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-exception 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H 11 #define _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H 12 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 <__charconv/chars_format.h> 20 #include <__charconv/to_chars_floating_point.h> 21 #include <__charconv/to_chars_result.h> 22 #include <__concepts/arithmetic.h> 23 #include <__concepts/same_as.h> 24 #include <__config> 25 #include <__format/concepts.h> 26 #include <__format/format_parse_context.h> 27 #include <__format/formatter.h> 28 #include <__format/formatter_integral.h> 29 #include <__format/formatter_output.h> 30 #include <__format/parser_std_format_spec.h> 31 #include <__iterator/concepts.h> 32 #include <__memory/allocator.h> 33 #include <__system_error/errc.h> 34 #include <__type_traits/conditional.h> 35 #include <__utility/move.h> 36 #include <__utility/unreachable.h> 37 #include <cmath> 38 #include <cstddef> 39 40 #ifndef _LIBCPP_HAS_NO_LOCALIZATION 41 # include <locale> 42 #endif 43 44 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 45 # pragma GCC system_header 46 #endif 47 48 _LIBCPP_PUSH_MACROS 49 #include <__undef_macros> 50 51 _LIBCPP_BEGIN_NAMESPACE_STD 52 53 #if _LIBCPP_STD_VER >= 20 54 55 namespace __formatter { 56 57 template <floating_point _Tp> 58 _LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value) { 59 to_chars_result __r = _VSTD::to_chars(__first, __last, __value); 60 _LIBCPP_ASSERT_UNCATEGORIZED(__r.ec == errc(0), "Internal buffer too small"); 61 return __r.ptr; 62 } 63 64 template <floating_point _Tp> 65 _LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value, chars_format __fmt) { 66 to_chars_result __r = _VSTD::to_chars(__first, __last, __value, __fmt); 67 _LIBCPP_ASSERT_UNCATEGORIZED(__r.ec == errc(0), "Internal buffer too small"); 68 return __r.ptr; 69 } 70 71 template <floating_point _Tp> 72 _LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value, chars_format __fmt, int __precision) { 73 to_chars_result __r = _VSTD::to_chars(__first, __last, __value, __fmt, __precision); 74 _LIBCPP_ASSERT_UNCATEGORIZED(__r.ec == errc(0), "Internal buffer too small"); 75 return __r.ptr; 76 } 77 78 // https://en.cppreference.com/w/cpp/language/types#cite_note-1 79 // float min subnormal: +/-0x1p-149 max: +/- 3.402,823,4 10^38 80 // double min subnormal: +/-0x1p-1074 max +/- 1.797,693,134,862,315,7 10^308 81 // long double (x86) min subnormal: +/-0x1p-16446 max: +/- 1.189,731,495,357,231,765,021 10^4932 82 // 83 // The maximum number of digits required for the integral part is based on the 84 // maximum's value power of 10. Every power of 10 requires one additional 85 // decimal digit. 86 // The maximum number of digits required for the fractional part is based on 87 // the minimal subnormal hexadecimal output's power of 10. Every division of a 88 // fraction's binary 1 by 2, requires one additional decimal digit. 89 // 90 // The maximum size of a formatted value depends on the selected output format. 91 // Ignoring the fact the format string can request a precision larger than the 92 // values maximum required, these values are: 93 // 94 // sign 1 code unit 95 // __max_integral 96 // radix point 1 code unit 97 // __max_fractional 98 // exponent character 1 code unit 99 // sign 1 code unit 100 // __max_fractional_value 101 // ----------------------------------- 102 // total 4 code units extra required. 103 // 104 // TODO FMT Optimize the storage to avoid storing digits that are known to be zero. 105 // https://www.exploringbinary.com/maximum-number-of-decimal-digits-in-binary-floating-point-numbers/ 106 107 // TODO FMT Add long double specialization when to_chars has proper long double support. 