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1// -*- C++ -*-2//===----------------------------------------------------------------------===//3//4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.5// See https://llvm.org/LICENSE.txt for license information.6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception7//8//===----------------------------------------------------------------------===//9 10#ifndef _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H11#define _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H12 13#include <__algorithm/copy_n.h>14#include <__algorithm/find.h>15#include <__algorithm/max.h>16#include <__algorithm/min.h>17#include <__algorithm/rotate.h>18#include <__algorithm/transform.h>19#include <__assert>20#include <__charconv/chars_format.h>21#include <__charconv/to_chars_floating_point.h>22#include <__charconv/to_chars_integral.h>23#include <__charconv/to_chars_result.h>24#include <__concepts/arithmetic.h>25#include <__concepts/same_as.h>26#include <__config>27#include <__cstddef/ptrdiff_t.h>28#include <__format/concepts.h>29#include <__format/format_parse_context.h>30#include <__format/formatter.h>31#include <__format/formatter_integral.h>32#include <__format/formatter_output.h>33#include <__format/parser_std_format_spec.h>34#include <__iterator/concepts.h>35#include <__memory/allocator.h>36#include <__system_error/errc.h>37#include <__type_traits/conditional.h>38#include <__utility/move.h>39#include <__utility/unreachable.h>40#include <cmath>41 42#if _LIBCPP_HAS_LOCALIZATION43# include <__locale>44#endif45 46#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)47# pragma GCC system_header48#endif49 50_LIBCPP_PUSH_MACROS51#include <__undef_macros>52 53_LIBCPP_BEGIN_NAMESPACE_STD54 55#if _LIBCPP_STD_VER >= 2056 57namespace __formatter {58 59template <floating_point _Tp>60_LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value) {61 to_chars_result __r = std::to_chars(__first, __last, __value);62 _LIBCPP_ASSERT_INTERNAL(__r.ec == errc(0), "Internal buffer too small");63 return __r.ptr;64}65 66template <floating_point _Tp>67_LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value, chars_format __fmt) {68 to_chars_result __r = std::to_chars(__first, __last, __value, __fmt);69 _LIBCPP_ASSERT_INTERNAL(__r.ec == errc(0), "Internal buffer too small");70 return __r.ptr;71}72 73template <floating_point _Tp>74_LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value, chars_format __fmt, int __precision) {75 to_chars_result __r = std::to_chars(__first, __last, __value, __fmt, __precision);76 _LIBCPP_ASSERT_INTERNAL(__r.ec == errc(0), "Internal buffer too small");77 return __r.ptr;78}79 80// https://en.cppreference.com/w/cpp/language/types#cite_note-181// float min subnormal: +/-0x1p-149 max: +/- 3.402,823,4 10^3882// double min subnormal: +/-0x1p-1074 max +/- 1.797,693,134,862,315,7 10^30883// long double (x86) min subnormal: +/-0x1p-16446 max: +/- 1.189,731,495,357,231,765,021 10^493284//85// The maximum number of digits required for the integral part is based on the86// maximum's value power of 10. Every power of 10 requires one additional87// decimal digit.88// The maximum number of digits required for the fractional part is based on89// the minimal subnormal hexadecimal output's power of 10. Every division of a90// fraction's binary 1 by 2, requires one additional decimal digit.91//92// The maximum size of a formatted value depends on the selected output format.93// Ignoring the fact the format string can request a precision larger than the94// values maximum required, these values are:95//96// sign 1 code unit97// __max_integral98// radix point 1 code unit99// __max_fractional100// exponent character 1 code unit101// sign 1 code unit102// __max_fractional_value103// -----------------------------------104// total 4 code units extra required.105//106// TODO FMT Optimize the storage to avoid storing digits that are known to be zero.107// https://www.exploringbinary.com/maximum-number-of-decimal-digits-in-binary-floating-point-numbers/108 109// TODO FMT Add long double specialization when to_chars has proper