code: /*
   * Copyright (C) 2013 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.lody.virtual.helper.collection;
  
  import android.util.Log;
  
  import java.lang.reflect.Array;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Set;
  
  
  /**
   * ArraySet is a generic set data structure that is designed to be more memory efficient than a
   * traditional {@link java.util.HashSet}.  The design is very similar to
   * {@link ArrayMap}, with all of the caveats described there.  This implementation is
   * separate from ArrayMap, however, so the Object array contains only one item for each
   * entry in the set (instead of a pair for a mapping).
   *
   * <p>Note that this implementation is not intended to be appropriate for data structures
   * that may contain large numbers of items.  It is generally slower than a traditional
   * HashSet, since lookups require a binary search and adds and removes require inserting
   * and deleting entries in the array.  For containers holding up to hundreds of items,
   * the performance difference is not significant, less than 50%.</p>
   *
   * <p>Because this container is intended to better balance memory use, unlike most other
   * standard Java containers it will shrink its array as items are removed from it.  Currently
   * you have no control over this shrinking -- if you set a capacity and then remove an
   * item, it may reduce the capacity to better match the current size.  In the future an
   * explicit call to set the capacity should turn off this aggressive shrinking behavior.</p>
   */
  public final class ArraySet<E> implements Collection<E>, Set<E> {
      private static final boolean DEBUG = false;
      private static final String TAG = "ArraySet";
  
      /**
       * The minimum amount by which the capacity of a ArraySet will increase.
       * This is tuned to be relatively space-efficient.
       */
      private static final int BASE_SIZE = 4;
  
      /**
       * Maximum number of entries to have in array caches.
       */
      private static final int CACHE_SIZE = 10;
  
      /**
       * Caches of small array objects to avoid spamming garbage.  The cache
       * Object[] variable is a pointer to a linked list of array objects.
       * The first entry in the array is a pointer to the next array in the
       * list; the second entry is a pointer to the int[] hash code array for it.
       */
      static Object[] mBaseCache;
      static int mBaseCacheSize;
      static Object[] mTwiceBaseCache;
      static int mTwiceBaseCacheSize;
  
      int[] mHashes;
      Object[] mArray;
      int mSize;
      MapCollections<E, E> mCollections;
  
      /**
       * Create a new empty ArraySet.  The default capacity of an array map is 0, and
       * will grow once items are added to it.
       */
      public ArraySet() {
          mHashes = ContainerHelpers.EMPTY_INTS;
          mArray = ContainerHelpers.EMPTY_OBJECTS;
          mSize = 0;
      }
  
      /**
       * Create a new ArraySet with a given initial capacity.
       */
      public ArraySet(int capacity) {
          if (capacity == 0) {
              mHashes = ContainerHelpers.EMPTY_INTS;
              mArray = ContainerHelpers.EMPTY_OBJECTS;
          } else {
              allocArrays(capacity);
          }
          mSize = 0;
      }
  
      /**
       * Create a new ArraySet with the mappings from the given ArraySet.
       */
      public ArraySet(ArraySet<E> set) {
          this();
          if (set != null) {
              addAll(set);
          }
      }
  
      /** {@hide} */
      public ArraySet(Collection<E> set) {
          this();
          if (set != null) {
              addAll(set);
          }
      }
  
      private static void freeArrays(final int[] hashes, final Object[] array, final int size) {
          if (hashes.length == (BASE_SIZE*2)) {
              synchronized (ArraySet.class) {
                  if (mTwiceBaseCacheSize < CACHE_SIZE) {
                      array[0] = mTwiceBaseCache;
                      array[1] = hashes;
                      for (int i=size-1; i>=2; i--) {
                          array[i] = null;
                      }
                      mTwiceBaseCache = array;
                      mTwiceBaseCacheSize++;
                      if (DEBUG) Log.d(TAG, "Storing 2x cache " + array
                              + " now have " + mTwiceBaseCacheSize + " entries");
                  }
              }
          } else if (hashes.length == BASE_SIZE) {
              synchronized (ArraySet.class) {
                  if (mBaseCacheSize < CACHE_SIZE) {
                      array[0] = mBaseCache;
                      array[1] = hashes;
                      for (int i=size-1; i>=2; i--) {
                          array[i] = null;
                      }
                      mBaseCache = array;
                      mBaseCacheSize++;
                      if (DEBUG) Log.d(TAG, "Storing 1x cache " + array
                              + " now have " + mBaseCacheSize + " entries");
                  }
              }
          }
      }
  
      private int indexOf(Object key, int hash) {
          final int N = mSize;
  
