trying to port some C++ structures to C# problem.

[Olaf Baeyens]

I am trying to port some C++ structures to C# but I have troubles with this
one.
Note: this is a file record, so I must keep this format.

#pragma pack( push, 1 )
typedef struct {
char title[80];

DWORD dwCount;
} STLHEADER, *LPSTLHEADER;
#pragma pack( pop )

Using Google I discovered that this could be ported to this C# variant,
note the 'Marshal' to create a 80 byte array.

[StructLayout(La youtKind.Sequen tial, Pack=1)]
internal struct STLHEADER {
[MarshalAs (UnmanagedType. U1, SizeConst=80)]
public char[] title;

public int dwCount;
}

So far so good, but now I am stuck on this line "sizeof(STLHEAD ER)" needed
in a unsafe function.
error CS0208: Cannot take the address or size of a variable of a managed
type ('MySpace.STLHE ADER')

And it has something to do with the Marshal thing.
I could replace the "sizeof(STLHEAD ER)" with 80+4 but I would really prefer
to have a more professional sollution.
Maybe there is another alternative way to define a 'char title[80]' byte
array?

Thanks for any feedback. :-)

--
http://www.skyscan.be

[Dennis Myrén]

Since you struct is using reference types(char []) you will need to use the
System.Runtime. InteropServices .Marshal.SizeOf method to determine the size
of your structure.

One more thing; you should change the char [] member into a byte [].
Otherwise, your data will not be parsed correctly, since char [80] in C# is
actually
160 bytes of size.
byte [] is in C# what char [] was in C++.
--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Olaf Baeyens" <ol**********@s kyscan.be> wrote in message
news:41******** **************@ news.skynet.be. ..

I am trying to port some C++ structures to C# but I have troubles with this
one.
Note: this is a file record, so I must keep this format.

#pragma pack( push, 1 )
typedef struct {
char title[80];

DWORD dwCount;
} STLHEADER, *LPSTLHEADER;
#pragma pack( pop )

Using Google I discovered that this could be ported to this C# variant,
note the 'Marshal' to create a 80 byte array.

[StructLayout(La youtKind.Sequen tial, Pack=1)]
internal struct STLHEADER {
[MarshalAs (UnmanagedType. U1, SizeConst=80)]
public char[] title;

public int dwCount;
}

So far so good, but now I am stuck on this line "sizeof(STLHEAD ER)"
needed
in a unsafe function.
error CS0208: Cannot take the address or size of a variable of a managed
type ('MySpace.STLHE ADER')

And it has something to do with the Marshal thing.
I could replace the "sizeof(STLHEAD ER)" with 80+4 but I would really
prefer
to have a more professional sollution.
Maybe there is another alternative way to define a 'char title[80]' byte
array?

Thanks for any feedback. :-)

--
http://www.skyscan.be

[Dennis Myrén]

And;
change
[MarshalAs (UnmanagedType. U1, SizeConst=80)]
into
[MarshalAs (UnmanagedType. ByValArray, SizeConst=80)]

So, now we have got:
[StructLayout(La youtKind.Sequen tial, Pack = 1)]
internal struct STLHEADER
{
[MarshalAs (UnmanagedType. ByValArray, SizeConst = 80)]
public byte [] title;
public int dwCount;
}
--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Dennis Myrén" <de****@oslokb. no> wrote in message
news:2n******** ************@ne ws4.e.nsc.no...

Since you struct is using reference types(char []) you will need to use
the
System.Runtime. InteropServices .Marshal.SizeOf method to determine the size
of your structure.

One more thing; you should change the char [] member into a byte [].
Otherwise, your data will not be parsed correctly, since char [80] in C#
is actually
160 bytes of size.
byte [] is in C# what char [] was in C++.
--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Olaf Baeyens" <ol**********@s kyscan.be> wrote in message
news:41******** **************@ news.skynet.be. ..

I am trying to port some C++ structures to C# but I have troubles with
this
one.
Note: this is a file record, so I must keep this format.

