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 android.host.systemui;
18 
19 import java.util.Objects;
20 
21 /**
22  * A simple hash function for use in privacy-sensitive logging.  Few bits = lots of collisions.
23  * See NotificationRecordLogger.
24  */
25 public class SmallHash {
26     // Hashes will be in the range [0, MAX_HASH).
27     public static final int MAX_HASH = (1 << 13);
28 
29     /**
30      * @return Small hash of the string, if non-null, or 0 otherwise.
31      */
hash(String in)32     public static int hash(String in) {
33         return hash(Objects.hashCode(in));
34     }
35 
36     /**
37      * Maps in to the range [0, MAX_HASH), keeping similar values distinct.
38      * @param in An arbitrary integer.
39      * @return in mod MAX_HASH, signs chosen to stay in the range [0, MAX_HASH).
40      */
hash(int in)41     public static int hash(int in) {
42         return Math.floorMod(in, MAX_HASH);
43     }
44 }
45