db_with.hpp

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/*
 * Copyright (c) 2015 Cryptonomex, Inc., and contributors.
 *
 * The MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#pragma once
 
#include <graphene/chain/database.hpp>
 
/*
 * This file provides with() functions which modify the database
 * temporarily, then restore it.  These functions are mostly internal
 * implementation detail of the database.
 *
 * Essentially, we want to be able to use "finally" to restore the
 * database regardless of whether an exception is thrown or not, but there
 * is no "finally" in C++.  Instead, C++ requires us to create a struct
 * and put the finally block in a destructor.  Aagh!
 */
 
namespace graphene { namespace chain { namespace detail {
struct skip_flags_restorer
{
   skip_flags_restorer( node_property_object& npo, uint32_t old_skip_flags )
      : _npo( npo ), _old_skip_flags( old_skip_flags )
   {}
 
   ~skip_flags_restorer()
   {
      _npo.skip_flags = _old_skip_flags;
   }
 
   node_property_object& _npo;
   uint32_t _old_skip_flags;      // initialized in ctor
};
 
struct pending_transactions_restorer
{
   pending_transactions_restorer( database& db, std::vector<processed_transaction>&& pending_transactions )
      : _db(db), _pending_transactions( std::move(pending_transactions) )
   {
      _db.clear_pending();
   }
 
   ~pending_transactions_restorer()
   {
      for( const auto& tx : _db._popped_tx )
      {
         try {
            if( !_db.is_known_transaction( tx.id() ) ) {
               _db._push_transaction( tx );
            }
         } catch ( const fc::exception& ) { // ignore invalid transactions
         }
      }
      _db._popped_tx.clear();
      for( const processed_transaction& tx : _pending_transactions )
      {
         try
         {
            if( !_db.is_known_transaction( tx.id() ) ) {
               _db._push_transaction( tx );
            }
         }
         catch( const fc::exception& )
         { // ignore invalid transactions
         }
      }
   }
 
   database& _db;
   std::vector< processed_transaction > _pending_transactions;
};
 
template< typename Lambda >
void with_skip_flags(
   database& db,
   uint32_t skip_flags,
   Lambda callback )
{
   node_property_object& npo = db.node_properties();
   skip_flags_restorer restorer( npo, npo.skip_flags );
   npo.skip_flags = skip_flags;
   callback();
   return;
}
 
template< typename Lambda >
void without_pending_transactions(
   database& db,
   std::vector<processed_transaction>&& pending_transactions,
   Lambda callback )
{
    pending_transactions_restorer restorer( db, std::move(pending_transactions) );
    callback();
    return;
}
 
} } } // graphene::chain::detail