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      1 /*
      2  * Copyright (C) 2013 Apple 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 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 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 #ifndef SQLTransactionStateMachine_h
     27 #define SQLTransactionStateMachine_h
     28 
     29 #include "modules/webdatabase/SQLTransactionState.h"
     30 #include "wtf/ThreadSafeRefCounted.h"
     31 
     32 namespace WebCore {
     33 
     34 template<typename T>
     35 class SQLTransactionStateMachine {
     36 public:
     37     virtual ~SQLTransactionStateMachine() { }
     38 
     39 protected:
     40     SQLTransactionStateMachine();
     41 
     42     typedef SQLTransactionState (T::* StateFunction)();
     43     virtual StateFunction stateFunctionFor(SQLTransactionState) = 0;
     44 
     45     void setStateToRequestedState();
     46     void runStateMachine();
     47 
     48     SQLTransactionState m_nextState;
     49     SQLTransactionState m_requestedState;
     50 
     51 #ifndef NDEBUG
     52     // The state audit trail (i.e. bread crumbs) keeps track of up to the last
     53     // s_sizeOfStateAuditTrail states that the state machine enters. The audit
     54     // trail is updated before entering each state. This is for debugging use
     55     // only.
     56     static const int s_sizeOfStateAuditTrail = 20;
     57     int m_nextStateAuditEntry;
     58     SQLTransactionState m_stateAuditTrail[s_sizeOfStateAuditTrail];
     59 #endif
     60 };
     61 
     62 #if !LOG_DISABLED
     63 extern const char* nameForSQLTransactionState(SQLTransactionState);
     64 #endif
     65 
     66 template<typename T>
     67 SQLTransactionStateMachine<T>::SQLTransactionStateMachine()
     68     : m_nextState(SQLTransactionState::Idle)
     69     , m_requestedState(SQLTransactionState::Idle)
     70 #ifndef NDEBUG
     71     , m_nextStateAuditEntry(0)
     72 #endif
     73 {
     74 #ifndef NDEBUG
     75     for (int i = 0; i < s_sizeOfStateAuditTrail; i++)
     76         m_stateAuditTrail[i] = SQLTransactionState::NumberOfStates;
     77 #endif
     78 }
     79 
     80 template<typename T>
     81 void SQLTransactionStateMachine<T>::setStateToRequestedState()
     82 {
     83     ASSERT(m_nextState == SQLTransactionState::Idle);
     84     ASSERT(m_requestedState != SQLTransactionState::Idle);
     85     m_nextState = m_requestedState;
     86     m_requestedState = SQLTransactionState::Idle;
     87 }
     88 
     89 template<typename T>
     90 void SQLTransactionStateMachine<T>::runStateMachine()
     91 {
     92     ASSERT(SQLTransactionState::End < SQLTransactionState::Idle);
     93     while (m_nextState > SQLTransactionState::Idle) {
     94         ASSERT(m_nextState < SQLTransactionState::NumberOfStates);
     95         StateFunction stateFunction = stateFunctionFor(m_nextState);
     96         ASSERT(stateFunction);
     97 
     98 #ifndef NDEBUG
     99         m_stateAuditTrail[m_nextStateAuditEntry] = m_nextState;
    100         m_nextStateAuditEntry = (m_nextStateAuditEntry + 1) % s_sizeOfStateAuditTrail;
    101 #endif
    102         m_nextState = (static_cast<T*>(this)->*stateFunction)();
    103     }
    104 }
    105 
    106 } // namespace WebCore
    107 
    108 #endif // SQLTransactionStateMachine_h
    109