include/llvm/ADT/Optional.h

   1 //===- Optional.h - Simple variant for passing optional values --*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 //  This file provides Optional, a template class modeled in the spirit of
  10 //  OCaml's 'opt' variant.  The idea is to strongly type whether or not
  11 //  a value can be optional.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #ifndef LLVM_ADT_OPTIONAL_H
  16 #define LLVM_ADT_OPTIONAL_H
  17
  18 #include "llvm/ADT/None.h"
  19 #include "llvm/Support/Compiler.h"
  20 #include "llvm/Support/type_traits.h"
  21 #include <cassert>
  22 #include <memory>
  23 #include <new>
  24 #include <utility>
  25
  26 namespace llvm {
  27
  28 class raw_ostream;
  29
  30 namespace optional_detail {
  31
  32 struct in_place_t {};
  33
  34 /// Storage for any type.
  35 template <typename T, bool = is_trivially_copyable<T>::value>
  36 class OptionalStorage {
  37   union {
  38     char empty;
  39     T value;
  40   };
  41   bool hasVal;
  42
  43 public:
  44   ~OptionalStorage() { reset(); }
  45
  46   OptionalStorage() noexcept : empty(), hasVal(false) {}
  47
  48   OptionalStorage(OptionalStorage const &other) : OptionalStorage() {
  49     if (other.hasValue()) {
  50       emplace(other.value);
  51     }
  52   }
  53   OptionalStorage(OptionalStorage &&other) : OptionalStorage() {
  54     if (other.hasValue()) {
  55       emplace(std::move(other.value));
  56     }
  57   }
  58
  59   template <class... Args>
  60   explicit OptionalStorage(in_place_t, Args &&... args)
  61       : value(std::forward<Args>(args)...), hasVal(true) {}
  62
  63   void reset() noexcept {
  64     if (hasVal) {
  65       value.~T();
  66       hasVal = false;
  67     }
  68   }
  69
  70   bool hasValue() const noexcept { return hasVal; }
  71
  72   T &getValue() LLVM_LVALUE_FUNCTION noexcept {
  73     assert(hasVal);
  74     return value;
  75   }
  76   T const &getValue() const LLVM_LVALUE_FUNCTION noexcept {
  77     assert(hasVal);
  78     return value;
  79   }
  80 #if LLVM_HAS_RVALUE_REFERENCE_THIS
  81   T &&getValue() && noexcept {
  82     assert(hasVal);
  83     return std::move(value);
  84   }
  85 #endif
  86
  87   template <class... Args> void emplace(Args &&... args) {
  88     reset();
  89     ::new ((void *)std::addressof(value)) T(std::forward<Args>(args)...);
  90     hasVal = true;
  91   }
  92
  93   OptionalStorage &operator=(T const &y) {
  94     if (hasValue()) {
  95       value = y;
  96     } else {
  97       ::new ((void *)std::addressof(value)) T(y);
  98       hasVal = true;
  99     }
 100     return *this;
 101   }
 102   OptionalStorage &operator=(T &&y) {
 103     if (hasValue()) {
 104       value = std::move(y);
 105     } else {
 106       ::new ((void *)std::addressof(value)) T(std::move(y));
 107       hasVal = true;
 108     }
 109     return *this;
 110   }
 111
 112   OptionalStorage &operator=(OptionalStorage const &other) {
 113     if (other.hasValue()) {
 114       if (hasValue()) {
 115         value = other.value;
 116       } else {
 117         ::new ((void *)std::addressof(value)) T(other.value);
 118         hasVal = true;
 119       }
 120     } else {
 121       reset();
 122     }
 123     return *this;
 124   }
 125
 126   OptionalStorage &operator=(OptionalStorage &&other) {
 127     if (other.hasValue()) {
 128       if (hasValue()) {
 129         value = std::move(other.value);
 130       } else {
 131         ::new ((void *)std::addressof(value)) T(std::move(other.value));
 132         hasVal = true;
 133       }
 134     } else {
 135       reset();
 136     }
 137     return *this;
 138   }
 139 };
 140
 141 template <typename T> class OptionalStorage<T, true> {
 142   union {
 143     char empty;
 144     T value;
 145   };
 146   bool hasVal = false;
 147
 148 public:
 149   ~OptionalStorage() = default;
 150
 151   OptionalStorage() noexcept : empty{} {}
 152
 153   OptionalStorage(OptionalStorage const &other) = default;
 154   OptionalStorage(OptionalStorage &&other) = default;
 155
