Question

Exposition:

I am on Linux / Mac.

Part of my code is in Java, part of my code is in C++.

They both have the same file mmapped for fast communication.

I want to synchronize the Java & C++ code.

I know the following:

1) given two threads in Java, I can use Locks / monitors.

2) given one piece of code in Java, one in C++, I can have them synchronize over tcp/ip

3) given two pieces of C++ code, that have mmaped an area of memory, I can have them synchronize using gcc’s compare_and_swap on a integer in the mmaped region.

Question:

Given that part of my code is in Java, part of my code is in C++, can I somehow do (3) — does the JVM support some type of atomic compare & swap ? So both my Java & C++ code can use this integer as a lock of sorts?

Thanks!

Answer 1

You could write a small C/C++ library that only purpose is to sync with your C++ code (using conventional IPC sync objects). Then you could would this library from your java process using JNI.