          // Important fast case: if nothing is in here, nothing to look for.
          if (N == 0) {
              return ~0;
          }
  
          int index = ContainerHelpers.binarySearch(mHashes, N, hash);
  
          // If the hash code wasn't found, then we have no entry for this key.
          if (index < 0) {
              return index;
          }
  
          // If the key at the returned index matches, that's what we want.
          if (key.equals(mArray[index])) {
              return index;
          }
  
          // Search for a matching key after the index.
          int end;
          for (end = index + 1; end < N && mHashes[end] == hash; end++) {
              if (key.equals(mArray[end])) return end;
          }
  
          // Search for a matching key before the index.
          for (int i = index - 1; i >= 0 && mHashes[i] == hash; i--) {
              if (key.equals(mArray[i])) return i;
          }
  
          // Key not found -- return negative value indicating where a
          // new entry for this key should go.  We use the end of the
          // hash chain to reduce the number of array entries that will
          // need to be copied when inserting.
          return ~end;
      }
  
      private int indexOfNull() {
          final int N = mSize;
  
          // Important fast case: if nothing is in here, nothing to look for.
          if (N == 0) {
              return ~0;
          }
  
          int index = ContainerHelpers.binarySearch(mHashes, N, 0);
  
          // If the hash code wasn't found, then we have no entry for this key.
          if (index < 0) {
              return index;
          }
  
          // If the key at the returned index matches, that's what we want.
          if (null == mArray[index]) {
              return index;
          }
  
          // Search for a matching key after the index.
          int end;
          for (end = index + 1; end < N && mHashes[end] == 0; end++) {
              if (null == mArray[end]) return end;
          }
  
          // Search for a matching key before the index.
          for (int i = index - 1; i >= 0 && mHashes[i] == 0; i--) {
              if (null == mArray[i]) return i;
          }
  
          // Key not found -- return negative value indicating where a
          // new entry for this key should go.  We use the end of the
          // hash chain to reduce the number of array entries that will
          // need to be copied when inserting.
          return ~end;
      }
  
      private void allocArrays(final int size) {
          if (size == (BASE_SIZE*2)) {
              synchronized (ArraySet.class) {
                  if (mTwiceBaseCache != null) {
                      final Object[] array = mTwiceBaseCache;
                      mArray = array;
                      mTwiceBaseCache = (Object[])array[0];
                      mHashes = (int[])array[1];
                      array[0] = array[1] = null;
                      mTwiceBaseCacheSize--;
                      if (DEBUG) Log.d(TAG, "Retrieving 2x cache " + mHashes
                              + " now have " + mTwiceBaseCacheSize + " entries");
                      return;
                  }
              }
          } else if (size == BASE_SIZE) {
              synchronized (ArraySet.class) {
                  if (mBaseCache != null) {
                      final Object[] array = mBaseCache;
                      mArray = array;
                      mBaseCache = (Object[])array[0];
                      mHashes = (int[])array[1];
                      array[0] = array[1] = null;
                      mBaseCacheSize--;
                      if (DEBUG) Log.d(TAG, "Retrieving 1x cache " + mHashes
                              + " now have " + mBaseCacheSize + " entries");
                      return;
                  }
              }
          }
  
          mHashes = new int[size];
          mArray = new Object[size];
      }
  
      /**
       * Make the array map empty.  All storage is released.
       */
      @Override
      public void clear() {
          if (mSize != 0) {
              freeArrays(mHashes, mArray, mSize);
              mHashes = ContainerHelpers.EMPTY_INTS;
              mArray = ContainerHelpers.EMPTY_OBJECTS;
              mSize = 0;
          }
      }
  
      /**
       * Ensure the array map can hold at least <var>minimumCapacity</var>
       * items.
       */
      public void ensureCapacity(int minimumCapacity) {
          if (mHashes.length < minimumCapacity) {
              final int[] ohashes = mHashes;
              final Object[] oarray = mArray;
              allocArrays(minimumCapacity);
              if (mSize > 0) {
                  System.arraycopy(ohashes, 0, mHashes, 0, mSize);
                  System.arraycopy(oarray, 0, mArray, 0, mSize);
              }
              freeArrays(ohashes, oarray, mSize);
          }
      }
  
