// std::from_chars implementation for floating-point types -*- C++ -*-
-// Copyright (C) 2020 Free Software Foundation, Inc.
+// Copyright (C) 2020-2023 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// 23.2.9 Primitive numeric input conversion [utility.from.chars]
//
+// Prefer to use std::pmr::string if possible, which requires the cxx11 ABI.
+#define _GLIBCXX_USE_CXX11_ABI 1
+
+#include <array>
#include <charconv>
+#include <bit>
#include <string>
#include <memory_resource>
#include <cfenv>
+#include <cfloat>
#include <cmath>
#include <cstdlib>
#include <cstring>
-#include <cctype>
#include <locale.h>
#include <bits/functexcept.h>
#if _GLIBCXX_HAVE_XLOCALE_H
#endif
#if _GLIBCXX_HAVE_USELOCALE
+// FIXME: This should be reimplemented so it doesn't use strtod and newlocale.
+// That will avoid the need for any memory allocation, meaning that the
+// non-conforming errc::not_enough_memory result cannot happen.
+# define USE_STRTOD_FOR_FROM_CHARS 1
+#endif
+
+#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
+#ifndef __LONG_DOUBLE_IBM128__
+#error "floating_from_chars.cc must be compiled with -mabi=ibmlongdouble"
+#endif
+// strtold for __ieee128
+extern "C" __ieee128 __strtoieee128(const char*, char**);
+#elif __FLT128_MANT_DIG__ == 113 && __LDBL_MANT_DIG__ != 113 \
+ && defined(__GLIBC_PREREQ)
+#define USE_STRTOF128_FOR_FROM_CHARS 1
+extern "C" _Float128 __strtof128(const char*, char**)
+ __asm ("strtof128")
+#ifndef _GLIBCXX_HAVE_FLOAT128_MATH
+ __attribute__((__weak__))
+#endif
+ ;
+#endif
+
+#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 \
+ && __SIZE_WIDTH__ >= 32
+# define USE_LIB_FAST_FLOAT 1
+# if __LDBL_MANT_DIG__ == __DBL_MANT_DIG__
+// No need to use strtold.
+# undef USE_STRTOD_FOR_FROM_CHARS
+# endif
+#endif
+
+#if USE_LIB_FAST_FLOAT
+# define FASTFLOAT_DEBUG_ASSERT __glibcxx_assert
+namespace
+{
+# include "fast_float/fast_float.h"
+
+namespace fast_float
+{
+
+ // Wrappers around float for std::{,b}float16_t promoted to float.
+ struct floating_type_float16_t
+ {
+ float* x;
+ uint16_t bits;
+ };
+ struct floating_type_bfloat16_t
+ {
+ float* x;
+ uint16_t bits;
+ };
+
+ template<>
+ constexpr int
+ binary_format<floating_type_float16_t>::mantissa_explicit_bits()
+ { return 10; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_bfloat16_t>::mantissa_explicit_bits()
+ { return 7; }
+
+ // 10 bits of stored mantissa, pow(5,q) <= 0x4p+10 implies q <= 5
+ template<>
+ constexpr int
+ binary_format<floating_type_float16_t>::max_exponent_round_to_even()
+ { return 5; }
+
+ // 7 bits of stored mantissa, pow(5,q) <= 0x4p+7 implies q <= 3
+ template<>
+ constexpr int
+ binary_format<floating_type_bfloat16_t>::max_exponent_round_to_even()
+ { return 3; }
+
+ // 10 bits of stored mantissa, pow(5,-q) < 0x1p+64 / 0x1p+11 implies q >= -22
+ template<>
+ constexpr int
+ binary_format<floating_type_float16_t>::min_exponent_round_to_even()
+ { return -22; }
+
+ // 7 bits of stored mantissa, pow(5,-q) < 0x1p+64 / 0x1p+8 implies q >= -24
+ template<>
+ constexpr int
+ binary_format<floating_type_bfloat16_t>::min_exponent_round_to_even()
+ { return -24; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_float16_t>::minimum_exponent()
+ { return -15; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_bfloat16_t>::minimum_exponent()
+ { return -127; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_float16_t>::infinite_power()
+ { return 0x1F; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_bfloat16_t>::infinite_power()
+ { return 0xFF; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_float16_t>::sign_index()
+ { return 15; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_bfloat16_t>::sign_index()
+ { return 15; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_float16_t>::largest_power_of_ten()
+ { return 4; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_bfloat16_t>::largest_power_of_ten()
+ { return 38; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_float16_t>::smallest_power_of_ten()
+ { return -27; }
+
+ template<>
+ constexpr int
+ binary_format<floating_type_bfloat16_t>::smallest_power_of_ten()
+ { return -60; }
+
+ template<>
+ constexpr size_t
+ binary_format<floating_type_float16_t>::max_digits()
+ { return 22; }
+
+ template<>
+ constexpr size_t
+ binary_format<floating_type_bfloat16_t>::max_digits()
+ { return 98; }
+
+ // negative_digit_comp converts adjusted_mantissa to the (originally only)
+ // floating type and immediately back with slight tweaks (e.g. explicit
+ // leading bit instead of implicit for normals).
