str_icase.hpp

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#pragma once
 
/// @file userver/utils/str_icase.hpp
/// @brief Case insensitive ASCII comparators and hashers
/// @ingroup userver_universal
 
#include <cstdint>
#include <string>
#include <string_view>
 
USERVER_NAMESPACE_BEGIN
 
namespace utils {
 
/// The seed structure used by underlying hashing implementation
struct HashSeed final {
  std::uint64_t k0;
  std::uint64_t k1;
};
 
/// @brief Case sensitive ASCII hashing functor
class StrCaseHash {
 public:
  using is_transparent [[maybe_unused]] = void;
 
  /// Generates a new random hash seed for each hasher instance
  StrCaseHash();
 
  /// Uses the provided seed. Use with caution: a constant seed makes the hasher
  /// vulnerable to HashDOS attacks when arbitrary keys are allowed.
  explicit StrCaseHash(HashSeed seed) noexcept;
 
  std::size_t operator()(std::string_view s) const& noexcept;
 
  template <class StringStrongTypedef>
  auto operator()(const StringStrongTypedef& s) const& noexcept
      -> decltype(operator()(std::string_view{s.GetUnderlying()})) {
    static_assert(noexcept((*this)(std::string_view{s.GetUnderlying()})),
                  "GetUnderlying() should not throw as this affects efficiency "
                  "on some platforms");
 
    return (*this)(std::string_view{s.GetUnderlying()});
  }
 
  HashSeed GetSeed() const noexcept { return seed_; }
 
 private:
  HashSeed seed_;
};
 
/// @brief Case insensitive ASCII hashing functor
class StrIcaseHash {
 public:
  using is_transparent [[maybe_unused]] = void;
 
  /// Generates a new random hash seed for each hasher instance
  StrIcaseHash();
 
  /// Uses the provided seed. Use with caution: a constant seed makes the hasher
  /// vulnerable to HashDOS attacks when arbitrary keys are allowed.
  explicit StrIcaseHash(HashSeed seed) noexcept;
 
  std::size_t operator()(std::string_view s) const& noexcept;
 
 private:
  HashSeed seed_;
};
 
/// Case insensitive ASCII 3-way comparison functor
class StrIcaseCompareThreeWay {
 public:
  // TODO: std::weak_ordering
 
  /// @returns integer <0 when `lhs < rhs`, >0 when `lhs > rhs` and 0 otherwise
  int operator()(std::string_view lhs, std::string_view rhs) const noexcept;
};
 
/// Case insensitive ASCII equality comparison functor
class StrIcaseEqual {
 public:
  using is_transparent [[maybe_unused]] = void;
 
  bool operator()(std::string_view lhs, std::string_view rhs) const noexcept;
};
 
/// Case insensitive ASCII less comparison functor
class StrIcaseLess {
 public:
  using is_transparent [[maybe_unused]] = void;
 
  bool operator()(std::string_view lhs, std::string_view rhs) const noexcept;
};
 
}  // namespace utils
 
USERVER_NAMESPACE_END