Re: share a structure array containing multidimensional char array

Oh I see, you aren't 'serializing' the structure to shared memory, I guess I wasn't clear when I said "the writer has to serialize...".

When you want to deserialize/serialize a managed type to/from unmanaged memory, you have to use the same serializer/deserializer at both sides, that means you also need to use .NET to serialize/deserialize at the C++ side.
For this you can use C++/CLI (VS2006 or VS2008) and compile your C++ program using /clr.

If you don't want to use .NET at the C++ side, you'll have to "custom" serialize, that means you'll have to copy the array of structures to the buffer obtained by MapViewOfFile. Besides the structures, you also have to store the number of structures serialized to the shared memory buffer and the size of the individual structure members, without this info it's impossible for the reader to determine the number of array members (number of structs) and the size of the structure members.

Willy.



"Aykut Ergin" <AykutErgin@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:9F8253C4-B780-4712-9C4A-F90CE7BC684D@xxxxxxxxxxxxxxxx
My original test code is shown below
I may have several errors,

hoping for your help.
Thanks in advance
Aykut

C++ code asis

HANDLE hKernel;
HANDLE hFile;

struct msg_file_s
{
unsigned char mb_buffer[10][10];
};

struct msg_file_s msg_file[16];
struct msg_file_s *msg_file_ptr;

HANDLE gfnInitMemory(struct msg_file_s **kernel_ram_ptr)
{
hKernel = CreateFileMapping ((HANDLE) 0xFFFFFFFF,
NULL,
PAGE_READWRITE,
0,
sizeof( struct msg_file_s ),
_T("TEST"));

if (hKernel != NULL)
{
switch(GetLastError())
{
case ERROR_ALREADY_EXISTS : return(FALSE);
case 0 : break;
}
}
else return(NULL);

*kernel_ram_ptr = (struct msg_file_s *)MapViewOfFile( hKernel,
FILE_MAP_READ | FILE_MAP_WRITE,
0,
0,
0 );

return(hKernel);
}


void init_struct()
{
struct msg_file_s *file_ptr;
file_ptr = &msg_file[0];
for(BYTE i=0;i<16;i++,file_ptr++)
{
for(BYTE i=0;i<10;i++)
for(BYTE j=0;j<10;j++)
file_ptr->mb_buffer[i][j] = 0x55;
}
}


// create and fill the memory mapped file
test_function()
{
msg_file_ptr = &msg_file[0];
hKernel = NULL;
hKernel = gfnInitMemory(&msg_file_ptr);

if (hKernel == NULL)
{
exit(0);
}

init_struct();
}

/*******************************************************************************************************/
/*******************************************************************************************************/
C# Code asis

[Serializable]
[StructLayout(LayoutKind.Sequential)]
unsafe struct msg_file_s
{
public byte[,] mb_buffer;
}

unsafe msg_file_s[] msg_file = new msg_file_s[16];
IntPtr hFileMap;
IntPtr address;


unsafe IntPtr map_memory_file()
{
hFileMap = CreateFileMapping(InvalidHandleValue, IntPtr.Zero,
PAGE_READWRITE, 0, 100, "TEST");
if (hFileMap == IntPtr.Zero)
{
MessageBox.Show("hFileMap olmadı");
return IntPtr.Zero;
}

address = MapViewOfFile(hFileMap, FILE_MAP_WRITE, 0, 0, IntPtr.Zero);
if (address == IntPtr.Zero)
{
MessageBox.Show("address olmadı");
return IntPtr.Zero;
}

return address;
}


unsafe static void GetObjectData2(IntPtr pBuf)
{
// set size of data bytes in MM segment manually
int len = 100;

// copy the MM data to a managed array
byte[] data = new byte[len];
Marshal.Copy(pBuf, data, 0, len);

// deserialize the managed byte[] to the struct representation
BinaryFormatter bf = new BinaryFormatter();
MemoryStream ms = new MemoryStream(data);
msg_file_s[] sa = (msg_file_s[])bf.Deserialize(ms);

// just a test to show
int x = sa[0].mb_buffer.GetUpperBound(0);
MessageBox.Show(x.ToString());

}

// test access memory mapped file
private void button1_Click(object sender, EventArgs e)
{
address = map_memory_file();
GetObjectData2(address);
}


"Aykut Ergin" wrote:

Hi Willy,

I am using C++ VS2005 and C# VS2005 compilers.
I write DLL with C++ VS2005. Struct member alignment=1byte.
I write application with C# VS2005.
I am not experienced at C# and dont know how to set structure alignment and
pack size.

