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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/>.
*/
#include "pch.h"
#include "pdfile.h"
#include "curop-inl.h"
namespace mongo {
bool BasicCursor::advance() {
killCurrentOp.checkForInterrupt();
if ( eof() ) {
if ( tailable_ && !last.isNull() ) {
curr = s->next( last );
}
else {
return false;
}
}
else {
last = curr;
curr = s->next( curr );
}
incNscanned();
return ok();
}
/* these will be used outside of mutexes - really functors - thus the const */
class Forward : public AdvanceStrategy {
virtual DiskLoc next( const DiskLoc &prev ) const {
return prev.rec()->getNext( prev );
}
} _forward;
class Reverse : public AdvanceStrategy {
virtual DiskLoc next( const DiskLoc &prev ) const {
return prev.rec()->getPrev( prev );
}
} _reverse;
const AdvanceStrategy *forward() {
return &_forward;
}
const AdvanceStrategy *reverse() {
return &_reverse;
}
DiskLoc nextLoop( NamespaceDetails *nsd, const DiskLoc &prev ) {
assert( nsd->capLooped() );
DiskLoc next = forward()->next( prev );
if ( !next.isNull() )
return next;
return nsd->firstRecord();
}
DiskLoc prevLoop( NamespaceDetails *nsd, const DiskLoc &curr ) {
assert( nsd->capLooped() );
DiskLoc prev = reverse()->next( curr );
if ( !prev.isNull() )
return prev;
return nsd->lastRecord();
}
ForwardCappedCursor::ForwardCappedCursor( NamespaceDetails *_nsd, const DiskLoc &startLoc ) :
nsd( _nsd ) {
if ( !nsd )
return;
DiskLoc start = startLoc;
if ( start.isNull() ) {
if ( !nsd->capLooped() )
start = nsd->firstRecord();
else {
start = nsd->capExtent.ext()->firstRecord;
if ( !start.isNull() && start == nsd->capFirstNewRecord ) {
start = nsd->capExtent.ext()->lastRecord;
start = nextLoop( nsd, start );
}
}
}
curr = start;
s = this;
incNscanned();
}
DiskLoc ForwardCappedCursor::next( const DiskLoc &prev ) const {
assert( nsd );
if ( !nsd->capLooped() )
return forward()->next( prev );
DiskLoc i = prev;
// Last record
if ( i == nsd->capExtent.ext()->lastRecord )
return DiskLoc();
i = nextLoop( nsd, i );
// If we become capFirstNewRecord from same extent, advance to next extent.
if ( i == nsd->capFirstNewRecord &&
i != nsd->capExtent.ext()->firstRecord )
i = nextLoop( nsd, nsd->capExtent.ext()->lastRecord );
// If we have just gotten to beginning of capExtent, skip to capFirstNewRecord
if ( i == nsd->capExtent.ext()->firstRecord )
i = nsd->capFirstNewRecord;
return i;
}
ReverseCappedCursor::ReverseCappedCursor( NamespaceDetails *_nsd, const DiskLoc &startLoc ) :
nsd( _nsd ) {
if ( !nsd )
return;
DiskLoc start = startLoc;
if ( start.isNull() ) {
if ( !nsd->capLooped() ) {
start = nsd->lastRecord();
}
else {
start = nsd->capExtent.ext()->lastRecord;
}
}
curr = start;
s = this;
incNscanned();
}
DiskLoc ReverseCappedCursor::next( const DiskLoc &prev ) const {
assert( nsd );
if ( !nsd->capLooped() )
return reverse()->next( prev );
DiskLoc i = prev;
// Last record
if ( nsd->capFirstNewRecord == nsd->capExtent.ext()->firstRecord ) {
if ( i == nextLoop( nsd, nsd->capExtent.ext()->lastRecord ) ) {
return DiskLoc();
}
}
else {
if ( i == nsd->capExtent.ext()->firstRecord ) {
return DiskLoc();
}
}
// If we are capFirstNewRecord, advance to prev extent, otherwise just get prev.
if ( i == nsd->capFirstNewRecord )
i = prevLoop( nsd, nsd->capExtent.ext()->firstRecord );
else
i = prevLoop( nsd, i );
// If we just became last in cap extent, advance past capFirstNewRecord
// (We know capExtent.ext()->firstRecord != capFirstNewRecord, since would
// have returned DiskLoc() earlier otherwise.)
if ( i == nsd->capExtent.ext()->lastRecord )
i = reverse()->next( nsd->capFirstNewRecord );
return i;
}
} // namespace mongo
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