COMMAND git -C /tmp/java-baseline-guava-3350 rev-parse HEAD
8868c096cfdabbe38170b6e395369c315cfb72a1

READ /tmp/java-baseline-guava-3350/guava/src/com/google/common/hash/BloomFilter.java
/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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.google.common.hash;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static java.lang.Byte.toUnsignedInt;
import static java.lang.Math.max;

import com.google.common.annotations.Beta;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Predicate;
import com.google.common.hash.BloomFilterStrategies.LockFreeBitArray;
import com.google.common.math.DoubleMath;
import com.google.common.primitives.SignedBytes;
import com.google.common.primitives.UnsignedBytes;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.InlineMe;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.math.RoundingMode;
import java.util.Objects;
import java.util.stream.Collector;
import org.jspecify.annotations.Nullable;

/**
 * A Bloom filter for instances of {@code T}. A Bloom filter offers an approximate containment test
 * with one-sided error: if it claims that an element is contained in it, this might be in error,
 * but if it claims that an element is <i>not</i> contained in it, then this is definitely true.
 *
 * <p>If you are unfamiliar with Bloom filters, this nice <a
 * href="http://llimllib.github.io/bloomfilter-tutorial/">tutorial</a> may help you understand how
 * they work.
 *
 * <p>The false positive probability ({@code FPP}) of a Bloom filter is defined as the probability
 * that {@linkplain #mightContain(Object)} will erroneously return {@code true} for an object that
 * has not actually been put in the {@code BloomFilter}.
 *
 * <p>Bloom filters are serializable. They also support a more compact serial representation via the
 * {@link #writeTo} and {@link #readFrom} methods. Both serialized forms will continue to be
 * supported by future versions of this library. However, serial forms generated by newer versions
 * of the code may not be readable by older versions of the code (e.g., a serialized Bloom filter
 * generated today may <i>not</i> be readable by a binary that was compiled 6 months ago).
 *
 * <p>As of Guava 23.0, this class is thread-safe and lock-free. It internally uses atomics and
 * compare-and-swap to ensure correctness when multiple threads are used to access it.
 *
 * @param <T> the type of instances that the {@code BloomFilter} accepts
 * @author Dimitris Andreou
 * @author Kevin Bourrillion
 * @since 11.0 (thread-safe since 23.0)
 */
@Beta
public final class BloomFilter<T extends @Nullable Object> implements Predicate<T>, Serializable {
  /**
   * A strategy to translate T instances, to {@code numHashFunctions} bit indexes.
   *
   * <p>Implementations should be collections of pure functions (i.e. stateless).
   */
  interface Strategy extends java.io.Serializable {

    /**
     * Sets {@code numHashFunctions} bits of the given bit array, by hashing a user element.
     *
     * <p>Returns whether any bits changed as a result of this operation.
     */
    <T extends @Nullable Object> boolean put(
        @ParametricNullness T object,
        Funnel<? super T> funnel,
        int numHashFunctions,
        LockFreeBitArray bits);

    /**
     * Queries {@code numHashFunctions} bits of the given bit array, by hashing a user element;
     * returns {@code true} if and only if all selected bits are set.
     */
    <T extends @Nullable Object> boolean mightContain(
        @ParametricNullness T object,
        Funnel<? super T> funnel,
        int numHashFunctions,
        LockFreeBitArray bits);

    /**
     * Identifier used to encode this strategy, when marshalled as part of a BloomFilter. Only
     * values in the [-128, 127] range are valid for the compact serial form. Non-negative values
     * are reserved for enums defined in BloomFilterStrategies; negative values are reserved for any
     * custom, stateful strategy we may define (e.g. any kind of strategy that would depend on user
     * input).
     */
    int ordinal();
  }

  /** The bit set of the BloomFilter (not necessarily power of 2!) */
  private final LockFreeBitArray bits;

  /** Number of hashes per element */
  private final int numHashFunctions;

  /** The funnel to translate Ts to bytes */
  private final Funnel<? super T> funnel;

  /** The strategy we employ to map an element T to {@code numHashFunctions} bit indexes. */
  private final Strategy strategy;

  /** Natural logarithm of 2, used to optimize calculations in Bloom filter sizing. */
  private static final double LOG_TWO = Math.log(2);

  /** Square of the natural logarithm of 2, reused to optimize the bit size calculation. */
  private static final double SQUARED_LOG_TWO = LOG_TWO * LOG_TWO;

  /** Creates a BloomFilter. */
  private BloomFilter(
      LockFreeBitArray bits, int numHashFunctions, Funnel<? super T> funnel, Strategy strategy) {
    checkArgument(numHashFunctions > 0, "numHashFunctions (%s) must be > 0", numHashFunctions);
    checkArgument(
        numHashFunctions <= 255, "numHashFunctions (%s) must be <= 255", numHashFunctions);
    this.bits = checkNotNull(bits);
    this.numHashFunctions = numHashFunctions;
    this.funnel = checkNotNull(funnel);
    this.strategy = checkNotNull(strategy);
  }

