if (FAILED(hr)) {
      printf("Failed to release accessor.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIRowset->ReleaseRows(cRowsObtained, rghRows, NULL, NULL, NULL);

   if (FAILED(hr)) {
      printf("Failed to release rows.\n");
      // Release any references and return.
      goto Exit;
   }

Exit:
   // Release all allocated memory and release interface pointers.
   CoUninitialize();
}

HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown) {
   HRESULT hr = S_OK;

   // Local interface pointers, until a connection is made.
   IDBInitialize* pIDBInitialize = NULL;
   IDBProperties*  pIDBProperties = NULL;
   IDBCreateSession* pIDBCreateSession = NULL;
   IDBCreateCommand* pIDBCreateCommand = NULL;

   const ULONG cPropSets = 1;
   DBPROPSET rgPropSets[cPropSets];

   const ULONG cProperties = 4;
   DBPROP rgProperties[cProperties];

   // Initialize property values needed to establish connection.
   for ( ULONG i = 0 ; i < 4 ; i++ )
      VariantInit(&rgProperties[i].vValue);

   // Server name.
   rgProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
   rgProperties[0].vValue.vt = VT_BSTR;

   rgProperties[0].vValue.bstrVal = SysAllocString(L"(local)");
   rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
   rgProperties[0].colid = DB_NULLID;

   // Database.
   rgProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;
   rgProperties[1].vValue.vt = VT_BSTR;
   rgProperties[1].vValue.bstrVal = SysAllocString(L"AdventureWorks");
   rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;
   rgProperties[1].colid = DB_NULLID;

   rgProperties[2].dwPropertyID = DBPROP_AUTH_INTEGRATED;
   rgProperties[2].vValue.vt = VT_BSTR;
   rgProperties[2].vValue.bstrVal = SysAllocString(L"SSPI");
   rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;
   rgProperties[2].colid = DB_NULLID;

   // Properties are now set.  Next, construct DBPROPSET structure (rgInitPropSet) used to pass an 
   // array of DBPROP structures (InitProperties) to the SetProperties method.
   rgPropSets[0].guidPropertySet = DBPROPSET_DBINIT;
   rgPropSets[0].cProperties = cProperties;
   rgPropSets[0].rgProperties = rgProperties;

   // Get the IDBInitialize interface.
   hr = CoCreateInstance(CLSID_SQLNCLI11, 
      NULL, 
      CLSCTX_INPROC_SERVER,
      IID_IDBInitialize, 
      (void**)&pIDBInitialize);

   if (FAILED(hr)) {
      printf("Failed to get IDBInitialize interface.\n");
      // Release any references and return.
      goto Exit;
   }

   // Set initialization properties.
   hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);
   if (FAILED(hr)) {
      printf("Failed to get IDBProperties interface.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIDBProperties->SetProperties(cPropSets, rgPropSets);
   if (FAILED(hr)) {
      printf("Failed to set properties for DBPROPSET_DBINIT.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIDBInitialize->Initialize();
   if (FAILED(hr)) {
      printf("Failed to initialize.\n");
      // Release any references and return.
      goto Exit;
   }

   // Create a session object.
   hr = pIDBInitialize->QueryInterface( IID_IDBCreateSession,
                                        (void **)&pIDBCreateSession);

   if (FAILED(hr)) {
      printf("Failed to get pIDBCreateSession interface.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIDBCreateSession->CreateSession( NULL, IID_IDBCreateCommand, (IUnknown**)&pIDBCreateCommand);

   if (FAILED(hr)) {
      printf("Failed to create session object.\n");
      // Release any references and return.
      goto Exit;
   }

   // Get CommandText object
   hr = pIDBCreateCommand->CreateCommand( NULL, riid, (IUnknown**)ppIUnknown);

   if (FAILED(hr)) {
      printf("Failed to create CommandText object.\n");
      // Release any references and return.
      goto Exit;
   }

   return hr;

Exit:
   // Free up all allocated memory and release interface pointers.
   return hr;
}

