Re: Access to memory managed by C module over JNI

From:

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 09 Sep 2007 22:28:28 -0400

Message-ID:

<46e4abb1$0$90270$14726298@news.sunsite.dk>

Sune wrote:

Prereq:
---------------
- The lookup service (see below) implemented by a C module cannot be
re-written in Java ;-)
- The lookup service is to be loaded into the process of the Java
application, i.e. I want to avoid expensive IPC

You asked the same question in the C# group. Do you need the
solution in Java or C# or both ?

1)
I got a C module that organizes a big block of memory into a fairly
nice lookup service. This C module exposes a C API that I guess I
would best access from a Java application by using JNI, right? Are
there any other choices than JNI?

I believe JNI is the only solution.

From my understanding, Java being a pointerless language, Java client

code cannot by any means, by mistake, access the memory block managed
by the C module. Is this correct? Does JNI in any way make this less
true? For example, are there mechanisms in JNI that uses physical
pointers for efficiency?

A Java reference is more or less a pointer.

But Java throws exceptions if you try and go over an arrays
boundaries.

So you can not overwrite memory by accident.

JNI code is C code and it can overwrite just any other C code.

Arne