+ // Avoid going through the floating point type.
+ template<>
+ fastfloat_really_inline void
+ to_float<floating_type_float16_t>(bool negative, adjusted_mantissa am,
+ floating_type_float16_t &value)
+ {
+ constexpr int mantissa_bits
+ = binary_format<floating_type_float16_t>::mantissa_explicit_bits();
+ value.bits = (am.mantissa
+ | (uint16_t(am.power2) << mantissa_bits)
+ | (negative ? 0x8000 : 0));
+ }
+
+ template<>
+ fastfloat_really_inline void
+ to_float<floating_type_bfloat16_t>(bool negative, adjusted_mantissa am,
+ floating_type_bfloat16_t &value)
+ {
+ constexpr int mantissa_bits
+ = binary_format<floating_type_bfloat16_t>::mantissa_explicit_bits();
+ value.bits = (am.mantissa
+ | (uint16_t(am.power2) << mantissa_bits)
+ | (negative ? 0x8000 : 0));
+ }
+
+ template <>
+ fastfloat_really_inline adjusted_mantissa
+ to_extended<floating_type_float16_t>(floating_type_float16_t value) noexcept
+ {
+ adjusted_mantissa am;
+ constexpr int mantissa_bits
+ = binary_format<floating_type_float16_t>::mantissa_explicit_bits();
+ int32_t bias
+ = (mantissa_bits
+ - binary_format<floating_type_float16_t>::minimum_exponent());
+ constexpr uint16_t exponent_mask = 0x7C00;
+ constexpr uint16_t mantissa_mask = 0x03FF;
+ constexpr uint16_t hidden_bit_mask = 0x0400;
+ if ((value.bits & exponent_mask) == 0) {
+ // denormal
+ am.power2 = 1 - bias;
+ am.mantissa = value.bits & mantissa_mask;
+ } else {
+ // normal
+ am.power2 = int32_t((value.bits & exponent_mask) >> mantissa_bits);
+ am.power2 -= bias;
+ am.mantissa = (value.bits & mantissa_mask) | hidden_bit_mask;
+ }
+ return am;
+ }
+
+ template <>
+ fastfloat_really_inline adjusted_mantissa
+ to_extended<floating_type_bfloat16_t>(floating_type_bfloat16_t value) noexcept
+ {
+ adjusted_mantissa am;
+ constexpr int mantissa_bits
+ = binary_format<floating_type_bfloat16_t>::mantissa_explicit_bits();
+ int32_t bias
+ = (mantissa_bits
+ - binary_format<floating_type_bfloat16_t>::minimum_exponent());
+ constexpr uint16_t exponent_mask = 0x7F80;
+ constexpr uint16_t mantissa_mask = 0x007F;
+ constexpr uint16_t hidden_bit_mask = 0x0080;
+ if ((value.bits & exponent_mask) == 0) {
+ // denormal
+ am.power2 = 1 - bias;
+ am.mantissa = value.bits & mantissa_mask;
+ } else {
+ // normal
+ am.power2 = int32_t((value.bits & exponent_mask) >> mantissa_bits);
+ am.power2 -= bias;
+ am.mantissa = (value.bits & mantissa_mask) | hidden_bit_mask;
+ }
+ return am;
+ }
+
+ // Like fast_float.h from_chars_advanced, but for 16-bit float.
+ template<typename T>
+ from_chars_result
+ from_chars_16(const char* first, const char* last, T &value,
+ chars_format fmt) noexcept
+ {
+ parse_options options{fmt};
+
+ from_chars_result answer;
+ if (first == last)
+ {
+ answer.ec = std::errc::invalid_argument;
+ answer.ptr = first;
+ return answer;
+ }
+
+ parsed_number_string pns = parse_number_string(first, last, options);
+ if (!pns.valid)
+ return detail::parse_infnan(first, last, *value.x);
+
+ answer.ec = std::errc();
+ answer.ptr = pns.lastmatch;
+
+ 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);
+
+ if ((pns.mantissa != 0 && am.mantissa == 0 && am.power2 == 0)
+ || am.power2 == binary_format<T>::infinite_power())
+ {
+ // In case of over/underflow, return result_out_of_range and don't
+ // modify value, as per [charconv.from.chars]/1. Note that LWG 3081 wants
+ // to modify value in this case too.
+ answer.ec = std::errc::result_out_of_range;
+ return answer;
+ }
+
+ // Transform the {,b}float16_t to float32_t before to_float.
