PerconaFT/ftcxx/cursor.hpp

/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
#ident "$Id$"
/*======
This file is part of PerconaFT.


Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved.

    PerconaFT is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License, version 2,
    as published by the Free Software Foundation.

    PerconaFT 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with PerconaFT.  If not, see <http://www.gnu.org/licenses/>.

----------------------------------------

    PerconaFT 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.

    PerconaFT 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 PerconaFT.  If not, see <http://www.gnu.org/licenses/>.
======= */

#ident "Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved."

#pragma once

#include <utility>

#include <db.h>

#include "buffer.hpp"
#include "db.hpp"
#include "db_env.hpp"
#include "db_txn.hpp"
#include "slice.hpp"

namespace ftcxx {

    class DB;

    struct IterationStrategy {
        bool forward;
        bool prelock;

        IterationStrategy(bool forward_, bool prelock_)
            : forward(forward_),
              prelock(prelock_)
        {}

        int getf_flags() const {
            if (prelock) {
                return DB_PRELOCKED | DB_PRELOCKED_WRITE;
            } else {
                return DBC_DISABLE_PREFETCHING;
            }
        }
    };

    class Bounds {
        const ::DB *_db;
        Slice _left;
        Slice _right;
        DBT _left_dbt;
        DBT _right_dbt;
        bool _left_infinite;
        bool _right_infinite;
        bool _end_exclusive;

    public:
        Bounds(const DB &db, const Slice &left, const Slice &right, bool end_exclusive)
            : _db(db.db()),
              _left(left.owned()),
              _right(right.owned()),
              _left_dbt(_left.dbt()),
              _right_dbt(_right.dbt()),
              _left_infinite(false),
              _right_infinite(false),
              _end_exclusive(end_exclusive)
        {}

        struct Infinite {};

        Bounds(const DB &db, Infinite, const Slice &right, bool end_exclusive)
            : _db(db.db()),
              _left(),
              _right(right.owned()),
              _left_dbt(_left.dbt()),
              _right_dbt(_right.dbt()),
              _left_infinite(true),
              _right_infinite(false),
              _end_exclusive(end_exclusive)
        {}

        Bounds(const DB &db, const Slice &left, Infinite, bool end_exclusive)
            : _db(db.db()),
              _left(left.owned()),
              _right(),
              _left_dbt(_left.dbt()),
              _right_dbt(_right.dbt()),
              _left_infinite(false),
              _right_infinite(true),
              _end_exclusive(end_exclusive)
        {}

        Bounds(const DB &db, Infinite, Infinite, bool end_exclusive)
            : _db(db.db()),
              _left(),
              _right(),
              _left_dbt(_left.dbt()),
              _right_dbt(_right.dbt()),
              _left_infinite(true),
              _right_infinite(true),
              _end_exclusive(end_exclusive)
        {}

        Bounds(const Bounds &other) = delete;
        Bounds& operator=(const Bounds &) = delete;

        Bounds(Bounds &&o)
            : _db(nullptr),
              _left(),
              _right(),
              _left_infinite(o._left_infinite),
              _right_infinite(o._right_infinite),
              _end_exclusive(o._end_exclusive)
        {
            std::swap(_db, o._db);
            std::swap(_left, o._left);
            std::swap(_right, o._right);
            _left_dbt = _left.dbt();
            _right_dbt = _right.dbt();
        }

        Bounds& operator=(Bounds&& other) {
            std::swap(_db, other._db);
            std::swap(_left, other._left);
            std::swap(_right, other._right);
            _left_dbt = _left.dbt();
            _right_dbt = _right.dbt();
            _left_infinite = other._left_infinite;
            _right_infinite = other._right_infinite;
            _end_exclusive = other._end_exclusive;
            return *this;
        }

        const DBT *left_dbt() const {
            if (_left_infinite) {
                return _db->dbt_neg_infty();
            } else {
                return &_left_dbt;
            }
        }

        const DBT *right_dbt() const {
            if (_right_infinite) {
                return _db->dbt_pos_infty();
            } else {
                return &_right_dbt;
            }
        }

        void set_left(const Slice &left) {
            _left = left.owned();
            _left_dbt = _left.dbt();
            _left_infinite = false;
        }

        void set_right(const Slice &right) {
            _right = right.owned();
            _right_dbt = _right.dbt();
            _right_infinite = false;
        }

        bool left_infinite() const { return _left_infinite; }
        bool right_infinite() const { return _right_infinite; }

        template<class Comparator>
        bool check(Comparator &cmp, const IterationStrategy &strategy, const Slice &key) const;
    };

    /**
     * DBC is a simple RAII wrapper around a DBC object.
     */
    class DBC {
    public:
        DBC(const DB &db, const DBTxn &txn=DBTxn(), int flags=0);
        ~DBC();

        // Directory cursor.
        DBC(const DBEnv &env, const DBTxn &txn=DBTxn());

        DBC(const DBC &) = delete;
        DBC& operator=(const DBC &) = delete;

        DBC(DBC &&o)
            : _txn(),
              _dbc(nullptr)
        {
            std::swap(_txn, o._txn);
            std::swap(_dbc, o._dbc);
        }

        DBC& operator=(DBC &&o) {
            std::swap(_txn, o._txn);
            std::swap(_dbc, o._dbc);
            return *this;
        }

