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1 // Formatting library for C++ - the core API
2 //
3 // Copyright (c) 2012 - present, Victor Zverovich
4 // All rights reserved.
5 //
6 // For the license information refer to format.h.
7 
8 #ifndef FMT_CORE_H_
9 #define FMT_CORE_H_
10 
11 #include <cstdio>  // std::FILE
12 #include <cstring>
13 #include <iterator>
14 #include <string>
15 #include <type_traits>
16 
17 // The fmt library version in the form major * 10000 + minor * 100 + patch.
18 #define FMT_VERSION 60101
19 
20 #ifdef __has_feature
21 #  define FMT_HAS_FEATURE(x) __has_feature(x)
22 #else
23 #  define FMT_HAS_FEATURE(x) 0
24 #endif
25 
26 #if defined(__has_include) && !defined(__INTELLISENSE__) && \
27     !(defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1600)
28 #  define FMT_HAS_INCLUDE(x) __has_include(x)
29 #else
30 #  define FMT_HAS_INCLUDE(x) 0
31 #endif
32 
33 #ifdef __has_cpp_attribute
34 #  define FMT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
35 #else
36 #  define FMT_HAS_CPP_ATTRIBUTE(x) 0
37 #endif
38 
39 #if defined(__GNUC__) && !defined(__clang__)
40 #  define FMT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
41 #else
42 #  define FMT_GCC_VERSION 0
43 #endif
44 
45 #if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
46 #  define FMT_HAS_GXX_CXX11 FMT_GCC_VERSION
47 #else
48 #  define FMT_HAS_GXX_CXX11 0
49 #endif
50 
51 #ifdef __NVCC__
52 #  define FMT_NVCC __NVCC__
53 #else
54 #  define FMT_NVCC 0
55 #endif
56 
57 #ifdef _MSC_VER
58 #  define FMT_MSC_VER _MSC_VER
59 #else
60 #  define FMT_MSC_VER 0
61 #endif
62 
63 // Check if relaxed C++14 constexpr is supported.
64 // GCC doesn't allow throw in constexpr until version 6 (bug 67371).
65 #ifndef FMT_USE_CONSTEXPR
66 #  define FMT_USE_CONSTEXPR                                           \
67     (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1910 || \
68      (FMT_GCC_VERSION >= 600 && __cplusplus >= 201402L)) &&           \
69         !FMT_NVCC
70 #endif
71 #if FMT_USE_CONSTEXPR
72 #  define FMT_CONSTEXPR constexpr
73 #  define FMT_CONSTEXPR_DECL constexpr
74 #else
75 #  define FMT_CONSTEXPR inline
76 #  define FMT_CONSTEXPR_DECL
77 #endif
78 
79 #ifndef FMT_OVERRIDE
80 #  if FMT_HAS_FEATURE(cxx_override) || \
81       (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
82 #    define FMT_OVERRIDE override
83 #  else
84 #    define FMT_OVERRIDE
85 #  endif
86 #endif
87 
88 // Check if exceptions are disabled.
89 #ifndef FMT_EXCEPTIONS
90 #  if (defined(__GNUC__) && !defined(__EXCEPTIONS)) || \
91       FMT_MSC_VER && !_HAS_EXCEPTIONS
92 #    define FMT_EXCEPTIONS 0
93 #  else
94 #    define FMT_EXCEPTIONS 1
95 #  endif
96 #endif
97 
98 // Define FMT_USE_NOEXCEPT to make fmt use noexcept (C++11 feature).
99 #ifndef FMT_USE_NOEXCEPT
100 #  define FMT_USE_NOEXCEPT 0
101 #endif
102 
103 #if FMT_USE_NOEXCEPT || FMT_HAS_FEATURE(cxx_noexcept) || \
104     (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
105 #  define FMT_DETECTED_NOEXCEPT noexcept
106 #  define FMT_HAS_CXX11_NOEXCEPT 1
107 #else
108 #  define FMT_DETECTED_NOEXCEPT throw()
109 #  define FMT_HAS_CXX11_NOEXCEPT 0
110 #endif
111 
112 #ifndef FMT_NOEXCEPT
113 #  if FMT_EXCEPTIONS || FMT_HAS_CXX11_NOEXCEPT
114 #    define FMT_NOEXCEPT FMT_DETECTED_NOEXCEPT
115 #  else
116 #    define FMT_NOEXCEPT
117 #  endif
118 #endif
119 
120 // [[noreturn]] is disabled on MSVC because of bogus unreachable code warnings.
121 #if FMT_EXCEPTIONS && FMT_HAS_CPP_ATTRIBUTE(noreturn) && !FMT_MSC_VER
122 #  define FMT_NORETURN [[noreturn]]
123 #else
124 #  define FMT_NORETURN
125 #endif
126 
127 #ifndef FMT_DEPRECATED
128 #  if (FMT_HAS_CPP_ATTRIBUTE(deprecated) && __cplusplus >= 201402L) || \
129       FMT_MSC_VER >= 1900
130 #    define FMT_DEPRECATED [[deprecated]]
131 #  else
132 #    if defined(__GNUC__) || defined(__clang__)
133 #      define FMT_DEPRECATED __attribute__((deprecated))
134 #    elif FMT_MSC_VER
135 #      define FMT_DEPRECATED __declspec(deprecated)
136 #    else
137 #      define FMT_DEPRECATED /* deprecated */
138 #    endif
139 #  endif
140 #endif
141 
142 // Workaround broken [[deprecated]] in the Intel compiler and NVCC.
143 #if defined(__INTEL_COMPILER) || FMT_NVCC
144 #  define FMT_DEPRECATED_ALIAS
145 #else
146 #  define FMT_DEPRECATED_ALIAS FMT_DEPRECATED
147 #endif
148 
149 #ifndef FMT_BEGIN_NAMESPACE
150 #  if FMT_HAS_FEATURE(cxx_inline_namespaces) || FMT_GCC_VERSION >= 404 || \
151       FMT_MSC_VER >= 1900
152 #    define FMT_INLINE_NAMESPACE inline namespace
153 #    define FMT_END_NAMESPACE \
154       }                       \
155       }
156 #  else
157 #    define FMT_INLINE_NAMESPACE namespace
158 #    define FMT_END_NAMESPACE \
159       }                       \
160       using namespace v6;     \
161       }
162 #  endif
163 #  define FMT_BEGIN_NAMESPACE \
164     namespace fmt {           \
165     FMT_INLINE_NAMESPACE v6 {
166 #endif
167 
168 #if !defined(FMT_HEADER_ONLY) && defined(_WIN32)
169 #  ifdef FMT_EXPORT
170 #    define FMT_API __declspec(dllexport)
171 #  elif defined(FMT_SHARED)
172 #    define FMT_API __declspec(dllimport)
173 #    define FMT_EXTERN_TEMPLATE_API FMT_API
174 #  endif
175 #endif
176 #ifndef FMT_API
177 #  define FMT_API
178 #endif
179 #ifndef FMT_EXTERN_TEMPLATE_API
180 #  define FMT_EXTERN_TEMPLATE_API
181 #endif
182 
183 #ifndef FMT_HEADER_ONLY
184 #  define FMT_EXTERN extern
185 #else
186 #  define FMT_EXTERN
187 #endif
188 
189 // libc++ supports string_view in pre-c++17.
