TileList.java revision a1470623b0f7c52c9e3985012bf9daeb692d7bcc 
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.support.v7.util;
18
19import android.util.SparseArray;
20
21import java.lang.reflect.Array;
22
23/**
24 * A sparse collection of tiles sorted for efficient access.
25 */
26class TileList<T> {
27
28    final int mTileSize;
29
30    // Keyed by start position.
31    private final SparseArray<Tile<T>> mTiles = new SparseArray<Tile<T>>(10);
32
33    Tile<T> mLastAccessedTile;
34
35    public TileList(int tileSize) {
36        mTileSize = tileSize;
37    }
38
39    public T getItemAt(int pos) {
40        if (mLastAccessedTile == null || !mLastAccessedTile.containsPosition(pos)) {
41            final int startPosition = pos - (pos % mTileSize);
42            final int index = mTiles.indexOfKey(startPosition);
43            if (index < 0) {
44                return null;
45            }
46            mLastAccessedTile = mTiles.valueAt(index);
47        }
48        return mLastAccessedTile.getByPosition(pos);
49    }
50
51    public int size() {
52        return mTiles.size();
53    }
54
55    public void clear() {
56        mTiles.clear();
57    }
58
59    public Tile<T> getAtIndex(int index) {
60        return mTiles.valueAt(index);
61    }
62
63    public Tile<T> addOrReplace(Tile<T> newTile) {
64        final int index = mTiles.indexOfKey(newTile.mStartPosition);
65        if (index < 0) {
66            mTiles.put(newTile.mStartPosition, newTile);
67            return null;
68        }
69        Tile<T> oldTile = mTiles.valueAt(index);
70        mTiles.setValueAt(index, newTile);
71        if (mLastAccessedTile == oldTile) {
72            mLastAccessedTile = newTile;
73        }
74        return oldTile;
75    }
76
77    public Tile<T> removeAtPos(int startPosition) {
78        Tile<T> tile = mTiles.get(startPosition);
79        if (mLastAccessedTile == tile) {
80            mLastAccessedTile = null;
81        }
82        mTiles.delete(startPosition);
83        return tile;
84    }
85
86    public static class Tile<T> {
87        public final T[] mItems;
88        public int mStartPosition;
89        public int mItemCount;
90        Tile<T> mNext;  // Used only for pooling recycled tiles.
91
92        public Tile(Class<T> klass, int size) {
93            //noinspection unchecked
94            mItems = (T[]) Array.newInstance(klass, size);
95        }
96
97        boolean containsPosition(int pos) {
98            return mStartPosition <= pos && pos < mStartPosition + mItemCount;
99        }
100
101        T getByPosition(int pos) {
102            return mItems[pos - mStartPosition];
103        }
104    }
105}
106