VPAEntry Struct Reference

Individual entry in the IImageVPA object's PVPAT. More...

Data Fields
intptr_t	XEntry
	Memory x-offset in bytes (columns).
intptr_t	YEntry
	Memory y-offset in bytes (lines).

Detailed Description

Individual entry in the IImageVPA object's PVPAT.

The VPAEntry array PVPAT is returned from GetImageVPA. The overall size (or length in element units) of the array is

cvbdim_t GetVPATLength(IMG Image)
{
  return max(ImageWidth(Image), ImageHeight(Image));
}

Note

The XEntry entries are only valid up to the ImageWidth and the YEntry entries up to ImageHeight.

In the picture at VPAT you see the logical setup of the VPAT. But if you look at this struct, you see that it combines XEntry and YEntry. Using this is a little unusual, but yields better cache behavior as all the offsets are in one contiguous memory block and all offsets are known.

If you take the two logical tables (X-table and Y-table from the VPAT image), you get the valid portion of the PVPAT array:

See also

VPAT for an explanation on how to use this data structure.

Field Documentation

XEntry

intptr_t VPAEntry::XEntry

Memory x-offset in bytes (columns).

Validity of this value depends on the ImageWidth. The offset is calculated from the base pointer returned by GetImageVPA.

YEntry

intptr_t VPAEntry::YEntry

Memory y-offset in bytes (lines).

Validity of this value depends on the ImageHeight. The offset is calculated from the base pointer returned by GetImageVPA.