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.h> 14 #include <__algorithm/copy_n.h> 15 #include <__algorithm/fill_n.h> 16 #include <__algorithm/find.h> 17 #include <__algorithm/min.h> 18 #include <__algorithm/rotate.h> 19 #include <__algorithm/transform.h> 20 #include <__concepts/arithmetic.h> 21 #include <__concepts/same_as.h> 22 #include <__config> 23 #include <__format/format_fwd.h> 24 #include <__format/format_parse_context.h> 25 #include <__format/formatter.h> 26 #include <__format/formatter_integral.h> 27 #include <__format/formatter_output.h> 28 #include <__format/parser_std_format_spec.h> 29 #include <__memory/allocator.h> 30 #include <__utility/move.h> 31 #include <__utility/unreachable.h> 32 #include <charconv> 33 34 #ifndef _LIBCPP_HAS_NO_LOCALIZATION 35 # include <locale> 36 #endif 37 38 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 39 # pragma GCC system_header 40 #endif 41 42 _LIBCPP_PUSH_MACROS 43 #include <__undef_macros> 44 45 _LIBCPP_BEGIN_NAMESPACE_STD 46 47 #if _LIBCPP_STD_VER > 17 48 49 namespace __formatter { 50 51 template <floating_point _Tp> 52 _LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value) { 53 to_chars_result __r = _VSTD::to_chars(__first, __last, __value); 54 _LIBCPP_ASSERT(__r.ec == errc(0), "Internal buffer too small"); 55 return __r.ptr; 56 } 57 58 template <floating_point _Tp> 59 _LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value, chars_format __fmt) { 60 to_chars_result __r = _VSTD::to_chars(__first, __last, __value, __fmt); 61 _LIBCPP_ASSERT(__r.ec == errc(0), "Internal buffer too small"); 62 return __r.ptr; 63 } 64 65 template <floating_point _Tp> 66 _LIBCPP_HIDE_FROM_ABI char* __to_buffer(char* __first, char* __last, _Tp __value, chars_format __fmt, int __precision) { 67 to_chars_result __r = _VSTD::to_chars(__first, __last, __value, __fmt, __precision); 68 _LIBCPP_ASSERT(__r.ec == errc(0), "Internal buffer too small"); 69 return __r.ptr; 70 } 71 72 // https://en.cppreference.com/w/cpp/language/types#cite_note-1 73 // float min subnormal: +/-0x1p-149 max: +/- 3.402,823,4 10^38 74 // double min subnormal: +/-0x1p-1074 max +/- 1.797,693,134,862,315,7 10^308 75 // long double (x86) min subnormal: +/-0x1p-16446 max: +/- 1.189,731,495,357,231,765,021 10^4932 76 // 77 // The maximum number of digits required for the integral part is based on the 78 // maximum's value power of 10. Every power of 10 requires one additional 79 // decimal digit. 80 // The maximum number of digits required for the fractional part is based on 81 // the minimal subnormal hexadecimal output's power of 10. Every division of a 82 // fraction's binary 1 by 2, requires one additional decimal digit. 83 // 84 // The maximum size of a formatted value depends on the selected output format. 85 // Ignoring the fact the format string can request a precision larger than the 86 // values maximum required, these values are: 87 // 88 // sign 1 code unit 89 // __max_integral 90 // radix point 1 code unit 91 // __max_fractional 92 // exponent character 1 code unit 93 // sign 1 code unit 94 // __max_fractional_value 95 // ----------------------------------- 96 // total 4 code units extra required. 97 // 98 // TODO FMT Optimize the storage to avoid storing digits that are known to be zero. 99 // https://www.exploringbinary.com/maximum-number-of-decimal-digits-in-binary-floating-point-numbers/ 100 101 // TODO FMT Add long double specialization when to_chars has proper long double support. 102 template <class _Tp> 103 struct __traits; 104 105 template <floating_point _Fp> 106 static constexpr size_t __float_buffer_size(int __precision) { 107 using _Traits = __traits<_Fp>; 108 return 4 + _Traits::__max_integral + __precision + _Traits::__max_fractional_value; 109 } 110 111 template <> 112 struct __traits<float> { 113 static constexpr int __max_integral = 38; 114 static constexpr int __max_fractional = 149; 115 static constexpr int __max_fractional_value = 3; 116 static constexpr size_t __stack_buffer_size = 256; 117 118 static constexpr int __hex_precision_digits = 3; 119 }; 120 121 template <> 122 struct __traits<double> { 123 static constexpr int __max_integral = 308; 124 static constexpr int __max_fractional = 1074; 125 static constexpr int __max_fractional_value = 4; 126 static constexpr size_t __stack_buffer_size = 1024; 127 128 static constexpr int __hex_precision_digits = 4; 129 }; 130 131 /// Helper class to store the conversion buffer. 