cpp-json/json_common.cpp

//
//  json_binder.cpp
//  json
//
//  Created by Sam Jaffe on 4/23/16.
//

#include "json_common.hpp"
#include <map>

namespace json {
  namespace helper {
    namespace {
      std::string get_no_end_error(char expected, char found) {
        char str[64] = { '\0' };
        snprintf(str, sizeof(str),
                 "Expected delimeter: ',' or '%c', got '%c' instead",
                 expected, found);
        return str;
      }
    }
    
    namespace {
      std::map<numeric_token_info::parse_state, uint_jt> bases{
        { numeric_token_info::decimal,     10 },
        { numeric_token_info::octal,        8 },
        { numeric_token_info::hexadecimal, 16 }
      };
      std::map<numeric_token_info::parse_state, std::string> allowed{
        { numeric_token_info::decimal,     "0123456789" },
        { numeric_token_info::octal,       "01234567" },
        { numeric_token_info::hexadecimal, "0123456789aAbBcCdDeEfF" }
      };
      std::map<char, uint_jt> values{
        { '0',  0 }, { '1',  1 }, { '2',  2 }, { '3',  3 },
        { '4',  4 }, { '5',  5 }, { '6',  6 }, { '7',  7 },
        { '8',  8 }, { '9',  9 }, { 'a', 10 }, { 'A', 10 },
        { 'b', 11 }, { 'B', 11 }, { 'c', 12 }, { 'C', 12 },
        { 'd', 13 }, { 'D', 13 }, { 'e', 14 }, { 'E', 14 },
        { 'f', 15 }, { 'F', 15 }
      };
      std::map<numeric_token_info::parse_state, uint_jt> thresholds{
        { numeric_token_info::decimal,     UINT_JT_MAX / 10 },
        { numeric_token_info::octal,       UINT_JT_MAX /  8 },
        { numeric_token_info::hexadecimal, UINT_JT_MAX / 16 }
      };
      std::map<numeric_token_info::parse_state, uint_jt> last_digits{
        { numeric_token_info::decimal,     INT_JT_MAX % 10 },
        { numeric_token_info::octal,       INT_JT_MAX %  8 },
        { numeric_token_info::hexadecimal, INT_JT_MAX % 16 }
      };

    }

    // TODO - parse hex and octal
    numeric_token_info::numeric_token_info(char const * start)
    : val(0)
    , base(decimal)
    , it(start)
    , end(start)
    , is_double(false)
    , is_negative(*start == '-') {
      if ( is_negative ) { ++it; ++end; }
      if ( *end == '0' ) {
        base = octal;
        ++end;
        if (strchr("xX", *end)) {
          base = hexadecimal;
          ++end;
        }
      }
      for (char c = *end;
           !strchr(",]}", c) && !isspace(c);
           c = *++end) {
        is_double |= !strchr(allowed[base].c_str(), c);
      }
      
      if ( is_negative && base != decimal ) {
        throw json_numeric_exception{"Only decimal numbers can be recorded as negative"};
      }
      if (end == it) {
        throw unterminated_json_exception("Expected any token, got nothing");
      }
    }
    
    numeric_state numeric_token_info::parse_numeric() {
      uint_jt const threshold = thresholds[base];
      uint_jt const last_digit = last_digits[base];
      val = 0;
      for (char c = *it; it != end; c = *++it) {
        uint_jt digit = values[c];
        if (val > threshold ||
            ( val == threshold && ((it + 1) < end ||
              digit > last_digit))) {
          return DOUBLE;
        }
        val = (bases[base] * val) + digit;
      }
      return INTEGER;
    }


    const char get_next_element(char const*& data) {
      while (isspace(*data)) ++data;
      return *data;
    }
    
    void advance_to_boundary(char const endtok, char const*& data) {
      char const next = get_next_element(data);
      if (next == ',') {
        ++data;
      } else if (next != endtok) {
        throw json::unterminated_json_exception(get_no_end_error(endtok, *data));
      }
    }
    
    int reverse_count(char const * data, char val) {
      int i = 0;
      while (*data-- == val) { ++i; }
      return i;
    }
    
    std::string replace_all(std::string str, std::string const & from, std::string const & to) {
      std::string::size_type start_pos = 0;
      while((start_pos = str.find(from, start_pos)) != std::string::npos) {
        str.replace(start_pos, from.length(), to);
        start_pos += to.length(); // ...
      }
      return std::move(str);
    }
    
    std::string parse_string(char const * & data) {
      char const* start = data;
      while (*++data) {
        if (*data == '"' && (reverse_count(data-1, '\\') % 2) == 0) {
          return replace_all(std::string(start+1, data++), "\\\"", "\"");
        }
      }
      throw json::unterminated_json_exception("Could not locate end of string");
    }
  }
}