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llvm-project/libcxx/include/__format/formatter_floating_point.h

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// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H
#define _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H
#include <__algorithm/copy.h>
#include <__algorithm/copy_n.h>
#include <__algorithm/fill_n.h>
#include <__algorithm/find.h>
#include <__algorithm/min.h>
#include <__algorithm/rotate.h>
#include <__algorithm/transform.h>
#include <__assert>
#include <__concepts/arithmetic.h>
#include <__config>
#include <__format/format_error.h>
#include <__format/format_fwd.h>
#include <__format/format_string.h>
#include <__format/formatter.h>
#include <__format/formatter_integral.h>
#include <__format/parser_std_format_spec.h>
#include <__utility/move.h>
#include <__utility/unreachable.h>
#include <charconv>
#include <cmath>
#ifndef _LIBCPP_HAS_NO_LOCALIZATION
# include <locale>
#endif
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 17
namespace __format_spec {
template <floating_point _Tp>
_LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value) {
to_chars_result __r = _VSTD::to_chars(__first, __last, __value);
_LIBCPP_ASSERT(__r.ec == errc(0), "Internal buffer too small");
return __r.ptr;
}
template <floating_point _Tp>
_LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value, chars_format __fmt) {
to_chars_result __r = _VSTD::to_chars(__first, __last, __value, __fmt);
_LIBCPP_ASSERT(__r.ec == errc(0), "Internal buffer too small");
return __r.ptr;
}
template <floating_point _Tp>
_LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value, chars_format __fmt, int __precision) {
to_chars_result __r = _VSTD::to_chars(__first, __last, __value, __fmt, __precision);
_LIBCPP_ASSERT(__r.ec == errc(0), "Internal buffer too small");
return __r.ptr;
}
// https://en.cppreference.com/w/cpp/language/types#cite_note-1
// float min subnormal: +/-0x1p-149 max: +/- 3.402,823,4 10^38
// double min subnormal: +/-0x1p-1074 max +/- 1.797,693,134,862,315,7 10^308
// long double (x86) min subnormal: +/-0x1p-16446 max: +/- 1.189,731,495,357,231,765,021 10^4932
//
// The maximum number of digits required for the integral part is based on the
// maximum's value power of 10. Every power of 10 requires one additional
// decimal digit.
// The maximum number of digits required for the fractional part is based on
// the minimal subnormal hexadecimal output's power of 10. Every division of a
// fraction's binary 1 by 2, requires one additional decimal digit.
//
// The maximum size of a formatted value depends on the selected output format.
// Ignoring the fact the format string can request a precision larger than the
// values maximum required, these values are:
//
// sign 1 code unit
// __max_integral
// radix point 1 code unit
// __max_fractional
// exponent character 1 code unit
// sign 1 code unit
// __max_fractional_value
// -----------------------------------
// total 4 code units extra required.
//
// TODO FMT Optimize the storage to avoid storing digits that are known to be zero.
// https://www.exploringbinary.com/maximum-number-of-decimal-digits-in-binary-floating-point-numbers/
// TODO FMT Add long double specialization when to_chars has proper long double support.
template <class _Tp>
struct __traits;
template <floating_point _Fp>
static constexpr size_t __float_buffer_size(int __precision) {
using _Traits = __traits<_Fp>;
return 4 + _Traits::__max_integral + __precision + _Traits::__max_fractional_value;
}
template <>
struct __traits<float> {
static constexpr int __max_integral = 38;
static constexpr int __max_fractional = 149;
static constexpr int __max_fractional_value = 3;
static constexpr size_t __stack_buffer_size = 256;
static constexpr int __hex_precision_digits = 3;
};
template <>
struct __traits<double> {
static constexpr int __max_integral = 308;
static constexpr int __max_fractional = 1074;
static constexpr int __max_fractional_value = 4;
static constexpr size_t __stack_buffer_size = 1024;
static constexpr int __hex_precision_digits = 4;
};
/// Helper class to store the conversion buffer.
///
/// Depending on the maxium size required for a value, the buffer is allocated
/// on the stack or the heap.
template <floating_point _Fp>
class _LIBCPP_TEMPLATE_VIS __float_buffer {
using _Traits = __traits<_Fp>;
public:
// TODO FMT Improve this constructor to do a better estimate.
// When using a scientific formatting with a precision of 6 a stack buffer
// will always suffice. At the moment that isn't important since floats and
// doubles use a stack buffer, unless the precision used in the format string
// is large.