Deserialization Error:
An unhandled exception of type
'System.Runtime.Serialization.SerializationException' occurred in mscorlib.dll
Additional information: Binary stream '0' does not contain a valid
BinaryHeader.
Possible causes are invalid stream or object version change between
serialization and deserialization.

Thank you very much for your valuable effort.
Best Regards,
Aykut


"Willy Denoyette [MVP]" wrote:

> See Inline
>
> Willy.
>
> "Aykut Ergin" <AykutErgin@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
> news:F6FFBC0F-D00C-43A1-96AC-FC4E482375D2@xxxxxxxxxxxxxxxx
> > Hi Willy,
> >
> > Thank you very much for your work.
> >
> > C++ code doesnot make any serialization.
>
> Mapping a datastructure, whatever it's type, in a serialization.
>
> > So at runtime C# code gives an serialization error at
> > "msg_file_s[] sa = (msg_file_s[]) bf.Deserialize(ms);"
> >
> What error do you get? Note that when mapping a structure to shared > memory,
> you have to consider the alignment and packing requirements of both > readers
> and writers if both are wriiten using different languages or compiler > tools.
>
> > I thought that it is very hard to memory map structure array.
> > I need both read and write memory mapped file at both side of C# and > > C++.
> > I am looking other ways to share memory between C++ and C#.
> >
> > Best Regards,
> > Aykut ERGİN
> > Nortel Netaş
> > Software Design Engineer
> >
> >
> >
> > "Willy Denoyette [MVP]" wrote:
> >
> >> Oh, but 256*256 is only 64.000 bytes!
> >>
> >> You can declare your structure like this:
> >>
> >> [Serializable]
> >> [StructLayout(LayoutKind.Sequential)]
> >> public struct msg_file_s
> >> {
> >> public byte[,] mb_buffer;
> >> public byte[] other;
> >> }
> >>
> >> The "writer" has to serialize the structure data and provide the > >> size of
> >> the
> >> total number of bytes in the shared memory segment to the "reader", > >> for
> >> instance as an int value at the start of the MM segment. Without > >> this
> >> length
> >> info there is no way to know the size and number of the individual
> >> structures stored in the MM segment.
> >>
> >> Then, the reader needs to deserialize the memory buffer as follows:
> >>
> >> // pBuf is the pointer that points to the shared memory buffer
> >> returned
> >> by the MapViewOfFile Win32 API.
> >>
> >> static void GetObjectData2(IntPtr pBuf)
> >> {
> >> // get size of data bytes in MM segment
> >> int len = Marshal.ReadInt32(pBuf, 0);
> >> // copy the MM data to a managed array
> >> byte[] data = new byte[len];
> >> Marshal.Copy(new IntPtr((int)pBuf + sizeof(int)), data, 0,
> >> len);
> >> // deserialize the managed byte[] to the struct > >> representation
> >> BinaryFormatter bf = new BinaryFormatter();
> >> MemoryStream ms = new MemoryStream(data);
> >> msg_file_s[] sa = (msg_file_s[]) bf.Deserialize(ms);
> >> // use the array of structs...
> >> foreach(msg_file_s s in sa)
> >> {
> >> // use structure data
> >> int x = s.mb_buffer.GetUpperBound(0);
> >> int y = s.mb_buffer.GetUpperBound(1);
> >> ...
> >> }
> >>
> >> }
> >> }
> >>
> >>
> >> Willy.
> >>
> >>
> >> "Aykut Ergin" <AykutErgin@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in > >> message
> >> news:6EEA35B1-D8CF-499B-AA9D-40873B3C732E@xxxxxxxxxxxxxxxx
> >> > Hi,
> >> >
> >> > My original structure is like shown below
> >> > struct msg_file_s
> >> > {
> >> > unsigned char mb_buffer[256][256];
> >> > unsigned char other[64];
> >> > };
> >> >
> >> > struct msg_file_s msg_file[16];
> >> >
> >> > This structure will execute on communication dll ( written with > >> > C++ ).
> >> > Applications will use this dll.
> >> > We have not the chance to edit it because we use for several > >> > projects
> >> > for
> >> > 15
> >> > years.