108 template <class _Tp> 109 struct __traits; 110 111 template <floating_point _Fp> 112 _LIBCPP_HIDE_FROM_ABI constexpr size_t __float_buffer_size(int __precision) { 113 using _Traits = __traits<_Fp>; 114 return 4 + _Traits::__max_integral + __precision + _Traits::__max_fractional_value; 115 } 116 117 template <> 118 struct __traits<float> { 119 static constexpr int __max_integral = 38; 120 static constexpr int __max_fractional = 149; 121 static constexpr int __max_fractional_value = 3; 122 static constexpr size_t __stack_buffer_size = 256; 123 124 static constexpr int __hex_precision_digits = 3; 125 }; 126 127 template <> 128 struct __traits<double> { 129 static constexpr int __max_integral = 308; 130 static constexpr int __max_fractional = 1074; 131 static constexpr int __max_fractional_value = 4; 132 static constexpr size_t __stack_buffer_size = 1024; 133 134 static constexpr int __hex_precision_digits = 4; 135 }; 136 137 /// Helper class to store the conversion buffer. 138 /// 139 /// Depending on the maxium size required for a value, the buffer is allocated 140 /// on the stack or the heap. 141 template <floating_point _Fp> 142 class _LIBCPP_TEMPLATE_VIS __float_buffer { 143 using _Traits = __traits<_Fp>; 144 145 public: 146 // TODO FMT Improve this constructor to do a better estimate. 147 // When using a scientific formatting with a precision of 6 a stack buffer 148 // will always suffice. At the moment that isn't important since floats and 149 // doubles use a stack buffer, unless the precision used in the format string 150 // is large. 151 // When supporting long doubles the __max_integral part becomes 4932 which 152 // may be too much for some platforms. For these cases a better estimate is 153 // required. 154 explicit _LIBCPP_HIDE_FROM_ABI __float_buffer(int __precision) 155 : __precision_(__precision != -1 ? __precision : _Traits::__max_fractional) { 156 157 // When the precision is larger than _Traits::__max_fractional the digits in 158 // the range (_Traits::__max_fractional, precision] will contain the value 159 // zero. There's no need to request to_chars to write these zeros: 160 // - When the value is large a temporary heap buffer needs to be allocated. 161 // - When to_chars writes the values they need to be "copied" to the output: 162 // - char: std::fill on the output iterator is faster than std::copy. 163 // - wchar_t: same argument as char, but additional std::copy won't work. 164 // The input is always a char buffer, so every char in the buffer needs 165 // to be converted from a char to a wchar_t. 166 if (__precision_ > _Traits::__max_fractional) { 167 __num_trailing_zeros_ = __precision_ - _Traits::__max_fractional; 168 __precision_ = _Traits::__max_fractional; 169 } 170 171 __size_ = __formatter::__float_buffer_size<_Fp>(__precision_); 172 if (__size_ > _Traits::__stack_buffer_size) 173 // The allocated buffer's contents don't need initialization. 174 __begin_ = allocator<char>{}.allocate(__size_); 175 else 176 __begin_ = __buffer_; 177 } 178 179 _LIBCPP_HIDE_FROM_ABI ~__float_buffer() { 180 if (__size_ > _Traits::__stack_buffer_size) 181 allocator<char>{}.deallocate(__begin_, __size_); 182 } 183 _LIBCPP_HIDE_FROM_ABI __float_buffer(const __float_buffer&) = delete; 184 _LIBCPP_HIDE_FROM_ABI __float_buffer& operator=(const __float_buffer&) = delete; 185 186 _LIBCPP_HIDE_FROM_ABI char* begin() const { return __begin_; } 187 _LIBCPP_HIDE_FROM_ABI char* end() const { return __begin_ + __size_; } 188 189 _LIBCPP_HIDE_FROM_ABI int __precision() const { return __precision_; } 190 _LIBCPP_HIDE_FROM_ABI int __num_trailing_zeros() const { return __num_trailing_zeros_; } 191 _LIBCPP_HIDE_FROM_ABI void __remove_trailing_zeros() { __num_trailing_zeros_ = 0; } 192 _LIBCPP_HIDE_FROM_ABI void __add_trailing_zeros(int __zeros) { __num_trailing_zeros_ += __zeros; } 193 194 private: 195 int __precision_; 196 int __num_trailing_zeros_{0}; 197 size_t __size_; 198 char* __begin_; 199 char __buffer_[_Traits::__stack_buffer_size]; 200 }; 201 202 struct __float_result { 203 /// Points at the beginning of the integral part in the buffer. 204 /// 205 /// When there's no sign character this points at the start of the buffer. 206 char* __integral; 207 208 /// Points at the radix point, when not present it's the same as \ref __last. 209 char* __radix_point; 210 211 /// Points at the exponent character, when not present it's the same as \ref __last. 212 char* __exponent; 213 214 /// Points beyond the last written element in the buffer. 