The Tor Browser: mobile/android/base/db/AbstractTransactionalProvider.java@6474c204b198 (annotated)

mobile/android/base/db/AbstractTransactionalProvider.java@6474c204b198 (annotated)

mobile/android/base/db/AbstractTransactionalProvider.java

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 package org.mozilla.gecko.db;
 import android.content.ContentProvider;
 import android.content.ContentValues;
 import android.database.Cursor;
 import android.database.SQLException;
 import android.database.sqlite.SQLiteDatabase;
 import android.net.Uri;
 import android.os.Build;
 import android.text.TextUtils;
 import android.util.Log;
 /**
  * This abstract class exists to capture some of the transaction-handling
  * commonalities in Fennec's DB layer.
  *
  * In particular, this abstracts DB access, batching, and a particular
  * transaction approach.
  *
  * That approach is: subclasses implement the abstract methods
  * {@link #insertInTransaction(android.net.Uri, android.content.ContentValues)},
  * {@link #deleteInTransaction(android.net.Uri, String, String[])}, and
  * {@link #updateInTransaction(android.net.Uri, android.content.ContentValues, String, String[])}.
  *
  * These are all called expecting a transaction to be established, so failed
  * modifications can be rolled-back, and work batched.
  *
  * If no transaction is established, that's not a problem. Transaction nesting
  * can be avoided by using {@link #beginWrite(SQLiteDatabase)}.
  *
  * The decision of when to begin a transaction is left to the subclasses,
  * primarily to avoid the pattern of a transaction being begun, a read occurring,
  * and then a write being necessary. This lock upgrade can result in SQLITE_BUSY,
  * which we don't handle well. Better to avoid starting a transaction too soon!
  *
  * You are probably interested in some subclasses:
  *
  * * {@link AbstractPerProfileDatabaseProvider} provides a simple abstraction for
  *   querying databases that are stored in the user's profile directory.
  * * {@link PerProfileDatabaseProvider} is a simple version that only allows a
  *   single ContentProvider to access each per-profile database.
  * * {@link SharedBrowserDatabaseProvider} is an example of a per-profile provider
  *   that allows for multiple providers to safely work with the same databases.
  */
 @SuppressWarnings("javadoc")
 public abstract class AbstractTransactionalProvider extends ContentProvider {
     private static final String LOGTAG = "GeckoTransProvider";
     private static boolean logDebug = Log.isLoggable(LOGTAG, Log.DEBUG);
     private static boolean logVerbose = Log.isLoggable(LOGTAG, Log.VERBOSE);
     protected abstract SQLiteDatabase getReadableDatabase(Uri uri);
     protected abstract SQLiteDatabase getWritableDatabase(Uri uri);
     public abstract SQLiteDatabase getWritableDatabaseForTesting(Uri uri);
     protected abstract Uri insertInTransaction(Uri uri, ContentValues values);
     protected abstract int deleteInTransaction(Uri uri, String selection, String[] selectionArgs);
     protected abstract int updateInTransaction(Uri uri, ContentValues values, String selection, String[] selectionArgs);
     /**
      * Track whether we're in a batch operation.
      *
      * When we're in a batch operation, individual write steps won't even try
      * to start a transaction... and neither will they attempt to finish one.
      *
      * Set this to <code>Boolean.TRUE</code> when you're entering a batch --
      * a section of code in which {@link ContentProvider} methods will be
      * called, but nested transactions should not be started. Callers are
      * responsible for beginning and ending the enclosing transaction, and
      * for setting this to <code>Boolean.FALSE</code> when done.
      *
      * This is a ThreadLocal separate from `db.inTransaction` because batched
      * operations start transactions independent of individual ContentProvider
      * operations. This doesn't work well with the entire concept of this
      * abstract class -- that is, automatically beginning and ending transactions
      * for each insert/delete/update operation -- and doing so without
      * causing arbitrary nesting requires external tracking.
      *
      * Note that beginWrite takes a DB argument, but we don't differentiate
      * between databases in this tracking flag. If your ContentProvider manages
      * multiple database transactions within the same thread, you'll need to
      * amend this scheme -- but then, you're already doing some serious wizardry,
