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durop.h
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durop.h
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// @file durop.h class DurOp and descendants
/**
* Copyright (C) 2010 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 "dur_journalformat.h"
#include "bufreader.h"
namespace mongo {
class AlignedBuilder;
class BufReader;
namespace dur {
const unsigned Alignment = 8192;
/** DurOp - Operations we journal that aren't just basic writes.
*
* Basic writes are logged as JEntry's, and indicated in ram temporarily as struct dur::WriteIntent.
* We don't make WriteIntent inherit from DurOp to keep it as lean as possible as there will be millions of
* them (we don't want a vtable for example there).
*
* For each op we want to journal, we define a subclass.
*/
class DurOp /* copyable */ {
public:
// @param opcode a sentinel value near max unsigned which uniquely identifies the operation.
// @see dur::JEntry
DurOp(unsigned opcode) : _opcode(opcode) { }
virtual ~DurOp() { }
/** serialize the op out to a builder which will then be written (presumably) to the journal */
void serialize(AlignedBuilder& ab);
/** read a durop from journal file referenced by br.
@param opcode the opcode which has already been written from the bufreader
*/
static shared_ptr<DurOp> read(unsigned opcode, BufReader& br);
/** replay the operation (during recovery)
throws
*/
virtual void replay() = 0;
virtual string toString() = 0;
/** if the op requires all file to be closed before doing its work, returns true. */
virtual bool needFilesClosed() { return false; }
protected:
/** DurOp will have already written the opcode for you */
virtual void _serialize(AlignedBuilder& ab) = 0;
private:
const unsigned _opcode;
};
/** indicates creation of a new file */
class FileCreatedOp : public DurOp {
public:
FileCreatedOp(BufReader& log);
FileCreatedOp(string f, unsigned long long l) :
DurOp(JEntry::OpCode_FileCreated), _filename(f), _len(l) { }
virtual void replay();
virtual string toString();
virtual bool needFilesClosed();
protected:
virtual void _serialize(AlignedBuilder& ab);
private:
string _filename;
unsigned long long _len; // size of file, not length of name
};
/** record drop of a database */
class DropDbOp : public DurOp {
public:
DropDbOp(BufReader& log);
DropDbOp(string db) :
DurOp(JEntry::OpCode_DropDb), _db(db) { }
virtual void replay();
virtual string toString() { return string("DropDbOp ") + _db; }
virtual bool needFilesClosed() { return true; }
protected:
virtual void _serialize(AlignedBuilder& ab);
private:
string _db;
};
}
}