An MSDN sample might be worth looking at:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconbufferssample.asp
It works for me on .NET, but I haven't been able to make it work with
mono... I'm thinking that mono isn't ready for full-blown DllImport
yet.
For example, the following works with .NET
// native.c
// Native library
#include <string.h>
#ifdef _MSC_VER
__declspec(dllexport)
#endif
int getname(char* s, unsigned int n)
{
const char m[] = "This is my message. Isn't it nice?";
strncpy(s, m, n);
return 0;
}
With VC, compile as `cl /LD native.c'; should create `native.dll'.
On Linux, compile as `gcc -c -fpic native.c && ld -shared -o
libnative.so native.o -lc', should create `libnative.so'
On Linux, make sure that `LD_LIBRARY_PATH' contains the directory with
`libnative.so': `export LD_LIBRARY_PATH=`pwd`'
Now, the managed code:
// managed.cs
using System;
using System.Runtime.InteropServices;
using System.Text;
public class ghbn {
[DllImport("native")]
private static extern int getname(
StringBuilder sb,
uint len);
public static void Main () {
StringBuilder sb = new StringBuilder(255);
getname(sb, (uint) sb.Capacity);
Console.Write("name: ");
Console.WriteLine(sb.ToString());
}
}
Compile under .NET with `csc.exe /out:managed-net.exe managed.cs'
Compile under mono with `mcs managed.cs'
When I run either `managed.exe' (the mcs-compiled program) or
`managed-net.exe' (the csc-compiled program) under .NET, I get the
expected output:
name: This is my message. Isn't it nice?
When I run either `managed.exe' or `managed-net.exe' under mono, I get
errors:
name:
** (process:13403): WARNING **: unhandled exception
System.NullReferenceException: "A null value was found where an object
instance was required"
in <0x00065> .ghbn:Main ()
RESULT: -1
This implies to me that Mono does not properly handle PInvoke calls, at
least currently. (CVS tree built around 9:00 AM this morning).
I should probably add this to bugzilla...
- Jon
On Fri, 2002-06-14 at 13:40, Stewart Allen wrote:
I've been struggling with DllImport all evening just to call
gethostname(char *buf, int len). Seems like it should be simple. There
appear to be a lot of examples of sending string arguments and getting
string return values, but I can't find anything that addresses filling a
preallocated string buffer.
most tests (that I can get to compile) result in:
** (process:7): WARNING **: unhandled exception
System.NullReferenceException: "A null value was found where an object
instance was required"
Any help is greatly appreciated.
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_______________________________________________
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