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      1 /*
      2  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  */
     25 
     26 #include "config.h"
     27 #include "modules/webdatabase/sqlite/SQLiteTransaction.h"
     28 
     29 #include "modules/webdatabase/sqlite/SQLiteDatabase.h"
     30 
     31 namespace WebCore {
     32 
     33 SQLiteTransaction::SQLiteTransaction(SQLiteDatabase& db, bool readOnly)
     34     : m_db(db)
     35     , m_inProgress(false)
     36     , m_readOnly(readOnly)
     37 {
     38 }
     39 
     40 SQLiteTransaction::~SQLiteTransaction()
     41 {
     42     if (m_inProgress)
     43         rollback();
     44 }
     45 
     46 void SQLiteTransaction::begin()
     47 {
     48     if (!m_inProgress) {
     49         ASSERT(!m_db.m_transactionInProgress);
     50         // Call BEGIN IMMEDIATE for a write transaction to acquire
     51         // a RESERVED lock on the DB file. Otherwise, another write
     52         // transaction (on another connection) could make changes
     53         // to the same DB file before this transaction gets to execute
     54         // any statements. If that happens, this transaction will fail.
     55         // http://www.sqlite.org/lang_transaction.html
     56         // http://www.sqlite.org/lockingv3.html#locking
     57         if (m_readOnly)
     58             m_inProgress = m_db.executeCommand("BEGIN");
     59         else
     60             m_inProgress = m_db.executeCommand("BEGIN IMMEDIATE");
     61         m_db.m_transactionInProgress = m_inProgress;
     62     }
     63 }
     64 
     65 void SQLiteTransaction::commit()
     66 {
     67     if (m_inProgress) {
     68         ASSERT(m_db.m_transactionInProgress);
     69         m_inProgress = !m_db.executeCommand("COMMIT");
     70         m_db.m_transactionInProgress = m_inProgress;
     71     }
     72 }
     73 
     74 void SQLiteTransaction::rollback()
     75 {
     76     // We do not use the 'm_inProgress = m_db.executeCommand("ROLLBACK")' construct here,
     77     // because m_inProgress should always be set to false after a ROLLBACK, and
     78     // m_db.executeCommand("ROLLBACK") can sometimes harmlessly fail, thus returning
     79     // a non-zero/true result (http://www.sqlite.org/lang_transaction.html).
     80     if (m_inProgress) {
     81         ASSERT(m_db.m_transactionInProgress);
     82         m_db.executeCommand("ROLLBACK");
     83         m_inProgress = false;
     84         m_db.m_transactionInProgress = false;
     85     }
     86 }
     87 
     88 void SQLiteTransaction::stop()
     89 {
     90     if (m_inProgress) {
     91         m_inProgress = false;
     92         m_db.m_transactionInProgress = false;
     93     }
     94 }
     95 
     96 bool SQLiteTransaction::wasRolledBackBySqlite() const
     97 {
     98     // According to http://www.sqlite.org/c3ref/get_autocommit.html,
     99     // the auto-commit flag should be off in the middle of a transaction
    100     return m_inProgress && m_db.isAutoCommitOn();
    101 }
    102 
    103 } // namespace WebCore
    104