sizeof problem

[Emil_halim]

Hi all


This code print 16 and give wrong size of type , it must be 14

Type BITMAPFILEHEADER
 bfType As Int16
 bfSize As Long
 bfReserved1 As Int16
 bfReserved2 As Int16
 bfOffBits As Long
End Type

print SizeOf(BITMAPFILEHEADER)

Do
 Sleep
Until Me Is Nothing

[scalion]

Hi,
Effectively, It's just a question of speed, but hello the size of the table in memory!

In fact this appears in the documentation:

"Dieser Type würde also 14 Bytes belegen (1 + 4 + 1 + 8), wenn nicht Speicherzugriffe auf unausgerichtete Daten im Speicher auch auf INTEL-Prozessoren benachteiligt sind (auf anderen Prozessoren (MIPS, Alpha, M68000) sogar noch erheblich mehr). Deshalb werden vom GFA-BASIC 32 automatisch Füllbytes eingefügt, um eine Ausrichtung auf entsprechende Byte-Grenzen zu erreichen."

Therefore, GFA-BASIC 32 automatically inserts padding bytes to match byte boundaries.

To have an exact size of corresponding data you must use Packed Statement :


Type BITMAPFILEHEADER Packed 1
 bfType As Int16
 bfSize As Long
 bfReserved1 As Int16
 bfReserved2 As Int16
 bfOffBits As Long
End Type

print SizeOf(BITMAPFILEHEADER) // <- Give 14

Do
 Sleep
Until Me Is Nothing

[Emil_halim]

great , yah..

thank a lot

i will update my last demo with your solution.