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1 : //===--- ArrayRef.h - Array Reference Wrapper -------------------*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 :
10 : // ATen: modified from llvm::ArrayRef.
11 : // removed llvm-specific functionality
12 : // removed some implicit const -> non-const conversions that rely on
13 : // complicated std::enable_if meta-programming
14 : // removed a bunch of slice variants for simplicity...
15 :
16 : #pragma once
17 :
18 : #include <c10/macros/Macros.h>
19 : #include <c10/util/Deprecated.h>
20 : #include <c10/util/Exception.h>
21 : #include <c10/util/SmallVector.h>
22 :
23 : #include <array>
24 : #include <cstddef>
25 : #include <cstdint>
26 : #include <initializer_list>
27 : #include <iterator>
28 : #include <ostream>
29 : #include <type_traits>
30 : #include <vector>
31 :
32 : namespace c10 {
33 : /// ArrayRef - Represent a constant reference to an array (0 or more elements
34 : /// consecutively in memory), i.e. a start pointer and a length. It allows
35 : /// various APIs to take consecutive elements easily and conveniently.
36 : ///
37 : /// This class does not own the underlying data, it is expected to be used in
38 : /// situations where the data resides in some other buffer, whose lifetime
39 : /// extends past that of the ArrayRef. For this reason, it is not in general
40 : /// safe to store an ArrayRef.
41 : ///
42 : /// This is intended to be trivially copyable, so it should be passed by
43 : /// value.
44 : template <typename T>
45 : class ArrayRef final {
46 : public:
47 : using iterator = const T*;
48 : using const_iterator = const T*;
49 : using size_type = size_t;
50 : using value_type = T;
51 :
52 : using reverse_iterator = std::reverse_iterator<iterator>;
53 :
54 : private:
55 : /// The start of the array, in an external buffer.
56 : const T* Data;
57 :
58 : /// The number of elements.
59 : size_type Length;
60 :
61 : void debugCheckNullptrInvariant() {
62 : TORCH_INTERNAL_ASSERT_DEBUG_ONLY(
63 : Data != nullptr || Length == 0,
64 : "created ArrayRef with nullptr and non-zero length! std::optional relies on this being illegal");
65 : }
66 :
67 : public:
68 : /// @name Constructors
69 : /// @{
70 :
71 : /// Construct an empty ArrayRef.
72 7 : /* implicit */ constexpr ArrayRef() : Data(nullptr), Length(0) {}
73 :
74 : /// Construct an ArrayRef from a single element.
75 : // TODO Make this explicit
76 : constexpr ArrayRef(const T& OneElt) : Data(&OneElt), Length(1) {}
77 :
78 : /// Construct an ArrayRef from a pointer and length.
79 : constexpr ArrayRef(const T* data, size_t length)
80 : : Data(data), Length(length) {
81 : debugCheckNullptrInvariant();
82 : }
83 :
84 : /// Construct an ArrayRef from a range.
85 : constexpr ArrayRef(const T* begin, const T* end)
86 : : Data(begin), Length(end - begin) {
87 : debugCheckNullptrInvariant();
88 : }
89 :
90 : /// Construct an ArrayRef from a SmallVector. This is templated in order to
91 : /// avoid instantiating SmallVectorTemplateCommon<T> whenever we
92 : /// copy-construct an ArrayRef.
93 : template <typename U>
94 : /* implicit */ ArrayRef(const SmallVectorTemplateCommon<T, U>& Vec)
95 : : Data(Vec.data()), Length(Vec.size()) {
96 : debugCheckNullptrInvariant();
97 : }
98 :
99 : template <
100 : typename Container,
101 : typename U = decltype(std::declval<Container>().data()),
102 : typename = std::enable_if_t<
103 : (std::is_same_v<U, T*> || std::is_same_v<U, T const*>)>>
104 : /* implicit */ ArrayRef(const Container& container)
105 : : Data(container.data()), Length(container.size()) {
106 : debugCheckNullptrInvariant();
107 : }
108 :
109 : /// Construct an ArrayRef from a std::vector.
110 : // The enable_if stuff here makes sure that this isn't used for
111 : // std::vector<bool>, because ArrayRef can't work on a std::vector<bool>
112 : // bitfield.
113 : template <typename A>
114 78 : /* implicit */ ArrayRef(const std::vector<T, A>& Vec)
115 78 : : Data(Vec.data()), Length(Vec.size()) {
116 : static_assert(
117 : !std::is_same_v<T, bool>,
118 : "ArrayRef<bool> cannot be constructed from a std::vector<bool> bitfield.");
119 : }
120 :
121 : /// Construct an ArrayRef from a std::array
122 : template <size_t N>
123 : /* implicit */ constexpr ArrayRef(const std::array<T, N>& Arr)
124 : : Data(Arr.data()), Length(N) {}
125 :
126 : /// Construct an ArrayRef from a C array.