        ::DBC *dbc() const { return _dbc; }

        void set_txn(const DBTxn &txn) const {
            _dbc->c_set_txn(_dbc, txn.txn());
        }

        void close();

        bool set_range(const IterationStrategy &strategy, const Bounds &bounds, YDB_CALLBACK_FUNCTION callback, void *extra) const;

        bool advance(const IterationStrategy &strategy, YDB_CALLBACK_FUNCTION callback, void *extra) const;

    protected:

        // the ordering here matters, for destructors
        DBTxn _txn;
        ::DBC *_dbc;
    };

    /**
     * Cursor supports iterating a cursor over a key range,
     * with bulk fetch buffering, and optional filtering.
     */
    template<class Comparator, class Handler>
    class CallbackCursor {
    public:

        /**
         * Directory cursor.
         */
        CallbackCursor(const DBEnv &env, const DBTxn &txn,
                       Comparator &&cmp, Handler &&handler);

        /**
         * Constructs an cursor.  Better to use DB::cursor instead to
         * avoid template parameters.
         */
        CallbackCursor(const DB &db, const DBTxn &txn, int flags,
                       IterationStrategy iteration_strategy,
                       Bounds bounds,
                       Comparator &&cmp, Handler &&handler);

        /**
         * Gets the next key/val pair in the iteration.  Returns true
         * if there is more data, and fills in key and val.  If the
         * range is exhausted, returns false.
         */
        bool consume_batch();

        void seek(const Slice &key);

        bool finished() const { return _finished; }

        bool ok() const { return !finished(); }

        void set_txn(const DBTxn &txn) const { _dbc.set_txn(txn); }

    private:

        DBC _dbc;
        IterationStrategy _iteration_strategy;
        Bounds _bounds;
        Comparator _cmp;
        Handler _handler;

        bool _finished;

        void init();

        static int getf_callback(const DBT *key, const DBT *val, void *extra) {
            CallbackCursor *i = static_cast<CallbackCursor *>(extra);
            return i->getf(key, val);
        }

        int getf(const DBT *key, const DBT *val);
    };

    template<class Predicate>
    class BufferAppender {
        Buffer &_buf;
        Predicate _filter;

    public:
        BufferAppender(Buffer &buf, Predicate &&filter)
            : _buf(buf),
              _filter(std::forward<Predicate>(filter))
        {}

        bool operator()(const DBT *key, const DBT *val);

        static size_t marshalled_size(size_t keylen, size_t vallen) {
            return (sizeof(((DBT *)0)->size)) + (sizeof(((DBT *)0)->size)) + keylen + vallen;
        }

        static void marshall(char *dest, const DBT *key, const DBT *val);

        static void unmarshall(char *src, DBT *key, DBT *val);
        static void unmarshall(char *src, Slice &key, Slice &val);
    };

    template<class Comparator, class Predicate>
    class BufferedCursor {
    public:

        /**
         * Directory cursor.
         */
        BufferedCursor(const DBEnv &env, const DBTxn &txn,
                       Comparator &&cmp, Predicate &&filter);

        /**
         * Constructs an buffered cursor.  Better to use
         * DB::buffered_cursor instead to avoid template parameters.
         */
        BufferedCursor(const DB &db, const DBTxn &txn, int flags,
                       IterationStrategy iteration_strategy,
                       Bounds bounds,
                       Comparator &&cmp, Predicate &&filter);

        /**
         * Gets the next key/val pair in the iteration.  Returns true
         * if there is more data, and fills in key and val.  If the
         * range is exhausted, returns false.
         */
        bool next(DBT *key, DBT *val);
        bool next(Slice &key, Slice &val);

        void seek(const Slice &key);

        bool ok() const {
            return _cur.ok() || _buf.more();
        }

        void set_txn(const DBTxn &txn) const { _cur.set_txn(txn); }

    private:

        typedef BufferAppender<Predicate> Appender;

        Buffer _buf;
        CallbackCursor<Comparator, Appender> _cur;
    };

    template<class Comparator>
    class SimpleCursor {
    public:
        SimpleCursor(const DBEnv &env, const DBTxn &txn,
                     Comparator &&cmp, Slice &key, Slice &val);

        SimpleCursor(const DB &db, const DBTxn &txn, int flags,
                     IterationStrategy iteration_strategy,
                     Bounds bounds, Comparator &&cmp,
                     Slice &key, Slice &val);

        /**
         * Gets the next key/val pair in the iteration.  Copies data
         * directly into key and val, which will own their buffers.
         */
        bool next();

        void seek(const Slice &key);

        bool ok() const {
            return _cur.ok();
        }

        void set_txn(const DBTxn &txn) const { _cur.set_txn(txn); }

        class SliceCopier {
            Slice &_key;
            Slice &_val;

        public:
            SliceCopier(Slice &key, Slice &val)
                : _key(key),
                  _val(val)
            {}

            bool operator()(const DBT *key, const DBT *val) {
                _key = Slice(*key).owned();
                _val = Slice(*val).owned();

                // Don't bulk fetch.
                return false;
            }
        };

    private:

        SliceCopier _copier;
        CallbackCursor<Comparator, SliceCopier&> _cur;
    };

} // namespace ftcxx

#include "cursor-inl.hpp"