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大きなデータの設定

SQL Server Native Client OLE DB プロバイダーでは、コンシューマー ストレージ オブジェクトへのポインターを渡すことにより、BLOB データを設定できます。

コンシューマーは、データを保持するストレージ オブジェクトを作成し、このストレージ オブジェクトへのポインターをプロバイダーに渡します。 次に、プロバイダーがコンシューマー ストレージ オブジェクトからデータを読み取り、BLOB 列に書き込みます。

コンシューマーは独自のストレージ オブジェクトへのポインターを渡すために、BLOB 列の値をバインドするアクセサーを作成します。 次に、BLOB 列をバインドするアクセサーを指定して、IRowsetChange::SetData メソッドまたは IRowsetChange::InsertRow メソッドを呼び出します。 このとき、コンシューマーのストレージ オブジェクトのストレージ インターフェイスへのポインターを渡します。

このトピックでは、次の関数で使用可能な機能について説明します。

  • IRowset:SetData

  • ICommand::Execute

  • IRowsetUpdate::Update

大きなデータを設定する方法

コンシューマーは、独自のストレージ オブジェクトへのポインターを渡すために、BLOB 列の値をバインドするアクセサーを作成します。次に、IRowsetChange::SetData メソッドまたは IRowsetChange::InsertRow メソッドを呼び出します。 BLOB データを設定するには、次の手順を実行します。

  1. BLOB 列へのアクセス方法を説明する DBOBJECT 構造体を作成します。 DBOBJECT 構造体の dwFlag 要素に STGM_READ を設定し、iid 要素に IID_ISequentialStream (公開されるインターフェイス) を設定します。

  2. 行セットが更新可能になるように、DBPROPSET_ROWSET プロパティ グループのプロパティを設定します。

  3. DBBINDING 構造体の配列を使用して、各列に 1 つずつ一連のバインドを作成します。 DBBINDING 構造体の wType 要素に DBTYPE_IUNKNOWN を設定し、pObject 要素に作成した DBOBJECT 構造体へのポインターを設定します。

  4. DBBINDINGS 構造体の配列内のバインド情報を使用して、アクセサーを作成します。

  5. GetNextRows を呼び出して、次の行を行セットにフェッチします。 GetData を呼び出して、その行セットからデータを読み取ります。

  6. データ (および長さのインジケーター) を保持するストレージ オブジェクトを作成し、次に BLOB 列をバインドするアクセサーを指定して IRowsetChange::SetData (または IRowsetChange::InsertRow) を呼び出し、データを設定します。

次の例は、BLOB データを設定する方法を示しています。 この例では、テーブルを作成し、サンプル レコードを追加して、行セット内のそのレコードをフェッチし、BLOB フィールドの値を設定しています。

#define UNICODE
#define DBINITCONSTANTS
#define INITGID

#include <windows.h>
#include <stdio.h>
#include <stddef.h>
#include <iostream.h>

#include <oledb.h>
#include <oledberr.h>

#include <sqlncli.h>

#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);

protected:
    //Data

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(void)
{
    return ++m_cRef;
}

ULONG    CSeqStream::Release(void)
{
//    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_s(pv, sizeof(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_s((void*)((BYTE*)m_pBuffer + m_iPos), sizeof((void*)((BYTE*)m_pBuffer + m_iPos)), pv, cb);
    // m_iPos += cb;

    if(pcbWritten)
        *pcbWritten = cb;

    return S_OK;
}
//...........................................................
void main()
{
    CoInitialize(NULL);

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

    struct BLOBDATA
    {
        DBSTATUS            dwStatus;   
        DWORD               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;
    ULONG 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 the Command object.
    hr = GetCommandObject(IID_ICommandText, 
                          (IUnknown**)&pICommandText);
    if (FAILED(hr))
    {
        cout << "Failed to get ICommandText interface.\n";
        // Release any references and return.
        goto Exit;
    } //end if

    // Create table with image column and index.
    hr = CreateTable(pICommandText);
    if (FAILED(hr))
    {
        cout << "Failed to create table.\n";
        // Release any references and return.
        goto Exit;
    } //end if
    
    /*
    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))
    {
        cout << "Failed to get ICommandProperties to set rowset properties.\n";
        // Release any references and return.
        goto Exit;
    } //end if
    hr = pICommandProperties->SetProperties(cPropSets, rgPropSets);
    if (FAILED(hr))
    {
        cout << "Execute failed to set rowset properties.\n";
        // Release any references and return.
        goto Exit;
    } //end if
    
    // Execute a command (SELECT * FROM TestISeqStream).
    hr = pICommandText->SetCommandText(DBGUID_DBSQL,
                                       L"SELECT * FROM TestISeqStream");
    if (FAILED(hr))
    {
        cout << "Failed to set command text SELECT * FROM.\n";
        // Release any references and return.
        goto Exit;
    } //end if

    hr = pICommandText->Execute(NULL, IID_IRowsetChange, NULL, NULL,
                                (IUnknown**)&pIRowsetChange);
    if (FAILED(hr))
    {
        cout << "Failed to execute the command SELECT * FROM.\n";
        // Release any references and return.
        goto Exit;
    } //end if

