include/llvm/ADT/ArrayRef.h

   1 //===- ArrayRef.h - Array Reference Wrapper ---------------------*- 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 #ifndef LLVM_ADT_ARRAYREF_H
  10 #define LLVM_ADT_ARRAYREF_H
  11
  12 #include "llvm/ADT/Hashing.h"
  13 #include "llvm/ADT/None.h"
  14 #include "llvm/ADT/SmallVector.h"
  15 #include "llvm/ADT/STLExtras.h"
  16 #include "llvm/Support/Compiler.h"
  17 #include <algorithm>
  18 #include <array>
  19 #include <cassert>
  20 #include <cstddef>
  21 #include <initializer_list>
  22 #include <iterator>
  23 #include <memory>
  24 #include <type_traits>
  25 #include <vector>
  26
  27 namespace llvm {
  28
  29   /// ArrayRef - Represent a constant reference to an array (0 or more elements
  30   /// consecutively in memory), i.e. a start pointer and a length.  It allows
  31   /// various APIs to take consecutive elements easily and conveniently.
  32   ///
  33   /// This class does not own the underlying data, it is expected to be used in
  34   /// situations where the data resides in some other buffer, whose lifetime
  35   /// extends past that of the ArrayRef. For this reason, it is not in general
  36   /// safe to store an ArrayRef.
  37   ///
  38   /// This is intended to be trivially copyable, so it should be passed by
  39   /// value.
  40   template<typename T>
  41   class LLVM_NODISCARD ArrayRef {
  42   public:
  43     using iterator = const T *;
  44     using const_iterator = const T *;
  45     using size_type = size_t;
  46     using reverse_iterator = std::reverse_iterator<iterator>;
  47
  48   private:
  49     /// The start of the array, in an external buffer.
  50     const T *Data = nullptr;
  51
  52     /// The number of elements.
  53     size_type Length = 0;
  54
  55   public:
  56     /// @name Constructors
  57     /// @{
  58
  59     /// Construct an empty ArrayRef.
  60     /*implicit*/ ArrayRef() = default;
  61
  62     /// Construct an empty ArrayRef from None.
  63     /*implicit*/ ArrayRef(NoneType) {}
  64
  65     /// Construct an ArrayRef from a single element.
  66     /*implicit*/ ArrayRef(const T &OneElt)
  67       : Data(&OneElt), Length(1) {}
  68
  69     /// Construct an ArrayRef from a pointer and length.
  70     /*implicit*/ ArrayRef(const T *data, size_t length)
  71       : Data(data), Length(length) {}
  72
  73     /// Construct an ArrayRef from a range.
  74     ArrayRef(const T *begin, const T *end)
  75       : Data(begin), Length(end - begin) {}
  76
  77     /// Construct an ArrayRef from a SmallVector. This is templated in order to
  78     /// avoid instantiating SmallVectorTemplateCommon<T> whenever we
  79     /// copy-construct an ArrayRef.
  80     template<typename U>
  81     /*implicit*/ ArrayRef(const SmallVectorTemplateCommon<T, U> &Vec)
  82       : Data(Vec.data()), Length(Vec.size()) {
  83     }
  84
  85     /// Construct an ArrayRef from a std::vector.
  86     template<typename A>
  87     /*implicit*/ ArrayRef(const std::vector<T, A> &Vec)
  88       : Data(Vec.data()), Length(Vec.size()) {}
  89
  90     /// Construct an ArrayRef from a std::array
  91     template <size_t N>
  92     /*implicit*/ constexpr ArrayRef(const std::array<T, N> &Arr)
  93         : Data(Arr.data()), Length(N) {}
  94
  95     /// Construct an ArrayRef from a C array.
  96     template <size_t N>
  97     /*implicit*/ constexpr ArrayRef(const T (&Arr)[N]) : Data(Arr), Length(N) {}
  98
  99     /// Construct an ArrayRef from a std::initializer_list.
 100     /*implicit*/ ArrayRef(const std::initializer_list<T> &Vec)
 101     : Data(Vec.begin() == Vec.end() ? (T*)nullptr : Vec.begin()),
 102       Length(Vec.size()) {}
 103
 104     /// Construct an ArrayRef<const T*> from ArrayRef<T*>. This uses SFINAE to
 105     /// ensure that only ArrayRefs of pointers can be converted.
