File string_utility.hpp¶

File List > base > string_utility.hpp
/*
 *
 * Copyright 2016 CUBRID Corporation
 *
 *  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.
 *
 */

/*
 * string_utility.hpp - Utility structures and definitions to support C++ String and related STL containers
 */

#ifndef _STRING_UTILITY_HPP_
#define _STRING_UTILITY_HPP_

#include <algorithm>
#include <string_view>
#include <unordered_set>
#include <cctype>

namespace cubbase
{
  /* ========================================================================== */
  /* STRUCT DEFINITIONS */
  /* ========================================================================== */

  struct lowercase_hash
  {
    // for case-insensitive comparision
    // FNV-1a 64-bit: single pass, no allocation; consistent with lowercase_compare
    static constexpr size_t FNV_OFFSET_BASIS = 14695981039346656037ULL;
    static constexpr size_t FNV_PRIME        = 1099511628211ULL;

    size_t operator() (const std::string_view str) const
    {
      size_t hash = FNV_OFFSET_BASIS;
      for (unsigned char c : str)
    {
      hash ^= static_cast<size_t> (std::tolower (c));
      hash *= FNV_PRIME;
    }
      return hash;
    }
  };

  struct lowercase_compare
  {
    // case-insensitive comparision
    bool operator() (const std::string_view l, const std::string_view r) const
    {
      return l.size() == r.size()
         && std::equal ( l.begin(), l.end(), r.begin(),
                 [] (const auto a, const auto b)
      {
    return tolower (a) == tolower (b);
      }
               );
    }
  };

  /* ========================================================================== */
  /* ALIAS DEFINITIONS */
  /* ========================================================================== */

  using string_set_ci_lower = std::unordered_set <std::string_view, lowercase_hash, lowercase_compare>;

}

#endif // _STRING_UTILITY_HPP_