long double support.110template <class _Tp>111struct __traits;112 113template <floating_point _Fp>114_LIBCPP_HIDE_FROM_ABI constexpr size_t __float_buffer_size(int __precision) {115 using _Traits = __traits<_Fp>;116 return 4 + _Traits::__max_integral + __precision + _Traits::__max_fractional_value;117}118 119template <>120struct __traits<float> {121 static constexpr int __max_integral = 38;122 static constexpr int __max_fractional = 149;123 static constexpr int __max_fractional_value = 3;124 static constexpr size_t __stack_buffer_size = 256;125 126 static constexpr int __hex_precision_digits = 3;127};128 129template <>130struct __traits<double> {131 static constexpr int __max_integral = 308;132 static constexpr int __max_fractional = 1074;133 static constexpr int __max_fractional_value = 4;134 static constexpr size_t __stack_buffer_size = 1024;135 136 static constexpr int __hex_precision_digits = 4;137};138 139/// Helper class to store the conversion buffer.140///141/// Depending on the maximum size required for a value, the buffer is allocated142/// on the stack or the heap.143template <floating_point _Fp>144class __float_buffer {145 using _Traits _LIBCPP_NODEBUG = __traits<_Fp>;146 147public:148 // TODO FMT Improve this constructor to do a better estimate.149 // When using a scientific formatting with a precision of 6 a stack buffer150 // will always suffice. At the moment that isn't important since floats and151 // doubles use a stack buffer, unless the precision used in the format string152 // is large.153 // When supporting long doubles the __max_integral part becomes 4932 which154 // may be too much for some platforms. For these cases a better estimate is155 // required.156 explicit _LIBCPP_HIDE_FROM_ABI __float_buffer(int __precision)157 : __precision_(__precision != -1 ? __precision : _Traits::__max_fractional) {158 // When the precision is larger than _Traits::__max_fractional the digits in159 // the range (_Traits::__max_fractional, precision] will contain the value160 // zero. There's no need to request to_chars to write these zeros:161 // - When the value is large a temporary heap buffer needs to be allocated.162 // - When to_chars writes the values they need to be "copied" to the output:163 // - char: std::fill on the output iterator is faster than std::copy.164 // - wchar_t: same argument as char, but additional std::copy won't work.165 // The input is always a char buffer, so every char in the buffer needs166 // to be converted from a char to a wchar_t.167 if (__precision_ > _Traits::__max_fractional) {168 __num_trailing_zeros_ = __precision_ - _Traits::__max_fractional;169 __precision_ = _Traits::__max_fractional;170 }171 172 __size_ = __formatter::__float_buffer_size<_Fp>(__precision_);173 if (__size_ > _Traits::__stack_buffer_size)174 // The allocated buffer's contents don't need initialization.175 __begin_ = allocator<char>{}.allocate(__size_);176 else177 __begin_ = __buffer_;178 }179 180 _LIBCPP_HIDE_FROM_ABI ~__float_buffer() {181 if (__size_ > _Traits::__stack_buffer_size)182 allocator<char>{}.deallocate(__begin_, __size_);183 }184 _LIBCPP_HIDE_FROM_ABI __float_buffer(const __float_buffer&) = delete;185 _LIBCPP_HIDE_FROM_ABI __float_buffer& operator=(const __float_buffer&) = delete;186 187 _LIBCPP_HIDE_FROM_ABI char* begin() const { return __begin_; }188 _LIBCPP_HIDE_FROM_ABI char* end() const { return __begin_ + __size_; }189 190 _LIBCPP_HIDE_FROM_ABI int __precision() const { return __precision_; }191 _LIBCPP_HIDE_FROM_ABI int __num_trailing_zeros() const { return __num_trailing_zeros_; }192 _LIBCPP_HIDE_FROM_ABI void __remove_trailing_zeros() { __num_trailing_zeros_ = 0; }193 _LIBCPP_HIDE_FROM_ABI void __add_trailing_zeros(int __zeros) { __num_trailing_zeros_ += __zeros; }194 195private:196 int __precision_;197 int __num_trailing_zeros_{0};198 size_t __size_;199 char* __begin_;200 char __buffer_[_Traits::__stack_buffer_size];201};202 203struct __float_result {204 /// Points at the beginning of the integral part in the buffer.205 ///206 /// When there's no sign character this points at the start of the buffer.207 char* __integral;208 