  /**
   * Creates a new {@code BloomFilter} that's a copy of this instance. The new instance is equal to
   * this instance but shares no mutable state.
   *
   * @since 12.0
   */
  public BloomFilter<T> copy() {
    return new BloomFilter<>(bits.copy(), numHashFunctions, funnel, strategy);
  }

  /**
   * Returns {@code true} if the element <i>might</i> have been put in this Bloom filter, {@code
   * false} if this is <i>definitely</i> not the case.
   */
  public boolean mightContain(@ParametricNullness T object) {
    return strategy.mightContain(object, funnel, numHashFunctions, bits);
  }

  /**
   * @deprecated Provided only to satisfy the {@link Predicate} interface; use {@link #mightContain}
   *     instead.
   */
  @InlineMe(replacement = "this.mightContain(input)")
  @Deprecated
  @Override
  public boolean apply(@ParametricNullness T input) {
    return mightContain(input);
  }

  /**
   * @deprecated Provided only to satisfy the {@link java.util.function.Predicate} interface; use
   *     {@link #mightContain} instead.
   * @since 21.0
   */
  @InlineMe(replacement = "this.mightContain(input)")
  @Deprecated
  @Override
  public boolean test(@ParametricNullness T input) {
    return mightContain(input);
  }

  /**
   * Puts an element into this {@code BloomFilter}. Ensures that subsequent invocations of {@link
   * #mightContain(Object)} with the same element will always return {@code true}.
   *
   * @return true if the Bloom filter's bits changed as a result of this operation. If the bits
   *     changed, this is <i>definitely</i> the first time {@code object} has been added to the
   *     filter. If the bits haven't changed, this <i>might</i> be the first time {@code object} has
   *     been added to the filter. Note that {@code put(t)} always returns the <i>opposite</i>
   *     result to what {@code mightContain(t)} would have returned at the time it is called.
   * @since 12.0 (present in 11.0 with {@code void} return type})
   */
  @CanIgnoreReturnValue
  public boolean put(@ParametricNullness T object) {
    return strategy.put(object, funnel, numHashFunctions, bits);
  }

  /**
   * Returns the probability that {@linkplain #mightContain(Object)} will erroneously return {@code
   * true} for an object that has not actually been put in the {@code BloomFilter}.
   *
   * <p>Ideally, this number should be close to the {@code fpp} parameter passed in {@linkplain
   * #create(Funnel, int, double)}, or smaller. If it is significantly higher, it is usually the
   * case that too many elements (more than expected) have been put in the {@code BloomFilter},
   * degenerating it.
   *
   * @since 14.0 (since 11.0 as expectedFalsePositiveProbability())
   */
  public double expectedFpp() {
    return Math.pow((double) bits.bitCount() / bitSize(), numHashFunctions);
  }

  /**
   * Returns an estimate for the total number of distinct elements that have been added to this
   * Bloom filter. This approximation is reasonably accurate if it does not exceed the value of
   * {@code expectedInsertions} that was used when constructing the filter.
   *
   * @since 22.0
   */
  public long approximateElementCount() {
    long bitSize = bits.bitSize();
    long bitCount = bits.bitCount();

    /*
     * Each insertion is expected to reduce the # of clear bits by a factor of
     * `numHashFunctions/bitSize`. So, after n insertions, expected bitCount is `bitSize * (1 - (1 -
     * numHashFunctions/bitSize)^n)`. Solving that for n, and approximating `ln x` as `x - 1` when x
     * is close to 1 (why?), gives the following formula.
     */
    double fractionOfBitsSet = (double) bitCount / bitSize;
    return DoubleMath.roundToLong(
        -Math.log1p(-fractionOfBitsSet) * bitSize / numHashFunctions, RoundingMode.HALF_UP);
  }

  /** Returns the number of bits in the underlying bit array. */
  @VisibleForTesting
  long bitSize() {
    return bits.bitSize();
  }

  /**
   * Determines whether a given Bloom filter is compatible with this Bloom filter. For two Bloom
   * filters to be compatible, they must:
   *
   * <ul>
   *   <li>not be the same instance
   *   <li>have the same number of hash functions
   *   <li>have the same bit size
   *   <li>have the same strategy
   *   <li>have equal funnels
   * </ul>
   *
   * @param that The Bloom filter to check for compatibility.
   * @since 15.0
   */
  public boolean isCompatible(BloomFilter<T> that) {
    checkNotNull(that);
    return this != that
        && this.numHashFunctions == that.numHashFunctions
        && this.bitSize() == that.bitSize()
        && this.strategy.equals(that.strategy)
        && this.funnel.equals(that.funnel);
  }