215 char* __last; 216 }; 217 218 /// Finds the position of the exponent character 'e' at the end of the buffer. 219 /// 220 /// Assuming there is an exponent the input will terminate with 221 /// eSdd and eSdddd (S = sign, d = digit) 222 /// 223 /// \returns a pointer to the exponent or __last when not found. 224 constexpr inline _LIBCPP_HIDE_FROM_ABI char* __find_exponent(char* __first, char* __last) { 225 ptrdiff_t __size = __last - __first; 226 if (__size >= 4) { 227 __first = __last - _VSTD::min(__size, ptrdiff_t(6)); 228 for (; __first != __last - 3; ++__first) { 229 if (*__first == 'e') 230 return __first; 231 } 232 } 233 return __last; 234 } 235 236 template <class _Fp, class _Tp> 237 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_default(const __float_buffer<_Fp>& __buffer, _Tp __value, 238 char* __integral) { 239 __float_result __result; 240 __result.__integral = __integral; 241 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value); 242 243 __result.__exponent = __formatter::__find_exponent(__result.__integral, __result.__last); 244 245 // Constrains: 246 // - There's at least one decimal digit before the radix point. 247 // - The radix point, when present, is placed before the exponent. 248 __result.__radix_point = _VSTD::find(__result.__integral + 1, __result.__exponent, '.'); 249 250 // When the radix point isn't found its position is the exponent instead of 251 // __result.__last. 252 if (__result.__radix_point == __result.__exponent) 253 __result.__radix_point = __result.__last; 254 255 // clang-format off 256 _LIBCPP_ASSERT_UNCATEGORIZED((__result.__integral != __result.__last) && 257 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 258 (__result.__exponent == __result.__last || *__result.__exponent == 'e'), 259 "Post-condition failure."); 260 // clang-format on 261 262 return __result; 263 } 264 265 template <class _Fp, class _Tp> 266 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_hexadecimal_lower_case(const __float_buffer<_Fp>& __buffer, 267 _Tp __value, int __precision, 268 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 else 274 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::hex, __precision); 275 276 // H = one or more hex-digits 277 // S = sign 278 // D = one or more decimal-digits 279 // When the fractional part is zero and no precision the output is 0p+0 280 // else the output is 0.HpSD 281 // 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 minimum 286 // 0.hpSd 287 // ^-- last 288 // ^---- integral = end of search 289 // ^-------- start of search 290 // 0123456 291 // 292 // Four digits is the maximum 293 // 0.hpSdddd 294 // ^-- last 295 // ^---- integral = end of search 296 // ^-------- start of search 297 // 0123456789 298 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 = _VSTD::find(__first, __last, 'p'); 303 } else { 304 __result.__radix_point = __result.__last; 305 __result.__exponent = __first; 306 } 307 308 // clang-format off 309 _LIBCPP_ASSERT_UNCATEGORIZED((__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 on 314 315 return __result; 316 } 317 318 template <class _Fp, class _Tp> 319 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_hexadecimal_upper_case(const __float_buffer<_Fp>& __buffer, 320 _Tp __value, int __precision, 321 char* __integral) { 322 __float_result __result = 323 __formatter::__format_buffer_hexadecimal_lower_case(__buffer, __value, __precision, __integral); 324 _VSTD::transform(__result.__integral, __result.__exponent, __result.__integral, __hex_to_upper); 325 *__result.__exponent = 'P'; 326 return __result; 327 } 328 329 template <class _Fp, class _Tp> 330 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_scientific_lower_case(const __float_buffer<_Fp>& __buffer, 331 _Tp __value, int __precision, 332 char* __integral) { 333 __float_result __result; 334 __result.__integral = __integral; 335 __result.__last = 336 __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::scientific, __precision); 337 338 char* __first = __integral + 1; 339 _LIBCPP_ASSERT_UNCATEGORIZED(__first != __result.