 106     template <typename U>
 107     ArrayRef(
 108         const ArrayRef<U *> &A,
 109         typename std::enable_if<
 110            std::is_convertible<U *const *, T const *>::value>::type * = nullptr)
 111       : Data(A.data()), Length(A.size()) {}
 112
 113     /// Construct an ArrayRef<const T*> from a SmallVector<T*>. This is
 114     /// templated in order to avoid instantiating SmallVectorTemplateCommon<T>
 115     /// whenever we copy-construct an ArrayRef.
 116     template<typename U, typename DummyT>
 117     /*implicit*/ ArrayRef(
 118       const SmallVectorTemplateCommon<U *, DummyT> &Vec,
 119       typename std::enable_if<
 120           std::is_convertible<U *const *, T const *>::value>::type * = nullptr)
 121       : Data(Vec.data()), Length(Vec.size()) {
 122     }
 123
 124     /// Construct an ArrayRef<const T*> from std::vector<T*>. This uses SFINAE
 125     /// to ensure that only vectors of pointers can be converted.
 126     template<typename U, typename A>
 127     ArrayRef(const std::vector<U *, A> &Vec,
 128              typename std::enable_if<
 129                  std::is_convertible<U *const *, T const *>::value>::type* = 0)
 130       : Data(Vec.data()), Length(Vec.size()) {}
 131
 132     /// @}
 133     /// @name Simple Operations
 134     /// @{
 135
 136     iterator begin() const { return Data; }
 137     iterator end() const { return Data + Length; }
 138
 139     reverse_iterator rbegin() const { return reverse_iterator(end()); }
 140     reverse_iterator rend() const { return reverse_iterator(begin()); }
 141
 142     /// empty - Check if the array is empty.
 143     bool empty() const { return Length == 0; }
 144
 145     const T *data() const { return Data; }
 146
 147     /// size - Get the array size.
 148     size_t size() const { return Length; }
 149
 150     /// front - Get the first element.
 151     const T &front() const {
 152       assert(!empty());
 153       return Data[0];
 154     }
 155
 156     /// back - Get the last element.
 157     const T &back() const {
 158       assert(!empty());
 159       return Data[Length-1];
 160     }
 161
 162     // copy - Allocate copy in Allocator and return ArrayRef<T> to it.
 163     template <typename Allocator> ArrayRef<T> copy(Allocator &A) {
 164       T *Buff = A.template Allocate<T>(Length);
 165       std::uninitialized_copy(begin(), end(), Buff);
 166       return ArrayRef<T>(Buff, Length);
 167     }
 168
 169     /// equals - Check for element-wise equality.
 170     bool equals(ArrayRef RHS) const {
 171       if (Length != RHS.Length)
 172         return false;
 173       return std::equal(begin(), end(), RHS.begin());
 174     }
 175
 176     /// slice(n, m) - Chop off the first N elements of the array, and keep M
 177     /// elements in the array.
 178     ArrayRef<T> slice(size_t N, size_t M) const {
 179       assert(N+M <= size() && "Invalid specifier");
 180       return ArrayRef<T>(data()+N, M);
 181     }
 182
 183     /// slice(n) - Chop off the first N elements of the array.
 184     ArrayRef<T> slice(size_t N) const { return slice(N, size() - N); }
 185
 186     /// Drop the first \p N elements of the array.
 187     ArrayRef<T> drop_front(size_t N = 1) const {
 188       assert(size() >= N && "Dropping more elements than exist");
 189       return slice(N, size() - N);
 190     }
 191
 192     /// Drop the last \p N elements of the array.
 193     ArrayRef<T> drop_back(size_t N = 1) const {
 194       assert(size() >= N && "Dropping more elements than exist");
 195       return slice(0, size() - N);
 196     }
 197
 198     /// Return a copy of *this with the first N elements satisfying the
 199     /// given predicate removed.
 200     template <class PredicateT> ArrayRef<T> drop_while(PredicateT Pred) const {
 201       return ArrayRef<T>(find_if_not(*this, Pred), end());
 202     }
 203
 204     /// Return a copy of *this with the first N elements not satisfying
 205     /// the given predicate removed.
 206     template <class PredicateT> ArrayRef<T> drop_until(PredicateT Pred) const {
 207       return ArrayRef<T>(find_if(*this, Pred), end());
 208     }
 209
 210     /// Return a copy of *this with only the first \p N elements.