209 /// Points at the radix point, when not present it's the same as \ref __last.210 char* __radix_point;211 212 /// Points at the exponent character, when not present it's the same as \ref __last.213 char* __exponent;214 215 /// Points beyond the last written element in the buffer.216 char* __last;217};218 219/// Finds the position of the exponent character 'e' at the end of the buffer.220///221/// Assuming there is an exponent the input will terminate with222/// eSdd and eSdddd (S = sign, d = digit)223///224/// \returns a pointer to the exponent or __last when not found.225constexpr inline _LIBCPP_HIDE_FROM_ABI char* __find_exponent(char* __first, char* __last) {226 ptrdiff_t __size = __last - __first;227 if (__size >= 4) {228 __first = __last - std::min(__size, ptrdiff_t(6));229 for (; __first != __last - 3; ++__first) {230 if (*__first == 'e')231 return __first;232 }233 }234 return __last;235}236 237template <class _Fp, class _Tp>238_LIBCPP_HIDE_FROM_ABI __float_result239__format_buffer_default(const __float_buffer<_Fp>& __buffer, _Tp __value, char* __integral) {240 __float_result __result;241 __result.__integral = __integral;242 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value);243 244 __result.__exponent = __formatter::__find_exponent(__result.__integral, __result.__last);245 246 // Constrains:247 // - There's at least one decimal digit before the radix point.248 // - The radix point, when present, is placed before the exponent.249 __result.__radix_point = std::find(__result.__integral + 1, __result.__exponent, '.');250 251 // When the radix point isn't found its position is the exponent instead of252 // __result.__last.253 if (__result.__radix_point == __result.__exponent)254 __result.__radix_point = __result.__last;255 256 // clang-format off257 _LIBCPP_ASSERT_INTERNAL((__result.__integral != __result.__last) &&258 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&259 (__result.__exponent == __result.__last || *__result.__exponent == 'e'),260 "Post-condition failure.");261 // clang-format on262 263 return __result;264}265 266template <class _Fp, class _Tp>267_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_hexadecimal_lower_case(268 const __float_buffer<_Fp>& __buffer, _Tp __value, int __precision, char* __integral) {269 __float_result __result;270 __result.__integral = __integral;271 if (__precision == -1)272 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::hex);273 else274 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::hex, __precision);275 276 // H = one or more hex-digits277 // S = sign278 // D = one or more decimal-digits279 // When the fractional part is zero and no precision the output is 0p+0280 // else the output is 0.HpSD281 // So testing the second position can differentiate between these two cases.282 char* __first = __integral + 1;283 if (*__first == '.') {284 __result.__radix_point = __first;285 // One digit is the minimum286 // 0.hpSd287 // ^-- last288 // ^---- integral = end of search289 // ^-------- start of search290 // 0123456291 //292 // Four digits is the maximum293 // 0.hpSdddd294 // ^-- last295 // ^---- integral = end of search296 // ^-------- start of search297 // 0123456789298 static_assert(__traits<_Fp>::__hex_precision_digits <= 4, "Guard against possible underflow.");299 300 char* __last = __result.__last - 2;301 __first = __last - __traits<_Fp>::__hex_precision_digits;302 __result.__exponent = std::find(__first, __last, 'p');303 } else {304 __result.__radix_point = __result.__last;305 __result.__exponent = __first;306 }307 308 // clang-format off309 _LIBCPP_ASSERT_INTERNAL((__result.__integral != __result.__last) &&310 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&311 (__result.__exponent != __result.__last && *__result.__exponent == 'p'),312 "Post-condition failure.");313 // clang-format on314 315 return __result;316}317 318template <class _Fp, class _Tp>319_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_hexadecimal_upper_case(320 const __float_buffer<_Fp>& __buffer, _Tp __value, int __precision, char* __integral) {321 __float_result __result =322 __formatter::__format_buffer_hexadecimal_lower_case(__buffer, __value, __precision, __integral);323 std::transform(__result.