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 "nsHashKeys.h"
  15 #include "nsInterfaceHashtable.h"
  16
  17 namespace mozilla {
  18 namespace storage {
  19
  20 /**
  21  * Class used to cache statements (mozIStorageStatement or
  22  * mozIStorageAsyncStatement).
  23  */
  24 template <typename StatementType>
  25 class StatementCache {
  26  public:
  27   /**
  28    * Constructor for the cache.
  29    *
  30    * @note a connection can have more than one cache.
  31    *
  32    * @param aConnection
  33    *        A reference to the nsCOMPtr for the connection this cache is to be
  34    *        used for.  This nsCOMPtr must at least live as long as this class,
  35    *        otherwise crashes will happen.
  36    */
  37   explicit StatementCache(nsCOMPtr<mozIStorageConnection>& aConnection)
  38       : mConnection(aConnection) {}
  39
  40   /**
  41    * Obtains a cached statement.  If this statement is not yet created, it will
  42    * be created and stored for later use.
  43    *
  44    * @param aQuery
  45    *        The SQL string (either a const char [] or nsACString) to get a
  46    *        cached query for.
  47    * @return the cached statement, or null upon error.
  48    */
  49   inline already_AddRefed<StatementType> GetCachedStatement(
  50       const nsACString& aQuery) {
  51     nsCOMPtr<StatementType> stmt;
  52     if (!mCachedStatements.Get(aQuery, getter_AddRefs(stmt))) {
  53       stmt = CreateStatement(aQuery);
  54       NS_ENSURE_TRUE(stmt, nullptr);
  55
  56       mCachedStatements.Put(aQuery, stmt);
  57     }
  58     return stmt.forget();
  59   }
  60
  61   template <int N>
  62   MOZ_ALWAYS_INLINE already_AddRefed<StatementType> GetCachedStatement(
  63       const char (&aQuery)[N]) {
  64     nsDependentCString query(aQuery, N - 1);
  65     return GetCachedStatement(query);
  66   }
  67
  68   /**
  69    * Finalizes all cached statements so the database can be safely closed.  The
  70    * behavior of this cache is unspecified after this method is called.
  71    */
  72   inline void FinalizeStatements() {
  73     for (auto iter = mCachedStatements.Iter(); !iter.Done(); iter.Next()) {
  74       (void)iter.Data()->Finalize();
  75     }
  76
  77     // Clear the cache at this time too!
  78     (void)mCachedStatements.Clear();
  79   }
  80
  81  private:
  82   inline already_AddRefed<StatementType> CreateStatement(
  83       const nsACString& aQuery);
  84
  85   nsInterfaceHashtable<nsCStringHashKey, StatementType> mCachedStatements;
  86   nsCOMPtr<mozIStorageConnection>& mConnection;
  87 };
  88
  89 template <>
  90 inline already_AddRefed<mozIStorageStatement>
  91 StatementCache<mozIStorageStatement>::CreateStatement(
  92     const nsACString& aQuery) {
  93   NS_ENSURE_TRUE(mConnection, nullptr);
  94
  95   nsCOMPtr<mozIStorageStatement> stmt;
  96   nsresult rv = mConnection->CreateStatement(aQuery, getter_AddRefs(stmt));
  97   if (NS_FAILED(rv)) {
  98     nsCString error;
  99     error.AppendLiteral("The statement '");
 100     error.Append(aQuery);
 101     error.AppendLiteral("' failed to compile with the error message '");
 102     nsCString msg;
 103     (void)mConnection->GetLastErrorString(msg);
 104     error.Append(msg);
 105     error.AppendLiteral("'.");
 106     NS_ERROR(error.get());
 107   }
 108   NS_ENSURE_SUCCESS(rv, nullptr);
 109
 110   return stmt.forget();
 111 }
 112
 113 template <>
 114 inline already_AddRefed<mozIStorageAsyncStatement>
 115 StatementCache<mozIStorageAsyncStatement>::CreateStatement(
 116     const nsACString& aQuery) {
 117   NS_ENSURE_TRUE(mConnection, nullptr);
 118
 119   nsCOMPtr<mozIStorageAsyncStatement> stmt;
 120   nsresult rv = mConnection->CreateAsyncStatement(aQuery, getter_AddRefs(stmt));
 121   NS_ENSURE_SUCCESS(rv, nullptr);
 122
 123   return stmt.forget();
 124 }
 125
 126 }  // namespace storage
 127 }  // namespace mozilla
 128
 129 #endif  // mozilla_storage_StatementCache_h