    // 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))
    {
        cout << "Failed to get IAccessor interface.\n";
        // Release any references and return.
        goto Exit;
    } //end if

    hr = pIAccessor->CreateAccessor(DBACCESSOR_ROWDATA,
                                    cBindings,
                                    rgBindings, 
                                    sizeof(BLOBDATA),
                                    &hAccessor,
                                    rgBindStatus);
    if (FAILED(hr))
    {
        cout << "Failed to create an accessor.\n";
        // Release any references and return.
        goto Exit;
    } //end if 

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

    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.
        cout << "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 in to the 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))
    {
        cout << "Failed to set data.\n";
        // Release any references and return.
        goto Exit;
    } //end if

    hr = pIAccessor->ReleaseAccessor(hAccessor, NULL);
    if (FAILED(hr))
    {
        cout << "Failed to release accessor.\n";
        // Release any references and return.
        goto Exit;
    } //end if
    hr = pIRowset->ReleaseRows(cRowsObtained, 
                            rghRows, 
                            NULL, 
                            NULL, 
                            NULL);
    if (FAILED(hr))
    {
        cout << "Failed to release rows.\n";
        // Release any references and return.
        goto Exit;
    } //end if
Exit:
    // Free up all allocated memory and release interface pointers.

    CoUninitialize();
} //end main.
//..........................................................
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 the property values needed to 
    establish the 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"server");
    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"pubs");
    rgProperties[1].dwOptions = DBPROPOPTIONS_REQUIRED;
    rgProperties[1].colid = DB_NULLID;


    // Username (login).
    rgProperties[2].dwPropertyID = DBPROP_AUTH_USERID;
    rgProperties[2].vValue.vt = VT_BSTR;
    rgProperties[2].vValue.bstrVal = 
                    SysAllocString(L"login");
    rgProperties[2].dwOptions = DBPROPOPTIONS_REQUIRED;
    rgProperties[2].colid = DB_NULLID;

    // Password.
    rgProperties[3].dwPropertyID = DBPROP_AUTH_PASSWORD;
    rgProperties[3].vValue.vt = VT_BSTR;
    rgProperties[3].vValue.bstrVal = 
                    SysAllocString(L"password");
    rgProperties[3].dwOptions = DBPROPOPTIONS_REQUIRED;
    rgProperties[3].colid = DB_NULLID;

    
    /*
    Now that the properties are set, construct the DBPROPSET 
    structure (rgInitPropSet).  The DBPROPSET structure is 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_SQLNCLI10, 
                            NULL, 
                            CLSCTX_INPROC_SERVER,
                            IID_IDBInitialize, 
                            (void**)&pIDBInitialize);
    if(FAILED(hr))
    {
        cout << "Failed to get IDBInitialize interface.\n";
        // Release any references and return.
        goto Exit;

    } //end if

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

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

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

    //Create a session object.
      hr = pIDBInitialize->QueryInterface(
                                IID_IDBCreateSession,
                                (void **)&pIDBCreateSession);
       if(FAILED(hr))
    {
        cout << "Failed to get pIDBCreateSession interface.\n";
        // Release any references and return.
        goto Exit;
    } // end if

       hr = pIDBCreateSession->CreateSession(
                                    NULL, 
                                    IID_IDBCreateCommand,
                                    (IUnknown**)&pIDBCreateCommand);
     if(FAILED(hr))
    {
        cout << "Failed to create session object.\n";
        // Release any references and return.
        goto Exit;
    } // end if

     // Get the CommandText object.
     hr = pIDBCreateCommand->CreateCommand(
                                    NULL, 
                                    riid, 
                                    (IUnknown**)ppIUnknown);
     if(FAILED(hr))
    {
        cout << "Failed to create CommandText object.\n";
        // Release any references and return.
        goto Exit;
    } // end if

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

} //end function
//...............................................................
HRESULT CreateTable(ICommandText* pICommandText)
{
    HRESULT hr = S_OK;

    // Drop the xisting table.
    hr = pICommandText->SetCommandText(
                            DBGUID_DBSQL,
                            L"DROP TABLE TestISeqStream");
    if(FAILED(hr))
    {
        cout << "Failed to set command text DROP TABLE.\n";
        // Release any references and return.
        goto Exit;

    } //end if

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

    // Create a new table.
    hr = pICommandText->SetCommandText(DBGUID_DBSQL,
         L"CREATE TABLE TestISeqStream (col1 int,col2 image)");
    if(FAILED(hr))
    {
        cout << "Failed to set command text CREATE TABLE.\n";
        // Release any references and return.
        goto Exit;
    } // end if

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

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

    hr = pICommandText->Execute(NULL, IID_NULL, NULL, NULL, NULL);
    if(FAILED(hr))
    {
        cout << "Failed to insert record in the table.\n";
        // Release any references and return.
        goto Exit;
    } // end if
   
Exit:
    // Free up all allocated memory and release interface pointers.
     return hr;

} //end function

関連項目

概念

BLOB と OLE オブジェクト

大きな値をとるデータ型の使用