cpp-json/json_common.hpp

//
//  json_common.h
//  json
//
//  Created by Sam Jaffe on 4/22/16.
//

#pragma once

#include <cstdint>
#include <cstdlib>
#include <stdexcept>
#include <string>

namespace json {
  using string_jt = std::string;
  using double_jt = double;
  using int_jt = int32_t;
  using uint_jt = uint32_t;
  using bool_jt = bool;
  
  class value;
  
  class malformed_json_exception :
  public std::domain_error {
    using std::domain_error::domain_error;
  };
  
  class unterminated_json_exception :
  public malformed_json_exception {
    using malformed_json_exception::malformed_json_exception;
  };
  
  class json_numeric_exception :
  public std::domain_error {
    using std::domain_error::domain_error;
  };

  class json_numeric_width_exception :
  public json_numeric_exception {
    using json_numeric_exception::json_numeric_exception;
  };

  namespace {
    const constexpr json::int_jt INT_JT_MAX = std::numeric_limits<json::int_jt>::max();
    const constexpr json::int_jt INT_JT_MAX_LAST_DIGIT = (INT_JT_MAX % 10);
    const constexpr json::int_jt INT_JT_MIN = std::numeric_limits<json::int_jt>::min();
    const constexpr json::uint_jt INT_JT_OVER = json::uint_jt(INT_JT_MAX) + 1;
    const constexpr json::uint_jt UINT_JT_MAX = json::uint_jt(0) - 1;
    //  const constexpr json::uint_jt UINT_JT_MIN = 0;
  }
}

namespace json { namespace parser {
  enum options {
    allow_all                        = 0x00,
    disable_unknown_keys             = 0x01,
    disable_concatenated_json_bodies = 0x02,
    disable_all                      = 0xFF,
  };
} }

namespace json { namespace helper {
  const char get_next_element(char const*& data);
  
  enum numeric_state {
    DOUBLE, INTEGER
  };
  
  struct numeric_token_info {
    numeric_token_info(char const * start);
    numeric_state parse_numeric();
    
    uint_jt val;
    
    char const * it;
    char const * end;
    bool is_double;
    bool is_negative;
  };
  
  numeric_token_info get_numeric_token_info(char const * it);
  
  /**
   * @throws json::malformed_json_exception
   */
  void advance_to_boundary(char const endtok, char const *& data);
  
  /**
   * @throws json::malformed_json_exception
   */
  std::string parse_string(char const * & data);
  
  template <typename T>
  void parse_string(T& json, char const * & data) {
    json = parse_string(data);
  }
  
  template <typename T>
  void parse_double_impl(T & json, char const * begin, char const * end) {
    json = std::stod(std::string(begin, end));
  }
  template <>
  inline void parse_double_impl<float>(float & json, char const * begin, char const * end) {
    json = std::stof(std::string(begin, end));
  }
  template <>
  inline void parse_double_impl<long double>(long double & json, char const * begin, char const * end) {
    json = std::stold(std::string(begin, end));
  }
  
  template <typename T>
  void parse_double(T& json, char const * & data) {
    char const * begin = data;
    if (*data == '-') { ++data; }
    while (isdigit(*data) || *data == '-') { ++data; }
    if (*data == '.') { ++data; }
    else if (begin != data && (*data == 'e' || *data == 'E')) {
      ++data;
      if (*data == '-') { ++data; }
    }
    while (isdigit(*data)) { ++data; }
    if ( begin == data ) {
      throw json::json_numeric_exception{"Expected numeric data"};
    }
    try {
      parse_double_impl(json, begin, data);
    } catch (std::domain_error const &) {
      throw json::json_numeric_exception{"Expected a numeric type"};
    } catch (std::out_of_range const &) {
      throw json::json_numeric_width_exception{"Number is out-of-range for floating-point type"};
    }
  }
  
  template <typename J>
  void parse_numeric(J & json, char const * & data) {
    if (std::is_floating_point<J>::value) {
      helper::parse_double(json, data);
      return;
    }
    numeric_token_info info = data;
    
    if ( info.is_double || info.parse_numeric() == DOUBLE ) {
      if (std::is_integral<J>::value) {
        throw json::json_numeric_exception{"Expected integer, got double"};
      }
      helper::parse_double(json, data);
    } else {
      uint_jt const val = info.val;
      
      if (fls(val) > std::numeric_limits<J>::digits + info.is_negative) {
        throw json::json_numeric_width_exception{"Integer width too small for parsed value"};
      }

      if (info.is_negative) {
        if (!std::is_signed<J>::value) {
          throw json::json_numeric_exception{"Expected signed integer"};
        }
        if (val == INT_JT_OVER) {
          json = (J) INT_JT_MIN; // Cast suppresses error message, narrowing check above makes safe
        } else {
          json = -int_jt(val);
        }
      } else if (val <= uint_jt(INT_JT_MAX)) {
        json = int_jt(val);
      } else if (std::is_signed<J>::value) {
        throw json::json_numeric_exception{"Expected unsigned integer"};
      } else {
        json = val;
      }
      data = info.it;
    }
  }
} }