Hans Boehm | 8f051c3 | 2016-10-03 16:53:58 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2016 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 | // FIXME: We need to rethink the error handling here. Do we want to revert to history-less |
| 18 | // operation if something goes wrong with the database? |
| 19 | // TODO: This tries to ensure strong thread-safety, i.e. each call looks atomic, both to |
| 20 | // other threads and other database users. Is this useful? |
| 21 | // TODO: Especially if we notice serious performance issues on rotation in the history |
| 22 | // view, we may need to use a CursorLoader or some other scheme to preserve the database |
| 23 | // across rotations. |
| 24 | |
| 25 | package com.android.calculator2; |
| 26 | |
| 27 | import android.content.ContentValues; |
| 28 | import android.content.Context; |
| 29 | import android.database.Cursor; |
| 30 | import android.database.sqlite.SQLiteDatabase; |
| 31 | import android.database.sqlite.SQLiteException; |
| 32 | import android.database.sqlite.SQLiteOpenHelper; |
| 33 | import android.os.AsyncTask; |
| 34 | import android.provider.BaseColumns; |
| 35 | import android.util.Log; |
| 36 | |
| 37 | import java.util.Calendar; |
| 38 | import java.util.TimeZone; |
| 39 | |
| 40 | public class ExpressionDB { |
| 41 | /* Table contents */ |
| 42 | public static class ExpressionEntry implements BaseColumns { |
| 43 | public static final String TABLE_NAME = "expressions"; |
| 44 | public static final String COLUMN_NAME_EXPRESSION = "expression"; |
| 45 | public static final String COLUMN_NAME_FLAGS = "flags"; |
| 46 | // Time stamp as returned by currentTimeMillis(). |
| 47 | public static final String COLUMN_NAME_TIMESTAMP = "timeStamp"; |
| 48 | // UTC offset at the locale when the expression was saved. In multiples of 15 minutes. |
| 49 | public static final String COLUMN_NAME_COMPRESSED_UTC_OFFSET = "compressedUtcOffset"; |
| 50 | } |
| 51 | |
| 52 | /* Data to be written to or read from a row in the table */ |
| 53 | public static class RowData { |
| 54 | private static final int DEGREE_MODE = 2; |
| 55 | private static final int LONG_TIMEOUT = 1; |
| 56 | public final byte[] mExpression; |
| 57 | public final int mFlags; |
| 58 | public long mTimeStamp; // 0 ==> this and next field to be filled in when written. |
| 59 | public byte mCompressedUtcOffset; // multiples of 15 minutes. |
| 60 | private static int flagsFromDegreeAndTimeout(Boolean DegreeMode, Boolean LongTimeout) { |
| 61 | return (DegreeMode ? DEGREE_MODE : 0) | (LongTimeout ? LONG_TIMEOUT : 0); |
| 62 | } |
| 63 | private boolean degreeModeFromFlags(int flags) { |
| 64 | return (flags & DEGREE_MODE) != 0; |
| 65 | } |
| 66 | private boolean longTimeoutFromFlags(int flags) { |
| 67 | return (flags & LONG_TIMEOUT) != 0; |
| 68 | } |
| 69 | private static final int MILLIS_IN_15_MINS = 15 * 60 * 1000; |
| 70 | private static byte compressUtcOffset(int utcOffsetMillis) { |
| 71 | // Rounded division, though it shouldn't really matter. |
| 72 | if (utcOffsetMillis > 0) { |
| 73 | return (byte) ((utcOffsetMillis + MILLIS_IN_15_MINS / 2) / MILLIS_IN_15_MINS); |
| 74 | } else { |
| 75 | return (byte) ((utcOffsetMillis - MILLIS_IN_15_MINS / 2) / MILLIS_IN_15_MINS); |
| 76 | } |
| 77 | } |
| 78 | private static int uncompressUtcOffset(byte compressedUtcOffset) { |
| 79 | return MILLIS_IN_15_MINS * (int)compressedUtcOffset; |
| 80 | } |
| 81 | private RowData(byte[] expr, int flags, long timeStamp, byte compressedUtcOffset) { |
| 82 | mExpression = expr; |
| 83 | mFlags = flags; |
| 84 | mTimeStamp = timeStamp; |
| 85 | mCompressedUtcOffset = compressedUtcOffset; |
| 86 | } |
| 87 | /** |
| 88 | * More client-friendly constructor that hides implementation ugliness. |
| 89 | * utcOffset here is uncompressed, in milliseconds. |
