fmt-11.0.2/include/fmt/compile.h

   1 // Formatting library for C++ - experimental format string compilation
   2 //
   3 // Copyright (c) 2012 - present, Victor Zverovich and fmt contributors
   4 // All rights reserved.
   5 //
   6 // For the license information refer to format.h.
   7
   8 #ifndef FMT_COMPILE_H_
   9 #define FMT_COMPILE_H_
  10
  11 #ifndef FMT_MODULE
  12 #  include <iterator>  // std::back_inserter
  13 #endif
  14
  15 #include "format.h"
  16
  17 FMT_BEGIN_NAMESPACE
  18
  19 // A compile-time string which is compiled into fast formatting code.
  20 FMT_EXPORT class compiled_string {};
  21
  22 namespace detail {
  23
  24 template <typename T, typename InputIt>
  25 FMT_CONSTEXPR inline auto copy(InputIt begin, InputIt end, counting_iterator it)
  26     -> counting_iterator {
  27   return it + (end - begin);
  28 }
  29
  30 template <typename S>
  31 struct is_compiled_string : std::is_base_of<compiled_string, S> {};
  32
  33 /**
  34  * Converts a string literal `s` into a format string that will be parsed at
  35  * compile time and converted into efficient formatting code. Requires C++17
  36  * `constexpr if` compiler support.
  37  *
  38  * **Example**:
  39  *
  40  *     // Converts 42 into std::string using the most efficient method and no
  41  *     // runtime format string processing.
  42  *     std::string s = fmt::format(FMT_COMPILE("{}"), 42);
  43  */
  44 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
  45 #  define FMT_COMPILE(s) FMT_STRING_IMPL(s, fmt::compiled_string, explicit)
  46 #else
  47 #  define FMT_COMPILE(s) FMT_STRING(s)
  48 #endif
  49
  50 #if FMT_USE_NONTYPE_TEMPLATE_ARGS
  51 template <typename Char, size_t N,
  52           fmt::detail_exported::fixed_string<Char, N> Str>
  53 struct udl_compiled_string : compiled_string {
  54   using char_type = Char;
  55   explicit constexpr operator basic_string_view<char_type>() const {
  56     return {Str.data, N - 1};
  57   }
  58 };
  59 #endif
  60
  61 template <typename T, typename... Tail>
  62 auto first(const T& value, const Tail&...) -> const T& {
  63   return value;
  64 }
  65
  66 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
  67 template <typename... Args> struct type_list {};
  68
  69 // Returns a reference to the argument at index N from [first, rest...].
  70 template <int N, typename T, typename... Args>
  71 constexpr const auto& get([[maybe_unused]] const T& first,
  72                           [[maybe_unused]] const Args&... rest) {
  73   static_assert(N < 1 + sizeof...(Args), "index is out of bounds");
  74   if constexpr (N == 0)
  75     return first;
  76   else
  77     return detail::get<N - 1>(rest...);
  78 }
  79
  80 template <typename Char, typename... Args>
  81 constexpr int get_arg_index_by_name(basic_string_view<Char> name,
  82                                     type_list<Args...>) {
  83   return get_arg_index_by_name<Args...>(name);
  84 }
  85
  86 template <int N, typename> struct get_type_impl;
  87
  88 template <int N, typename... Args> struct get_type_impl<N, type_list<Args...>> {
  89   using type =
  90       remove_cvref_t<decltype(detail::get<N>(std::declval<Args>()...))>;
  91 };
  92
  93 template <int N, typename T>
  94 using get_type = typename get_type_impl<N, T>::type;
  95
  96 template <typename T> struct is_compiled_format : std::false_type {};
  97
  98 template <typename Char> struct text {
  99   basic_string_view<Char> data;
 100   using char_type = Char;
 101
 102   template <typename OutputIt, typename... Args>
 103   constexpr OutputIt format(OutputIt out, const Args&...) const {
 104     return write<Char>(out, data);
 105   }
 106 };
 107
 108 template <typename Char>
 109 struct is_compiled_format<text<Char>> : std::true_type {};
 110
 111 template <typename Char>
 112 constexpr text<Char> make_text(basic_string_view<Char> s, size_t pos,
 113                                size_t size) {
 114   return {{&s[pos], size}};
 115 }
 116
 117 template <typename Char> struct code_unit {
 118   Char value;
 119   using char_type = Char;
 120
 121   template <typename OutputIt, typename... Args>
 122   constexpr OutputIt format(OutputIt out, const Args&...) const {
 123     *out++ = value;
 124     return out;
 125   }
 126 };
 127
 128 // This ensures that the argument type is convertible to `const T&`.
