third_party/WebKit/Source/modules/webdatabase/SQLTransactionCoordinator.cpp

/*
 * Copyright (C) 2009 Google Inc. All rights reserved.
 * 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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 * copyright notice, this list of conditions and the following disclaimer
 * 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
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#include "modules/webdatabase/SQLTransactionCoordinator.h"

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

namespace blink {

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

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

DEFINE_TRACE(SQLTransactionCoordinator) {}

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

  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 (auto& it : info.activeReadTransactions) {
      it->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()) {
      SQLTransactionBackend* transaction = info.pendingTransactions.takeFirst();
      transaction->notifyDatabaseThreadIsShuttingDown();
    }
  }

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

}  // namespace blink