| 90 | * A zero timestamp will cause it to be automatically filled in. |
| 91 | */ |
| 92 | public RowData(byte[] expr, boolean degreeMode, boolean longTimeout, long timeStamp, |
| 93 | int utcOffset) { |
| 94 | this(expr, flagsFromDegreeAndTimeout(degreeMode, longTimeout), timeStamp, |
| 95 | compressUtcOffset(utcOffset)); |
| 96 | } |
| 97 | public boolean degreeMode() { |
| 98 | return degreeModeFromFlags(mFlags); |
| 99 | } |
| 100 | public boolean longTimeout() { |
| 101 | return longTimeoutFromFlags(mFlags); |
| 102 | } |
| 103 | /** |
| 104 | * Return UTC offset for timestamp in milliseconds. |
| 105 | */ |
| 106 | public int utcOffset() { |
| 107 | return uncompressUtcOffset(mCompressedUtcOffset); |
| 108 | } |
| 109 | /** |
| 110 | * Return a ContentValues object representing the current data. |
| 111 | */ |
| 112 | public ContentValues toContentValues() { |
| 113 | ContentValues cvs = new ContentValues(); |
| 114 | cvs.put(ExpressionEntry.COLUMN_NAME_EXPRESSION, mExpression); |
| 115 | cvs.put(ExpressionEntry.COLUMN_NAME_FLAGS, mFlags); |
| 116 | if (mTimeStamp == 0) { |
| 117 | mTimeStamp = System.currentTimeMillis(); |
| 118 | final TimeZone timeZone = Calendar.getInstance().getTimeZone(); |
| 119 | mCompressedUtcOffset = compressUtcOffset(timeZone.getOffset(mTimeStamp)); |
| 120 | } |
| 121 | cvs.put(ExpressionEntry.COLUMN_NAME_TIMESTAMP, mTimeStamp); |
| 122 | cvs.put(ExpressionEntry.COLUMN_NAME_COMPRESSED_UTC_OFFSET, mCompressedUtcOffset); |
| 123 | return cvs; |
| 124 | } |
| 125 | } |
| 126 | |
| 127 | private static final String SQL_CREATE_ENTRIES = |
| 128 | "CREATE TABLE " + ExpressionEntry.TABLE_NAME + " (" + |
| 129 | ExpressionEntry._ID + " INTEGER PRIMARY KEY," + |
| 130 | ExpressionEntry.COLUMN_NAME_EXPRESSION + " BLOB," + |
| 131 | ExpressionEntry.COLUMN_NAME_FLAGS + " INTEGER," + |
| 132 | ExpressionEntry.COLUMN_NAME_TIMESTAMP + " INTEGER," + |
| 133 | ExpressionEntry.COLUMN_NAME_COMPRESSED_UTC_OFFSET + " INTEGER)"; |
| 134 | private static final String SQL_DELETE_ENTRIES = |
| 135 | "DROP TABLE IF EXISTS " + ExpressionEntry.TABLE_NAME; |
| 136 | private static final String SQL_GET_MIN = "SELECT MIN(" + ExpressionEntry._ID + |
| 137 | ") FROM " + ExpressionEntry.TABLE_NAME; |
| 138 | private static final String SQL_GET_MAX = "SELECT MAX(" + ExpressionEntry._ID + |
| 139 | ") FROM " + ExpressionEntry.TABLE_NAME; |
| 140 | private static final String SQL_GET_ROW = "SELECT * FROM " + ExpressionEntry.TABLE_NAME + |
| 141 | " WHERE " + ExpressionEntry._ID + " = ?"; |
| 142 | |
| 143 | private class ExpressionDBHelper extends SQLiteOpenHelper { |
| 144 | // If you change the database schema, you must increment the database version. |
| 145 | public static final int DATABASE_VERSION = 1; |
| 146 | public static final String DATABASE_NAME = "Expressions.db"; |
| 147 | |
| 148 | public ExpressionDBHelper(Context context) { |
| 149 | super(context, DATABASE_NAME, null, DATABASE_VERSION); |
| 150 | } |
| 151 | public void onCreate(SQLiteDatabase db) { |
| 152 | db.execSQL(SQL_CREATE_ENTRIES); |
| 153 | } |
| 154 | public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { |
| 155 | // For now just throw away history on database version upgrade/downgrade. |
| 156 | db.execSQL(SQL_DELETE_ENTRIES); |
| 157 | onCreate(db); |
| 158 | } |
| 159 | public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) { |
| 160 | onUpgrade(db, oldVersion, newVersion); |
| 161 | } |
| 162 | } |
| 163 | |
| 164 | private ExpressionDBHelper mExpressionDBHelper; |
| 165 | |
| 166 | private SQLiteDatabase mExpressionDB; // Constant after initialization. |
| 167 | |
| 168 | private boolean mBadDB = false; // Database initialization failed. |
| 169 | |
| 170 | // Never allocate new negative indicees (row ids) >= MAXIMUM_MIN_INDEX. |
| 171 | public static final long MAXIMUM_MIN_INDEX = -10; |
| 172 | |
