I need to construct a dynamic link library from existing C++ code. My understanding of C++ is rudimentary. I have, however, used JNI in the past to communicate with DLL's but they've always been DLL's provided to me by the vendor with well-documented API's so writing a wrapper and getting going has been easy.
Please keep in mind that I cannot use Runtime.exe() for this (at least I don't see how I could). The C++ code takes an observer which it notifies of messages when it has them. If there's some way to build the system so that I can use Runtime.exe, I'm open to that and feel that would be a better cross-platform solution anyway if I can get away with it. However, the target system that will use the DLL has already been built and it does work with an old DLL that I was able to secure for a previous version of the C++ code. Still, I'd be happy to modify the
Java side if it means getting a better and quicker solution from the C++ side.
The C++ source is from an open source project (
rtmidi). I know that Java has MIDI packages. We have found javax.sound to be unreliable when it comes to many people's systems - sound drops out when students are playing along with our accompaniments and MIDI cables get lost and / or cannot be found at all. I was able to use an old version of the rtmidi packages (someone made a wrapper for them for the old version) and prove that none of these problems exist with this package. However, there's a memory leak problem in the old C++ code, they've reported it as fixed but the project is not well supported and the build files are for the old version and don't work when I simply change the C++ source and update the directory name in the build scripts. I now need to make new build files and have no clue how to get a DLL out.
The instructions for building on Windows are to add the pre-compiler flags as such :
1. "__WINDOWS_MM__". This flag tells the C++ program which API to load when you call it. So this flag needs to be somewhere in my build command such that the DLL will automatically send this flag when I invoke "new" on the RtMidi.
2. "winmm.lib" is a dependency I think. However, I am not sure if this is needed if you're not using Visual C++. I would prefer to use MinGW if I can.
3. "multithreaded"
That's about the extent of the instructions they give. The rest just says "compiler specific".
So... can someone please tell me what I need to do (or resources I need to go study) to make a DLL that I can then call with JNI to invoke the DLL and C++ code?
My directory structure is /rtmidi-2.0.1 which has the RtMidi.h, RtError.h and RtMidi.cpp in it. There is an old MS Visual Studio build script for version 1.0 (not 2.0.1) provided but it won't make a DLL (but will compile) and my attempts at doing so have all failed. Can someone help me understand how to create this DLL in such a way that I can then write my JNI wrapper and be on my way, please? If I need to provide more info, please do let me know and thanks so much for your help!
