Using/converting legacy structs from a stream

[=?Utf-8?B?U2V0aEluTUk=?=]

I am a total newb at .net, and I have not been able to search out a best
practice answer to what must be a common problem.

My app must process binary data from a UDP socket, a MSMQ queue and a file.
In C, the data is in nested structs, with mixed types, floats, ints, char
arrays, int arrays, variable length arrays of structs etc.

My preference would be to access the data in a similar fashion to C, casting
the byte array of received data to the struct I want, and then sending out
the struct when it is time to transmit.

How can I format a struct to be able to mimic legacy structs, especially
with arrays? I see how I can do it for marshalled code, with [ MarshalAs(
UnmanagedType.B yValArray, SizeConst=XX )] attribute, but does that only work
with unmanaged code?

Thanks,

Seth

[John Vottero]

Re: Using/converting legacy structs from a stream

"SethInMI" <SethInMI@discu ssions.microsof t.comwrote in message
news:CA8B0658-E124-4BBB-B45A-CD6B3E5C0C68@mi crosoft.com...

>I understand how to at least get started using the Marshal attributes in
defining my struct in C#, but I am still I think missing one step. Does
marshalling work if no unmanaged code or memory is accessed?
>
here is my pseudo code, where myStruct is defined using LayoutSequentia l
and
appropriate Marshalling attributes to mimic the layout of legacy C struct.
>
Byte[] RawData = sock.Receive(re f RawAddr);
If (RawData.Length == Marshal.SizeOf( myStruct) {
Convert RawData into myStruct (using marshalling? just a cast?)
}

To convert RawData into myStruct, you would do something like:

IntPtr adr = Marshal.UnsafeA ddrOfPinnedArra yElement(RawDat a, 0);
MyStruct myStruct = Marshal.PtrToSt ructure(adr, typeof(MyStruct ));

When you use the LayoutSequentia l and Marshaling attributes, you aren't
actually changing the structure, you're just providing instructions that are
used when marshaling the structure to/from unmanaged bytes.

[=?Utf-8?B?U2V0aEluTUk=?=]

Re: Using/converting legacy structs from a stream

Thanks John.

You mentioned UnsafeAddrOfPin nedArrayElement in your first post, I just
didn't pick up how to use it.

"John Vottero" wrote:

"SethInMI" <SethInMI@discu ssions.microsof t.comwrote in message
news:CA8B0658-E124-4BBB-B45A-CD6B3E5C0C68@mi crosoft.com...

I understand how to at least get started using the Marshal attributes in
defining my struct in C#, but I am still I think missing one step. Does
marshalling work if no unmanaged code or memory is accessed?

here is my pseudo code, where myStruct is defined using LayoutSequentia l
and
appropriate Marshalling attributes to mimic the layout of legacy C struct.

Byte[] RawData = sock.Receive(re f RawAddr);
If (RawData.Length == Marshal.SizeOf( myStruct) {
Convert RawData into myStruct (using marshalling? just a cast?)
}

>
To convert RawData into myStruct, you would do something like:
>
IntPtr adr = Marshal.UnsafeA ddrOfPinnedArra yElement(RawDat a, 0);
MyStruct myStruct = Marshal.PtrToSt ructure(adr, typeof(MyStruct ));
>
When you use the LayoutSequentia l and Marshaling attributes, you aren't
actually changing the structure, you're just providing instructions that are
used when marshaling the structure to/from unmanaged bytes.
>
>