127 : template <size_t N>
128 : // NOLINTNEXTLINE(*c-arrays*)
129 : /* implicit */ constexpr ArrayRef(const T (&Arr)[N]) : Data(Arr), Length(N) {}
130 :
131 : /// Construct an ArrayRef from a std::initializer_list.
132 264 : /* implicit */ constexpr ArrayRef(const std::initializer_list<T>& Vec)
133 264 : : Data(
134 : std::begin(Vec) == std::end(Vec) ? static_cast<T*>(nullptr)
135 : : std::begin(Vec)),
136 188 : Length(Vec.size()) {}
137 :
138 : /// @}
139 : /// @name Simple Operations
140 : /// @{
141 :
142 : constexpr iterator begin() const {
143 : return Data;
144 : }
145 : constexpr iterator end() const {
146 264 : return Data + Length;
147 : }
148 :
149 : // These are actually the same as iterator, since ArrayRef only
150 : // gives you const iterators.
151 : constexpr const_iterator cbegin() const {
152 : return Data;
153 : }
154 : constexpr const_iterator cend() const {
155 : return Data + Length;
156 : }
157 :
158 : constexpr reverse_iterator rbegin() const {
159 : return reverse_iterator(end());
160 : }
161 : constexpr reverse_iterator rend() const {
162 : return reverse_iterator(begin());
163 : }
164 :
165 : /// Check if all elements in the array satisfy the given expression
166 : constexpr bool allMatch(const std::function<bool(const T&)>& pred) const {
167 : return std::all_of(cbegin(), cend(), pred);
168 : }
169 :
170 : /// empty - Check if the array is empty.
171 : constexpr bool empty() const {
172 : return Length == 0;
173 : }
174 :
175 : constexpr const T* data() const {
176 : return Data;
177 : }
178 :
179 : /// size - Get the array size.
180 : constexpr size_t size() const {
181 55 : return Length;
182 : }
183 :
184 : /// front - Get the first element.
185 : constexpr const T& front() const {
186 : TORCH_CHECK(
187 : !empty(), "ArrayRef: attempted to access front() of empty list");
188 : return Data[0];
189 : }
190 :
191 : /// back - Get the last element.
192 : constexpr const T& back() const {
193 : TORCH_CHECK(!empty(), "ArrayRef: attempted to access back() of empty list");
194 : return Data[Length - 1];
195 : }
196 :
197 : /// equals - Check for element-wise equality.
198 : constexpr bool equals(ArrayRef RHS) const {
199 : return Length == RHS.Length && std::equal(begin(), end(), RHS.begin());
200 : }
201 :
202 : /// slice(n, m) - Take M elements of the array starting at element N
203 : constexpr ArrayRef<T> slice(size_t N, size_t M) const {
204 : TORCH_CHECK(
205 : N + M <= size(),
206 : "ArrayRef: invalid slice, N = ",
207 : N,
208 : "; M = ",
209 : M,
210 : "; size = ",
211 : size());
212 : return ArrayRef<T>(data() + N, M);
213 : }
214 :
215 : /// slice(n) - Chop off the first N elements of the array.
216 : constexpr ArrayRef<T> slice(size_t N) const {
217 : TORCH_CHECK(
218 : N <= size(), "ArrayRef: invalid slice, N = ", N, "; size = ", size());
219 : return slice(N, size() - N);
220 : }
221 :
222 : /// @}
223 : /// @name Operator Overloads
224 : /// @{
225 : constexpr const T& operator[](size_t Index) const {
226 : return Data[Index];
227 : }
228 :
229 : /// Vector compatibility
230 : constexpr const T& at(size_t Index) const {
231 : TORCH_CHECK(
232 : Index < Length,
233 : "ArrayRef: invalid index Index = ",
234 : Index,
235 : "; Length = ",
236 : Length);
237 : return Data[Index];
238 : }
239 :
240 : /// Disallow accidental assignment from a temporary.
241 : ///
242 : /// The declaration here is extra complicated so that "arrayRef = {}"
243 : /// continues to select the move assignment operator.
244 : template <typename U>
245 : std::enable_if_t<std::is_same_v<U, T>, ArrayRef<T>>& operator=(
246 : // NOLINTNEXTLINE(cppcoreguidelines-missing-std-forward)
247 : U&& Temporary) = delete;
248 :
249 : /// Disallow accidental assignment from a temporary.
250 : ///
251 : /// The declaration here is extra complicated so that "arrayRef = {}"
252 : /// continues to select the move assignment operator.