 129 template <typename T, int N, typename... Args>
 130 constexpr const T& get_arg_checked(const Args&... args) {
 131   const auto& arg = detail::get<N>(args...);
 132   if constexpr (detail::is_named_arg<remove_cvref_t<decltype(arg)>>()) {
 133     return arg.value;
 134   } else {
 135     return arg;
 136   }
 137 }
 138
 139 template <typename Char>
 140 struct is_compiled_format<code_unit<Char>> : std::true_type {};
 141
 142 // A replacement field that refers to argument N.
 143 template <typename Char, typename T, int N> struct field {
 144   using char_type = Char;
 145
 146   template <typename OutputIt, typename... Args>
 147   constexpr OutputIt format(OutputIt out, const Args&... args) const {
 148     const T& arg = get_arg_checked<T, N>(args...);
 149     if constexpr (std::is_convertible<T, basic_string_view<Char>>::value) {
 150       auto s = basic_string_view<Char>(arg);
 151       return copy<Char>(s.begin(), s.end(), out);
 152     }
 153     return write<Char>(out, arg);
 154   }
 155 };
 156
 157 template <typename Char, typename T, int N>
 158 struct is_compiled_format<field<Char, T, N>> : std::true_type {};
 159
 160 // A replacement field that refers to argument with name.
 161 template <typename Char> struct runtime_named_field {
 162   using char_type = Char;
 163   basic_string_view<Char> name;
 164
 165   template <typename OutputIt, typename T>
 166   constexpr static bool try_format_argument(
 167       OutputIt& out,
 168       // [[maybe_unused]] due to unused-but-set-parameter warning in GCC 7,8,9
 169       [[maybe_unused]] basic_string_view<Char> arg_name, const T& arg) {
 170     if constexpr (is_named_arg<typename std::remove_cv<T>::type>::value) {
 171       if (arg_name == arg.name) {
 172         out = write<Char>(out, arg.value);
 173         return true;
 174       }
 175     }
 176     return false;
 177   }
 178
 179   template <typename OutputIt, typename... Args>
 180   constexpr OutputIt format(OutputIt out, const Args&... args) const {
 181     bool found = (try_format_argument(out, name, args) || ...);
 182     if (!found) {
 183       FMT_THROW(format_error("argument with specified name is not found"));
 184     }
 185     return out;
 186   }
 187 };
 188
 189 template <typename Char>
 190 struct is_compiled_format<runtime_named_field<Char>> : std::true_type {};
 191
 192 // A replacement field that refers to argument N and has format specifiers.
 193 template <typename Char, typename T, int N> struct spec_field {
 194   using char_type = Char;
 195   formatter<T, Char> fmt;
 196
 197   template <typename OutputIt, typename... Args>
 198   constexpr FMT_INLINE OutputIt format(OutputIt out,
 199                                        const Args&... args) const {
 200     const auto& vargs =
 201         fmt::make_format_args<basic_format_context<OutputIt, Char>>(args...);
 202     basic_format_context<OutputIt, Char> ctx(out, vargs);
 203     return fmt.format(get_arg_checked<T, N>(args...), ctx);
 204   }
 205 };
 206
 207 template <typename Char, typename T, int N>
 208 struct is_compiled_format<spec_field<Char, T, N>> : std::true_type {};
 209
 210 template <typename L, typename R> struct concat {
 211   L lhs;
 212   R rhs;
 213   using char_type = typename L::char_type;
 214
 215   template <typename OutputIt, typename... Args>
 216   constexpr OutputIt format(OutputIt out, const Args&... args) const {
 217     out = lhs.format(out, args...);
 218     return rhs.format(out, args...);
 219   }
 220 };
 221
 222 template <typename L, typename R>
 223 struct is_compiled_format<concat<L, R>> : std::true_type {};
 224
 225 template <typename L, typename R>
 226 constexpr concat<L, R> make_concat(L lhs, R rhs) {
 227   return {lhs, rhs};
 228 }
 229
 230 struct unknown_format {};
 231
 232 template <typename Char>
 233 constexpr size_t parse_text(basic_string_view<Char> str, size_t pos) {
 234   for (size_t size = str.size(); pos != size; ++pos) {
 235     if (str[pos] == '{' || str[pos] == '}') break;
