Makoto Onuki | 4501c61d | 2017-07-27 15:56:40 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2017 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.content.pm; |
| 18 | |
| 19 | import android.os.Parcel; |
| 20 | import android.util.Log; |
| 21 | |
| 22 | import java.util.ArrayList; |
| 23 | import java.util.HashMap; |
| 24 | |
| 25 | /** |
| 26 | * Helper classes to read from and write to Parcel with pooled strings. |
| 27 | * |
| 28 | * @hide |
| 29 | */ |
| 30 | public class PackageParserCacheHelper { |
| 31 | private PackageParserCacheHelper() { |
| 32 | } |
| 33 | |
| 34 | private static final String TAG = "PackageParserCacheHelper"; |
| 35 | private static final boolean DEBUG = false; |
| 36 | |
| 37 | /** |
| 38 | * Parcel read helper with a string pool. |
| 39 | */ |
| 40 | public static class ReadHelper extends Parcel.ReadWriteHelper { |
| 41 | private final ArrayList<String> mStrings = new ArrayList<>(); |
| 42 | |
| 43 | private final Parcel mParcel; |
| 44 | |
| 45 | public ReadHelper(Parcel p) { |
| 46 | mParcel = p; |
| 47 | } |
| 48 | |
| 49 | /** |
| 50 | * Prepare to read from a parcel, and install itself as a read-write helper. |
| 51 | * |
| 52 | * (We don't do it in the constructor to avoid calling methods before the constructor |
| 53 | * finishes.) |
| 54 | */ |
| 55 | public void startAndInstall() { |
| 56 | mStrings.clear(); |
| 57 | |
| 58 | final int poolPosition = mParcel.readInt(); |
| 59 | final int startPosition = mParcel.dataPosition(); |
| 60 | |
| 61 | // The pool is at the end of the parcel. |
| 62 | mParcel.setDataPosition(poolPosition); |
| 63 | mParcel.readStringList(mStrings); |
| 64 | |
| 65 | // Then move back. |
| 66 | mParcel.setDataPosition(startPosition); |
| 67 | |
| 68 | if (DEBUG) { |
| 69 | Log.i(TAG, "Read " + mStrings.size() + " strings"); |
| 70 | for (int i = 0; i < mStrings.size(); i++) { |
| 71 | Log.i(TAG, " " + i + ": \"" + mStrings.get(i) + "\""); |
| 72 | } |
| 73 | } |
| 74 | |
| 75 | mParcel.setReadWriteHelper(this); |
| 76 | } |
| 77 | |
| 78 | /** |
| 79 | * Read an string index from a parcel, and returns the corresponding string from the pool. |
| 80 | */ |
| 81 | @Override |
| 82 | public String readString(Parcel p) { |
| 83 | return mStrings.get(p.readInt()); |
| 84 | } |
| 85 | } |
| 86 | |
| 87 | /** |
| 88 | * Parcel write helper with a string pool. |
| 89 | */ |
| 90 | public static class WriteHelper extends Parcel.ReadWriteHelper { |
| 91 | private final ArrayList<String> mStrings = new ArrayList<>(); |
| 92 | |
| 93 | private final HashMap<String, Integer> mIndexes = new HashMap<>(); |
| 94 | |
| 95 | private final Parcel mParcel; |
| 96 | private final int mStartPos; |
| 97 | |
| 98 | /** |
| 99 | * Constructor. Prepare a parcel, and install it self as a read-write helper. |
| 100 | */ |
| 101 | public WriteHelper(Parcel p) { |
| 102 | mParcel = p; |
| 103 | mStartPos = p.dataPosition(); |
| 104 | mParcel.writeInt(0); // We come back later here and write the pool position. |
| 105 | |
| 106 | mParcel.setReadWriteHelper(this); |
| 107 | } |
| 108 | |
| 109 | /** |
| 110 | * Instead of writing a string directly to a parcel, this method adds it to the pool, |
| 111 | * and write the index in the pool to the parcel. |
| 112 | */ |
| 113 | @Override |
| 114 | public void writeString(Parcel p, String s) { |
| 115 | final Integer cur = mIndexes.get(s); |
| 116 | if (cur != null) { |
| 117 | // String already in the pool. Just write the index. |
| 118 | p.writeInt(cur); // Already in the pool. |
| 119 | if (DEBUG) { |
| 120 | Log.i(TAG, "Duplicate '" + s + "' at " + cur); |
| 121 | } |
| 122 | } else { |
| 123 | // Not in the pool. Add to the pool, and write the index. |
| 124 | final int index = mStrings.size(); |
| 125 | mIndexes.put(s, index); |
| 126 | mStrings.add(s); |
| 127 | |
| 128 | if (DEBUG) { |
| 129 | Log.i(TAG, "New '" + s + "' at " + index); |
| 130 | } |
| 131 | |
| 132 | p.writeInt(index); |
| 133 | } |
| 134 | } |
| 135 | |
| 136 | /** |
| 137 | * Closes a parcel by appending the string pool at the end and updating the pool offset, |
| 138 | * which it assumes is at the first byte. It also uninstalls itself as a read-write helper. |
| 139 | */ |
| 140 | public void finishAndUninstall() { |
| 141 | // Uninstall first, so that writeStringList() uses the native writeString. |
| 142 | mParcel.setReadWriteHelper(null); |
| 143 | |
| 144 | final int poolPosition = mParcel.dataPosition(); |
| 145 | mParcel.writeStringList(mStrings); |
| 146 | |
| 147 | mParcel.setDataPosition(mStartPos); |
| 148 | mParcel.writeInt(poolPosition); |
| 149 | |
| 150 | // Move back to the end. |
| 151 | mParcel.setDataPosition(mParcel.dataSize()); |
| 152 | if (DEBUG) { |
| 153 | Log.i(TAG, "Wrote " + mStrings.size() + " strings"); |
| 154 | } |
| 155 | } |
| 156 | } |
| 157 | } |