1 /*
2  * Copyright (C) 2019 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.wifi.util;
18 
19 import android.util.ArrayMap;
20 
21 import java.lang.reflect.Array;
22 import java.util.Iterator;
23 import java.util.Map;
24 
25 /**
26  * Counts occurrences of keys of type K, where K is a custom key class. This is most commonly used
27  * for counting occurrences of composite keys.
28  * @param <K> Custom key type K must override {@link Object#hashCode()},
29  * {@link Object#equals(Object)}, and {@link Object#toString()}. These methods can be auto-generated
30  *           by IntelliJ by right clicking inside your class and clicking "Generate...".
31  */
32 public class ObjectCounter<K> implements Iterable<Map.Entry<K, Integer>> {
33     private ArrayMap<K, Integer> mCounter;
34 
ObjectCounter()35     public ObjectCounter() {
36         mCounter = new ArrayMap<>();
37     }
38 
39     /**
40      * Removes all keys and counts from this counter.
41      */
clear()42     public void clear() {
43         mCounter.clear();
44     }
45 
46     /**
47      * Returns the number of keys in this counter.
48      */
size()49     public int size() {
50         return mCounter.size();
51     }
52 
53     /**
54      * Gets the number of occurrences of a key
55      */
getCount(K key)56     public int getCount(K key) {
57         return mCounter.getOrDefault(key, 0);
58     }
59 
60     /**
61      * Increments the count of a key by 1.
62      */
increment(K key)63     public void increment(K key) {
64         add(key, 1);
65     }
66 
67     /**
68      * Increments the count of a key by <code>count</code>.
69      */
add(K key, int count)70     public void add(K key, int count) {
71         int curCount = getCount(key);
72         mCounter.put(key, curCount + count);
73     }
74 
75     /**
76      * Returns a string representation of this counter object suitable for dump(). Note that the
77      * type K must have an overridden implementation of {@link Object#toString()}.
78      */
79     @Override
toString()80     public String toString() {
81         return mCounter.toString();
82     }
83 
84     /**
85      * Iterates over all (key, count) pairs.
86      */
87     @Override
iterator()88     public Iterator<Map.Entry<K, Integer>> iterator() {
89         return mCounter.entrySet().iterator();
90     }
91 
92     /**
93      * Converter function that converts a single (key, count) pair to a Protobuf object.
94      * @param <I> The type of the key.
95      * @param <O> The type of the Protobuf output.
96      */
97     public interface ProtobufConverter<I, O> {
98         /**
99          * Converter function that converts a single (key, count) pair to a Protobuf object.
100          * @param key the key that we are counting occurrences for
101          * @param count the number of occurrences for this key
102          * @return the Protobuf output
103          */
convert(I key, int count)104         O convert(I key, int count);
105     }
106 
107     /**
108      * Converts this object to a custom Protobuf representation.
109      * @param protoClass the class object for the Protobuf type.
110      * @param converter a conversion function.
111      * @param <T> the type of the Protobuf output.
112      * @return an array of Protobuf representation of buckets generated by the converter function.
113      */
toProto(Class<T> protoClass, ProtobufConverter<K, T> converter)114     public <T> T[] toProto(Class<T> protoClass, ProtobufConverter<K, T> converter) {
115         @SuppressWarnings("unchecked")
116         T[] output = (T[]) Array.newInstance(protoClass, size());
117         int i = 0;
118         for (Map.Entry<K, Integer> entry : this) {
119             output[i] = converter.convert(entry.getKey(), entry.getValue());
120             i++;
121         }
122         return output;
123     }
124 }
125