 236   }
 237   return pos;
 238 }
 239
 240 template <typename Args, size_t POS, int ID, typename S>
 241 constexpr auto compile_format_string(S fmt);
 242
 243 template <typename Args, size_t POS, int ID, typename T, typename S>
 244 constexpr auto parse_tail(T head, S fmt) {
 245   if constexpr (POS != basic_string_view<typename S::char_type>(fmt).size()) {
 246     constexpr auto tail = compile_format_string<Args, POS, ID>(fmt);
 247     if constexpr (std::is_same<remove_cvref_t<decltype(tail)>,
 248                                unknown_format>())
 249       return tail;
 250     else
 251       return make_concat(head, tail);
 252   } else {
 253     return head;
 254   }
 255 }
 256
 257 template <typename T, typename Char> struct parse_specs_result {
 258   formatter<T, Char> fmt;
 259   size_t end;
 260   int next_arg_id;
 261 };
 262
 263 enum { manual_indexing_id = -1 };
 264
 265 template <typename T, typename Char>
 266 constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
 267                                                   size_t pos, int next_arg_id) {
 268   str.remove_prefix(pos);
 269   auto ctx =
 270       compile_parse_context<Char>(str, max_value<int>(), nullptr, next_arg_id);
 271   auto f = formatter<T, Char>();
 272   auto end = f.parse(ctx);
 273   return {f, pos + fmt::detail::to_unsigned(end - str.data()),
 274           next_arg_id == 0 ? manual_indexing_id : ctx.next_arg_id()};
 275 }
 276
 277 template <typename Char> struct arg_id_handler {
 278   arg_ref<Char> arg_id;
 279
 280   constexpr int on_auto() {
 281     FMT_ASSERT(false, "handler cannot be used with automatic indexing");
 282     return 0;
 283   }
 284   constexpr int on_index(int id) {
 285     arg_id = arg_ref<Char>(id);
 286     return 0;
 287   }
 288   constexpr int on_name(basic_string_view<Char> id) {
 289     arg_id = arg_ref<Char>(id);
 290     return 0;
 291   }
 292 };
 293
 294 template <typename Char> struct parse_arg_id_result {
 295   arg_ref<Char> arg_id;
 296   const Char* arg_id_end;
 297 };
 298
 299 template <int ID, typename Char>
 300 constexpr auto parse_arg_id(const Char* begin, const Char* end) {
 301   auto handler = arg_id_handler<Char>{arg_ref<Char>{}};
 302   auto arg_id_end = parse_arg_id(begin, end, handler);
 303   return parse_arg_id_result<Char>{handler.arg_id, arg_id_end};
 304 }
 305
 306 template <typename T, typename Enable = void> struct field_type {
 307   using type = remove_cvref_t<T>;
 308 };
 309
 310 template <typename T>
 311 struct field_type<T, enable_if_t<detail::is_named_arg<T>::value>> {
 312   using type = remove_cvref_t<decltype(T::value)>;
 313 };
 314
 315 template <typename T, typename Args, size_t END_POS, int ARG_INDEX, int NEXT_ID,
 316           typename S>
 317 constexpr auto parse_replacement_field_then_tail(S fmt) {
 318   using char_type = typename S::char_type;
 319   constexpr auto str = basic_string_view<char_type>(fmt);
 320   constexpr char_type c = END_POS != str.size() ? str[END_POS] : char_type();
 321   if constexpr (c == '}') {
 322     return parse_tail<Args, END_POS + 1, NEXT_ID>(
 323         field<char_type, typename field_type<T>::type, ARG_INDEX>(), fmt);
 324   } else if constexpr (c != ':') {
 325     FMT_THROW(format_error("expected ':'"));
 326   } else {
 327     constexpr auto result = parse_specs<typename field_type<T>::type>(
 328         str, END_POS + 1, NEXT_ID == manual_indexing_id ? 0 : NEXT_ID);
 329     if constexpr (result.end >= str.size() || str[result.end] != '}') {
 330       FMT_THROW(format_error("expected '}'"));
 331       return 0;
 332     } else {
 333       return parse_tail<Args, result.end + 1, result.next_arg_id>(
 334           spec_field<char_type, typename field_type<T>::type, ARG_INDEX>{
 335               result.fmt},
 336           fmt);
 337     }
 338   }
 339 }
 340
 341 // Compiles a non-empty format string and returns the compiled representation
 342 // or unknown_format() on unrecognized input.