132 /// 133 /// Depending on the maxium size required for a value, the buffer is allocated 134 /// on the stack or the heap. 135 template <floating_point _Fp> 136 class _LIBCPP_TEMPLATE_VIS __float_buffer { 137 using _Traits = __traits<_Fp>; 138 139 public: 140 // TODO FMT Improve this constructor to do a better estimate. 141 // When using a scientific formatting with a precision of 6 a stack buffer 142 // will always suffice. At the moment that isn't important since floats and 143 // doubles use a stack buffer, unless the precision used in the format string 144 // is large. 145 // When supporting long doubles the __max_integral part becomes 4932 which 146 // may be too much for some platforms. For these cases a better estimate is 147 // required. 148 explicit _LIBCPP_HIDE_FROM_ABI __float_buffer(int __precision) 149 : __precision_(__precision != -1 ? __precision : _Traits::__max_fractional) { 150 151 // When the precision is larger than _Traits::__max_fractional the digits in 152 // the range (_Traits::__max_fractional, precision] will contain the value 153 // zero. There's no need to request to_chars to write these zeros: 154 // - When the value is large a temporary heap buffer needs to be allocated. 155 // - When to_chars writes the values they need to be "copied" to the output: 156 // - char: std::fill on the output iterator is faster than std::copy. 157 // - wchar_t: same argument as char, but additional std::copy won't work. 158 // The input is always a char buffer, so every char in the buffer needs 159 // to be converted from a char to a wchar_t. 160 if (__precision_ > _Traits::__max_fractional) { 161 __num_trailing_zeros_ = __precision_ - _Traits::__max_fractional; 162 __precision_ = _Traits::__max_fractional; 163 } 164 165 __size_ = __formatter::__float_buffer_size<_Fp>(__precision_); 166 if (__size_ > _Traits::__stack_buffer_size) 167 // The allocated buffer's contents don't need initialization. 168 __begin_ = allocator<char>{}.allocate(__size_); 169 else 170 __begin_ = __buffer_; 171 } 172 173 _LIBCPP_HIDE_FROM_ABI ~__float_buffer() { 174 if (__size_ > _Traits::__stack_buffer_size) 175 allocator<char>{}.deallocate(__begin_, __size_); 176 } 177 _LIBCPP_HIDE_FROM_ABI __float_buffer(const __float_buffer&) = delete; 178 _LIBCPP_HIDE_FROM_ABI __float_buffer& operator=(const __float_buffer&) = delete; 179 180 _LIBCPP_HIDE_FROM_ABI char* begin() const { return __begin_; } 181 _LIBCPP_HIDE_FROM_ABI char* end() const { return __begin_ + __size_; } 182 183 _LIBCPP_HIDE_FROM_ABI int __precision() const { return __precision_; } 184 _LIBCPP_HIDE_FROM_ABI int __num_trailing_zeros() const { return __num_trailing_zeros_; } 185 _LIBCPP_HIDE_FROM_ABI void __remove_trailing_zeros() { __num_trailing_zeros_ = 0; } 186 187 private: 188 int __precision_; 189 int __num_trailing_zeros_{0}; 190 size_t __size_; 191 char* __begin_; 192 char __buffer_[_Traits::__stack_buffer_size]; 193 }; 194 195 struct __float_result { 196 /// Points at the beginning of the integral part in the buffer. 197 /// 198 /// When there's no sign character this points at the start of the buffer. 199 char* __integral; 200 201 /// Points at the radix point, when not present it's the same as \ref __last. 202 char* __radix_point; 203 204 /// Points at the exponent character, when not present it's the same as \ref __last. 205 char* __exponent; 206 207 /// Points beyond the last written element in the buffer. 208 char* __last; 209 }; 210 211 /// Finds the position of the exponent character 'e' at the end of the buffer. 212 /// 213 /// Assuming there is an exponent the input will terminate with 214 /// eSdd and eSdddd (S = sign, d = digit) 215 /// 216 /// \returns a pointer to the exponent or __last when not found. 