+ if constexpr (std::is_same_v<T, floating_type_float16_t>)
+ {
+ if (am.power2 == 0)
+ {
+ if (am.mantissa)
+ {
+ int n = (std::numeric_limits<unsigned int>::digits
+ - __builtin_clz (am.mantissa)) - 1;
+ am.mantissa &= ~(static_cast<decltype(am.mantissa)>(1) << n);
+ am.mantissa <<= (binary_format<float>::mantissa_explicit_bits()
+ - n);
+ am.power2 = n + 0x67;
+ }
+ }
+ else
+ {
+ am.mantissa <<= 13;
+ am.power2 += 0x70;
+ }
+ }
+ else
+ am.mantissa <<= 16;
+ to_float(pns.negative, am, *value.x);
+ return answer;
+ }
+} // fast_float
+
+} // anon namespace
+#endif
+
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace
{
+#if USE_STRTOD_FOR_FROM_CHARS
// A memory resource with a static buffer that can be used for small
// allocations. At most one allocation using the freestore can be done
// if the static buffer is insufficient. The callers below only require
return m_buf + std::__exchange(m_bytes, m_bytes + bytes);
__glibcxx_assert(m_ptr == nullptr);
- __glibcxx_assert(alignment != 1);
m_ptr = operator new(bytes);
m_bytes = bytes;
void* m_ptr = nullptr;
};
+#if _GLIBCXX_USE_CXX11_ABI
+ using buffered_string = std::pmr::string;
+#else
+ using buffered_string = std::string;
+#endif
+
inline bool valid_fmt(chars_format fmt)
{
return fmt != chars_format{}
// Find initial portion of [first, last) containing a floating-point number.
// The string `digits` is either `dec_digits` or `hex_digits`
- // and `exp` is 'e' or 'p' or '\0'.
+ // and `exp` is "eE", "pP" or NULL.
const char*
find_end_of_float(const char* first, const char* last, const char* digits,
- char exp)
+ const char *exp)
{
while (first < last && strchr(digits, *first) != nullptr)
++first;
while (first < last && strchr(digits, *first))
++first;
}
- if (first < last && exp != 0 && std::tolower((unsigned char)*first) == exp)
+ if (first < last && exp != nullptr && (*first == exp[0] || *first == exp[1]))
{
++first;
if (first < last && (*first == '-' || *first == '+'))
// Returns a nullptr if a valid pattern is not present.
const char*
pattern(const char* const first, const char* last,
- chars_format& fmt, pmr::string& buf)
+ chars_format& fmt, buffered_string& buf)
{
// fmt has the value of one of the enumerators of chars_format.
__glibcxx_assert(valid_fmt(fmt));
if ((last - first + 2) > buffer_resource::guaranteed_capacity())
{
- last = find_end_of_float(first + neg, last, digits, 'p');
+ last = find_end_of_float(first + neg, last, digits, "pP");
#ifndef __cpp_exceptions
if ((last - first + 2) > buffer_resource::guaranteed_capacity())
{
if ((last - first) > buffer_resource::guaranteed_capacity())
{
last = find_end_of_float(first + neg, last, digits,
- "e"[fmt == chars_format::fixed]);
+ fmt == chars_format::fixed ? nullptr : "eE");
#ifndef __cpp_exceptions
if ((last - first) > buffer_resource::guaranteed_capacity())
{
ptrdiff_t
from_chars_impl(const char* str, T& value, errc& ec) noexcept
{
- if (locale_t loc = ::newlocale(LC_ALL, "C", (locale_t)0)) [[likely]]
+ if (locale_t loc = ::newlocale(LC_ALL_MASK, "C", (locale_t)0)) [[likely]]
{
locale_t orig = ::uselocale(loc);
-#if _GLIBCXX_USE_C99_FENV_TR1
+#if _GLIBCXX_USE_C99_FENV_TR1 && defined(FE_TONEAREST)
const int rounding = std::fegetround();
if (rounding != FE_TONEAREST)
std::fesetround(FE_TONEAREST);
tmpval = std::strtod(str, &endptr);
else if constexpr (is_same_v<T, long double>)
tmpval = std::strtold(str, &endptr);
+# ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
+ else if constexpr (is_same_v<T, __ieee128>)
+ tmpval = __strtoieee128(str, &endptr);
+# elif defined(USE_STRTOF128_FOR_FROM_CHARS)
+ else if constexpr (is_same_v<T, _Float128>)
+ {
+#ifndef _GLIBCXX_HAVE_FLOAT128_MATH
+ if (&__strtof128 == nullptr)
+ tmpval = _Float128(std::strtold(str, &endptr));
+ else
+#endif
+ tmpval = __strtof128(str, &endptr);
+ }
+# endif
#else
tmpval = std::strtod(str, &endptr);
