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IWMSDataSourcePlugin::OpenDirectory

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IWMSDataSourcePlugin::OpenDirectory

The OpenDirectory method opens a directory data container.

Syntax

  HRESULT OpenDirectory(
  IWMSCommandContext*  pCommandContext,
  IWMSContext*  pUserContext,
  IWMSContext*  pPresentationContext,
  LPWSTR  pszContainerName,
  DWORD  dwFlags,
  IWMSBufferAllocator*  pBufferAllocator,
  IWMSDataSourcePluginCallback*  pCallback,
  QWORD  qwContext
);

Parameters

pCommandContext

[in] Pointer to an IWMSCommandContext interface that contains a command context.

pUserContext

[in] Pointer to an IWMSContext object that contains a user context.

pPresentationContext

[in] Pointer to an IWMSContext interface that contains a presentation context.

pszContainerName

[in] Pointer to a null-terminated string containing the directory name that the server resolved from the requested URL. This includes the scheme type, as in file://C:\wmpub\wmroot\.

dwFlags

[in] DWORD containing a member of the WMS_DATA_CONTAINER_OPEN_FLAGS enumeration type that indicates the type of access requested. This must be a bitwise OR of one or more of the following values.

Values Description
WMS_DATA_CONTAINER_READ_ACCESS The server has requested read access.
WMS_DATA_CONTAINER_WRITE_ACCESS The server has requested write access.
WMS_DATA_CONTAINER_CREATE_NEW_CONTAINER The server has requested that a new data container be created.
WMS_DATA_CONTAINER_ALLOW_BUFFER_IO Buffered data does not need to be page-aligned.

pBufferAllocator

[in] Pointer to an IWMSBufferAllocator interface that can be used by the data source plug-in to allocate additional buffers for reading or writing data.

pCallback

[in] Pointer to an IWMSDataSourcePluginCallback interface. The plug-in calls IWMSDataSourcePluginCallback::OnOpenDirectory to return a result to the server.

qwContext

[in] QWORD containing a value defined by the server to identify which OpenDirectory request the plug-in is responding to when it calls IWMSDataSourcePluginCallback::OnOpenDirectory. The plug-in must pass this value back unaltered.

Return Values

If the method succeeds, the plug-in must return S_OK. To report an error, the plug-in can return any HRESULT other than S_OK. If the plug-in uses the IWMSEventLog interface to log error information directly to the Windows Event Viewer, it is recommended that it return NS_E_PLUGIN_ERROR_REPORTED. Typically, the server attempts to make plug-in error information available to the server object model, the Windows Event Viewer, and the troubleshooting list in the details pane of the Windows Media Services MMC. However, if the plug-in uses the IWMSEventLog interface to send custom error information to the Windows Event Viewer, returning NS_E_PLUGIN_ERROR_REPORTED stops the server from also logging to the event viewer. For more information about retrieving plug-in error information, see Identifying Plug-in Errors.

Example Code

HRESULT STDMETHODCALLTYPE 
CDataSourcePlugin::OpenDirectory( 
                    IWMSCommandContext *pCommandContext,
                    IWMSContext *pUserContext,
                    IWMSContext *pPresentationContext,
                    LPWSTR pszContainerName,
                    DWORD dwFlags,
                    IWMSBufferAllocator *pBufferAllocator,
                    IWMSDataSourcePluginCallback *pCallback,
                    QWORD qwContext
                    )
{
    HRESULT hr = S_OK;
    CDirectoryImpl *pDirectory = NULL;

    // TODO: Allocate a CDirectoryImpl object. The
    // CDirectoryImpl object is user-defined
    // and implements the IWMSDirectory interface.
    // pDirectory points to the object.

    hr = pDirectory->Initialize( 
                            pUserContext,
                            pszContainerName,
                            this,
                            pCallback,
                            qwContext
                            );
    if (FAILED(hr)) goto EXIT;

    hr = pDirectory->Release();
    if (FAILED(hr)) goto EXIT;