190 #if (FMT_HAS_INCLUDE(<string_view>) &&                       \
191      (__cplusplus > 201402L || defined(_LIBCPP_VERSION))) || \
192     (defined(_MSVC_LANG) && _MSVC_LANG > 201402L && _MSC_VER >= 1910)
193 #  include <string_view>
194 #  define FMT_USE_STRING_VIEW
195 #elif FMT_HAS_INCLUDE("experimental/string_view") && __cplusplus >= 201402L
196 #  include <experimental/string_view>
197 #  define FMT_USE_EXPERIMENTAL_STRING_VIEW
198 #endif
199 
200 FMT_BEGIN_NAMESPACE
201 
202 // Implementations of enable_if_t and other types for pre-C++14 systems.
203 template <bool B, class T = void>
204 using enable_if_t = typename std::enable_if<B, T>::type;
205 template <bool B, class T, class F>
206 using conditional_t = typename std::conditional<B, T, F>::type;
207 template <bool B> using bool_constant = std::integral_constant<bool, B>;
208 template <typename T>
209 using remove_reference_t = typename std::remove_reference<T>::type;
210 template <typename T>
211 using remove_const_t = typename std::remove_const<T>::type;
212 template <typename T>
213 using remove_cvref_t = typename std::remove_cv<remove_reference_t<T>>::type;
214 
215 struct monostate {};
216 
217 // An enable_if helper to be used in template parameters which results in much
218 // shorter symbols: https://godbolt.org/z/sWw4vP. Extra parentheses are needed
219 // to workaround a bug in MSVC 2019 (see #1140 and #1186).
220 #define FMT_ENABLE_IF(...) enable_if_t<(__VA_ARGS__), int> = 0
221 
222 namespace internal {
223 
224 // A workaround for gcc 4.8 to make void_t work in a SFINAE context.
225 template <typename... Ts> struct void_t_impl { using type = void; };
226 
227 FMT_API void assert_fail(const char* file, int line, const char* message);
228 
229 #ifndef FMT_ASSERT
230 #  ifdef NDEBUG
231 #    define FMT_ASSERT(condition, message)
232 #  else
233 #    define FMT_ASSERT(condition, message) \
234       ((condition)                         \
235            ? void()                        \
236            : fmt::internal::assert_fail(__FILE__, __LINE__, (message)))
237 #  endif
238 #endif
239 
240 #if defined(FMT_USE_STRING_VIEW)
241 template <typename Char> using std_string_view = std::basic_string_view<Char>;
242 #elif defined(FMT_USE_EXPERIMENTAL_STRING_VIEW)
243 template <typename Char>
244 using std_string_view = std::experimental::basic_string_view<Char>;
245 #else
246 template <typename T> struct std_string_view {};
247 #endif
248 
249 #ifdef FMT_USE_INT128
250 // Do nothing.
251 #elif defined(__SIZEOF_INT128__)
252 #  define FMT_USE_INT128 1
253 using int128_t = __int128_t;
254 using uint128_t = __uint128_t;
255 #else
256 #  define FMT_USE_INT128 0
257 #endif
258 #if !FMT_USE_INT128
259 struct int128_t {};
260 struct uint128_t {};
261 #endif
262 
263 // Casts a nonnegative integer to unsigned.
264 template <typename Int>
to_unsigned(Int value)265 FMT_CONSTEXPR typename std::make_unsigned<Int>::type to_unsigned(Int value) {
266   FMT_ASSERT(value >= 0, "negative value");
267   return static_cast<typename std::make_unsigned<Int>::type>(value);
268 }
269 }  // namespace internal
270 
271 template <typename... Ts>
272 using void_t = typename internal::void_t_impl<Ts...>::type;
273 
274 /**
275   An implementation of ``std::basic_string_view`` for pre-C++17. It provides a
276   subset of the API. ``fmt::basic_string_view`` is used for format strings even
277   if ``std::string_view`` is available to prevent issues when a library is
278   compiled with a different ``-std`` option than the client code (which is not
279   recommended).
280  */
281 template <typename Char> class basic_string_view {
282  private:
283   const Char* data_;
284   size_t size_;
285 
286  public:
287   using char_type = Char;
288   using iterator = const Char*;
289 
basic_string_view()290   FMT_CONSTEXPR basic_string_view() FMT_NOEXCEPT : data_(nullptr), size_(0) {}
291 
292   /** Constructs a string reference object from a C string and a size. */
basic_string_view(const Char * s,size_t count)293   FMT_CONSTEXPR basic_string_view(const Char* s, size_t count) FMT_NOEXCEPT
294       : data_(s),
295         size_(count) {}
296 
297   /**
298     \rst
299     Constructs a string reference object from a C string computing
300     the size with ``std::char_traits<Char>::length``.
301     \endrst
302    */
basic_string_view(const Char * s)303   basic_string_view(const Char* s)
304       : data_(s), size_(std::char_traits<Char>::length(s)) {}
305 
306   /** Constructs a string reference from a ``std::basic_string`` object. */
307   template <typename Traits, typename Alloc>
basic_string_view(const std::basic_string<Char,Traits,Alloc> & s)308   FMT_CONSTEXPR basic_string_view(
309       const std::basic_string<Char, Traits, Alloc>& s) FMT_NOEXCEPT
310       : data_(s.data()),
311         size_(s.size()) {}
312 
313   template <
314       typename S,
315       FMT_ENABLE_IF(std::is_same<S, internal::std_string_view<Char>>::value)>
basic_string_view(S s)316   FMT_CONSTEXPR basic_string_view(S s) FMT_NOEXCEPT : data_(s.data()),
317                                                       size_(s.size()) {}
318 
319   /** Returns a pointer to the string data. */
data()320   FMT_CONSTEXPR const Char* data() const { return data_; }
321 
322   /** Returns the string size. */
size()323   FMT_CONSTEXPR size_t size() const { return size_; }
324 
begin()325   FMT_CONSTEXPR iterator begin() const { return data_; }
end()326   FMT_CONSTEXPR iterator end() const { return data_ + size_; }
327 
328   FMT_CONSTEXPR const Char& operator[](size_t pos) const { return data_[pos]; }
329 
remove_prefix(size_t n)330   FMT_CONSTEXPR void remove_prefix(size_t n) {
331     data_ += n;
332     size_ -= n;
333   }
334 
335   // Lexicographically compare this string reference to other.
compare(basic_string_view other)336   int compare(basic_string_view other) const {
337     size_t str_size = size_ < other.size_ ? size_ : other.size_;
338     int result = std::char_traits<Char>::compare(data_, other.data_, str_size);
339     if (result == 0)
340       result = size_ == other.size_ ? 0 : (size_ < other.size_ ? -1 : 1);
341     return result;
342   }
343 
344   friend bool operator==(basic_string_view lhs, basic_string_view rhs) {
345     return lhs.compare(rhs) == 0;
346   }
347   friend bool operator!=(basic_string_view lhs, basic_string_view rhs) {
348     return lhs.compare(rhs) != 0;
349   }
350   friend bool operator<(basic_string_view lhs, basic_string_view rhs) {
351     return lhs.compare(rhs) < 0;
352   }
353   friend bool operator<=(basic_string_view lhs, basic_string_view rhs) {
354     return lhs.compare(rhs) <= 0;
355   }
356   friend bool operator>(basic_string_view lhs, basic_string_view rhs) {
357     return lhs.compare(rhs) > 0;
358   }
359   friend bool operator>=(basic_string_view lhs, basic_string_view rhs) {
360     return lhs.compare(rhs) >= 0;
361   }
362 };
363 
364 using string_view = basic_string_view<char>;
365 using wstring_view = basic_string_view<wchar_t>;
366 
367 #ifndef __cpp_char8_t
368 // A UTF-8 code unit type.
