/**
* Reads a byte stream, which was written by {@linkplain #writeTo(OutputStream)}, into a {@code
* BloomFilter<T>}.
*
* <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.
*/
public static <T> BloomFilter<T> readFrom(InputStream in, Funnel<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 = UnsignedBytes.toInt(din.readByte());
dataLength = din.readInt();
Strategy strategy = BloomFilterStrategies.values()[strategyOrdinal];
long[] data = new long[dataLength];
for (int i = 0; i < data.length; i++) {
data[i] = din.readLong();
}
return new BloomFilter<T>(new BitArray(data), numHashFunctions, funnel, strategy);
} catch (RuntimeException e) {
IOException ioException =
new IOException(
"Unable to deserialize BloomFilter from InputStream."
+ " strategyOrdinal: "
+ strategyOrdinal
+ " numHashFunctions: "
+ numHashFunctions
+ " dataLength: "
+ dataLength);
ioException.initCause(e);
throw ioException;
}
}
/**
* This test will fail whenever someone updates/reorders the BloomFilterStrategies constants. Only
* appending a new constant is allowed.
*/
public void testBloomFilterStrategies() {
assertThat(BloomFilterStrategies.values()).hasLength(2);
assertEquals(BloomFilterStrategies.MURMUR128_MITZ_32, BloomFilterStrategies.values()[0]);
assertEquals(BloomFilterStrategies.MURMUR128_MITZ_64, BloomFilterStrategies.values()[1]);
}