> >> > We use this MMF with VC++ 5 / VC++ 6 / BCB 6 on NT4 / 2000 / 2003 > >> > / XP.
> >> > We do not have any problem.
> >> >
> >> > Best Regards
> >> > -- > >> > Aykut ERGİN
> >> > Nortel Netaş
> >> > Software Design Engineer
> >> >
> >> >
> >> >
> >> > "Willy Denoyette [MVP]" wrote:
> >> >
> >> >> "Aykut Ergin" <AykutErgin@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in > >> >> message
> >> >> news:139D98E6-5572-4BB8-8FAD-E312F04F871A@xxxxxxxxxxxxxxxx
> >> >> >I want to share a structure array containing multi dimensional > >> >> >char
> >> >> >array
> >> >> > between C# and C++, by using memory mapped file.
> >> >> >
> >> >> > I already have C++ code for handling memory mapped file.
> >> >> > I am passing pointer to the structure array as shown below for > >> >> > C++;
> >> >> > I am able to work with pointer ( for C++ ).
> >> >> > C++ code works fine.
> >> >> >
> >> >> > I am working on converting code for memory mapped file in C#.
> >> >> > My problems:
> >> >> > 1. How should I define structure array in C# ( for the below
> >> >> > structure
> >> >> > array
> >> >> > ).
> >> >> > 2. How should I define pointer to structure array in C# ( for > >> >> > the
> >> >> > below
> >> >> > structure array ).
> >> >> >
> >> >> > Any help related to this would be highly appreciated.
> >> >> >
> >> >> > C++ implementation:
> >> >> >
> >> >> > struct msg_file_s
> >> >> > {
> >> >> > unsigned char mb_buffer[1000][1000];
> >> >> > .....
> >> >> > .....
> >> >> > };
> >> >> >
> >> >> > struct msg_file_s msg_file[16];
> >> >> > struct msg_file_s *msg_file_ptr;
> >> >> >
> >> >> >
> >> >> > HANDLE api_map_memory(struct msg_file_s **msg_file_ptr)
> >> >> > {
> >> >> > HANDLE hKernel = CreateFileMapping ( (HANDLE) 0xFFFFFFFF,
> >> >> >
> >> >> > NULL,
> >> >> >
> >> >> > PAGE_READWRITE,
> >> >> >
> >> >> > 0,
> >> >> >
> >> >> > sizeof( struct msg_file_s ),
> >> >> >
> >> >> > _T("TEST"));
> >> >> >
> >> >> > *msg_file_ptr = (struct msg_file_s *) MapViewOfFile( hKernel,
> >> >> >
> >> >> > FILE_MAP_READ | FILE_MAP_WRITE,
> >> >> >
> >> >> > 0,
> >> >> >
> >> >> > 0,
> >> >> >
> >> >> > 0
> >> >> > );
> >> >> > return(hKernel);
> >> >> > }
> >> >> >
> >> >> >
> >> >> > map_memory_file(int index)
> >> >> > {
> >> >> > msg_file_ptr = &msg_file[index];
> >> >> > hKernel = api_map_memory(&msg_file_ptr);
> >> >> > }
> >> >> >
> >> >> > /****************************************************************************/
> >> >> >
> >> >> > C# implementation:
> >> >> >
> >> >> > [StructLayout(LayoutKind.Sequential)]
> >> >> > unsafe struct msg_file_s
> >> >> > {
> >> >> > [MarshalAs(UnmanagedType.LPArray, ArraySubType= > >> >> > UnmanagedType.U1,
> >> >> > SizeConst = 100, SizeParamIndex=2)]
> >> >> > byte[,] mb_buffer;
> >> >> > }
> >> >> >
> >> >> >
> >> >> > -- > >> >> > Aykut ERGİN
> >> >> > Nortel Netaş
> >> >> > Software Design Engineer
> >> >> >
> >> >>
> >> >>
> >> >>
> >> >> Are you sure you want to pass such a huge amount of data through
> >> >> Shared
> >> >> memory (MM file)?
> >> >> I see in your declaration that one element is already 1000000 > >> >> bytes,
> >> >> how
> >> >> large are the other elements? and how large is the array of > >> >> structures
> >> >> you
> >> >> want to share?
> >> >>
> >> >> Note that passing data through Shared Memory requires a lot more
> >> >> memory
> >> >> because you'll have to marshal the data from unmanaged memory to
> >> >> managed
> >> >> memory before you will be able to access the managed presentation > >> >> of
> >> >> the
> >> >> unmanaged data. Note that the extra marshaling will reduce the
> >> >> performance
> >> >> advantage of the shared memory "transfer" significantly, if not
> >> >> completely.
> >> >>
> >> >> Willy.
> >> >>
> >> >>
> >> >>
> >> >>
> >>
> >>
> >>
>
>
>


.