#endif
const int conv_errno = std::__exchange(errno, save_errno);
-#if _GLIBCXX_USE_C99_FENV_TR1
+#if _GLIBCXX_USE_C99_FENV_TR1 && defined(FE_TONEAREST)
if (rounding != FE_TONEAREST)
std::fesetround(rounding);
#endif
const ptrdiff_t n = endptr - str;
if (conv_errno == ERANGE) [[unlikely]]
{
- if (isinf(tmpval)) // overflow
+ if (__builtin_isinf(tmpval)) // overflow
ec = errc::result_out_of_range;
- else // underflow (LWG 3081 wants to set value = tmpval here)
+ else if (tmpval == 0) // underflow (LWG 3081 wants to set value = tmpval here)
ec = errc::result_out_of_range;
+ else // denormal value
+ {
+ value = tmpval;
+ ec = errc();
+ }
}
else if (n)
{
return result;
}
+#if ! _GLIBCXX_USE_CXX11_ABI
+ inline bool
+ reserve_string(std::string& s) noexcept
+ {
+ __try
+ {
+ s.reserve(buffer_resource::guaranteed_capacity());
+ }
+ __catch (const std::bad_alloc&)
+ {
+ return false;
+ }
+ return true;
+ }
+#endif
+
+ template<typename T>
+ from_chars_result
+ from_chars_strtod(const char* first, const char* last, T& value,
+ chars_format fmt) noexcept
+ {
+ errc ec = errc::invalid_argument;
+#if _GLIBCXX_USE_CXX11_ABI
+ buffer_resource mr;
+ pmr::string buf(&mr);
+#else
+ string buf;
+ if (!reserve_string(buf))
+ return make_result(first, 0, {}, ec);
+#endif
+ size_t len = 0;
+ __try
+ {
+ if (const char* pat = pattern(first, last, fmt, buf)) [[likely]]
+ len = from_chars_impl(pat, value, ec);
+ }
+ __catch (const std::bad_alloc&)
+ {
+ fmt = chars_format{};
+ }
+ return make_result(first, len, fmt, ec);
+ }
+#endif // USE_STRTOD_FOR_FROM_CHARS
+
+#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
+ // Return true iff [FIRST,LAST) begins with PREFIX, ignoring case.
+ // PREFIX is assumed to not contain any uppercase letters.
+ bool
+ starts_with_ci(const char* first, const char* last, string_view prefix)
+ {
+ __glibcxx_requires_valid_range(first, last);
+
+ // A lookup table that maps uppercase letters to lowercase and
+ // is otherwise the identity mapping.
+ static constexpr auto upper_to_lower_table = [] {
+ constexpr unsigned char lower_letters[27] = "abcdefghijklmnopqrstuvwxyz";
+ constexpr unsigned char upper_letters[27] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+ std::array<unsigned char, (1u << __CHAR_BIT__)> table = {};
+ for (unsigned i = 0; i < table.size(); ++i)
+ table[i] = i;
+ for (unsigned i = 0; i < 26; ++i)
+ table[upper_letters[i]] = lower_letters[i];
+ return table;
+ }();
+
+ if (last - first < static_cast<ptrdiff_t>(prefix.length()))
+ return false;
+
+ for (const unsigned char pch : prefix)
+ {
+ // __glibcxx_assert(pch == upper_to_lower_table[pch]);
+ const unsigned char ch = *first;
+ if (ch != pch && upper_to_lower_table[ch] != pch)
+ return false;
+ ++first;
+ }
+
+ return true;
+ }
+
+ // An implementation of hexadecimal float parsing for binary32/64.
+ template<typename T>
+ from_chars_result
+ __floating_from_chars_hex(const char* first, const char* last, T& value)
+ {
+ using uint_t = conditional_t<is_same_v<T, float>, uint32_t,
+ conditional_t<is_same_v<T, double>, uint64_t,
+ uint16_t>>;
+#if USE_LIB_FAST_FLOAT
+ constexpr int mantissa_bits
+ = fast_float::binary_format<T>::mantissa_explicit_bits();
+ constexpr int exponent_bits
+ = is_same_v<T, double> ? 11
+ : is_same_v<T, fast_float::floating_type_float16_t> ? 5 : 8;
+#else
+ constexpr int mantissa_bits = is_same_v<T, float> ? 23 : 52;
+ constexpr int exponent_bits = is_same_v<T, float> ? 8 : 11;
+#endif
+ constexpr int exponent_bias = (1 << (exponent_bits - 1)) - 1;
+
+ __glibcxx_requires_valid_range(first, last);
+ if (first == last)
+ return {first, errc::invalid_argument};
+
+ // Consume the sign bit.
+ const char* const orig_first = first;
+ bool sign_bit = false;
+ if (*first == '-')
+ {
+ sign_bit = true;
+ ++first;
+ }
+
+ // Handle "inf", "infinity", "NaN" and variants thereof.