__last, "No exponent present"); 340 if (*__first == '.') { 341 __result.__radix_point = __first; 342 __result.__exponent = __formatter::__find_exponent(__first + 1, __result.__last); 343 } else { 344 __result.__radix_point = __result.__last; 345 __result.__exponent = __first; 346 } 347 348 // clang-format off 349 _LIBCPP_ASSERT_UNCATEGORIZED((__result.__integral != __result.__last) && 350 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 351 (__result.__exponent != __result.__last && *__result.__exponent == 'e'), 352 "Post-condition failure."); 353 // clang-format on 354 return __result; 355 } 356 357 template <class _Fp, class _Tp> 358 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_scientific_upper_case(const __float_buffer<_Fp>& __buffer, 359 _Tp __value, int __precision, 360 char* __integral) { 361 __float_result __result = 362 __formatter::__format_buffer_scientific_lower_case(__buffer, __value, __precision, __integral); 363 *__result.__exponent = 'E'; 364 return __result; 365 } 366 367 template <class _Fp, class _Tp> 368 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_fixed(const __float_buffer<_Fp>& __buffer, _Tp __value, 369 int __precision, char* __integral) { 370 __float_result __result; 371 __result.__integral = __integral; 372 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::fixed, __precision); 373 374 // When there's no precision there's no radix point. 375 // Else the radix point is placed at __precision + 1 from the end. 376 // By converting __precision to a bool the subtraction can be done 377 // unconditionally. 378 __result.__radix_point = __result.__last - (__precision + bool(__precision)); 379 __result.__exponent = __result.__last; 380 381 // clang-format off 382 _LIBCPP_ASSERT_UNCATEGORIZED((__result.__integral != __result.__last) && 383 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 384 (__result.__exponent == __result.__last), 385 "Post-condition failure."); 386 // clang-format on 387 return __result; 388 } 389 390 template <class _Fp, class _Tp> 391 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_general_lower_case(__float_buffer<_Fp>& __buffer, _Tp __value, 392 int __precision, char* __integral) { 393 394 __buffer.__remove_trailing_zeros(); 395 396 __float_result __result; 397 __result.__integral = __integral; 398 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::general, __precision); 399 400 char* __first = __integral + 1; 401 if (__first == __result.__last) { 402 __result.__radix_point = __result.__last; 403 __result.__exponent = __result.__last; 404 } else { 405 __result.__exponent = __formatter::__find_exponent(__first, __result.__last); 406 if (__result.__exponent != __result.__last) 407 // In scientific mode if there's a radix point it will always be after 408 // the first digit. (This is the position __first points at). 409 __result.__radix_point = *__first == '.' ? __first : __result.__last; 410 else { 411 // In fixed mode the algorithm truncates trailing spaces and possibly the 412 // radix point. There's no good guess for the position of the radix point 413 // therefore scan the output after the first digit. 414 __result.__radix_point = _VSTD::find(__first, __result.__last, '.'); 415 } 416 } 417 418 // clang-format off 419 _LIBCPP_ASSERT_UNCATEGORIZED((__result.__integral != __result.__last) && 420 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 421 (__result.__exponent == __result.__last || *__result.__exponent == 'e'), 422 "Post-condition failure."); 423 // clang-format on 424 425 return __result; 426 } 427 428 template <class _Fp, class _Tp> 429 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_general_upper_case(__float_buffer<_Fp>& __buffer, _Tp __value, 430 int __precision, char* __integral) { 431 __float_result __result = __formatter::__format_buffer_general_lower_case(__buffer, __value, __precision, __integral); 432 if (__result.__exponent != __result.__last) 433 *__result.__exponent = 'E'; 434 return __result; 435 } 436 437 /// Fills the buffer with the data based on the requested formatting. 