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#ifndef FASTFLOAT_PARSE_NUMBER_H
#define FASTFLOAT_PARSE_NUMBER_H
#include "ascii_number.h"
#include "decimal_to_binary.h"
#include "digit_comparison.h"
#include "float_common.h"
#include <cmath>
#include <cstring>
#include <limits>
#include <system_error>
namespace fast_float {
namespace detail {
/**
* Special case +inf, -inf, nan, infinity, -infinity.
* The case comparisons could be made much faster given that we know that the
* strings a null-free and fixed.
**/
template <typename T, typename UC>
from_chars_result_t<UC> FASTFLOAT_CONSTEXPR14
parse_infnan(UC const * first, UC const * last, T &value) noexcept {
from_chars_result_t<UC> answer{};
answer.ptr = first;
answer.ec = std::errc(); // be optimistic
bool minusSign = false;
if (*first == UC('-')) { // assume first < last, so dereference without checks; C++17 20.19.3.(7.1) explicitly forbids '+' here
minusSign = true;
++first;
}
#ifdef FASTFLOAT_ALLOWS_LEADING_PLUS // disabled by default
if (*first == UC('+')) {
++first;
}
#endif
if (last - first >= 3) {
if (fastfloat_strncasecmp(first, str_const_nan<UC>(), 3)) {
answer.ptr = (first += 3);
value = minusSign ? -std::numeric_limits<T>::quiet_NaN() : std::numeric_limits<T>::quiet_NaN();
// Check for possible nan(n-char-seq-opt), C++17 20.19.3.7, C11 7.20.1.3.3. At least MSVC produces nan(ind) and nan(snan).
if(first != last && *first == UC('(')) {
for(UC const * ptr = first + 1; ptr != last; ++ptr) {
if (*ptr == UC(')')) {
answer.ptr = ptr + 1; // valid nan(n-char-seq-opt)
break;
}
else if(!((UC('a') <= *ptr && *ptr <= UC('z')) || (UC('A') <= *ptr && *ptr <= UC('Z')) || (UC('0') <= *ptr && *ptr <= UC('9')) || *ptr == UC('_')))
break; // forbidden char, not nan(n-char-seq-opt)
}
}
return answer;
}
if (fastfloat_strncasecmp(first, str_const_inf<UC>(), 3)) {
if ((last - first >= 8) && fastfloat_strncasecmp(first + 3, str_const_inf<UC>() + 3, 5)) {
answer.ptr = first + 8;
} else {
answer.ptr = first + 3;
}
value = minusSign ? -std::numeric_limits<T>::infinity() : std::numeric_limits<T>::infinity();
return answer;
}
}
answer.ec = std::errc::invalid_argument;
return answer;
}
/**
* Returns true if the floating-pointing rounding mode is to 'nearest'.
* It is the default on most system. This function is meant to be inexpensive.
* Credit : @mwalcott3
*/
fastfloat_really_inline bool rounds_to_nearest() noexcept {
// https://lemire.me/blog/2020/06/26/gcc-not-nearest/
#if (FLT_EVAL_METHOD != 1) && (FLT_EVAL_METHOD != 0)
return false;
#endif
// See
// A fast function to check your floating-point rounding mode
// https://lemire.me/blog/2022/11/16/a-fast-function-to-check-your-floating-point-rounding-mode/
//
// This function is meant to be equivalent to :
// prior: #include <cfenv>
// return fegetround() == FE_TONEAREST;
// However, it is expected to be much faster than the fegetround()
// function call.
//
// The volatile keywoard prevents the compiler from computing the function
// at compile-time.
// There might be other ways to prevent compile-time optimizations (e.g., asm).
// The value does not need to be std::numeric_limits<float>::min(), any small
// value so that 1 + x should round to 1 would do (after accounting for excess
// precision, as in 387 instructions).
static volatile float fmin = std::numeric_limits<float>::min();
float fmini = fmin; // we copy it so that it gets loaded at most once.
//
// Explanation:
// Only when fegetround() == FE_TONEAREST do we have that
// fmin + 1.0f == 1.0f - fmin.
//
// FE_UPWARD:
// fmin + 1.0f > 1
// 1.0f - fmin == 1
//
// FE_DOWNWARD or FE_TOWARDZERO:
// fmin + 1.0f == 1
// 1.0f - fmin < 1
//
// Note: This may fail to be accurate if fast-math has been
// enabled, as rounding conventions may not apply.
#ifdef FASTFLOAT_VISUAL_STUDIO
# pragma warning(push)
// todo: is there a VS warning?
