helper.hpp

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/*
 
Copyright 2025 | Leong Fan FUNG | funglf | stanleyfunglf@gmail.com
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
 
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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*/
#pragma once
#include <charconv>
#include <string>
#include <string_view>
#include <stdexcept>
#include <cstdint>
 
#include <comppare/internal/config.hpp>
 
namespace comppare::internal::helper
{
    template <typename T>
    T get_arg_value(std::string_view option, const char *nextArg)
    {
        std::string_view valstr;
        if (auto eq = option.find('='); eq != std::string_view::npos)
            valstr = option.substr(eq + 1);
        else if (nextArg)
            valstr = nextArg;
        else
            throw std::invalid_argument(std::string(option) + " requires a value");
 
 
        if constexpr (std::same_as<T, std::string>)
        {
            return std::string(valstr);
        }
        else if constexpr (std::is_integral_v<T>) // if integral type
        {
            size_t idx = 0;
            std::string s{valstr};
 
            if constexpr (std::is_signed_v<T>) // if signed
            {
                long long tmp = std::stoll(s, &idx);
                if (idx != s.size()) // if not all characters were processed
                    throw std::invalid_argument("invalid integer for " + std::string(option));
 
                if (tmp < std::numeric_limits<T>::min() ||
                    tmp > std::numeric_limits<T>::max()) // if out of range for T
                    throw std::out_of_range("integer out of range for " + std::string(option));
 
                return static_cast<T>(tmp);
            }
            else // unsigned
            {
                if (!s.empty() && s.front() == '-') // if negative -- reject
                    throw std::invalid_argument("invalid unsigned integer for " + std::string(option));
 
                unsigned long long tmp = std::stoull(s, &idx);
                if (idx != s.size()) // if not all characters were processed
                    throw std::invalid_argument("invalid unsigned integer for " + std::string(option));
 
                if (tmp > std::numeric_limits<T>::max()) // if out of range for T
                    throw std::out_of_range("unsigned integer out of range for " + std::string(option));
 
                return static_cast<T>(tmp);
            }
        }
        else if constexpr (std::is_floating_point_v<T>)
        {
            size_t idx = 0;
            long double tmp = std::stold(std::string(valstr), &idx);
            if (idx != valstr.size())
                throw std::invalid_argument("invalid floating-point for " + std::string(option));
            return static_cast<T>(tmp);
        }
        else
        {
            static_assert(std::is_arithmetic_v<T> || std::same_as<T, std::string>,
                          "get_arg_value supports only arithmetic types or std::string");
        }
    }
 
    static inline void parse_args(int argc, char **argv)
    {
        if (!argv)
            return;
 
        for (int i = 1; i < argc; ++i)
        {
            std::string_view arg = argv[i];
 
            auto get_next_arg_if_needed = [&](std::string_view a) -> const char *
            {
                return (a.find('=') == std::string_view::npos && i + 1 < argc)
                           ? argv[++i]
                           : nullptr;
            };
 
            if (arg.rfind("--warmup", 0) == 0)
            {
                auto w = get_arg_value<std::uint64_t>(arg, get_next_arg_if_needed(arg));
                comppare::config::set_warmup_iters(w);
            }
            else if (arg.rfind("--iter", 0) == 0)
            {
                auto n = get_arg_value<std::uint64_t>(arg, get_next_arg_if_needed(arg));
                comppare::config::set_bench_iters(n);
            }
            else if (arg.rfind("--tolerance", 0) == 0)
            {
                auto tol = get_arg_value<long double>(arg, get_next_arg_if_needed(arg));
                comppare::config::set_all_fp_tolerance(tol);
            }
        }
    }
} // namespace comppare::internal::helper