 211     ArrayRef<T> take_front(size_t N = 1) const {
 212       if (N >= size())
 213         return *this;
 214       return drop_back(size() - N);
 215     }
 216
 217     /// Return a copy of *this with only the last \p N elements.
 218     ArrayRef<T> take_back(size_t N = 1) const {
 219       if (N >= size())
 220         return *this;
 221       return drop_front(size() - N);
 222     }
 223
 224     /// Return the first N elements of this Array that satisfy the given
 225     /// predicate.
 226     template <class PredicateT> ArrayRef<T> take_while(PredicateT Pred) const {
 227       return ArrayRef<T>(begin(), find_if_not(*this, Pred));
 228     }
 229
 230     /// Return the first N elements of this Array that don't satisfy the
 231     /// given predicate.
 232     template <class PredicateT> ArrayRef<T> take_until(PredicateT Pred) const {
 233       return ArrayRef<T>(begin(), find_if(*this, Pred));
 234     }
 235
 236     /// @}
 237     /// @name Operator Overloads
 238     /// @{
 239     const T &operator[](size_t Index) const {
 240       assert(Index < Length && "Invalid index!");
 241       return Data[Index];
 242     }
 243
 244     /// Disallow accidental assignment from a temporary.
 245     ///
 246     /// The declaration here is extra complicated so that "arrayRef = {}"
 247     /// continues to select the move assignment operator.
 248     template <typename U>
 249     typename std::enable_if<std::is_same<U, T>::value, ArrayRef<T>>::type &
 250     operator=(U &&Temporary) = delete;
 251
 252     /// Disallow accidental assignment from a temporary.
 253     ///
 254     /// The declaration here is extra complicated so that "arrayRef = {}"
 255     /// continues to select the move assignment operator.
 256     template <typename U>
 257     typename std::enable_if<std::is_same<U, T>::value, ArrayRef<T>>::type &
 258     operator=(std::initializer_list<U>) = delete;
 259
 260     /// @}
 261     /// @name Expensive Operations
 262     /// @{
 263     std::vector<T> vec() const {
 264       return std::vector<T>(Data, Data+Length);
 265     }
 266
 267     /// @}
 268     /// @name Conversion operators
 269     /// @{
 270     operator std::vector<T>() const {
 271       return std::vector<T>(Data, Data+Length);
 272     }
 273
 274     /// @}
 275   };
 276
 277   /// MutableArrayRef - Represent a mutable reference to an array (0 or more
 278   /// elements consecutively in memory), i.e. a start pointer and a length.  It
 279   /// allows various APIs to take and modify consecutive elements easily and
 280   /// conveniently.
 281   ///
 282   /// This class does not own the underlying data, it is expected to be used in
 283   /// situations where the data resides in some other buffer, whose lifetime
 284   /// extends past that of the MutableArrayRef. For this reason, it is not in
 285   /// general safe to store a MutableArrayRef.
 286   ///
 287   /// This is intended to be trivially copyable, so it should be passed by
 288   /// value.
 289   template<typename T>
 290   class LLVM_NODISCARD MutableArrayRef : public ArrayRef<T> {
 291   public:
 292     using iterator = T *;
 293     using reverse_iterator = std::reverse_iterator<iterator>;
 294
 295     /// Construct an empty MutableArrayRef.
 296     /*implicit*/ MutableArrayRef() = default;
 297
 298     /// Construct an empty MutableArrayRef from None.
 299     /*implicit*/ MutableArrayRef(NoneType) : ArrayRef<T>() {}
 300
 301     /// Construct an MutableArrayRef from a single element.
 302     /*implicit*/ MutableArrayRef(T &OneElt) : ArrayRef<T>(OneElt) {}
 303
 304     /// Construct an MutableArrayRef from a pointer and length.
 305     /*implicit*/ MutableArrayRef(T *data, size_t length)
 306       : ArrayRef<T>(data, length) {}
 307
 308     /// Construct an MutableArrayRef from a range.
 309     MutableArrayRef(T *begin, T *end) : ArrayRef<T>(begin, end) {}
 310
 311     /// Construct an MutableArrayRef from a SmallVector.
 312     /*implicit*/ MutableArrayRef(SmallVectorImpl<T> &Vec)
 313     : ArrayRef<T>(Vec) {}
 314
 315     /// Construct a MutableArrayRef from a std::vector.