__integral, __result.__exponent, __result.__integral, __hex_to_upper);324 *__result.__exponent = 'P';325 return __result;326}327 328template <class _Fp, class _Tp>329_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_scientific_lower_case(330 const __float_buffer<_Fp>& __buffer, _Tp __value, int __precision, char* __integral) {331 __float_result __result;332 __result.__integral = __integral;333 __result.__last =334 __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::scientific, __precision);335 336 char* __first = __integral + 1;337 _LIBCPP_ASSERT_INTERNAL(__first != __result.__last, "No exponent present");338 if (*__first == '.') {339 __result.__radix_point = __first;340 __result.__exponent = __formatter::__find_exponent(__first + 1, __result.__last);341 } else {342 __result.__radix_point = __result.__last;343 __result.__exponent = __first;344 }345 346 // clang-format off347 _LIBCPP_ASSERT_INTERNAL((__result.__integral != __result.__last) &&348 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&349 (__result.__exponent != __result.__last && *__result.__exponent == 'e'),350 "Post-condition failure.");351 // clang-format on352 return __result;353}354 355template <class _Fp, class _Tp>356_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_scientific_upper_case(357 const __float_buffer<_Fp>& __buffer, _Tp __value, int __precision, char* __integral) {358 __float_result __result =359 __formatter::__format_buffer_scientific_lower_case(__buffer, __value, __precision, __integral);360 *__result.__exponent = 'E';361 return __result;362}363 364template <class _Fp, class _Tp>365_LIBCPP_HIDE_FROM_ABI __float_result366__format_buffer_fixed(const __float_buffer<_Fp>& __buffer, _Tp __value, int __precision, char* __integral) {367 __float_result __result;368 __result.__integral = __integral;369 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::fixed, __precision);370 371 // When there's no precision there's no radix point.372 // Else the radix point is placed at __precision + 1 from the end.373 // By converting __precision to a bool the subtraction can be done374 // unconditionally.375 __result.__radix_point = __result.__last - (__precision + bool(__precision));376 __result.__exponent = __result.__last;377 378 // clang-format off379 _LIBCPP_ASSERT_INTERNAL((__result.__integral != __result.__last) &&380 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&381 (__result.__exponent == __result.__last),382 "Post-condition failure.");383 // clang-format on384 return __result;385}386 387template <class _Fp, class _Tp>388_LIBCPP_HIDE_FROM_ABI __float_result389__format_buffer_general_lower_case(__float_buffer<_Fp>& __buffer, _Tp __value, int __precision, char* __integral) {390 __buffer.__remove_trailing_zeros();391 392 __float_result __result;393 __result.__integral = __integral;394 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::general, __precision);395 396 char* __first = __integral + 1;397 if (__first == __result.__last) {398 __result.__radix_point = __result.__last;399 __result.__exponent = __result.__last;400 } else {401 __result.__exponent = __formatter::__find_exponent(__first, __result.__last);402 if (__result.__exponent != __result.__last)403 // In scientific mode if there's a radix point it will always be after404 // the first digit. (This is the position __first points at).405 __result.__radix_point = *__first == '.' ? __first : __result.__last;406 else {407 // In fixed mode the algorithm truncates trailing spaces and possibly the408 // radix point. There's no good guess for the position of the radix point409 // therefore scan the output after the first digit.410 __result.__radix_point = std::find(__first, __result.__last, '.');411 }412 }413 414 // clang-format off415 _LIBCPP_ASSERT_INTERNAL((__result.__integral != __result.__last) &&416 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') &&417 (__result.__exponent == __result.__last || *__result.