369 enum char8_t : unsigned char {};
370 #endif
371 
372 /** Specifies if ``T`` is a character type. Can be specialized by users. */
373 template <typename T> struct is_char : std::false_type {};
374 template <> struct is_char<char> : std::true_type {};
375 template <> struct is_char<wchar_t> : std::true_type {};
376 template <> struct is_char<char8_t> : std::true_type {};
377 template <> struct is_char<char16_t> : std::true_type {};
378 template <> struct is_char<char32_t> : std::true_type {};
379 
380 /**
381   \rst
382   Returns a string view of `s`. In order to add custom string type support to
383   {fmt} provide an overload of `to_string_view` for it in the same namespace as
384   the type for the argument-dependent lookup to work.
385 
386   **Example**::
387 
388     namespace my_ns {
389     inline string_view to_string_view(const my_string& s) {
390       return {s.data(), s.length()};
391     }
392     }
393     std::string message = fmt::format(my_string("The answer is {}"), 42);
394   \endrst
395  */
396 template <typename Char, FMT_ENABLE_IF(is_char<Char>::value)>
397 inline basic_string_view<Char> to_string_view(const Char* s) {
398   return s;
399 }
400 
401 template <typename Char, typename Traits, typename Alloc>
402 inline basic_string_view<Char> to_string_view(
403     const std::basic_string<Char, Traits, Alloc>& s) {
404   return s;
405 }
406 
407 template <typename Char>
408 inline basic_string_view<Char> to_string_view(basic_string_view<Char> s) {
409   return s;
410 }
411 
412 template <typename Char,
413           FMT_ENABLE_IF(!std::is_empty<internal::std_string_view<Char>>::value)>
414 inline basic_string_view<Char> to_string_view(
415     internal::std_string_view<Char> s) {
416   return s;
417 }
418 
419 // A base class for compile-time strings. It is defined in the fmt namespace to
420 // make formatting functions visible via ADL, e.g. format(fmt("{}"), 42).
421 struct compile_string {};
422 
423 template <typename S>
424 struct is_compile_string : std::is_base_of<compile_string, S> {};
425 
426 template <typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
427 constexpr basic_string_view<typename S::char_type> to_string_view(const S& s) {
428   return s;
429 }
430 
431 namespace internal {
432 void to_string_view(...);
433 using fmt::v6::to_string_view;
434 
435 // Specifies whether S is a string type convertible to fmt::basic_string_view.
436 // It should be a constexpr function but MSVC 2017 fails to compile it in
437 // enable_if and MSVC 2015 fails to compile it as an alias template.
438 template <typename S>
439 struct is_string : std::is_class<decltype(to_string_view(std::declval<S>()))> {
440 };
441 
442 template <typename S, typename = void> struct char_t_impl {};
443 template <typename S> struct char_t_impl<S, enable_if_t<is_string<S>::value>> {
444   using result = decltype(to_string_view(std::declval<S>()));
445   using type = typename result::char_type;
446 };
447 
448 struct error_handler {
449   FMT_CONSTEXPR error_handler() = default;
450   FMT_CONSTEXPR error_handler(const error_handler&) = default;
451 
452   // This function is intentionally not constexpr to give a compile-time error.
453   FMT_NORETURN FMT_API void on_error(const char* message);
454 };
455 }  // namespace internal
456 
457 /** String's character type. */
458 template <typename S> using char_t = typename internal::char_t_impl<S>::type;
459 
460 /**
461   \rst
462   Parsing context consisting of a format string range being parsed and an
463   argument counter for automatic indexing.
464 
465   You can use one of the following type aliases for common character types:
466 
467   +-----------------------+-------------------------------------+
468   | Type                  | Definition                          |
469   +=======================+=====================================+
470   | format_parse_context  | basic_format_parse_context<char>    |
471   +-----------------------+-------------------------------------+
472   | wformat_parse_context | basic_format_parse_context<wchar_t> |
473   +-----------------------+-------------------------------------+
474   \endrst
475  */
476 template <typename Char, typename ErrorHandler = internal::error_handler>
477 class basic_format_parse_context : private ErrorHandler {
478  private:
479   basic_string_view<Char> format_str_;
480   int next_arg_id_;
481 
482  public:
483   using char_type = Char;
484   using iterator = typename basic_string_view<Char>::iterator;
485 
486   explicit FMT_CONSTEXPR basic_format_parse_context(
487       basic_string_view<Char> format_str, ErrorHandler eh = ErrorHandler())
488       : ErrorHandler(eh), format_str_(format_str), next_arg_id_(0) {}
489 
490   /**
491     Returns an iterator to the beginning of the format string range being
492     parsed.
493    */
494   FMT_CONSTEXPR iterator begin() const FMT_NOEXCEPT {
495     return format_str_.begin();
496   }
497 
498   /**
499     Returns an iterator past the end of the format string range being parsed.
500    */
501   FMT_CONSTEXPR iterator end() const FMT_NOEXCEPT { return format_str_.end(); }
502 
503   /** Advances the begin iterator to ``it``. */
504   FMT_CONSTEXPR void advance_to(iterator it) {
505     format_str_.remove_prefix(internal::to_unsigned(it - begin()));
506   }
507 
508   /**
509     Reports an error if using the manual argument indexing; otherwise returns
510     the next argument index and switches to the automatic indexing.
511    */
512   FMT_CONSTEXPR int next_arg_id() {
513     if (next_arg_id_ >= 0) return next_arg_id_++;
514     on_error("cannot switch from manual to automatic argument indexing");
515     return 0;
516   }
517 
518   /**
519     Reports an error if using the automatic argument indexing; otherwise
520     switches to the manual indexing.
521    */
522   FMT_CONSTEXPR void check_arg_id(int) {
523     if (next_arg_id_ > 0)
524       on_error("cannot switch from automatic to manual argument indexing");
525     else
526       next_arg_id_ = -1;
527   }
528 
529   FMT_CONSTEXPR void check_arg_id(basic_string_view<Char>) {}
530 
531   FMT_CONSTEXPR void on_error(const char* message) {
532     ErrorHandler::on_error(message);
533   }
534 
535   FMT_CONSTEXPR ErrorHandler error_handler() const { return *this; }
536 };
537 
538 using format_parse_context = basic_format_parse_context<char>;
539 using wformat_parse_context = basic_format_parse_context<wchar_t>;
540 
541 template <typename Char, typename ErrorHandler = internal::error_handler>
542 using basic_parse_context FMT_DEPRECATED_ALIAS =
543     basic_format_parse_context<Char, ErrorHandler>;
544 using parse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<char>;
545 using wparse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<wchar_t>;
546 
547 template <typename Context> class basic_format_arg;
548 template <typename Context> class basic_format_args;
549 
550 // A formatter for objects of type T.
551 template <typename T, typename Char = char, typename Enable = void>
552 struct formatter {
553   // A deleted default constructor indicates a disabled formatter.
554   formatter() = delete;
555 };
556 
557 template <typename T, typename Char, typename Enable = void>
558 struct FMT_DEPRECATED convert_to_int
559     : bool_constant<!std::is_arithmetic<T>::value &&
560                     std::is_convertible<T, int>::value> {};
561 
562 // Specifies if T has an enabled formatter specialization. A type can be
563 // formattable even if it doesn't have a formatter e.g. via a conversion.