217 constexpr inline _LIBCPP_HIDE_FROM_ABI char* __find_exponent(char* __first, char* __last) { 218 ptrdiff_t __size = __last - __first; 219 if (__size > 4) { 220 __first = __last - _VSTD::min(__size, ptrdiff_t(6)); 221 for (; __first != __last - 3; ++__first) { 222 if (*__first == 'e') 223 return __first; 224 } 225 } 226 return __last; 227 } 228 229 template <class _Fp, class _Tp> 230 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_default(const __float_buffer<_Fp>& __buffer, _Tp __value, 231 char* __integral) { 232 __float_result __result; 233 __result.__integral = __integral; 234 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value); 235 236 __result.__exponent = __formatter::__find_exponent(__result.__integral, __result.__last); 237 238 // Constrains: 239 // - There's at least one decimal digit before the radix point. 240 // - The radix point, when present, is placed before the exponent. 241 __result.__radix_point = _VSTD::find(__result.__integral + 1, __result.__exponent, '.'); 242 243 // When the radix point isn't found its position is the exponent instead of 244 // __result.__last. 245 if (__result.__radix_point == __result.__exponent) 246 __result.__radix_point = __result.__last; 247 248 // clang-format off 249 _LIBCPP_ASSERT((__result.__integral != __result.__last) && 250 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 251 (__result.__exponent == __result.__last || *__result.__exponent == 'e'), 252 "Post-condition failure."); 253 // clang-format on 254 255 return __result; 256 } 257 258 template <class _Fp, class _Tp> 259 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_hexadecimal_lower_case(const __float_buffer<_Fp>& __buffer, 260 _Tp __value, int __precision, 261 char* __integral) { 262 __float_result __result; 263 __result.__integral = __integral; 264 if (__precision == -1) 265 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::hex); 266 else 267 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::hex, __precision); 268 269 // H = one or more hex-digits 270 // S = sign 271 // D = one or more decimal-digits 272 // When the fractional part is zero and no precision the output is 0p+0 273 // else the output is 0.HpSD 274 // So testing the second position can differentiate between these two cases. 275 char* __first = __integral + 1; 276 if (*__first == '.') { 277 __result.__radix_point = __first; 278 // One digit is the minimum 279 // 0.hpSd 280 // ^-- last 281 // ^---- integral = end of search 282 // ^-------- start of search 283 // 0123456 284 // 285 // Four digits is the maximum 286 // 0.hpSdddd 287 // ^-- last 288 // ^---- integral = end of search 289 // ^-------- start of search 290 // 0123456789 291 static_assert(__traits<_Fp>::__hex_precision_digits <= 4, "Guard against possible underflow."); 292 293 char* __last = __result.__last - 2; 294 __first = __last - __traits<_Fp>::__hex_precision_digits; 295 __result.__exponent = _VSTD::find(__first, __last, 'p'); 296 } else { 297 __result.__radix_point = __result.__last; 298 __result.__exponent = __first; 299 } 300 301 // clang-format off 302 _LIBCPP_ASSERT((__result.__integral != __result.__last) && 303 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 304 (__result.__exponent != __result.__last && *__result.__exponent == 'p'), 305 "Post-condition failure."); 306 // clang-format on 307 308 return __result; 309 } 310 311 template <class _Fp, class _Tp> 312 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_hexadecimal_upper_case(const __float_buffer<_Fp>& __buffer, 313 _Tp __value, int __precision, 314 char* __integral) { 315 __float_result __result = 316 __formatter::__format_buffer_hexadecimal_lower_case(__buffer, __value, __precision, __integral); 317 _VSTD::transform(__result.__integral, __result.__exponent, __result.__integral, __hex_to_upper); 318 *__result.__exponent = 'P'; 319 return __result; 320 } 321 322 template <class _Fp, class _Tp> 323 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_scientific_lower_case(const __float_buffer<_Fp>& __buffer, 324 _Tp __value, int __precision, 325 char* __integral) { 326 __float_result __result; 327 __result.__integral = __integral; 328 __result.__last = 329 __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::scientific, __precision); 330 331 char* __first = __integral + 1; 332 _LIBCPP_ASSERT(__first != __result.__last, "No exponent present"); 333 if (*__first == '.') { 334 __result.__radix_point = __first; 335 __result.__exponent = __formatter::__find_exponent(__first + 1, __result.