 156   OptionalStorage &operator=(OptionalStorage const &other) = default;
 157   OptionalStorage &operator=(OptionalStorage &&other) = default;
 158
 159   template <class... Args>
 160   explicit OptionalStorage(in_place_t, Args &&... args)
 161       : value(std::forward<Args>(args)...), hasVal(true) {}
 162
 163   void reset() noexcept {
 164     if (hasVal) {
 165       value.~T();
 166       hasVal = false;
 167     }
 168   }
 169
 170   bool hasValue() const noexcept { return hasVal; }
 171
 172   T &getValue() LLVM_LVALUE_FUNCTION noexcept {
 173     assert(hasVal);
 174     return value;
 175   }
 176   T const &getValue() const LLVM_LVALUE_FUNCTION noexcept {
 177     assert(hasVal);
 178     return value;
 179   }
 180 #if LLVM_HAS_RVALUE_REFERENCE_THIS
 181   T &&getValue() && noexcept {
 182     assert(hasVal);
 183     return std::move(value);
 184   }
 185 #endif
 186
 187   template <class... Args> void emplace(Args &&... args) {
 188     reset();
 189     ::new ((void *)std::addressof(value)) T(std::forward<Args>(args)...);
 190     hasVal = true;
 191   }
 192
 193   OptionalStorage &operator=(T const &y) {
 194     if (hasValue()) {
 195       value = y;
 196     } else {
 197       ::new ((void *)std::addressof(value)) T(y);
 198       hasVal = true;
 199     }
 200     return *this;
 201   }
 202   OptionalStorage &operator=(T &&y) {
 203     if (hasValue()) {
 204       value = std::move(y);
 205     } else {
 206       ::new ((void *)std::addressof(value)) T(std::move(y));
 207       hasVal = true;
 208     }
 209     return *this;
 210   }
 211 };
 212
 213 } // namespace optional_detail
 214
 215 template <typename T> class Optional {
 216   optional_detail::OptionalStorage<T> Storage;
 217
 218 public:
 219   using value_type = T;
 220
 221   constexpr Optional() {}
 222   constexpr Optional(NoneType) {}
 223
 224   Optional(const T &y) : Storage(optional_detail::in_place_t{}, y) {}
 225   Optional(const Optional &O) = default;
 226
 227   Optional(T &&y) : Storage(optional_detail::in_place_t{}, std::move(y)) {}
 228   Optional(Optional &&O) = default;
 229
 230   Optional &operator=(T &&y) {
 231     Storage = std::move(y);
 232     return *this;
 233   }
 234   Optional &operator=(Optional &&O) = default;
 235
 236   /// Create a new object by constructing it in place with the given arguments.
 237   template <typename... ArgTypes> void emplace(ArgTypes &&... Args) {
 238     Storage.emplace(std::forward<ArgTypes>(Args)...);
 239   }
 240
 241   static inline Optional create(const T *y) {
 242     return y ? Optional(*y) : Optional();
 243   }
 244
 245   Optional &operator=(const T &y) {
 246     Storage = y;
 247     return *this;
 248   }
 249   Optional &operator=(const Optional &O) = default;
 250
 251   void reset() { Storage.reset(); }
 252
 253   const T *getPointer() const { return &Storage.getValue(); }
 254   T *getPointer() { return &Storage.getValue(); }
 255   const T &getValue() const LLVM_LVALUE_FUNCTION { return Storage.getValue(); }
 256   T &getValue() LLVM_LVALUE_FUNCTION { return Storage.getValue(); }
 257
 258   explicit operator bool() const { return hasValue(); }
 259   bool hasValue() const { return Storage.hasValue(); }
 260   const T *operator->() const { return getPointer(); }
 261   T *operator->() { return getPointer(); }
 262   const T &operator*() const LLVM_LVALUE_FUNCTION { return getValue(); }
 263   T &operator*() LLVM_LVALUE_FUNCTION { return getValue(); }
 264
 265   template <typename U>
 266   constexpr T getValueOr(U &&value) const LLVM_LVALUE_FUNCTION {
 267     return hasValue() ? getValue() : std::forward<U>(value);
 268   }
 269
 270 #if LLVM_HAS_RVALUE_REFERENCE_THIS
 271   T &&getValue() && { return std::move(Storage.getValue()); }
 272   T &&operator*() && { return std::move(Storage.getValue()); }
 273
 274   template <typename U>
 275   T getValueOr(U &&value) && {
 276     return hasValue() ? std::move(getValue()) : std::forward<U>(value);
 277   }
 278 #endif
 279 };
 280
 281 template <typename T, typename U>
 282 bool operator==(const Optional<T> &X, const Optional<U> &Y) {