  /**
   * Combines this Bloom filter with another Bloom filter by performing a bitwise OR of the
   * underlying data. The mutations happen to <b>this</b> instance. Callers must ensure the Bloom
   * filters are appropriately sized to avoid saturating them.
   *
   * @param that The Bloom filter to combine this Bloom filter with. It is not mutated.
   * @throws IllegalArgumentException if {@code isCompatible(that) == false}
   * @since 15.0
   */
  public void putAll(BloomFilter<T> that) {
    checkNotNull(that);
    checkArgument(this != that, "Cannot combine a BloomFilter with itself.");
    checkArgument(
        this.numHashFunctions == that.numHashFunctions,
        "BloomFilters must have the same number of hash functions (%s != %s)",
        this.numHashFunctions,
        that.numHashFunctions);
    checkArgument(
        this.bitSize() == that.bitSize(),
        "BloomFilters must have the same size underlying bit arrays (%s != %s)",
        this.bitSize(),
        that.bitSize());
    checkArgument(
        this.strategy.equals(that.strategy),
        "BloomFilters must have equal strategies (%s != %s)",
        this.strategy,
        that.strategy);
    checkArgument(
        this.funnel.equals(that.funnel),
        "BloomFilters must have equal funnels (%s != %s)",
        this.funnel,
        that.funnel);
    this.bits.putAll(that.bits);
  }

  @Override
  public boolean equals(@Nullable Object object) {
    if (object == this) {
      return true;
    }
    if (object instanceof BloomFilter) {
      BloomFilter<?> that = (BloomFilter<?>) object;
      return this.numHashFunctions == that.numHashFunctions
          && this.funnel.equals(that.funnel)
          && this.bits.equals(that.bits)
          && this.strategy.equals(that.strategy);
    }
    return false;
  }

  @Override
  public int hashCode() {
    return Objects.hash(numHashFunctions, funnel, strategy, bits);
  }

  /**
   * Returns a {@code Collector} expecting the specified number of insertions, and yielding a {@link
   * BloomFilter} with false positive probability 3%.
   *
   * <p>Note that if the {@code Collector} receives significantly more elements than specified, the
   * resulting {@code BloomFilter} will suffer a sharp deterioration of its false positive
   * probability.
   *
   * <p>The constructed {@code BloomFilter} will be serializable if the provided {@code Funnel<T>}
   * is.
   *
   * <p>It is recommended that the funnel be implemented as a Java enum. This has the benefit of
   * ensuring proper serialization and deserialization, which is important since {@link #equals}
   * also relies on object identity of funnels.
   *
   * @param funnel the funnel of T's that the constructed {@code BloomFilter} will use
   * @param expectedInsertions the number of expected insertions to the constructed {@code
   *     BloomFilter}; must be positive
   * @return a {@code Collector} generating a {@code BloomFilter} of the received elements
   * @since 23.0 (but only since 33.4.0 in the Android flavor)
   */
  public static <T extends @Nullable Object> Collector<T, ?, BloomFilter<T>> toBloomFilter(
      Funnel<? super T> funnel, long expectedInsertions) {
    return toBloomFilter(funnel, expectedInsertions, 0.03);
  }

  /**
   * Returns a {@code Collector} expecting the specified number of insertions, and yielding a {@link
   * BloomFilter} with the specified expected false positive probability.
   *
   * <p>Note that if the {@code Collector} receives significantly more elements than specified, the
   * resulting {@code BloomFilter} will suffer a sharp deterioration of its false positive
   * probability.
   *
   * <p>The constructed {@code BloomFilter} will be serializable if the provided {@code Funnel<T>}
   * is.
   *
   * <p>It is recommended that the funnel be implemented as a Java enum. This has the benefit of
   * ensuring proper serialization and deserialization, which is important since {@link #equals}
   * also relies on object identity of funnels.
   *
   * @param funnel the funnel of T's that the constructed {@code BloomFilter} will use
   * @param expectedInsertions the number of expected insertions to the constructed {@code
   *     BloomFilter}; must be positive
   * @param fpp the desired false positive probability (must be positive and less than 1.0)
   * @return a {@code Collector} generating a {@code BloomFilter} of the received elements
   * @since 23.0 (but only since 33.4.0 in the Android flavor)
   */
  public static <T extends @Nullable Object> Collector<T, ?, BloomFilter<T>> toBloomFilter(
      Funnel<? super T> funnel, long expectedInsertions, double fpp) {
    checkNotNull(funnel);
    checkArgument(
        expectedInsertions >= 0, "Expected insertions (%s) must be >= 0", expectedInsertions);
    checkArgument(fpp > 0.0, "False positive probability (%s) must be > 0.0", fpp);
    checkArgument(fpp < 1.0, "False positive probability (%s) must be < 1.0", fpp);
    return Collector.of(
        () -> BloomFilter.create(funnel, expectedInsertions, fpp),
        BloomFilter::put,
        (bf1, bf2) -> {
          bf1.putAll(bf2);
          return bf1;
        },
        Collector.Characteristics.UNORDERED,
        Collector.Characteristics.CONCURRENT);
  }