| 173 | // Minimum index value in DB. |
| 174 | private long mMinIndex; |
| 175 | // Maximum index value in DB. |
| 176 | private long mMaxIndex; |
| 177 | // mMinIndex and mMaxIndex are correct. |
| 178 | private boolean mMinMaxValid; |
| 179 | |
| 180 | // mLock protects mExpressionDB and mBadDB, though we access mExpressionDB without |
| 181 | // synchronization after it's known to be initialized. Used to wait for database |
| 182 | // initialization. Also protects mMinIndex, mMaxIndex, and mMinMaxValid. |
| 183 | private Object mLock = new Object(); |
| 184 | |
| 185 | public ExpressionDB(Context context) { |
| 186 | mExpressionDBHelper = new ExpressionDBHelper(context); |
| 187 | AsyncInitializer initializer = new AsyncInitializer(); |
| 188 | initializer.execute(mExpressionDBHelper); |
| 189 | } |
| 190 | |
| 191 | private boolean getBadDB() { |
| 192 | synchronized(mLock) { |
| 193 | return mBadDB; |
| 194 | } |
| 195 | } |
| 196 | |
| 197 | private void setBadDB() { |
| 198 | synchronized(mLock) { |
| 199 | mBadDB = true; |
| 200 | } |
| 201 | } |
| 202 | |
| 203 | /** |
| 204 | * Set mExpressionDB and compute minimum and maximum indices in the background. |
| 205 | */ |
| 206 | private class AsyncInitializer extends AsyncTask<ExpressionDBHelper, Void, SQLiteDatabase> { |
| 207 | @Override |
| 208 | protected SQLiteDatabase doInBackground(ExpressionDBHelper... helper) { |
| 209 | SQLiteDatabase result; |
| 210 | try { |
| 211 | result = helper[0].getWritableDatabase(); |
| 212 | // We notify here, since there are unlikely cases in which the UI thread |
| 213 | // may be blocked on us, preventing onPostExecute from running. |
| 214 | synchronized(mLock) { |
| 215 | mExpressionDB = result; |
| 216 | mLock.notifyAll(); |
| 217 | } |
| 218 | long min, max; |
| 219 | try (Cursor minResult = result.rawQuery(SQL_GET_MIN, null)) { |
| 220 | if (!minResult.moveToFirst()) { |
| 221 | // Empty database. |
| 222 | min = MAXIMUM_MIN_INDEX; |
| 223 | } else { |
| 224 | min = Math.min(minResult.getLong(0), MAXIMUM_MIN_INDEX); |
| 225 | } |
| 226 | } |
| 227 | try (Cursor maxResult = result.rawQuery(SQL_GET_MAX, null)) { |
| 228 | if (!maxResult.moveToFirst()) { |
| 229 | // Empty database. |
| 230 | max = 0L; |
| 231 | } else { |
| 232 | max = Math.max(maxResult.getLong(0), 0L); |
| 233 | } |
| 234 | } |
| 235 | synchronized(mLock) { |
| 236 | mMinIndex = min; |
| 237 | mMaxIndex = max; |
| 238 | mMinMaxValid = true; |
| 239 | mLock.notifyAll(); |
| 240 | } |
| 241 | } catch(SQLiteException e) { |
| 242 | Log.e("Calculator", "Database initialization failed.\n", e); |
| 243 | synchronized(mLock) { |
| 244 | mBadDB = true; |
| 245 | mLock.notifyAll(); |
| 246 | } |
| 247 | return null; |
| 248 | } |
| 249 | return result; |
| 250 | } |
| 251 | |
| 252 | @Override |
| 253 | protected void onPostExecute(SQLiteDatabase result) { |
| 254 | if (result == null) { |
| 255 | throw new AssertionError("Failed to open history DB"); |
| 256 | // TODO: Should we try to run without persistent history instead? |
| 257 | } // else doInBackground already set expressionDB. |
| 258 | } |
| 259 | // On cancellation we do nothing; |
| 260 | } |
| 261 | |
| 262 | /** |
| 263 | * Wait until expression DB is ready. |
| 264 | * This should usually be a no-op, since we set up the DB on creation. But there are a few |
| 265 | * cases, such as restarting the calculator in history mode, when we currently can't do |
| 266 | * anything but wait, possibly even in the UI thread. |
| 267 | */ |
| 268 | private void waitForExpressionDB() { |
| 269 | synchronized(mLock) { |
| 270 | while (mExpressionDB == null && !mBadDB) { |
| 271 | try { |
| 272 | mLock.wait(); |
| 273 | } catch(InterruptedException e) { |
| 274 | mBadDB = true; |
| 275 | } |
| 276 | } |
| 277 | if (mBadDB) { |
| 278 | throw new AssertionError("Failed to open history DB"); |