__last); 336 } else { 337 __result.__radix_point = __result.__last; 338 __result.__exponent = __first; 339 } 340 341 // clang-format off 342 _LIBCPP_ASSERT((__result.__integral != __result.__last) && 343 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 344 (__result.__exponent != __result.__last && *__result.__exponent == 'e'), 345 "Post-condition failure."); 346 // clang-format on 347 return __result; 348 } 349 350 template <class _Fp, class _Tp> 351 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_scientific_upper_case(const __float_buffer<_Fp>& __buffer, 352 _Tp __value, int __precision, 353 char* __integral) { 354 __float_result __result = 355 __formatter::__format_buffer_scientific_lower_case(__buffer, __value, __precision, __integral); 356 *__result.__exponent = 'E'; 357 return __result; 358 } 359 360 template <class _Fp, class _Tp> 361 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_fixed(const __float_buffer<_Fp>& __buffer, _Tp __value, 362 int __precision, char* __integral) { 363 __float_result __result; 364 __result.__integral = __integral; 365 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::fixed, __precision); 366 367 // When there's no precision there's no radix point. 368 // Else the radix point is placed at __precision + 1 from the end. 369 // By converting __precision to a bool the subtraction can be done 370 // unconditionally. 371 __result.__radix_point = __result.__last - (__precision + bool(__precision)); 372 __result.__exponent = __result.__last; 373 374 // clang-format off 375 _LIBCPP_ASSERT((__result.__integral != __result.__last) && 376 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 377 (__result.__exponent == __result.__last), 378 "Post-condition failure."); 379 // clang-format on 380 return __result; 381 } 382 383 template <class _Fp, class _Tp> 384 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_general_lower_case(__float_buffer<_Fp>& __buffer, _Tp __value, 385 int __precision, char* __integral) { 386 387 __buffer.__remove_trailing_zeros(); 388 389 __float_result __result; 390 __result.__integral = __integral; 391 __result.__last = __formatter::__to_buffer(__integral, __buffer.end(), __value, chars_format::general, __precision); 392 393 char* __first = __integral + 1; 394 if (__first == __result.__last) { 395 __result.__radix_point = __result.__last; 396 __result.__exponent = __result.__last; 397 } else { 398 __result.__exponent = __formatter::__find_exponent(__first, __result.__last); 399 if (__result.__exponent != __result.__last) 400 // In scientific mode if there's a radix point it will always be after 401 // the first digit. (This is the position __first points at). 402 __result.__radix_point = *__first == '.' ? __first : __result.__last; 403 else { 404 // In fixed mode the algorithm truncates trailing spaces and possibly the 405 // radix point. There's no good guess for the position of the radix point 406 // therefore scan the output after the first digit. 407 __result.__radix_point = _VSTD::find(__first, __result.__last, '.'); 408 } 409 } 410 411 // clang-format off 412 _LIBCPP_ASSERT((__result.__integral != __result.__last) && 413 (__result.__radix_point == __result.__last || *__result.__radix_point == '.') && 414 (__result.__exponent == __result.__last || *__result.__exponent == 'e'), 415 "Post-condition failure."); 416 // clang-format on 417 418 return __result; 419 } 420 421 template <class _Fp, class _Tp> 422 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer_general_upper_case(__float_buffer<_Fp>& __buffer, _Tp __value, 423 int __precision, char* __integral) { 424 __float_result __result = __formatter::__format_buffer_general_lower_case(__buffer, __value, __precision, __integral); 425 if (__result.__exponent != __result.__last) 426 *__result.__exponent = 'E'; 427 return __result; 428 } 429 430 /// Fills the buffer with the data based on the requested formatting. 431 /// 432 /// This function, when needed, turns the characters to upper case and 433 /// determines the "interesting" locations which are returned to the caller. 434 /// 435 /// This means the caller never has to convert the contents of the buffer to 436 /// upper case or search for radix points and the location of the exponent. 