pjs/storage/public/mozStorageHelper.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Storage code
*
* The Initial Developer of the Original Code is
* Google Inc.
* Portions created by the Initial Developer are Copyright (C) 2005
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Brett Wilson <brettw@gmail.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef MOZSTORAGEHELPER_H
#define MOZSTORAGEHELPER_H
#include "nsAutoPtr.h"
#include "mozIStorageConnection.h"
#include "mozIStorageStatement.h"
#include "mozStorage.h"
/**
* This class wraps a transaction inside a given C++ scope, guaranteeing that
* the transaction will be completed even if you have an exception or
* return early.
*
* aCommitOnComplete controls whether the transaction is committed or rolled
* back when it goes out of scope. A common use is to create an instance with
* commitOnComplete = FALSE (rollback), then call Commit on this object manually
* when your function completes successfully.
*
* Note that nested transactions are not supported by sqlite, so if a transaction
* is already in progress, this object does nothing. Note that in this case,
* you may not get the transaction type you ask for, and you won't be able
* to rollback.
*/
class mozStorageTransaction
{
public:
mozStorageTransaction(mozIStorageConnection* aConnection,
PRBool aCommitOnComplete,
PRInt32 aType = mozIStorageConnection::TRANSACTION_DEFERRED)
: mConnection(aConnection),
mHasTransaction(PR_FALSE),
mCommitOnComplete(aCommitOnComplete),
mCompleted(PR_FALSE)
{
// We won't try to get a transaction if one is already in progress.
if (mConnection)
mHasTransaction = NS_SUCCEEDED(mConnection->BeginTransactionAs(aType));
}
~mozStorageTransaction()
{
if (mConnection && mHasTransaction && ! mCompleted) {
if (mCommitOnComplete)
mConnection->CommitTransaction();
else
mConnection->RollbackTransaction();
}
}
/**
* Commits the transaction if one is in progress. If one is not in progress,
* this is a NOP since the actual owner of the transaction outside of our
* scope is in charge of finally comitting or rolling back the transaction.
*/
nsresult Commit()
{
if (!mConnection || mCompleted)
return NS_OK; // no connection, or already done
mCompleted = PR_TRUE;
if (! mHasTransaction)
return NS_OK; // transaction not ours, ignore
nsresult rv = mConnection->CommitTransaction();
if (NS_SUCCEEDED(rv))
mHasTransaction = PR_FALSE;
return rv;
}
/**
* Rolls back the transaction in progress. You should only call this function
* if this object has a real transaction (HasTransaction() = true) because
* otherwise, there is no transaction to roll back.
*/
nsresult Rollback()
{
if (!mConnection || mCompleted)
return NS_OK; // no connection, or already done
mCompleted = PR_TRUE;
if (! mHasTransaction)
return NS_ERROR_FAILURE;
// It is possible that a rollback will return busy, so we busy wait...
nsresult rv = NS_OK;
do {
rv = mConnection->RollbackTransaction();
if (rv == NS_ERROR_STORAGE_BUSY)
(void)PR_Sleep(PR_INTERVAL_NO_WAIT);
} while (rv == NS_ERROR_STORAGE_BUSY);
if (NS_SUCCEEDED(rv))
mHasTransaction = PR_FALSE;
return rv;
}
/**
* Returns whether this object wraps a real transaction. False means that
* this object doesn't do anything because there was already a transaction in
* progress when it was created.
*/
PRBool HasTransaction()
{
return mHasTransaction;
}
/**
* This sets the default action (commit or rollback) when this object goes
* out of scope.
*/
void SetDefaultAction(PRBool aCommitOnComplete)
{
mCommitOnComplete = aCommitOnComplete;
}
protected:
nsCOMPtr<mozIStorageConnection> mConnection;
PRBool mHasTransaction;
PRBool mCommitOnComplete;
PRBool mCompleted;
};
/**
* This class wraps a statement so that it is guaraneed to be reset when
* this object goes out of scope.
*
* Note that this always just resets the statement. If the statement doesn't
* need resetting, the reset operation is inexpensive.
*/
class NS_STACK_CLASS mozStorageStatementScoper
{
public:
mozStorageStatementScoper(mozIStorageStatement* aStatement)
: mStatement(aStatement)
{
}
~mozStorageStatementScoper()
{
if (mStatement)
mStatement->Reset();
}
/**
* Call this to make the statement not reset. You might do this if you know
* that the statement has been reset.
*/
void Abandon()
{
mStatement = nsnull;
}
protected:
nsCOMPtr<mozIStorageStatement> mStatement;
};
#endif /* MOZSTORAGEHELPER_H */