__exponent == 'e'),418 "Post-condition failure.");419 // clang-format on420 421 return __result;422}423 424template <class _Fp, class _Tp>425_LIBCPP_HIDE_FROM_ABI __float_result426__format_buffer_general_upper_case(__float_buffer<_Fp>& __buffer, _Tp __value, int __precision, char* __integral) {427 __float_result __result = __formatter::__format_buffer_general_lower_case(__buffer, __value, __precision, __integral);428 if (__result.__exponent != __result.__last)429 *__result.__exponent = 'E';430 return __result;431}432 433/// Fills the buffer with the data based on the requested formatting.434///435/// This function, when needed, turns the characters to upper case and436/// determines the "interesting" locations which are returned to the caller.437///438/// This means the caller never has to convert the contents of the buffer to439/// upper case or search for radix points and the location of the exponent.440/// This gives a bit of overhead. The original code didn't do that, but due441/// to the number of possible additional work needed to turn this number to442/// the proper output the code was littered with tests for upper cases and443/// searches for radix points and exponents.444/// - When a precision larger than the type's precision is selected445/// additional zero characters need to be written before the exponent.446/// - alternate form needs to add a radix point when not present.447/// - localization needs to do grouping in the integral part.448template <class _Fp, class _Tp>449// TODO FMT _Fp should just be _Tp when to_chars has proper long double support.450_LIBCPP_HIDE_FROM_ABI __float_result __format_buffer(451 __float_buffer<_Fp>& __buffer,452 _Tp __value,453 bool __negative,454 bool __has_precision,455 __format_spec::__sign __sign,456 __format_spec::__type __type) {457 char* __first = __formatter::__insert_sign(__buffer.begin(), __negative, __sign);458 switch (__type) {459 case __format_spec::__type::__default:460 if (__has_precision)461 return __formatter::__format_buffer_general_lower_case(__buffer, __value, __buffer.__precision(), __first);462 else463 return __formatter::__format_buffer_default(__buffer, __value, __first);464 465 case __format_spec::__type::__hexfloat_lower_case:466 return __formatter::__format_buffer_hexadecimal_lower_case(467 __buffer, __value, __has_precision ? __buffer.__precision() : -1, __first);468 469 case __format_spec::__type::__hexfloat_upper_case:470 return __formatter::__format_buffer_hexadecimal_upper_case(471 __buffer, __value, __has_precision ? __buffer.__precision() : -1, __first);472 473 case __format_spec::__type::__scientific_lower_case:474 return __formatter::__format_buffer_scientific_lower_case(__buffer, __value, __buffer.__precision(), __first);475 476 case __format_spec::__type::__scientific_upper_case:477 return __formatter::__format_buffer_scientific_upper_case(__buffer, __value, __buffer.__precision(), __first);478 479 case __format_spec::__type::__fixed_lower_case:480 case __format_spec::__type::__fixed_upper_case:481 return __formatter::__format_buffer_fixed(__buffer, __value, __buffer.__precision(), __first);482 483 case __format_spec::__type::__general_lower_case:484 return __formatter::__format_buffer_general_lower_case(__buffer, __value, __buffer.__precision(), __first);485 486 case __format_spec::__type::__general_upper_case:487 return __formatter::__format_buffer_general_upper_case(__buffer, __value, __buffer.__precision(), __first);488 489 default:490 _LIBCPP_ASSERT_INTERNAL(false, "The parser should have validated the type");491 __libcpp_unreachable();492 }493}494 495# if _LIBCPP_HAS_LOCALIZATION496template <class _OutIt, class _Fp, class _CharT>497_LIBCPP_HIDE_FROM_ABI _OutIt __format_locale_specific_form(498 _OutIt __out_it,499 const __float_buffer<_Fp>& __buffer,500 const __float_result& __result,501 std::locale __loc,502 __format_spec::__parsed_specifications<_CharT> __specs) {503 const auto& __np = std::use_facet<numpunct<_CharT>>(__loc);504 string __grouping = __np.grouping();505 char* __first = __result.__integral;506 // When no radix point or exponent are present __last will be __result.__last.507 char* __last = std::min(__result.__radix_point, __result.