// see https://stackoverflow.com/questions/46079446/is-there-a-warning-for-floating-point-equality-checking-in-visual-studio-2013
#elif defined(__clang__)
# pragma clang diagnostic push
# pragma clang diagnostic ignored "-Wfloat-equal"
#elif defined(__GNUC__)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wfloat-equal"
#endif
return (fmini + 1.0f == 1.0f - fmini);
#ifdef FASTFLOAT_VISUAL_STUDIO
# pragma warning(pop)
#elif defined(__clang__)
# pragma clang diagnostic pop
#elif defined(__GNUC__)
# pragma GCC diagnostic pop
#endif
}
} // namespace detail
template<typename T, typename UC>
FASTFLOAT_CONSTEXPR20
from_chars_result_t<UC> from_chars(UC const * first, UC const * last,
T &value, chars_format fmt /*= chars_format::general*/) noexcept {
return from_chars_advanced(first, last, value, parse_options_t<UC>{fmt});
}
template<typename T, typename UC>
FASTFLOAT_CONSTEXPR20
from_chars_result_t<UC> from_chars_advanced(UC const * first, UC const * last,
T &value, parse_options_t<UC> options) noexcept {
static_assert (std::is_same<T, double>::value || std::is_same<T, float>::value, "only float and double are supported");
static_assert (std::is_same<UC, char>::value ||
std::is_same<UC, wchar_t>::value ||
std::is_same<UC, char16_t>::value ||
std::is_same<UC, char32_t>::value , "only char, wchar_t, char16_t and char32_t are supported");
from_chars_result_t<UC> answer;
#ifdef FASTFLOAT_SKIP_WHITE_SPACE // disabled by default
while ((first != last) && fast_float::is_space(uint8_t(*first))) {
first++;
}
#endif
if (first == last) {
answer.ec = std::errc::invalid_argument;
answer.ptr = first;
return answer;
}
parsed_number_string_t<UC> pns = parse_number_string<UC>(first, last, options);
if (!pns.valid) {
answer.ec = std::errc::invalid_argument;
answer.ptr = first;
return answer;
}
answer.ec = std::errc(); // be optimistic
answer.ptr = pns.lastmatch;
// The implementation of the Clinger's fast path is convoluted because
// we want round-to-nearest in all cases, irrespective of the rounding mode
// selected on the thread.
// We proceed optimistically, assuming that detail::rounds_to_nearest() returns
// true.
if (binary_format<T>::min_exponent_fast_path() <= pns.exponent && pns.exponent <= binary_format<T>::max_exponent_fast_path() && !pns.too_many_digits) {
// Unfortunately, the conventional Clinger's fast path is only possible
// when the system rounds to the nearest float.
//
// We expect the next branch to almost always be selected.
// We could check it first (before the previous branch), but
// there might be performance advantages at having the check
// be last.
if(!cpp20_and_in_constexpr() && detail::rounds_to_nearest()) {
// We have that fegetround() == FE_TONEAREST.
// Next is Clinger's fast path.
if (pns.mantissa <=binary_format<T>::max_mantissa_fast_path()) {
value = T(pns.mantissa);
if (pns.exponent < 0) { value = value / binary_format<T>::exact_power_of_ten(-pns.exponent); }
else { value = value * binary_format<T>::exact_power_of_ten(pns.exponent); }
if (pns.negative) { value = -value; }
return answer;
}
} else {
// We do not have that fegetround() == FE_TONEAREST.
// Next is a modified Clinger's fast path, inspired by Jakub Jelínek's proposal
if (pns.exponent >= 0 && pns.mantissa <=binary_format<T>::max_mantissa_fast_path(pns.exponent)) {
#if defined(__clang__)
// Clang may map 0 to -0.0 when fegetround() == FE_DOWNWARD
if(pns.mantissa == 0) {
value = pns.negative ? -0. : 0.;
return answer;
}
#endif
value = T(pns.mantissa) * binary_format<T>::exact_power_of_ten(pns.exponent);
if (pns.negative) { value = -value; }
return answer;
}
}
}
adjusted_mantissa am = compute_float<binary_format<T>>(pns.exponent, pns.mantissa);
if(pns.too_many_digits && am.power2 >= 0) {
if(am != compute_float<binary_format<T>>(pns.exponent, pns.mantissa + 1)) {
am = compute_error<binary_format<T>>(pns.exponent, pns.mantissa);
}
}
// If we called compute_float<binary_format<T>>(pns.exponent, pns.mantissa) and we have an invalid power (am.power2 < 0),
// then we need to go the long way around again. This is very uncommon.
if(am.power2 < 0) { am = digit_comp<T>(pns, am); }
to_float(pns.negative, am, value);
// Test for over/underflow.
if ((pns.mantissa != 0 && am.mantissa == 0 && am.power2 == 0) || am.power2 == binary_format<T>::infinite_power()) {
answer.ec = std::errc::result_out_of_range;
}
return answer;
}
} // namespace fast_float
#endif
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