 343 template <typename Args, size_t POS, int ID, typename S>
 344 constexpr auto compile_format_string(S fmt) {
 345   using char_type = typename S::char_type;
 346   constexpr auto str = basic_string_view<char_type>(fmt);
 347   if constexpr (str[POS] == '{') {
 348     if constexpr (POS + 1 == str.size())
 349       FMT_THROW(format_error("unmatched '{' in format string"));
 350     if constexpr (str[POS + 1] == '{') {
 351       return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), fmt);
 352     } else if constexpr (str[POS + 1] == '}' || str[POS + 1] == ':') {
 353       static_assert(ID != manual_indexing_id,
 354                     "cannot switch from manual to automatic argument indexing");
 355       constexpr auto next_id =
 356           ID != manual_indexing_id ? ID + 1 : manual_indexing_id;
 357       return parse_replacement_field_then_tail<get_type<ID, Args>, Args,
 358                                                POS + 1, ID, next_id>(fmt);
 359     } else {
 360       constexpr auto arg_id_result =
 361           parse_arg_id<ID>(str.data() + POS + 1, str.data() + str.size());
 362       constexpr auto arg_id_end_pos = arg_id_result.arg_id_end - str.data();
 363       constexpr char_type c =
 364           arg_id_end_pos != str.size() ? str[arg_id_end_pos] : char_type();
 365       static_assert(c == '}' || c == ':', "missing '}' in format string");
 366       if constexpr (arg_id_result.arg_id.kind == arg_id_kind::index) {
 367         static_assert(
 368             ID == manual_indexing_id || ID == 0,
 369             "cannot switch from automatic to manual argument indexing");
 370         constexpr auto arg_index = arg_id_result.arg_id.val.index;
 371         return parse_replacement_field_then_tail<get_type<arg_index, Args>,
 372                                                  Args, arg_id_end_pos,
 373                                                  arg_index, manual_indexing_id>(
 374             fmt);
 375       } else if constexpr (arg_id_result.arg_id.kind == arg_id_kind::name) {
 376         constexpr auto arg_index =
 377             get_arg_index_by_name(arg_id_result.arg_id.val.name, Args{});
 378         if constexpr (arg_index >= 0) {
 379           constexpr auto next_id =
 380               ID != manual_indexing_id ? ID + 1 : manual_indexing_id;
 381           return parse_replacement_field_then_tail<
 382               decltype(get_type<arg_index, Args>::value), Args, arg_id_end_pos,
 383               arg_index, next_id>(fmt);
 384         } else if constexpr (c == '}') {
 385           return parse_tail<Args, arg_id_end_pos + 1, ID>(
 386               runtime_named_field<char_type>{arg_id_result.arg_id.val.name},
 387               fmt);
 388         } else if constexpr (c == ':') {
 389           return unknown_format();  // no type info for specs parsing
 390         }
 391       }
 392     }
 393   } else if constexpr (str[POS] == '}') {
 394     if constexpr (POS + 1 == str.size())
 395       FMT_THROW(format_error("unmatched '}' in format string"));
 396     return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), fmt);
 397   } else {
 398     constexpr auto end = parse_text(str, POS + 1);
 399     if constexpr (end - POS > 1) {
 400       return parse_tail<Args, end, ID>(make_text(str, POS, end - POS), fmt);
 401     } else {
 402       return parse_tail<Args, end, ID>(code_unit<char_type>{str[POS]}, fmt);
 403     }
 404   }
 405 }
 406
 407 template <typename... Args, typename S,
 408           FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
 409 constexpr auto compile(S fmt) {
 410   constexpr auto str = basic_string_view<typename S::char_type>(fmt);
 411   if constexpr (str.size() == 0) {
 412     return detail::make_text(str, 0, 0);
 413   } else {
 414     constexpr auto result =
 415         detail::compile_format_string<detail::type_list<Args...>, 0, 0>(fmt);
 416     return result;
 417   }
 418 }
 419 #endif  // defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 420 }  // namespace detail
 421
 422 FMT_BEGIN_EXPORT
 423
 424 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 425
 426 template <typename CompiledFormat, typename... Args,
 427           typename Char = typename CompiledFormat::char_type,
 428           FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