  /**
   * Creates a {@link BloomFilter} with the expected number of insertions and expected false
   * positive probability.
   *
   * <p>Note that overflowing a {@code BloomFilter} with significantly more elements than specified,
   * will result in its saturation, and a sharp deterioration of its false positive probability.
   *
   * <p>The constructed {@code BloomFilter} will be serializable if the provided {@code Funnel<T>}
   * is.
   *
   * <p>It is recommended that the funnel be implemented as a Java enum. This has the benefit of
   * ensuring proper serialization and deserialization, which is important since {@link #equals}
   * also relies on object identity of funnels.
   *
   * @param funnel the funnel of T's that the constructed {@code BloomFilter} will use
   * @param expectedInsertions the number of expected insertions to the constructed {@code
   *     BloomFilter}; must be positive
   * @param fpp the desired false positive probability (must be positive and less than 1.0)
   * @return a {@code BloomFilter}
   */
  public static <T extends @Nullable Object> BloomFilter<T> create(
      Funnel<? super T> funnel, int expectedInsertions, double fpp) {
    return create(funnel, (long) expectedInsertions, fpp);
  }

  /**
   * Creates a {@link BloomFilter} with the expected number of insertions and expected false
   * positive probability.
   *
   * <p>Note that overflowing a {@code BloomFilter} with significantly more elements than specified,
   * will result in its saturation, and a sharp deterioration of its false positive probability.
   *
   * <p>The constructed {@code BloomFilter} will be serializable if the provided {@code Funnel<T>}
   * is.
   *
   * <p>It is recommended that the funnel be implemented as a Java enum. This has the benefit of
   * ensuring proper serialization and deserialization, which is important since {@link #equals}
   * also relies on object identity of funnels.
   *
   * @param funnel the funnel of T's that the constructed {@code BloomFilter} will use
   * @param expectedInsertions the number of expected insertions to the constructed {@code
   *     BloomFilter}; must be positive
   * @param fpp the desired false positive probability (must be positive and less than 1.0)
   * @return a {@code BloomFilter}
   * @since 19.0
   */
  public static <T extends @Nullable Object> BloomFilter<T> create(
      Funnel<? super T> funnel, long expectedInsertions, double fpp) {
    return create(funnel, expectedInsertions, fpp, BloomFilterStrategies.MURMUR128_MITZ_64);
  }

  @VisibleForTesting
  static <T extends @Nullable Object> BloomFilter<T> create(
      Funnel<? super T> funnel, long expectedInsertions, double fpp, Strategy strategy) {
    checkNotNull(funnel);
    checkArgument(
        expectedInsertions >= 0, "Expected insertions (%s) must be >= 0", expectedInsertions);
    checkArgument(fpp > 0.0, "False positive probability (%s) must be > 0.0", fpp);
    checkArgument(fpp < 1.0, "False positive probability (%s) must be < 1.0", fpp);
    checkNotNull(strategy);

    if (expectedInsertions == 0) {
      expectedInsertions = 1;
    }
    /*
     * TODO(user): Put a warning in the javadoc about tiny fpp values, since the resulting size
     * is proportional to -log(p), but there is not much of a point after all, e.g.
     * optimalM(1000, 0.0000000000000001) = 76680 which is less than 10kb. Who cares!
     */
    long numBits = optimalNumOfBits(expectedInsertions, fpp);
    int numHashFunctions = optimalNumOfHashFunctions(fpp);
    try {
      return new BloomFilter<>(new LockFreeBitArray(numBits), numHashFunctions, funnel, strategy);
    } catch (IllegalArgumentException e) {
      throw new IllegalArgumentException("Could not create BloomFilter of " + numBits + " bits", e);
    }
  }

  /**
   * Creates a {@link BloomFilter} with the expected number of insertions and a default expected
   * false positive probability of 3%.
   *
   * <p>Note that overflowing a {@code BloomFilter} with significantly more elements than specified,
   * will result in its saturation, and a sharp deterioration of its false positive probability.
   *
   * <p>The constructed {@code BloomFilter} will be serializable if the provided {@code Funnel<T>}
   * is.
   *
   * <p>It is recommended that the funnel be implemented as a Java enum. This has the benefit of
   * ensuring proper serialization and deserialization, which is important since {@link #equals}
   * also relies on object identity of funnels.
   *
   * @param funnel the funnel of T's that the constructed {@code BloomFilter} will use
   * @param expectedInsertions the number of expected insertions to the constructed {@code
   *     BloomFilter}; must be positive
   * @return a {@code BloomFilter}
   */
  public static <T extends @Nullable Object> BloomFilter<T> create(
      Funnel<? super T> funnel, int expectedInsertions) {
    return create(funnel, (long) expectedInsertions);
  }

  /**
   * Creates a {@link BloomFilter} with the expected number of insertions and a default expected
   * false positive probability of 3%.
   *
   * <p>Note that overflowing a {@code BloomFilter} with significantly more elements than specified,
   * will result in its saturation, and a sharp deterioration of its false positive probability.
   *
   * <p>The constructed {@code BloomFilter} will be serializable if the provided {@code Funnel<T>}
   * is.
   *
   * <p>It is recommended that the funnel be implemented as a Java enum. This has the benefit of
   * ensuring proper serialization and deserialization, which is important since {@link #equals}
   * also relies on object identity of funnels.
   *
   * @param funnel the funnel of T's that the constructed {@code BloomFilter} will use
   * @param expectedInsertions the number of expected insertions to the constructed {@code
   *     BloomFilter}; must be positive
   * @return a {@code BloomFilter}
   * @since 19.0
   */
  public static <T extends @Nullable Object> BloomFilter<T> create(
      Funnel<? super T> funnel, long expectedInsertions) {
    return create(funnel, expectedInsertions, 0.03); // FYI, for 3%, we always get 5 hash functions
  }