+ if (first != last)
+ if (*first == 'i' || *first == 'I' || *first == 'n' || *first == 'N') [[unlikely]]
+ {
+ if (starts_with_ci(first, last, "inf"sv))
+ {
+ first += strlen("inf");
+ if (starts_with_ci(first, last, "inity"sv))
+ first += strlen("inity");
+
+ if constexpr (is_same_v<T, float> || is_same_v<T, double>)
+ {
+ uint_t result = 0;
+ result |= sign_bit;
+ result <<= exponent_bits;
+ result |= (1ull << exponent_bits) - 1;
+ result <<= mantissa_bits;
+ memcpy(&value, &result, sizeof(result));
+ }
+ else
+ {
+ // float +/-Inf.
+ uint32_t result = 0x7F800000 | (sign_bit ? 0x80000000U : 0);
+ memcpy(value.x, &result, sizeof(result));
+ }
+
+ return {first, errc{}};
+ }
+ else if (starts_with_ci(first, last, "nan"))
+ {
+ first += strlen("nan");
+
+ if (first != last && *first == '(')
+ {
+ // Tentatively consume the '(' as we look for an optional
+ // n-char-sequence followed by a ')'.
+ const char* const fallback_first = first;
+ for (;;)
+ {
+ ++first;
+ if (first == last)
+ {
+ first = fallback_first;
+ break;
+ }
+
+ char ch = *first;
+ if (ch == ')')
+ {
+ ++first;
+ break;
+ }
+ else if (ch == '_'
+ || __detail::__from_chars_alnum_to_val(ch) < 127)
+ continue;
+ else
+ {
+ first = fallback_first;
+ break;
+ }
+ }
+ }
+
+ // We make the implementation-defined decision of ignoring the
+ // sign bit and the n-char-sequence when assembling the NaN.
+ if constexpr (is_same_v<T, float> || is_same_v<T, double>)
+ {
+ uint_t result = 0;
+ result <<= exponent_bits;
+ result |= (1ull << exponent_bits) - 1;
+ result <<= mantissa_bits;
+ result |= (1ull << (mantissa_bits - 1)) | 1;
+ memcpy(&value, &result, sizeof(result));
+ }
+ else
+ {
+ // float qNaN.
+ uint32_t result = 0x7FC00001;
+ memcpy(value.x, &result, sizeof(result));
+ }
+
+ return {first, errc{}};
+ }
+ }
+
+ // Consume all insignificant leading zeros in the whole part of the
+ // mantissa.
+ bool seen_hexit = false;
+ while (first != last && *first == '0')
+ {
+ seen_hexit = true;
+ ++first;
+ }
+
+ // Now consume the rest of the written mantissa, populating MANTISSA with
+ // the first MANTISSA_BITS+k significant bits of the written mantissa, where
+ // 1 <= k <= 4 is the bit width of the leading significant written hexit.
+ //
+ // Examples:
+ // After parsing "1.2f3", MANTISSA is 0x12f30000000000 (bit_width=52+1).
+ // After parsing ".0000f0e", MANTISSA is 0xf0e00000000000 (bit_width=52+4).
+ // After parsing ".1234567890abcd8", MANTISSA is 0x1234567890abcd (bit_width=52+1)
+ // and MIDPOINT_BIT is true (and NONZERO_TAIL is false).
+ uint_t mantissa = 0;
+ int mantissa_idx = mantissa_bits; // The current bit index into MANTISSA
+ // into which we'll write the next hexit.
+ int exponent_adjustment = 0; // How much we'd have to adjust the written
+ // exponent in order to represent the mantissa
+ // in scientific form h.hhhhhhhhhhhhh.
+ bool midpoint_bit = false; // Whether the MANTISSA_BITS+k+1 significant
+ // bit is set in the written mantissa.
+ bool nonzero_tail = false; // Whether some bit thereafter is set in the
+ // written mantissa.