438 /// 439 /// This function, when needed, turns the characters to upper case and 440 /// determines the "interesting" locations which are returned to the caller. 441 /// 442 /// This means the caller never has to convert the contents of the buffer to 443 /// upper case or search for radix points and the location of the exponent. 444 /// This gives a bit of overhead. The original code didn't do that, but due 445 /// to the number of possible additional work needed to turn this number to 446 /// the proper output the code was littered with tests for upper cases and 447 /// searches for radix points and exponents. 448 /// - When a precision larger than the type's precision is selected 449 /// additional zero characters need to be written before the exponent. 450 /// - alternate form needs to add a radix point when not present. 451 /// - localization needs to do grouping in the integral part. 452 template <class _Fp, class _Tp> 453 // TODO FMT _Fp should just be _Tp when to_chars has proper long double support. 454 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer( 455 __float_buffer<_Fp>& __buffer, 456 _Tp __value, 457 bool __negative, 458 bool __has_precision, 459 __format_spec::__sign __sign, 460 __format_spec::__type __type) { 461 char* __first = __formatter::__insert_sign(__buffer.begin(), __negative, __sign); 462 switch (__type) { 463 case __format_spec::__type::__default: 464 if (__has_precision) 465 return __formatter::__format_buffer_general_lower_case(__buffer, __value, __buffer.__precision(), __first); 466 else 467 return __formatter::__format_buffer_default(__buffer, __value, __first); 468 469 case __format_spec::__type::__hexfloat_lower_case: 470 return __formatter::__format_buffer_hexadecimal_lower_case( 471 __buffer, __value, __has_precision ? __buffer.__precision() : -1, __first); 472 473 case __format_spec::__type::__hexfloat_upper_case: 474 return __formatter::__format_buffer_hexadecimal_upper_case( 475 __buffer, __value, __has_precision ? __buffer.__precision() : -1, __first); 476 477 case __format_spec::__type::__scientific_lower_case: 478 return __formatter::__format_buffer_scientific_lower_case(__buffer, __value, __buffer.__precision(), __first); 479 480 case __format_spec::__type::__scientific_upper_case: 481 return __formatter::__format_buffer_scientific_upper_case(__buffer, __value, __buffer.__precision(), __first); 482 483 case __format_spec::__type::__fixed_lower_case: 484 case __format_spec::__type::__fixed_upper_case: 485 return __formatter::__format_buffer_fixed(__buffer, __value, __buffer.__precision(), __first); 486 487 case __format_spec::__type::__general_lower_case: 488 return __formatter::__format_buffer_general_lower_case(__buffer, __value, __buffer.__precision(), __first); 489 490 case __format_spec::__type::__general_upper_case: 491 return __formatter::__format_buffer_general_upper_case(__buffer, __value, __buffer.__precision(), __first); 492 493 default: 494 _LIBCPP_ASSERT_UNCATEGORIZED(false, "The parser should have validated the type"); 495 __libcpp_unreachable(); 496 } 497 } 498 499 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 500 template <class _OutIt, class _Fp, class _CharT> 501 _LIBCPP_HIDE_FROM_ABI _OutIt __format_locale_specific_form( 502 _OutIt __out_it, 503 const __float_buffer<_Fp>& __buffer, 504 const __float_result& __result, 505 _VSTD::locale __loc, 506 __format_spec::__parsed_specifications<_CharT> __specs) { 507 const auto& __np = std::use_facet<numpunct<_CharT>>(__loc); 508 string __grouping = __np.grouping(); 509 char* __first = __result.__integral; 510 // When no radix point or exponent are present __last will be __result.__last. 511 char* __last = _VSTD::min(__result.__radix_point, __result.__exponent); 512 513 ptrdiff_t __digits = __last - __first; 514 if (!__grouping.empty()) { 515 if (__digits <= __grouping[0]) 516 __grouping.clear(); 517 else 518 __grouping = __formatter::__determine_grouping(__digits, __grouping); 519 } 520 521 ptrdiff_t __size = 522 __result.