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undo_database.cpp
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undo_database.cpp
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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.
*/
#include <graphene/db/object_database.hpp>
#include <graphene/db/undo_database.hpp>
#include <fc/reflect/variant.hpp>
namespace graphene { namespace db {
void undo_database::enable() { _disabled = false; }
void undo_database::disable() { _disabled = true; }
undo_database::session undo_database::start_undo_session( bool force_enable )
{
if( _disabled && !force_enable ) return session(*this);
bool disable_on_exit = _disabled && force_enable;
if( force_enable )
_disabled = false;
while( size() > max_size() )
_stack.pop_front();
_stack.emplace_back();
++_active_sessions;
return session(*this, disable_on_exit );
}
void undo_database::on_create( const object& obj )
{
if( _disabled ) return;
if( _stack.empty() )
_stack.emplace_back();
auto& state = _stack.back();
auto index_id = object_id_type( obj.id.space(), obj.id.type(), 0 );
auto itr = state.old_index_next_ids.find( index_id );
if( itr == state.old_index_next_ids.end() )
state.old_index_next_ids[index_id] = obj.id;
state.new_ids.insert(obj.id);
}
void undo_database::on_modify( const object& obj )
{
if( _disabled ) return;
if( _stack.empty() )
_stack.emplace_back();
auto& state = _stack.back();
if( state.new_ids.find(obj.id) != state.new_ids.end() )
return;
auto itr = state.old_values.find(obj.id);
if( itr != state.old_values.end() ) return;
state.old_values[obj.id] = obj.clone();
}
void undo_database::on_remove( const object& obj )
{
if( _disabled ) return;
if( _stack.empty() )
_stack.emplace_back();
undo_state& state = _stack.back();
if( state.new_ids.count(obj.id) )
{
state.new_ids.erase(obj.id);
return;
}
if( state.old_values.count(obj.id) )
{
state.removed[obj.id] = std::move(state.old_values[obj.id]);
state.old_values.erase(obj.id);
return;
}
if( state.removed.count(obj.id) ) return;
state.removed[obj.id] = obj.clone();
}
void undo_database::undo()
{ try {
FC_ASSERT( !_disabled );
FC_ASSERT( _active_sessions > 0 );
disable();
auto& state = _stack.back();
for( auto& item : state.old_values )
{
_db.modify( _db.get_object( item.second->id ), [&]( object& obj ){ obj.move_from( *item.second ); } );
}
for( auto ritr = state.new_ids.begin(); ritr != state.new_ids.end(); ++ritr )
{
_db.remove( _db.get_object(*ritr) );
}
for( auto& item : state.old_index_next_ids )
{
_db.get_mutable_index( item.first.space(), item.first.type() ).set_next_id( item.second );
}
for( auto& item : state.removed )
_db.insert( std::move(*item.second) );
_stack.pop_back();
if( _stack.empty() )
_stack.emplace_back();
enable();
--_active_sessions;
} FC_CAPTURE_AND_RETHROW() }
void undo_database::merge()
{
FC_ASSERT( _active_sessions > 0 );
FC_ASSERT( _stack.size() >=2 );
auto& state = _stack.back();
auto& prev_state = _stack[_stack.size()-2];
// An object's relationship to a state can be:
// in new_ids : new
// in old_values (was=X) : upd(was=X)
// in removed (was=X) : del(was=X)
// not in any of above : nop
//
// When merging A=prev_state and B=state we have a 4x4 matrix of all possibilities:
//
// |--------------------- B ----------------------|
//
// +------------+------------+------------+------------+
// | new | upd(was=Y) | del(was=Y) | nop |
// +------------+------------+------------+------------+------------+
// / | new | N/A | new A| nop C| new A|
// | +------------+------------+------------+------------+------------+
// | | upd(was=X) | N/A | upd(was=X)A| del(was=X)C| upd(was=X)A|
// A +------------+------------+------------+------------+------------+
// | | del(was=X) | N/A | N/A | N/A | del(was=X)A|
// | +------------+------------+------------+------------+------------+
// \ | nop | new B| upd(was=Y)B| del(was=Y)B| nop AB|
// +------------+------------+------------+------------+------------+
//
// Each entry was composed by labelling what should occur in the given case.
