Dianne Hackborn | a83ce1d | 2015-03-11 15:16:13 -0700 | [diff] [blame] | 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 | |
| 17 | package android.os; |
| 18 | |
| 19 | import java.util.HashMap; |
| 20 | |
| 21 | /** |
| 22 | * Helper class for writing pooled strings into a Parcel. It must be used |
| 23 | * in conjunction with {@link android.os.PooledStringReader}. This really needs |
| 24 | * to be pushed in to Parcel itself, but doing that is... complicated. |
| 25 | * @hide |
| 26 | */ |
| 27 | public class PooledStringWriter { |
| 28 | private final Parcel mOut; |
| 29 | |
| 30 | /** |
| 31 | * Book-keeping for writing pooled string objects, mapping strings we have |
| 32 | * written so far to their index in the pool. We deliberately use HashMap |
| 33 | * here since performance is critical, we expect to be doing lots of adds to |
| 34 | * it, and it is only a temporary object so its overall memory footprint is |
| 35 | * not a signifciant issue. |
| 36 | */ |
| 37 | private final HashMap<String, Integer> mPool; |
| 38 | |
| 39 | /** |
| 40 | * Book-keeping for writing pooling string objects, indicating where we |
| 41 | * started writing the pool, which is where we need to ultimately store |
| 42 | * how many strings are in the pool. |
| 43 | */ |
| 44 | private int mStart; |
| 45 | |
| 46 | /** |
| 47 | * Next available index in the pool. |
| 48 | */ |
| 49 | private int mNext; |
| 50 | |
| 51 | public PooledStringWriter(Parcel out) { |
| 52 | mOut = out; |
| 53 | mPool = new HashMap<>(); |
| 54 | mStart = out.dataPosition(); |
| 55 | out.writeInt(0); // reserve space for final pool size. |
| 56 | } |
| 57 | |
| 58 | public void writeString(String str) { |
| 59 | final Integer cur = mPool.get(str); |
| 60 | if (cur != null) { |
| 61 | mOut.writeInt(cur); |
| 62 | } else { |
| 63 | mPool.put(str, mNext); |
| 64 | mOut.writeInt(-(mNext+1)); |
| 65 | mOut.writeString(str); |
| 66 | mNext++; |
| 67 | } |
| 68 | } |
| 69 | |
Dianne Hackborn | 782d498 | 2015-07-08 17:36:37 -0700 | [diff] [blame] | 70 | public int getStringCount() { |
| 71 | return mPool.size(); |
| 72 | } |
| 73 | |
Dianne Hackborn | a83ce1d | 2015-03-11 15:16:13 -0700 | [diff] [blame] | 74 | public void finish() { |
| 75 | final int pos = mOut.dataPosition(); |
| 76 | mOut.setDataPosition(mStart); |
| 77 | mOut.writeInt(mNext); |
| 78 | mOut.setDataPosition(pos); |
| 79 | } |
| 80 | } |