1/* 2 * Copyright (C) 2006 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.database; 18 19import android.os.Bundle; 20import android.os.IBinder; 21import android.os.RemoteException; 22import android.util.Log; 23 24 25/** 26 * Wraps a BulkCursor around an existing Cursor making it remotable. 27 * <p> 28 * If the wrapped cursor returns non-null from {@link CrossProcessCursor#getWindow} 29 * then it is assumed to own the window. Otherwise, the adaptor provides a 30 * window to be filled and ensures it gets closed as needed during deactivation 31 * and requeries. 32 * </p> 33 * 34 * {@hide} 35 */ 36public final class CursorToBulkCursorAdaptor extends BulkCursorNative 37 implements IBinder.DeathRecipient { 38 private static final String TAG = "Cursor"; 39 40 private final Object mLock = new Object(); 41 private final String mProviderName; 42 private ContentObserverProxy mObserver; 43 44 /** 45 * The cursor that is being adapted. 46 * This field is set to null when the cursor is closed. 47 */ 48 private CrossProcessCursor mCursor; 49 50 /** 51 * The cursor window that was filled by the cross process cursor in the 52 * case where the cursor does not support getWindow. 53 * This field is only ever non-null when the window has actually be filled. 54 */ 55 private CursorWindow mFilledWindow; 56 57 private static final class ContentObserverProxy extends ContentObserver { 58 protected IContentObserver mRemote; 59 60 public ContentObserverProxy(IContentObserver remoteObserver, DeathRecipient recipient) { 61 super(null); 62 mRemote = remoteObserver; 63 try { 64 remoteObserver.asBinder().linkToDeath(recipient, 0); 65 } catch (RemoteException e) { 66 // Do nothing, the far side is dead 67 } 68 } 69 70 public boolean unlinkToDeath(DeathRecipient recipient) { 71 return mRemote.asBinder().unlinkToDeath(recipient, 0); 72 } 73 74 @Override 75 public boolean deliverSelfNotifications() { 76 // The far side handles the self notifications. 77 return false; 78 } 79 80 @Override 81 public void onChange(boolean selfChange) { 82 try { 83 mRemote.onChange(selfChange); 84 } catch (RemoteException ex) { 85 // Do nothing, the far side is dead 86 } 87 } 88 } 89 90 public CursorToBulkCursorAdaptor(Cursor cursor, IContentObserver observer, 91 String providerName) { 92 if (cursor instanceof CrossProcessCursor) { 93 mCursor = (CrossProcessCursor)cursor; 94 } else { 95 mCursor = new CrossProcessCursorWrapper(cursor); 96 } 97 mProviderName = providerName; 98 99 synchronized (mLock) { 100 createAndRegisterObserverProxyLocked(observer); 101 } 102 } 103 104 private void closeFilledWindowLocked() { 105 if (mFilledWindow != null) { 106 mFilledWindow.close(); 107 mFilledWindow = null; 108 } 109 } 110 111 private void disposeLocked() { 112 if (mCursor != null) { 113 unregisterObserverProxyLocked(); 114 mCursor.close(); 115 mCursor = null; 116 } 117 118 closeFilledWindowLocked(); 119 } 120 121 private void throwIfCursorIsClosed() { 122 if (mCursor == null) { 123 throw new StaleDataException("Attempted to access a cursor after it has been closed."); 124 } 125 } 126 127 @Override 128 public void binderDied() { 129 synchronized (mLock) { 130 disposeLocked(); 131 } 132 } 133 134 @Override 135 public CursorWindow getWindow(int startPos) { 136 synchronized (mLock) { 137 throwIfCursorIsClosed(); 138 139 if (!mCursor.moveToPosition(startPos)) { 140 closeFilledWindowLocked(); 141 return null; 142 } 143 144 CursorWindow window = mCursor.getWindow(); 145 if (window != null) { 