 316     /*implicit*/ MutableArrayRef(std::vector<T> &Vec)
 317     : ArrayRef<T>(Vec) {}
 318
 319     /// Construct an ArrayRef from a std::array
 320     template <size_t N>
 321     /*implicit*/ constexpr MutableArrayRef(std::array<T, N> &Arr)
 322         : ArrayRef<T>(Arr) {}
 323
 324     /// Construct an MutableArrayRef from a C array.
 325     template <size_t N>
 326     /*implicit*/ constexpr MutableArrayRef(T (&Arr)[N]) : ArrayRef<T>(Arr) {}
 327
 328     T *data() const { return const_cast<T*>(ArrayRef<T>::data()); }
 329
 330     iterator begin() const { return data(); }
 331     iterator end() const { return data() + this->size(); }
 332
 333     reverse_iterator rbegin() const { return reverse_iterator(end()); }
 334     reverse_iterator rend() const { return reverse_iterator(begin()); }
 335
 336     /// front - Get the first element.
 337     T &front() const {
 338       assert(!this->empty());
 339       return data()[0];
 340     }
 341
 342     /// back - Get the last element.
 343     T &back() const {
 344       assert(!this->empty());
 345       return data()[this->size()-1];
 346     }
 347
 348     /// slice(n, m) - Chop off the first N elements of the array, and keep M
 349     /// elements in the array.
 350     MutableArrayRef<T> slice(size_t N, size_t M) const {
 351       assert(N + M <= this->size() && "Invalid specifier");
 352       return MutableArrayRef<T>(this->data() + N, M);
 353     }
 354
 355     /// slice(n) - Chop off the first N elements of the array.
 356     MutableArrayRef<T> slice(size_t N) const {
 357       return slice(N, this->size() - N);
 358     }
 359
 360     /// Drop the first \p N elements of the array.
 361     MutableArrayRef<T> drop_front(size_t N = 1) const {
 362       assert(this->size() >= N && "Dropping more elements than exist");
 363       return slice(N, this->size() - N);
 364     }
 365
 366     MutableArrayRef<T> drop_back(size_t N = 1) const {
 367       assert(this->size() >= N && "Dropping more elements than exist");
 368       return slice(0, this->size() - N);
 369     }
 370
 371     /// Return a copy of *this with the first N elements satisfying the
 372     /// given predicate removed.
 373     template <class PredicateT>
 374     MutableArrayRef<T> drop_while(PredicateT Pred) const {
 375       return MutableArrayRef<T>(find_if_not(*this, Pred), end());
 376     }
 377
 378     /// Return a copy of *this with the first N elements not satisfying
 379     /// the given predicate removed.
 380     template <class PredicateT>
 381     MutableArrayRef<T> drop_until(PredicateT Pred) const {
 382       return MutableArrayRef<T>(find_if(*this, Pred), end());
 383     }
 384
 385     /// Return a copy of *this with only the first \p N elements.
 386     MutableArrayRef<T> take_front(size_t N = 1) const {
 387       if (N >= this->size())
 388         return *this;
 389       return drop_back(this->size() - N);
 390     }
 391
 392     /// Return a copy of *this with only the last \p N elements.
 393     MutableArrayRef<T> take_back(size_t N = 1) const {
 394       if (N >= this->size())
 395         return *this;
 396       return drop_front(this->size() - N);
 397     }
 398
 399     /// Return the first N elements of this Array that satisfy the given
 400     /// predicate.
 401     template <class PredicateT>
 402     MutableArrayRef<T> take_while(PredicateT Pred) const {
 403       return MutableArrayRef<T>(begin(), find_if_not(*this, Pred));
 404     }
 405
 406     /// Return the first N elements of this Array that don't satisfy the
 407     /// given predicate.
 408     template <class PredicateT>
 409     MutableArrayRef<T> take_until(PredicateT Pred) const {
 410       return MutableArrayRef<T>(begin(), find_if(*this, Pred));
 411     }
 412
 413     /// @}
 414     /// @name Operator Overloads
 415     /// @{
 416     T &operator[](size_t Index) const {
 417       assert(Index < this->size() && "Invalid index!");
 418       return data()[Index];
 419     }
 420   };
 421
 422   /// This is a MutableArrayRef that owns its array.
