1 files changed, 212 insertions, 0 deletions
diff --git a/src/com/android/photos/data/SparseArrayBitmapPool.java b/src/com/android/photos/data/SparseArrayBitmapPool.java
new file mode 100644
index 000000000..95e10267b
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+++ b/src/com/android/photos/data/SparseArrayBitmapPool.java
@@ -0,0 +1,212 @@
+/*
+ * Copyright (C) 2013 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 com.android.photos.data;
+
+import android.graphics.Bitmap;
+import android.util.SparseArray;
+
+import android.util.Pools.Pool;
+import android.util.Pools.SimplePool;
+
+/**
+ * Bitmap pool backed by a sparse array indexing linked lists of bitmaps
+ * sharing the same width. Performance will degrade if using this to store
+ * many bitmaps with the same width but many different heights.
+ */
+public class SparseArrayBitmapPool {
+
+    private int mCapacityBytes;
+    private SparseArray<Node> mStore = new SparseArray<Node>();
+    private int mSizeBytes = 0;
+
+    private Pool<Node> mNodePool;
+    private Node mPoolNodesHead = null;
+    private Node mPoolNodesTail = null;
+
+    protected static class Node {
+        Bitmap bitmap;
+
+        // Each node is part of two doubly linked lists:
+        // - A pool-level list (accessed by mPoolNodesHead and mPoolNodesTail)
+        //   that is used for FIFO eviction of nodes when the pool gets full.
+        // - A bucket-level list for each index of the sparse array, so that
+        //   each index can store more than one item.
+        Node prevInBucket;
+        Node nextInBucket;
+        Node nextInPool;
+        Node prevInPool;
+    }
+
+    /**
+     * @param capacityBytes Maximum capacity of the pool in bytes.
+     * @param nodePool Shared pool to use for recycling linked list nodes, or null.
+     */
+    public SparseArrayBitmapPool(int capacityBytes, Pool<Node> nodePool) {
+        mCapacityBytes = capacityBytes;
+        if (nodePool == null) {
+            mNodePool = new SimplePool<Node>(32);
+        } else {
+            mNodePool = nodePool;
+        }
+    }
+
+    /**
+     * Set the maximum capacity of the pool, and if necessary trim it down to size.
+     */
+    public synchronized void setCapacity(int capacityBytes) {
+        mCapacityBytes = capacityBytes;
+
+        // No-op unless current size exceeds the new capacity.
+        freeUpCapacity(0);
+    }
+
+    private void freeUpCapacity(int bytesNeeded) {
+        int targetSize = mCapacityBytes - bytesNeeded;
+        // Repeatedly remove the oldest node until we have freed up at least bytesNeeded.
+        while (mPoolNodesTail != null && mSizeBytes > targetSize) {
+            unlinkAndRecycleNode(mPoolNodesTail, true);
+        }
+    }
+
+    private void unlinkAndRecycleNode(Node n, boolean recycleBitmap) {
+        // Unlink the node from its sparse array bucket list.
+        if (n.prevInBucket != null) {
+            // This wasn't the head, update the previous node.
+            n.prevInBucket.nextInBucket = n.nextInBucket;
+        } else {
+            // This was the head of the bucket, replace it with the next node.
+            mStore.put(n.bitmap.getWidth(), n.nextInBucket);
+        }
+        if (n.nextInBucket != null) {
+            // This wasn't the tail, update the next node.
+            n.nextInBucket.prevInBucket = n.prevInBucket;
+        }
+
+        // Unlink the node from the pool-wide list.
+        if (n.prevInPool != null) {
+            // This wasn't the head, update the previous node.
+            n.prevInPool.nextInPool = n.nextInPool;
+        } else {
+            // This was the head of the pool-wide list, update the head pointer.
+            mPoolNodesHead = n.nextInPool;
+        }
+        if (n.nextInPool != null) {
+            // This wasn't the tail, update the next node.
+            n.nextInPool.prevInPool = n.prevInPool;
+        } else {
+            // This was the tail, update the tail pointer.
+            mPoolNodesTail = n.prevInPool;
+        }
+
+        // Recycle the node.
+        n.nextInBucket = null;
+        n.nextInPool = null;
+        n.prevInBucket = null;
+        n.prevInPool = null;
+        mSizeBytes -= n.bitmap.getByteCount();
+        if (recycleBitmap) n.bitmap.recycle();
+        n.bitmap = null;
+        mNodePool.release(n);
+    }
+
+    /**
+     * @return Capacity of the pool in bytes.
+     */
+    public synchronized int getCapacity() {
+        return mCapacityBytes;
+    }
+
+    /**
+     * @return Total size in bytes of the bitmaps stored in the pool.
+     */
+    public synchronized int getSize() {
+        return mSizeBytes;
+    }
+
+    /**
+     * @return Bitmap from the pool with the desired height/width or null if none available.
+     */
+    public synchronized Bitmap get(int width, int height) {
+        Node cur = mStore.get(width);
+
+        // Traverse the list corresponding to the width bucket in the
+        // sparse array, and unlink and return the first bitmap that
+        // also has the correct height.
+        while (cur != null) {
+            if (cur.bitmap.getHeight() == height) {
+                Bitmap b = cur.bitmap;
+                unlinkAndRecycleNode(cur, false);
+                return b;
+            }
+            cur = cur.nextInBucket;
+        }
+        return null;
+    }
+
+    /**
+     * Adds the given bitmap to the pool.
+     * @return Whether the bitmap was added to the pool.
+     */
+    public synchronized boolean put(Bitmap b) {
+        if (b == null) {
+            return false;
+        }
+
+        // Ensure there is enough room to contain the new bitmap.
+        int bytes = b.getByteCount();
+        freeUpCapacity(bytes);
+
+        Node newNode = mNodePool.acquire();
+        if (newNode == null) {
+            newNode = new Node();
+        }
+        newNode.bitmap = b;
+
+        // We append to the head, and freeUpCapacity clears from the tail,
+        // resulting in FIFO eviction.
+        newNode.prevInBucket = null;
+        newNode.prevInPool = null;
+        newNode.nextInPool = mPoolNodesHead;
+        mPoolNodesHead = newNode;
+
+        // Insert the node into its appropriate bucket based on width.
+        int key = b.getWidth();
+        newNode.nextInBucket = mStore.get(key);
+        if (newNode.nextInBucket != null) {
+            // The bucket already had nodes, update the old head.
+            newNode.nextInBucket.prevInBucket = newNode;
+        }
+        mStore.put(key, newNode);
+
+        if (newNode.nextInPool == null) {
+            // This is the only node in the list, update the tail pointer.
+            mPoolNodesTail = newNode;
+        } else {
+            newNode.nextInPool.prevInPool = newNode;
+        }
+        mSizeBytes += bytes;
+        return true;
+    }
+
+    /**
+     * Empty the pool, recycling all the bitmaps currently in it.
+     */
+    public synchronized void clear() {
+        // Clearing is equivalent to ensuring all the capacity is available.
+        freeUpCapacity(mCapacityBytes);
+    }
+}