__exponent);508 509 ptrdiff_t __digits = __last - __first;510 if (!__grouping.empty()) {511 if (__digits <= __grouping[0])512 __grouping.clear();513 else514 __grouping = __formatter::__determine_grouping(__digits, __grouping);515 }516 517 ptrdiff_t __size =518 __result.__last - __buffer.begin() + // Formatted string519 __buffer.__num_trailing_zeros() + // Not yet rendered zeros520 __grouping.size() - // Grouping contains one521 !__grouping.empty(); // additional character522 523 __formatter::__padding_size_result __padding = {0, 0};524 bool __zero_padding = __specs.__alignment_ == __format_spec::__alignment::__zero_padding;525 if (__size < __specs.__width_) {526 if (__zero_padding) {527 __specs.__alignment_ = __format_spec::__alignment::__right;528 __specs.__fill_.__data[0] = _CharT('0');529 }530 531 __padding = __formatter::__padding_size(__size, __specs.__width_, __specs.__alignment_);532 }533 534 // sign and (zero padding or alignment)535 if (__zero_padding && __first != __buffer.begin())536 *__out_it++ = *__buffer.begin();537 __out_it = __formatter::__fill(std::move(__out_it), __padding.__before_, __specs.__fill_);538 if (!__zero_padding && __first != __buffer.begin())539 *__out_it++ = *__buffer.begin();540 541 // integral part542 if (__grouping.empty()) {543 __out_it = __formatter::__copy(__first, __digits, std::move(__out_it));544 } else {545 auto __r = __grouping.rbegin();546 auto __e = __grouping.rend() - 1;547 _CharT __sep = __np.thousands_sep();548 // The output is divided in small groups of numbers to write:549 // - A group before the first separator.550 // - A separator and a group, repeated for the number of separators.551 // - A group after the last separator.552 // This loop achieves that process by testing the termination condition553 // midway in the loop.554 while (true) {555 __out_it = __formatter::__copy(__first, *__r, std::move(__out_it));556 __first += *__r;557 558 if (__r == __e)559 break;560 561 ++__r;562 *__out_it++ = __sep;563 }564 }565 566 // fractional part567 if (__result.__radix_point != __result.__last) {568 *__out_it++ = __np.decimal_point();569 __out_it = __formatter::__copy(__result.__radix_point + 1, __result.__exponent, std::move(__out_it));570 __out_it = __formatter::__fill(std::move(__out_it), __buffer.__num_trailing_zeros(), _CharT('0'));571 }572 573 // exponent574 if (__result.__exponent != __result.__last)575 __out_it = __formatter::__copy(__result.__exponent, __result.__last, std::move(__out_it));576 577 // alignment578 return __formatter::__fill(std::move(__out_it), __padding.__after_, __specs.__fill_);579}580# endif // _LIBCPP_HAS_LOCALIZATION581 582template <class _OutIt, class _CharT>583_LIBCPP_HIDE_FROM_ABI _OutIt __format_floating_point_non_finite(584 _OutIt __out_it, __format_spec::__parsed_specifications<_CharT> __specs, bool __negative, bool __isnan) {585 char __buffer[4];586 char* __last = __formatter::__insert_sign(__buffer, __negative, __specs.__std_.__sign_);587 588 // to_chars can return inf, infinity, nan, and nan(n-char-sequence).589 // The format library requires inf and nan.590 // All in one expression to avoid dangling references.591 bool __upper_case =592 __specs.__std_.__type_ == __format_spec::__type::__hexfloat_upper_case ||593 __specs.__std_.__type_ == __format_spec::__type::__scientific_upper_case ||594 __specs.__std_.__type_ == __format_spec::__type::__fixed_upper_case ||595 __specs.__std_.__type_ == __format_spec::__type::__general_upper_case;596 __last = std::copy_n(&("infnanINFNAN"[6 * __upper_case + 3 * __isnan]), 3, __last);597 598 // [format.string.std]/13599 // A zero (0) character preceding the width field pads the field with600 // leading zeros (following any indication of sign or base) to the field601 // width, except when applied to an infinity or NaN.602 if (__specs.__alignment_ == __format_spec::__alignment::__zero_padding)603 __specs.