storage/StatementCache.h

   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/. */
   6
   7 #ifndef mozilla_storage_StatementCache_h
   8 #define mozilla_storage_StatementCache_h
   9
  10 #include "mozIStorageConnection.h"
  11 #include "mozIStorageStatement.h"
  12 #include "mozIStorageAsyncStatement.h"
  13
  14 #include "nsAutoPtr.h"
  15 #include "nsHashKeys.h"
  16 #include "nsInterfaceHashtable.h"
  17
  18 namespace mozilla {
  19 namespace storage {
  20
  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   explicit StatementCache(nsCOMPtr<mozIStorageConnection>& aConnection)
  39   : mConnection(aConnection)
  40   {
  41   }
  42
  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);
  60
  61       mCachedStatements.Put(aQuery, stmt);
  62     }
  63     return stmt.forget();
  64   }
  65
  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   }
  73
  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);
  83
  84     // Clear the cache at this time too!
  85     (void)mCachedStatements.Clear();
  86   }
  87
  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   }
 101
 102   nsInterfaceHashtable<nsCStringHashKey, StatementType> mCachedStatements;
 103   nsCOMPtr<mozIStorageConnection>& mConnection;
 104 };
 105
 106 template< >
 107 inline
 108 already_AddRefed<mozIStorageStatement>
 109 StatementCache<mozIStorageStatement>::CreateStatement(const nsACString& aQuery)
 110 {
 111   NS_ENSURE_TRUE(mConnection, nullptr);
 112
 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);
 127
 128   return stmt.forget();
 129 }
 130
 131 template< >
 132 inline
 133 already_AddRefed<mozIStorageAsyncStatement>
 134 StatementCache<mozIStorageAsyncStatement>::CreateStatement(const nsACString& aQuery)
 135 {
 136   NS_ENSURE_TRUE(mConnection, nullptr);
 137
 138   nsCOMPtr<mozIStorageAsyncStatement> stmt;
 139   nsresult rv = mConnection->CreateAsyncStatement(aQuery, getter_AddRefs(stmt));
 140   NS_ENSURE_SUCCESS(rv, nullptr);
 141
 142   return stmt.forget();
 143 }
 144
 145 } // namespace storage
 146 } // namespace mozilla
 147
 148 #endif // mozilla_storage_StatementCache_h