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IWDFIoRequest::GetReadParameters method (wudfddi.h)

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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 GetReadParameters method retrieves the request parameters for a read-type request.

Syntax

void GetReadParameters(
  [out, optional] SIZE_T   *pSizeInBytes,
  [out, optional] LONGLONG *pullOffset,
  [out, optional] ULONG    *pulKey
);

Parameters

[out, optional] pSizeInBytes

A pointer to a variable that receives the size, in bytes, to read. To retrieve the data for reading, the driver calls the IWDFIoRequest::GetOutputMemory method.

This parameter is optional. The driver can pass NULL if it does not require the information.

[out, optional] pullOffset

A pointer to a variable that receives the offset, in bytes, to begin reading from the device or the file on the device. If the device does not support absolute read addresses, pullOffset can be ignored. For more information, see the following Remarks section.

Client applications specify this value in the Offset and OffsetHigh members of the OVERLAPPED structure. A pointer to OVERLAPPED is passed in the Microsoft Win32 ReadFile or ReadFileEx function.

This parameter is optional. The driver can pass NULL if it does not require the information.

[out, optional] pulKey

A pointer to a variable that receives a key that the driver can use to sort the I/O request in a way that the driver determines.

This parameter is optional. The driver can pass NULL if it does not require the information.

Return value

None

Remarks

A call to GetReadParameters fails if the request type is not a read type.

For devices that support addressing (for example, a disk device), the value that the pullOffset parameter points to is typically the byte offset into the device. For devices that do not support addressing (for example, a serial port), the driver can ignore the value at pullOffset.

Although the driver can optionally specify NULL for each of the pSizeInBytes, pullOffset, and pulKey parameters, the driver must specify at least one non-NULL parameter for GetReadParameters to execute successfully.

Requirements

Requirement Value
End of support Unavailable in UMDF 2.0 and later.
Target Platform Desktop
Minimum UMDF version 1.5
Header wudfddi.h (include Wudfddi.h)
DLL WUDFx.dll

See also