Struct issue

[Alexander M]

how to make clear that this struct has to be 2 bytes in size and NOT 3?

typedef struct _TEST
{
USHORT FragmentOffset: 13;
UCHAR MF: 1;
UCHAR DF: 1;
UCHAR Reserved: 1;
} TEST, *PTEST;

Thanks Don't try it, just do it! ;-)

[Vitali Halershtein]

Hi, try to sizeof(...) = 4 ;) Vitali http://www.creative-case.com

[John M Drescher]

Use #pragma pack John

[Alexander M]

I did, but it doesn't work. Don't try it, just do it! ;-)

[Alexander M]

I can't, this struct is part of the IPv4 header. Don't try it, just do it! ;-)

[John M Drescher]

How about making all the UCHARs to USHORT? John

[Alexander M]

Thank you John, that works! Don't try it, just do it! ;-)

[Maxwell Chen]

Yes, you are right. But how strange ... although I remembered that in C++ syntax, we only have to write this way for bit field:

struct SS
{
unsigned A : 13;
unsigned B : 1;
unsigned C : 1;
unsigned D : 1;
}; // size = 4.

But with pragma of VisualC++7, the previous acts different to:

struct SS
{
unsigned short A : 13;
unsigned short B : 1;
unsigned short C : 1;
unsigned short D : 1;
}; // size = 2.

Maxwell Chen

[Anonymous]

Hi If you have problems with the size structue you have to close your structure declaration between #pragma pack() instruction, you can get additional info at msdn.