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WDF_ALIGN_SIZE_UP function (wdfcore.h)

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[Applies to KMDF and UMDF]

The WDF_ALIGN_SIZE_UP function returns the next-higher buffer size that is aligned to a specified alignment offset.

Syntax

size_t WDF_ALIGN_SIZE_UP(
  [in] size_t Length,
  [in] size_t AlignTo
);

Parameters

[in] Length

The length, in bytes, of a memory buffer.

[in] AlignTo

The alignment offset, in bytes. This value must be a power of 2, such as 2, 4, 8, 16, and so on.

Return value

WDF_ALIGN_SIZE_UP returns the aligned buffer size, in bytes.

Remarks

Drivers can use WDF_ALIGN_SIZE_UP or WDF_ALIGN_SIZE_DOWN to calculate a buffer size that is aligned to a specified alignment offset. This calculation is useful if your driver must allocate multiple contiguous buffers, if each buffer must begin at an address alignment boundary.

If the value of either input parameter is too large, arithmetic overflow causes WDF_ALIGN_SIZE_UP to return an invalid value that is smaller than Length. Your code should test for this condition.

Examples

The following code example receives a buffer size and returns the size (either the current size or the next-higher size) that aligns to a DWORD address boundary.

bufferSizeAligned = WDF_ALIGN_SIZE_UP(bufferSize,
                                      sizeof(DWORD));
if (bufferSizeAligned < bufferSize)
{
    // Buffer too large.
    ...
}

Requirements

Requirement Value
Target Platform Universal
Minimum KMDF version 1.0
Minimum UMDF version 2.0
Header wdfcore.h (include Wdf.h)
Library Wdf01000.sys (see Framework Library Versioning.)
IRQL Any IRQL.

See also

WDF_ALIGN_SIZE_DOWN