constexpr_string_map.hpp

#pragma once
#include <stdexcept>
#include <string_view>
 
namespace ossia
{
struct small_string
{
  static constexpr int size() { return 64; }
  char arr[64];
  constexpr const char& operator[](int i) const { return arr[i]; }
  constexpr char& operator[](int i) { return arr[i]; }
 
  friend constexpr small_string operator+(small_string lhs, small_string rhs)
  {
    bool past_lhs = false;
    int k = 0;
    for(int i = 0; i < small_string::size(); i++)
    {
      if(lhs[i] == 0)
      {
 
        for(int k = 0; k < small_string::size(); k++)
        {
          if(i + k > small_string::size())
          {
            throw std::runtime_error("string too long");
          }
 
          lhs[i + k] = rhs[k];
        }
      }
    }
    return lhs;
  }
 
  template <std::size_t N>
  friend constexpr small_string operator+(small_string lhs, const char (&rhs)[N])
  {
    bool past_lhs = false;
    int k = 0;
    for(int i = 0; i < size(); i++)
    {
      if(lhs[i] == 0)
      {
        if(i + N > small_string::size())
        {
          throw std::runtime_error("string too long");
        }
 
        for(int k = 0; k < N; k++)
        {
          lhs[i + k] = rhs[k];
        }
      }
    }
    return lhs;
  }
};
 
constexpr small_string to_lower(std::string_view arr)
{
  if(arr.size() > small_string::size())
    throw std::runtime_error("string too long");
 
  small_string s{};
  int i = 0;
  for(; i < arr.size(); i++)
  {
    char in = arr[i];
    if(in <= 'Z' && in >= 'A')
      s[i] = in - ('Z' - 'z');
  }
  s[i + 1] = 0;
  return s;
}
}