HRESULT CreateTable(ICommandText* pICommandText) {
   HRESULT hr = S_OK;

   // drop the table "TestISeqStream" if the table exists.
   hr = pICommandText->SetCommandText( DBGUID_DBSQL, L"if object_id('TestISeqStream') is not null drop table TestISeqStream");
   if (FAILED(hr)) {
      printf("Failed to set command text DROP TABLE.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
   if (FAILED(hr)) {
      printf("Failed to drop the table.\n");
      // Release any references and return.
      goto Exit;
   }

   // Create a new table.
   hr = pICommandText->SetCommandText(DBGUID_DBSQL, 
      L"CREATE TABLE TestISeqStream (col1 int,col2 image)");

   if (FAILED(hr)) {
      printf("Failed to set command text CREATE TABLE.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
   if (FAILED(hr)) {
      printf("Failed to create table.\n");
      // Release any references and return.
      goto Exit;
   }

   // Insert one row into table.
   hr = pICommandText->SetCommandText(DBGUID_DBSQL,
      L"INSERT INTO TestISeqStream(col1,col2) VALUES (1,0xAAAAAAAAAAAAAAAAA)");
   if (FAILED(hr)) {
      printf("Failed to set command text INSERT INTO.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);

   if (FAILED(hr)) {
      printf("Failed to insert record in the table.\n");
      // Release any references and return.
      goto Exit;
   }

Exit:
   // Release all allocated memory and release interface pointers.
   return hr;
}

// compile with: ole32.lib oleaut32.lib
#define UNICODE
#define DBINITCONSTANTS
#define INITGID
#define OLEDBVER 0x0250  // to include correct interfaces

#include <windows.h>
#include <stdio.h>
#include <stddef.h>
#include <iostream>
#include <oledb.h>
#include <oledberr.h>
#include <SQLNCLI.h>

using namespace std;

#define SAFE_RELEASE(pIUnknown) if(pIUnknown) (pIUnknown)->Release();
HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown);
HRESULT CreateTable(ICommandText* pICommandText);

class CSeqStream : public ISequentialStream {
public:
   // Constructors
   CSeqStream();
   virtual ~CSeqStream();

   virtual BOOL Seek(ULONG iPos);
   virtual BOOL Clear();
   virtual BOOL CompareData(void* pBuffer);
   virtual ULONG Length() { return m_cBufSize; };

   virtual operator void* const() { return m_pBuffer; };

   STDMETHODIMP_(ULONG) AddRef(void);
   STDMETHODIMP_(ULONG) Release(void);
   STDMETHODIMP QueryInterface(REFIID riid, LPVOID *ppv);

   STDMETHODIMP Read( 
      /* [out] */ void __RPC_FAR *pv,
      /* [in]  */ ULONG cb,
      /* [out] */ ULONG __RPC_FAR *pcbRead);

   STDMETHODIMP Write( 
      /* [in] */ const void __RPC_FAR *pv,
      /* [in] */ ULONG cb,
      /* [out]*/ ULONG __RPC_FAR *pcbWritten);

private:
   ULONG m_cRef;   // reference count
   void* m_pBuffer;   // buffer
   ULONG m_cBufSize;   // buffer size
   ULONG m_iPos;   // current index position in the buffer
};

// class implementation
CSeqStream::CSeqStream() {
   m_iPos = 0;
   m_cRef = 0;
   m_pBuffer = NULL;
   m_cBufSize = 0;

   // The constructor AddRef's
   AddRef();
}

CSeqStream::~CSeqStream() {
   // Shouldn't have any references left ASSERT(m_cRef == 0);
   CoTaskMemFree(m_pBuffer);
}

