utils.h

// Contains small utility classes and functions for cpark.
 
#ifndef CPARK_UTILS_H
#define CPARK_UTILS_H
 
#include <ostream>
 
namespace cpark {
 
namespace utils {
 
class NullOStream : public std::ostream {
private:
  class NullBuffer : public std::streambuf {
  public:
    int overflow(int c) override { return c; }
  };
 
  inline static NullBuffer g_null_buffer_;
 
public:
  NullOStream() : std::ostream(&g_null_buffer_) {}
};
 
inline static NullOStream g_null_ostream;
 
template <typename R>
using RddElementType = std::ranges::range_value_t<std::ranges::range_value_t<R>>;
 
template <typename R>
using RddKeyType = decltype(std::declval<RddElementType<R>>().first);
 
template <typename R>
using RddValueType = decltype(std::declval<RddElementType<R>>().second);
 
namespace {
 
template <typename Iterator>
struct GetIteratorTagImpl {};
 
template <typename Iterator>
requires std::forward_iterator<Iterator> struct GetIteratorTagImpl<Iterator> {
  using type = std::forward_iterator_tag;
};
 
template <typename Iterator>
requires std::bidirectional_iterator<Iterator> struct GetIteratorTagImpl<Iterator> {
  using type = std::bidirectional_iterator_tag;
};
 
template <typename Iterator>
requires std::random_access_iterator<Iterator> struct GetIteratorTagImpl<Iterator> {
  using type = std::random_access_iterator_tag;
};
 
} // namespace
 
template <typename Iterator>
using GetIteratorTagType = typename GetIteratorTagImpl<Iterator>::type;
 
}  // namespace utils
 
}  // namespace cpark
 
#endif  // CPARK_UTILS_H