flink-libraries/flink-table/src/main/java/org/apache/flink/table/runtime/functions/aggfunctions/cardinality/MurmurHash.java

/*
 * 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.flink.table.runtime.functions.aggfunctions.cardinality;

/**
 * This is a very fast, non-cryptographic hash suitable for general hash-based
 * lookup. See http://murmurhash.googlepages.com/ for more details.
 * <p/>
 */
public class MurmurHash {

	public static int hash(Object o) {
		if (o == null) {
			return 0;
		}
		if (o instanceof Long) {
			return hashLong((Long) o);
		}
		if (o instanceof Integer) {
			return hashLong((Integer) o);
		}
		if (o instanceof Double) {
			return hashLong(Double.doubleToRawLongBits((Double) o));
		}
		if (o instanceof Float) {
			return hashLong(Float.floatToRawIntBits((Float) o));
		}
		if (o instanceof String) {
			return hash(((String) o).getBytes());
		}
		if (o instanceof byte[]) {
			return hash((byte[]) o);
		}
		return hash(o.toString());
	}

	public static int hash(byte[] data) {
		return hash(data, data.length, -1);
	}

	public static int hash(byte[] data, int seed) {
		return hash(data, data.length, seed);
	}

	public static int hash(byte[] data, int length, int seed) {
		int m = 0x5bd1e995;
		int r = 24;

		int h = seed ^ length;

		int len4 = length >> 2;

		for (int i = 0; i < len4; i++) {
			int i4 = i << 2;
			int k = data[i4 + 3];
			k = k << 8;
			k = k | (data[i4 + 2] & 0xff);
			k = k << 8;
			k = k | (data[i4 + 1] & 0xff);
			k = k << 8;
			k = k | (data[i4 + 0] & 0xff);
			k *= m;
			k ^= k >>> r;
			k *= m;
			h *= m;
			h ^= k;
		}

		// avoid calculating modulo
		int lenM = len4 << 2;
		int left = length - lenM;

		if (left != 0) {
			if (left >= 3) {
				h ^= (int) data[length - 3] << 16;
			}
			if (left >= 2) {
				h ^= (int) data[length - 2] << 8;
			}
			if (left >= 1) {
				h ^= (int) data[length - 1];
			}

			h *= m;
		}

		h ^= h >>> 13;
		h *= m;
		h ^= h >>> 15;

		return h;
	}

	public static int hashLong(long data) {
		int m = 0x5bd1e995;
		int r = 24;

		int h = 0;

		int k = (int) data * m;
		k ^= k >>> r;
		h ^= k * m;

		k = (int) (data >> 32) * m;
		k ^= k >>> r;
		h *= m;
		h ^= k * m;

		h ^= h >>> 13;
		h *= m;
		h ^= h >>> 15;

		return h;
	}

	public static long hash64(Object o) {
		if (o == null) {
			return 0L;
		} else if (o instanceof String) {
			final byte[] bytes = ((String) o).getBytes();
			return hash64(bytes, bytes.length);
		} else if (o instanceof byte[]) {
			final byte[] bytes = (byte[]) o;
			return hash64(bytes, bytes.length);
		}
		return hash64(o.toString());
	}

	// 64 bit implementation copied from here:  https://github.com/tnm/murmurhash-java

	/**
	 * Generates 64 bit hash from byte array with default seed value.
	 *
	 * @param data   byte array to hash
	 * @param length length of the array to hash
	 * @return 64 bit hash of the given string
	 */
	public static long hash64(final byte[] data, int length) {
		return hash64(data, length, 0xe17a1465);
	}


	/**
	 * Generates 64 bit hash from byte array of the given length and seed.
	 *
	 * @param data   byte array to hash
	 * @param length length of the array to hash
	 * @param seed   initial seed value
	 * @return 64 bit hash of the given array
	 */
	public static long hash64(final byte[] data, int length, int seed) {
		final long m = 0xc6a4a7935bd1e995L;
		final int r = 47;

		long h = (seed & 0xffffffffL) ^ (length * m);

		int length8 = length / 8;

		for (int i = 0; i < length8; i++) {
			final int i8 = i * 8;
			long k = ((long) data[i8 + 0] & 0xff) + (((long) data[i8 + 1] & 0xff) << 8)
					+ (((long) data[i8 + 2] & 0xff) << 16) + (((long) data[i8 + 3] & 0xff) << 24)
					+ (((long) data[i8 + 4] & 0xff) << 32) + (((long) data[i8 + 5] & 0xff) << 40)
					+ (((long) data[i8 + 6] & 0xff) << 48) + (((long) data[i8 + 7] & 0xff) << 56);

			k *= m;
			k ^= k >>> r;
			k *= m;

			h ^= k;
			h *= m;
		}

		switch (length % 8) {
			case 7:
				h ^= (long) (data[(length & ~7) + 6] & 0xff) << 48;
				h ^= (long) (data[(length & ~7) + 5] & 0xff) << 40;
				h ^= (long) (data[(length & ~7) + 4] & 0xff) << 32;
				h ^= (long) (data[(length & ~7) + 3] & 0xff) << 24;
				h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
				h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
				h ^= (long) (data[length & ~7] & 0xff);
				h *= m;
				break;
			case 6:
				h ^= (long) (data[(length & ~7) + 5] & 0xff) << 40;
				h ^= (long) (data[(length & ~7) + 4] & 0xff) << 32;
				h ^= (long) (data[(length & ~7) + 3] & 0xff) << 24;
				h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
				h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
				h ^= (long) (data[length & ~7] & 0xff);
				h *= m;
				break;
			case 5:
				h ^= (long) (data[(length & ~7) + 4] & 0xff) << 32;
				h ^= (long) (data[(length & ~7) + 3] & 0xff) << 24;
				h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
				h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
				h ^= (long) (data[length & ~7] & 0xff);
				h *= m;
				break;
			case 4:
				h ^= (long) (data[(length & ~7) + 3] & 0xff) << 24;
				h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
				h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
				h ^= (long) (data[length & ~7] & 0xff);
				h *= m;
				break;
			case 3:
				h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
				h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
				h ^= (long) (data[length & ~7] & 0xff);
				h *= m;
				break;
			case 2:
				h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
				h ^= (long) (data[length & ~7] & 0xff);
				h *= m;
				break;
			case 1:
				h ^= (long) (data[length & ~7] & 0xff);
				h *= m;
				break;
			default:
		}

		h ^= h >>> r;
		h *= m;
		h ^= h >>> r;

		return h;
	}
}