//===--- ArrayRef.h - Array Reference Wrapper -------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// ATen: modified from llvm::ArrayRef.
// removed llvm-specific functionality
// removed some implicit const -> non-const conversions that rely on
// complicated std::enable_if meta-programming
// removed a bunch of slice variants for simplicity...
#pragma once
#include <c10/macros/Macros.h>
#include <c10/util/Deprecated.h>
#include <c10/util/Exception.h>
#include <c10/util/SmallVector.h>
#include <array>
#include <cstddef>
#include <cstdint>
#include <initializer_list>
#include <iterator>
#include <ostream>
#include <type_traits>
#include <vector>
namespace c10 {
/// ArrayRef - Represent a constant reference to an array (0 or more elements
/// consecutively in memory), i.e. a start pointer and a length. It allows
/// various APIs to take consecutive elements easily and conveniently.
///
/// This class does not own the underlying data, it is expected to be used in
/// situations where the data resides in some other buffer, whose lifetime
/// extends past that of the ArrayRef. For this reason, it is not in general
/// safe to store an ArrayRef.
///
/// This is intended to be trivially copyable, so it should be passed by
/// value.
template <typename T>
class ArrayRef final {
public:
using iterator = const T*;
using const_iterator = const T*;
using size_type = size_t;
using value_type = T;
using reverse_iterator = std::reverse_iterator<iterator>;
private:
/// The start of the array, in an external buffer.
const T* Data;
/// The number of elements.
size_type Length;
void debugCheckNullptrInvariant() {
TORCH_INTERNAL_ASSERT_DEBUG_ONLY(
Data != nullptr || Length == 0,
"created ArrayRef with nullptr and non-zero length! std::optional relies on this being illegal");
}
public:
/// @name Constructors
/// @{
/// Construct an empty ArrayRef.
/* implicit */ constexpr ArrayRef() : Data(nullptr), Length(0) {}
/// Construct an ArrayRef from a single element.
// TODO Make this explicit
constexpr ArrayRef(const T& OneElt) : Data(&OneElt), Length(1) {}
/// Construct an ArrayRef from a pointer and length.
C10_HOST_CONSTEXPR_EXCEPT_WIN_CUDA ArrayRef(const T* data, size_t length)
: Data(data), Length(length) {
debugCheckNullptrInvariant();
}
/// Construct an ArrayRef from a range.
C10_HOST_CONSTEXPR_EXCEPT_WIN_CUDA ArrayRef(const T* begin, const T* end)
: Data(begin), Length(end - begin) {
debugCheckNullptrInvariant();
}
/// Construct an ArrayRef from a SmallVector. This is templated in order to
/// avoid instantiating SmallVectorTemplateCommon<T> whenever we
/// copy-construct an ArrayRef.
template <typename U>
/* implicit */ ArrayRef(const SmallVectorTemplateCommon<T, U>& Vec)
: Data(Vec.data()), Length(Vec.size()) {
debugCheckNullptrInvariant();
}
template <
typename Container,
typename = std::enable_if_t<std::is_same_v<
std::remove_const_t<decltype(std::declval<Container>().data())>,
T*>>>
/* implicit */ ArrayRef(const Container& container)
: Data(container.data()), Length(container.size()) {
debugCheckNullptrInvariant();
}
/// Construct an ArrayRef from a std::vector.
// The enable_if stuff here makes sure that this isn't used for
// std::vector<bool>, because ArrayRef can't work on a std::vector<bool>
// bitfield.
template <typename A>
/* implicit */ ArrayRef(const std::vector<T, A>& Vec)
: Data(Vec.data()), Length(Vec.size()) {
static_assert(
!std::is_same<T, bool>::value,
"ArrayRef<bool> cannot be constructed from a std::vector<bool> bitfield.");
}
/// Construct an ArrayRef from a std::array
template <size_t N>
/* implicit */ constexpr ArrayRef(const std::array<T, N>& Arr)
: Data(Arr.data()), Length(N) {}
/// Construct an ArrayRef from a C array.
template <size_t N>
// NOLINTNEXTLINE(*c-arrays*)
/* implicit */ constexpr ArrayRef(const T (&Arr)[N]) : Data(Arr), Length(N) {}
/// Construct an ArrayRef from a std::initializer_list.