      /**
       * Check whether a value exists in the set.
       *
       * @param key The value to search for.
       * @return Returns true if the value exists, else false.
       */
      @Override
      public boolean contains(Object key) {
          return indexOf(key) >= 0;
      }
  
      /**
       * Returns the index of a value in the set.
       *
       * @param key The value to search for.
       * @return Returns the index of the value if it exists, else a negative integer.
       */
      public int indexOf(Object key) {
          return key == null ? indexOfNull() : indexOf(key, key.hashCode());
      }
  
      /**
       * Return the value at the given index in the array.
       * @param index The desired index, must be between 0 and {@link #size()}-1.
       * @return Returns the value stored at the given index.
       */
      public E valueAt(int index) {
          return (E)mArray[index];
      }
  
      /**
       * Return true if the array map contains no items.
       */
      @Override
      public boolean isEmpty() {
          return mSize <= 0;
      }
  
      /**
       * Adds the specified object to this set. The set is not modified if it
       * already contains the object.
       *
       * @param value the object to add.
       * @return {@code true} if this set is modified, {@code false} otherwise.
       * @throws ClassCastException
       *             when the class of the object is inappropriate for this set.
       */
      @Override
      public boolean add(E value) {
          final int hash;
          int index;
          if (value == null) {
              hash = 0;
              index = indexOfNull();
          } else {
              hash = value.hashCode();
              index = indexOf(value, hash);
          }
          if (index >= 0) {
              return false;
          }
  
          index = ~index;
          if (mSize >= mHashes.length) {
              final int n = mSize >= (BASE_SIZE*2) ? (mSize+(mSize>>1))
                      : (mSize >= BASE_SIZE ? (BASE_SIZE*2) : BASE_SIZE);
  
              if (DEBUG) Log.d(TAG, "add: grow from " + mHashes.length + " to " + n);
  
              final int[] ohashes = mHashes;
              final Object[] oarray = mArray;
              allocArrays(n);
  
              if (mHashes.length > 0) {
                  if (DEBUG) Log.d(TAG, "add: copy 0-" + mSize + " to 0");
                  System.arraycopy(ohashes, 0, mHashes, 0, ohashes.length);
                  System.arraycopy(oarray, 0, mArray, 0, oarray.length);
              }
  
              freeArrays(ohashes, oarray, mSize);
          }
  
          if (index < mSize) {
              if (DEBUG) Log.d(TAG, "add: move " + index + "-" + (mSize-index)
                      + " to " + (index+1));
              System.arraycopy(mHashes, index, mHashes, index + 1, mSize - index);
              System.arraycopy(mArray, index, mArray, index + 1, mSize - index);
          }
  
          mHashes[index] = hash;
          mArray[index] = value;
          mSize++;
          return true;
      }
  
      /**
       * Perform a {@link #add(Object)} of all values in <var>array</var>
       * @param array The array whose contents are to be retrieved.
       */
      public void addAll(ArraySet<? extends E> array) {
          final int N = array.mSize;
          ensureCapacity(mSize + N);
          if (mSize == 0) {
              if (N > 0) {
                  System.arraycopy(array.mHashes, 0, mHashes, 0, N);
                  System.arraycopy(array.mArray, 0, mArray, 0, N);
                  mSize = N;
              }
          } else {
              for (int i=0; i<N; i++) {
                  add(array.valueAt(i));
              }
          }
      }
  
      /**
       * Removes the specified object from this set.
       *
       * @param object the object to remove.
       * @return {@code true} if this set was modified, {@code false} otherwise.
       */
      @Override
      public boolean remove(Object object) {
          final int index = indexOf(object);
          if (index >= 0) {
              removeAt(index);
              return true;
          }
          return false;
      }
  
