IQueueCallbackWrite::OnWrite method (wudfddi.h)

[Warning: UMDF 2 is the latest version of UMDF and supersedes UMDF 1. All new UMDF drivers should be written using UMDF 2. No new features are being added to UMDF 1 and there is limited support for UMDF 1 on newer versions of Windows 10. Universal Windows drivers must use UMDF 2. For more info, see Getting Started with UMDF.]

The OnWrite method is called to handle a write request when an application writes information to a device through the Microsoft Win32 WriteFile or WriteFileEx function.

Syntax

void OnWrite(
  [in] IWDFIoQueue   *pWdfQueue,
  [in] IWDFIoRequest *pWdfRequest,
  [in] SIZE_T        NumOfBytesToWrite
);

Parameters

[in] pWdfQueue

A pointer to the IWDFIoQueue interface for the I/O queue object that the request arrives from.

[in] pWdfRequest

A pointer to the IWDFIoRequest interface that represents the framework request object.

[in] NumOfBytesToWrite

The size, in bytes, of the write buffer for the request.

Return value

None

Remarks

A driver registers the IQueueCallbackWrite interface when the driver calls the IWDFDevice::CreateIoQueue method to create an I/O queue or to configure the default I/O queue.

A driver can implement a single OnWrite method for all I/O queues or separate OnWrite methods for each I/O queue.

The OnWrite method receives every write request type from the queue. (The write request type is identified by the WdfRequestWrite value of the WDF_REQUEST_TYPE enumeration type for the request.) The OnWrite method must process each received write request. For more information about how UMDF drivers process I/O requests, see Processing I/O Requests.

The driver can call the IWDFIoRequest::GetWriteParameters and IWDFIoRequest::GetInputMemory methods to retrieve information about the request and the write buffer.

Requirements

See also

IQueueCallbackWrite

IWDFDevice::CreateIoQueue

IWDFIoQueue

IWDFIoRequest

WDF_REQUEST_TYPE