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Workaround for missing or partially implemented std::from_chars()

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This commit is contained in:
Vojtech Bubnik 2020-10-29 11:31:59 +01:00
parent d2e5be89e3
commit 9f11cab092
1 changed files with 42 additions and 5 deletions
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43
src/libslic3r/GCode/GCodeProcessor.cpp
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@ -9,7 +9,10 @@
#include <float.h>
#include <assert.h>
#if __has_include(<charconv>)
#include <charconv>
#endif
#if ENABLE_GCODE_VIEWER
#include <chrono>
@ -947,14 +950,48 @@ static inline bool starts_with(const std::string_view comment, const std::string
return comment.size() >= tag_len && comment.substr(0, tag_len) == tag;
}
#if __has_include(<charconv>)
template <typename T, typename = void>
struct is_from_chars_convertible : std::false_type {};
template <typename T>
struct is_from_chars_convertible<T, std::void_t<decltype(std::from_chars(declval<const char*>(), declval<const char*>(), declval<T&>()))>> : std::true_type {};
#endif
// Returns true if the number was parsed correctly into out and the number spanned the whole input string.
template<typename T>
static inline bool parse_number(const std::string_view str, T &out)
[[nodiscard]] static inline bool parse_number(const std::string_view sv, T &out)
{
auto str_end = str.data() + str.size();
auto [end_ptr, error_code] = std::from_chars(str.data(), str_end, out);
// https://www.bfilipek.com/2019/07/detect-overload-from-chars.html#example-stdfromchars
#if __has_include(<charconv>)
// Visual Studio 19 supports from_chars all right.
// OSX compiler that we use only implements std::from_chars just for ints.
// GCC that we compile on does not provide <charconv> at all.
if constexpr (is_from_chars_convertible<T>::value) {
auto str_end = sv.data() + sv.size();
auto [end_ptr, error_code] = std::from_chars(sv.data(), str_end, out);
return error_code == std::errc() && end_ptr == str_end;
}
else
#endif
{
// Legacy conversion, which is costly due to having to make a copy of the string before conversion.
try {
std::string str { str };
size_t read = 0;
if constexpr (std::is_same_v<T, int>)
out = std::stoi(str, &read);
else if constexpr (std::is_same_v<T, long>)
out = std::stol(str, &read);
else if constexpr (std::is_same_v<T, float>)
out = std::stof(str, &read);
else if constexpr (std::is_same_v<T, double>)
out = std::stod(str, &read);
return str.size() == read;
} catch (...) {
return false;
}
}
}
void GCodeProcessor::process_tags(const std::string_view comment)
{