// When supporting long doubles the __max_integral part becomes 4932 which
// may be too much for some platforms. For these cases a better estimate is
// required.
explicit _LIBCPP_HIDE_FROM_ABI __float_buffer(int __precision)
: __precision_(__precision != -1 ? __precision : _Traits::__max_fractional) {
// When the precision is larger than _Traits::__max_fractional the digits in
// the range (_Traits::__max_fractional, precision] will contain the value
// zero. There's no need to request to_chars to write these zeros:
// - When the value is large a temporary heap buffer needs to be allocated.
// - When to_chars writes the values they need to be "copied" to the output:
// - char: std::fill on the output iterator is faster than std::copy.
// - wchar_t: same argument as char, but additional std::copy won't work.
// The input is always a char buffer, so every char in the buffer needs
// to be converted from a char to a wchar_t.
if (__precision_ > _Traits::__max_fractional) {
__num_trailing_zeros_ = __precision_ - _Traits::__max_fractional;
__precision_ = _Traits::__max_fractional;
}
__size_ = __format_spec::__float_buffer_size<_Fp>(__precision_);
if (__size_ > _Traits::__stack_buffer_size)
// The allocated buffer's contents don't need initialization.
__begin_ = allocator<char>{}.allocate(__size_);
else
__begin_ = __buffer_;
}
_LIBCPP_HIDE_FROM_ABI ~__float_buffer() {
if (__size_ > _Traits::__stack_buffer_size)
allocator<char>{}.deallocate(__begin_, __size_);
}
_LIBCPP_HIDE_FROM_ABI __float_buffer(const __float_buffer&) = delete;
_LIBCPP_HIDE_FROM_ABI __float_buffer& operator=(const __float_buffer&) = delete;
_LIBCPP_HIDE_FROM_ABI char* begin() const { return __begin_; }
_LIBCPP_HIDE_FROM_ABI char* end() const { return __begin_ + __size_; }
_LIBCPP_HIDE_FROM_ABI int __precision() const { return __precision_; }
_LIBCPP_HIDE_FROM_ABI int __num_trailing_zeros() const { return __num_trailing_zeros_; }
_LIBCPP_HIDE_FROM_ABI void __remove_trailing_zeros() { __num_trailing_zeros_ = 0; }
private:
int __precision_;
int __num_trailing_zeros_{0};
size_t __size_;
char* __begin_;
char __buffer_[_Traits::__stack_buffer_size];
};
struct __float_result {
/// Points at the beginning of the integral part in the buffer.
///
/// When there's no sign character this points at the start of the buffer.
char* __integral;
/// Points at the radix point, when not present it's the same as \ref __last.
char* __radix_point;
/// Points at the exponent character, when not present it's the same as \ref __last.
char* __exponent;
/// Points beyond the last written element in the buffer.
char* __last;
};
/// Finds the position of the exponent character 'e' at the end of the buffer.
///
/// Assuming there is an exponent the input will terminate with
/// eSdd and eSdddd (S = sign, d = digit)
///
/// \returns a pointer to the exponent or __last when not found.
constexpr inline _LIBCPP_HIDE_FROM_ABI char* __find_exponent(char* __first, char* __last) {
ptrdiff_t __size = __last - __first;
if (__size > 4) {
__first = __last - _VSTD::min(__size, ptrdiff_t(6));
for (; __first != __last - 3; ++__first) {
if (*__first == 'e')
return __first;
}
}
return __last;
}
template <class _Fp, class _Tp>
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_default(const __float_buffer<_Fp>& __buffer, _Tp __value,
char* __integral) {
__float_result __result;
__result.__integral = __integral;
__result.__last = __format_spec::__to_buffer(__integral, __buffer.end(), __value);
__result.__exponent = __format_spec::__find_exponent(__result.__integral, __result.__last);
// Constrains:
// - There's at least one decimal digit before the radix point.
// - The radix point, when present, is placed before the exponent.