| 279 | } |
| 280 | } |
| 281 | } |
| 282 | |
| 283 | /** |
| 284 | * Wait until the minimum key has been computed. |
| 285 | */ |
| 286 | private void waitForMinMaxValid() { |
| 287 | synchronized(mLock) { |
| 288 | while (!mMinMaxValid && !mBadDB) { |
| 289 | try { |
| 290 | mLock.wait(); |
| 291 | } catch(InterruptedException e) { |
| 292 | mBadDB = true; |
| 293 | } |
| 294 | } |
| 295 | if (mBadDB) { |
| 296 | throw new AssertionError("Failed to compute minimum key"); |
| 297 | } |
| 298 | } |
| 299 | } |
| 300 | |
| 301 | public synchronized void eraseAll() { |
| 302 | waitForExpressionDB(); |
| 303 | mExpressionDB.execSQL("SQL_DELETE_ENTRIES"); |
| 304 | try { |
| 305 | mExpressionDB.execSQL("VACUUM"); |
| 306 | } catch(Exception e) { |
| 307 | Log.v("Calculator", "Database VACUUM failed\n", e); |
| 308 | // FIXME: probably needed only if there is danger of concurrent execution. |
| 309 | } |
| 310 | } |
| 311 | |
| 312 | /** |
| 313 | * Update a row in place. |
| 314 | * Currently unused, since only the main expression is updated in place, and we |
| 315 | * don't save that in the DB. |
| 316 | */ |
| 317 | public void updateRow(long index, RowData data) { |
| 318 | if (index == -1) { |
| 319 | setBadDB(); |
| 320 | throw new AssertionError("Can't insert row index of -1"); |
| 321 | } |
| 322 | ContentValues cvs = data.toContentValues(); |
| 323 | cvs.put(ExpressionEntry._ID, index); |
| 324 | waitForExpressionDB(); |
| 325 | long result = mExpressionDB.replace(ExpressionEntry.TABLE_NAME, null, cvs); |
| 326 | if (result == -1) { |
| 327 | throw new AssertionError("Row update failed"); |
| 328 | } |
| 329 | } |
| 330 | |
| 331 | /** |
| 332 | * Add a row with index outside existing range. |
| 333 | * The returned index will be larger than any existing index unless negative_index is true. |
| 334 | * In that case it will be smaller than any existing index and smaller than MAXIMUM_MIN_INDEX. |
| 335 | */ |
| 336 | public long addRow(boolean negative_index, RowData data) { |
| 337 | long result; |
| 338 | long newIndex; |
| 339 | waitForMinMaxValid(); |
| 340 | synchronized(mLock) { |
| 341 | if (negative_index) { |
| 342 | newIndex = mMinIndex - 1; |
| 343 | mMinIndex = newIndex; |
| 344 | } else { |
| 345 | newIndex = mMaxIndex + 1; |
| 346 | mMaxIndex = newIndex; |
| 347 | } |
| 348 | ContentValues cvs = data.toContentValues(); |
| 349 | cvs.put(ExpressionEntry._ID, newIndex); |
| 350 | result = mExpressionDB.insert(ExpressionEntry.TABLE_NAME, null, cvs); |
| 351 | } |
| 352 | if (result != newIndex) { |
| 353 | throw new AssertionError("Expected row id " + newIndex + ", got " + result); |
| 354 | } |
| 355 | return result; |
| 356 | } |
| 357 | |
| 358 | /** |
| 359 | * Retrieve the row with the given index. |
| 360 | * Such a row must exist. |
| 361 | */ |
| 362 | public RowData getRow(long index) { |
| 363 | RowData result; |
| 364 | waitForExpressionDB(); |
| 365 | String args[] = new String[] { Long.toString(index) }; |
| 366 | Cursor resultC = mExpressionDB.rawQuery(SQL_GET_ROW, args); |
| 367 | if (!resultC.moveToFirst()) { |
| 368 | throw new AssertionError("Missing Row"); |
| 369 | } else { |
| 370 | result = new RowData(resultC.getBlob(1), resultC.getInt(2) /* flags */, |
| 371 | resultC.getLong(3) /* timestamp */, (byte)resultC.getInt(4) /* UTC offset */); |
| 372 | } |
| 373 | return result; |
| 374 | } |
| 375 | |
| 376 | public long getMinIndex() { |
| 377 | waitForMinMaxValid(); |
| 378 | synchronized(mLock) { |
| 379 | return mMinIndex; |
| 380 | } |
| 381 | } |
| 382 | |
| 383 | public long getMaxIndex() { |
| 384 | waitForMinMaxValid(); |
| 385 | synchronized(mLock) { |
| 386 | return mMaxIndex; |
| 387 | } |
| 388 | } |
| 389 | |
| 390 | public void close() { |
| 391 | mExpressionDBHelper.close(); |
| 392 | } |
| 393 | |
| 394 | } |