[GitHub] [commons-collections] Claudenw commented on a diff in pull request #258: Simplify bloom filters

[GitBox <gi...@apache.org>]

Claudenw commented on code in PR #258:
URL: https://github.com/apache/commons-collections/pull/258#discussion_r895017495


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src/main/java/org/apache/commons/collections4/bloomfilter/SimpleBloomFilter.java:
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@@ -0,0 +1,245 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.commons.collections4.bloomfilter;
+
+import java.util.Arrays;
+import java.util.Objects;
+import java.util.function.IntPredicate;
+import java.util.function.LongPredicate;
+
+/**
+ * A bloom filter using an array of bit maps to track enabled bits. This is a standard
+ * implementation and should work well for most Bloom filters.
+ * @since 4.5
+ */
+public final class SimpleBloomFilter implements BloomFilter {
+
+    /**
+     * The array of bit map longs that defines this Bloom filter.  Will be null if the filter is empty.
+     */
+    private final long[] bitMap;
+
+    /**
+     * The Shape of this Bloom filter.
+     */
+    private final Shape shape;
+
+    /**
+     * The cardinality of this Bloom filter.
+     */
+    private int cardinality;
+
+    /**
+     * Creates an empty instance.
+     *
+     * @param shape The shape for the filter.
+     */
+    public SimpleBloomFilter(Shape shape) {
+        Objects.requireNonNull(shape, "shape");
+        this.shape = shape;
+        this.bitMap = new long[BitMap.numberOfBitMaps(shape.getNumberOfBits())];
+        this.cardinality = 0;
+    }
+
+    /**
+     * Creates an instance that is equivalent to {@code other}.
+     *
+     * @param other The bloom filter to copy.
+     */
+    public SimpleBloomFilter(BloomFilter other) {
+        Objects.requireNonNull(other, "other");
+        this.shape = other.getShape();
+        this.bitMap = new long[BitMap.numberOfBitMaps(shape.getNumberOfBits())];
+        this.cardinality = 0;
+        if (other.isSparse()) {
+            mergeInPlace((IndexProducer) other);
+        } else {
+            mergeInPlace((BitMapProducer) other);
+        }
+    }
+
+    /**
+     * Creates a populated instance.
+     * @param shape The shape for the filter.
+     * @param hasher the Hasher to initialize the filter with.
+     */
+    public SimpleBloomFilter(final Shape shape, Hasher hasher) {
+        this(shape);
+        Objects.requireNonNull(hasher, "hasher");
+        mergeInPlace(hasher);
+    }
+
+    /**
+     * Creates a populated instance.
+     * @param shape The shape for the filter.
+     * @param indices the IndexProducer to initialize the filter with.
+     * @throws IllegalArgumentException if producer sends illegal value.
+     */
+    public SimpleBloomFilter(final Shape shape, IndexProducer indices) {
+        this(shape);
+        Objects.requireNonNull(indices, "indices");
+        mergeInPlace(indices);
+    }
+
+    /**
+     * Creates a populated instance.
+     * @param shape The shape for the filter.
+     * @param bitMaps the BitMapProducer to initialize the filter with.
+     * @throws IllegalArgumentException if the producer returns too many or too few bit maps.
+     */
+    public SimpleBloomFilter(final Shape shape, BitMapProducer bitMaps) {
+        this(shape);
+        Objects.requireNonNull(bitMaps, "bitMaps");
+        mergeInPlace(bitMaps);
+    }
+
+    /**
+     * Copy constructor for {@code copy()} use.
+     * @param source
+     */
+    private SimpleBloomFilter(SimpleBloomFilter source) {
+        this.shape = source.shape;
+        this.bitMap = source.bitMap.clone();
+        this.cardinality = source.cardinality;
+    }
+
+    @Override
+    public long[] asBitMapArray() {
+        return Arrays.copyOf(bitMap, bitMap.length);
+    }
+
+    @Override
+    public boolean forEachBitMapPair(BitMapProducer other, LongBiPredicate func) {
+        CountingLongPredicate p = new CountingLongPredicate(bitMap, func);
+        return other.forEachBitMap(p) && p.forEachRemaining();
+    }
+
+    @Override
+    public SimpleBloomFilter copy() {
+        return new SimpleBloomFilter(this);
+    }
+
+    /**
+     * Performs a merge in place using an IndexProducer.
+     * @param indexProducer the IndexProducer to merge from.
+     * @throws IllegalArgumentException if producer sends illegal value.
+     */
+    private void mergeInPlace(IndexProducer indexProducer) {
+        indexProducer.forEachIndex(idx -> {
+            if (idx < 0 || idx >= shape.getNumberOfBits()) {
+                throw new IllegalArgumentException(String.format(
+                        "IndexProducer should only send values in the range[0,%s]", shape.getNumberOfBits() - 1));
+            }
+            BitMap.set(bitMap, idx);
+            return true;
+        });
+        cardinality = -1;
+    }
+
+    /**
+     * Performs a merge in place using an BitMapProducer.
+     * @param bitMapProducer the BitMapProducer to merge from.
+     * @throws IllegalArgumentException if producer sends illegal value.
+     */
+    private void mergeInPlace(BitMapProducer bitMapProducer) {
+        try {
+            int[] idx = new int[1];
+            bitMapProducer.forEachBitMap(value -> {
+                bitMap[idx[0]++] |= value;
+                return true;
+            });
+            // idx[0] will be limit+1 so decrement it
+            idx[0]--;
+            int idxLimit = BitMap.getLongIndex(shape.getNumberOfBits());
+            if (idxLimit < idx[0]) {

Review Comment:
   Opened https://issues.apache.org/jira/browse/COLLECTIONS-816 to address this



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