Length of a struct

[Guest]

Hello NG,

I have two structs.
The only differnce is the order of the members:


public struct DataStruct
{
public UInt16 Sekunde;
public UInt32 BehälterId;
public UInt32 WannenNr;
public UInt16 Station;
};

public struct DataStruct
{
public UInt32 BehälterId;
public UInt32 WannenNr;
public UInt16 Station;
public UInt16 Sekunde;
};


If I use SizeOf for the struct it is 16 forthe first and 12 for the second
struct.
The right value should by 12.

If I change the order, why do I get another length ?

regards
Stephan

 

[Greg Young [MVP]]

Padding.

public UInt16 Sekunde; //padded to 32 bits
public UInt32 BehälterId; //32 bits
public UInt32 WannenNr;//32 bits
public UInt16 Station; //padded to 32 bits

you can change padding http://www.vsj.co.uk/articles/display.asp?id=501

 

[Sericinus hunter]

Hello NG,

I have two structs.
The only differnce is the order of the members:

public struct DataStruct
{
public UInt16 Sekunde;
public UInt32 BehälterId;
public UInt32 WannenNr;
public UInt16 Station;
};

public struct DataStruct
{
public UInt32 BehälterId;
public UInt32 WannenNr;
public UInt16 Station;
public UInt16 Sekunde;
};

If I use SizeOf for the struct it is 16 forthe first and 12 for the second
struct. The right value should by 12.

If I change the order, why do I get another length ?

Suspiciously looks like memory alignment to me. Each field in the struct
is multiple of four bytes.