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jDLMS is a library implementing the DLMS/COSEM (IEC 62056) communication standard.

There is a newer version: 1.8.0

package org.openmuc.jdlms;

import java.io.IOException;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;

import org.openmuc.jdlms.internal.APdu;

class APduBlockingQueue {

    private IOException ioException;

    private final BlockingQueue queue;

    public APduBlockingQueue() {
        this.queue = new LinkedBlockingQueue<>();
    }

    public void putError(IOException e) {
        this.ioException = e;
        put(new APdu(null, null));
    }

    public void put(APdu aPdu) {
        try {
            this.queue.put(aPdu);
        } catch (InterruptedException e) {
            // ignore this here
        }
    }

    public APdu poll(long timeout, TimeUnit unit) throws InterruptedException, IOException {
        throwExIfExists();
        APdu poll = this.queue.poll(timeout, unit);
        throwExIfExists();
        return poll;
    }

    private void throwExIfExists() throws IOException {
        if (this.ioException != null) {
            IOException ex = this.ioException;
            this.ioException = null;

            throw ex;
        }
    }

    public APdu take() throws InterruptedException, IOException {
        throwExIfExists();
        APdu aPdu = this.queue.take();
        throwExIfExists();
        return aPdu;
    }

}