564 template <typename T, typename Context>
565 using has_formatter =
566     std::is_constructible<typename Context::template formatter_type<T>>;
567 
568 namespace internal {
569 
570 /** A contiguous memory buffer with an optional growing ability. */
571 template <typename T> class buffer {
572  private:
573   T* ptr_;
574   std::size_t size_;
575   std::size_t capacity_;
576 
577  protected:
578   // Don't initialize ptr_ since it is not accessed to save a few cycles.
579   buffer(std::size_t sz) FMT_NOEXCEPT : size_(sz), capacity_(sz) {}
580 
581   buffer(T* p = nullptr, std::size_t sz = 0, std::size_t cap = 0) FMT_NOEXCEPT
582       : ptr_(p),
583         size_(sz),
584         capacity_(cap) {}
585 
586   /** Sets the buffer data and capacity. */
587   void set(T* buf_data, std::size_t buf_capacity) FMT_NOEXCEPT {
588     ptr_ = buf_data;
589     capacity_ = buf_capacity;
590   }
591 
592   /** Increases the buffer capacity to hold at least *capacity* elements. */
593   virtual void grow(std::size_t capacity) = 0;
594 
595  public:
596   using value_type = T;
597   using const_reference = const T&;
598 
599   buffer(const buffer&) = delete;
600   void operator=(const buffer&) = delete;
601   virtual ~buffer() = default;
602 
603   T* begin() FMT_NOEXCEPT { return ptr_; }
604   T* end() FMT_NOEXCEPT { return ptr_ + size_; }
605 
606   /** Returns the size of this buffer. */
607   std::size_t size() const FMT_NOEXCEPT { return size_; }
608 
609   /** Returns the capacity of this buffer. */
610   std::size_t capacity() const FMT_NOEXCEPT { return capacity_; }
611 
612   /** Returns a pointer to the buffer data. */
613   T* data() FMT_NOEXCEPT { return ptr_; }
614 
615   /** Returns a pointer to the buffer data. */
616   const T* data() const FMT_NOEXCEPT { return ptr_; }
617 
618   /**
619     Resizes the buffer. If T is a POD type new elements may not be initialized.
620    */
621   void resize(std::size_t new_size) {
622     reserve(new_size);
623     size_ = new_size;
624   }
625 
626   /** Clears this buffer. */
627   void clear() { size_ = 0; }
628 
629   /** Reserves space to store at least *capacity* elements. */
630   void reserve(std::size_t new_capacity) {
631     if (new_capacity > capacity_) grow(new_capacity);
632   }
633 
634   void push_back(const T& value) {
635     reserve(size_ + 1);
636     ptr_[size_++] = value;
637   }
638 
639   /** Appends data to the end of the buffer. */
640   template <typename U> void append(const U* begin, const U* end);
641 
642   T& operator[](std::size_t index) { return ptr_[index]; }
643   const T& operator[](std::size_t index) const { return ptr_[index]; }
644 };
645 
646 // A container-backed buffer.
647 template <typename Container>
648 class container_buffer : public buffer<typename Container::value_type> {
649  private:
650   Container& container_;
651 
652  protected:
653   void grow(std::size_t capacity) FMT_OVERRIDE {
654     container_.resize(capacity);
655     this->set(&container_[0], capacity);
656   }
657 
658  public:
659   explicit container_buffer(Container& c)
660       : buffer<typename Container::value_type>(c.size()), container_(c) {}
661 };
662 
663 // Extracts a reference to the container from back_insert_iterator.
664 template <typename Container>
665 inline Container& get_container(std::back_insert_iterator<Container> it) {
666   using bi_iterator = std::back_insert_iterator<Container>;
667   struct accessor : bi_iterator {
668     accessor(bi_iterator iter) : bi_iterator(iter) {}
669     using bi_iterator::container;
670   };
671   return *accessor(it).container;
672 }
673 
674 template <typename T, typename Char = char, typename Enable = void>
675 struct fallback_formatter {
676   fallback_formatter() = delete;
677 };
678 
679 // Specifies if T has an enabled fallback_formatter specialization.
680 template <typename T, typename Context>
681 using has_fallback_formatter =
682     std::is_constructible<fallback_formatter<T, typename Context::char_type>>;
683 
684 template <typename Char> struct named_arg_base;
685 template <typename T, typename Char> struct named_arg;
686 
687 enum type {
688   none_type,
689   named_arg_type,
690   // Integer types should go first,
691   int_type,
692   uint_type,
693   long_long_type,
694   ulong_long_type,
695   int128_type,
696   uint128_type,
697   bool_type,
698   char_type,
699   last_integer_type = char_type,
700   // followed by floating-point types.
701   float_type,
702   double_type,
703   long_double_type,
704   last_numeric_type = long_double_type,
705   cstring_type,
706   string_type,
707   pointer_type,
708   custom_type
709 };
710 
711 // Maps core type T to the corresponding type enum constant.
712 template <typename T, typename Char>
713 struct type_constant : std::integral_constant<type, custom_type> {};
714 
715 #define FMT_TYPE_CONSTANT(Type, constant) \
716   template <typename Char>                \
717   struct type_constant<Type, Char> : std::integral_constant<type, constant> {}
718 
719 FMT_TYPE_CONSTANT(const named_arg_base<Char>&, named_arg_type);
720 FMT_TYPE_CONSTANT(int, int_type);
721 FMT_TYPE_CONSTANT(unsigned, uint_type);
722 FMT_TYPE_CONSTANT(long long, long_long_type);
723 FMT_TYPE_CONSTANT(unsigned long long, ulong_long_type);
724 FMT_TYPE_CONSTANT(int128_t, int128_type);
725 FMT_TYPE_CONSTANT(uint128_t, uint128_type);
726 FMT_TYPE_CONSTANT(bool, bool_type);
727 FMT_TYPE_CONSTANT(Char, char_type);
728 FMT_TYPE_CONSTANT(float, float_type);
729 FMT_TYPE_CONSTANT(double, double_type);
730 FMT_TYPE_CONSTANT(long double, long_double_type);
731 FMT_TYPE_CONSTANT(const Char*, cstring_type);
732 FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
733 FMT_TYPE_CONSTANT(const void*, pointer_type);
734 
735 FMT_CONSTEXPR bool is_integral_type(type t) {
736   FMT_ASSERT(t != named_arg_type, "invalid argument type");
737   return t > none_type && t <= last_integer_type;
738 }
739 
740 FMT_CONSTEXPR bool is_arithmetic_type(type t) {
741   FMT_ASSERT(t != named_arg_type, "invalid argument type");
742   return t > none_type && t <= last_numeric_type;
743 }
744 
745 template <typename Char> struct string_value {
746   const Char* data;
747   std::size_t size;
748 };
749 
750 template <typename Context> struct custom_value {
751   using parse_context = basic_format_parse_context<typename Context::char_type>;
752   const void* value;
753   void (*format)(const void* arg, parse_context& parse_ctx, Context& ctx);
754 };
755 
756 // A formatting argument value.
