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// 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 "mongo/db/diskloc.h"
#include "mongo/db/storage/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)
class Extent {
public:
enum { extentSignature = 0x41424344 };
unsigned magic;
DiskLoc myLoc;
DiskLoc xnext, xprev; /* next/prev extent for this namespace */
/* 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];
static int HeaderSize() { return sizeof(Extent)-4; }
bool validates(const DiskLoc diskLoc, BSONArrayBuilder* errors = NULL);
BSONObj dump();
void dump(iostream& s);
/* assumes already zeroed -- insufficient for block 'reuse' perhaps
Returns a DeletedRecord location which is the data in the extent ready for us.
Caller will need to add that to the freelist structure in namespacedetail.
*/
DiskLoc init(const char *nsname, int _length, int _fileNo, int _offset, bool capped);
/* like init(), but for a reuse case */
DiskLoc reuse(const char *nsname, bool newUseIsAsCapped);
bool isOk() const { return magic == extentSignature; }
void assertOk() const { verify(isOk()); }
Record* getRecord(DiskLoc dl) {
verify( !dl.isNull() );
verify( dl.sameFile(myLoc) );
int x = dl.getOfs() - myLoc.getOfs();
verify( x > 0 );
return (Record *) (((char *) this) + x);
}
Extent* getNextExtent();
Extent* getPrevExtent();
static int maxSize();
static int minSize() { return 0x1000; }
/**
* @param len lengt of record we need
* @param lastRecord size of last extent which is a factor in next extent size
*/
static int followupSize(int len, int lastExtentLen);
/** get a suggested size for the first extent in a namespace
* @param len length of record we need to insert
*/
static int initialSize(int len);
struct FL {
DiskLoc firstRecord;
DiskLoc lastRecord;
};
/** often we want to update just the firstRecord and lastRecord fields.
this helper is for that -- for use with getDur().writing() method
*/
FL* fl() { return (FL*) &firstRecord; }
/** caller must declare write intent first */
void markEmpty();
private:
DiskLoc _reuse(const char *nsname, bool newUseIsAsCapped); // recycle an extent and reuse it for a different ns
};
#pragma pack()
}
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