Initial import

[jpf-core.git] / src / main / gov / nasa / jpf / util / DynamicObjectArray.java

diff --git a/src/main/gov/nasa/jpf/util/DynamicObjectArray.java b/src/main/gov/nasa/jpf/util/DynamicObjectArray.java
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+++ b/src/main/gov/nasa/jpf/util/DynamicObjectArray.java
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+/*
+ * Copyright (C) 2014, United States Government, as represented by the
+ * Administrator of the National Aeronautics and Space Administration.
+ * All rights reserved.
+ *
+ * The Java Pathfinder core (jpf-core) platform is 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 gov.nasa.jpf.util;
+
+import java.util.Iterator;
+
+/**
+ * simplistic Object array that differentiates from ArrayList by
+ * using chunks instead of exponential growth, thus efficiently dealing
+ * with huge, potentially sparse arrays
+ *
+ * the motivation for this class is memory optimization, i.e. space efficient
+ * storage of potentially huge arrays without good a-priori size guesses
+ *
+ * this class is awfully lifted from DynamicIntArray (same motivation, but
+ * primitive types - not much factorizable functionality w/o excessive
+ * casting/boxing)
+ *
+ * the API of this class is between a primitive array and a AbstractList. Since
+ * it handles Objects, we could turn this into a Collection (and probably should)
+ *
+ * NOTE: like standard Collection implementations/arrays, this class is not
+ * synchronized
+ */
+
+public final class DynamicObjectArray<E> implements Iterable<E> {
+  final static int DEFAULT_CHUNKBITS = 8;
+  final static int INIT_CHUNKS = 16;
+
+  /** growth strategy */
+  Growth growth;
+
+  /** our allocation sizes */
+  int chunkBits;
+  int nPerChunk; // just a cache for (1<<chunkBits)
+
+  /** mask for index within chunk */
+  int chunkMask;
+
+  /** the real data. limitations in generics prevent use of E[][] */
+  Object[][] data;
+
+  /** the maximum index set so far */
+  int maxIndex = -1;
+
+  class DynIterator implements Iterator<E> {
+    int i;
+
+    @Override
+       public boolean hasNext() {
+      return (i<size());
+    }
+
+    @Override
+       public E next() {
+      return get(i++);
+    }
+
+    @Override
+       public void remove() {
+      throw new UnsupportedOperationException();
+    }
+  }
+
+  public DynamicObjectArray () {
+    this(Growth.defaultGrowth, DEFAULT_CHUNKBITS, INIT_CHUNKS);
+  }
+
+  /**
+   * Creates a DynamicObjectArray in which each chunk has 2**chunkBits elements
+   * and initChunks chunks are initially allocated.
+   */
+  public DynamicObjectArray (int chunkBits, int initChunks) {
+    this(Growth.defaultGrowth, chunkBits, initChunks);
+  }
+
+  public DynamicObjectArray (Growth strategy, int chunkBits, int initChunks) {
+    if (chunkBits > 20) throw new IllegalArgumentException();
+    this.chunkBits = chunkBits;
+    nPerChunk = 1<<chunkBits;
+    this.chunkMask = nPerChunk - 1;
+    data = new Object[initChunks][];
+    growth = strategy;
+  }
+
+  @Override
+  public Iterator<E> iterator() {
+    return new DynIterator();
+  }
+
+  @SuppressWarnings("unchecked")
+  public E get (int index) {
+    int i = index >> chunkBits;
+    if (i < data.length && data[i] != null) {
+      int j = index & chunkMask;
+      return (E) data[i][j];
+    } else {
+      return null;
+    }
+  }
+
+  // this is only the max size, not the max index that was accessed/set
+  public int size() {
+    return data.length * nPerChunk;
+  }
+
+  public int getMaxIndex() {
+    return maxIndex;
+  }
+
+  public void set (int index, E value) {
+    if (index > maxIndex) {
+      maxIndex = index;
+    }
+
+    int i = index >> chunkBits;
+    int j = index & chunkMask;
+
+    if (i >= data.length) {
+      int nChunks = growth.grow(data.length, i+1);
+      Object[][] newChunks = new Object[nChunks][];
+      System.arraycopy(data, 0, newChunks, 0, data.length);
+      data = newChunks;
+    }
+    if (data[i] == null) {
+      data[i] = new Object[1 << chunkBits];
+    }
+
+    data[i][j] = value;
+  }
+
+  @Override
+  public String toString() {
+    int length = data.length * (1 << chunkBits);
+    while (length > 1 && get(length-1) == null) length--;
+
+    StringBuilder sb = new StringBuilder(length);
+
+    sb.append('{');
+    int l = length-1;
+    for (int i=0; i<l; i++) {
+      sb.append(get(i));
+      sb.append(',');
+    }
+    sb.append(get(l));
+    sb.append('}');
+
+    return sb.toString();
+  }
+
+  // removed toArray method, which is confusing for 1.5
+}