Question

I have an input byte array which I would like to feed to the standard input of an external program (Process). Also, I would like to collect the output in a byte array.

What is the most elegant way to do this? PipedInputStream/PipedOutputStream? nio.channels.Pipe?

Sample code would be a plus because I can’t really figure out how to do this in a good way…

Answer 1

Combining PipedInputStream with PipedOutputStream and Peter’s MultiOutputStream from another post here, you can get the following:

final int CAPCITY = 4096;
final int PIPE_SIZE = 4096;

PipedOutputStream pout = new PipedOutputStream();
ByteArrayOutputStream bout = new ByteArrayOutputStream(CAPACITY);
MultiOutputStream multiOs= new MultiOutputStream(pout, bout);

PipedInputStream is = new PipedInputStream(pout, PIPE_SIZE);

Now, if you execute:

byte[] bytes = new bytes[1024];
multiOs.write(bytes, 0, 1024);

You feed your PipedInputStream, optionally handing the reference over to another process, i.e. Java Thread. Simultaneoulsy, you write into a byte array, which can be queried by:

bytes[] written = bout.toByteArray();