1/*
2 * Copyright (C) 2015 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
17package android.content.res;
18
19import android.annotation.NonNull;
20import android.annotation.Nullable;
21import android.content.pm.ActivityInfo.Config;
22import android.content.res.Resources.Theme;
23import android.content.res.Resources.ThemeKey;
24import android.util.LongSparseArray;
25import android.util.ArrayMap;
26
27import java.lang.ref.WeakReference;
28
29/**
30 * Data structure used for caching data against themes.
31 *
32 * @param <T> type of data to cache
33 */
34abstract class ThemedResourceCache<T> {
35    private ArrayMap<ThemeKey, LongSparseArray<WeakReference<T>>> mThemedEntries;
36    private LongSparseArray<WeakReference<T>> mUnthemedEntries;
37    private LongSparseArray<WeakReference<T>> mNullThemedEntries;
38
39    /**
40     * Adds a new theme-dependent entry to the cache.
41     *
42     * @param key a key that uniquely identifies the entry
43     * @param theme the theme against which this entry was inflated, or
44     *              {@code null} if the entry has no theme applied
45     * @param entry the entry to cache
46     */
47    public void put(long key, @Nullable Theme theme, @NonNull T entry) {
48        put(key, theme, entry, true);
49    }
50
51    /**
52     * Adds a new entry to the cache.
53     *
54     * @param key a key that uniquely identifies the entry
55     * @param theme the theme against which this entry was inflated, or
56     *              {@code null} if the entry has no theme applied
57     * @param entry the entry to cache
58     * @param usesTheme {@code true} if the entry is affected theme changes,
59     *                  {@code false} otherwise
60     */
61    public void put(long key, @Nullable Theme theme, @NonNull T entry, boolean usesTheme) {
62        if (entry == null) {
63            return;
64        }
65
66        synchronized (this) {
67            final LongSparseArray<WeakReference<T>> entries;
68            if (!usesTheme) {
69                entries = getUnthemedLocked(true);
70            } else {
71                entries = getThemedLocked(theme, true);
72            }
73            if (entries != null) {
74                entries.put(key, new WeakReference<>(entry));
75            }
76        }
77    }
78
79    /**
80     * Returns an entry from the cache.
81     *
82     * @param key a key that uniquely identifies the entry
83     * @param theme the theme where the entry will be used
84     * @return a cached entry, or {@code null} if not in the cache
85     */
86    @Nullable
87    public T get(long key, @Nullable Theme theme) {
88        // The themed (includes null-themed) and unthemed caches are mutually
89        // exclusive, so we'll give priority to whichever one we think we'll
90        // hit first. Since most of the framework drawables are themed, that's
91        // probably going to be the themed cache.
92        synchronized (this) {
93            final LongSparseArray<WeakReference<T>> themedEntries = getThemedLocked(theme, false);
94            if (themedEntries != null) {
95                final WeakReference<T> themedEntry = themedEntries.get(key);
96                if (themedEntry != null) {
97                    return themedEntry.get();
98                }
99            }
100
101            final LongSparseArray<WeakReference<T>> unthemedEntries = getUnthemedLocked(false);
102            if (unthemedEntries != null) {
103                final WeakReference<T> unthemedEntry = unthemedEntries.get(key);
104                if (unthemedEntry != null) {
105                    return unthemedEntry.get();
106                }
107            }
108        }
109
110        return null;
111    }
112
113    /**
114     * Prunes cache entries that have been invalidated by a configuration
115     * change.
116     *
117     * @param configChanges a bitmask of configuration changes
118     */
119    public void onConfigurationChange(@Config int configChanges) {
120        prune(configChanges);
121    }
122
123    /**
124     * Returns whether a cached entry has been invalidated by a configuration
125     * change.
126     *
127     * @param entry a cached entry
128     * @param configChanges a non-zero bitmask of configuration changes
129     * @return {@code true} if the entry is invalid, {@code false} otherwise
130     */
131    protected abstract boolean shouldInvalidateEntry(@NonNull T entry, int configChanges);
132
133    /**
134     * Returns the cached data for the specified theme, optionally creating a
135     * new entry if one does not already exist.
136     *
137     * @param t the theme for which to return cached data
138     * @param create {@code true} to create an entry if one does not already
139     *               exist, {@code false} otherwise
140     * @return the cached data for the theme, or {@code null} if the cache is
141     *         empty and {@code create} was {@code false}
142     */
143    @Nullable
144    private LongSparseArray<WeakReference<T>> getThemedLocked(@Nullable Theme t, boolean create) {
145        if (t == null) {
146            if (mNullThemedEntries == null && create) {
147                mNullThemedEntries = new LongSparseArray<>(1);
148            }
149            return mNullThemedEntries;
150        }
151
152        if (mThemedEntries == null) {
153            if (create) {
154                mThemedEntries = new ArrayMap<>(1);
155            } else {
156                return null;
157            }
158        }
159
160        final ThemeKey key = t.getKey();
161        LongSparseArray<WeakReference<T>> cache = mThemedEntries.get(key);
162        if (cache == null && create) {
163            cache = new LongSparseArray<>(1);
164
165            final ThemeKey keyClone = key.clone();
166            mThemedEntries.put(keyClone, cache);
167        }
168
169        return cache;
170    }
171
172    /**
173     * Returns the theme-agnostic cached data.
174     *
175     * @param create {@code true} to create an entry if one does not already
176     *               exist, {@code false} otherwise
177     * @return the theme-agnostic cached data, or {@code null} if the cache is
178     *         empty and {@code create} was {@code false}
179     */
180    @Nullable
181    private LongSparseArray<WeakReference<T>> getUnthemedLocked(boolean create) {
182        if (mUnthemedEntries == null && create) {
183            mUnthemedEntries = new LongSparseArray<>(1);
184        }
185        return mUnthemedEntries;
186    }
187
188    /**
189     * Prunes cache entries affected by configuration changes or where weak
190     * references have expired.
191     *
192     * @param configChanges a bitmask of configuration changes, or {@code 0} to
193     *                      simply prune missing weak references
194     * @return {@code true} if the cache is completely empty after pruning
195     */
196    private boolean prune(@Config int configChanges) {
197        synchronized (this) {
198            if (mThemedEntries != null) {
199                for (int i = mThemedEntries.size() - 1; i >= 0; i--) {
200                    if (pruneEntriesLocked(mThemedEntries.valueAt(i), configChanges)) {
201                        mThemedEntries.removeAt(i);
202                    }
203                }
204            }
205
206            pruneEntriesLocked(mNullThemedEntries, configChanges);
207            pruneEntriesLocked(mUnthemedEntries, configChanges);
208
209            return mThemedEntries == null && mNullThemedEntries == null
210                    && mUnthemedEntries == null;
211        }
212    }
213
214    private boolean pruneEntriesLocked(@Nullable LongSparseArray<WeakReference<T>> entries,
215            @Config int configChanges) {
216        if (entries == null) {
217            return true;
218        }
219
220        for (int i = entries.size() - 1; i >= 0; i--) {
221            final WeakReference<T> ref = entries.valueAt(i);
222            if (ref == null || pruneEntryLocked(ref.get(), configChanges)) {
223                entries.removeAt(i);
224            }
225        }
226
227        return entries.size() == 0;
228    }
229
230    private boolean pruneEntryLocked(@Nullable T entry, @Config int configChanges) {
231        return entry == null || (configChanges != 0
232                && shouldInvalidateEntry(entry, configChanges));
233    }
234}
235