#pragma pack( push, 1 )
typedef struct {
char title[80];

DWORD dwCount;
} STLHEADER, *LPSTLHEADER;
#pragma pack( pop )

Using Google I discovered that this could be ported to this C# variant,
note the 'Marshal' to create a 80 byte array.

[StructLayout(La youtKind.Sequen tial, Pack=1)]
internal struct STLHEADER {
[MarshalAs (UnmanagedType. U1, SizeConst=80)]
public char[] title;

public int dwCount;
}

So far so good, but now I am stuck on this line "sizeof(STLHEAD ER)"
needed
in a unsafe function.
error CS0208: Cannot take the address or size of a variable of a managed
type ('MySpace.STLHE ADER')

And it has something to do with the Marshal thing.
I could replace the "sizeof(STLHEAD ER)" with 80+4 but I would really
prefer
to have a more professional sollution.
Maybe there is another alternative way to define a 'char title[80]' byte
array?

Thanks for any feedback. :-)

--
http://www.skyscan.be

[Willy Denoyette [MVP]]

Not sure why you need this size for, but you have to:
- Declare the array element as UnmanagedType.B yValArray, and
- use the Marshal.SizeOf method to get the marshaled size of a struct.

[StructLayout(La youtKind.Sequen tial, Pack=1)]
internal struct STLHEADER {
[MarshalAs (UnmanagedType. ByValArray, SizeConst=80)]
public char[] title;
public int dwCount;
}

....
STLHEADER stlh = new STLHEADER();
int marshaledSizeOf Struct = Marshal.SizeOf( stlh); // should be 84

Willy.
"Olaf Baeyens" <ol**********@s kyscan.be> wrote in message
news:41******** **************@ news.skynet.be. ..

I am trying to port some C++ structures to C# but I have troubles with this
one.
Note: this is a file record, so I must keep this format.

#pragma pack( push, 1 )
typedef struct {
char title[80];

DWORD dwCount;
} STLHEADER, *LPSTLHEADER;
#pragma pack( pop )

Using Google I discovered that this could be ported to this C# variant,
note the 'Marshal' to create a 80 byte array.

[StructLayout(La youtKind.Sequen tial, Pack=1)]
internal struct STLHEADER {
[MarshalAs (UnmanagedType. U1, SizeConst=80)]
public char[] title;

public int dwCount;
}

So far so good, but now I am stuck on this line "sizeof(STLHEAD ER)"
needed
in a unsafe function.
error CS0208: Cannot take the address or size of a variable of a managed
type ('MySpace.STLHE ADER')

And it has something to do with the Marshal thing.
I could replace the "sizeof(STLHEAD ER)" with 80+4 but I would really
prefer
to have a more professional sollution.
Maybe there is another alternative way to define a 'char title[80]' byte
array?

Thanks for any feedback. :-)

--
http://www.skyscan.be

[Olaf Baeyens]

Wow thanks for the quick responce.

But Now I get this problem:

int iSTLHeaderSize= Marshal.SizeOf( STLHEADER);
Generates an error error "CS0118: 'MySpace.STLHEA DER' denotes a 'class'
where a 'variable' was expected"
Odd since STLHEADER) is a structure type.

Another problem is this;

Normally without the char[] the code works fine

fixed (void *lSTLHeader=&ST LFile.BufferPtr[0]) {
STLHEADER *pSTLHeader=(ST LHEADER *)lSTLHeader;
....
}

But because of the Marshal thing, it refuses to work so I found a tip to
use 'Marshal.PtrToS tructure' on Google.
So I tried this:
fixed (void *lSTLHeader=&ST LFile.BufferPtr[0]) {
STLHEADER *pSTLHeader= (STLHEADER *)
Marshal.PtrToSt ructure(lSTLHea der,typeof(STLH EADER) );
}

But 'Marshal.PtrToS tructure' tells me now that lSTLHeader should be a
IntPtr, so now is the question how can I convert void *lSTLHeader to
IntPtr????