757 template <typename Context> class value {
758  public:
759   using char_type = typename Context::char_type;
760 
761   union {
762     int int_value;
763     unsigned uint_value;
764     long long long_long_value;
765     unsigned long long ulong_long_value;
766     int128_t int128_value;
767     uint128_t uint128_value;
768     bool bool_value;
769     char_type char_value;
770     float float_value;
771     double double_value;
772     long double long_double_value;
773     const void* pointer;
774     string_value<char_type> string;
775     custom_value<Context> custom;
776     const named_arg_base<char_type>* named_arg;
777   };
778 
779   FMT_CONSTEXPR value(int val = 0) : int_value(val) {}
780   FMT_CONSTEXPR value(unsigned val) : uint_value(val) {}
781   value(long long val) : long_long_value(val) {}
782   value(unsigned long long val) : ulong_long_value(val) {}
783   value(int128_t val) : int128_value(val) {}
784   value(uint128_t val) : uint128_value(val) {}
785   value(float val) : float_value(val) {}
786   value(double val) : double_value(val) {}
787   value(long double val) : long_double_value(val) {}
788   value(bool val) : bool_value(val) {}
789   value(char_type val) : char_value(val) {}
790   value(const char_type* val) { string.data = val; }
791   value(basic_string_view<char_type> val) {
792     string.data = val.data();
793     string.size = val.size();
794   }
795   value(const void* val) : pointer(val) {}
796 
797   template <typename T> value(const T& val) {
798     custom.value = &val;
799     // Get the formatter type through the context to allow different contexts
800     // have different extension points, e.g. `formatter<T>` for `format` and
801     // `printf_formatter<T>` for `printf`.
802     custom.format = format_custom_arg<
803         T, conditional_t<has_formatter<T, Context>::value,
804                          typename Context::template formatter_type<T>,
805                          fallback_formatter<T, char_type>>>;
806   }
807 
808   value(const named_arg_base<char_type>& val) { named_arg = &val; }
809 
810  private:
811   // Formats an argument of a custom type, such as a user-defined class.
812   template <typename T, typename Formatter>
813   static void format_custom_arg(
814       const void* arg, basic_format_parse_context<char_type>& parse_ctx,
815       Context& ctx) {
816     Formatter f;
817     parse_ctx.advance_to(f.parse(parse_ctx));
818     ctx.advance_to(f.format(*static_cast<const T*>(arg), ctx));
819   }
820 };
821 
822 template <typename Context, typename T>
823 FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value);
824 
825 // To minimize the number of types we need to deal with, long is translated
826 // either to int or to long long depending on its size.
827 enum { long_short = sizeof(long) == sizeof(int) };
828 using long_type = conditional_t<long_short, int, long long>;
829 using ulong_type = conditional_t<long_short, unsigned, unsigned long long>;
830 
831 // Maps formatting arguments to core types.
832 template <typename Context> struct arg_mapper {
833   using char_type = typename Context::char_type;
834 
835   FMT_CONSTEXPR int map(signed char val) { return val; }
836   FMT_CONSTEXPR unsigned map(unsigned char val) { return val; }
837   FMT_CONSTEXPR int map(short val) { return val; }
838   FMT_CONSTEXPR unsigned map(unsigned short val) { return val; }
839   FMT_CONSTEXPR int map(int val) { return val; }
840   FMT_CONSTEXPR unsigned map(unsigned val) { return val; }
841   FMT_CONSTEXPR long_type map(long val) { return val; }
842   FMT_CONSTEXPR ulong_type map(unsigned long val) { return val; }
843   FMT_CONSTEXPR long long map(long long val) { return val; }
844   FMT_CONSTEXPR unsigned long long map(unsigned long long val) { return val; }
845   FMT_CONSTEXPR int128_t map(int128_t val) { return val; }
846   FMT_CONSTEXPR uint128_t map(uint128_t val) { return val; }
847   FMT_CONSTEXPR bool map(bool val) { return val; }
848 
849   template <typename T, FMT_ENABLE_IF(is_char<T>::value)>
850   FMT_CONSTEXPR char_type map(T val) {
851     static_assert(
852         std::is_same<T, char>::value || std::is_same<T, char_type>::value,
853         "mixing character types is disallowed");
854     return val;
855   }
856 
857   FMT_CONSTEXPR float map(float val) { return val; }
858   FMT_CONSTEXPR double map(double val) { return val; }
859   FMT_CONSTEXPR long double map(long double val) { return val; }
860 
861   FMT_CONSTEXPR const char_type* map(char_type* val) { return val; }
862   FMT_CONSTEXPR const char_type* map(const char_type* val) { return val; }
863   template <typename T, FMT_ENABLE_IF(is_string<T>::value)>
864   FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
865     static_assert(std::is_same<char_type, char_t<T>>::value,
866                   "mixing character types is disallowed");
867     return to_string_view(val);
868   }
869   template <typename T,
870             FMT_ENABLE_IF(
871                 std::is_constructible<basic_string_view<char_type>, T>::value &&
872                 !is_string<T>::value)>
873   FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
874     return basic_string_view<char_type>(val);
875   }
876   template <
877       typename T,
878       FMT_ENABLE_IF(
879           std::is_constructible<std_string_view<char_type>, T>::value &&
880           !std::is_constructible<basic_string_view<char_type>, T>::value &&
881           !is_string<T>::value)>
882   FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
883     return std_string_view<char_type>(val);
884   }
885   FMT_CONSTEXPR const char* map(const signed char* val) {
886     static_assert(std::is_same<char_type, char>::value, "invalid string type");
887     return reinterpret_cast<const char*>(val);
888   }
889   FMT_CONSTEXPR const char* map(const unsigned char* val) {
890     static_assert(std::is_same<char_type, char>::value, "invalid string type");
891     return reinterpret_cast<const char*>(val);
892   }
893 
894   FMT_CONSTEXPR const void* map(void* val) { return val; }
895   FMT_CONSTEXPR const void* map(const void* val) { return val; }
896   FMT_CONSTEXPR const void* map(std::nullptr_t val) { return val; }
897   template <typename T> FMT_CONSTEXPR int map(const T*) {
898     // Formatting of arbitrary pointers is disallowed. If you want to output
899     // a pointer cast it to "void *" or "const void *". In particular, this
900     // forbids formatting of "[const] volatile char *" which is printed as bool
901     // by iostreams.
902     static_assert(!sizeof(T), "formatting of non-void pointers is disallowed");
903     return 0;
904   }
905 
906   template <typename T,
907             FMT_ENABLE_IF(std::is_enum<T>::value &&
908                           !has_formatter<T, Context>::value &&
909                           !has_fallback_formatter<T, Context>::value)>
910   FMT_CONSTEXPR auto map(const T& val) -> decltype(
911       map(static_cast<typename std::underlying_type<T>::type>(val))) {
912     return map(static_cast<typename std::underlying_type<T>::type>(val));
913   }
914   template <typename T,
915             FMT_ENABLE_IF(!is_string<T>::value && !is_char<T>::value &&
916                           !std::is_constructible<basic_string_view<char_type>,
917                                                  T>::value &&
918                           (has_formatter<T, Context>::value ||
919                            has_fallback_formatter<T, Context>::value))>
920   FMT_CONSTEXPR const T& map(const T& val) {
921     return val;
922   }
923 
924   template <typename T>
925   FMT_CONSTEXPR const named_arg_base<char_type>& map(
926       const named_arg<T, char_type>& val) {
927     auto arg = make_arg<Context>(val.value);
928     std::memcpy(val.data, &arg, sizeof(arg));
929     return val;
930   }
931 };
932 
933 // A type constant after applying arg_mapper<Context>.