ULONG CSeqStream::AddRef() {
   return ++m_cRef;
}

ULONG CSeqStream::Release() {
   // ASSERT(m_cRef);
   if (--m_cRef)
      return m_cRef;

   delete this;
   return 0;
}

HRESULT CSeqStream::QueryInterface(REFIID riid, void** ppv) {
   // ASSERT(ppv);
   *ppv = NULL;

   if (riid == IID_IUnknown)
      *ppv = this;

   if (riid == IID_ISequentialStream)
      *ppv = this;

   if(*ppv) {
      ((IUnknown*)*ppv)->AddRef();
      return S_OK;
   }

   return E_NOINTERFACE;
}

BOOL CSeqStream::Seek(ULONG iPos) {
   // Make sure the desired position is within the buffer
   // ASSERT(iPos == 0 || iPos < m_cBufSize);

   // Reset the current buffer position
   m_iPos = iPos;
   return TRUE;
}

BOOL CSeqStream::Clear() {
   // Frees the buffer
   m_iPos = 0;
   m_cBufSize = 0;

   CoTaskMemFree(m_pBuffer);
   m_pBuffer = NULL;

   return TRUE;
}

BOOL CSeqStream::CompareData(void* pBuffer) {
   // ASSERT(pBuffer);

   // Quick and easy way to compare user buffer with the stream
   return memcmp(pBuffer, m_pBuffer, m_cBufSize) == 0;
}

HRESULT CSeqStream::Read(void *pv, ULONG cb, ULONG* pcbRead) {
   // Parameter checking
   if (pcbRead)
      *pcbRead = 0;

   if (!pv)
      return STG_E_INVALIDPOINTER;

   if (cb == 0)
      return S_OK;

   // Actual code
   ULONG cBytesLeft = m_cBufSize - m_iPos;
   ULONG cBytesRead = cb > cBytesLeft ? cBytesLeft : cb;

   // if no more bytes to retrieve return 
   if (cBytesLeft == 0)
      return S_FALSE; 

   // Copy to users buffer the number of bytes requested or remaining
   memcpy(pv, (void*)((BYTE*)m_pBuffer + m_iPos), cBytesRead);
   m_iPos += cBytesRead;

   if (pcbRead)
      *pcbRead = cBytesRead;

   if (cb != cBytesRead)
      return S_FALSE; 

   return S_OK;
}

HRESULT CSeqStream::Write(const void *pv, ULONG cb, ULONG* pcbWritten) {
   // Parameter checking
   if (!pv)
      return STG_E_INVALIDPOINTER;

   if (pcbWritten)
      *pcbWritten = 0;

   if (cb == 0)
      return S_OK;

   // Enlarge the current buffer
   m_cBufSize += cb;

   // Need to append to the end of the stream
   m_pBuffer = CoTaskMemRealloc(m_pBuffer, m_cBufSize);
   memcpy((void*)((BYTE*)m_pBuffer + m_iPos), pv, cb);
   // m_iPos += cb;

   if (pcbWritten)
      *pcbWritten = cb;

   return S_OK;
}

int main() {
   CoInitialize(NULL);

   DBOBJECT ObjectStruct;
   ObjectStruct.dwFlags = STGM_READ;
   ObjectStruct.iid = IID_ISequentialStream;

   struct BLOBDATA {
      DBSTATUS dwStatus;   
      DBLENGTH dwLength; 
      ISequentialStream* pISeqStream;
   };

   BLOBDATA BLOBGetData;
   BLOBDATA BLOBSetData;

   const ULONG cBindings = 1;
   DBBINDING rgBindings[cBindings]; 
   HRESULT hr = S_OK;

   IAccessor* pIAccessor = NULL;
   ICommandText* pICommandText = NULL;
   ICommandProperties* pICommandProperties = NULL;
   IRowsetChange* pIRowsetChange = NULL;
   IRowset* pIRowset = NULL;
   CSeqStream* pMySeqStream = NULL;

   DBCOUNTITEM cRowsObtained = 0;
   HACCESSOR hAccessor = DB_NULL_HACCESSOR;
   DBBINDSTATUS rgBindStatus[cBindings];
   HROW* rghRows = NULL;

   const ULONG cPropSets = 1;
   DBPROPSET rgPropSets[cPropSets];
   const ULONG cProperties = 1;
   DBPROP rgProperties[cProperties];
   const ULONG cBytes = 10;

