content: /*
   * Copyright (C) 2011 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package android.database.sqlite;
  
  import android.annotation.TestApi;
  import android.content.res.Resources;
  import android.os.StatFs;
  import android.os.SystemProperties;
  
  /**
   * Provides access to SQLite functions that affect all database connection,
   * such as memory management.
   *
   * The native code associated with SQLiteGlobal is also sets global configuration options
   * using sqlite3_config() then calls sqlite3_initialize() to ensure that the SQLite
   * library is properly initialized exactly once before any other framework or application
   * code has a chance to run.
   *
   * Verbose SQLite logging is enabled if the "log.tag.SQLiteLog" property is set to "V".
   * (per {@link SQLiteDebug#DEBUG_SQL_LOG}).
   *
   * @hide
   */
  @TestApi
  public final class SQLiteGlobal {
      private static final String TAG = "SQLiteGlobal";
  
      /** @hide */
      public static final String SYNC_MODE_FULL = "FULL";
  
      /** @hide */
      static final String WIPE_CHECK_FILE_SUFFIX = "-wipecheck";
  
      private static final Object sLock = new Object();
  
      private static int sDefaultPageSize;
  
      private static native int nativeReleaseMemory();
  
      /** @hide */
      public static volatile String sDefaultSyncMode;
  
      private SQLiteGlobal() {
      }
  
      /**
       * Attempts to release memory by pruning the SQLite page cache and other
       * internal data structures.
       *
       * @return The number of bytes that were freed.
       */
      public static int releaseMemory() {
          return nativeReleaseMemory();
      }
  
      /**
       * Gets the default page size to use when creating a database.
       */
      public static int getDefaultPageSize() {
          synchronized (sLock) {
              if (sDefaultPageSize == 0) {
                  // If there is an issue accessing /data, something is so seriously
                  // wrong that we just let the IllegalArgumentException propagate.
                  sDefaultPageSize = new StatFs("/data").getBlockSize();
              }
              return SystemProperties.getInt("debug.sqlite.pagesize", sDefaultPageSize);
          }
      }
  
      /**
       * Gets the default journal mode when WAL is not in use.
       */
      public static String getDefaultJournalMode() {
          return SystemProperties.get("debug.sqlite.journalmode",
                  Resources.getSystem().getString(
                  com.android.internal.R.string.db_default_journal_mode));
      }
  
      /**
       * Gets the journal size limit in bytes.
       */
      public static int getJournalSizeLimit() {
          return SystemProperties.getInt("debug.sqlite.journalsizelimit",
                  Resources.getSystem().getInteger(
                  com.android.internal.R.integer.db_journal_size_limit));
      }
  
      /**
       * Gets the default database synchronization mode when WAL is not in use.
       */
      public static String getDefaultSyncMode() {
          // Use the FULL synchronous mode for system processes by default.
          String defaultMode = sDefaultSyncMode;
          if (defaultMode != null) {
              return defaultMode;
          }
          return SystemProperties.get("debug.sqlite.syncmode",
                  Resources.getSystem().getString(
                  com.android.internal.R.string.db_default_sync_mode));
      }
  
      /**
       * Gets the database synchronization mode when in WAL mode.
       */
      public static String getWALSyncMode() {
          // Use the FULL synchronous mode for system processes by default.
          String defaultMode = sDefaultSyncMode;
          if (defaultMode != null) {
              return defaultMode;
          }
          return SystemProperties.get("debug.sqlite.wal.syncmode",
                  Resources.getSystem().getString(
                  com.android.internal.R.string.db_wal_sync_mode));
      }
  
      /**
       * Gets the WAL auto-checkpoint integer in database pages.
       */
      public static int getWALAutoCheckpoint() {
          int value = SystemProperties.getInt("debug.sqlite.wal.autocheckpoint",
                  Resources.getSystem().getInteger(
                  com.android.internal.R.integer.db_wal_autocheckpoint));
          return Math.max(1, value);
      }
  
      /**
       * Gets the connection pool size when in WAL mode.
       */
      public static int getWALConnectionPoolSize() {
          int value = SystemProperties.getInt("debug.sqlite.wal.poolsize",
                  Resources.getSystem().getInteger(
                  com.android.internal.R.integer.db_connection_pool_size));
          return Math.max(2, value);
      }
  
      /**
       * The default number of milliseconds that SQLite connection is allowed to be idle before it
       * is closed and removed from the pool.
       */
      public static int getIdleConnectionTimeout() {
          return SystemProperties.getInt("debug.sqlite.idle_connection_timeout",
                  Resources.getSystem().getInteger(
                          com.android.internal.R.integer.db_default_idle_connection_timeout));
      }
  
      /**
       * When opening a database, if the WAL file is larger than this size, we'll truncate it.
       *
       * (If it's 0, we do not truncate.)
       *
       * @hide
       */
      public static long getWALTruncateSize() {
          final long setting = SQLiteCompatibilityWalFlags.getTruncateSize();
          if (setting >= 0) {
              return setting;
          }
          return SystemProperties.getInt("debug.sqlite.wal.truncatesize",
                  Resources.getSystem().getInteger(
                          com.android.internal.R.integer.db_wal_truncate_size));
      }
  
      /** @hide */
      public static boolean checkDbWipe() {
          return false;
      }
  }
  