Does JNI still work with Carbon on this basic level (FileManager,
Resource Manager). Btw i have to read and write resource Data. Or
should i forget it (and not go to work the next few days .. ;-)
We have JNI code that uses many Carbon APIs without problem
(e.g. SoundManager). What seems to be the big problem are
GUI elements -- do not use Carbon GUI components. In many
ways the Carbon event loop *can* coexist with the Cocoa JVM
(1.4+ JVMs are Cocoa based, 1.3* are Carbon based), for
example we use the Carbon Hot Keys API with success from a
1.4.2 JVM. There *are* threading issues to worry about with
the Carbon APIs. Earlier (1.3*) JVMs had a "Carbon Lock"
that JNI calls needed to acquire before calling Carbon APIs.
That is gone now. Also, many OS X APIs are not thread-safe,
and callers must ensure only one thread at a time calls them
(in some cases only one thread of a process may ever call
the API, and in some cases only the main AppKit thread may
call the API). Check the API documentation for thread safety
notices -- if there isn't one, then the API is not thread
safe. Apple's recommendation is to only call such APIs from
the main AppKit thread (which is different from the main
Java thread -- the AppKit thread is only visible to Java
when a native callback attaches to the JVM via JNI and calls
up to Java). The only way for 1.4 JNI code to call native
routines on the AppKit thread is via an NSObject method:
performSelectorOnMainThread (and only via Objective-C). If
you call such APIs from any thread, your code may work fine
99.999% of the time, but crash and burn if you get unlucky
and call it concurrently with native code on the AppKit
thread (most likely vs. the JVM itself).
If you just need to read and write resource forks, the
easiest route is to use the MacBinaryToolkit (mentioned
earlier), or use the "named fork" syntax (see the archives:
http://lists.apple.com/archives/java-dev/2004/Oct/msg00668.htmlhttp://lists.apple.com/archives/java-dev/2005/Aug/msg00107.html)
I've not tried calling the ResourceManager from JNI, I'd
guess it would be sufficient to ensure that only one of
the Java threads is calling it (using a conventional
Java monitor), I doubt that the Cocoa JVMs use the
ResourceManager at all. However, this is just a guess,
I've been wrong before.
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