Access lookup-service managed by C module

[Sune]

Hi all,

I'm not a C# programmer so please be gentle:

Prereq:
---------------
- The lookup service (see below) implemented by a C module cannot be
re-written in C# ;-)
- The lookup service is to be loaded into the process of the C#
application, i.e. I want to avoid expensive IPC

1)
I got a C module that organizes a big block of memory into a fairly
nice lookup service. This C module exposes a C API.

From my understanding, C# being a pointerless language, C# client

code cannot by any means, by mistake, access the memory block managed
by the C module. Is this correct? Will the bridge between C and C#
open the can of worms I try to avoid by using a pointerless language?

Note:
In C/C++, a rouge pointer can very easily damage the lookup service
and this would not be noticed until several days have passed. This is
not acceptable.

Thank you for your time
/Sune

 

[Nicholas Paldino [.NET/C# MVP]]

Sune,

Well, you could access the memory block that is used by the C module if
you REALLY wanted to, but generally, the way it works is that you are going
to call the API through the P/Invoke layer, which is going to be responsible
for marshaling the .NET types to the unmanaged module and back.

 

[Sune]

Sune,

Well, you could access the memory block that is used by the C module if
you REALLY wanted to, but generally, the way it works is that you are going
to call the API through the P/Invoke layer, which is going to be responsible
for marshaling the .NET types to the unmanaged module and back.

--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

Hi all,

I'm not a C# programmer so please be gentle:

Prereq:
---------------
- The lookup service (see below) implemented by a C module cannot be
re-written in C# ;-)
- The lookup service is to be loaded into the process of the C#
application, i.e. I want to avoid expensive IPC

1)
I got a C module that organizes a big block of memory into a fairly
nice lookup service. This C module exposes a C API.
code cannot by any means, by mistake, access the memory block managed
by the C module. Is this correct? Will the bridge between C and C#
open the can of worms I try to avoid by using a pointerless language?

Note:
In C/C++, a rouge pointer can very easily damage the lookup service
and this would not be noticed until several days have passed. This is
not acceptable.

Thank you for your time
/Sune

Thanks Nicholas!

 

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

Prereq:
---------------
- The lookup service (see below) implemented by a C module cannot be
re-written in C# ;-)
- The lookup service is to be loaded into the process of the C#
application, i.e. I want to avoid expensive IPC

You asked the same question in the Java group. Do you need the
solution in C# or Java or both ?

1)
I got a C module that organizes a big block of memory into a fairly
nice lookup service. This C module exposes a C API.

code cannot by any means, by mistake, access the memory block managed
by the C module. Is this correct? Will the bridge between C and C#
open the can of worms I try to avoid by using a pointerless language?

Pure managed C# can not overwrite memory.

You will need to call unmanaged (native) code to do what
you want.

And that code can overwrite memory.

If you want to have your C# code access global memory
managed by the C code, then I think you can use only your C# code and
native code provided by Microsoft.

See below for a code snippet (some C# code that communicates
via some Delphi code via global memory.

Arne

==============================

using System;
using System.Runtime.InteropServices;

class MainClass
{
const int PAGE_READONLY = 0x0002;
const int PAGE_READWRITE = 0x0004;
const int PAGE_EXECUTE = 0x0010;
const int PAGE_EXECUTE_READ = 0x0020;
const int PAGE_EXECUTE_READWRITE = 0x0040;
const int PAGE_GUARD = 0x0100;
const int PAGE_NOACCESS = 0x0001;
const int PAGE_NOCACHE = 0x0200;
const int FILE_MAP_COPY = 0x0001;
const int FILE_MAP_WRITE = 0x0002;
const int FILE_MAP_READ = 0x0004;
const int FILE_MAP_ALL_ACCESS = 0x001F;

[StructLayout( LayoutKind.Sequential )]
class SECURITY_ATTRIBUTES
{
//int nLength;
//int lpSecurityDescriptor;
//int bInheritHandle;
}

[DllImport("kernel32.dll")]
static extern int CreateFileMappingA ( uint hFile,
SECURITY_ATTRIBUTES
lpFileMappigAttributes,
int flProtect,
int dwMaximumSizeHigh,
int dwMaximumSizeLow,
string lpName);

[DllImport("kernel32.dll")]
static extern IntPtr MapViewOfFile ( int hFileMappingObject,
int dwDesiredAccess,
int dwFileOffsetHigh,
int dwFileOffsetLow,
int dwNumberOfBytesToMap);

[DllImport("kernel32.dll")]
static extern int UnmapViewOfFile (IntPtr lpBaseAddress);

[DllImport("kernel32.dll")]
static extern int CloseHandle ( int hObject);

public static void Main(string[] args)
{
int mem = CreateFileMappingA(0xFFFFFFFF, null, PAGE_READWRITE,
0, 8192, "GBLMEM");
IntPtr data = MapViewOfFile(mem, FILE_MAP_WRITE, 0, 0, 8192);
Console.WriteLine("Run Delphi program and press enter");
Console.ReadLine();
int[] data2 = new int[2048];
Marshal.Copy( data, data2, 0, 3 );
UnmapViewOfFile(data);
CloseHandle(mem);
Console.WriteLine(data2[0]);
Console.WriteLine(data2[1]);
Console.WriteLine(data2[2]);
}
}