Element packing

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Element packing

 

Element alignment

 

By default, the elements are tightly packed in memory, one after each other.

 

You can alter this behaviour by specifying alignment modifier. It can take 3 different values:

1.byte, for 1 byte alignment

2.word, for 2 byte alignment

3.dword, for 4 byte alignment

 

The default packing is on byte level, so you don't really need to specify it.

 

In case you want to pack values aligned to 4 byte steps, you might consider using DWORD modifier.

 

Let's have a look at this example:

 

TYPE RGBColor
  R AS BYTE
  G AS BYTE
  B AS BYTE  
END TYPE

 

By default, the size of RGBColor will be 3 bytes, as you can verify with SizeOf:

 

msgBox SizeOf(RGBColor)

 

3 elements, each 1 byte in size.

 

To apply 32bit alignment, use DWORD modifier:

 

TYPE DwordAlignedRGBColor DWORD
  R AS BYTE
  G AS BYTE
  B AS BYTE  
END TYPE

 

This means that R, G and B elements will still be of byte data type, however their element offset will change to 4 byte jumps.

 

You can verify it easily:

 

DIM colorNormal  AS RGBColor
 
msgbox strFormat$("The offset of .R is {1}, .G is {2} and .B is {3}",
                  UDT_ElementOffset(colorNormal.r),
                  UDT_ElementOffset(colorNormal.g),
                  UDT_ElementOffset(colorNormal.b))
 
DIM colorAligned AS DwordAlignedRGBColor
                  
msgbox strFormat$("The offset of .R is {1}, .G is {2} and .B is {3}",
                  UDT_ElementOffset(colorAligned.r),
                  UDT_ElementOffset(colorAligned.g),
                  UDT_ElementOffset(colorAligned.b))