437 /// This gives a bit of overhead. The original code didn't do that, but due 438 /// to the number of possible additional work needed to turn this number to 439 /// the proper output the code was littered with tests for upper cases and 440 /// searches for radix points and exponents. 441 /// - When a precision larger than the type's precision is selected 442 /// additional zero characters need to be written before the exponent. 443 /// - alternate form needs to add a radix point when not present. 444 /// - localization needs to do grouping in the integral part. 445 template <class _Fp, class _Tp> 446 // TODO FMT _Fp should just be _Tp when to_chars has proper long double support. 447 _LIBCPP_HIDE_FROM_ABI __float_result __format_buffer( 448 __float_buffer<_Fp>& __buffer, 449 _Tp __value, 450 bool __negative, 451 bool __has_precision, 452 __format_spec::__sign __sign, 453 __format_spec::__type __type) { 454 char* __first = __formatter::__insert_sign(__buffer.begin(), __negative, __sign); 455 switch (__type) { 456 case __format_spec::__type::__default: 457 return __formatter::__format_buffer_default(__buffer, __value, __first); 458 459 case __format_spec::__type::__hexfloat_lower_case: 460 return __formatter::__format_buffer_hexadecimal_lower_case( 461 __buffer, __value, __has_precision ? __buffer.__precision() : -1, __first); 462 463 case __format_spec::__type::__hexfloat_upper_case: 464 return __formatter::__format_buffer_hexadecimal_upper_case( 465 __buffer, __value, __has_precision ? __buffer.__precision() : -1, __first); 466 467 case __format_spec::__type::__scientific_lower_case: 468 return __formatter::__format_buffer_scientific_lower_case(__buffer, __value, __buffer.__precision(), __first); 469 470 case __format_spec::__type::__scientific_upper_case: 471 return __formatter::__format_buffer_scientific_upper_case(__buffer, __value, __buffer.__precision(), __first); 472 473 case __format_spec::__type::__fixed_lower_case: 474 case __format_spec::__type::__fixed_upper_case: 475 return __formatter::__format_buffer_fixed(__buffer, __value, __buffer.__precision(), __first); 476 477 case __format_spec::__type::__general_lower_case: 478 return __formatter::__format_buffer_general_lower_case(__buffer, __value, __buffer.__precision(), __first); 479 480 case __format_spec::__type::__general_upper_case: 481 return __formatter::__format_buffer_general_upper_case(__buffer, __value, __buffer.__precision(), __first); 482 483 default: 484 _LIBCPP_ASSERT(false, "The parser should have validated the type"); 485 __libcpp_unreachable(); 486 } 487 } 488 489 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 490 template <class _OutIt, class _Fp, class _CharT> 491 _LIBCPP_HIDE_FROM_ABI _OutIt __format_locale_specific_form( 492 _OutIt __out_it, 493 const __float_buffer<_Fp>& __buffer, 494 const __float_result& __result, 495 _VSTD::locale __loc, 496 __format_spec::__parsed_specifications<_CharT> __specs) { 497 const auto& __np = use_facet<numpunct<_CharT>>(__loc); 498 string __grouping = __np.grouping(); 499 char* __first = __result.__integral; 500 // When no radix point or exponent are present __last will be __result.__last. 501 char* __last = _VSTD::min(__result.__radix_point, __result.__exponent); 502 503 ptrdiff_t __digits = __last - __first; 504 if (!__grouping.empty()) { 505 if (__digits <= __grouping[0]) 506 __grouping.clear(); 507 else 508 __grouping = __formatter::__determine_grouping(__digits, __grouping); 509 } 510 511 ptrdiff_t __size = 512 __result.__last - __buffer.begin() + // Formatted string 513 __buffer.__num_trailing_zeros() + // Not yet rendered zeros 514 __grouping.size() - // Grouping contains one 515 !__grouping.empty(); // additional character 516 517 __formatter::__padding_size_result __padding = {0, 0}; 518 bool __zero_padding = __specs.__alignment_ == __format_spec::__alignment::__zero_padding; 519 if (__size < __specs.__width_) { 520 if (__zero_padding) { 521 __specs.__alignment_ = __format_spec::__alignment::__right; 522 __specs.__fill_ = _CharT('0'); 523 } 524 525 __padding = __formatter::__padding_size(__size, __specs.__width_, __specs.