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// database.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/>.
*
* 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 "mongo/bson/bsonobjbuilder.h"
#include "mongo/db/storage/mmap_v1/diskloc.h"
#include "mongo/db/storage/record_data.h"
#include "mongo/platform/atomic_word.h"
namespace mongo {
class DeletedRecord;
/* MmapV1RecordHeader is a record in a datafile. DeletedRecord is similar but for deleted space.
*11:03:20 AM) dm10gen: regarding extentOfs...
(11:03:42 AM) dm10gen: an extent is a continugous disk area, which contains many Records and DeleteRecords
(11:03:56 AM) dm10gen: a DiskLoc has two pieces, the fileno and ofs. (64 bit total)
(11:04:16 AM) dm10gen: to keep the headesr small, instead of storing a 64 bit ptr to the full extent address, we keep just the offset
(11:04:29 AM) dm10gen: we can do this as we know the record's address, and it has the same fileNo
(11:04:33 AM) dm10gen: see class DiskLoc for more info
(11:04:43 AM) dm10gen: so that is how MmapV1RecordHeader::myExtent() works
(11:04:53 AM) dm10gen: on an alloc(), when we build a new MmapV1RecordHeader, we must populate its extentOfs then
*/
#pragma pack(1)
class MmapV1RecordHeader {
public:
enum HeaderSizeValue { HeaderSize = 16 };
int lengthWithHeaders() const { return _lengthWithHeaders; }
int& lengthWithHeaders() { return _lengthWithHeaders; }
int extentOfs() const { return _extentOfs; }
int& extentOfs() { return _extentOfs; }
int nextOfs() const { return _nextOfs; }
int& nextOfs() { return _nextOfs; }
int prevOfs() const { return _prevOfs; }
int& prevOfs() { return _prevOfs; }
const char* data() const { return _data; }
char* data() { return _data; }
// XXX remove
const char* dataNoThrowing() const { return _data; }
char* dataNoThrowing() { return _data; }
int netLength() const { return _netLength(); }
/* use this when a record is deleted. basically a union with next/prev fields */
DeletedRecord& asDeleted() { return *((DeletedRecord*) this); }
DiskLoc myExtentLoc(const DiskLoc& myLoc) const { return DiskLoc(myLoc.a(), extentOfs() ); }
struct NP {
int nextOfs;
int prevOfs;
};
NP* np() { return (NP*) &_nextOfs; }
RecordData toRecordData() const { return RecordData(_data, _netLength()); }
private:
int _netLength() const { return _lengthWithHeaders - HeaderSize; }
int _lengthWithHeaders;
int _extentOfs;
int _nextOfs;
int _prevOfs;
/** be careful when referencing this that your write intent was correct */
char _data[4];
public:
static bool MemoryTrackingEnabled;
};
#pragma pack()
// TODO: this probably moves to record_store.h
class DeletedRecord {
public:
int lengthWithHeaders() const { return _lengthWithHeaders; }
int& lengthWithHeaders() { return _lengthWithHeaders; }
int extentOfs() const { return _extentOfs; }
int& extentOfs() { return _extentOfs; }
// TODO: we need to not const_cast here but problem is DiskLoc::writing
DiskLoc& nextDeleted() const { return const_cast<DiskLoc&>(_nextDeleted); }
private:
int _lengthWithHeaders;
int _extentOfs;
DiskLoc _nextDeleted;
};
BOOST_STATIC_ASSERT( 16 == sizeof(DeletedRecord) );
} // namespace mongo
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