__alignment_ = __format_spec::__alignment::__right;604 605 return __formatter::__write(__buffer, __last, std::move(__out_it), __specs);606}607 608/// Writes additional zero's for the precision before the exponent.609/// This is used when the precision requested in the format string is larger610/// than the maximum precision of the floating-point type. These precision611/// digits are always 0.612///613/// \param __exponent The location of the exponent character.614/// \param __num_trailing_zeros The number of 0's to write before the exponent615/// character.616template <class _CharT, class _ParserCharT>617_LIBCPP_HIDE_FROM_ABI auto __write_using_trailing_zeros(618 const _CharT* __first,619 const _CharT* __last,620 output_iterator<const _CharT&> auto __out_it,621 __format_spec::__parsed_specifications<_ParserCharT> __specs,622 size_t __size,623 const _CharT* __exponent,624 size_t __num_trailing_zeros) -> decltype(__out_it) {625 _LIBCPP_ASSERT_INTERNAL(__first <= __last, "Not a valid range");626 _LIBCPP_ASSERT_INTERNAL(__num_trailing_zeros > 0, "The overload not writing trailing zeros should have been used");627 628 __padding_size_result __padding =629 __formatter::__padding_size(__size + __num_trailing_zeros, __specs.__width_, __specs.__alignment_);630 __out_it = __formatter::__fill(std::move(__out_it), __padding.__before_, __specs.__fill_);631 __out_it = __formatter::__copy(__first, __exponent, std::move(__out_it));632 __out_it = __formatter::__fill(std::move(__out_it), __num_trailing_zeros, _CharT('0'));633 __out_it = __formatter::__copy(__exponent, __last, std::move(__out_it));634 return __formatter::__fill(std::move(__out_it), __padding.__after_, __specs.__fill_);635}636 637template <floating_point _Tp, class _CharT, class _FormatContext>638_LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator639__format_floating_point(_Tp __value, _FormatContext& __ctx, __format_spec::__parsed_specifications<_CharT> __specs) {640 bool __negative = std::signbit(__value);641 642 if (!std::isfinite(__value)) [[unlikely]]643 return __formatter::__format_floating_point_non_finite(__ctx.out(), __specs, __negative, std::isnan(__value));644 645 // Depending on the std-format-spec string the sign and the value646 // might not be outputted together:647 // - zero-padding may insert additional '0' characters.648 // Therefore the value is processed as a non negative value.649 // The function @ref __insert_sign will insert a '-' when the value was650 // negative.651 652 if (__negative)653 __value = -__value;654 655 // TODO FMT _Fp should just be _Tp when to_chars has proper long double support.656 using _Fp = conditional_t<same_as<_Tp, long double>, double, _Tp>;657 // Force the type of the precision to avoid -1 to become an unsigned value.658 __float_buffer<_Fp> __buffer(__specs.__precision_);659 __float_result __result = __formatter::__format_buffer(660 __buffer, __value, __negative, (__specs.__has_precision()), __specs.__std_.__sign_, __specs.__std_.__type_);661 662 if (__specs.__std_.__alternate_form_) {663 if (__result.__radix_point == __result.__last) {664 *__result.__last++ = '.';665 666 // When there is an exponent the point needs to be moved before the667 // exponent. When there's no exponent the rotate does nothing. Since668 // rotate tests whether the operation is a nop, call it unconditionally.669 std::rotate(__result.__exponent, __result.__last - 1, __result.__last);670 __result.__radix_point = __result.__exponent;671 672 // The radix point is always placed before the exponent.673 // - No exponent needs to point to the new last.674 // - An exponent needs to move one position to the right.675 // So it's safe to increment the value unconditionally.676 ++__result.__exponent;677 }678 679 // [format.string.std]/6680 // In addition, for g and G conversions, trailing zeros are not removed681 // from the result.682 //683 // If the type option for a floating-point type is none it may use the684 // general formatting, but it's not a g or G conversion. So in that case685 // the formatting should not append trailing zeros.686 bool __is_general = __specs.__std_.__type_ == __format_spec::__type::__general_lower_case ||687 __specs.__std_.__type_ == __format_spec::__type::__general_upper_case;688 689 if (__is_general) {690 // https://en.cppreference.com/w/c/io/fprintf691 // Let P equal the precision if nonzero, 6 if the precision is not692 // specified, or 1 if the precision is 0. Then, if a conversion with693 // style E would have an exponent of X:694 int __p = std::max<int>(1, (__specs.