__floating_point_formatter.h

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#pragma once
#if !defined(__XTD_CORE_INTERNAL__)
#error "Do not include this file: Internal use only"
#endif
 
#include "__binary_formatter.h"
#include "__character_formatter.h"
#include "__currency_formatter.h"
#include "__format_exception.h"
#include "__hexfloat_formatter.h"
#include "__natural_formatter.h"
#include "__sprintf.h"
#include <algorithm>
#include <cstring>
#include <vector>
 
template<typename char_t, typename value_t>
inline std::basic_string<char_t> __floating_point_formatter(const std::basic_string<char_t>& format, value_t value, const std::locale& loc) {
  auto fmt = format;
  if (fmt.empty()) fmt = {'G'};
  
  std::vector<char_t> possible_formats {'b', 'B', 'c', 'C', 'e', 'E', 'f', 'F', 'g', 'G', 'n', 'N', 'p', 'P', 'x', 'X'};
  if (fmt.size() > 3 || std::find(possible_formats.begin(), possible_formats.end(), fmt[0]) == possible_formats.end() || (fmt.size() >= 2 && !std::isdigit(fmt[1])) || (fmt.size() == 3 && !std::isdigit(fmt[2])))
    __format_exception("Custom format not yet implemented");
    
  int precision = 0;
  try {
    if (fmt.size() > 1) precision = std::stoi(fmt.substr(1));
  } catch (...) {
    __format_exception("Invalid format expression");
  }
  if ((fmt[0] == 'f' || fmt[0] == 'F' || fmt[0] == 'n' || fmt[0] == 'N' || fmt[0] == 'p' || fmt[0] == 'P' || fmt[0] == 'r' || fmt[0] == 'R') && fmt.size() == 1) precision = 2;
  if ((fmt[0] == 'e' || fmt[0] == 'E') && fmt.size() == 1) precision = 6;
  if ((fmt[0] == 'g' || fmt[0] == 'G') && fmt.size() == 1) precision = sizeof(value) <= 4 ? 7 : 15;
  
  std::basic_string<char_t> fmt_str({'%', '.', '*', 'L'});
  switch (fmt[0]) {
    case 'b':
    case 'B': {double value_double = static_cast<double>(value); int64_t value_int64 = 0; memcpy(&value_int64, &value_double, sizeof(value_double)); return __binary_formatter<char_t>(value_int64, precision);}
    case 'c':
    case 'C': return __currency_formatter<char_t>(static_cast<long double>(value), loc);
    case 'e':
    case 'E':
    case 'f':
    case 'F':
    case 'g':
    case 'G': return __sprintf((fmt_str + fmt[0]).c_str(), precision, static_cast<long double>(value));
    case 'n':
    case 'N': return __natural_formatter<char_t>(static_cast<long double>(value), precision, loc);
    case 'p': return __sprintf((fmt_str + char_t('f')).c_str(), precision, static_cast<long double>(value * 100)) + std::basic_string<char_t>({char_t(' '), char_t('%')});
    case 'P': return __sprintf((fmt_str + char_t('F')).c_str(), precision, static_cast<long double>(value * 100)) + std::basic_string<char_t>({char_t(' '), char_t('%')});
    case 'x':
    case 'X': return __hexfloat_formatter<char_t>(static_cast<long double>(value), precision, loc);
    default: __format_exception("Invalid format expression"); return {};
  }
}