 423   template <typename T> class OwningArrayRef : public MutableArrayRef<T> {
 424   public:
 425     OwningArrayRef() = default;
 426     OwningArrayRef(size_t Size) : MutableArrayRef<T>(new T[Size], Size) {}
 427
 428     OwningArrayRef(ArrayRef<T> Data)
 429         : MutableArrayRef<T>(new T[Data.size()], Data.size()) {
 430       std::copy(Data.begin(), Data.end(), this->begin());
 431     }
 432
 433     OwningArrayRef(OwningArrayRef &&Other) { *this = std::move(Other); }
 434
 435     OwningArrayRef &operator=(OwningArrayRef &&Other) {
 436       delete[] this->data();
 437       this->MutableArrayRef<T>::operator=(Other);
 438       Other.MutableArrayRef<T>::operator=(MutableArrayRef<T>());
 439       return *this;
 440     }
 441
 442     ~OwningArrayRef() { delete[] this->data(); }
 443   };
 444
 445   /// @name ArrayRef Convenience constructors
 446   /// @{
 447
 448   /// Construct an ArrayRef from a single element.
 449   template<typename T>
 450   ArrayRef<T> makeArrayRef(const T &OneElt) {
 451     return OneElt;
 452   }
 453
 454   /// Construct an ArrayRef from a pointer and length.
 455   template<typename T>
 456   ArrayRef<T> makeArrayRef(const T *data, size_t length) {
 457     return ArrayRef<T>(data, length);
 458   }
 459
 460   /// Construct an ArrayRef from a range.
 461   template<typename T>
 462   ArrayRef<T> makeArrayRef(const T *begin, const T *end) {
 463     return ArrayRef<T>(begin, end);
 464   }
 465
 466   /// Construct an ArrayRef from a SmallVector.
 467   template <typename T>
 468   ArrayRef<T> makeArrayRef(const SmallVectorImpl<T> &Vec) {
 469     return Vec;
 470   }
 471
 472   /// Construct an ArrayRef from a SmallVector.
 473   template <typename T, unsigned N>
 474   ArrayRef<T> makeArrayRef(const SmallVector<T, N> &Vec) {
 475     return Vec;
 476   }
 477
 478   /// Construct an ArrayRef from a std::vector.
 479   template<typename T>
 480   ArrayRef<T> makeArrayRef(const std::vector<T> &Vec) {
 481     return Vec;
 482   }
 483
 484   /// Construct an ArrayRef from a std::array.
 485   template <typename T, std::size_t N>
 486   ArrayRef<T> makeArrayRef(const std::array<T, N> &Arr) {
 487     return Arr;
 488   }
 489
 490   /// Construct an ArrayRef from an ArrayRef (no-op) (const)
 491   template <typename T> ArrayRef<T> makeArrayRef(const ArrayRef<T> &Vec) {
 492     return Vec;
 493   }
 494
 495   /// Construct an ArrayRef from an ArrayRef (no-op)
 496   template <typename T> ArrayRef<T> &makeArrayRef(ArrayRef<T> &Vec) {
 497     return Vec;
 498   }
 499
 500   /// Construct an ArrayRef from a C array.
 501   template<typename T, size_t N>
 502   ArrayRef<T> makeArrayRef(const T (&Arr)[N]) {
 503     return ArrayRef<T>(Arr);
 504   }
 505
 506   /// Construct a MutableArrayRef from a single element.
 507   template<typename T>
 508   MutableArrayRef<T> makeMutableArrayRef(T &OneElt) {
 509     return OneElt;
 510   }
 511
 512   /// Construct a MutableArrayRef from a pointer and length.
 513   template<typename T>
 514   MutableArrayRef<T> makeMutableArrayRef(T *data, size_t length) {
 515     return MutableArrayRef<T>(data, length);
 516   }
 517
 518   /// @}
 519   /// @name ArrayRef Comparison Operators
 520   /// @{
 521
 522   template<typename T>
 523   inline bool operator==(ArrayRef<T> LHS, ArrayRef<T> RHS) {
 524     return LHS.equals(RHS);
 525   }
 526
 527   template<typename T>
 528   inline bool operator!=(ArrayRef<T> LHS, ArrayRef<T> RHS) {
 529     return !(LHS == RHS);
 530   }
 531
 532   /// @}
 533
 534   template <typename T> hash_code hash_value(ArrayRef<T> S) {
 535     return hash_combine_range(S.begin(), S.end());
 536   }
 537
 538 } // end namespace llvm
 539
 540 #endif // LLVM_ADT_ARRAYREF_H