1 /*
2  * Copyright 2018 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.view.inspector;
18 
19 import android.annotation.NonNull;
20 
21 import java.util.ArrayList;
22 import java.util.Collections;
23 import java.util.HashSet;
24 import java.util.List;
25 import java.util.Objects;
26 import java.util.Set;
27 
28 /**
29  * Maps the values of an {@code int} property to sets of string for properties that encode flags.
30  *
31  * An {@link InspectionCompanion} may provide an instance of this class to a {@link PropertyMapper}
32  * for flag values packed into primitive {@code int} properties.
33  *
34  * Each flag has a mask and a target value, for non-exclusive flags, the target can also be used as
35  * the mask. A given integer value is compared against each flag to find what flags are active for
36  * it by bitwise anding it with the mask and comparing the result against the target, that is,
37  * {@code (value & mask) == target}.
38  *
39  * @see PropertyMapper#mapIntFlag(String, int, java.util.function.IntFunction)
40  */
41 public final class IntFlagMapping {
42     private final List<Flag> mFlags = new ArrayList<>();
43 
44     /**
45      * Get a set of the names of enabled flags for a given property value.
46      *
47      * @param value The value of the property
48      * @return The names of the enabled flags, empty if no flags enabled
49      */
50     @NonNull
get(int value)51     public Set<String> get(int value) {
52         final Set<String> enabledFlagNames = new HashSet<>(mFlags.size());
53 
54         for (Flag flag : mFlags) {
55             if (flag.isEnabledFor(value)) {
56                 enabledFlagNames.add(flag.mName);
57             }
58         }
59 
60         return Collections.unmodifiableSet(enabledFlagNames);
61     }
62 
63     /**
64      * Add a mutually exclusive flag to the map.
65      *
66      * @param mask The bit mask to compare to and with a value
67      * @param target The target value to compare the masked value with
68      * @param name The name of the flag to include if enabled
69      */
add(int mask, int target, @NonNull String name)70     public void add(int mask, int target, @NonNull String name) {
71         mFlags.add(new Flag(mask, target, name));
72     }
73 
74     /**
75      * Inner class that holds the name, mask, and target value of a flag
76      */
77     private static final class Flag {
78         @NonNull private final String mName;
79         private final int mTarget;
80         private final int mMask;
81 
Flag(int mask, int target, @NonNull String name)82         private Flag(int mask, int target, @NonNull String name) {
83             mTarget = target;
84             mMask = mask;
85             mName = Objects.requireNonNull(name);
86         }
87 
88         /**
89          * Compare the supplied property value against the mask and target.
90          *
91          * @param value The value to check
92          * @return True if this flag is enabled
93          */
isEnabledFor(int value)94         private boolean isEnabledFor(int value) {
95             return (value & mMask) == mTarget;
96         }
97     }
98 }
99