__result.__radix_point = _VSTD::find(__result.__integral + 1, __result.__exponent, '.');
// When the radix point isn't found its position is the exponent instead of
// __result.__last.
if (__result.__radix_point == __result.__exponent)
__result.__radix_point = __result.__last;
// clang-format off
_LIBCPP_ASSERT((__result.__integral != __result.__last) &&
(__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&
(__result.__exponent == __result.__last || *__result.__exponent == 'e'),
"Post-condition failure.");
// clang-format on
return __result;
}
template <class _Fp, class _Tp>
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_hexadecimal_lower_case(const __float_buffer<_Fp>& __buffer,
_Tp __value, int __precision,
char* __integral) {
__float_result __result;
__result.__integral = __integral;
if (__precision == -1)
__result.__last = __format_spec::__to_buffer(__integral, __buffer.end(), __value, chars_format::hex);
else
__result.__last = __format_spec::__to_buffer(__integral, __buffer.end(), __value, chars_format::hex, __precision);
// H = one or more hex-digits
// S = sign
// D = one or more decimal-digits
// When the fractional part is zero and no precision the output is 0p+0
// else the output is 0.HpSD
// So testing the second position can differentiate between these two cases.
char* __first = __integral + 1;
if (*__first == '.') {
__result.__radix_point = __first;
// One digit is the minimum
// 0.hpSd
// ^-- last
// ^---- integral = end of search
// ^-------- start of search
// 0123456
//
// Four digits is the maximum
// 0.hpSdddd
// ^-- last
// ^---- integral = end of search
// ^-------- start of search
// 0123456789
static_assert(__traits<_Fp>::__hex_precision_digits <= 4, "Guard against possible underflow.");
char* __last = __result.__last - 2;
__first = __last - __traits<_Fp>::__hex_precision_digits;
__result.__exponent = _VSTD::find(__first, __last, 'p');
} else {
__result.__radix_point = __result.__last;
__result.__exponent = __first;
}
// clang-format off
_LIBCPP_ASSERT((__result.__integral != __result.__last) &&
(__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&
(__result.__exponent != __result.__last && *__result.__exponent == 'p'),
"Post-condition failure.");
// clang-format on
return __result;
}
template <class _Fp, class _Tp>
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_hexadecimal_upper_case(const __float_buffer<_Fp>& __buffer,
_Tp __value, int __precision,
char* __integral) {
__float_result __result =
__format_spec::__format_buffer_hexadecimal_lower_case(__buffer, __value, __precision, __integral);
_VSTD::transform(__result.__integral, __result.__exponent, __result.__integral, __hex_to_upper);
*__result.__exponent = 'P';
return __result;
}
template <class _Fp, class _Tp>
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_scientific_lower_case(const __float_buffer<_Fp>& __buffer,
_Tp __value, int __precision,
char* __integral) {
__float_result __result;
__result.__integral = __integral;
__result.__last =
__format_spec::__to_buffer(__integral, __buffer.end(), __value, chars_format::scientific, __precision);
char* __first = __integral + 1;
_LIBCPP_ASSERT(__first != __result.__last, "No exponent present");
if (*__first == '.') {
__result.__radix_point = __first;
__result.__exponent = __format_spec::__find_exponent(__first + 1, __result.__last);
} else {
__result.__radix_point = __result.__last;
__result.__exponent = __first;
}
// clang-format off
_LIBCPP_ASSERT((__result.__integral != __result.__last) &&
(__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&
(__result.__exponent != __result.__last && *__result.__exponent == 'e'),
"Post-condition failure.");
// clang-format on
return __result;
}
template <class _Fp, class _Tp>
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_scientific_upper_case(const __float_buffer<_Fp>& __buffer,
_Tp __value, int __precision,
char* __integral) {
__float_result __result =
__format_spec::__format_buffer_scientific_lower_case(__buffer, __value, __precision, __integral);
*__result.__exponent = 'E';
return __result;
}
template <class _Fp, class _Tp>
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_fixed(const __float_buffer<_Fp>& __buffer, _Tp __value,
int __precision, char* __integral) {
__float_result __result;
__result.__integral = __integral;
__result.__last = __format_spec::__to_buffer(__integral, __buffer.end(), __value, chars_format::fixed, __precision);
// When there's no precision there's no radix point.
// Else the radix point is placed at __precision + 1 from the end.
// By converting __precision to a bool the subtraction can be done
// unconditionally.