      * so rock on.
      */
     final ThreadLocal<Boolean> isInBatchOperation = new ThreadLocal<Boolean>();
     /**
      * Return true if OS version and database parallelism support indicates
      * that this provider should bundle writes into transactions.
      */
     @SuppressWarnings("static-method")
     protected boolean shouldUseTransactions() {
         return Build.VERSION.SDK_INT >= 11;
     }
     protected static String computeSQLInClause(int items, String field) {
         final StringBuilder builder = new StringBuilder(field);
         builder.append(" IN (");
         int i = 0;
         for (; i < items - 1; ++i) {
             builder.append("?, ");
         }
         if (i < items) {
             builder.append("?");
         }
         builder.append(")");
         return builder.toString();
     }
     private boolean isInBatch() {
         final Boolean isInBatch = isInBatchOperation.get();
         if (isInBatch == null) {
             return false;
         }
         return isInBatch.booleanValue();
     }
     /**
      * If we're not currently in a transaction, and we should be, start one.
      */
     protected void beginWrite(final SQLiteDatabase db) {
         if (isInBatch()) {
             trace("Not bothering with an intermediate write transaction: inside batch operation.");
             return;
         }
         if (shouldUseTransactions() && !db.inTransaction()) {
             trace("beginWrite: beginning transaction.");
             db.beginTransaction();
         }
     }
     /**
      * If we're not in a batch, but we are in a write transaction, mark it as
      * successful.
      */
     protected void markWriteSuccessful(final SQLiteDatabase db) {
         if (isInBatch()) {
             trace("Not marking write successful: inside batch operation.");
             return;
         }
         if (shouldUseTransactions() && db.inTransaction()) {
             trace("Marking write transaction successful.");
             db.setTransactionSuccessful();
         }
     }
     /**
      * If we're not in a batch, but we are in a write transaction,
      * end it.
      *
      * @see PerProfileDatabaseProvider#markWriteSuccessful(SQLiteDatabase)
      */
     protected void endWrite(final SQLiteDatabase db) {
         if (isInBatch()) {
             trace("Not ending write: inside batch operation.");
             return;
         }
         if (shouldUseTransactions() && db.inTransaction()) {
             trace("endWrite: ending transaction.");
             db.endTransaction();
         }
     }
     protected void beginBatch(final SQLiteDatabase db) {
         trace("Beginning batch.");
         isInBatchOperation.set(Boolean.TRUE);
         db.beginTransaction();
     }
     protected void markBatchSuccessful(final SQLiteDatabase db) {
         if (isInBatch()) {
             trace("Marking batch successful.");
             db.setTransactionSuccessful();
             return;
         }
         Log.w(LOGTAG, "Unexpectedly asked to mark batch successful, but not in batch!");
         throw new IllegalStateException("Not in batch.");
     }
     protected void endBatch(final SQLiteDatabase db) {
         trace("Ending batch.");
         db.endTransaction();
         isInBatchOperation.set(Boolean.FALSE);
     }
     /**
      * Turn a single-column cursor of longs into a single SQL "IN" clause.
      * We can do this without using selection arguments because Long isn't
      * vulnerable to injection.
      */
     protected static String computeSQLInClauseFromLongs(final Cursor cursor, String field) {
         final StringBuilder builder = new StringBuilder(field);
         builder.append(" IN (");
         final int commaLimit = cursor.getCount() - 1;
         int i = 0;
         while (cursor.moveToNext()) {
             builder.append(cursor.getLong(0));
             if (i++ < commaLimit) {
                 builder.append(", ");
             }
         }
         builder.append(")");
         return builder.toString();
     }
     @Override
     public int delete(Uri uri, String selection, String[] selectionArgs) {
         trace("Calling delete on URI: " + uri + ", " + selection + ", " + selectionArgs);
         final SQLiteDatabase db = getWritableDatabase(uri);
         int deleted = 0;
         try {
             deleted = deleteInTransaction(uri, selection, selectionArgs);
             markWriteSuccessful(db);
         } finally {
             endWrite(db);
         }
         if (deleted > 0) {
