text: // Copyright (c) 2014-2022, The iTw3 Project
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without modification, are
  // permitted provided that the following conditions are met:
  //
  // 1. Redistributions of source code must retain the above copyright notice, this list of
  //    conditions and the following disclaimer.
  //
  // 2. Redistributions in binary form must reproduce the above copyright notice, this list
  //    of conditions and the following disclaimer in the documentation and/or other
  //    materials provided with the distribution.
  //
  // 3. Neither the name of the copyright holder nor the names of its contributors may be
  //    used to endorse or promote products derived from this software without specific
  //    prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
  // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
  // THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
  // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #include "error.h"
  
  #include <lmdb.h>
  #include <string>
  
  namespace {
      struct category final : std::error_category
      {
          virtual const char* name() const noexcept override final
          {
              return "lmdb::error_category()";
          }
  
          virtual std::string message(int value) const override final
          {
              char const* const msg = mdb_strerror(value);
              if (msg)
                  return msg;
              return "Unknown lmdb::error_category() value";
          }
  
          virtual std::error_condition default_error_condition(int value) const noexcept override final
          {
              switch (value)
              {
                  case MDB_KEYEXIST:
                  case MDB_NOTFOUND:
                      break; // map to nothing generic
                  case MDB_PAGE_NOTFOUND:
                  case MDB_CORRUPTED:
                      return std::errc::bad_address;
                  case MDB_PANIC:
                  case MDB_VERSION_MISMATCH:
                  case MDB_INVALID:
                      break; // map to nothing generic
                  case MDB_MAP_FULL:
                      return std::errc::no_buffer_space;
                  case MDB_DBS_FULL:
                      break; // map to nothing generic
                  case MDB_READERS_FULL:
                  case MDB_TLS_FULL:
                      return std::errc::no_lock_available;
                  case MDB_TXN_FULL:
                  case MDB_CURSOR_FULL:
                  case MDB_PAGE_FULL:
                  case MDB_MAP_RESIZED:
                      break; // map to nothing generic
                  case MDB_INCOMPATIBLE:
                      return std::errc::invalid_argument;
                  case MDB_BAD_RSLOT:
                  case MDB_BAD_TXN:
                  case MDB_BAD_VALSIZE:
                  case MDB_BAD_DBI:
                      return std::errc::invalid_argument;
                  default:
                      return std::error_condition{value, std::generic_category()};
              }
              return std::error_condition{value, *this};
          }
      };
  }
  
  namespace lmdb
  {
      std::error_category const& error_category() noexcept
      {
          static const category instance{};
          return instance;
      }
  }
  
  