+ bool seen_decimal_point = false;
+ for (; first != last; ++first)
+ {
+ char ch = *first;
+ if (ch == '.' && !seen_decimal_point)
+ {
+ seen_decimal_point = true;
+ continue;
+ }
+
+ int hexit = __detail::__from_chars_alnum_to_val(ch);
+ if (hexit >= 16)
+ break;
+ seen_hexit = true;
+
+ if (!seen_decimal_point && mantissa != 0)
+ exponent_adjustment += 4;
+ else if (seen_decimal_point && mantissa == 0)
+ {
+ exponent_adjustment -= 4;
+ if (hexit == 0x0)
+ continue;
+ }
+
+ if (mantissa_idx >= 0)
+ mantissa |= uint_t(hexit) << mantissa_idx;
+ else if (mantissa_idx >= -4)
+ {
+ if constexpr (is_same_v<T, float>
+#if USE_LIB_FAST_FLOAT
+ || is_same_v<T,
+ fast_float::floating_type_bfloat16_t>
+#endif
+ )
+ {
+ __glibcxx_assert(mantissa_idx == -1);
+ mantissa |= hexit >> 1;
+ midpoint_bit = (hexit & 0b0001) != 0;
+ }
+ else if constexpr (is_same_v<T, double>)
+ {
+ __glibcxx_assert(mantissa_idx == -4);
+ midpoint_bit = (hexit & 0b1000) != 0;
+ nonzero_tail = (hexit & 0b0111) != 0;
+ }
+ else
+ {
+ __glibcxx_assert(mantissa_idx == -2);
+ mantissa |= hexit >> 2;
+ midpoint_bit = (hexit & 0b0010) != 0;
+ nonzero_tail = (hexit & 0b0001) != 0;
+ }
+ }
+ else
+ nonzero_tail |= (hexit != 0x0);
+
+ mantissa_idx -= 4;
+ }
+ if (mantissa != 0)
+ __glibcxx_assert(__bit_width(mantissa) >= mantissa_bits + 1
+ && __bit_width(mantissa) <= mantissa_bits + 4);
+ else
+ __glibcxx_assert(!midpoint_bit && !nonzero_tail);
+
+ if (!seen_hexit)
+ // If we haven't seen any hexit at this point, the parse failed.
+ return {orig_first, errc::invalid_argument};
+
+ // Parse the written exponent.
+ int written_exponent = 0;
+ if (first != last && (*first == 'p' || *first == 'P'))
+ {
+ // Tentatively consume the 'p' and try to parse a decimal number.
+ const char* const fallback_first = first;
+ ++first;
+ if (first != last && *first == '+')
+ ++first;
+ from_chars_result fcr = from_chars(first, last, written_exponent, 10);
+ if (fcr.ptr == first)
+ // The parse failed, so undo consuming the 'p' and carry on as if the
+ // exponent was omitted (i.e. is 0).
+ first = fallback_first;
+ else
+ {
+ first = fcr.ptr;
+ if (mantissa != 0 && fcr.ec == errc::result_out_of_range)
+ // Punt on very large exponents for now. FIXME
+ return {first, errc::result_out_of_range};
+ }
+ }
+ int biased_exponent = written_exponent + exponent_bias;
+ if (exponent_adjustment != 0)
+ // The mantissa wasn't written in scientific form. Adjust the exponent
+ // so that we may assume scientific form.
+ //
+ // Examples;
+ // For input "a.bcp5", EXPONENT_ADJUSTMENT would be 0 since this
+ // written mantissa is already in scientific form.
+ // For input "ab.cp5", EXPONENT_ADJUSTMENT would be 4 since the
+ // scientific form is "a.bcp9".
+ // For input 0.0abcp5", EXPONENT_ADJUSTMENT would be -8 since the
+ // scientific form is "a.bcp-3".
+ biased_exponent += exponent_adjustment;
+
+ // Shifts the mantissa to the right by AMOUNT while updating
+ // BIASED_EXPONENT, MIDPOINT_BIT and NONZERO_TAIL accordingly.
+ auto shift_mantissa = [&] (int amount) {
+ __glibcxx_assert(amount >= 0);
+ if (amount > mantissa_bits + 1)
+ {
+ // Shifting the mantissa by an amount greater than its precision.
+ nonzero_tail |= midpoint_bit;
+ nonzero_tail |= mantissa != 0;
+ midpoint_bit = false;
+ mantissa = 0;
+ biased_exponent += amount;
+ }
+ else if (amount != 0)
+ {
+ nonzero_tail |= midpoint_bit;
+ nonzero_tail |= (mantissa & ((1ull << (amount - 1)) - 1)) != 0;
+ midpoint_bit = (mantissa & (1ull << (amount - 1))) != 0;
+ mantissa >>= amount;
+ biased_exponent += amount;
+ }
+ };
+
+ if (mantissa != 0)
+ {
+ // If the leading hexit is not '1', shift MANTISSA to make it so.
+ // This normalizes input like "4.08p0" into "1.02p2".
+ const int leading_hexit = mantissa >> mantissa_bits;
+ const int leading_hexit_width = __bit_width(leading_hexit); // FIXME: optimize?
+ __glibcxx_assert(leading_hexit_width >= 1 && leading_hexit_width <= 4);
+ shift_mantissa(leading_hexit_width - 1);
+ // After this adjustment, we can assume the leading hexit is '1'.
+ __glibcxx_assert((mantissa >> mantissa_bits) == 0x1);
+ }
+
+ if (biased_exponent <= 0)
+ {
+ // This number is too small to be represented as a normal number, so
+ // try for a subnormal number by shifting the mantissa sufficiently.
