dbclientcursor.h

// file dbclientcursor.h

/*    Copyright 2009 10gen Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

#pragma once

#include <stack>

#include "mongo/client/dbclientinterface.h"
#include "mongo/client/export_macros.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/json.h"
#include "mongo/util/net/message.h"

namespace mongo {

    class DBClientCursorShim;
    class DBClientCursorShimCursorID;
    class DBClientCursorShimArray;
    class DBClientCursorShimTransform;

    class MONGO_CLIENT_API DBClientCursorInterface : boost::noncopyable {
    public:
        virtual ~DBClientCursorInterface() {}
        virtual bool more() = 0;
        virtual BSONObj next() = 0;
        // TODO bring more of the DBClientCursor interface to here
    protected:
        DBClientCursorInterface() {}
    };

    class MONGO_CLIENT_API DBClientCursor : public DBClientCursorInterface {
    public:
        bool more();

        int objsLeftInBatch() const { _assertIfNull(); return _putBack.size() + batch.nReturned - batch.pos; }
        bool moreInCurrentBatch() { return objsLeftInBatch() > 0; }

        BSONObj next();

        void putBack( const BSONObj &o ) { _putBack.push( o.getOwned() ); }

        BSONObj nextSafe();

        void peek(std::vector<BSONObj>&, int atMost);

        // Peeks at first element, if exists
        BSONObj peekFirst();

        bool peekError(BSONObj* error = NULL);

        int itcount() {
            int c = 0;
            while ( more() ) {
                next();
                c++;
            }
            return c;
        }

        bool isDead() const { return cursorId == 0; }

        bool tailable() const { return (opts & QueryOption_CursorTailable) != 0; }

        bool hasResultFlag( int flag ) {
            _assertIfNull();
            return (resultFlags & flag) != 0;
        }

        void setBatchSize(int newBatchSize) { batchSize = newBatchSize; }

        DBClientCursor( DBClientBase* client, const std::string &_ns, BSONObj _query, int _nToReturn,
                        int _nToSkip, const BSONObj *_fieldsToReturn, int queryOptions , int bs );
        DBClientCursor( DBClientBase* client, const std::string &_ns, long long _cursorId, int _nToReturn, int options, int _batchSize );

        virtual ~DBClientCursor();

        long long getCursorId() const { return cursorId; }

        void decouple() { _ownCursor = false; }

        std::string originalHost() const { return _originalHost; }

        std::string getns() const { return ns; }

        Message* getMessage(){ return batch.m.get(); }

        bool initCommand();

        bool init();

        void initLazy( bool isRetry = false );
        bool initLazyFinish( bool& retry );

        class Batch : boost::noncopyable {
            friend class DBClientCursor;
            std::auto_ptr<Message> m;
            int nReturned;
            int pos;
            const char *data;
        public:
            Batch() : m( new Message() ), nReturned(), pos(), data() { }
        };

    private:
        friend class DBClientBase;
        friend class DBClientConnection;
        friend class DBClientCursorShimCursorID;
        friend class DBClientCursorShimArray;
        friend class DBClientCursorShimTransform;
        friend class DBClientWithCommands;

        int nextBatchSize();
        void _finishConsInit();

        BSONObj rawNext();
        bool rawMore();

        std::auto_ptr<DBClientCursorShim> shim;

        Batch batch;
        DBClientBase* _client;
        std::string _originalHost;
        std::string ns;
        BSONObj query;
        int nToReturn;
        int nToSkip;
        long long nReturned;
        const BSONObj *fieldsToReturn;
        int opts;
        int batchSize;
        std::stack< BSONObj > _putBack;
        int resultFlags;
        long long cursorId;
        bool _ownCursor; // see decouple()
        std::string _scopedHost;
        std::string _lazyHost;
        bool wasError;

        void dataReceived() { bool retry; std::string lazyHost; dataReceived( retry, lazyHost ); }
        void dataReceived( bool& retry, std::string& lazyHost );
        void requestMore();
        void exhaustReceiveMore(); // for exhaust

        // Don't call from a virtual function
        void _assertIfNull() const { uassert(13348, "connection died", this); }

        // non-copyable , non-assignable
        DBClientCursor( const DBClientCursor& );
        DBClientCursor& operator=( const DBClientCursor& );

        // init pieces
        void _assembleInit( Message& toSend );
    };

    class MONGO_CLIENT_API DBClientCursorBatchIterator {
    public:
        DBClientCursorBatchIterator( DBClientCursor &c ) : _c( c ), _n() {}
        bool moreInCurrentBatch() { return _c.moreInCurrentBatch(); }
        BSONObj nextSafe() {
            massert( 13383, "BatchIterator empty", moreInCurrentBatch() );
            ++_n;
            return _c.nextSafe();
        }
        int n() const { return _n; }
    private:
        DBClientCursor &_c;
        int _n;
    };

} // namespace mongo