Signal-Android/qr/lib/src/main/java/org/signal/qr/kitkat/ScanningThread.java

package org.signal.qr.kitkat;

import androidx.annotation.NonNull;

import com.google.zxing.DecodeHintType;

import org.signal.core.util.logging.Log;
import org.signal.qr.QrProcessor;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;

import static org.signal.qr.kitkat.QrCameraView.PreviewCallback;
import static org.signal.qr.kitkat.QrCameraView.PreviewFrame;

public class ScanningThread extends Thread implements PreviewCallback {

  private static final String TAG = Log.tag(ScanningThread.class);

  private final QrProcessor                   processor    = new QrProcessor();
  private final AtomicReference<ScanListener> scanListener = new AtomicReference<>();
  private final Map<DecodeHintType, String>   hints        = new HashMap<>();

  private boolean      scanning = true;
  private PreviewFrame previewFrame;

  public void setCharacterSet(String characterSet) {
    hints.put(DecodeHintType.CHARACTER_SET, characterSet);
  }

  public void setScanListener(ScanListener scanListener) {
    this.scanListener.set(scanListener);
  }

  @Override
  public void onPreviewFrame(@NonNull PreviewFrame previewFrame) {
    try {
      synchronized (this) {
        this.previewFrame = previewFrame;
        this.notify();
      }
    } catch (RuntimeException e) {
      Log.w(TAG, e);
    }
  }

  @Override
  public void run() {
    while (true) {
      PreviewFrame ourFrame;

      synchronized (this) {
        while (scanning && previewFrame == null) {
          waitFor();
        }

        if (!scanning) return;
        else ourFrame = previewFrame;

        previewFrame = null;
      }

      String       data         = processor.getScannedData(ourFrame.getData(), ourFrame.getWidth(), ourFrame.getHeight());
      ScanListener scanListener = this.scanListener.get();

      if (data != null && scanListener != null) {
        scanListener.onQrDataFound(data);
        return;
      }
    }
  }

  public void stopScanning() {
    synchronized (this) {
      scanning = false;
      notify();
    }
  }

  private void waitFor() {
    try {
      wait(0);
    } catch (InterruptedException ie) {
      throw new AssertionError(ie);
    }
  }
}