  // Cheat sheet:
  //
  // m: total bits
  // n: expected insertions
  // b: m/n, bits per insertion
  // p: expected false positive probability
  //
  // 1) Optimal k = b * ln2
  // 2) p = (1 - e ^ (-kn/m))^k
  // 3) For optimal k: p = 2 ^ (-k) ~= 0.6185^b
  // 4) For optimal k: m = -nlnp / ((ln2) ^ 2)

  /**
   * Computes the optimal number of hash functions (k) for a given false positive probability (p).
   *
   * <p>See http://en.wikipedia.org/wiki/File:Bloom_filter_fp_probability.svg for the formula.
   *
   * @param p desired false positive probability (must be between 0 and 1, exclusive)
   */
  @VisibleForTesting
  static int optimalNumOfHashFunctions(double p) {
    // -log(p) / log(2), ensuring the result is rounded to avoid truncation.
    return max(1, (int) Math.round(-Math.log(p) / LOG_TWO));
  }

  /**
   * Computes m (total bits of Bloom filter) which is expected to achieve, for the specified
   * expected insertions, the required false positive probability.
   *
   * <p>See http://en.wikipedia.org/wiki/Bloom_filter#Probability_of_false_positives for the
   * formula.
   *
   * @param n expected insertions (must be positive)
   * @param p false positive rate (must be 0 < p < 1)
   */
  @VisibleForTesting
  static long optimalNumOfBits(long n, double p) {
    if (p == 0) {
      p = Double.MIN_VALUE;
    }
    return (long) (-n * Math.log(p) / SQUARED_LOG_TWO);
  }

    private Object writeReplace() {
    return new SerialForm<T>(this);
  }

    private void readObject(ObjectInputStream stream) throws InvalidObjectException {
    throw new InvalidObjectException("Use SerializedForm");
  }

  private static final class SerialForm<T extends @Nullable Object> implements Serializable {
    final long[] data;
    final int numHashFunctions;
    final Funnel<? super T> funnel;
    final Strategy strategy;

    SerialForm(BloomFilter<T> bf) {
      this.data = LockFreeBitArray.toPlainArray(bf.bits.data);
      this.numHashFunctions = bf.numHashFunctions;
      this.funnel = bf.funnel;
      this.strategy = bf.strategy;
    }

    Object readResolve() {
      return new BloomFilter<T>(new LockFreeBitArray(data), numHashFunctions, funnel, strategy);
    }

    private static final long serialVersionUID = 1;
  }

  /**
   * Writes this {@code BloomFilter} to an output stream, with a custom format (not Java
   * serialization). This has been measured to save at least 400 bytes compared to regular
   * serialization.
   *
   * <p>Use {@linkplain #readFrom(InputStream, Funnel)} to reconstruct the written BloomFilter.
   */
  public void writeTo(OutputStream out) throws IOException {
    // Serial form:
    // 1 signed byte for the strategy
    // 1 unsigned byte for the number of hash functions
    // 1 big endian int, the number of longs in our bitset
    // N big endian longs of our bitset
    DataOutputStream dout = new DataOutputStream(out);
    dout.writeByte(SignedBytes.checkedCast(strategy.ordinal()));
    dout.writeByte(UnsignedBytes.checkedCast(numHashFunctions)); // note: checked at the c'tor
    dout.writeInt(bits.data.length());
    for (int i = 0; i < bits.data.length(); i++) {
      dout.writeLong(bits.data.get(i));
    }
  }

  /**
   * Reads a byte stream, which was written by {@linkplain #writeTo(OutputStream)}, into a {@code
   * BloomFilter}.
   *
   * <p>The {@code Funnel} to be used is not encoded in the stream, so it must be provided here.
   * <b>Warning:</b> the funnel provided <b>must</b> behave identically to the one used to populate
   * the original Bloom filter!
   *
   * @throws IOException if the InputStream throws an {@code IOException}, or if its data does not
   *     appear to be a BloomFilter serialized using the {@linkplain #writeTo(OutputStream)} method.
   */
  @SuppressWarnings("CatchingUnchecked") // sneaky checked exception
  public static <T extends @Nullable Object> BloomFilter<T> readFrom(
      InputStream in, Funnel<? super T> funnel) throws IOException {
    checkNotNull(in, "InputStream");
    checkNotNull(funnel, "Funnel");
    int strategyOrdinal = -1;
    int numHashFunctions = -1;
    int dataLength = -1;
    try {
      DataInputStream din = new DataInputStream(in);
      // currently this assumes there is no negative ordinal; will have to be updated if we
      // add non-stateless strategies (for which we've reserved negative ordinals; see
      // Strategy.ordinal()).
      strategyOrdinal = din.readByte();
      numHashFunctions = toUnsignedInt(din.readByte());
      dataLength = din.readInt();

