gecko-dev/storage/public/StatementCache.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
* ***** 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 the mozStorage statement cache.
*
* The Initial Developer of the Original Code is
* the Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2010
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Shawn Wilsher <me@shawnwilsher.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 mozilla_storage_StatementCache_h
#define mozilla_storage_StatementCache_h
#include "mozIStorageConnection.h"
#include "mozIStorageStatement.h"
#include "mozIStorageAsyncStatement.h"
#include "nsAutoPtr.h"
#include "nsHashKeys.h"
#include "nsInterfaceHashtable.h"
namespace mozilla {
namespace storage {
/**
* Class used to cache statements (mozIStorageStatement or
* mozIStorageAsyncStatement).
*/
template<typename StatementType>
class StatementCache {
public:
/**
* Constructor for the cache.
*
* @note a connection can have more than one cache.
*
* @param aConnection
* A reference to the nsCOMPtr for the connection this cache is to be
* used for. This nsCOMPtr must at least live as long as this class,
* otherwise crashes will happen.
*/
StatementCache(nsCOMPtr<mozIStorageConnection>& aConnection)
: mConnection(aConnection)
{
if (!mCachedStatements.Init()) {
NS_ERROR("Out of memory!?");
}
}
/**
* Obtains a cached statement. If this statement is not yet created, it will
* be created and stored for later use.
*
* @param aQuery
* The SQL string (either a const char [] or nsACString) to get a
* cached query for.
* @return the cached statement, or null upon error.
*/
inline
already_AddRefed<StatementType>
GetCachedStatement(const nsACString& aQuery)
{
nsCOMPtr<StatementType> stmt;
if (!mCachedStatements.Get(aQuery, getter_AddRefs(stmt))) {
stmt = CreateStatement(aQuery);
NS_ENSURE_TRUE(stmt, nsnull);
if (!mCachedStatements.Put(aQuery, stmt)) {
NS_ERROR("Out of memory!?");
}
}
return stmt.forget();
}
template<int N>
NS_ALWAYS_INLINE already_AddRefed<StatementType>
GetCachedStatement(const char (&aQuery)[N])
{
nsDependentCString query(aQuery, N - 1);
return GetCachedStatement(query);
}
/**
* Finalizes all cached statements so the database can be safely closed. The
* behavior of this cache is unspecified after this method is called.
*/
inline
void
FinalizeStatements()
{
(void)mCachedStatements.Enumerate(FinalizeCachedStatements, NULL);
// Clear the cache at this time too!
(void)mCachedStatements.Clear();
}
private:
inline
already_AddRefed<StatementType>
CreateStatement(const nsACString& aQuery);
static
PLDHashOperator
FinalizeCachedStatements(const nsACString& aKey,
nsCOMPtr<StatementType>& aStatement,
void*)
{
(void)aStatement->Finalize();
return PL_DHASH_NEXT;
}
nsInterfaceHashtable<nsCStringHashKey, StatementType> mCachedStatements;
nsCOMPtr<mozIStorageConnection>& mConnection;
};
template< >
inline
already_AddRefed<mozIStorageStatement>
StatementCache<mozIStorageStatement>::CreateStatement(const nsACString& aQuery)
{
NS_ENSURE_TRUE(mConnection, nsnull);
nsCOMPtr<mozIStorageStatement> stmt;
nsresult rv = mConnection->CreateStatement(aQuery, getter_AddRefs(stmt));
if (NS_FAILED(rv)) {
nsCString error;
error.AppendLiteral("The statement '");
error.Append(aQuery);
error.AppendLiteral("' failed to compile with the error message '");
nsCString msg;
(void)mConnection->GetLastErrorString(msg);
error.Append(msg);
error.AppendLiteral("'.");
NS_ERROR(error.get());
}
NS_ENSURE_SUCCESS(rv, nsnull);
return stmt.forget();
}
template< >
inline
already_AddRefed<mozIStorageAsyncStatement>
StatementCache<mozIStorageAsyncStatement>::CreateStatement(const nsACString& aQuery)
{
NS_ENSURE_TRUE(mConnection, nsnull);
nsCOMPtr<mozIStorageAsyncStatement> stmt;
nsresult rv = mConnection->CreateAsyncStatement(aQuery, getter_AddRefs(stmt));
NS_ENSURE_SUCCESS(rv, nsnull);
return stmt.forget();
}
} // namespace storage
} // namespace mozilla
#endif // mozilla_storage_StatementCache_h