__last - __buffer.begin() + // Formatted string 523 __buffer.__num_trailing_zeros() + // Not yet rendered zeros 524 __grouping.size() - // Grouping contains one 525 !__grouping.empty(); // additional character 526 527 __formatter::__padding_size_result __padding = {0, 0}; 528 bool __zero_padding = __specs.__alignment_ == __format_spec::__alignment::__zero_padding; 529 if (__size < __specs.__width_) { 530 if (__zero_padding) { 531 __specs.__alignment_ = __format_spec::__alignment::__right; 532 __specs.__fill_.__data[0] = _CharT('0'); 533 } 534 535 __padding = __formatter::__padding_size(__size, __specs.__width_, __specs.__alignment_); 536 } 537 538 // sign and (zero padding or alignment) 539 if (__zero_padding && __first != __buffer.begin()) 540 *__out_it++ = *__buffer.begin(); 541 __out_it = __formatter::__fill(_VSTD::move(__out_it), __padding.__before_, __specs.__fill_); 542 if (!__zero_padding && __first != __buffer.begin()) 543 *__out_it++ = *__buffer.begin(); 544 545 // integral part 546 if (__grouping.empty()) { 547 __out_it = __formatter::__copy(__first, __digits, _VSTD::move(__out_it)); 548 } else { 549 auto __r = __grouping.rbegin(); 550 auto __e = __grouping.rend() - 1; 551 _CharT __sep = __np.thousands_sep(); 552 // The output is divided in small groups of numbers to write: 553 // - A group before the first separator. 554 // - A separator and a group, repeated for the number of separators. 555 // - A group after the last separator. 556 // This loop achieves that process by testing the termination condition 557 // midway in the loop. 558 while (true) { 559 __out_it = __formatter::__copy(__first, *__r, _VSTD::move(__out_it)); 560 __first += *__r; 561 562 if (__r == __e) 563 break; 564 565 ++__r; 566 *__out_it++ = __sep; 567 } 568 } 569 570 // fractional part 571 if (__result.__radix_point != __result.__last) { 572 *__out_it++ = __np.decimal_point(); 573 __out_it = __formatter::__copy(__result.__radix_point + 1, __result.__exponent, _VSTD::move(__out_it)); 574 __out_it = __formatter::__fill(_VSTD::move(__out_it), __buffer.__num_trailing_zeros(), _CharT('0')); 575 } 576 577 // exponent 578 if (__result.__exponent != __result.__last) 579 __out_it = __formatter::__copy(__result.__exponent, __result.__last, _VSTD::move(__out_it)); 580 581 // alignment 582 return __formatter::__fill(_VSTD::move(__out_it), __padding.__after_, __specs.__fill_); 583 } 584 # endif // _LIBCPP_HAS_NO_LOCALIZATION 585 586 template <class _OutIt, class _CharT> 587 _LIBCPP_HIDE_FROM_ABI _OutIt __format_floating_point_non_finite( 588 _OutIt __out_it, __format_spec::__parsed_specifications<_CharT> __specs, bool __negative, bool __isnan) { 589 char __buffer[4]; 590 char* __last = __formatter::__insert_sign(__buffer, __negative, __specs.__std_.__sign_); 591 592 // to_chars can return inf, infinity, nan, and nan(n-char-sequence). 593 // The format library requires inf and nan. 594 // All in one expression to avoid dangling references. 595 bool __upper_case = 596 __specs.__std_.__type_ == __format_spec::__type::__hexfloat_upper_case || 597 __specs.__std_.__type_ == __format_spec::__type::__scientific_upper_case || 598 __specs.__std_.__type_ == __format_spec::__type::__fixed_upper_case || 599 __specs.__std_.__type_ == __format_spec::__type::__general_upper_case; 600 __last = _VSTD::copy_n(&("infnanINFNAN"[6 * __upper_case + 3 * __isnan]), 3, __last); 601 602 // [format.string.std]/13 603 // A zero (0) character preceding the width field pads the field with 604 // leading zeros (following any indication of sign or base) to the field 605 // width, except when applied to an infinity or NaN. 606 if (__specs.__alignment_ == __format_spec::__alignment::__zero_padding) 607 __specs.__alignment_ = __format_spec::__alignment::__right; 608 609 return __formatter::__write(__buffer, __last, _VSTD::move(__out_it), __specs); 610 } 611 612 /// Writes additional zero's for the precision before the exponent. 613 /// This is used when the precision requested in the format string is larger 614 /// than the maximum precision of the floating-point type. These precision 615 /// digits are always 0. 