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// extsort.h
/**
* Copyright (C) 2008 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include "../stdafx.h"
#include "jsobj.h"
#include "namespace.h"
#include <map>
namespace mongo {
/**
for sorting by BSONObj and attaching a value
*/
class BSONObjExternalSorter : boost::noncopyable {
public:
typedef pair<BSONObj,DiskLoc> Data;
private:
class FileIterator : boost::noncopyable {
public:
FileIterator( string file );
~FileIterator();
bool more();
Data next();
private:
MemoryMappedFile _file;
char * _buf;
char * _end;
};
class MyCmp {
public:
MyCmp( const BSONObj & order = BSONObj() ) : _order( order ){}
bool operator()( const Data &l, const Data &r ) const {
_compares++;
int x = l.first.woCompare( r.first , _order );
if ( x )
return x < 0;
return l.second.compare( r.second ) < 0;
};
private:
BSONObj _order;
};
public:
typedef list<Data> InMemory;
class Iterator : boost::noncopyable {
public:
Iterator( BSONObjExternalSorter * sorter );
~Iterator();
bool more();
Data next();
private:
MyCmp _cmp;
vector<FileIterator*> _files;
vector< pair<Data,bool> > _stash;
InMemory * _in;
InMemory::iterator _it;
};
BSONObjExternalSorter( const BSONObj & order = BSONObj() , long maxFileSize = 1024 * 1024 * 100 );
~BSONObjExternalSorter();
void add( const BSONObj& o , const DiskLoc & loc );
void add( const BSONObj& o , int a , int b ){
add( o , DiskLoc( a , b ) );
}
/* call after adding values, and before fetching the iterator */
void sort();
auto_ptr<Iterator> iterator(){
uassert( "not sorted" , _sorted );
return auto_ptr<Iterator>( new Iterator( this ) );
}
int numFiles(){
return _files.size();
}
private:
void sort( string file );
void finishMap();
BSONObj _order;
long _maxFilesize;
path _root;
InMemory * _cur;
long _curSizeSoFar;
list<string> _files;
bool _sorted;
static unsigned long long _compares;
};
}
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