+ // We need to shift by 1 more than -BIASED_EXPONENT because the leading
+ // mantissa bit is omitted in the representation of a normal number but
+ // not in a subnormal number.
+ shift_mantissa(-biased_exponent + 1);
+ __glibcxx_assert(!(mantissa & (1ull << mantissa_bits)));
+ __glibcxx_assert(biased_exponent == 1);
+ biased_exponent = 0;
+ }
+
+ // Perform round-to-nearest, tie-to-even rounding according to
+ // MIDPOINT_BIT and NONZERO_TAIL.
+ if (midpoint_bit && (nonzero_tail || (mantissa % 2) != 0))
+ {
+ // Rounding away from zero.
+ ++mantissa;
+ midpoint_bit = false;
+ nonzero_tail = false;
+
+ // Deal with a couple of corner cases after rounding.
+ if (mantissa == (1ull << mantissa_bits))
+ {
+ // We rounded the subnormal number 1.fffffffffffff...p-1023
+ // up to the normal number 1p-1022.
+ __glibcxx_assert(biased_exponent == 0);
+ ++biased_exponent;
+ }
+ else if (mantissa & (1ull << (mantissa_bits + 1)))
+ {
+ // We rounded the normal number 1.fffffffffffff8pN (with maximal
+ // mantissa) up to to 1p(N+1).
+ mantissa >>= 1;
+ ++biased_exponent;
+ }
+ }
+ else
+ {
+ // Rounding toward zero.
+
+ if (mantissa == 0 && (midpoint_bit || nonzero_tail))
+ {
+ // A nonzero number that rounds to zero is unrepresentable.
+ __glibcxx_assert(biased_exponent == 0);
+ return {first, errc::result_out_of_range};
+ }
+
+ midpoint_bit = false;
+ nonzero_tail = false;
+ }
+
+ if (mantissa != 0 && biased_exponent >= (1 << exponent_bits) - 1)
+ // The exponent of this number is too large to be representable.
+ return {first, errc::result_out_of_range};
+
+ uint_t result = 0;
+ if (mantissa == 0)
+ {
+ // Assemble a (possibly signed) zero.
+ if (sign_bit)
+ result |= 1ull << (exponent_bits + mantissa_bits);
+ }
+ else
+ {
+ // Assemble a nonzero normal or subnormal value.
+ result |= sign_bit;
+ result <<= exponent_bits;
+ result |= biased_exponent;
+ result <<= mantissa_bits;
+ result |= mantissa & ((1ull << mantissa_bits) - 1);
+ // The implicit leading mantissa bit is set iff the number is normal.
+ __glibcxx_assert(((mantissa & (1ull << mantissa_bits)) != 0)
+ == (biased_exponent != 0));
+ }
+ if constexpr (is_same_v<T, float> || is_same_v<T, double>)
+ memcpy(&value, &result, sizeof(result));
+#if USE_LIB_FAST_FLOAT
+ else if constexpr (is_same_v<T, fast_float::floating_type_bfloat16_t>)
+ {
+ uint32_t res = uint32_t{result} << 16;
+ memcpy(value.x, &res, sizeof(res));
+ }
+ else
+ {
+ // Otherwise float16_t which needs to be converted to float32_t.
+ uint32_t res;
+ if ((result & 0x7FFF) == 0)
+ res = uint32_t{result} << 16; // +/-0.0f16
+ else if ((result & 0x7C00) == 0)
+ { // denormal
+ unsigned n = (std::numeric_limits<unsigned int>::digits
+ - __builtin_clz (result & 0x3FF) - 1);
+ res = uint32_t{result} & 0x3FF & ~(uint32_t{1} << n);
+ res <<= 23 - n;
+ res |= (((uint32_t{n} + 0x67) << 23)
+ | ((uint32_t{result} & 0x8000) << 16));
+ }
+ else
+ res = (((uint32_t{result} & 0x3FF) << 13)
+ | ((((uint32_t{result} >> 10) & 0x1F) + 0x70) << 23)
+ | ((uint32_t{result} & 0x8000) << 16));
+ memcpy(value.x, &res, sizeof(res));
+ }
+#endif
+
+ return {first, errc{}};
+ }
+#endif // _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64
+
} // namespace
-// FIXME: This should be reimplemented so it doesn't use strtod and newlocale.
-// That will avoid the need for any memory allocation, meaning that the
-// non-conforming errc::not_enough_memory result cannot happen.