616 /// 617 /// \param __exponent The location of the exponent character. 618 /// \param __num_trailing_zeros The number of 0's to write before the exponent 619 /// character. 620 template <class _CharT, class _ParserCharT> 621 _LIBCPP_HIDE_FROM_ABI auto __write_using_trailing_zeros( 622 const _CharT* __first, 623 const _CharT* __last, 624 output_iterator<const _CharT&> auto __out_it, 625 __format_spec::__parsed_specifications<_ParserCharT> __specs, 626 size_t __size, 627 const _CharT* __exponent, 628 size_t __num_trailing_zeros) -> decltype(__out_it) { 629 _LIBCPP_ASSERT_UNCATEGORIZED(__first <= __last, "Not a valid range"); 630 _LIBCPP_ASSERT_UNCATEGORIZED(__num_trailing_zeros > 0, 631 "The overload not writing trailing zeros should have been used"); 632 633 __padding_size_result __padding = 634 __formatter::__padding_size(__size + __num_trailing_zeros, __specs.__width_, __specs.__alignment_); 635 __out_it = __formatter::__fill(_VSTD::move(__out_it), __padding.__before_, __specs.__fill_); 636 __out_it = __formatter::__copy(__first, __exponent, _VSTD::move(__out_it)); 637 __out_it = __formatter::__fill(_VSTD::move(__out_it), __num_trailing_zeros, _CharT('0')); 638 __out_it = __formatter::__copy(__exponent, __last, _VSTD::move(__out_it)); 639 return __formatter::__fill(_VSTD::move(__out_it), __padding.__after_, __specs.__fill_); 640 } 641 642 643 template <floating_point _Tp, class _CharT, class _FormatContext> 644 _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator 645 __format_floating_point(_Tp __value, _FormatContext& __ctx, __format_spec::__parsed_specifications<_CharT> __specs) { 646 bool __negative = _VSTD::signbit(__value); 647 648 if (!_VSTD::isfinite(__value)) [[unlikely]] 649 return __formatter::__format_floating_point_non_finite(__ctx.out(), __specs, __negative, _VSTD::isnan(__value)); 650 651 // Depending on the std-format-spec string the sign and the value 652 // might not be outputted together: 653 // - zero-padding may insert additional '0' characters. 654 // Therefore the value is processed as a non negative value. 655 // The function @ref __insert_sign will insert a '-' when the value was 656 // negative. 657 658 if (__negative) 659 __value = -__value; 660 661 // TODO FMT _Fp should just be _Tp when to_chars has proper long double support. 662 using _Fp = conditional_t<same_as<_Tp, long double>, double, _Tp>; 663 // Force the type of the precision to avoid -1 to become an unsigned value. 664 __float_buffer<_Fp> __buffer(__specs.__precision_); 665 __float_result __result = __formatter::__format_buffer( 666 __buffer, __value, __negative, (__specs.__has_precision()), __specs.__std_.__sign_, __specs.__std_.__type_); 667 668 if (__specs.__std_.__alternate_form_) { 669 if (__result.__radix_point == __result.__last) { 670 *__result.__last++ = '.'; 671 672 // When there is an exponent the point needs to be moved before the 673 // exponent. When there's no exponent the rotate does nothing. Since 674 // rotate tests whether the operation is a nop, call it unconditionally. 675 _VSTD::rotate(__result.__exponent, __result.__last - 1, __result.__last); 676 __result.__radix_point = __result.__exponent; 677 678 // The radix point is always placed before the exponent. 679 // - No exponent needs to point to the new last. 680 // - An exponent needs to move one position to the right. 681 // So it's safe to increment the value unconditionally. 682 ++__result.__exponent; 683 } 684 685 // [format.string.std]/6 686 // In addition, for g and G conversions, trailing zeros are not removed 687 // from the result. 688 // 689 // If the type option for a floating-point type is none it may use the 690 // general formatting, but it's not a g or G conversion. So in that case 691 // the formatting should not append trailing zeros. 692 bool __is_general = __specs.__std_.__type_ == __format_spec::__type::__general_lower_case || 693 __specs.__std_.