             final boolean shouldSyncToNetwork = !isCallerSync(uri);
             getContext().getContentResolver().notifyChange(uri, null, shouldSyncToNetwork);
         }
         return deleted;
     }
     @Override
     public Uri insert(Uri uri, ContentValues values) {
         trace("Calling insert on URI: " + uri);
         final SQLiteDatabase db = getWritableDatabase(uri);
         Uri result = null;
         try {
             result = insertInTransaction(uri, values);
             markWriteSuccessful(db);
         } catch (SQLException sqle) {
             Log.e(LOGTAG, "exception in DB operation", sqle);
         } catch (UnsupportedOperationException uoe) {
             Log.e(LOGTAG, "don't know how to perform that insert", uoe);
         } finally {
             endWrite(db);
         }
         if (result != null) {
             final boolean shouldSyncToNetwork = !isCallerSync(uri);
             getContext().getContentResolver().notifyChange(uri, null, shouldSyncToNetwork);
         }
         return result;
     }
     @Override
     public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
         trace("Calling update on URI: " + uri + ", " + selection + ", " + selectionArgs);
         final SQLiteDatabase db = getWritableDatabase(uri);
         int updated = 0;
         try {
             updated = updateInTransaction(uri, values, selection,
                                           selectionArgs);
             markWriteSuccessful(db);
         } finally {
             endWrite(db);
         }
         if (updated > 0) {
             final boolean shouldSyncToNetwork = !isCallerSync(uri);
             getContext().getContentResolver().notifyChange(uri, null, shouldSyncToNetwork);
         }
         return updated;
     }
     @Override
     public int bulkInsert(Uri uri, ContentValues[] values) {
         if (values == null) {
             return 0;
         }
         int numValues = values.length;
         int successes = 0;
         final SQLiteDatabase db = getWritableDatabase(uri);
         debug("bulkInsert: explicitly starting transaction.");
         beginBatch(db);
         try {
             for (int i = 0; i < numValues; i++) {
                 insertInTransaction(uri, values[i]);
                 successes++;
             }
             trace("Flushing DB bulkinsert...");
             markBatchSuccessful(db);
         } finally {
             debug("bulkInsert: explicitly ending transaction.");
             endBatch(db);
         }
         if (successes > 0) {
             final boolean shouldSyncToNetwork = !isCallerSync(uri);
             getContext().getContentResolver().notifyChange(uri, null, shouldSyncToNetwork);
         }
         return successes;
     }
     /**
      * Indicates whether a query should include deleted fields
      * based on the URI.
      * @param uri query URI
      */
     protected static boolean shouldShowDeleted(Uri uri) {
         String showDeleted = uri.getQueryParameter(BrowserContract.PARAM_SHOW_DELETED);
         return !TextUtils.isEmpty(showDeleted);
     }
     /**
      * Indicates whether an insertion should be made if a record doesn't
      * exist, based on the URI.
      * @param uri query URI
      */
     protected static boolean shouldUpdateOrInsert(Uri uri) {
         String insertIfNeeded = uri.getQueryParameter(BrowserContract.PARAM_INSERT_IF_NEEDED);
         return Boolean.parseBoolean(insertIfNeeded);
     }
     /**
      * Indicates whether query is a test based on the URI.
      * @param uri query URI
      */
     protected static boolean isTest(Uri uri) {
         if (uri == null) {
             return false;
         }
         String isTest = uri.getQueryParameter(BrowserContract.PARAM_IS_TEST);
         return !TextUtils.isEmpty(isTest);
     }
     /**
      * Return true of the query is from Firefox Sync.
      * @param uri query URI
      */
     protected static boolean isCallerSync(Uri uri) {
         String isSync = uri.getQueryParameter(BrowserContract.PARAM_IS_SYNC);
         return !TextUtils.isEmpty(isSync);
     }
     protected static void trace(String message) {
         if (logVerbose) {
             Log.v(LOGTAG, message);
         }
     }
     protected static void debug(String message) {
         if (logDebug) {
             Log.d(LOGTAG, message);
         }
     }
 }

The Tor Browser / annotate

mobile/android/base/db/AbstractTransactionalProvider.java@6474c204b198 (annotated)

mobile/android/base/db/AbstractTransactionalProvider.java