      /**
       * Remove the key/value mapping at the given index.
       * @param index The desired index, must be between 0 and {@link #size()}-1.
       * @return Returns the value that was stored at this index.
       */
      public E removeAt(int index) {
          final Object old = mArray[index];
          if (mSize <= 1) {
              // Now empty.
              if (DEBUG) Log.d(TAG, "remove: shrink from " + mHashes.length + " to 0");
              freeArrays(mHashes, mArray, mSize);
              mHashes = ContainerHelpers.EMPTY_INTS;
              mArray = ContainerHelpers.EMPTY_OBJECTS;
              mSize = 0;
          } else {
              if (mHashes.length > (BASE_SIZE*2) && mSize < mHashes.length/3) {
                  // Shrunk enough to reduce size of arrays.  We don't allow it to
                  // shrink smaller than (BASE_SIZE*2) to avoid flapping between
                  // that and BASE_SIZE.
                  final int n = mSize > (BASE_SIZE*2) ? (mSize + (mSize>>1)) : (BASE_SIZE*2);
  
                  if (DEBUG) Log.d(TAG, "remove: shrink from " + mHashes.length + " to " + n);
  
                  final int[] ohashes = mHashes;
                  final Object[] oarray = mArray;
                  allocArrays(n);
  
                  mSize--;
                  if (index > 0) {
                      if (DEBUG) Log.d(TAG, "remove: copy from 0-" + index + " to 0");
                      System.arraycopy(ohashes, 0, mHashes, 0, index);
                      System.arraycopy(oarray, 0, mArray, 0, index);
                  }
                  if (index < mSize) {
                      if (DEBUG) Log.d(TAG, "remove: copy from " + (index+1) + "-" + mSize
                              + " to " + index);
                      System.arraycopy(ohashes, index + 1, mHashes, index, mSize - index);
                      System.arraycopy(oarray, index + 1, mArray, index, mSize - index);
                  }
              } else {
                  mSize--;
                  if (index < mSize) {
                      if (DEBUG) Log.d(TAG, "remove: move " + (index+1) + "-" + mSize
                              + " to " + index);
                      System.arraycopy(mHashes, index + 1, mHashes, index, mSize - index);
                      System.arraycopy(mArray, index + 1, mArray, index, mSize - index);
                  }
                  mArray[mSize] = null;
              }
          }
          return (E)old;
      }
  
      /**
       * Perform a {@link #remove(Object)} of all values in <var>array</var>
       * @param array The array whose contents are to be removed.
       */
      public boolean removeAll(ArraySet<? extends E> array) {
          // TODO: If array is sufficiently large, a marking approach might be beneficial. In a first
          //       pass, use the property that the sets are sorted by hash to make this linear passes
          //       (except for hash collisions, which means worst case still n*m), then do one
          //       collection pass into a new array. This avoids binary searches and excessive memcpy.
          final int N = array.mSize;
  
          // Note: ArraySet does not make thread-safety guarantees. So instead of OR-ing together all
          //       the single results, compare size before and after.
          final int originalSize = mSize;
          for (int i = 0; i < N; i++) {
              remove(array.valueAt(i));
          }
          return originalSize != mSize;
      }
  
      /**
       * Return the number of items in this array map.
       */
      @Override
      public int size() {
          return mSize;
      }
  
      @Override
      public Object[] toArray() {
          Object[] result = new Object[mSize];
          System.arraycopy(mArray, 0, result, 0, mSize);
          return result;
      }
  
      @Override
      public <T> T[] toArray(T[] array) {
          if (array.length < mSize) {
              @SuppressWarnings("unchecked") T[] newArray
                  = (T[]) Array.newInstance(array.getClass().getComponentType(), mSize);
              array = newArray;
          }
          System.arraycopy(mArray, 0, array, 0, mSize);
          if (array.length > mSize) {
              array[mSize] = null;
          }
          return array;
      }
  
      /**
       * {@inheritDoc}
       *
       * <p>This implementation returns false if the object is not a set, or
       * if the sets have different sizes.  Otherwise, for each value in this
       * set, it checks to make sure the value also exists in the other set.
       * If any value doesn't exist, the method returns false; otherwise, it
       * returns true.
       */
      @Override
      public boolean equals(Object object) {
          if (this == object) {
              return true;
          }
          if (object instanceof Set) {
              Set<?> set = (Set<?>) object;
              if (size() != set.size()) {
                  return false;
              }
  
              try {
                  for (int i=0; i<mSize; i++) {
                      E mine = valueAt(i);
                      if (!set.contains(mine)) {
                          return false;
                      }
                  }
              } catch (NullPointerException ignored) {
                  return false;
              } catch (ClassCastException ignored) {
                  return false;
              }
              return true;
          }
          return false;
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public int hashCode() {
          final int[] hashes = mHashes;
          int result = 0;
          for (int i = 0, s = mSize; i < s; i++) {
              result += hashes[i];
          }
          return result;
      }
  