__result.__radix_point = __result.__last - (__precision + bool(__precision));
__result.__exponent = __result.__last;
// clang-format off
_LIBCPP_ASSERT((__result.__integral != __result.__last) &&
(__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&
(__result.__exponent == __result.__last),
"Post-condition failure.");
// clang-format on
return __result;
}
template <class _Fp, class _Tp>
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_general_lower_case(__float_buffer<_Fp>& __buffer, _Tp __value,
int __precision, char* __integral) {
__buffer.__remove_trailing_zeros();
__float_result __result;
__result.__integral = __integral;
__result.__last = __format_spec::__to_buffer(__integral, __buffer.end(), __value, chars_format::general, __precision);
char* __first = __integral + 1;
if (__first == __result.__last) {
__result.__radix_point = __result.__last;
__result.__exponent = __result.__last;
} else {
__result.__exponent = __format_spec::__find_exponent(__first, __result.__last);
if (__result.__exponent != __result.__last)
// In scientific mode if there's a radix point it will always be after
// the first digit. (This is the position __first points at).
__result.__radix_point = *__first == '.' ? __first : __result.__last;
else {
// In fixed mode the algorithm truncates trailing spaces and possibly the
// radix point. There's no good guess for the position of the radix point
// therefore scan the output after the first digit.
__result.__radix_point = _VSTD::find(__first, __result.__last, '.');
}
}
// clang-format off
_LIBCPP_ASSERT((__result.__integral != __result.__last) &&
(__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&
(__result.__exponent == __result.__last || *__result.__exponent == 'e'),
"Post-condition failure.");
// clang-format on
return __result;
}
template <class _Fp, class _Tp>
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_general_upper_case(__float_buffer<_Fp>& __buffer, _Tp __value,
int __precision, char* __integral) {
__float_result __result =
__format_spec::__format_buffer_general_lower_case(__buffer, __value, __precision, __integral);
if (__result.__exponent != __result.__last)
*__result.__exponent = 'E';
return __result;
}
# ifndef _LIBCPP_HAS_NO_LOCALIZATION
template <class _OutIt, class _Fp, class _CharT>
_LIBCPP_HIDE_FROM_ABI _OutIt __format_locale_specific_form(_OutIt __out_it, const __float_buffer<_Fp>& __buffer,
const __float_result& __result, _VSTD::locale __loc,
size_t __width, _Flags::_Alignment __alignment,
_CharT __fill) {
const auto& __np = use_facet<numpunct<_CharT>>(__loc);
string __grouping = __np.grouping();
char* __first = __result.__integral;
// When no radix point or exponent are present __last will be __result.__last.
char* __last = _VSTD::min(__result.__radix_point, __result.__exponent);
ptrdiff_t __digits = __last - __first;
if (!__grouping.empty()) {
if (__digits <= __grouping[0])
__grouping.clear();
else
__grouping = __determine_grouping(__digits, __grouping);
}
size_t __size = __result.__last - __buffer.begin() + // Formatted string
__buffer.__num_trailing_zeros() + // Not yet rendered zeros
__grouping.size() - // Grouping contains one
!__grouping.empty(); // additional character
__formatter::__padding_size_result __padding = {0, 0};
bool __zero_padding = __alignment == _Flags::_Alignment::__default;
if (__size < __width) {
if (__zero_padding) {
__alignment = _Flags::_Alignment::__right;
__fill = _CharT('0');
}
__padding = __formatter::__padding_size(__size, __width, __alignment);
}
// sign and (zero padding or alignment)
if (__zero_padding && __first != __buffer.begin())
*__out_it++ = *__buffer.begin();
__out_it = _VSTD::fill_n(_VSTD::move(__out_it), __padding.__before, __fill);
if (!__zero_padding && __first != __buffer.begin())
*__out_it++ = *__buffer.begin();
// integral part
if (__grouping.empty()) {
__out_it = _VSTD::copy_n(__first, __digits, _VSTD::move(__out_it));
} else {
auto __r = __grouping.rbegin();
auto __e = __grouping.rend() - 1;
_CharT __sep = __np.thousands_sep();
// The output is divided in small groups of numbers to write:
// - A group before the first separator.
// - A separator and a group, repeated for the number of separators.
// - A group after the last separator.