   BYTE pBuffer[cBytes];
   ULONG cBytesRead = 0;

   BYTE pReadData[cBytes];   // read BLOB data in this array
   memset(pReadData, 0xAA, cBytes);

   BYTE pWriteData[cBytes];   // write BLOB data from this array
   memset(pWriteData, 'D', cBytes);

   // Get Command object
   hr = GetCommandObject(IID_ICommandText, (IUnknown**)&pICommandText);
   if (FAILED(hr)) {
      printf("Failed to get ICommandText interface.\n");
      // Release any references and return.
      goto Exit;
   }

   // Create table with image column and index
   hr = CreateTable(pICommandText);
   if (FAILED(hr)) {
      printf("Failed to create table.\n");
      // Release any references and return.
      goto Exit;
   }

   // Set the DBPROPSET structure.  It is used to pass an array 
   // of DBPROP structures to SetProperties().
   rgPropSets[0].guidPropertySet = DBPROPSET_ROWSET;
   rgPropSets[0].cProperties = cProperties;
   rgPropSets[0].rgProperties = rgProperties;

   // Now set properties in the property group (DBPROPSET_ROWSET)
   rgPropSets[0].rgProperties[0].dwPropertyID = DBPROP_UPDATABILITY;
   rgPropSets[0].rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
   rgPropSets[0].rgProperties[0].dwStatus = DBPROPSTATUS_OK;
   rgPropSets[0].rgProperties[0].colid = DB_NULLID;
   rgPropSets[0].rgProperties[0].vValue.vt = VT_I4;
   V_I4(&rgPropSets[0].rgProperties[0].vValue) = DBPROPVAL_UP_CHANGE;

   // Set the rowset properties
   hr = pICommandText->QueryInterface(IID_ICommandProperties,
      (void **)&pICommandProperties);

   if (FAILED(hr)) {
      printf("Failed to get ICommandProperties to set rowset properties.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);

   if (FAILED(hr)) {
      printf("Execute failed to set rowset properties.\n");
      // Release any references and return.
      goto Exit;
   }

   // Execute a command (SELECT * FROM TestISeqStream)
   hr = pICommandText->SetCommandText(DBGUID_DBSQL, L"SELECT * FROM TestISeqStream");

   if (FAILED(hr)) {
      printf("Failed to set command text SELECT * FROM.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandText->Execute(NULL, 
      IID_IRowsetChange, 
      NULL, 
      NULL,
      (IUnknown**)&pIRowsetChange);

   if (FAILED(hr)) {
      printf("Failed to execute the command SELECT * FROM.\n");
      // Release any references and return.
      goto Exit;
   }

   // Fill the DBBINDINGS array.
   rgBindings[0].iOrdinal = 2;   // ordinal position
   rgBindings[0].obValue = offsetof(BLOBDATA, pISeqStream);
   rgBindings[0].obLength = offsetof(BLOBDATA, dwLength);
   rgBindings[0].obStatus = offsetof(BLOBDATA, dwStatus);
   rgBindings[0].pTypeInfo = NULL;
   rgBindings[0].pObject = &ObjectStruct;
   rgBindings[0].pBindExt = NULL;
   rgBindings[0].dwPart =  DBPART_VALUE | DBPART_STATUS | DBPART_LENGTH;
   rgBindings[0].dwMemOwner = DBMEMOWNER_CLIENTOWNED;
   rgBindings[0].eParamIO = DBPARAMIO_NOTPARAM;
   rgBindings[0].cbMaxLen = 0; 
   rgBindings[0].dwFlags = 0;
   rgBindings[0].wType = DBTYPE_IUNKNOWN;
   rgBindings[0].bPrecision = 0;
   rgBindings[0].bScale = 0;