934 template <typename T, typename Context>
935 using mapped_type_constant =
936     type_constant<decltype(arg_mapper<Context>().map(std::declval<const T&>())),
937                   typename Context::char_type>;
938 
939 enum { packed_arg_bits = 5 };
940 // Maximum number of arguments with packed types.
941 enum { max_packed_args = 63 / packed_arg_bits };
942 enum : unsigned long long { is_unpacked_bit = 1ULL << 63 };
943 
944 template <typename Context> class arg_map;
945 }  // namespace internal
946 
947 // A formatting argument. It is a trivially copyable/constructible type to
948 // allow storage in basic_memory_buffer.
949 template <typename Context> class basic_format_arg {
950  private:
951   internal::value<Context> value_;
952   internal::type type_;
953 
954   template <typename ContextType, typename T>
955   friend FMT_CONSTEXPR basic_format_arg<ContextType> internal::make_arg(
956       const T& value);
957 
958   template <typename Visitor, typename Ctx>
959   friend FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
960                                              const basic_format_arg<Ctx>& arg)
961       -> decltype(vis(0));
962 
963   friend class basic_format_args<Context>;
964   friend class internal::arg_map<Context>;
965 
966   using char_type = typename Context::char_type;
967 
968  public:
969   class handle {
970    public:
971     explicit handle(internal::custom_value<Context> custom) : custom_(custom) {}
972 
973     void format(basic_format_parse_context<char_type>& parse_ctx,
974                 Context& ctx) const {
975       custom_.format(custom_.value, parse_ctx, ctx);
976     }
977 
978    private:
979     internal::custom_value<Context> custom_;
980   };
981 
982   FMT_CONSTEXPR basic_format_arg() : type_(internal::none_type) {}
983 
984   FMT_CONSTEXPR explicit operator bool() const FMT_NOEXCEPT {
985     return type_ != internal::none_type;
986   }
987 
988   internal::type type() const { return type_; }
989 
990   bool is_integral() const { return internal::is_integral_type(type_); }
991   bool is_arithmetic() const { return internal::is_arithmetic_type(type_); }
992 };
993 
994 /**
995   \rst
996   Visits an argument dispatching to the appropriate visit method based on
997   the argument type. For example, if the argument type is ``double`` then
998   ``vis(value)`` will be called with the value of type ``double``.
999   \endrst
1000  */
1001 template <typename Visitor, typename Context>
1002 FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
1003                                     const basic_format_arg<Context>& arg)
1004     -> decltype(vis(0)) {
1005   using char_type = typename Context::char_type;
1006   switch (arg.type_) {
1007   case internal::none_type:
1008     break;
1009   case internal::named_arg_type:
1010     FMT_ASSERT(false, "invalid argument type");
1011     break;
1012   case internal::int_type:
1013     return vis(arg.value_.int_value);
1014   case internal::uint_type:
1015     return vis(arg.value_.uint_value);
1016   case internal::long_long_type:
1017     return vis(arg.value_.long_long_value);
1018   case internal::ulong_long_type:
1019     return vis(arg.value_.ulong_long_value);
1020 #if FMT_USE_INT128
1021   case internal::int128_type:
1022     return vis(arg.value_.int128_value);
1023   case internal::uint128_type:
1024     return vis(arg.value_.uint128_value);
1025 #else
1026   case internal::int128_type:
1027   case internal::uint128_type:
1028     break;
1029 #endif
1030   case internal::bool_type:
1031     return vis(arg.value_.bool_value);
1032   case internal::char_type:
1033     return vis(arg.value_.char_value);
1034   case internal::float_type:
1035     return vis(arg.value_.float_value);
1036   case internal::double_type:
1037     return vis(arg.value_.double_value);
1038   case internal::long_double_type:
1039     return vis(arg.value_.long_double_value);
1040   case internal::cstring_type:
1041     return vis(arg.value_.string.data);
1042   case internal::string_type:
1043     return vis(basic_string_view<char_type>(arg.value_.string.data,
1044                                             arg.value_.string.size));
1045   case internal::pointer_type:
1046     return vis(arg.value_.pointer);
1047   case internal::custom_type:
1048     return vis(typename basic_format_arg<Context>::handle(arg.value_.custom));
1049   }
1050   return vis(monostate());
1051 }
1052 
1053 namespace internal {
1054 // A map from argument names to their values for named arguments.
1055 template <typename Context> class arg_map {
1056  private:
1057   using char_type = typename Context::char_type;
1058 
1059   struct entry {
1060     basic_string_view<char_type> name;
1061     basic_format_arg<Context> arg;
1062   };
1063 
1064   entry* map_;
1065   unsigned size_;
1066 
1067   void push_back(value<Context> val) {
1068     const auto& named = *val.named_arg;
1069     map_[size_] = {named.name, named.template deserialize<Context>()};
1070     ++size_;
1071   }
1072 
1073  public:
1074   arg_map(const arg_map&) = delete;
1075   void operator=(const arg_map&) = delete;
1076   arg_map() : map_(nullptr), size_(0) {}
1077   void init(const basic_format_args<Context>& args);
1078   ~arg_map() { delete[] map_; }
1079 
1080   basic_format_arg<Context> find(basic_string_view<char_type> name) const {
1081     // The list is unsorted, so just return the first matching name.
1082     for (entry *it = map_, *end = map_ + size_; it != end; ++it) {
1083       if (it->name == name) return it->arg;
1084     }
1085     return {};
1086   }
1087 };
1088 
1089 // A type-erased reference to an std::locale to avoid heavy <locale> include.
1090 class locale_ref {
1091  private:
1092   const void* locale_;  // A type-erased pointer to std::locale.
1093 
1094  public:
1095   locale_ref() : locale_(nullptr) {}
1096   template <typename Locale> explicit locale_ref(const Locale& loc);
1097 
1098   explicit operator bool() const FMT_NOEXCEPT { return locale_ != nullptr; }
1099 
1100   template <typename Locale> Locale get() const;
1101 };
1102 
1103 template <typename> constexpr unsigned long long encode_types() { return 0; }
1104 
1105 template <typename Context, typename Arg, typename... Args>
1106 constexpr unsigned long long encode_types() {
1107   return mapped_type_constant<Arg, Context>::value |
1108          (encode_types<Context, Args...>() << packed_arg_bits);
1109 }
1110 
1111 template <typename Context, typename T>
1112 FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value) {
1113   basic_format_arg<Context> arg;
1114   arg.type_ = mapped_type_constant<T, Context>::value;
1115   arg.value_ = arg_mapper<Context>().map(value);
1116   return arg;
1117 }
1118 
1119 template <bool IS_PACKED, typename Context, typename T,
1120           FMT_ENABLE_IF(IS_PACKED)>
1121 inline value<Context> make_arg(const T& val) {
1122   return arg_mapper<Context>().map(val);
1123 }
1124 
1125 template <bool IS_PACKED, typename Context, typename T,
1126           FMT_ENABLE_IF(!IS_PACKED)>
1127 inline basic_format_arg<Context> make_arg(const T& value) {
1128   return make_arg<Context>(value);
1129 }
1130 }  // namespace internal
1131 
1132 // Formatting context.