 429 FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
 430                                           const Args&... args) {
 431   auto s = std::basic_string<Char>();
 432   cf.format(std::back_inserter(s), args...);
 433   return s;
 434 }
 435
 436 template <typename OutputIt, typename CompiledFormat, typename... Args,
 437           FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
 438 constexpr FMT_INLINE OutputIt format_to(OutputIt out, const CompiledFormat& cf,
 439                                         const Args&... args) {
 440   return cf.format(out, args...);
 441 }
 442
 443 template <typename S, typename... Args,
 444           FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
 445 FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
 446                                                            Args&&... args) {
 447   if constexpr (std::is_same<typename S::char_type, char>::value) {
 448     constexpr auto str = basic_string_view<typename S::char_type>(S());
 449     if constexpr (str.size() == 2 && str[0] == '{' && str[1] == '}') {
 450       const auto& first = detail::first(args...);
 451       if constexpr (detail::is_named_arg<
 452                         remove_cvref_t<decltype(first)>>::value) {
 453         return fmt::to_string(first.value);
 454       } else {
 455         return fmt::to_string(first);
 456       }
 457     }
 458   }
 459   constexpr auto compiled = detail::compile<Args...>(S());
 460   if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
 461                              detail::unknown_format>()) {
 462     return fmt::format(
 463         static_cast<basic_string_view<typename S::char_type>>(S()),
 464         std::forward<Args>(args)...);
 465   } else {
 466     return fmt::format(compiled, std::forward<Args>(args)...);
 467   }
 468 }
 469
 470 template <typename OutputIt, typename S, typename... Args,
 471           FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
 472 FMT_CONSTEXPR OutputIt format_to(OutputIt out, const S&, Args&&... args) {
 473   constexpr auto compiled = detail::compile<Args...>(S());
 474   if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
 475                              detail::unknown_format>()) {
 476     return fmt::format_to(
 477         out, static_cast<basic_string_view<typename S::char_type>>(S()),
 478         std::forward<Args>(args)...);
 479   } else {
 480     return fmt::format_to(out, compiled, std::forward<Args>(args)...);
 481   }
 482 }
 483 #endif
 484
 485 template <typename OutputIt, typename S, typename... Args,
 486           FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
 487 auto format_to_n(OutputIt out, size_t n, const S& fmt, Args&&... args)
 488     -> format_to_n_result<OutputIt> {
 489   using traits = detail::fixed_buffer_traits;
 490   auto buf = detail::iterator_buffer<OutputIt, char, traits>(out, n);
 491   fmt::format_to(std::back_inserter(buf), fmt, std::forward<Args>(args)...);
 492   return {buf.out(), buf.count()};
 493 }
 494
 495 template <typename S, typename... Args,
 496           FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
 497 FMT_CONSTEXPR20 auto formatted_size(const S& fmt, const Args&... args)
 498     -> size_t {
 499   return fmt::format_to(detail::counting_iterator(), fmt, args...).count();
 500 }
 501
 502 template <typename S, typename... Args,
 503           FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
 504 void print(std::FILE* f, const S& fmt, const Args&... args) {
 505   memory_buffer buffer;
 506   fmt::format_to(std::back_inserter(buffer), fmt, args...);
 507   detail::print(f, {buffer.data(), buffer.size()});
 508 }
 509
 510 template <typename S, typename... Args,
 511           FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
 512 void print(const S& fmt, const Args&... args) {
 513   print(stdout, fmt, args...);
 514 }
 515
 516 #if FMT_USE_NONTYPE_TEMPLATE_ARGS
 517 inline namespace literals {
 518 template <detail_exported::fixed_string Str> constexpr auto operator""_cf() {
 519   using char_t = remove_cvref_t<decltype(Str.data[0])>;
 520   return detail::udl_compiled_string<char_t, sizeof(Str.data) / sizeof(char_t),
 521                                      Str>();
 522 }
 523 }  // namespace literals
 524 #endif
 525
 526 FMT_END_EXPORT
 527 FMT_END_NAMESPACE
 528
 529 #endif  // FMT_COMPILE_H_