1 /* 2 * Copyright (C) 2022 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.server.nearby.common.bloomfilter; 18 19 import com.google.common.hash.Hashing; 20 21 import java.nio.ByteBuffer; 22 23 /** 24 * Hasher which hashes a value using SHA-256 and splits it into parts, each of which can be 25 * converted to an index. 26 */ 27 public class FastPairBloomFilterHasher implements BloomFilter.Hasher { 28 29 private static final int NUM_INDEXES = 8; 30 31 @Override getHashes(byte[] value)32 public int[] getHashes(byte[] value) { 33 byte[] hash = Hashing.sha256().hashBytes(value).asBytes(); 34 ByteBuffer buffer = ByteBuffer.wrap(hash); 35 int[] hashes = new int[NUM_INDEXES]; 36 for (int i = 0; i < NUM_INDEXES; i++) { 37 hashes[i] = buffer.getInt(); 38 } 39 return hashes; 40 } 41 } 42