Line data    Source code

       1             : // Copyright (c) 2019  Made to Order Software Corp.  All Rights Reserved
       2             : //
       3             : // https://snapwebsites.org/project/snapdatabase
       4             : // contact@m2osw.com
       5             : //
       6             : // This program is free software; you can redistribute it and/or modify
       7             : // it under the terms of the GNU General Public License as published by
       8             : // the Free Software Foundation; either version 2 of the License, or
       9             : // (at your option) any later version.
      10             : //
      11             : // This program is distributed in the hope that it will be useful,
      12             : // but WITHOUT ANY WARRANTY; without even the implied warranty of
      13             : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14             : // GNU General Public License for more details.
      15             : //
      16             : // You should have received a copy of the GNU General Public License along
      17             : // with this program; if not, write to the Free Software Foundation, Inc.,
      18             : // 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
      19             : #pragma once
      20             : 
      21             : 
      22             : /** \file
      23             :  * \brief The virtual buffer declarations.
      24             :  *
      25             :  * When dealing with a block, we at times have to reduce or enlarge it.
      26             :  * Several resizing events may occur before it settles. It is best not
      27             :  * to resize the entire block for each event. _To ease the damage,_ we
      28             :  * want to use separate memory buffer to handle growths. Once we are
      29             :  * done with a structure, we can then request for the final data to
      30             :  * be written to file.
      31             :  *
      32             :  * Another case is when a structure ends up being larger than one block.
      33             :  * For example, the table schema can end up requiring 2 or 3 blocks.
      34             :  * To handle that case, we use avirtual buffer as well. This is very
      35             :  * practical because that way we do not have to handle the fact that
      36             :  * the buffer is multiple buffers. The virtual buffer gives us one
      37             :  * linear offset starting at `0` and going up to `size - 1`.
      38             :  */
      39             : 
      40             : // self
      41             : //
      42             : #include    "snapdatabase/block/block.h"
      43             : 
      44             : 
      45             : // C++ lib
      46             : //
      47             : #include    <deque>
      48             : 
      49             : 
      50             : 
      51             : namespace snapdatabase
      52             : {
      53             : 
      54             : 
      55             : 
      56             : typedef std::vector<uint8_t>            buffer_t;
      57             : 
      58             : 
      59           9 : class virtual_buffer
      60             : {
      61             : public:
      62             :     typedef std::shared_ptr<virtual_buffer> pointer_t;
      63             : 
      64             :                                         virtual_buffer();
      65             :                                         virtual_buffer(block::pointer_t b, std::uint64_t offset, std::uint64_t size);
      66             : 
      67             :     void                                add_buffer(block::pointer_t b, std::uint64_t offset, std::uint64_t size);
      68             : 
      69             :     bool                                modified() const;
      70             :     std::size_t                         count_buffers() const;
      71             :     std::uint64_t                       size() const;
      72             :     bool                                is_data_available(std::uint64_t offset, std::uint64_t size) const;
      73             : 
      74             :     int                                 pread(void * buf, std::uint64_t size, std::uint64_t offset, bool full = true) const;
      75             :     int                                 pwrite(void const * buf, std::uint64_t size, std::uint64_t offset, bool allow_growth = false);
      76             :     int                                 pinsert(void const * buf, std::uint64_t size, std::uint64_t offset);
      77             :     int                                 perase(std::uint64_t size, std::uint64_t offset);
      78             : 
      79             : private:
      80          63 :     struct vbuf_t
      81             :     {
      82             :         typedef std::deque<vbuf_t>          deque_t;
      83             : 
      84             :                                             vbuf_t();
      85             :                                             vbuf_t(block::pointer_t b, std::uint64_t offset, std::uint64_t size);
      86             : 
      87             :         block::pointer_t                    f_block = block::pointer_t();
      88             :         buffer_t                            f_data = buffer_t();    // data not (yet) in the block(s)
      89             :         std::uint64_t                       f_offset = 0;
      90             :         std::uint64_t                       f_size = 0;
      91             :     };
      92             : 
      93             :     vbuf_t::deque_t                     f_buffers = vbuf_t::deque_t();
      94             :     std::uint64_t                       f_total_size = 0;
      95             :     bool                                f_modified = false;
      96             : };
      97             : 
      98             : 
      99             : 
     100             : std::ostream & operator << (std::ostream & out, virtual_buffer const & v);
     101             : 
     102             : 
     103             : 
     104             : } // namespace snapdatabase
     105             : // vim: ts=4 sw=4 et