+#if USE_LIB_FAST_FLOAT || USE_STRTOD_FOR_FROM_CHARS
from_chars_result
from_chars(const char* first, const char* last, float& value,
chars_format fmt) noexcept
{
- buffer_resource mr;
- pmr::string buf(&mr);
- size_t len = 0;
- errc ec = errc::invalid_argument;
- __try
- {
- if (const char* pat = pattern(first, last, fmt, buf)) [[likely]]
- len = from_chars_impl(pat, value, ec);
- }
- __catch (const std::bad_alloc&)
- {
- fmt = chars_format{};
- }
- return make_result(first, len, fmt, ec);
+#if USE_LIB_FAST_FLOAT
+ if (fmt == chars_format::hex)
+ return __floating_from_chars_hex(first, last, value);
+ else
+ return fast_float::from_chars(first, last, value, fmt);
+#else
+ return from_chars_strtod(first, last, value, fmt);
+#endif
}
from_chars_result
from_chars(const char* first, const char* last, double& value,
chars_format fmt) noexcept
{
- buffer_resource mr;
- pmr::string buf(&mr);
- size_t len = 0;
- errc ec = errc::invalid_argument;
- __try
- {
- if (const char* pat = pattern(first, last, fmt, buf)) [[likely]]
- len = from_chars_impl(pat, value, ec);
- }
- __catch (const std::bad_alloc&)
- {
- fmt = chars_format{};
- }
- return make_result(first, len, fmt, ec);
+#if USE_LIB_FAST_FLOAT
+ if (fmt == chars_format::hex)
+ return __floating_from_chars_hex(first, last, value);
+ else
+ return fast_float::from_chars(first, last, value, fmt);
+#else
+ return from_chars_strtod(first, last, value, fmt);
+#endif
}
from_chars_result
from_chars(const char* first, const char* last, long double& value,
chars_format fmt) noexcept
{
- buffer_resource mr;
- pmr::string buf(&mr);
- size_t len = 0;
- errc ec = errc::invalid_argument;
- __try
- {
- if (const char* pat = pattern(first, last, fmt, buf)) [[likely]]
- len = from_chars_impl(pat, value, ec);
- }
- __catch (const std::bad_alloc&)
- {
- fmt = chars_format{};
- }
- return make_result(first, len, fmt, ec);
+#if ! USE_STRTOD_FOR_FROM_CHARS
+ // Either long double is the same as double, or we can't use strtold.
+ // In the latter case, this might give an incorrect result (e.g. values
+ // out of range of double give an error, even if they fit in long double).
+ double dbl_value;
+ from_chars_result result;
+ if (fmt == chars_format::hex)
+ result = __floating_from_chars_hex(first, last, dbl_value);
+ else
+ result = fast_float::from_chars(first, last, dbl_value, fmt);
+ if (result.ec == errc{})
+ value = dbl_value;
+ return result;
+#else
+ return from_chars_strtod(first, last, value, fmt);
+#endif
+}
+
+#if USE_LIB_FAST_FLOAT
+// Entrypoints for 16-bit floats.
+[[gnu::cold]] from_chars_result
+__from_chars_float16_t(const char* first, const char* last, float& value,
+ chars_format fmt) noexcept
+{
+ struct fast_float::floating_type_float16_t val{ &value, 0 };
+ if (fmt == chars_format::hex)
+ return __floating_from_chars_hex(first, last, val);
+ else
+ return fast_float::from_chars_16(first, last, val, fmt);
}
+[[gnu::cold]] from_chars_result
+__from_chars_bfloat16_t(const char* first, const char* last, float& value,
+ chars_format fmt) noexcept
+{
+ struct fast_float::floating_type_bfloat16_t val{ &value, 0 };
+ if (fmt == chars_format::hex)
+ return __floating_from_chars_hex(first, last, val);
+ else
+ return fast_float::from_chars_16(first, last, val, fmt);
+}
+#endif
+
#ifdef _GLIBCXX_LONG_DOUBLE_COMPAT
+// Make std::from_chars for 64-bit long double an alias for the overload
+// for double.
extern "C" from_chars_result
_ZSt10from_charsPKcS0_ReSt12chars_format(const char* first, const char* last,
long double& value,
__attribute__((alias ("_ZSt10from_charsPKcS0_RdSt12chars_format")));
#endif
+#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
+from_chars_result
+from_chars(const char* first, const char* last, __ieee128& value,
+ chars_format fmt) noexcept
+{
+ // fast_float doesn't support IEEE binary128 format, but we can use strtold.
+ return from_chars_strtod(first, last, value, fmt);
+}
+#elif defined(USE_STRTOF128_FOR_FROM_CHARS)
+from_chars_result
+from_chars(const char* first, const char* last, _Float128& value,
+ chars_format fmt) noexcept
+{
+ // fast_float doesn't support IEEE binary128 format, but we can use strtold.
+ return from_chars_strtod(first, last, value, fmt);
+}
+#endif
+
+#endif // USE_LIB_FAST_FLOAT || USE_STRTOD_FOR_FROM_CHARS
+
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
-#endif // _GLIBCXX_HAVE_USELOCALE
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