(As you can see I am very new to this Marshal thing)
I appreciate the help though. :-)
--
http://www.skyscan.be

[Dennis Myrén]

The SizeOf method has two overloads, one expecting a type, the other
expecting an instance of a type. I think the most efficient one would be
that one taking a type, so to get the size, do:
int size = Marshal.SizeOf( typeof(STLHEADE R));

Olaf Baeyens <ol**********@s kyscan.be> wrote:

But because of the Marshal thing, it refuses to work so I found a tip to
use 'Marshal.PtrToS tructure' on Google.
So I tried this:
fixed (void *lSTLHeader=&ST LFile.BufferPtr[0]) {
STLHEADER *pSTLHeader= (STLHEADER *)
Marshal.PtrToS tructure(lSTLHe ader,typeof(STL HEADER) );
} If your structure did not use reference types(byte []), you could have done:
byte [] buff = new byte [sizeof(STLHEADE R)];
[LOAD RAW DATA INTO buff]
fixed (byte * pBuff = buff)
header = * ((STLHEADER *) pBuff);

However, since you use a reference type in the structure, i think this is
the way to do it:
byte [] buff = new byte [Marshal.SizeOf( typeof(STLHEADE R))];
[LOAD RAW DATA INTO buff]
IntPtr ptr = Marshal.AllocHG lobal(buff.Leng th);
Marshal.Copy(bu ff, 0x0, ptr, buff.Length);
header = (STLHEADER) Marshal.PtrToSt ructure(ptr, typeof(STLHEADE R));
Marshal.FreeHGl obal(ptr);

HTH.

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Olaf Baeyens" <ol**********@s kyscan.be> wrote in message
news:41******** *************** @news.skynet.be ... Wow thanks for the quick responce.

But Now I get this problem:

int iSTLHeaderSize= Marshal.SizeOf( STLHEADER);
Generates an error error "CS0118: 'MySpace.STLHEA DER' denotes a 'class'
where a 'variable' was expected"
Odd since STLHEADER) is a structure type.

Another problem is this;

Normally without the char[] the code works fine

fixed (void *lSTLHeader=&ST LFile.BufferPtr[0]) {
STLHEADER *pSTLHeader=(ST LHEADER *)lSTLHeader;
....
}

But because of the Marshal thing, it refuses to work so I found a tip to
use 'Marshal.PtrToS tructure' on Google.
So I tried this:
fixed (void *lSTLHeader=&ST LFile.BufferPtr[0]) {
STLHEADER *pSTLHeader= (STLHEADER *)
Marshal.PtrToSt ructure(lSTLHea der,typeof(STLH EADER) );
}

But 'Marshal.PtrToS tructure' tells me now that lSTLHeader should be a
IntPtr, so now is the question how can I convert void *lSTLHeader to
IntPtr????

(As you can see I am very new to this Marshal thing)
I appreciate the help though. :-)
--
http://www.skyscan.be

[Olaf Baeyens]

> int size = Marshal.SizeOf( typeof(STLHEADE R));

This worked! typeof was missing. :-)

The rest I am trying to implement now, I report back if it works.

But I am wondering, since I use pure C# why do I need marshalling at all?
The structure is created in C# and the parsing and loading functionality of
the binary file is also created in that same C# assembly.
So as far as I understand this, I do not have a situation between managed
and unmnaged code because it is pure C#.

There is probably a very logical reason for this. :-)

--
http://www.skyscan.be

[Willy Denoyette [MVP]]

See inline ****
Willy.
"Olaf Baeyens" <ol**********@s kyscan.be> wrote in message
news:41******** *************** @news.skynet.be ...

Wow thanks for the quick responce.

