Android Open Source - Jello Vanilla Histogram

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Back to project page Jello.

License

The source code is released under:

Apache License

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Java Source Code

package com.atteo.jello.space;
/*from ww w  .  j  av a2s  .c om*/
import java.util.ArrayList;

import com.google.inject.Inject;
import com.google.inject.Singleton;
import com.google.inject.name.Named;

@Singleton
public class VanillaHistogram implements NextFitHistogram {
  private final short classSize;
  private final ArrayList<Integer> witnesses;
  private final ArrayList<Integer> counts;
  private int count;
  private final int histogramClasses;

  @Inject
  public VanillaHistogram(@Named("pageSize") final short pageSize,
      @Named("nextFitHistogramClasses") int histogramClasses) {

    if (pageSize % histogramClasses != 0)
      throw new IllegalArgumentException(
          "histogramClasses should divide pageSize");

    classSize = (short) (pageSize / histogramClasses);

    histogramClasses++; // empty pages have a separate class

    this.histogramClasses = histogramClasses;
    count = 0;

    witnesses = new ArrayList<Integer>();
    counts = new ArrayList<Integer>();

    for (int i = 0; i < histogramClasses; i++) {
      witnesses.add(-1);
      counts.add(0);
    }

  }

  public short getClassSize() {
    return classSize;
  }

  public int getWitness(final short freeSpace) {
    int loc = classFor(freeSpace);
    loc++;
    if (loc == histogramClasses)
      loc = histogramClasses - 1;

    boolean found = false;

    while (loc < histogramClasses) {
      if (counts.get(loc) > 0) {
        found = true;
        final int w = witnesses.get(loc);
        if (w != -1)
          return w;
      }
      loc++;
    }

    if (found == false)
      return NextFitHistogram.NO_PAGE;

    return NextFitHistogram.NO_WITNESS;
  }

  public void update(final int id, final short previousFreeSpace,
      final short freeSpace) {
    if (previousFreeSpace != -1) {
      final int loc = classFor(previousFreeSpace);
      counts.set(loc, counts.get(loc) - 1);
      if (witnesses.get(loc) == id)
        witnesses.set(loc, -1);

      count--;
    }

    if (freeSpace == -1)
      return;

    final int loc = classFor(freeSpace);
    counts.set(loc, counts.get(loc) + 1);
    witnesses.set(loc, id);
    count++;
  }

  private int classFor(final int freeSpace) {
    return freeSpace / classSize;
  }
}

Java Source Code List