      /*
       * We document in BloomFilterStrategies that we must not change the ordering, and we have a
       * test that verifies that we don't do so.
       */
      @SuppressWarnings("EnumOrdinal")
      Strategy strategy = BloomFilterStrategies.values()[strategyOrdinal];

      LockFreeBitArray dataArray = new LockFreeBitArray(Math.multiplyExact(dataLength, 64L));
      for (int i = 0; i < dataLength; i++) {
        dataArray.putData(i, din.readLong());
      }

      return new BloomFilter<>(dataArray, numHashFunctions, funnel, strategy);
    } catch (IOException e) {
      throw e;
    } catch (Exception e) { // sneaky checked exception
      String message =
          "Unable to deserialize BloomFilter from InputStream."
              + " strategyOrdinal: "
              + strategyOrdinal
              + " numHashFunctions: "
              + numHashFunctions
              + " dataLength: "
              + dataLength;
      throw new IOException(message, e);
    }
  }

  private static final long serialVersionUID = 0xcafebabe;
}

READ /tmp/java-baseline-guava-3350/guava/src/com/google/common/hash/AbstractByteHasher.java
/*
 * Copyright (C) 2012 The Guava Authors
 *
 * 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.google.common.hash;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;

import com.google.common.primitives.Chars;
import com.google.common.primitives.Ints;
import com.google.common.primitives.Longs;
import com.google.common.primitives.Shorts;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import org.jspecify.annotations.Nullable;

/**
 * Abstract {@link Hasher} that handles converting primitives to bytes using a scratch {@code
 * ByteBuffer} and streams all bytes to a sink to compute the hash.
 *
 * @author Colin Decker
 */
abstract class AbstractByteHasher extends AbstractHasher {
  private @Nullable ByteBuffer scratch;

  /** Updates this hasher with the given byte. */
  protected abstract void update(byte b);

  /** Updates this hasher with the given bytes. */
  protected void update(byte[] b) {
    update(b, 0, b.length);
  }

  /** Updates this hasher with {@code len} bytes starting at {@code off} in the given buffer. */
  protected void update(byte[] b, int off, int len) {
    for (int i = off; i < off + len; i++) {
      update(b[i]);
    }
  }

  /** Updates this hasher with bytes from the given buffer. */
  protected void update(ByteBuffer b) {
    if (b.hasArray()) {
      update(b.array(), b.arrayOffset() + b.position(), b.remaining());
      Java8Compatibility.position(b, b.limit());
    } else {
      for (int remaining = b.remaining(); remaining > 0; remaining--) {
        update(b.get());
      }
    }
  }

  /** Updates the sink with the given number of bytes from the buffer. */
  @SuppressWarnings("ByteBufferBackingArray") // We created the array with ByteBuffer.allocate().
  @CanIgnoreReturnValue
  private Hasher update(ByteBuffer scratch, int bytes) {
    try {
      update(scratch.array(), 0, bytes);
    } finally {
      Java8Compatibility.clear(scratch);
    }
    return this;
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putByte(byte b) {
    update(b);
    return this;
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putBytes(byte[] bytes) {
    checkNotNull(bytes);
    update(bytes);
    return this;
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putBytes(byte[] bytes, int off, int len) {
    checkPositionIndexes(off, off + len, bytes.length);
    update(bytes, off, len);
    return this;
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putBytes(ByteBuffer bytes) {
    update(bytes);
    return this;
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putShort(short s) {
    ByteBuffer scratch = scratch();
    scratch.putShort(s);
    return update(scratch, Shorts.BYTES);
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putInt(int i) {
    ByteBuffer scratch = scratch();
    scratch.putInt(i);
    return update(scratch, Ints.BYTES);
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putLong(long l) {
    ByteBuffer scratch = scratch();
    scratch.putLong(l);
    return update(scratch, Longs.BYTES);
  }

  @Override
  @CanIgnoreReturnValue
  public Hasher putChar(char c) {
    ByteBuffer scratch = scratch();
    scratch.putChar(c);
    return update(scratch, Chars.BYTES);
  }

  private ByteBuffer scratch() {
    if (scratch == null) {
      scratch = ByteBuffer.allocate(8).order(ByteOrder.LITTLE_ENDIAN);
    }
    return scratch;
  }
}

READ /tmp/java-baseline-guava-3350/guava/src/com/google/common/hash/BloomFilterStrategies.java
/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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.google.common.hash;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.math.LongMath;
import com.google.common.primitives.Ints;
import com.google.common.primitives.Longs;
import java.math.RoundingMode;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicLongArray;
import java.util.concurrent.atomic.LongAdder;
import org.jspecify.annotations.Nullable;

