// extent.h

/**
*    Copyright (C) 2013 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/>.
*
*    As a special exception, the copyright holders give permission to link the
*    code of portions of this program with the OpenSSL library under certain
*    conditions as described in each individual source file and distribute
*    linked combinations including the program with the OpenSSL library. You
*    must comply with the GNU Affero General Public License in all respects for
*    all of the code used other than as permitted herein. If you modify file(s)
*    with this exception, you may extend this exception to your version of the
*    file(s), but you are not obligated to do so. If you do not wish to do so,
*    delete this exception statement from your version. If you delete this
*    exception statement from all source files in the program, then also delete
*    it in the license file.
*/

#pragma once

#include <string>
#include <vector>

#include "mongo/db/diskloc.h"
#include "mongo/db/structure/catalog/namespace.h"

namespace mongo {

    /* extents are datafile regions where all the records within the region
       belong to the same namespace.

    (11:12:35 AM) dm10gen: when the extent is allocated, all its empty space is stuck into one big DeletedRecord
    (11:12:55 AM) dm10gen: and that is placed on the free list
    */
#pragma pack(1)
    struct Extent {
        enum { extentSignature = 0x41424344 };
        unsigned magic;
        DiskLoc myLoc;

        /* next/prev extent for this namespace */
        DiskLoc xnext;
        DiskLoc xprev;

        /* which namespace this extent is for.  this is just for troubleshooting really
           and won't even be correct if the collection were renamed!
        */
        Namespace nsDiagnostic;

        int length;   /* size of the extent, including these fields */
        DiskLoc firstRecord;
        DiskLoc lastRecord;
        char _extentData[4];

        // -----

        bool validates(const DiskLoc diskLoc, std::vector<std::string>* errors = NULL) const;

        BSONObj dump() const;

        void dump(iostream& s) const;

        bool isOk() const { return magic == extentSignature; }
        void assertOk() const { verify(isOk()); }

        static int HeaderSize() { return sizeof(Extent)-4; }
    };
#pragma pack()

}
