1 files changed, 166 insertions, 0 deletions
diff --git a/src/mongo/db/cursor.cpp b/src/mongo/db/cursor.cpp
new file mode 100644
index 00000000000..ac7afc1532b
--- /dev/null
+++ b/src/mongo/db/cursor.cpp
@@ -0,0 +1,166 @@
+/**
+ *    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