__alignment_); 526 } 527 528 // sign and (zero padding or alignment) 529 if (__zero_padding && __first != __buffer.begin()) 530 *__out_it++ = *__buffer.begin(); 531 __out_it = _VSTD::fill_n(_VSTD::move(__out_it), __padding.__before_, __specs.__fill_); 532 if (!__zero_padding && __first != __buffer.begin()) 533 *__out_it++ = *__buffer.begin(); 534 535 // integral part 536 if (__grouping.empty()) { 537 __out_it = _VSTD::copy_n(__first, __digits, _VSTD::move(__out_it)); 538 } else { 539 auto __r = __grouping.rbegin(); 540 auto __e = __grouping.rend() - 1; 541 _CharT __sep = __np.thousands_sep(); 542 // The output is divided in small groups of numbers to write: 543 // - A group before the first separator. 544 // - A separator and a group, repeated for the number of separators. 545 // - A group after the last separator. 546 // This loop achieves that process by testing the termination condition 547 // midway in the loop. 548 while (true) { 549 __out_it = _VSTD::copy_n(__first, *__r, _VSTD::move(__out_it)); 550 __first += *__r; 551 552 if (__r == __e) 553 break; 554 555 ++__r; 556 *__out_it++ = __sep; 557 } 558 } 559 560 // fractional part 561 if (__result.__radix_point != __result.__last) { 562 *__out_it++ = __np.decimal_point(); 563 __out_it = _VSTD::copy(__result.__radix_point + 1, __result.__exponent, _VSTD::move(__out_it)); 564 __out_it = _VSTD::fill_n(_VSTD::move(__out_it), __buffer.__num_trailing_zeros(), _CharT('0')); 565 } 566 567 // exponent 568 if (__result.__exponent != __result.__last) 569 __out_it = _VSTD::copy(__result.__exponent, __result.__last, _VSTD::move(__out_it)); 570 571 // alignment 572 return _VSTD::fill_n(_VSTD::move(__out_it), __padding.__after_, __specs.__fill_); 573 } 574 # endif // _LIBCPP_HAS_NO_LOCALIZATION 575 576 template <class _OutIt, class _CharT> 577 _LIBCPP_HIDE_FROM_ABI _OutIt __format_floating_point_non_finite( 578 _OutIt __out_it, __format_spec::__parsed_specifications<_CharT> __specs, bool __negative, bool __isnan) { 579 char __buffer[4]; 580 char* __last = __formatter::__insert_sign(__buffer, __negative, __specs.__std_.__sign_); 581 582 // to_chars can return inf, infinity, nan, and nan(n-char-sequence). 583 // The format library requires inf and nan. 584 // All in one expression to avoid dangling references. 585 bool __upper_case = 586 __specs.__std_.__type_ == __format_spec::__type::__hexfloat_upper_case || 587 __specs.__std_.__type_ == __format_spec::__type::__scientific_upper_case || 588 __specs.__std_.__type_ == __format_spec::__type::__fixed_upper_case || 589 __specs.__std_.__type_ == __format_spec::__type::__general_upper_case; 590 __last = _VSTD::copy_n(&("infnanINFNAN"[6 * __upper_case + 3 * __isnan]), 3, __last); 591 592 // [format.string.std]/13 593 // A zero (0) character preceding the width field pads the field with 594 // leading zeros (following any indication of sign or base) to the field 595 // width, except when applied to an infinity or NaN. 596 if (__specs.__alignment_ == __format_spec::__alignment::__zero_padding) 597 __specs.__alignment_ = __format_spec::__alignment::__right; 598 599 return __formatter::__write(__buffer, __last, _VSTD::move(__out_it), __specs); 600 } 601 602 template <floating_point _Tp, class _CharT> 603 _LIBCPP_HIDE_FROM_ABI auto 604 __format_floating_point(_Tp __value, auto& __ctx, __format_spec::__parsed_specifications<_CharT> __specs) 605 -> decltype(__ctx.out()) { 606 bool __negative = _VSTD::signbit(__value); 607 608 if (!_VSTD::isfinite(__value)) [[unlikely]] 609 return __formatter::__format_floating_point_non_finite(__ctx.out(), __specs, __negative, _VSTD::isnan(__value)); 610 611 // Depending on the std-format-spec string the sign and the value 612 // might not be outputted together: 613 // - zero-padding may insert additional '0' characters. 614 // Therefore the value is processed as a non negative value. 615 // The function @ref __insert_sign will insert a '-' when the value was 616 // negative. 617 618 if (__negative) 619 __value = -__value; 620 621 // TODO FMT _Fp should just be _Tp when to_chars has proper long double support. 622 using _Fp = conditional_t<same_as<_Tp, long double>, double, _Tp>; 623 // Force the type of the precision to avoid -1 to become an unsigned value. 624 __float_buffer<_Fp> __buffer(__specs.