string_view_utils.hpp

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#ifndef STRING_VIEW_UTILS_183e2da27fe9
#define STRING_VIEW_UTILS_183e2da27fe9
 
#include <string>
#include <string_view>
#include <type_traits>
#include <utility>
#include <stdlib.h>
#include <ctype.h>
 
std::string_view tokenize(std::string_view& str, char delim, char quot = '\0');
 
inline bool sv_contains(std::string_view haystack, std::string_view needle){
        return haystack.find(needle) != std::string_view::npos;
}
 
inline bool sv_is_prefix(std::string_view haystack, std::string_view needle){
    return haystack.compare(0, needle.length(), needle) == 0;
}
 
inline std::string_view sv_trim_whitespace_front(std::string_view sv){
    size_t i = 0;
    while(i < sv.size() && isspace(sv[i])) i++;
 
    return sv.substr(i);
}
 
inline std::string_view sv_trim_whitespace_back(std::string_view sv){
    size_t i = sv.size();
    while(i > 0 && isspace(sv[i - 1])) i--;
 
    return sv.substr(0, i);
}
 
inline std::string_view sv_trim_whitespace(std::string_view sv){
    return sv_trim_whitespace_front(sv_trim_whitespace_back(sv));
}
 
/* std::from_chars is c++17, but on major compilers the feature was missing or 
 * partial (no floating point support). This header provides safe fallbacks
 * if the particular implementation lacks std::from_chars for a given type.
 *
 * std::from_chars support:
 * GCC - partial since v8, floating since v11
 * Clang - partial since 7
 */
#if __has_include(<charconv>)
#include <charconv>
 
template<typename T, typename = void>
struct from_chars_available : std::false_type {  };
 
template<typename T>
struct from_chars_available<T,
        std::void_t<decltype(std::from_chars(std::declval<const char *>(), std::declval<const char *>(), std::declval<T&>()))>>
        : std::true_type {  };
 
template<typename T>
inline constexpr bool from_chars_available_v = from_chars_available<T>::value;
 
template<typename T, std::enable_if_t<from_chars_available_v<T>, bool> = true,
        std::enable_if_t<!std::is_floating_point_v<T>, bool> = true>
bool parse_num(std::string_view sv, T& res, int base = 10){
        return !sv.empty() && std::from_chars(sv.begin(), sv.end(), res, base).ec == std::errc();
}
 
template<typename T, std::enable_if_t<from_chars_available_v<T>, bool> = true,
        std::enable_if_t<std::is_floating_point_v<T>, bool> = true>
bool parse_num(std::string_view sv, T& res){
        return !sv.empty() && std::from_chars(sv.begin(), sv.end(), res).ec == std::errc();
}
 
#else
 
template<typename T>
inline constexpr bool from_chars_available_v = false;
 
#endif // has_include(<charconv>)
 
template<typename T, auto convert, typename... Args>
bool parse_num_fallback_impl(std::string_view sv, T& res, Args... args){
        if(sv.empty())
                return false;
 
        std::string tmp(sv);
        const char *c_str_ptr = tmp.c_str();
        char *endptr = nullptr;
        T num;
 
        num = convert(c_str_ptr, &endptr, args...);
 
        if(c_str_ptr == endptr)
                return false;
 
        res = num;
        return true;
}
 
template<typename T,
        std::enable_if_t<!from_chars_available_v<T>, bool> = true,
        std::enable_if_t<std::is_integral_v<T>, bool> = true>
bool parse_num(std::string_view sv, T& res, int base = 10){
        return parse_num_fallback_impl<T, strtol>(sv, res, base);
}
 
template<typename T,
        std::enable_if_t<!from_chars_available_v<T>, bool> = true,
        std::enable_if_t<std::is_same_v<T, double>, bool> = true>
bool parse_num(std::string_view sv, T& res){
        return parse_num_fallback_impl<T, strtod>(sv, res);
}
 
template<typename T,
        std::enable_if_t<!from_chars_available_v<T>, bool> = true,
        std::enable_if_t<std::is_same_v<T, float>, bool> = true>
bool parse_num(std::string_view sv, T& res){
        return parse_num_fallback_impl<T, strtof>(sv, res);
}
 
#endif