//
// Type A means the composition of states contains the same entry as the first of the two merged states for that object.
// Type B means the composition of states contains the same entry as the second of the two merged states for that object.
// Type C means the composition of states contains an entry different from either of the merged states for that object.
// Type N/A means the composition of states violates causal timing.
// Type AB means both type A and type B simultaneously.
//
// The merge() operation is defined as modifying prev_state in-place to be the state object which represents the composition of
// state A and B.
//
// Type A (and AB) can be implemented as a no-op; prev_state already contains the correct value for the merged state.
// Type B (and AB) can be implemented by copying from state to prev_state.
// Type C needs special case-by-case logic.
// Type N/A can be ignored or assert(false) as it can only occur if prev_state and state have illegal values
// (a serious logic error which should never happen).
//
// We can only be outside type A/AB (the nop path) if B is not nop, so it suffices to iterate through B's three containers.
// *+upd
for( auto& obj : state.old_values )
{
if( prev_state.new_ids.find(obj.second->id) != prev_state.new_ids.end() )
{
// new+upd -> new, type A
continue;
}
if( prev_state.old_values.find(obj.second->id) != prev_state.old_values.end() )
{
// upd(was=X) + upd(was=Y) -> upd(was=X), type A
continue;
}
// del+upd -> N/A
assert( prev_state.removed.find(obj.second->id) == prev_state.removed.end() );
// nop+upd(was=Y) -> upd(was=Y), type B
prev_state.old_values[obj.second->id] = std::move(obj.second);
}
// *+new, but we assume the N/A cases don't happen, leaving type B nop+new -> new
for( auto id : state.new_ids )
prev_state.new_ids.insert(id);
// old_index_next_ids can only be updated, iterate over *+upd cases
for( auto& item : state.old_index_next_ids )
{
if( prev_state.old_index_next_ids.find( item.first ) == prev_state.old_index_next_ids.end() )
{
// nop+upd(was=Y) -> upd(was=Y), type B
prev_state.old_index_next_ids[item.first] = item.second;
continue;
}
else
{
// upd(was=X)+upd(was=Y) -> upd(was=X), type A
// type A implementation is a no-op, as discussed above, so there is no code here
continue;
}
}
// *+del
for( auto& obj : state.removed )
{
if( prev_state.new_ids.find(obj.second->id) != prev_state.new_ids.end() )
{
// new + del -> nop (type C)
prev_state.new_ids.erase(obj.second->id);
continue;
}
auto it = prev_state.old_values.find(obj.second->id);
if( it != prev_state.old_values.end() )
{
// upd(was=X) + del(was=Y) -> del(was=X)
prev_state.removed[obj.second->id] = std::move(it->second);
prev_state.old_values.erase(obj.second->id);
continue;
}
// del + del -> N/A
assert( prev_state.removed.find( obj.second->id ) == prev_state.removed.end() );
// nop + del(was=Y) -> del(was=Y)
prev_state.removed[obj.second->id] = std::move(obj.second);
}
_stack.pop_back();
--_active_sessions;
}
void undo_database::commit()
{
FC_ASSERT( _active_sessions > 0 );
--_active_sessions;
}
void undo_database::pop_commit()
{
FC_ASSERT( _active_sessions == 0 );
FC_ASSERT( !_stack.empty() );
disable();
try {
auto& state = _stack.back();
for( auto& item : state.old_values )
{
_db.modify( _db.get_object( item.second->id ), [&]( object& obj ){ obj.move_from( *item.second ); } );
}
for( auto ritr = state.new_ids.begin(); ritr != state.new_ids.end(); ++ritr )
{
_db.remove( _db.get_object(*ritr) );
}
for( auto& item : state.old_index_next_ids )
{
_db.get_mutable_index( item.first.space(), item.first.type() ).set_next_id( item.second );
}
for( auto& item : state.removed )
_db.insert( std::move(*item.second) );
_stack.pop_back();
}
catch ( const fc::exception& e )
{
elog( "error popping commit ${e}", ("e", e.to_detail_string() ) );
enable();
throw;
}
enable();
}
const undo_state& undo_database::head()const
{
FC_ASSERT( !_stack.empty() );
return _stack.back();
}
} } // graphene::db