But Now I get this problem:

int iSTLHeaderSize= Marshal.SizeOf( STLHEADER);
Generates an error error "CS0118: 'MySpace.STLHEA DER' denotes a 'class'
where a 'variable' was expected"
Odd since STLHEADER) is a structure type.
*** There's is nothin odd, SizeOf takes a variable argument like:
STLHEADER stlh = new STLHEADER();
int iSTLHeaderSize= Marshal.SizeOf( stlh);

or:
int iSTLHeaderSize= Marshal.SizeOf( typeof(STLHEADE R));

Another problem is this;

Normally without the char[] the code works fine

fixed (void *lSTLHeader=&ST LFile.BufferPtr[0]) {
STLHEADER *pSTLHeader=(ST LHEADER *)lSTLHeader;
....
}

But because of the Marshal thing, it refuses to work so I found a tip to
use 'Marshal.PtrToS tructure' on Google.
So I tried this:
fixed (void *lSTLHeader=&ST LFile.BufferPtr[0]) {
STLHEADER *pSTLHeader= (STLHEADER *)
Marshal.PtrToSt ructure(lSTLHea der,typeof(STLH EADER) );
}

But 'Marshal.PtrToS tructure' tells me now that lSTLHeader should be a
IntPtr, so now is the question how can I convert void *lSTLHeader to
IntPtr????

(As you can see I am very new to this Marshal thing)
I appreciate the help though. :-)

What you need is StructureToPtr, that is marshal a structure to a
pointer....

STLHEADER stlh = new STLHEADER(); // crate instance of struct
.... // initialize the struct fields
int iSTLHeaderSize= Marshal.SizeOf( stlh); // get size of marshaled struct
IntPtr stlhPtr = Marshal.AllocHG lobal( iSTLHeaderSize) // allocate
unmanaged memory with size of struct
Marshal.Structu reToPtr(stlh , stlhPtr , true); // mashal managed
struct to unmanaged struct
.....// use unmanaged struct pointer to call unmanaged code functions
.....
Marshal.FreeHGl obal(stlhPtr ); // Free unmanaged memory when done

But again I'm not sure this is what you want, therefore I asked why you
needed the size of the struct.

Willy.

[Dennis Myrén]

Well, you could have avoided using Marshal utilities by manually loading the
members of STLHEADER
from a raw byte array source.

Marshalling could also have been avoided if the structure contained only
value types.
As the first example in my last post showed, you then could have used
"unsafe" code statements
in order to cast a raw byte array into a data structure.
This is possible since the structure is then stored in RAM in the exact way
as it was declared.
However, if reference types is used in the structure, you will need
something to marshal
them as if they were value types, because they are actually allocated on the
heap.

For instance, what i guess Marshal.SizeOf does, is locating any reference
types that are
members of the structure on the heap and measures it's size explicitly.

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
"Olaf Baeyens" <ol**********@s kyscan.be> wrote in message
news:41******** *************** @news.skynet.be ...

int size = Marshal.SizeOf( typeof(STLHEADE R));

This worked! typeof was missing. :-)

The rest I am trying to implement now, I report back if it works.

But I am wondering, since I use pure C# why do I need marshalling at all?
The structure is created in C# and the parsing and loading functionality
of
the binary file is also created in that same C# assembly.
So as far as I understand this, I do not have a situation between managed
and unmnaged code because it is pure C#.

There is probably a very logical reason for this. :-)

--
http://www.skyscan.be

[Olaf Baeyens]

> But again I'm not sure this is what you want, therefore I asked why you

needed the size of the struct.

Wel I have a binary STL file that contains a header and then a lot of 3D
triangles.
What I do is to load the complete file in memory, then maps a structure to
the header and if that structure is correct then I map another STLFACET
structure for every triangle.

It is code that is needed for my OpenGL visualization stuff, and since the
original data files can be huge, I try to avoid copying as much as I can.
Managed code is perfect for 3D modelling stuff. No more tracking of who
created the object and who should delete it. Wonderfull. :-)

This STL parser is only the beginning part, I try to create the technology
to parse any potentional binary file formats (bmp, tiff, jpg,...) that I
might encounter.
I want to create a code base for this.

--
http://www.skyscan.be