__has_precision() ? __specs.__precision_ : 6));695 if (__result.__exponent == __result.__last)696 // if P > X >= -4, the conversion is with style f or F and precision P - 1 - X.697 // By including the radix point it calculates P - (1 + X)698 __p -= __result.__radix_point - __result.__integral;699 else700 // otherwise, the conversion is with style e or E and precision P - 1.701 --__p;702 703 ptrdiff_t __precision = (__result.__exponent - __result.__radix_point) - 1;704 if (__precision < __p)705 __buffer.__add_trailing_zeros(__p - __precision);706 }707 }708 709# if _LIBCPP_HAS_LOCALIZATION710 if (__specs.__std_.__locale_specific_form_)711 return __formatter::__format_locale_specific_form(__ctx.out(), __buffer, __result, __ctx.locale(), __specs);712# endif713 714 ptrdiff_t __size = __result.__last - __buffer.begin();715 int __num_trailing_zeros = __buffer.__num_trailing_zeros();716 if (__size + __num_trailing_zeros >= __specs.__width_) {717 if (__num_trailing_zeros && __result.__exponent != __result.__last)718 // Insert trailing zeros before exponent character.719 return __formatter::__copy(720 __result.__exponent,721 __result.__last,722 __formatter::__fill(__formatter::__copy(__buffer.begin(), __result.__exponent, __ctx.out()),723 __num_trailing_zeros,724 _CharT('0')));725 726 return __formatter::__fill(727 __formatter::__copy(__buffer.begin(), __result.__last, __ctx.out()), __num_trailing_zeros, _CharT('0'));728 }729 730 auto __out_it = __ctx.out();731 char* __first = __buffer.begin();732 if (__specs.__alignment_ == __format_spec::__alignment ::__zero_padding) {733 // When there is a sign output it before the padding. Note the __size734 // doesn't need any adjustment, regardless whether the sign is written735 // here or in __formatter::__write.736 if (__first != __result.__integral)737 *__out_it++ = *__first++;738 // After the sign is written, zero padding is the same a right alignment739 // with '0'.740 __specs.__alignment_ = __format_spec::__alignment::__right;741 __specs.__fill_.__data[0] = _CharT('0');742 }743 744 if (__num_trailing_zeros)745 return __formatter::__write_using_trailing_zeros(746 __first, __result.__last, std::move(__out_it), __specs, __size, __result.__exponent, __num_trailing_zeros);747 748 return __formatter::__write(__first, __result.__last, std::move(__out_it), __specs, __size);749}750 751} // namespace __formatter752 753template <__fmt_char_type _CharT>754struct __formatter_floating_point {755public:756 template <class _ParseContext>757 _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {758 typename _ParseContext::iterator __result = __parser_.__parse(__ctx, __format_spec::__fields_floating_point);759 __format_spec::__process_parsed_floating_point(__parser_, "a floating-point");760 return __result;761 }762 763 template <floating_point _Tp, class _FormatContext>764 _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(_Tp __value, _FormatContext& __ctx) const {765 return __formatter::__format_floating_point(__value, __ctx, __parser_.__get_parsed_std_specifications(__ctx));766 }767 768 __format_spec::__parser<_CharT> __parser_;769};770 771template <__fmt_char_type _CharT>772struct formatter<float, _CharT> : public __formatter_floating_point<_CharT> {};773template <__fmt_char_type _CharT>774struct formatter<double, _CharT> : public __formatter_floating_point<_CharT> {};775template <__fmt_char_type _CharT>776struct formatter<long double, _CharT> : public __formatter_floating_point<_CharT> {};777 778# if _LIBCPP_STD_VER >= 23779template <>780inline constexpr bool enable_nonlocking_formatter_optimization<float> = true;781template <>782inline constexpr bool enable_nonlocking_formatter_optimization<double> = true;783template <>784inline constexpr bool enable_nonlocking_formatter_optimization<long double> = true;785# endif // _LIBCPP_STD_VER >= 23786#endif // _LIBCPP_STD_VER >= 20787 788_LIBCPP_END_NAMESPACE_STD789 790_LIBCPP_POP_MACROS791 792#endif // _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H793