mongodb/db/jsobjmanipulator.h

/** jsobjManipulator.h */

/**
 *    Copyright (C) 2009 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 "jsobj.h"
#include "repl.h"

namespace mongo {

/** Manipulate the binary representation of a BSONElement in-place.
 Careful, this casts away const.
 */
class BSONElementManipulator {
public:
    BSONElementManipulator( const BSONElement &element ) :
    element_( element ) {
    }
    /** Replace a Timestamp type with a Date type initialized to
     OpTime::now().asDate()
     */
    void initTimestamp() {
        massert( "Expected CurrentTime type", element_.type() == Timestamp );
        unsigned long long &timestamp = *( reinterpret_cast< unsigned long long* >( value() ) );
        if ( timestamp == 0 )
            timestamp = OpTime::now().asDate();
    }
    /** Change the value, in place, of the number. */
    void setNumber(double d) {
        if ( element_.type() == NumberDouble ) *reinterpret_cast< double * >( value() )  = d;
        else if ( element_.type() == NumberInt ) *reinterpret_cast< int * >( value() ) = (int) d;
    }    
private:
    char *data() { return nonConst( element_.rawdata() ); }
    char *value() { return nonConst( element_.value() ); }
    static char *nonConst( const char *s ) { return const_cast< char * >( s ); }
    const BSONElement element_;
};

} // namespace mongo