The Tor Browser: storage/public/StatementCache.h@8bccb770b82d

     1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-

     2  * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :

     3  * This Source Code Form is subject to the terms of the Mozilla Public

     4  * License, v. 2.0. If a copy of the MPL was not distributed with this

     5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     7 #ifndef mozilla_storage_StatementCache_h

     8 #define mozilla_storage_StatementCache_h

    10 #include "mozIStorageConnection.h"

    11 #include "mozIStorageStatement.h"

    12 #include "mozIStorageAsyncStatement.h"

    14 #include "nsAutoPtr.h"

    15 #include "nsHashKeys.h"

    16 #include "nsInterfaceHashtable.h"

    18 namespace mozilla {

    19 namespace storage {

    21 /**

    22  * Class used to cache statements (mozIStorageStatement or

    23  * mozIStorageAsyncStatement).

    24  */

    25 template<typename StatementType>

    26 class StatementCache {

    27 public:

    28   /**

    29    * Constructor for the cache.

    30    *

    31    * @note a connection can have more than one cache.

    32    *

    33    * @param aConnection

    34    *        A reference to the nsCOMPtr for the connection this cache is to be

    35    *        used for.  This nsCOMPtr must at least live as long as this class,

    36    *        otherwise crashes will happen.

    37    */

    38   StatementCache(nsCOMPtr<mozIStorageConnection>& aConnection)

    39   : mConnection(aConnection)

    40   {

    41   }

    43   /**

    44    * Obtains a cached statement.  If this statement is not yet created, it will

    45    * be created and stored for later use.

    46    *

    47    * @param aQuery

    48    *        The SQL string (either a const char [] or nsACString) to get a

    49    *        cached query for.

    50    * @return the cached statement, or null upon error.

    51    */

    52   inline

    53   already_AddRefed<StatementType>

    54   GetCachedStatement(const nsACString& aQuery)

    55   {

    56     nsCOMPtr<StatementType> stmt;

    57     if (!mCachedStatements.Get(aQuery, getter_AddRefs(stmt))) {

    58       stmt = CreateStatement(aQuery);

    59       NS_ENSURE_TRUE(stmt, nullptr);

    61       mCachedStatements.Put(aQuery, stmt);

    62     }

    63     return stmt.forget();

    64   }

    66   template<int N>

    67   MOZ_ALWAYS_INLINE already_AddRefed<StatementType>

    68   GetCachedStatement(const char (&aQuery)[N])

    69   {

    70     nsDependentCString query(aQuery, N - 1);

    71     return GetCachedStatement(query);

    72   }

    74   /**

    75    * Finalizes all cached statements so the database can be safely closed.  The

    76    * behavior of this cache is unspecified after this method is called.

    77    */

    78   inline

    79   void

    80   FinalizeStatements()

    81   {

    82     (void)mCachedStatements.Enumerate(FinalizeCachedStatements, nullptr);

    84     // Clear the cache at this time too!

    85     (void)mCachedStatements.Clear();

    86   }

    88 private:

    89   inline

    90   already_AddRefed<StatementType>

    91   CreateStatement(const nsACString& aQuery);

    92   static

    93   PLDHashOperator

    94   FinalizeCachedStatements(const nsACString& aKey,

    95                            nsCOMPtr<StatementType>& aStatement,

    96                            void*)

    97   {

    98     (void)aStatement->Finalize();

    99     return PL_DHASH_NEXT;

   100   }

   102   nsInterfaceHashtable<nsCStringHashKey, StatementType> mCachedStatements;

   103   nsCOMPtr<mozIStorageConnection>& mConnection;

   104 };

   106 template< >

   107 inline

   108 already_AddRefed<mozIStorageStatement>

   109 StatementCache<mozIStorageStatement>::CreateStatement(const nsACString& aQuery)

   110 {

   111   NS_ENSURE_TRUE(mConnection, nullptr);

   113   nsCOMPtr<mozIStorageStatement> stmt;

   114   nsresult rv = mConnection->CreateStatement(aQuery, getter_AddRefs(stmt));

   115   if (NS_FAILED(rv)) {

   116     nsCString error;

   117     error.AppendLiteral("The statement '");

   118     error.Append(aQuery);

   119     error.AppendLiteral("' failed to compile with the error message '");

   120     nsCString msg;

   121     (void)mConnection->GetLastErrorString(msg);

   122     error.Append(msg);

   123     error.AppendLiteral("'.");

   124     NS_ERROR(error.get());

   125   }

   126   NS_ENSURE_SUCCESS(rv, nullptr);

   128   return stmt.forget();

   129 }

   131 template< >

   132 inline

   133 already_AddRefed<mozIStorageAsyncStatement>

   134 StatementCache<mozIStorageAsyncStatement>::CreateStatement(const nsACString& aQuery)

   135 {

   136   NS_ENSURE_TRUE(mConnection, nullptr);

   138   nsCOMPtr<mozIStorageAsyncStatement> stmt;

   139   nsresult rv = mConnection->CreateAsyncStatement(aQuery, getter_AddRefs(stmt));

   140   NS_ENSURE_SUCCESS(rv, nullptr);

   142   return stmt.forget();

   143 }

   145 } // namespace storage

   146 } // namespace mozilla

   148 #endif // mozilla_storage_StatementCache_h

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