New LRU cache class. (e2c1f4a0) · Commits · e / os / android_frameworks_base

api/current.xml

+190 −1

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		@@ -204632,6 +204632,195 @@
		</parameter>
		</method>
		</class>
		<class name="LruCache"
		extends="java.lang.Object"
		abstract="false"
		static="false"
		final="false"
		deprecated="not deprecated"
		visibility="public"
		>
		<constructor name="LruCache"
		type="android.util.LruCache"
		static="false"
		final="false"
		deprecated="not deprecated"
		visibility="public"
		>
		<parameter name="maxSize" type="int">
		</parameter>
		</constructor>
		<method name="create"
		return="V"
		abstract="false"
		native="false"
		synchronized="false"
		static="false"
		final="false"
		deprecated="not deprecated"
		visibility="protected"
		>
		<parameter name="key" type="K">
		</parameter>
		</method>
		<method name="createCount"
		return="int"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		<method name="entryEvicted"
		return="void"
		abstract="false"
		native="false"
		synchronized="false"
		static="false"
		final="false"
		deprecated="not deprecated"
		visibility="protected"
		>
		<parameter name="key" type="K">
		</parameter>
		<parameter name="value" type="V">
		</parameter>
		</method>
		<method name="evictAll"
		return="void"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		<method name="evictionCount"
		return="int"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		<method name="get"
		return="V"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		<parameter name="key" type="K">
		</parameter>
		</method>
		<method name="hitCount"
		return="int"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		<method name="missCount"
		return="int"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		<method name="put"
		return="V"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		<parameter name="key" type="K">
		</parameter>
		<parameter name="value" type="V">
		</parameter>
		</method>
		<method name="putCount"
		return="int"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		<method name="size"
		return="int"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		<method name="sizeOf"
		return="int"
		abstract="false"
		native="false"
		synchronized="false"
		static="false"
		final="false"
		deprecated="not deprecated"
		visibility="protected"
		>
		<parameter name="key" type="K">
		</parameter>
		<parameter name="value" type="V">
		</parameter>
		</method>
		<method name="snapshot"
		return="java.util.Map<K, V>"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		<method name="toString"
		return="java.lang.String"
		abstract="false"
		native="false"
		synchronized="true"
		static="false"
		final="true"
		deprecated="not deprecated"
		visibility="public"
		>
		</method>
		</class>
		<class name="MalformedJsonException"
		extends="java.io.IOException"
		abstract="false"
		@@ -263805,7 +263994,7 @@
		deprecated="not deprecated"
		visibility="public"
		>
		<parameter name="t" type="T">
		<parameter name="arg0" type="T">
		</parameter>
		</method>
		</interface>

core/java/android/util/LruCache.java

0 → 100644

+249 −0

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		/*
		* Copyright (C) 2011 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		package android.util;

		import java.util.LinkedHashMap;
		import java.util.Map;

		/**
		* A cache that holds strong references to a limited number of values. Each time
		* a value is accessed, it is moved to the head of a queue. When a value is
		* added to a full cache, the value at the end of that queue is evicted and may
		* become eligible for garbage collection.
		*
		* <p>If your cached values hold resources that need to be explicitly released,
		* override {@link #entryEvicted}. This method is only invoked when values are
		* evicted. Values replaced by calls to {@link #put} must be released manually.
		*
		* <p>If a cache miss should be computed on demand for the corresponding keys,
		* override {@link #create}. This simplifies the calling code, allowing it to
		* assume a value will always be returned, even when there's a cache miss.
		*
		* <p>By default, the cache size is measured in the number of entries. Override
		* {@link #sizeOf} to size the cache in different units. For, this cache is
		* limited to 4MiB of bitmaps:
		* <pre> {@code
		* int cacheSize = 4 * 1024 * 1024; // 4MiB
		* LruCache<String, Bitmap> bitmapCache = new LruCache<String, Bitmap>(cacheSize) {
		* @Override protected int sizeOf(String key, Bitmap value) {
		* return value.getByteCount();
		* }
		* }}</pre>
		*/
		public class LruCache<K, V> {
		private final LinkedHashMap<K, V> map;

		/** Size of this cache in units. Not necessarily the number of elements. */
		private int size;
		private final int maxSize;

		private int putCount;
		private int createCount;
		private int evictionCount;
		private int hitCount;
		private int missCount;

		/**
		* @param maxSize for caches that do not override {@link #sizeOf}, this is
		* the maximum number of entries in the cache. For all other caches,
		* this is the maximum sum of the sizes of the entries in this cache.
		*/
		public LruCache(int maxSize) {
		if (maxSize <= 0) {
		throw new IllegalArgumentException("maxSize <= 0");
		}
		this.maxSize = maxSize;
		this.map = new LinkedHashMap<K, V>(0, 0.75f, true);
		}