253 : template <typename U>
254 : std::enable_if_t<std::is_same_v<U, T>, ArrayRef<T>>& operator=(
255 : std::initializer_list<U>) = delete;
256 :
257 : /// @}
258 : /// @name Expensive Operations
259 : /// @{
260 : std::vector<T> vec() const {
261 : return std::vector<T>(Data, Data + Length);
262 : }
263 :
264 : /// @}
265 : };
266 :
267 : template <typename T>
268 : std::ostream& operator<<(std::ostream& out, ArrayRef<T> list) {
269 : int i = 0;
270 : out << "[";
271 : for (const auto& e : list) {
272 : if (i++ > 0)
273 : out << ", ";
274 : out << e;
275 : }
276 : out << "]";
277 : return out;
278 : }
279 :
280 : /// @name ArrayRef Convenience constructors
281 : /// @{
282 :
283 : /// Construct an ArrayRef from a single element.
284 : template <typename T>
285 : ArrayRef<T> makeArrayRef(const T& OneElt) {
286 : return OneElt;
287 : }
288 :
289 : /// Construct an ArrayRef from a pointer and length.
290 : template <typename T>
291 : ArrayRef<T> makeArrayRef(const T* data, size_t length) {
292 : return ArrayRef<T>(data, length);
293 : }
294 :
295 : /// Construct an ArrayRef from a range.
296 : template <typename T>
297 : ArrayRef<T> makeArrayRef(const T* begin, const T* end) {
298 : return ArrayRef<T>(begin, end);
299 : }
300 :
301 : /// Construct an ArrayRef from a SmallVector.
302 : template <typename T>
303 : ArrayRef<T> makeArrayRef(const SmallVectorImpl<T>& Vec) {
304 : return Vec;
305 : }
306 :
307 : /// Construct an ArrayRef from a SmallVector.
308 : template <typename T, unsigned N>
309 : ArrayRef<T> makeArrayRef(const SmallVector<T, N>& Vec) {
310 : return Vec;
311 : }
312 :
313 : /// Construct an ArrayRef from a std::vector.
314 : template <typename T>
315 : ArrayRef<T> makeArrayRef(const std::vector<T>& Vec) {
316 : return Vec;
317 : }
318 :
319 : /// Construct an ArrayRef from a std::array.
320 : template <typename T, std::size_t N>
321 : ArrayRef<T> makeArrayRef(const std::array<T, N>& Arr) {
322 : return Arr;
323 : }
324 :
325 : /// Construct an ArrayRef from an ArrayRef (no-op) (const)
326 : template <typename T>
327 : ArrayRef<T> makeArrayRef(const ArrayRef<T>& Vec) {
328 : return Vec;
329 : }
330 :
331 : /// Construct an ArrayRef from an ArrayRef (no-op)
332 : template <typename T>
333 : ArrayRef<T>& makeArrayRef(ArrayRef<T>& Vec) {
334 : return Vec;
335 : }
336 :
337 : /// Construct an ArrayRef from a C array.
338 : template <typename T, size_t N>
339 : // NOLINTNEXTLINE(*c-arrays*)
340 : ArrayRef<T> makeArrayRef(const T (&Arr)[N]) {
341 : return ArrayRef<T>(Arr);
342 : }
343 :
344 : // WARNING: Template instantiation will NOT be willing to do an implicit
345 : // conversions to get you to an c10::ArrayRef, which is why we need so
346 : // many overloads.
347 :
348 : template <typename T>
349 : bool operator==(c10::ArrayRef<T> a1, c10::ArrayRef<T> a2) {
350 : return a1.equals(a2);
351 : }
352 :
353 : template <typename T>
354 : bool operator!=(c10::ArrayRef<T> a1, c10::ArrayRef<T> a2) {
355 : return !a1.equals(a2);
356 : }
357 :
358 : template <typename T>
359 : bool operator==(const std::vector<T>& a1, c10::ArrayRef<T> a2) {
360 : return c10::ArrayRef<T>(a1).equals(a2);
361 : }
362 :
363 : template <typename T>
364 : bool operator!=(const std::vector<T>& a1, c10::ArrayRef<T> a2) {
365 : return !c10::ArrayRef<T>(a1).equals(a2);
366 : }
367 :
368 : template <typename T>
369 : bool operator==(c10::ArrayRef<T> a1, const std::vector<T>& a2) {
370 : return a1.equals(c10::ArrayRef<T>(a2));
371 : }
372 :
373 : template <typename T>
374 : bool operator!=(c10::ArrayRef<T> a1, const std::vector<T>& a2) {
375 : return !a1.equals(c10::ArrayRef<T>(a2));
376 : }
377 :
378 : using IntArrayRef = ArrayRef<int64_t>;
379 :
380 : // This alias is deprecated because it doesn't make ownership
381 : // semantics obvious. Use IntArrayRef instead!
382 : C10_DEFINE_DEPRECATED_USING(IntList, ArrayRef<int64_t>)
383 :
384 : } // namespace c10
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