PRJ_CANCEL_COMMAND_CB callback function (projectedfslib.h)

Article
10/13/2021

Notifies the provider that an operation by an earlier invocation of a callback should be canceled.

Syntax

PRJ_CANCEL_COMMAND_CB PrjCancelCommandCb;

void PrjCancelCommandCb(
  [in] const PRJ_CALLBACK_DATA *callbackData
)
{...}

Parameters

[in] callbackData

Information about the operation. The following callbackData members are necessary to implement this callback:

CommandId Identifies the operation to be cancelled.

Return value

None

Remarks

Every invocation of a provider callback has a callbackData parameter with a CommandId field. If a provider supplies an implementation of this callback, it should keep track of the CommandId values of callbacks that it processes asynchronously, i.e. callbacks from which it has returned HRESULT_FROM_WIN32(ERROR_IO_PENDING) but not yet completed by calling PrjCompleteCommand. If the provider receives this callback, it indicates that the I/O that caused the earlier callback to be invoked was canceled, either explicitly or because the thread it was issued on terminated. The provider should cancel processing the callback invocation identified by CommandId as soon as possible.

Calling PrjCompleteCommand for the CommandId in this callback's callbackData is not an error, however it is a no-op because the I/O that caused the callback invocation identified by CommandId has already ended.

ProjFS will invoke PRJ_CANCEL_COMMAND_CB for a given CommandId only after the callback to be canceled is invoked. However if the provider is configured to allow more than one concurrently running worker thread, the cancellation and original invocation may run concurrently. The provider must be able to handle this situation.

This callback is optional. If the provider does not supply an implementation of this callback, none of the other callbacks will be cancellable. The provider will process all callbacks synchronously.

Requirements

Requirement	Value
Minimum supported client	Windows 10, version 1809 [desktop apps only]
Minimum supported server	Windows Server [desktop apps only]
Target Platform	Windows
Header	projectedfslib.h

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