      /**
       * {@inheritDoc}
       *
       * <p>This implementation composes a string by iterating over its values. If
       * this set contains itself as a value, the string "(this Set)"
       * will appear in its place.
       */
      @Override
      public String toString() {
          if (isEmpty()) {
              return "{}";
          }
  
          StringBuilder buffer = new StringBuilder(mSize * 14);
          buffer.append('{');
          for (int i=0; i<mSize; i++) {
              if (i > 0) {
                  buffer.append(", ");
              }
              Object value = valueAt(i);
              if (value != this) {
                  buffer.append(value);
              } else {
                  buffer.append("(this Set)");
              }
          }
          buffer.append('}');
          return buffer.toString();
      }
  
      // ------------------------------------------------------------------------
      // Interop with traditional Java containers.  Not as efficient as using
      // specialized collection APIs.
      // ------------------------------------------------------------------------
  
      private MapCollections<E, E> getCollection() {
          if (mCollections == null) {
              mCollections = new MapCollections<E, E>() {
                  @Override
                  protected int colGetSize() {
                      return mSize;
                  }
  
                  @Override
                  protected Object colGetEntry(int index, int offset) {
                      return mArray[index];
                  }
  
                  @Override
                  protected int colIndexOfKey(Object key) {
                      return indexOf(key);
                  }
  
                  @Override
                  protected int colIndexOfValue(Object value) {
                      return indexOf(value);
                  }
  
                  @Override
                  protected Map<E, E> colGetMap() {
                      throw new UnsupportedOperationException("not a map");
                  }
  
                  @Override
                  protected void colPut(E key, E value) {
                      add(key);
                  }
  
                  @Override
                  protected E colSetValue(int index, E value) {
                      throw new UnsupportedOperationException("not a map");
                  }
  
                  @Override
                  protected void colRemoveAt(int index) {
                      removeAt(index);
                  }
  
                  @Override
                  protected void colClear() {
                      clear();
                  }
              };
          }
          return mCollections;
      }
  
      /**
       * Return an {@link java.util.Iterator} over all values in the set.
       *
       * <p><b>Note:</b> this is a fairly inefficient way to access the array contents, it
       * requires generating a number of temporary objects and allocates additional state
       * information associated with the container that will remain for the life of the container.</p>
       */
      @Override
      public Iterator<E> iterator() {
          return getCollection().getKeySet().iterator();
      }
  
      /**
       * Determine if the array set contains all of the values in the given collection.
       * @param collection The collection whose contents are to be checked against.
       * @return Returns true if this array set contains a value for every entry
       * in <var>collection</var>, else returns false.
       */
      @Override
      public boolean containsAll(Collection<?> collection) {
          Iterator<?> it = collection.iterator();
          while (it.hasNext()) {
              if (!contains(it.next())) {
                  return false;
              }
          }
          return true;
      }
  
      /**
       * Perform an {@link #add(Object)} of all values in <var>collection</var>
       * @param collection The collection whose contents are to be retrieved.
       */
      @Override
      public boolean addAll(Collection<? extends E> collection) {
          ensureCapacity(mSize + collection.size());
          boolean added = false;
          for (E value : collection) {
              added |= add(value);
          }
          return added;
      }
  
      /**
       * Remove all values in the array set that exist in the given collection.
       * @param collection The collection whose contents are to be used to remove values.
       * @return Returns true if any values were removed from the array set, else false.
       */
      @Override
      public boolean removeAll(Collection<?> collection) {
          boolean removed = false;
          for (Object value : collection) {
              removed |= remove(value);
          }
          return removed;
      }
  
      /**
       * Remove all values in the array set that do <b>not</b> exist in the given collection.
       * @param collection The collection whose contents are to be used to determine which
       * values to keep.
       * @return Returns true if any values were removed from the array set, else false.
       */
      @Override
      public boolean retainAll(Collection<?> collection) {
          boolean removed = false;
          for (int i=mSize-1; i>=0; i--) {
              if (!collection.contains(mArray[i])) {
                  removeAt(i);
                  removed = true;
              }
          }
          return removed;
      }
  }
  