Reading line by line strings from multiple byte arrays in Java

Question

I have a JNI function "byte[] read()" which reads some bytes from a particular hardware interface and returns a new byte array each time it is called. The read data is always ASCII text data and has '\n' for line termination.

I'd like to convert these MULTIPLE byte arrays read from the function into an InputStream so I may print them line by line.

Something like:

while(running) {
    byte[] in = read(); // Can very well return in complete line
    SomeInputStream.setMoreIncoming(in);
    if(SomeInputStream.hasLineData())
        System.out.println(SomeInputSream.readline());
}

How do I do that?

Hardware interface provides bytes but you say "line". Lines of text termibated by '\n', in which character encoding? — Aubin
– Aubin, Commented Nov 11, 2012 at 18:38
I should have clarified. Only plain ASCII text data is received and lines of text are terminated by '\n'. — sharjeel
– sharjeel, Commented Nov 11, 2012 at 18:46

Aubin · Accepted Answer · 2012-11-11 22:58:58Z

2

You can choose the class java.io.Reader as base class overriding the abstract method int read( char[] cbuf, int off, int len) to build your own character oriented stream.

Sample code:

import java.io.IOException;
import java.io.Reader;

public class CustomReader extends Reader { // FIXME: choose a better name

   native byte[] native_call(); // Your JNI code here

   @Override public int read( char[] cbuf, int off, int len ) throws IOException {
      if( this.buffer == null ) {
         return -1;
      }
      final int count = len - off;
      int remaining = count;
      do {
         while( remaining > 0 && this.index < this.buffer.length ) {
            cbuf[off++] = (char)this.buffer[this.index++];
            --remaining;
         }
         if( remaining > 0 ) {
            this.buffer = native_call(); // Your JNI code here
            this.index  = 0;
         }
      } while( this.buffer != null && remaining > 0 );
      return count - remaining;
   }

   @Override
   public void close() throws IOException {
      // FIXME: release hardware resources
   }

   private int     index  = 0;
   private byte[]  buffer = native_call();

}

edited Nov 11, 2012 at 22:58

answered Nov 11, 2012 at 18:44

Aubin

14.9k11 gold badges67 silver badges89 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

sharjeel Over a year ago

Aubin; it is only text. Could you please provider a code snippet?

sharjeel Over a year ago

Thanks. I was hoping that I wouldn't have to write such complex code for seemingly very straightforward problem but I guess I can't escape that

Collectives™ on Stack Overflow

Reading line by line strings from multiple byte arrays in Java

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related