__type_ == __format_spec::__type::__general_upper_case; 694 695 if (__is_general) { 696 // https://en.cppreference.com/w/c/io/fprintf 697 // Let P equal the precision if nonzero, 6 if the precision is not 698 // specified, or 1 if the precision is 0. Then, if a conversion with 699 // style E would have an exponent of X: 700 int __p = _VSTD::max(1, (__specs.__has_precision() ? __specs.__precision_ : 6)); 701 if (__result.__exponent == __result.__last) 702 // if P > X >= -4, the conversion is with style f or F and precision P - 1 - X. 703 // By including the radix point it calculates P - (1 + X) 704 __p -= __result.__radix_point - __result.__integral; 705 else 706 // otherwise, the conversion is with style e or E and precision P - 1. 707 --__p; 708 709 ptrdiff_t __precision = (__result.__exponent - __result.__radix_point) - 1; 710 if (__precision < __p) 711 __buffer.__add_trailing_zeros(__p - __precision); 712 } 713 } 714 715 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 716 if (__specs.__std_.__locale_specific_form_) 717 return __formatter::__format_locale_specific_form(__ctx.out(), __buffer, __result, __ctx.locale(), __specs); 718 # endif 719 720 ptrdiff_t __size = __result.__last - __buffer.begin(); 721 int __num_trailing_zeros = __buffer.__num_trailing_zeros(); 722 if (__size + __num_trailing_zeros >= __specs.__width_) { 723 if (__num_trailing_zeros && __result.__exponent != __result.__last) 724 // Insert trailing zeros before exponent character. 725 return __formatter::__copy( 726 __result.__exponent, 727 __result.__last, 728 __formatter::__fill(__formatter::__copy(__buffer.begin(), __result.__exponent, __ctx.out()), 729 __num_trailing_zeros, 730 _CharT('0'))); 731 732 return __formatter::__fill( 733 __formatter::__copy(__buffer.begin(), __result.__last, __ctx.out()), __num_trailing_zeros, _CharT('0')); 734 } 735 736 auto __out_it = __ctx.out(); 737 char* __first = __buffer.begin(); 738 if (__specs.__alignment_ == __format_spec::__alignment ::__zero_padding) { 739 // When there is a sign output it before the padding. Note the __size 740 // doesn't need any adjustment, regardless whether the sign is written 741 // here or in __formatter::__write. 742 if (__first != __result.__integral) 743 *__out_it++ = *__first++; 744 // After the sign is written, zero padding is the same a right alignment 745 // with '0'. 746 __specs.__alignment_ = __format_spec::__alignment::__right; 747 __specs.__fill_.__data[0] = _CharT('0'); 748 } 749 750 if (__num_trailing_zeros) 751 return __formatter::__write_using_trailing_zeros( 752 __first, __result.__last, _VSTD::move(__out_it), __specs, __size, __result.__exponent, __num_trailing_zeros); 753 754 return __formatter::__write(__first, __result.__last, _VSTD::move(__out_it), __specs, __size); 755 } 756 757 } // namespace __formatter 758 759 template <__fmt_char_type _CharT> 760 struct _LIBCPP_TEMPLATE_VIS __formatter_floating_point { 761 public: 762 template <class _ParseContext> 763 _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) { 764 typename _ParseContext::iterator __result = __parser_.__parse(__ctx, __format_spec::__fields_floating_point); 765 __format_spec::__process_parsed_floating_point(__parser_, "a floating-point"); 766 return __result; 767 } 768 769 template <floating_point _Tp, class _FormatContext> 770 _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator format(_Tp __value, _FormatContext& __ctx) const { 771 return __formatter::__format_floating_point(__value, __ctx, __parser_.__get_parsed_std_specifications(__ctx)); 772 } 773 774 __format_spec::__parser<_CharT> __parser_; 775 }; 776 777 template <__fmt_char_type _CharT> 778 struct _LIBCPP_TEMPLATE_VIS formatter<float, _CharT> 779 : public __formatter_floating_point<_CharT> {}; 780 template <__fmt_char_type _CharT> 781 struct _LIBCPP_TEMPLATE_VIS formatter<double, _CharT> 782 : public __formatter_floating_point<_CharT> {}; 783 template <__fmt_char_type _CharT> 784 struct _LIBCPP_TEMPLATE_VIS formatter<long double, _CharT> 785 : public __formatter_floating_point<_CharT> {}; 786 787 #endif //_LIBCPP_STD_VER >= 20 788 789 _LIBCPP_END_NAMESPACE_STD 790 791 _LIBCPP_POP_MACROS 792 793 #endif // _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H 794