		/**
		* Returns the value for {@code key} if it exists in the cache or can be
		* created by {@code #create}. If a value was returned, it is moved to the
		* head of the queue. This returns null if a value is not cached and cannot
		* be created.
		*/
		public synchronized final V get(K key) {
		if (key == null) {
		throw new NullPointerException();
		}

		V result = map.get(key);
		if (result != null) {
		hitCount++;
		return result;
		}

		missCount++;

		// TODO: release the lock while calling this potentially slow user code
		result = create(key);

		if (result != null) {
		createCount++;
		size += safeSizeOf(key, result);
		map.put(key, result);
		trimToSize(maxSize);
		}
		return result;
		}

		/**
		* Caches {@code value} for {@code key}. The value is moved to the head of
		* the queue.
		*
		* @return the previous value mapped by {@code key}. Although that entry is
		* no longer cached, it has not been passed to {@link #entryEvicted}.
		*/
		public synchronized final V put(K key, V value) {
		if (key == null \|\| value == null) {
		throw new NullPointerException();
		}

		putCount++;
		size += safeSizeOf(key, value);
		V previous = map.put(key, value);
		if (previous != null) {
		size -= safeSizeOf(key, previous);
		}
		trimToSize(maxSize);
		return previous;
		}

		private void trimToSize(int maxSize) {
		while (size > maxSize) {
		Map.Entry<K, V> toEvict = map.eldest();
		if (toEvict == null) {
		break; // map is empty; if size is not 0 then throw an error below
		}

		K key = toEvict.getKey();
		V value = toEvict.getValue();
		map.remove(key);
		size -= safeSizeOf(key, value);
		evictionCount++;

		// TODO: release the lock while calling this potentially slow user code
		entryEvicted(key, value);
		}

		if (size < 0 \|\| (map.isEmpty() && size != 0)) {
		throw new IllegalStateException(getClass().getName()
		+ ".sizeOf() is reporting inconsistent results!");
		}
		}

		/**
		* Called for entries that have reached the tail of the least recently used
		* queue and are be removed. The default implementation does nothing.
		*/
		protected void entryEvicted(K key, V value) {}

		/**
		* Called after a cache miss to compute a value for the corresponding key.
		* Returns the computed value or null if no value can be computed. The
		* default implementation returns null.
		*/
		protected V create(K key) {
		return null;
		}

		private int safeSizeOf(K key, V value) {
		int result = sizeOf(key, value);
		if (result < 0) {
		throw new IllegalStateException("Negative size: " + key + "=" + value);
		}
		return result;
		}

		/**
		* Returns the size of the entry for {@code key} and {@code value} in
		* user-defined units. The default implementation returns 1 so that size
		* is the number of entries and max size is the maximum number of entries.
		*
		* <p>An entry's size must not change while it is in the cache.
		*/
		protected int sizeOf(K key, V value) {
		return 1;
		}

		/**
		* Clear the cache, calling {@link #entryEvicted} on each removed entry.
		*/
		public synchronized final void evictAll() {
		trimToSize(-1); // -1 will evict 0-sized elements
		}

		/**
		* For caches that do not override {@link #sizeOf}, this is the number of
		* entries in the cache. For all other caches, this is the sum of the sizes
		* of the entries in this cache.
		*/
		public synchronized final int size() {
		return size;
		}

		/**
		* Returns the number of times {@link #get} returned a value.
		*/
		public synchronized final int hitCount() {
		return hitCount;
		}

		/**
		* Returns the number of times {@link #get} returned null or required a new
		* value to be created.
		*/
		public synchronized final int missCount() {
		return missCount;
		}

		/**
		* Returns the number of times {@link #create(Object)} returned a value.
		*/
		public synchronized final int createCount() {
		return createCount;
		}

		/**
		* Returns the number of times {@link #put} was called.
		*/
		public synchronized final int putCount() {
		return putCount;
		}

		/**
		* Returns the number of values that have been evicted.
		*/
		public synchronized final int evictionCount() {
		return evictionCount;
		}

		/**
		* Returns a copy of the current contents of the cache, ordered from least
		* recently accessed to most recently accessed.
		*/
		public synchronized final Map<K, V> snapshot() {
		return new LinkedHashMap<K, V>(map);
		}

		@Override public synchronized final String toString() {
		int accesses = hitCount + missCount;
		int hitPercent = accesses != 0 ? (100 * hitCount / accesses) : 0;
		return String.format("LruCache[maxSize=%d,hits=%d,misses=%d,hitRate=%d%%]",
		maxSize, hitCount, missCount, hitPercent);
		}
		}

core/tests/coretests/src/android/util/LruCacheTest.java

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