__precision_); 625 __float_result __result = __formatter::__format_buffer( 626 __buffer, __value, __negative, (__specs.__has_precision()), __specs.__std_.__sign_, __specs.__std_.__type_); 627 628 if (__specs.__std_.__alternate_form_ && __result.__radix_point == __result.__last) { 629 *__result.__last++ = '.'; 630 631 // When there is an exponent the point needs to be moved before the 632 // exponent. When there's no exponent the rotate does nothing. Since 633 // rotate tests whether the operation is a nop, call it unconditionally. 634 _VSTD::rotate(__result.__exponent, __result.__last - 1, __result.__last); 635 __result.__radix_point = __result.__exponent; 636 637 // The radix point is always placed before the exponent. 638 // - No exponent needs to point to the new last. 639 // - An exponent needs to move one position to the right. 640 // So it's safe to increment the value unconditionally. 641 ++__result.__exponent; 642 } 643 644 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 645 if (__specs.__std_.__locale_specific_form_) 646 return __formatter::__format_locale_specific_form(__ctx.out(), __buffer, __result, __ctx.locale(), __specs); 647 # endif 648 649 ptrdiff_t __size = __result.__last - __buffer.begin(); 650 int __num_trailing_zeros = __buffer.__num_trailing_zeros(); 651 if (__size + __num_trailing_zeros >= __specs.__width_) { 652 if (__num_trailing_zeros && __result.__exponent != __result.__last) 653 // Insert trailing zeros before exponent character. 654 return _VSTD::copy( 655 __result.__exponent, 656 __result.__last, 657 _VSTD::fill_n( 658 _VSTD::copy(__buffer.begin(), __result.__exponent, __ctx.out()), __num_trailing_zeros, _CharT('0'))); 659 660 return _VSTD::fill_n( 661 _VSTD::copy(__buffer.begin(), __result.__last, __ctx.out()), __num_trailing_zeros, _CharT('0')); 662 } 663 664 auto __out_it = __ctx.out(); 665 char* __first = __buffer.begin(); 666 if (__specs.__alignment_ == __format_spec::__alignment ::__zero_padding) { 667 // When there is a sign output it before the padding. Note the __size 668 // doesn't need any adjustment, regardless whether the sign is written 669 // here or in __formatter::__write. 670 if (__first != __result.__integral) 671 *__out_it++ = *__first++; 672 // After the sign is written, zero padding is the same a right alignment 673 // with '0'. 674 __specs.__alignment_ = __format_spec::__alignment::__right; 675 __specs.__fill_ = _CharT('0'); 676 } 677 678 if (__num_trailing_zeros) 679 return __formatter::__write_using_trailing_zeros( 680 __first, __result.__last, _VSTD::move(__out_it), __specs, __size, __result.__exponent, __num_trailing_zeros); 681 682 return __formatter::__write(__first, __result.__last, _VSTD::move(__out_it), __specs, __size); 683 } 684 685 } // namespace __formatter 686 687 template <__formatter::__char_type _CharT> 688 struct _LIBCPP_TEMPLATE_VIS __formatter_floating_point { 689 public: 690 _LIBCPP_HIDE_FROM_ABI constexpr auto 691 parse(basic_format_parse_context<_CharT>& __parse_ctx) -> decltype(__parse_ctx.begin()) { 692 auto __result = __parser_.__parse(__parse_ctx, __format_spec::__fields_floating_point); 693 __format_spec::__process_parsed_floating_point(__parser_); 694 return __result; 695 } 696 697 template <floating_point _Tp> 698 _LIBCPP_HIDE_FROM_ABI auto format(_Tp __value, auto& __ctx) const -> decltype(__ctx.out()) { 699 return __formatter::__format_floating_point(__value, __ctx, __parser_.__get_parsed_std_specifications(__ctx)); 700 } 701 702 __format_spec::__parser<_CharT> __parser_; 703 }; 704 705 template <__formatter::__char_type _CharT> 706 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<float, _CharT> 707 : public __formatter_floating_point<_CharT> {}; 708 template <__formatter::__char_type _CharT> 709 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<double, _CharT> 710 : public __formatter_floating_point<_CharT> {}; 711 template <__formatter::__char_type _CharT> 712 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT formatter<long double, _CharT> 713 : public __formatter_floating_point<_CharT> {}; 714 715 #endif //_LIBCPP_STD_VER > 17 716 717 _LIBCPP_END_NAMESPACE_STD 718 719 _LIBCPP_POP_MACROS 720 721 #endif // _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H 722