   // Create an accessor using the binding information.
   hr = pIRowsetChange->QueryInterface(IID_IAccessor, (void**)&pIAccessor);
   if (FAILED(hr)) {
      printf("Failed to get IAccessor interface.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,
      cBindings,
      rgBindings, 
      sizeof(BLOBDATA),
      &hAccessor,
      rgBindStatus);

   if (FAILED(hr)) {
      printf("Failed to create an accessor.\n");
      // Release any references and return.
      goto Exit;
   }

   // get the first row.
   hr = pIRowsetChange->QueryInterface(IID_IRowset, (void **)&pIRowset);
   if (FAILED(hr)) {
      printf("Failed to get IRowset interface.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIRowset->GetNextRows(NULL, 0, 1, &cRowsObtained, &rghRows);
   hr = pIRowset->GetData(rghRows[0], hAccessor, &BLOBGetData);

   // Verify the retrieved data, only if data is not null.
   if (BLOBGetData.dwStatus == DBSTATUS_S_ISNULL) {
      // Process null data
      printf("Provider returned a null value.\n");
   } 
   else if(BLOBGetData.dwStatus == DBSTATUS_S_OK) {
      // Provider returned a nonNULL value
      BLOBGetData.pISeqStream->Read( pBuffer, cBytes, &cBytesRead);

      if (memcmp(pBuffer, pReadData, cBytes) != 0) {
         // cleanup 
      }

      SAFE_RELEASE(BLOBGetData.pISeqStream);
   }

   // Set up data for SetData.
   pMySeqStream = new CSeqStream();

   // Put data into ISequentialStream object for the provider to write.
   pMySeqStream->Write(pWriteData, cBytes, NULL);

   BLOBSetData.pISeqStream = (ISequentialStream*)pMySeqStream;
   BLOBSetData.dwStatus = DBSTATUS_S_OK;
   BLOBSetData.dwLength = pMySeqStream->Length();

   // Set the data.
   hr = pIRowsetChange->SetData(rghRows[0], hAccessor, &BLOBSetData);
   if (FAILED(hr))     {
      printf("Failed to set data.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);
   if (FAILED(hr)) {
      printf("Failed to release accessor.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIRowset->ReleaseRows(cRowsObtained, rghRows, NULL, NULL, NULL);

   if (FAILED(hr)) {
      printf("Failed to release rows.\n");
      // Release any references and return.
      goto Exit;
   }

Exit:
   // Release all allocated memory and release interface pointers.
   CoUninitialize();
}

HRESULT GetCommandObject(REFIID riid, IUnknown** ppIUnknown) {
   HRESULT hr = S_OK;

   // Local interface pointers, until a connection is made.
   IDBInitialize* pIDBInitialize = NULL;
   IDBProperties*  pIDBProperties = NULL;
   IDBCreateSession* pIDBCreateSession = NULL;
   IDBCreateCommand* pIDBCreateCommand = NULL;

   const ULONG cPropSets = 1;
   DBPROPSET rgPropSets[cPropSets];

   const ULONG cProperties = 4;
   DBPROP rgProperties[cProperties];

   // Initialize property values needed to establish connection.
   for ( ULONG i = 0 ; i < 4 ; i++ )
      VariantInit(&rgProperties[i].vValue);

   // Server name.
   rgProperties[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
   rgProperties[0].vValue.vt = VT_BSTR;

   rgProperties[0].vValue.bstrVal = SysAllocString(L"(local)");
   rgProperties[0].dwOptions = DBPROPOPTIONS_REQUIRED;
   rgProperties[0].colid = DB_NULLID;

   // Database.
   rgProperties[1].dwPropertyID = DBPROP_INIT_CATALOG;
   rgProperties[1].vValue.vt = VT_BSTR;
   rgProperties[1].vValue.bstrVal = SysAllocString(L"AdventureWorks");
   rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;
   rgProperties[1].colid = DB_NULLID;

   rgProperties[2].dwPropertyID = DBPROP_AUTH_INTEGRATED;
   rgProperties[2].vValue.vt = VT_BSTR;
   rgProperties[2].vValue.bstrVal = SysAllocString(L"SSPI");
   rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;
   rgProperties[2].colid = DB_NULLID;

