root/Source/modules/webdatabase/SQLTransactionCoordinator.cpp

DEFINITIONS

1. getDatabaseIdentifier
2. trace
3. processPendingTransactions
4. acquireLock
5. releaseLock
6. shutdown

/*
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 * Copyright (C) 2013 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
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 * notice, this list of conditions and the following disclaimer.
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 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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#include "config.h"
#include "modules/webdatabase/SQLTransactionCoordinator.h"

#include "modules/webdatabase/DatabaseBackend.h"
#include "modules/webdatabase/SQLTransactionBackend.h"

namespace WebCore {

static String getDatabaseIdentifier(SQLTransactionBackend* transaction)
{
    DatabaseBackend* database = transaction->database();
    ASSERT(database);
    return database->stringIdentifier();
}

SQLTransactionCoordinator::SQLTransactionCoordinator()
    : m_isShuttingDown(false)
{
}

void SQLTransactionCoordinator::trace(Visitor* visitor)
{
    visitor->trace(m_coordinationInfoMap);
}

void SQLTransactionCoordinator::processPendingTransactions(CoordinationInfo& info)
{
    if (info.activeWriteTransaction || info.pendingTransactions.isEmpty())
        return;

    RefPtrWillBeRawPtr<SQLTransactionBackend> firstPendingTransaction = info.pendingTransactions.first();
    if (firstPendingTransaction->isReadOnly()) {
        do {
            firstPendingTransaction = info.pendingTransactions.takeFirst();
            info.activeReadTransactions.add(firstPendingTransaction);
            firstPendingTransaction->lockAcquired();
        } while (!info.pendingTransactions.isEmpty() && info.pendingTransactions.first()->isReadOnly());
    } else if (info.activeReadTransactions.isEmpty()) {
        info.pendingTransactions.removeFirst();
        info.activeWriteTransaction = firstPendingTransaction;
        firstPendingTransaction->lockAcquired();
    }
}

void SQLTransactionCoordinator::acquireLock(SQLTransactionBackend* transaction)
{
    ASSERT(!m_isShuttingDown);

    String dbIdentifier = getDatabaseIdentifier(transaction);

    CoordinationInfoHeapMap::iterator coordinationInfoIterator = m_coordinationInfoMap.find(dbIdentifier);
    if (coordinationInfoIterator == m_coordinationInfoMap.end()) {
        // No pending transactions for this DB
        CoordinationInfo& info = m_coordinationInfoMap.add(dbIdentifier, CoordinationInfo()).storedValue->value;
        info.pendingTransactions.append(transaction);
        processPendingTransactions(info);
    } else {
        CoordinationInfo& info = coordinationInfoIterator->value;
        info.pendingTransactions.append(transaction);
        processPendingTransactions(info);
    }

}

void SQLTransactionCoordinator::releaseLock(SQLTransactionBackend* transaction)
{
    if (m_isShuttingDown)
        return;

    String dbIdentifier = getDatabaseIdentifier(transaction);

    CoordinationInfoHeapMap::iterator coordinationInfoIterator = m_coordinationInfoMap.find(dbIdentifier);
    ASSERT_WITH_SECURITY_IMPLICATION(coordinationInfoIterator != m_coordinationInfoMap.end());
    CoordinationInfo& info = coordinationInfoIterator->value;

    if (transaction->isReadOnly()) {
        ASSERT(info.activeReadTransactions.contains(transaction));
        info.activeReadTransactions.remove(transaction);
    } else {
        ASSERT(info.activeWriteTransaction == transaction);
        info.activeWriteTransaction = nullptr;
    }

    processPendingTransactions(info);
}

void SQLTransactionCoordinator::shutdown()
{
    // Prevent releaseLock() from accessing / changing the coordinationInfo
    // while we're shutting down.
    m_isShuttingDown = true;

    // Notify all transactions in progress that the database thread is shutting down
    for (CoordinationInfoHeapMap::iterator coordinationInfoIterator = m_coordinationInfoMap.begin();
         coordinationInfoIterator != m_coordinationInfoMap.end(); ++coordinationInfoIterator) {
        CoordinationInfo& info = coordinationInfoIterator->value;

        // Clean up transactions that have reached "lockAcquired":
        // Transaction phase 4 cleanup. See comment on "What happens if a
        // transaction is interrupted?" at the top of SQLTransactionBackend.cpp.
        if (info.activeWriteTransaction)
            info.activeWriteTransaction->notifyDatabaseThreadIsShuttingDown();
        for (WillBeHeapHashSet<RefPtrWillBeMember<SQLTransactionBackend> >::iterator activeReadTransactionsIterator =
                     info.activeReadTransactions.begin();
             activeReadTransactionsIterator != info.activeReadTransactions.end();
             ++activeReadTransactionsIterator) {
            (*activeReadTransactionsIterator)->notifyDatabaseThreadIsShuttingDown();
        }

        // Clean up transactions that have NOT reached "lockAcquired":
        // Transaction phase 3 cleanup. See comment on "What happens if a
        // transaction is interrupted?" at the top of SQLTransactionBackend.cpp.
        while (!info.pendingTransactions.isEmpty()) {
            RefPtrWillBeRawPtr<SQLTransactionBackend> transaction = info.pendingTransactions.first();
            transaction->notifyDatabaseThreadIsShuttingDown();
        }
    }

    // Clean up all pending transactions for all databases
    m_coordinationInfoMap.clear();
}

} // namespace WebCore