Memory Mapped file in C++ read in Java

Question

I have a C++ program that uses at one point

hMapFile = OpenFileMapping(dwDesiredAccess, bInheritHandle, lpName);

The lpName is something like "myfile" without extensions or path, i.e. a memory mapped file. I can find the file with the WinObj-Browser (WinObj) in the path Sessions\1\BaseNamedObjects\myfile. If I try to read that particular file in Java, I tried

File file = new File("myfile");
FileChannel filechannel = new RandomAccessFile(file, "r").getChannel();
MappedByteBuffer buffer = filechannel.map(FileChannel.MapMode.READ_ONLY, 0, filechannel.size());

But I get always the same error: Cannot find the specified file at the RandomAccessFile command. Maybe another file-access is needed? Which one?

As I understand by other posts, they always use a path and an extension, however, I have no idea that the path and extension would be in my case...

What I'm looking for, I a way to access the Kernel object namespacesKernel object namespaces

I know, there is this JNI example (Memorymap using JNI), however I would like to keep it simple and use nio (if even possible).

UPDATE

So I just tried the whole thing in C# and it was ridiculously easy, didn't take me more than 5 lines of code.

Answer 1

You need to use CreateFileMapping instead of OpenFileMapping. That way you will create an actual file on the disk which is associated with the file mapping.

Note: It is important to notice that using regular Read/Write methods will NOT be synchronized with a file mapping of a different process. So you still need to use something like MappedByteBuffer in Java

Answer 2

A file is a file, I agree with "Joachim Pileborg" that the Java program has not got the file in its working directory. Try

String working dir = System.getProperty("user.dir");

and make sure the file is in the correct path.