content: /**
   * Copyright 2004-2006 DFKI GmbH.
   * All Rights Reserved.  Use is subject to license terms.
   * <p/>
   * This file is part of MARY TTS.
   * <p/>
   * MARY TTS is free software: you can redistribute it and/or modify
   * it under the terms of the GNU Lesser General Public License as published by
   * the Free Software Foundation, version 3 of the License.
   * <p/>
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU Lesser General Public License for more details.
   * <p/>
   * You should have received a copy of the GNU Lesser General Public License
   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  package marytts.util.data;
  
  import marytts.util.data.audio.DDSAudioInputStream;
  import marytts.util.math.MathUtils;
  
  public class NoiseDoubleDataSource extends BaseDoubleDataSource {
      protected long n;
      protected double amplitude;
  
      /**
       * Construct an double data source from which a given amount of
       * white noise can be read.
       *
       * @param n  the number of samles samples to be read
       * @param dB the energy of the noise, in dB relative to max amplitude.
       *           This must be non-positive, and will typically be between -100 and -3.
       */
      public NoiseDoubleDataSource(long n, double dB) {
          super();
          this.n = n;
          dataLength = n;
          if (dB > 0) {
              throw new IllegalArgumentException("Energy must be non-positive");
          }
          this.amplitude = DDSAudioInputStream.MAX_AMPLITUDE * Math.sqrt(MathUtils.db2linear(dB));
      }
  
      @Override
      public boolean hasMoreData() {
          return n > 0;
      }
  
      /**
       * The number of doubles that can currently be read from this
       * double data source without blocking. This number can change over time.
       *
       * @return the number of doubles that can currently be read without blocking
       */
      @Override
      public int available() {
          return (int) n;
      }
  
      @Override
      public int getData(double[] target, int targetPos, int length) {
          if (target.length - targetPos < length) {
              throw new IllegalArgumentException("Target array cannot hold enough data (" + (target.length - targetPos) + " left, but " + length + " requested)");
          }
          int toCopy = (int) Math.min(length, n);
          for (int i = targetPos; i < targetPos + toCopy; i++) {
              target[i] = 2 * (0.5 - Math.random()) * amplitude;
          }
          n -= toCopy;
          return toCopy;
      }
  
  }
  
  