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/* $Id: delta.cpp,v 1.4 2006-11-05 04:42:43 ganzhorn Exp $
* This file is part of lfhex.
* Copyright (C) 2006 Salem Ganzhorn <eyekode@yahoo.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation version 2.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include "delta.hpp"
//
// DeltaMap class implimentation:
//
DeltaMap::DeltaMap() {} // noop
DeltaMap::~DeltaMap()
{
// just free all of the Delta's
clear();
}
// Free all the Delta's
// Note: this invalidates all pointers to Delta's returned through search()
// do NOT keep returned pointers arround for long.
//
void DeltaMap::clear()
{
_map.erase(_map.begin(),_map.end());
// note: the union of _undo and _redo should contain ALL of the Delta's
// in the map. The intersection of _undo and _redo should be the empty set.
while ( !_undo.empty() ) {
delete _undo.top();
_undo.pop();
}
while ( !_redo.empty() ) {
delete _redo.top();
_redo.pop();
}
}
// returns const ptr to the most recent delta on offset off_t
const Delta * DeltaMap::search( off_t offset ) const
{
delta_map_t::const_iterator itr = _map.find(offset);
if ( itr != _map.end() && (itr->second).size() )
return itr->second.back();
else
return 0;
}
size_t DeltaMap::insert( off_t offset,
const vector<uchar>& oldData,
const vector<uchar>& newData )
{
//
// only modify the newData of the top undo iff the offsets match
// and the redo stack is empty.
//
if( _undo.size() && _undo.top()->offset() == offset && _redo.empty() ) {
//just modify the newData of the top delta
_undo.top()->setNewData( newData );
// _map[offset] _should_ exist
return _map[offset].size();
} else {
// create a new delta
Delta * tmp = new Delta(offset, oldData, newData);
_map[offset].push_back( tmp );
_undo.push( tmp );
return _map[offset].size();
}
}
bool DeltaMap::undo()
{
if( _undo.empty() )
return false;
Delta* d = _undo.top();
_undo.pop();
// find the delta in the delta list indexed by d->offset and remove it.
map<off_t,list<Delta*> >::iterator itr = _map.find(d->offset());
itr->second.remove(d);
// remove the entry iff the list is empty
if( itr->second.empty() ) {
_map.erase(itr);
}
// push the delta back onto the redo stack.
_redo.push( d );
return true;
}
bool DeltaMap::redo()
{
if( _redo.empty() )
return false;
// insert the delta back into the modification list
Delta *d = _redo.top();
_redo.pop();
_map[d->offset()].push_back( d );
_undo.push( d );
return true;
}
// methods for iterating over all the modifications in the tree
off_t DeltaMap::lower_bound(off_t lb) const
{
delta_map_t::const_iterator itr = _map.lower_bound(lb);
if( itr == _map.end() ) {
return -1;
} else {
return itr->first;
}
}
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