/**
 * Collections of strategies of generating the k * log(M) bits required for an element to be mapped
 * to a BloomFilter of M bits and k hash functions. These strategies are part of the serialized form
 * of the Bloom filters that use them, thus they must be preserved as is (no updates allowed, only
 * introduction of new versions).
 *
 * <p>Important: the order of the constants cannot change, and they cannot be deleted - we depend on
 * their ordinal for BloomFilter serialization.
 *
 * @author Dimitris Andreou
 * @author Kurt Alfred Kluever
 */
enum BloomFilterStrategies implements BloomFilter.Strategy {
  /**
   * See "Less Hashing, Same Performance: Building a Better Bloom Filter" by Adam Kirsch and Michael
   * Mitzenmacher. The paper argues that this trick doesn't significantly deteriorate the
   * performance of a Bloom filter (yet only needs two 32bit hash functions).
   */
  MURMUR128_MITZ_32() {
    @Override
    public <T extends @Nullable Object> boolean put(
        @ParametricNullness T object,
        Funnel<? super T> funnel,
        int numHashFunctions,
        LockFreeBitArray bits) {
      long bitSize = bits.bitSize();
      long hash64 = Hashing.murmur3_128().hashObject(object, funnel).asLong();
      int hash1 = (int) hash64;
      int hash2 = (int) (hash64 >>> 32);

      boolean bitsChanged = false;
      for (int i = 1; i <= numHashFunctions; i++) {
        int combinedHash = hash1 + (i * hash2);
        // Flip all the bits if it's negative (guaranteed positive number)
        if (combinedHash < 0) {
          combinedHash = ~combinedHash;
        }
        bitsChanged |= bits.set(combinedHash % bitSize);
      }
      return bitsChanged;
    }

    @Override
    public <T extends @Nullable Object> boolean mightContain(
        @ParametricNullness T object,
        Funnel<? super T> funnel,
        int numHashFunctions,
        LockFreeBitArray bits) {
      long bitSize = bits.bitSize();
      long hash64 = Hashing.murmur3_128().hashObject(object, funnel).asLong();
      int hash1 = (int) hash64;
      int hash2 = (int) (hash64 >>> 32);

      for (int i = 1; i <= numHashFunctions; i++) {
        int combinedHash = hash1 + (i * hash2);
        // Flip all the bits if it's negative (guaranteed positive number)
        if (combinedHash < 0) {
          combinedHash = ~combinedHash;
        }
        if (!bits.get(combinedHash % bitSize)) {
          return false;
        }
      }
      return true;
    }
  },
  /**
   * This strategy uses all 128 bits of {@link Hashing#murmur3_128} when hashing. It looks different
   * from the implementation in MURMUR128_MITZ_32 because we're avoiding the multiplication in the
   * loop and doing a (much simpler) += hash2. We're also changing the index to a positive number by
   * AND'ing with Long.MAX_VALUE instead of flipping the bits.
   */
  MURMUR128_MITZ_64() {
    @Override
    public <T extends @Nullable Object> boolean put(
        @ParametricNullness T object,
        Funnel<? super T> funnel,
        int numHashFunctions,
        LockFreeBitArray bits) {
      long bitSize = bits.bitSize();
      byte[] bytes = Hashing.murmur3_128().hashObject(object, funnel).getBytesInternal();
      long hash1 = lowerEight(bytes);
      long hash2 = upperEight(bytes);

      boolean bitsChanged = false;
      long combinedHash = hash1;
      for (int i = 0; i < numHashFunctions; i++) {
        // Make the combined hash positive and indexable
        bitsChanged |= bits.set((combinedHash & Long.MAX_VALUE) % bitSize);
        combinedHash += hash2;
      }
      return bitsChanged;
    }

    @Override
    public <T extends @Nullable Object> boolean mightContain(
        @ParametricNullness T object,
        Funnel<? super T> funnel,
        int numHashFunctions,
        LockFreeBitArray bits) {
      long bitSize = bits.bitSize();
      byte[] bytes = Hashing.murmur3_128().hashObject(object, funnel).getBytesInternal();
      long hash1 = lowerEight(bytes);
      long hash2 = upperEight(bytes);

      long combinedHash = hash1;
      for (int i = 0; i < numHashFunctions; i++) {
        // Make the combined hash positive and indexable
        if (!bits.get((combinedHash & Long.MAX_VALUE) % bitSize)) {
          return false;
        }
        combinedHash += hash2;
      }
      return true;
    }

    private /* static */ long lowerEight(byte[] bytes) {
      return Longs.fromBytes(
          bytes[7], bytes[6], bytes[5], bytes[4], bytes[3], bytes[2], bytes[1], bytes[0]);
    }

    private /* static */ long upperEight(byte[] bytes) {
      return Longs.fromBytes(
          bytes[15], bytes[14], bytes[13], bytes[12], bytes[11], bytes[10], bytes[9], bytes[8]);
    }
  };