 283   if (X && Y)
 284     return *X == *Y;
 285   return X.hasValue() == Y.hasValue();
 286 }
 287
 288 template <typename T, typename U>
 289 bool operator!=(const Optional<T> &X, const Optional<U> &Y) {
 290   return !(X == Y);
 291 }
 292
 293 template <typename T, typename U>
 294 bool operator<(const Optional<T> &X, const Optional<U> &Y) {
 295   if (X && Y)
 296     return *X < *Y;
 297   return X.hasValue() < Y.hasValue();
 298 }
 299
 300 template <typename T, typename U>
 301 bool operator<=(const Optional<T> &X, const Optional<U> &Y) {
 302   return !(Y < X);
 303 }
 304
 305 template <typename T, typename U>
 306 bool operator>(const Optional<T> &X, const Optional<U> &Y) {
 307   return Y < X;
 308 }
 309
 310 template <typename T, typename U>
 311 bool operator>=(const Optional<T> &X, const Optional<U> &Y) {
 312   return !(X < Y);
 313 }
 314
 315 template<typename T>
 316 bool operator==(const Optional<T> &X, NoneType) {
 317   return !X;
 318 }
 319
 320 template<typename T>
 321 bool operator==(NoneType, const Optional<T> &X) {
 322   return X == None;
 323 }
 324
 325 template<typename T>
 326 bool operator!=(const Optional<T> &X, NoneType) {
 327   return !(X == None);
 328 }
 329
 330 template<typename T>
 331 bool operator!=(NoneType, const Optional<T> &X) {
 332   return X != None;
 333 }
 334
 335 template <typename T> bool operator<(const Optional<T> &X, NoneType) {
 336   return false;
 337 }
 338
 339 template <typename T> bool operator<(NoneType, const Optional<T> &X) {
 340   return X.hasValue();
 341 }
 342
 343 template <typename T> bool operator<=(const Optional<T> &X, NoneType) {
 344   return !(None < X);
 345 }
 346
 347 template <typename T> bool operator<=(NoneType, const Optional<T> &X) {
 348   return !(X < None);
 349 }
 350
 351 template <typename T> bool operator>(const Optional<T> &X, NoneType) {
 352   return None < X;
 353 }
 354
 355 template <typename T> bool operator>(NoneType, const Optional<T> &X) {
 356   return X < None;
 357 }
 358
 359 template <typename T> bool operator>=(const Optional<T> &X, NoneType) {
 360   return None <= X;
 361 }
 362
 363 template <typename T> bool operator>=(NoneType, const Optional<T> &X) {
 364   return X <= None;
 365 }
 366
 367 template <typename T> bool operator==(const Optional<T> &X, const T &Y) {
 368   return X && *X == Y;
 369 }
 370
 371 template <typename T> bool operator==(const T &X, const Optional<T> &Y) {
 372   return Y && X == *Y;
 373 }
 374
 375 template <typename T> bool operator!=(const Optional<T> &X, const T &Y) {
 376   return !(X == Y);
 377 }
 378
 379 template <typename T> bool operator!=(const T &X, const Optional<T> &Y) {
 380   return !(X == Y);
 381 }
 382
 383 template <typename T> bool operator<(const Optional<T> &X, const T &Y) {
 384   return !X || *X < Y;
 385 }
 386
 387 template <typename T> bool operator<(const T &X, const Optional<T> &Y) {
 388   return Y && X < *Y;
 389 }
 390
 391 template <typename T> bool operator<=(const Optional<T> &X, const T &Y) {
 392   return !(Y < X);
 393 }
 394
 395 template <typename T> bool operator<=(const T &X, const Optional<T> &Y) {
 396   return !(Y < X);
 397 }
 398
 399 template <typename T> bool operator>(const Optional<T> &X, const T &Y) {
 400   return Y < X;
 401 }
 402
 403 template <typename T> bool operator>(const T &X, const Optional<T> &Y) {
 404   return Y < X;
 405 }
 406
 407 template <typename T> bool operator>=(const Optional<T> &X, const T &Y) {
 408   return !(X < Y);
 409 }
 410
 411 template <typename T> bool operator>=(const T &X, const Optional<T> &Y) {
 412   return !(X < Y);
 413 }
 414
 415 raw_ostream &operator<<(raw_ostream &OS, NoneType);
 416
 417 template <typename T, typename = decltype(std::declval<raw_ostream &>()
 418                                           << std::declval<const T &>())>
 419 raw_ostream &operator<<(raw_ostream &OS, const Optional<T> &O) {
 420   if (O)
 421     OS << *O;
 422   else
 423     OS << None;
 424   return OS;
 425 }
 426
 427 } // end namespace llvm
 428
 429 #endif // LLVM_ADT_OPTIONAL_H