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package DataStructures.Buffers;

import java.util.Random;

import java.util.concurrent.atomic.AtomicInteger;

public class CircularBuffer {

private char[] _buffer;

public final int _buffer_size;

private int _write_index = 0;

private int _read_index = 0;

private AtomicInteger _readable_data = new AtomicInteger(0);

public CircularBuffer(int buffer_size) {

if (!IsPowerOfTwo(buffer_size)) {

throw new IllegalArgumentException();

}

this._buffer_size = buffer_size;

_buffer = new char[buffer_size];

}

private boolean IsPowerOfTwo(int i) {

return (i & (i - 1)) == 0;

}

private int getTrueIndex(int i) {

return i % _buffer_size;

}

public Character readOutChar() {

Character result = null;

//if we have data to read

if (_readable_data.get() > 0) {

result = new Character(_buffer[getTrueIndex(_read_index)]);

_readable_data.decrementAndGet();

_read_index++;

}

return result;

}

public boolean writeToCharBuffer(char c) {

boolean result = false;

//if we can write to the buffer

if (_readable_data.get() < _buffer_size) {

//write to buffer

_buffer[getTrueIndex(_write_index)] = c;

_readable_data.incrementAndGet();

_write_index++;

result = true;

}

return result;

}

private static class TestWriteWorker implements Runnable {

String _alphabet = "abcdefghijklmnopqrstuvwxyz0123456789";

Random _random = new Random();

CircularBuffer _buffer;

public TestWriteWorker(CircularBuffer cb) {

this._buffer = cb;

}

private char getRandomChar() {

return _alphabet.charAt(_random.nextInt(_alphabet.length()));

}

public void run() {

while (!Thread.interrupted()) {

if (!_buffer.writeToCharBuffer(getRandomChar())) {

Thread.yield();

try {

Thread.sleep(10);

} catch (InterruptedException e) {

return;

}

}

}

}

}

private static class TestReadWorker implements Runnable {

CircularBuffer _buffer;

public TestReadWorker(CircularBuffer cb) {

this._buffer = cb;

}

@Override

public void run() {

System.out.println("Printing Buffer:");

while (!Thread.interrupted()) {

Character c = _buffer.readOutChar();

if (c != null) {

System.out.print(c.charValue());

} else {

Thread.yield();

try {

Thread.sleep(10);

} catch (InterruptedException e) {

System.out.println();

return;

}

}

}

}

}

public static void main(String[] args) throws InterruptedException {

int buffer_size = 1024;

//create circular buffer

CircularBuffer cb = new CircularBuffer(buffer_size);

//create threads that read and write the buffer.

Thread write_thread = new Thread(new TestWriteWorker(cb));

Thread read_thread = new Thread(new TestReadWorker(cb));

read_thread.start();

write_thread.start();

//wait some amount of time

Thread.sleep(10000);

//interrupt threads and exit

write_thread.interrupt();

read_thread.interrupt();

}

}