1133 template <typename OutputIt, typename Char> class basic_format_context {
1134  public:
1135   /** The character type for the output. */
1136   using char_type = Char;
1137 
1138  private:
1139   OutputIt out_;
1140   basic_format_args<basic_format_context> args_;
1141   internal::arg_map<basic_format_context> map_;
1142   internal::locale_ref loc_;
1143 
1144  public:
1145   using iterator = OutputIt;
1146   using format_arg = basic_format_arg<basic_format_context>;
1147   template <typename T> using formatter_type = formatter<T, char_type>;
1148 
1149   basic_format_context(const basic_format_context&) = delete;
1150   void operator=(const basic_format_context&) = delete;
1151   /**
1152    Constructs a ``basic_format_context`` object. References to the arguments are
1153    stored in the object so make sure they have appropriate lifetimes.
1154    */
1155   basic_format_context(OutputIt out,
1156                        basic_format_args<basic_format_context> ctx_args,
1157                        internal::locale_ref loc = internal::locale_ref())
1158       : out_(out), args_(ctx_args), loc_(loc) {}
1159 
1160   format_arg arg(int id) const { return args_.get(id); }
1161 
1162   // Checks if manual indexing is used and returns the argument with the
1163   // specified name.
1164   format_arg arg(basic_string_view<char_type> name);
1165 
1166   internal::error_handler error_handler() { return {}; }
1167   void on_error(const char* message) { error_handler().on_error(message); }
1168 
1169   // Returns an iterator to the beginning of the output range.
1170   iterator out() { return out_; }
1171 
1172   // Advances the begin iterator to ``it``.
1173   void advance_to(iterator it) { out_ = it; }
1174 
1175   internal::locale_ref locale() { return loc_; }
1176 };
1177 
1178 template <typename Char>
1179 using buffer_context =
1180     basic_format_context<std::back_insert_iterator<internal::buffer<Char>>,
1181                          Char>;
1182 using format_context = buffer_context<char>;
1183 using wformat_context = buffer_context<wchar_t>;
1184 
1185 /**
1186   \rst
1187   An array of references to arguments. It can be implicitly converted into
1188   `~fmt::basic_format_args` for passing into type-erased formatting functions
1189   such as `~fmt::vformat`.
1190   \endrst
1191  */
1192 template <typename Context, typename... Args> class format_arg_store {
1193  private:
1194   static const size_t num_args = sizeof...(Args);
1195   static const bool is_packed = num_args < internal::max_packed_args;
1196 
1197   using value_type = conditional_t<is_packed, internal::value<Context>,
1198                                    basic_format_arg<Context>>;
1199 
1200   // If the arguments are not packed, add one more element to mark the end.
1201   value_type data_[num_args + (num_args == 0 ? 1 : 0)];
1202 
1203   friend class basic_format_args<Context>;
1204 
1205  public:
1206   static constexpr unsigned long long types =
1207       is_packed ? internal::encode_types<Context, Args...>()
1208                 : internal::is_unpacked_bit | num_args;
1209 
1210   format_arg_store(const Args&... args)
1211       : data_{internal::make_arg<is_packed, Context>(args)...} {}
1212 };
1213 
1214 /**
1215   \rst
1216   Constructs an `~fmt::format_arg_store` object that contains references to
1217   arguments and can be implicitly converted to `~fmt::format_args`. `Context`
1218   can be omitted in which case it defaults to `~fmt::context`.
1219   See `~fmt::arg` for lifetime considerations.
1220   \endrst
1221  */
1222 template <typename Context = format_context, typename... Args>
1223 inline format_arg_store<Context, Args...> make_format_args(
1224     const Args&... args) {
1225   return {args...};
1226 }
1227 
1228 /** Formatting arguments. */
1229 template <typename Context> class basic_format_args {
1230  public:
1231   using size_type = int;
1232   using format_arg = basic_format_arg<Context>;
1233 
1234  private:
1235   // To reduce compiled code size per formatting function call, types of first
1236   // max_packed_args arguments are passed in the types_ field.
1237   unsigned long long types_;
1238   union {
1239     // If the number of arguments is less than max_packed_args, the argument
1240     // values are stored in values_, otherwise they are stored in args_.
1241     // This is done to reduce compiled code size as storing larger objects
1242     // may require more code (at least on x86-64) even if the same amount of
1243     // data is actually copied to stack. It saves ~10% on the bloat test.
1244     const internal::value<Context>* values_;
1245     const format_arg* args_;
1246   };
1247 
1248   bool is_packed() const { return (types_ & internal::is_unpacked_bit) == 0; }
1249 
1250   internal::type type(int index) const {
1251     int shift = index * internal::packed_arg_bits;
1252     unsigned int mask = (1 << internal::packed_arg_bits) - 1;
1253     return static_cast<internal::type>((types_ >> shift) & mask);
1254   }
1255 
1256   friend class internal::arg_map<Context>;
1257 
1258   void set_data(const internal::value<Context>* values) { values_ = values; }
1259   void set_data(const format_arg* args) { args_ = args; }
1260 
1261   format_arg do_get(int index) const {
1262     format_arg arg;
1263     if (!is_packed()) {
1264       auto num_args = max_size();
1265       if (index < num_args) arg = args_[index];
1266       return arg;
1267     }
1268     if (index > internal::max_packed_args) return arg;
1269     arg.type_ = type(index);
1270     if (arg.type_ == internal::none_type) return arg;
1271     internal::value<Context>& val = arg.value_;
1272     val = values_[index];
1273     return arg;
1274   }
1275 
1276  public:
1277   basic_format_args() : types_(0) {}
1278 
1279   /**
1280    \rst
1281    Constructs a `basic_format_args` object from `~fmt::format_arg_store`.
1282    \endrst
1283    */
1284   template <typename... Args>
1285   basic_format_args(const format_arg_store<Context, Args...>& store)
1286       : types_(static_cast<unsigned long long>(store.types)) {
1287     set_data(store.data_);
1288   }
1289 
1290   /**
1291    \rst
1292    Constructs a `basic_format_args` object from a dynamic set of arguments.
1293    \endrst
1294    */
1295   basic_format_args(const format_arg* args, int count)
1296       : types_(internal::is_unpacked_bit | internal::to_unsigned(count)) {
1297     set_data(args);
1298   }
1299 
1300   /** Returns the argument at specified index. */
1301   format_arg get(int index) const {
1302     format_arg arg = do_get(index);
1303     if (arg.type_ == internal::named_arg_type)
1304       arg = arg.value_.named_arg->template deserialize<Context>();
1305     return arg;
1306   }
1307 
1308   int max_size() const {
1309     unsigned long long max_packed = internal::max_packed_args;
1310     return static_cast<int>(is_packed() ? max_packed
1311                                         : types_ & ~internal::is_unpacked_bit);
1312   }
1313 };
1314 
1315 /** An alias to ``basic_format_args<context>``. */
1316 // It is a separate type rather than an alias to make symbols readable.
1317 struct format_args : basic_format_args<format_context> {
1318   template <typename... Args>
1319   format_args(Args&&... args)
1320       : basic_format_args<format_context>(std::forward<Args>(args)...) {}
1321 };
1322 struct wformat_args : basic_format_args<wformat_context> {
1323   template <typename... Args>
1324   wformat_args(Args&&... args)
1325       : basic_format_args<wformat_context>(std::forward<Args>(args)...) {}
1326 };
1327 
1328 template <typename Container> struct is_contiguous : std::false_type {};
1329 
1330 template <typename Char>
1331 struct is_contiguous<std::basic_string<Char>> : std::true_type {};
1332 
1333 template <typename Char>
1334 struct is_contiguous<internal::buffer<Char>> : std::true_type {};
1335 
1336 namespace internal {
1337 
1338 template <typename OutputIt>
1339 struct is_contiguous_back_insert_iterator : std::false_type {};
1340 template <typename Container>
1341 struct is_contiguous_back_insert_iterator<std::back_insert_iterator<Container>>
1342     : is_contiguous<Container> {};
1343 
1344 template <typename Char> struct named_arg_base {
1345   basic_string_view<Char> name;
1346 
1347   // Serialized value<context>.