146 closeFilledWindowLocked(); 147 } else { 148 window = mFilledWindow; 149 if (window == null) { 150 mFilledWindow = new CursorWindow(mProviderName); 151 window = mFilledWindow; 152 mCursor.fillWindow(startPos, window); 153 } else if (startPos < window.getStartPosition() 154 || startPos >= window.getStartPosition() + window.getNumRows()) { 155 window.clear(); 156 mCursor.fillWindow(startPos, window); 157 } 158 } 159 160 // Acquire a reference before returning from this RPC. 161 // The Binder proxy will decrement the reference count again as part of writing 162 // the CursorWindow to the reply parcel as a return value. 163 if (window != null) { 164 window.acquireReference(); 165 } 166 return window; 167 } 168 } 169 170 @Override 171 public void onMove(int position) { 172 synchronized (mLock) { 173 throwIfCursorIsClosed(); 174 175 mCursor.onMove(mCursor.getPosition(), position); 176 } 177 } 178 179 @Override 180 public int count() { 181 synchronized (mLock) { 182 throwIfCursorIsClosed(); 183 184 return mCursor.getCount(); 185 } 186 } 187 188 @Override 189 public String[] getColumnNames() { 190 synchronized (mLock) { 191 throwIfCursorIsClosed(); 192 193 return mCursor.getColumnNames(); 194 } 195 } 196 197 @Override 198 public void deactivate() { 199 synchronized (mLock) { 200 if (mCursor != null) { 201 unregisterObserverProxyLocked(); 202 mCursor.deactivate(); 203 } 204 205 closeFilledWindowLocked(); 206 } 207 } 208 209 @Override 210 public void close() { 211 synchronized (mLock) { 212 disposeLocked(); 213 } 214 } 215 216 @Override 217 public int requery(IContentObserver observer) { 218 synchronized (mLock) { 219 throwIfCursorIsClosed(); 220 221 closeFilledWindowLocked(); 222 223 try { 224 if (!mCursor.requery()) { 225 return -1; 226 } 227 } catch (IllegalStateException e) { 228 IllegalStateException leakProgram = new IllegalStateException( 229 mProviderName + " Requery misuse db, mCursor isClosed:" + 230 mCursor.isClosed(), e); 231 throw leakProgram; 232 } 233 234 unregisterObserverProxyLocked(); 235 createAndRegisterObserverProxyLocked(observer); 236 return mCursor.getCount(); 237 } 238 } 239 240 @Override 241 public boolean getWantsAllOnMoveCalls() { 242 synchronized (mLock) { 243 throwIfCursorIsClosed(); 244 245 return mCursor.getWantsAllOnMoveCalls(); 246 } 247 } 248 249 /** 250 * Create a ContentObserver from the observer and register it as an observer on the 251 * underlying cursor. 252 * @param observer the IContentObserver that wants to monitor the cursor 253 * @throws IllegalStateException if an observer is already registered 254 */ 255 private void createAndRegisterObserverProxyLocked(IContentObserver observer) { 256 if (mObserver != null) { 257 throw new IllegalStateException("an observer is already registered"); 258 } 259 mObserver = new ContentObserverProxy(observer, this); 260 mCursor.registerContentObserver(mObserver); 261 } 262 263 /** Unregister the observer if it is already registered. */ 264 private void unregisterObserverProxyLocked() { 265 if (mObserver != null) { 266 mCursor.unregisterContentObserver(mObserver); 267 mObserver.unlinkToDeath(this); 268 mObserver = null; 269 } 270 } 271 272 @Override 273 public Bundle getExtras() { 274 synchronized (mLock) { 275 throwIfCursorIsClosed(); 276 277 return mCursor.getExtras(); 278 } 279 } 280 281 @Override 282 public Bundle respond(Bundle extras) { 283 synchronized (mLock) { 284 throwIfCursorIsClosed(); 285 286 return mCursor.respond(extras); 287 } 288 } 289} 290