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IWMDMOperation::BeginRead (deprecated)

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This is preliminary documentation and subject to change.

This topic documents a feature of the Windows Media Device Manager SDK. We recommend that you migrate your application to use the Windows Portable Devices API. For more information, see the Windows Portable Devices SDK.

The BeginRead method indicates that a "read from device" action is beginning. Windows Media Device Manager only calls this method if the application calls IWMDMStorageControl::Read and passes in this IWMDMOperation interface.

Syntax

HRESULT BeginRead();

Parameters

This method takes no parameters.

Return Values

The application should return one of the following HRESULT values.

Return code Description
S_OK The read operation should continue.
WMDM_E_USER_CANCELLED The read operation should be cancelled without finishing.
E_FAIL An unspecified error occurred, and the read operation should be cancelled without finishing.

If the application returns either E_FAIL or WMDM_E_USER_CANCELLED, the Windows Media Device Manager will call the End method to indicate that the process has been terminated. If the application is using block mode and returns WMDM_E_USER_CANCELLED, then Windows Media Device Manager will return that error to the application.

Remarks

This method is called just before the Windows Media Device Manager calls IWMDMOperation::TransferObjectData.

Example Code

The following C++ code example implements the BeginRead method and outputs a message when a read-from-device action is beginning.

HRESULT BeginRead()
{
    // TODO: Display the message: "IWMDMOperation event--BeginRead."

    // If the global handle of the source file is uninitialized, fail.
    if (m_File == INVALID_HANDLE_VALUE)
        return E_FAIL;

    // Global status to let TransferObjectData know what kind of
    // operation is happening.
    m_OperationStatus = OPERATION_READ;
    return S_OK;
}

Requirements

Header: Defined in mswmdm.h.

Library: mssachlp.lib

See Also