1348   mutable char data[sizeof(basic_format_arg<buffer_context<Char>>)];
1349 
1350   named_arg_base(basic_string_view<Char> nm) : name(nm) {}
1351 
1352   template <typename Context> basic_format_arg<Context> deserialize() const {
1353     basic_format_arg<Context> arg;
1354     std::memcpy(&arg, data, sizeof(basic_format_arg<Context>));
1355     return arg;
1356   }
1357 };
1358 
1359 template <typename T, typename Char> struct named_arg : named_arg_base<Char> {
1360   const T& value;
1361 
1362   named_arg(basic_string_view<Char> name, const T& val)
1363       : named_arg_base<Char>(name), value(val) {}
1364 };
1365 
1366 template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
1367 inline void check_format_string(const S&) {
1368 #if defined(FMT_ENFORCE_COMPILE_STRING)
1369   static_assert(is_compile_string<S>::value,
1370                 "FMT_ENFORCE_COMPILE_STRING requires all format strings to "
1371                 "utilize FMT_STRING() or fmt().");
1372 #endif
1373 }
1374 template <typename..., typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
1375 void check_format_string(S);
1376 
1377 struct view {};
1378 template <bool...> struct bool_pack;
1379 template <bool... Args>
1380 using all_true =
1381     std::is_same<bool_pack<Args..., true>, bool_pack<true, Args...>>;
1382 
1383 template <typename... Args, typename S, typename Char = char_t<S>>
1384 inline format_arg_store<buffer_context<Char>, remove_reference_t<Args>...>
1385 make_args_checked(const S& format_str,
1386                   const remove_reference_t<Args>&... args) {
1387   static_assert(all_true<(!std::is_base_of<view, remove_reference_t<Args>>() ||
1388                           !std::is_reference<Args>())...>::value,
1389                 "passing views as lvalues is disallowed");
1390   check_format_string<remove_const_t<remove_reference_t<Args>>...>(format_str);
1391   return {args...};
1392 }
1393 
1394 template <typename Char>
1395 std::basic_string<Char> vformat(basic_string_view<Char> format_str,
1396                                 basic_format_args<buffer_context<Char>> args);
1397 
1398 template <typename Char>
1399 typename buffer_context<Char>::iterator vformat_to(
1400     buffer<Char>& buf, basic_string_view<Char> format_str,
1401     basic_format_args<buffer_context<Char>> args);
1402 }  // namespace internal
1403 
1404 /**
1405   \rst
1406   Returns a named argument to be used in a formatting function.
1407 
1408   The named argument holds a reference and does not extend the lifetime
1409   of its arguments.
1410   Consequently, a dangling reference can accidentally be created.
1411   The user should take care to only pass this function temporaries when
1412   the named argument is itself a temporary, as per the following example.
1413 
1414   **Example**::
1415 
1416     fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
1417   \endrst
1418  */
1419 template <typename S, typename T, typename Char = char_t<S>>
1420 inline internal::named_arg<T, Char> arg(const S& name, const T& arg) {
1421   static_assert(internal::is_string<S>::value, "");
1422   return {name, arg};
1423 }
1424 
1425 // Disable nested named arguments, e.g. ``arg("a", arg("b", 42))``.
1426 template <typename S, typename T, typename Char>
1427 void arg(S, internal::named_arg<T, Char>) = delete;
1428 
1429 /** Formats a string and writes the output to ``out``. */
1430 // GCC 8 and earlier cannot handle std::back_insert_iterator<Container> with
1431 // vformat_to<ArgFormatter>(...) overload, so SFINAE on iterator type instead.
1432 template <typename OutputIt, typename S, typename Char = char_t<S>,
1433           FMT_ENABLE_IF(
1434               internal::is_contiguous_back_insert_iterator<OutputIt>::value)>
1435 OutputIt vformat_to(OutputIt out, const S& format_str,
1436                     basic_format_args<buffer_context<Char>> args) {
1437   using container = remove_reference_t<decltype(internal::get_container(out))>;
1438   internal::container_buffer<container> buf((internal::get_container(out)));
1439   internal::vformat_to(buf, to_string_view(format_str), args);
1440   return out;
1441 }
1442 
1443 template <typename Container, typename S, typename... Args,
1444           FMT_ENABLE_IF(
1445               is_contiguous<Container>::value&& internal::is_string<S>::value)>
1446 inline std::back_insert_iterator<Container> format_to(
1447     std::back_insert_iterator<Container> out, const S& format_str,
1448     Args&&... args) {
1449   return vformat_to(
1450       out, to_string_view(format_str),
1451       {internal::make_args_checked<Args...>(format_str, args...)});
1452 }
1453 
1454 template <typename S, typename Char = char_t<S>>
1455 inline std::basic_string<Char> vformat(
1456     const S& format_str, basic_format_args<buffer_context<Char>> args) {
1457   return internal::vformat(to_string_view(format_str), args);
1458 }
1459 
1460 /**
1461   \rst
1462   Formats arguments and returns the result as a string.
1463 
1464   **Example**::
1465 
1466     #include <fmt/core.h>
1467     std::string message = fmt::format("The answer is {}", 42);
1468   \endrst
1469 */
1470 // Pass char_t as a default template parameter instead of using
1471 // std::basic_string<char_t<S>> to reduce the symbol size.
1472 template <typename S, typename... Args, typename Char = char_t<S>>
1473 inline std::basic_string<Char> format(const S& format_str, Args&&... args) {
1474   return internal::vformat(
1475       to_string_view(format_str),
1476       {internal::make_args_checked<Args...>(format_str, args...)});
1477 }
1478 
1479 FMT_API void vprint(std::FILE* f, string_view format_str, format_args args);
1480 FMT_API void vprint(string_view format_str, format_args args);
1481 
1482 /**
1483   \rst
1484   Prints formatted data to the file *f*. For wide format strings,
1485   *f* should be in wide-oriented mode set via ``fwide(f, 1)`` or
1486   ``_setmode(_fileno(f), _O_U8TEXT)`` on Windows.
1487 
1488   **Example**::
1489 
1490     fmt::print(stderr, "Don't {}!", "panic");
1491   \endrst
1492  */
1493 template <typename S, typename... Args,
1494           FMT_ENABLE_IF(internal::is_string<S>::value)>
1495 inline void print(std::FILE* f, const S& format_str, Args&&... args) {
1496   vprint(f, to_string_view(format_str),
1497          internal::make_args_checked<Args...>(format_str, args...));
1498 }
1499 
1500 /**
1501   \rst
1502   Prints formatted data to ``stdout``.
1503 
1504   **Example**::
1505 
1506     fmt::print("Elapsed time: {0:.2f} seconds", 1.23);
1507   \endrst
1508  */
1509 template <typename S, typename... Args,
1510           FMT_ENABLE_IF(internal::is_string<S>::value)>
1511 inline void print(const S& format_str, Args&&... args) {
1512   vprint(to_string_view(format_str),
1513          internal::make_args_checked<Args...>(format_str, args...));
1514 }
1515 FMT_END_NAMESPACE
1516 
1517 #endif  // FMT_CORE_H_
1518