Re: Read a single byte from stdin

From:
Tom Anderson <twic@urchin.earth.li>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 14 Jul 2009 08:24:12 +0100
Message-ID:
<alpine.DEB.1.10.0907132358570.25982@urchin.earth.li>
On Sun, 12 Jul 2009, Mike Schilling wrote:

Arne Vajh?j wrote:

Lew wrote:

Lew wrote:

Yep. InputStream and the Reader returned by Console have
essentially
the same set of read() operations. Console does at least have
readLine() and a non-echoing readPassword().


However, InputStream does not, nor does it always have to be
buffered. Again, I trust that your tests show that System.in is
actually line buffered.


I would put it another way.

If System.in is line buffered on one or more systems, then
a portable program can not not assume it is not line buffered.

Implementation specific does not solve hos problem. He need
something that is documented to work in all compliant
implementations.


Right. In other words, if the JRE doesn't provide this (which to the
best of my knowledge, it does not), the only solution is
system-specific JNI. In fact, JRE support for this feature amounts to
a requirement that JRE implementors provide the system-specific JNI
for us.

Having said that, suppose for the sake of argument that you'd
constructed seperate JNI for Windows, Mac, and Linux [1], and were happy
that you'd now solved the problem for all of your likely users. What's
the best way to package your application? Do you need three different
versions, or is there some magic that will allow the app to locate and
load the proper version of the JNI library at runtime?


There's no chance that Java will load the wrong library in this case, as
those three platforms have different naming conventions for libraries (not
to mention different formats): you'd have SCHILLING.DLL,
libschilling.dylib, and libschilling.so, respectively. You might have a
problem if you wanted to support multiple unices, especially if they all
used the same binary format - i don't know how you'd disambiguate two ELFs
called libschilling.so where one was for linux and one for FreeBSD.

However, there is a bigger problem, which i think renders the name clash
moot: how do you get the JVM to find your library. You can't just put it
somewhere on disk and hope. Unless the JVM has some particular mechanism
i'm not aware of for finding libraries (which is more than possible),
you'll have to use the local OS's method, eg setting LD_LIBRARY_PATH on
linux - in which case you can sidestep the ambiguity problem by putting
the different versions of your library in different places.

tom

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