--- /dev/null
+/*
+ * 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.support.v2.util;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Static library version of {@code android.util.LruCache}. Used to write apps
+ * that run on API levels prior to 12. When running on API level 12 or above,
+ * this implementation is still used; it does not try to switch to the
+ * framework's implementation. See the framework SDK documentation for a class
+ * overview.
+ */
+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 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 final V get(K key) {
+ if (key == null) {
+ throw new NullPointerException("key == null");
+ }
+
+ V mapValue;
+ synchronized (this) {
+ mapValue = map.get(key);
+ if (mapValue != null) {
+ hitCount++;
+ return mapValue;
+ }
+ missCount++;
+ }
+
+ /*
+ * Attempt to create a value. This may take a long time, and the map
+ * may be different when create() returns. If a conflicting value was
+ * added to the map while create() was working, we leave that value in
+ * the map and release the created value.
+ */
+
+ V createdValue = create(key);
+ if (createdValue == null) {
+ return null;
+ }
+
+ synchronized (this) {
+ createCount++;
+ mapValue = map.put(key, createdValue);
+
+ if (mapValue != null) {
+ // There was a conflict so undo that last put
+ map.put(key, mapValue);
+ } else {
+ size += safeSizeOf(key, createdValue);
+ }
+ }
+
+ if (mapValue != null) {
+ entryRemoved(false, key, createdValue, mapValue);
+ return mapValue;
+ } else {
+ trimToSize(maxSize);
+ return createdValue;
+ }
+ }
+
+ /**
+ * Caches {@code value} for {@code key}. The value is moved to the head of
+ * the queue.
+ *
+ * @return the previous value mapped by {@code key}.
+ */
+ public final V put(K key, V value) {
+ if (key == null || value == null) {
+ throw new NullPointerException("key == null || value == null");
+ }
+
+ V previous;
+ synchronized (this) {
+ putCount++;
+ size += safeSizeOf(key, value);
+ previous = map.put(key, value);
+ if (previous != null) {
+ size -= safeSizeOf(key, previous);
+ }
+ }
+
+ if (previous != null) {
+ entryRemoved(false, key, previous, value);
+ }
+
+ trimToSize(maxSize);
+ return previous;
+ }
+
+ /**
+ * @param maxSize the maximum size of the cache before returning. May be -1
+ * to evict even 0-sized elements.
+ */
+ private void trimToSize(int maxSize) {
+ while (true) {
+ K key;
+ V value;
+ synchronized (this) {
+ if (size < 0 || (map.isEmpty() && size != 0)) {
+ throw new IllegalStateException(getClass().getName()
+ + ".sizeOf() is reporting inconsistent results!");
+ }
+
+ if (size <= maxSize || map.isEmpty()) {
+ break;
+ }
+
+ Map.Entry<K, V> toEvict = map.entrySet().iterator().next();
+ key = toEvict.getKey();
+ value = toEvict.getValue();
+ map.remove(key);
+ size -= safeSizeOf(key, value);
+ evictionCount++;
+ }
+
+ entryRemoved(true, key, value, null);
+ }
+ }
+
+ /**
+ * Removes the entry for {@code key} if it exists.
+ *
+ * @return the previous value mapped by {@code key}.
+ */
+ public final V remove(K key) {
+ if (key == null) {
+ throw new NullPointerException("key == null");
+ }
+
+ V previous;
+ synchronized (this) {
+ previous = map.remove(key);
+ if (previous != null) {
+ size -= safeSizeOf(key, previous);
+ }
+ }
+
+ if (previous != null) {
+ entryRemoved(false, key, previous, null);
+ }
+
+ return previous;
+ }
+
+ /**
+ * Called for entries that have been evicted or removed. This method is
+ * invoked when a value is evicted to make space, removed by a call to
+ * {@link #remove}, or replaced by a call to {@link #put}. The default
+ * implementation does nothing.
+ *
+ * <p>The method is called without synchronization: other threads may
+ * access the cache while this method is executing.
+ *
+ * @param evicted true if the entry is being removed to make space, false
+ * if the removal was caused by a {@link #put} or {@link #remove}.
+ * @param newValue the new value for {@code key}, if it exists. If non-null,
+ * this removal was caused by a {@link #put}. Otherwise it was caused by
+ * an eviction or a {@link #remove}.
+ */
+ protected void entryRemoved(boolean evicted, K key, V oldValue, V newValue) {}
+
+ /**
+ * 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.
+ *
+ * <p>The method is called without synchronization: other threads may
+ * access the cache while this method is executing.
+ *
+ * <p>If a value for {@code key} exists in the cache when this method
+ * returns, the created value will be released with {@link #entryRemoved}
+ * and discarded. This can occur when multiple threads request the same key
+ * at the same time (causing multiple values to be created), or when one
+ * thread calls {@link #put} while another is creating a value for the same
+ * key.
+ */
+ 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 #entryRemoved} on each removed entry.
+ */
+ public final void evictAll() {
+ trimToSize(-1); // -1 will evict 0-sized elements
+ }
+
+ /**
+ * For caches that do not override {@link #sizeOf}, this returns the number
+ * of entries in the cache. For all other caches, this returns the sum of
+ * the sizes of the entries in this cache.
+ */
+ public synchronized final int size() {
+ return size;
+ }
+
+ /**
+ * For caches that do not override {@link #sizeOf}, this returns the maximum
+ * number of entries in the cache. For all other caches, this returns the
+ * maximum sum of the sizes of the entries in this cache.
+ */
+ public synchronized final int maxSize() {
+ return maxSize;
+ }
+
+ /**
+ * 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);
+ }
+}
notaz.gp2x.de / android_pandora.git / blobdiff