// This loop achieves that process by testing the termination condition
// midway in the loop.
while (true) {
__out_it = _VSTD::copy_n(__first, *__r, _VSTD::move(__out_it));
__first += *__r;
if (__r == __e)
break;
++__r;
*__out_it++ = __sep;
}
}
// fractional part
if (__result.__radix_point != __result.__last) {
*__out_it++ = __np.decimal_point();
__out_it = _VSTD::copy(__result.__radix_point + 1, __result.__exponent, _VSTD::move(__out_it));
__out_it = _VSTD::fill_n(_VSTD::move(__out_it), __buffer.__num_trailing_zeros(), _CharT('0'));
}
// exponent
if (__result.__exponent != __result.__last)
__out_it = _VSTD::copy(__result.__exponent, __result.__last, _VSTD::move(__out_it));
// alignment
return _VSTD::fill_n(_VSTD::move(__out_it), __padding.__after, __fill);
}
# endif // _LIBCPP_HAS_NO_LOCALIZATION
template <__formatter::__char_type _CharT>
class _LIBCPP_TEMPLATE_VIS __formatter_floating_point : public __parser_floating_point<_CharT> {
public:
template <floating_point _Tp>
_LIBCPP_HIDE_FROM_ABI auto format(_Tp __value, auto& __ctx) -> decltype(__ctx.out()) {
if (this->__width_needs_substitution())
this->__substitute_width_arg_id(__ctx.arg(this->__width));
bool __negative = _VSTD::signbit(__value);
if (!_VSTD::isfinite(__value)) [[unlikely]]
return __format_non_finite(__ctx.out(), __negative, _VSTD::isnan(__value));
bool __has_precision = this->__has_precision_field();
if (this->__precision_needs_substitution())
this->__substitute_precision_arg_id(__ctx.arg(this->__precision));
// Depending on the std-format-spec string the sign and the value
// might not be outputted together:
// - zero-padding may insert additional '0' characters.
// Therefore the value is processed as a non negative value.
// The function @ref __insert_sign will insert a '-' when the value was
// negative.
if (__negative)
__value = _VSTD::copysign(__value, +1.0);
// TODO FMT _Fp should just be _Tp when to_chars has proper long double support.
using _Fp = conditional_t<same_as<_Tp, long double>, double, _Tp>;
// Force the type of the precision to avoid -1 to become an unsigned value.
__float_buffer<_Fp> __buffer(__has_precision ? int(this->__precision) : -1);
__float_result __result = __format_buffer(__buffer, __value, __negative, __has_precision);
if (this->__alternate_form && __result.__radix_point == __result.__last) {
*__result.__last++ = '.';
// When there is an exponent the point needs to be moved before the
// exponent. When there's no exponent the rotate does nothing. Since
// rotate tests whether the operation is a nop, call it unconditionally.
_VSTD::rotate(__result.__exponent, __result.__last - 1, __result.__last);
__result.__radix_point = __result.__exponent;
// The radix point is always placed before the exponent.
// - No exponent needs to point to the new last.
// - An exponent needs to move one position to the right.
// So it's safe to increment the value unconditionally.
++__result.__exponent;
}
# ifndef _LIBCPP_HAS_NO_LOCALIZATION
if (this->__locale_specific_form)
return __format_spec::__format_locale_specific_form(__ctx.out(), __buffer, __result, __ctx.locale(),
this->__width, this->__alignment, this->__fill);
# endif
ptrdiff_t __size = __result.__last - __buffer.begin();
int __num_trailing_zeros = __buffer.__num_trailing_zeros();
if (__size + __num_trailing_zeros >= this->__width) {
if (__num_trailing_zeros && __result.__exponent != __result.__last)
// Insert trailing zeros before exponent character.
return _VSTD::copy(__result.__exponent, __result.__last,
_VSTD::fill_n(_VSTD::copy(__buffer.begin(), __result.__exponent, __ctx.out()),
__num_trailing_zeros, _CharT('0')));
return _VSTD::fill_n(_VSTD::copy(__buffer.begin(), __result.__last, __ctx.out()), __num_trailing_zeros,
_CharT('0'));
}
auto __out_it = __ctx.out();
char* __first = __buffer.begin();
if (this->__alignment == _Flags::_Alignment::__default) {
// When there is a sign output it before the padding. Note the __size
// doesn't need any adjustment, regardless whether the sign is written
// here or in __formatter::__write.
if (__first != __result.__integral)
*__out_it++ = *__first++;
// After the sign is written, zero padding is the same a right alignment
// with '0'.
this->__alignment = _Flags::_Alignment::__right;
this->__fill = _CharT('0');
}
if (__num_trailing_zeros)
return __formatter::__write(_VSTD::move(__out_it), __first, __result.__last, __size, this->__width, this->__fill,
this->__alignment, __result.__exponent, __num_trailing_zeros);
return __formatter::__write(_VSTD::move(__out_it), __first, __result.__last, __size, this->__width, this->__fill,
this->__alignment);
}
private:
template <class _OutIt>
_LIBCPP_HIDE_FROM_ABI _OutIt __format_non_finite(_OutIt __out_it, bool __negative, bool __isnan) {
char __buffer[4];
char* __last = __insert_sign(__buffer, __negative, this->__sign);
// to_char can return inf, infinity, nan, and nan(n-char-sequence).
