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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-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 <__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_LOCALIZATION
43# include <__locale>
44#endif
45
46#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
47# pragma GCC system_header
48#endif
49
50_LIBCPP_PUSH_MACROS
51#include <__undef_macros>
52
53_LIBCPP_BEGIN_NAMESPACE_STD
54
55#if _LIBCPP_STD_VER >= 20
56
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-1
81// float min subnormal: +/-0x1p-149 max: +/- 3.402,823,4 10^38
82// double min subnormal: +/-0x1p-1074 max +/- 1.797,693,134,862,315,7 10^308
83// long double (x86) min subnormal: +/-0x1p-16446 max: +/- 1.189,731,495,357,231,765,021 10^4932
84//
85// The maximum number of digits required for the integral part is based on the
86// maximum's value power of 10. Every power of 10 requires one additional
87// decimal digit.
88// The maximum number of digits required for the fractional part is based on
89// the minimal subnormal hexadecimal output's power of 10. Every division of a
90// 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 the
94// values maximum required, these values are:
95//
96// sign 1 code unit
97// __max_integral
98// radix point 1 code unit
99// __max_fractional
100// exponent character 1 code unit
101// sign 1 code unit
102// __max_fractional_value
103// -----------------------------------
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 allocated
142/// 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 buffer
150 // will always suffice. At the moment that isn't important since floats and
151 // doubles use a stack buffer, unless the precision used in the format string
152 // is large.
153 // When supporting long doubles the __max_integral part becomes 4932 which
154 // may be too much for some platforms. For these cases a better estimate is
155 // 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 in
159 // the range (_Traits::__max_fractional, precision] will contain the value
160 // 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 needs
166 // 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 else
177 __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 with
222/// 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_result
239__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 of
252 // __result.__last.
253 if (__result.__radix_point == __result.__exponent)
254 __result.__radix_point = __result.__last;
255
256 // clang-format off
257 _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 on
262
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 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 = std::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_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 on
314
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 off
347 _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 on
352 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_result
366__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 done
374 // unconditionally.
375 __result.__radix_point = __result.__last - (__precision + bool(__precision));
376 __result.__exponent = __result.__last;
377
378 // clang-format off
379 _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 on
384 return __result;
385}
386
387template <class _Fp, class _Tp>
388_LIBCPP_HIDE_FROM_ABI __float_result
389__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 after
404 // 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 the
408 // radix point. There's no good guess for the position of the radix point
409 // therefore scan the output after the first digit.
410 __result.__radix_point = std::find(__first, __result.__last, '.');
411 }
412 }
413
414 // clang-format off
415 _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 on
420
421 return __result;
422}
423
424template <class _Fp, class _Tp>
425_LIBCPP_HIDE_FROM_ABI __float_result
426__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 and
436/// 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 to
439/// 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 due
441/// to the number of possible additional work needed to turn this number to
442/// the proper output the code was littered with tests for upper cases and
443/// searches for radix points and exponents.
444/// - When a precision larger than the type's precision is selected
445/// 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 else
463 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_LOCALIZATION
496template <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 else
514 __grouping = __formatter::__determine_grouping(__digits, __grouping);
515 }
516
517 ptrdiff_t __size =
518 __result.__last - __buffer.begin() + // Formatted string
519 __buffer.__num_trailing_zeros() + // Not yet rendered zeros
520 __grouping.size() - // Grouping contains one
521 !__grouping.empty(); // additional character
522
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 part
542 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 condition
553 // 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 part
567 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 // exponent
574 if (__result.__exponent != __result.__last)
575 __out_it = __formatter::__copy(__result.__exponent, __result.__last, std::move(__out_it));
576
577 // alignment
578 return __formatter::__fill(std::move(__out_it), __padding.__after_, __specs.__fill_);
579}
580# endif // _LIBCPP_HAS_LOCALIZATION
581
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]/13
599 // A zero (0) character preceding the width field pads the field with
600 // leading zeros (following any indication of sign or base) to the field
601 // 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 larger
610/// than the maximum precision of the floating-point type. These precision
611/// 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 exponent
615/// 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::iterator
639__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 value
646 // 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 was
650 // 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 the
667 // exponent. When there's no exponent the rotate does nothing. Since
668 // 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]/6
680 // In addition, for g and G conversions, trailing zeros are not removed
681 // from the result.
682 //
683 // If the type option for a floating-point type is none it may use the
684 // general formatting, but it's not a g or G conversion. So in that case
685 // 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/fprintf
691 // Let P equal the precision if nonzero, 6 if the precision is not
692 // specified, or 1 if the precision is 0. Then, if a conversion with
693 // 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 else
700 // 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_LOCALIZATION
710 if (__specs.__std_.__locale_specific_form_)
711 return __formatter::__format_locale_specific_form(__ctx.out(), __buffer, __result, __ctx.locale(), __specs);
712# endif
713
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 __size
734 // doesn't need any adjustment, regardless whether the sign is written
735 // 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 alignment
739 // 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 __formatter
752
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 >= 23
779template <>
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 >= 23
786#endif // _LIBCPP_STD_VER >= 20
787
788_LIBCPP_END_NAMESPACE_STD
789
790_LIBCPP_POP_MACROS
791
792#endif // _LIBCPP___FORMAT_FORMATTER_FLOATING_POINT_H
793

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source code of libcxx/include/__format/formatter_floating_point.h