config_option.h

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/*
  Copyright (c) 2019, 2024, Oracle and/or its affiliates.
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
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  as designated in a particular file or component or in included license
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  permission to link the program and your derivative works with the
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  the program or referenced in the documentation.
 
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
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  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#ifndef MYSQL_HARNESS_CONFIG_OPTION_INCLUDED
#define MYSQL_HARNESS_CONFIG_OPTION_INCLUDED
 
#include <charconv>  // from_chars
#include <chrono>
#include <limits>
#include <stdexcept>
#include <string>
#include <string_view>
#include <type_traits>
 
#include "harness_export.h"
 
namespace mysql_harness {
 
double HARNESS_EXPORT
option_as_double(const std::string &value, const std::string &option_desc,
                 double min_value = 0,
                 double max_value = std::numeric_limits<double>::max());
 
/**
 * Gets an integer using the given option value.
 *
 * Gets an integer using the given option value. The type can be
 * any integer type such as uint16_t, int8_t and bool.
 *
 * The min_value argument can be used to set a minimum value for
 * the option. For example, when 0 (zero) is not allowed, min_value
 * can be set to 1. The maximum value is whatever the maximum of the
 * use type is.
 *
 * Throws std::invalid_argument on errors.
 *
 * @param value Option value
 * @param option_desc Option name
 * @param min_value Minimum value
 * @param max_value Maximum value
 * @return value read from the configuration
 */
template <typename T>
T option_as_int(const std::string_view &value, const std::string &option_desc,
                T min_value = std::numeric_limits<T>::min(),
                T max_value = std::numeric_limits<T>::max()) {
  const char *start = value.data();
  const char *end = start + value.size();
 
  // from_chars has no support for <bool>, map it to uint8_t
  using integral_type = std::conditional_t<std::is_same_v<T, bool>, uint8_t, T>;
 
  integral_type int_result;
  const auto [ptr, ec]{std::from_chars(start, end, int_result)};
 
  if (ptr == end && ec == std::errc{}) {
    // before comparing, cast back to the target_type
    //
    // without the cast, MSVC warns: warning C4804: '<=': unsafe use of type
    // 'bool' in operation
    if (int_result <= static_cast<integral_type>(max_value) &&
        int_result >= static_cast<integral_type>(min_value)) {
      return int_result;
    }
  }
 
  throw std::invalid_argument(option_desc + " needs value between " +
                              std::to_string(min_value) + " and " +
                              std::to_string(max_value) + " inclusive, was '" +
                              std::string(value) + "'");
}
 
/**
 * Get a unsigned integer.
 *
 * use option_as_int<T> instead.
 */
template <typename T>
T option_as_uint(const std::string_view &value, const std::string &option_desc,
                 T min_value = std::numeric_limits<T>::min(),
                 T max_value = std::numeric_limits<T>::max()) {
  return option_as_int<T>(value, option_desc, min_value, max_value);
}
 
template <typename T>
class IntOption {
 public:
  constexpr IntOption(T min_value = std::numeric_limits<T>::min(),
                      T max_value = std::numeric_limits<T>::max())
      : min_value_{min_value}, max_value_{max_value} {}
 
  T operator()(const std::string &value, const std::string &option_desc) {
    return mysql_harness::option_as_int(value, option_desc, min_value_,
                                        max_value_);
  }
 
 private:
  T min_value_;
  T max_value_;
};
 
class StringOption {
 public:
  std::string operator()(const std::string &value,
                         const std::string & /* option_desc */) {
    return value;
  }
};
 
class BoolOption {
 public:
  bool operator()(const std::string &value, const std::string &option_desc) {
    if (value == "true" || value == "1") return true;
    if (value == "false" || value == "0") return false;
 
    throw std::invalid_argument(
        option_desc + " needs a value of either 0, 1, false or true, was '" +
        value + "'");
  }
};
 
template <typename V>
class FloatingPointOption {
 public:
  using value_type = V;
 
  FloatingPointOption(
      value_type min_value = 0,
      value_type max_value = std::numeric_limits<value_type>::max())
      : min_value_{min_value}, max_value_{max_value} {}
 
  value_type operator()(const std::string &value,
                        const std::string &option_desc) {
    return mysql_harness::option_as_double(value, option_desc, min_value_,
                                           max_value_);
  }
 
 private:
  value_type min_value_;
  value_type max_value_;
};
 
using DoubleOption = FloatingPointOption<double>;
 
template <typename Dur>
class DurationOption : public DoubleOption {
 public:
  using duration_type = Dur;
  using __base = DoubleOption;
 
  using __base::__base;
 
  duration_type operator()(const std::string &value,
                           const std::string &option_desc) {
    double result = __base::operator()(value, option_desc);
 
    return std::chrono::duration_cast<std::chrono::milliseconds>(
        std::chrono::duration<double>(result));
  }
};
 
/**
 * a double option with milli-second precision.
 *
 * input is seconds as double.
 * output is a std::chrono::millisecond
 */
using MilliSecondsOption = DurationOption<std::chrono::milliseconds>;
 
}  // namespace mysql_harness
#endif