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/**
* 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/>.
*/
#pragma once
#include "../stdafx.h"
#include "jsobj.h"
#include "diskloc.h"
namespace mongo {
class Record;
/* Query cursors, base class. This is for our internal cursors. "ClientCursor" is a separate
concept and is for the user's cursor.
WARNING concurrency: the vfunctions below are called back from within a
ClientCursor::ccmutex. Don't cause a deadlock, you've been warned.
*/
class Cursor {
public:
virtual ~Cursor() {}
virtual bool ok() = 0;
bool eof() {
return !ok();
}
virtual Record* _current() = 0;
virtual BSONObj current() = 0;
virtual DiskLoc currLoc() = 0;
virtual bool advance() = 0; /*true=ok*/
virtual BSONObj currKey() const { return BSONObj(); }
// DiskLoc the cursor requires for continued operation. Before this
// DiskLoc is deleted, the cursor must be incremented or destroyed.
virtual DiskLoc refLoc() = 0;
/* Implement these if you want the cursor to be "tailable" */
/* Request that the cursor starts tailing after advancing past last record. */
/* The implementation may or may not honor this request. */
virtual void setTailable() {}
/* indicates if tailing is enabled. */
virtual bool tailable() {
return false;
}
virtual void aboutToDeleteBucket(const DiskLoc& b) { }
/* optional to implement. if implemented, means 'this' is a prototype */
virtual Cursor* clone() {
return 0;
}
virtual BSONObj indexKeyPattern() {
return BSONObj();
}
/* called after every query block is iterated -- i.e. between getMore() blocks
so you can note where we are, if necessary.
*/
virtual void noteLocation() { }
/* called before query getmore block is iterated */
virtual void checkLocation() { }
virtual string toString() {
return "abstract?";
}
/* used for multikey index traversal to avoid sending back dups. see Matcher::matches().
if a multikey index traversal:
if loc has already been sent, returns true.
otherwise, marks loc as sent.
@param deep - match was against an array, so we know it is multikey. this is legacy and kept
for backwards datafile compatibility. 'deep' can be eliminated next time we
force a data file conversion. 7Jul09
*/
virtual bool getsetdup(DiskLoc loc) = 0;
virtual BSONObj prettyStartKey() const { return BSONObj(); }
virtual BSONObj prettyEndKey() const { return BSONObj(); }
virtual bool capped() const { return false; }
};
// strategy object implementing direction of traversal.
class AdvanceStrategy {
public:
virtual ~AdvanceStrategy() { }
virtual DiskLoc next( const DiskLoc &prev ) const = 0;
};
const AdvanceStrategy *forward();
const AdvanceStrategy *reverse();
/* table-scan style cursor */
class BasicCursor : public Cursor {
protected:
DiskLoc curr, last;
const AdvanceStrategy *s;
private:
bool tailable_;
void init() {
tailable_ = false;
}
public:
bool ok() {
return !curr.isNull();
}
Record* _current() {
assert( ok() );
return curr.rec();
}
BSONObj current() {
Record *r = _current();
BSONObj j(r);
return j;
}
virtual DiskLoc currLoc() {
return curr;
}
virtual DiskLoc refLoc() {
return curr.isNull() ? last : curr;
}
bool advance();
BasicCursor(DiskLoc dl, const AdvanceStrategy *_s = forward()) : curr(dl), s( _s ) {
init();
}
BasicCursor(const AdvanceStrategy *_s = forward()) : s( _s ) {
init();
}
virtual string toString() {
return "BasicCursor";
}
virtual void setTailable() {
if ( !curr.isNull() || !last.isNull() )
tailable_ = true;
}
virtual bool tailable() {
return tailable_;
}
virtual bool getsetdup(DiskLoc loc) { return false; }
};
/* used for order { $natural: -1 } */
class ReverseCursor : public BasicCursor {
public:
ReverseCursor(DiskLoc dl) : BasicCursor( dl, reverse() ) { }
ReverseCursor() : BasicCursor( reverse() ) { }
virtual string toString() {
return "ReverseCursor";
}
};
class NamespaceDetails;
class ForwardCappedCursor : public BasicCursor, public AdvanceStrategy {
public:
ForwardCappedCursor( NamespaceDetails *nsd = 0, const DiskLoc &startLoc = DiskLoc() );
virtual string toString() {
return "ForwardCappedCursor";
}
virtual DiskLoc next( const DiskLoc &prev ) const;
virtual bool capped() const { return true; }
private:
NamespaceDetails *nsd;
};
class ReverseCappedCursor : public BasicCursor, public AdvanceStrategy {
public:
ReverseCappedCursor( NamespaceDetails *nsd = 0, const DiskLoc &startLoc = DiskLoc() );
virtual string toString() {
return "ReverseCappedCursor";
}
virtual DiskLoc next( const DiskLoc &prev ) const;
virtual bool capped() const { return true; }
private:
NamespaceDetails *nsd;
};
} // namespace mongo
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