  /**
   * Models a lock-free array of bits.
   *
   * <p>We use this instead of java.util.BitSet because we need access to the array of longs and we
   * need compare-and-swap.
   */
  static final class LockFreeBitArray {
    private static final int LONG_ADDRESSABLE_BITS = 6;
    final AtomicLongArray data;
    private final LongAdder bitCount;

    LockFreeBitArray(long bits) {
      checkArgument(bits > 0, "data length is zero!");
      // Avoid delegating to this(long[]), since AtomicLongArray(long[]) will clone its input and
      // thus double memory usage.
      this.data =
          new AtomicLongArray(Ints.checkedCast(LongMath.divide(bits, 64, RoundingMode.CEILING)));
      this.bitCount = new LongAdder();
    }

    // Used by serialization
    LockFreeBitArray(long[] data) {
      checkArgument(data.length > 0, "data length is zero!");
      this.data = new AtomicLongArray(data);
      this.bitCount = new LongAdder();
      long bitCount = 0;
      for (long value : data) {
        bitCount += Long.bitCount(value);
      }
      this.bitCount.add(bitCount);
    }

    /** Returns true if the bit changed value. */
    boolean set(long bitIndex) {
      if (get(bitIndex)) {
        return false;
      }

      int longIndex = (int) (bitIndex >>> LONG_ADDRESSABLE_BITS);
      long mask = 1L << bitIndex; // only cares about low 6 bits of bitIndex

      long oldValue;
      long newValue;
      do {
        oldValue = data.get(longIndex);
        newValue = oldValue | mask;
        if (oldValue == newValue) {
          return false;
        }
      } while (!data.compareAndSet(longIndex, oldValue, newValue));

      // We turned the bit on, so increment bitCount.
      bitCount.increment();
      return true;
    }

    boolean get(long bitIndex) {
      return (data.get((int) (bitIndex >>> LONG_ADDRESSABLE_BITS)) & (1L << bitIndex)) != 0;
    }

    /**
     * Careful here: if threads are mutating the atomicLongArray while this method is executing, the
     * final long[] will be a "rolling snapshot" of the state of the bit array. This is usually good
     * enough, but should be kept in mind.
     */
    public static long[] toPlainArray(AtomicLongArray atomicLongArray) {
      long[] array = new long[atomicLongArray.length()];
      for (int i = 0; i < array.length; ++i) {
        array[i] = atomicLongArray.get(i);
      }
      return array;
    }

    /** Number of bits */
    long bitSize() {
      return (long) data.length() * Long.SIZE;
    }

    /**
     * Number of set bits (1s).
     *
     * <p>Note that because of concurrent set calls and uses of atomics, this bitCount is a (very)
     * close *estimate* of the actual number of bits set. It's not possible to do better than an
     * estimate without locking. Note that the number, if not exactly accurate, is *always*
     * underestimating, never overestimating.
     */
    long bitCount() {
      return bitCount.sum();
    }

    LockFreeBitArray copy() {
      return new LockFreeBitArray(toPlainArray(data));
    }

    /**
     * Combines the two BitArrays using bitwise OR.
     *
     * <p>NOTE: Because of the use of atomics, if the other LockFreeBitArray is being mutated while
     * this operation is executing, not all of those new 1's may be set in the final state of this
     * LockFreeBitArray. The ONLY guarantee provided is that all the bits that were set in the other
     * LockFreeBitArray at the start of this method will be set in this LockFreeBitArray at the end
     * of this method.
     */
    void putAll(LockFreeBitArray other) {
      checkArgument(
          data.length() == other.data.length(),
          "BitArrays must be of equal length (%s != %s)",
          data.length(),
          other.data.length());
      for (int i = 0; i < data.length(); i++) {
        putData(i, other.data.get(i));
      }
    }

    /**
     * ORs the bits encoded in the {@code i}th {@code long} in the underlying {@link
     * AtomicLongArray} with the given value.
     */
    void putData(int i, long longValue) {
      long ourLongOld;
      long ourLongNew;
      boolean changedAnyBits = true;
      do {
        ourLongOld = data.get(i);
        ourLongNew = ourLongOld | longValue;
        if (ourLongOld == ourLongNew) {
          changedAnyBits = false;
          break;
        }
      } while (!data.compareAndSet(i, ourLongOld, ourLongNew));

      if (changedAnyBits) {
        int bitsAdded = Long.bitCount(ourLongNew) - Long.bitCount(ourLongOld);
        bitCount.add(bitsAdded);
      }
    }

    /** Returns the number of {@code long}s in the underlying {@link AtomicLongArray}. */
    int dataLength() {
      return data.length();
    }

    @Override
    public boolean equals(@Nullable Object o) {
      if (o instanceof LockFreeBitArray) {
        LockFreeBitArray lockFreeBitArray = (LockFreeBitArray) o;
        // TODO(lowasser): avoid allocation here
        return Arrays.equals(toPlainArray(data), toPlainArray(lockFreeBitArray.data));
      }
      return false;
    }

    @Override
    public int hashCode() {
      // TODO(lowasser): avoid allocation here
      return Arrays.hashCode(toPlainArray(data));
    }
  }
}