// The format library requires inf and nan.
// All in one expression to avoid dangling references.
__last = _VSTD::copy_n(&("infnanINFNAN"[6 * (this->__type == _Flags::_Type::__float_hexadecimal_upper_case ||
this->__type == _Flags::_Type::__scientific_upper_case ||
this->__type == _Flags::_Type::__fixed_upper_case ||
this->__type == _Flags::_Type::__general_upper_case) +
3 * __isnan]),
3, __last);
// [format.string.std]/13
// A zero (0) character preceding the width field pads the field with
// leading zeros (following any indication of sign or base) to the field
// width, except when applied to an infinity or NaN.
if (this->__alignment == _Flags::_Alignment::__default)
this->__alignment = _Flags::_Alignment::__right;
ptrdiff_t __size = __last - __buffer;
if (__size >= this->__width)
return _VSTD::copy_n(__buffer, __size, _VSTD::move(__out_it));
return __formatter::__write(_VSTD::move(__out_it), __buffer, __last, __size, this->__width, this->__fill,
this->__alignment);
}
/// Fills the buffer with the data based on the requested formatting.
///
/// This function, when needed, turns the characters to upper case and
/// determines the "interesting" locations which are returned to the caller.
///
/// This means the caller never has to convert the contents of the buffer to
/// upper case or search for radix points and the location of the exponent.
/// This gives a bit of overhead. The original code didn't do that, but due
/// to the number of possible additional work needed to turn this number to
/// the proper output the code was littered with tests for upper cases and
/// searches for radix points and exponents.
/// - When a precision larger than the type's precision is selected
/// additional zero characters need to be written before the exponent.
/// - alternate form needs to add a radix point when not present.
/// - localization needs to do grouping in the integral part.
template <class _Fp, class _Tp>
// TODO FMT _Fp should just be _Tp when to_chars has proper long double support.
_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer(__float_buffer<_Fp>& __buffer, _Tp __value, bool __negative,
bool __has_precision) {
char* __first = __insert_sign(__buffer.begin(), __negative, this->__sign);
switch (this->__type) {
case _Flags::_Type::__default:
return __format_spec::__format_buffer_default(__buffer, __value, __first);
case _Flags::_Type::__float_hexadecimal_lower_case:
return __format_spec::__format_buffer_hexadecimal_lower_case(
__buffer, __value, __has_precision ? __buffer.__precision() : -1, __first);
case _Flags::_Type::__float_hexadecimal_upper_case:
return __format_spec::__format_buffer_hexadecimal_upper_case(
__buffer, __value, __has_precision ? __buffer.__precision() : -1, __first);
case _Flags::_Type::__scientific_lower_case:
return __format_spec::__format_buffer_scientific_lower_case(__buffer, __value, __buffer.__precision(), __first);
case _Flags::_Type::__scientific_upper_case:
return __format_spec::__format_buffer_scientific_upper_case(__buffer, __value, __buffer.__precision(), __first);
case _Flags::_Type::__fixed_lower_case:
case _Flags::_Type::__fixed_upper_case:
return __format_spec::__format_buffer_fixed(__buffer, __value, __buffer.__precision(), __first);
case _Flags::_Type::__general_lower_case:
return __format_spec::__format_buffer_general_lower_case(__buffer, __value, __buffer.__precision(), __first);
case _Flags::_Type::__general_upper_case:
return __format_spec::__format_buffer_general_upper_case(__buffer, __value, __buffer.__precision(), __first);
default:
_LIBCPP_ASSERT(false, "The parser should have validated the type");
__libcpp_unreachable();
}
}
};
} //namespace __format_spec
template <__formatter::__char_type _CharT>
struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<float, _CharT>
: public __format_spec::__formatter_floating_point<_CharT> {};
template <__formatter::__char_type _CharT>
struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<double, _CharT>
: public __format_spec::__formatter_floating_point<_CharT> {};
template <__formatter::__char_type _CharT>
struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<long double, _CharT>
: public __format_spec::__formatter_floating_point<_CharT> {};
#endif //_LIBCPP_STD_VER > 17
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H
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