IProgressNotify::OnProgress

Article
11/18/2015

A version of this page is also available for

4/8/2010

This method notifies registered objects and applications of the progress of a downloading operation.

Syntax

HRESULT OnProgress(
  DWORD dwProgressCurrent, 
  DWORD dwProgressMaximum, 
  BOOL fAccurate, 
  BOOL fOwner 
);

Parameters

dwProgressCurrent
[in] Amount of data available.

dwProgressMaximum
[in] Total amount of data to be downloaded.

fAccurate
[in] Values in dwProgressCurrent and dwProgressMaximum are either reliable (TRUE) or unreliable (FALSE).

The FALSE value indicates that control structures for determining the actual position of, or amount of, data yet to be downloaded are not available.

fOwner
[in] Value that indicates whether this IProgressNotify::OnProgress call can control the blocking behavior of the operation.

If TRUE, the caller can use return values from OnProgress to block (STG_S_BLOCK), retry (STG_S_RETRYNOW), or monitor (STG_S_MONITORING) the operation.

If FALSE, the return value from OnProgress has no influence on blocking behavior.

Return Value

This function supports the standard return values E_OUTOFMEMORY, E_UNEXPECTED, E_INVALIDARG, and E_FAIL.

The following table shows the additional return values for this method.

Value	Description
STG_S_RETRYNOW	The caller is to retry the operation immediately. This value is most useful for applications that do blocking from within the callback routine.
STG_S_BLOCK	The caller is to block the download and retry the call as needed to determine if additional data is available. This is the default behavior if no sinks are registered on the connection point.
STG_S_MONITORING	The callback recipient relinquishes control of the downloading process to one of the other objects or applications that have registered progress notification sinks on the same stream. This is useful if the notification sink is interested only in gathering statistics.
E_PENDING	Data is currently unavailable. The caller is to try again after some desired interval. The notification sink returns this value if the asynchronous storage is to operate in non-blocking mode.

Remarks

Sinks may be inherited by any substorage or substream of a given storage. If no sink is registered, the thread will block until the requested data becomes available, or the download is canceled by the downloader.

Where multiple objects or applications have registered progress notification sinks on a single stream, only one of them can control the behavior of a download. Ownership of the download goes to the first sink to register with the storage or stream.

Any advise sinks that may have been inherited from the parent storage (if the storage was created with ASYNC_MODE_COMPATIBILITY).

Any one of the sinks can relinquish control to the next connection point by returning STG_S_MONITORING to the connection point making the current caller.

Once a connection point obtains control (through receiving STG_S_BLOCK or STG_S_RETRYNOW), all subsequent connection points calling IProgressNotify::OnProgress will set fOwner to FALSE.

To determine whether the platform supports this interface, see Determining Supported COM APIs.

Requirements

Header	objidl.h, objidl.idl
Library	ole32.lib, uuid.lib
Windows Embedded CE	Windows CE 3.0 and later
Windows Mobile	Windows Mobile Version 5.0 and later

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