   // Properties are now set.  Next, construct DBPROPSET structure (rgInitPropSet) used to pass an 
   // array of DBPROP structures (InitProperties) to the SetProperties method.
   rgPropSets[0].guidPropertySet = DBPROPSET_DBINIT;
   rgPropSets[0].cProperties = cProperties;
   rgPropSets[0].rgProperties = rgProperties;

   // Get the IDBInitialize interface.
   hr = CoCreateInstance(CLSID_SQLNCLI11, 
      NULL, 
      CLSCTX_INPROC_SERVER,
      IID_IDBInitialize, 
      (void**)&pIDBInitialize);

   if (FAILED(hr)) {
      printf("Failed to get IDBInitialize interface.\n");
      // Release any references and return.
      goto Exit;
   }

   // Set initialization properties.
   hr = pIDBInitialize->QueryInterface(IID_IDBProperties, (void **)&pIDBProperties);
   if (FAILED(hr)) {
      printf("Failed to get IDBProperties interface.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIDBProperties->SetProperties(cPropSets, rgPropSets);
   if (FAILED(hr)) {
      printf("Failed to set properties for DBPROPSET_DBINIT.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIDBInitialize->Initialize();
   if (FAILED(hr)) {
      printf("Failed to initialize.\n");
      // Release any references and return.
      goto Exit;
   }

   // Create a session object.
   hr = pIDBInitialize->QueryInterface( IID_IDBCreateSession,
                                        (void **)&pIDBCreateSession);

   if (FAILED(hr)) {
      printf("Failed to get pIDBCreateSession interface.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pIDBCreateSession->CreateSession( NULL, IID_IDBCreateCommand, (IUnknown**)&pIDBCreateCommand);

   if (FAILED(hr)) {
      printf("Failed to create session object.\n");
      // Release any references and return.
      goto Exit;
   }

   // Get CommandText object
   hr = pIDBCreateCommand->CreateCommand( NULL, riid, (IUnknown**)ppIUnknown);

   if (FAILED(hr)) {
      printf("Failed to create CommandText object.\n");
      // Release any references and return.
      goto Exit;
   }

   return hr;

Exit:
   // Free up all allocated memory and release interface pointers.
   return hr;
}

HRESULT CreateTable(ICommandText* pICommandText) {
   HRESULT hr = S_OK;

   // drop the table "TestISeqStream" if the table exists.
   hr = pICommandText->SetCommandText( DBGUID_DBSQL, L"if object_id('TestISeqStream') is not null drop table TestISeqStream");
   if (FAILED(hr)) {
      printf("Failed to set command text DROP TABLE.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
   if (FAILED(hr)) {
      printf("Failed to drop the table.\n");
      // Release any references and return.
      goto Exit;
   }

   // Create a new table.
   hr = pICommandText->SetCommandText(DBGUID_DBSQL, 
      L"CREATE TABLE TestISeqStream (col1 int,col2 image)");

   if (FAILED(hr)) {
      printf("Failed to set command text CREATE TABLE.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
   if (FAILED(hr)) {
      printf("Failed to create table.\n");
      // Release any references and return.
      goto Exit;
   }

   // Insert one row into table.
   hr = pICommandText->SetCommandText(DBGUID_DBSQL,
      L"INSERT INTO TestISeqStream(col1,col2) VALUES (1,0xAAAAAAAAAAAAAAAAA)");
   if (FAILED(hr)) {
      printf("Failed to set command text INSERT INTO.\n");
      // Release any references and return.
      goto Exit;
   }

   hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);

   if (FAILED(hr)) {
      printf("Failed to insert record in the table.\n");
      // Release any references and return.
      goto Exit;
   }

Exit:
   // Release all allocated memory and release interface pointers.
   return hr;
}