diff -r 000000000000 -r 6474c204b198 storage/public/StatementCache.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/storage/public/StatementCache.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,148 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#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)
+  {
+  }
+
+  /**
+   * 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, nullptr);
+
+      mCachedStatements.Put(aQuery, stmt);
+    }
+    return stmt.forget();
+  }
+
+  template<int N>
+  MOZ_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, nullptr);
+
+    // 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, nullptr);
+
+  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, nullptr);
+
+  return stmt.forget();
+}
+
+template< >
+inline
+already_AddRefed<mozIStorageAsyncStatement>
+StatementCache<mozIStorageAsyncStatement>::CreateStatement(const nsACString& aQuery)
+{
+  NS_ENSURE_TRUE(mConnection, nullptr);
+
+  nsCOMPtr<mozIStorageAsyncStatement> stmt;
+  nsresult rv = mConnection->CreateAsyncStatement(aQuery, getter_AddRefs(stmt));
+  NS_ENSURE_SUCCESS(rv, nullptr);
+
+  return stmt.forget();
+}
+
+} // namespace storage
+} // namespace mozilla
+
+#endif // mozilla_storage_StatementCache_h