EXIT:
    // TODO: Release temporary objects.
    return( hr );
}

// Create a CDirectory object and a method, Initialize(), to 
// enumerate the files in a directory and store information
// about them in a linked list of CDirectoryInfo objects. The 
// CDirectory and CDirectoryInfo objects are user-defined, and 
// the CDirectory object implements the IWMSDirectory interface.
CDirectory::Initialize(
                    IWMSContext *pUserContext,
                    LPWSTR pszContainerName,
                    CNTFSStorageSystem *pOwnerStorageSystem,
                    IWMSDataSourcePluginCallback *pCallback,
                    QWORD qwContext
                    )
{
    HRESULT hr = S_OK;
    HRESULT hr = S_OK;
    WCHAR *pszNtfsPathname;
    size_t sFileName;
    DWORD dwFileAttributes;
    DWORD dwIndex;
    HANDLE hFileEnum = INVALID_HANDLE_VALUE;
    BOOL fSuccess = FALSE;
    WIN32_FIND_DATA FileInfo;

    // Parse the path name to remove the scheme type and
    // use the GetFileAttributes() function to determine
    // whether the path identifies a directory.
    pszNtfsPathname = pszContainerName + URL_SCHEME_LENGTH;    
    dwFileAttributes = GetFileAttributes( pszNtfsPathname );
    if( !( FILE_ATTRIBUTE_DIRECTORY & dwFileAttributes ) )
    {
        hr = HRESULT_FROM_WIN32( ERROR_DIRECTORY );
    }

    // Add the global wildcard character '*' to the end
    // of the directory name.
    sFileName = wcslen( pszNtfsPathname );
    pSearchDirName = new WCHAR[ sFileName + 8 ];
    pSearchDirName[sFileName] = '*';
    pSearchDirName[sFileName + 1] = '\0';

    // Find the first entry in the directory.
    hFileEnum = FindFirstFileW( m_pSearchDirName, &FileInfo );

    dwIndex = 0;
    fSuccess = TRUE;

    while ( TRUE )
    {

        // TODO: Determine whether you have reached the end of 
        // the directory items. If so, break.

        // If the directory item is empty or '.' or '..' or a hidden file,
        // skip it, get the next file and start the loop again.
        if( ( '\0' == FileInfo.cFileName[0] )
            || ( ( '.' == FileInfo.cFileName[0] ) 
                          && ('\0' == FileInfo.cFileName[1] ) )
            || ( ( '.' == FileInfo.cFileName[0] ) 
                          && ( '.' == FileInfo.cFileName[1] )
                          && ( '\0' == FileInfo.cFileName[2] ) )
            || ( FileInfo.dwFileAttributes & FILE_ATTRIBUTE_HIDDEN ) )
        {
            fSuccess = FindNextFileW( hFileEnum, &FileInfo );
            continue;
        }

        // TODO: Retrieve information about each file, such as
        // the name and size, and save it in a linked list of 
        // user-defined CDirectoryInfo objects. In this example,
        // the CDirectoryInfo class contains four data members
        // that save information about a file:
        //     CDirectoryInfo() 
        //     { 
        //     m_cRef = 1;          // Reference count.
        //     m_pszwName = NULL;   // File name.
        //     m_qwSize = 0;        // File size.
        //     m_pNext = NULL;      // Pointer to next CDirectoryInfo.
        //     }

        // Increment the index and find the next file.
        dwIndex++;
        fSuccess = FindNextFileW( hFileEnum, &FileInfo );
    }

    // Callback to the server.
    hr = pCallback->OnOpenDirectory( hr, this, qwContext );
    if (FAILED(hr)) goto EXIT;

    // Because errors are passed through the callback, return S_OK.
    return( S_OK );

EXIT:
    // TODO: Release temporary objects.
}

Requirements

Header: datacontainer.h.

Library: WMSServerTypeLib.dll.

Platform: Windows Server 2003, Enterprise Edition; Windows Server 2003, Datacenter Edition; Windows Server 2008.

See Also

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