/* implicit */ constexpr ArrayRef(const std::initializer_list<T>& Vec)
: Data(
std::begin(Vec) == std::end(Vec) ? static_cast<T*>(nullptr)
: std::begin(Vec)),
Length(Vec.size()) {}
/// @}
/// @name Simple Operations
/// @{
constexpr iterator begin() const {
return Data;
}
constexpr iterator end() const {
return Data + Length;
}
// These are actually the same as iterator, since ArrayRef only
// gives you const iterators.
constexpr const_iterator cbegin() const {
return Data;
}
constexpr const_iterator cend() const {
return Data + Length;
}
constexpr reverse_iterator rbegin() const {
return reverse_iterator(end());
}
constexpr reverse_iterator rend() const {
return reverse_iterator(begin());
}
/// empty - Check if the array is empty.
constexpr bool empty() const {
return Length == 0;
}
constexpr const T* data() const {
return Data;
}
/// size - Get the array size.
constexpr size_t size() const {
return Length;
}
/// front - Get the first element.
C10_HOST_CONSTEXPR_EXCEPT_WIN_CUDA const T& front() const {
TORCH_CHECK(
!empty(), "ArrayRef: attempted to access front() of empty list");
return Data[0];
}
/// back - Get the last element.
C10_HOST_CONSTEXPR_EXCEPT_WIN_CUDA const T& back() const {
TORCH_CHECK(!empty(), "ArrayRef: attempted to access back() of empty list");
return Data[Length - 1];
}
/// equals - Check for element-wise equality.
constexpr bool equals(ArrayRef RHS) const {
return Length == RHS.Length && std::equal(begin(), end(), RHS.begin());
}
/// slice(n, m) - Take M elements of the array starting at element N
C10_HOST_CONSTEXPR_EXCEPT_WIN_CUDA ArrayRef<T> slice(size_t N, size_t M)
const {
TORCH_CHECK(
N + M <= size(),
"ArrayRef: invalid slice, N = ",
N,
"; M = ",
M,
"; size = ",
size());
return ArrayRef<T>(data() + N, M);
}
/// slice(n) - Chop off the first N elements of the array.
C10_HOST_CONSTEXPR_EXCEPT_WIN_CUDA ArrayRef<T> slice(size_t N) const {
TORCH_CHECK(
N <= size(), "ArrayRef: invalid slice, N = ", N, "; size = ", size());
return slice(N, size() - N);
}
/// @}
/// @name Operator Overloads
/// @{
constexpr const T& operator[](size_t Index) const {
return Data[Index];
}
/// Vector compatibility
C10_HOST_CONSTEXPR_EXCEPT_WIN_CUDA const T& at(size_t Index) const {
TORCH_CHECK(
Index < Length,
"ArrayRef: invalid index Index = ",
Index,
"; Length = ",
Length);
return Data[Index];
}
/// Disallow accidental assignment from a temporary.
///
/// The declaration here is extra complicated so that "arrayRef = {}"
/// continues to select the move assignment operator.
template <typename U>
std::enable_if_t<std::is_same_v<U, T>, ArrayRef<T>>& operator=(
// NOLINTNEXTLINE(cppcoreguidelines-missing-std-forward)
U&& Temporary) = delete;
/// Disallow accidental assignment from a temporary.
///
/// The declaration here is extra complicated so that "arrayRef = {}"
/// continues to select the move assignment operator.
template <typename U>
std::enable_if_t<std::is_same_v<U, T>, ArrayRef<T>>& operator=(
std::initializer_list<U>) = delete;
/// @}
/// @name Expensive Operations
/// @{
std::vector<T> vec() const {
return std::vector<T>(Data, Data + Length);
}
/// @}
};
template <typename T>
std::ostream& operator<<(std::ostream& out, ArrayRef<T> list) {
int i = 0;
out << "[";
for (const auto& e : list) {
if (i++ > 0)
out << ", ";
out << e;
}
out << "]";
return out;
}
/// @name ArrayRef Convenience constructors
/// @{
/// Construct an ArrayRef from a single element.
template <typename T>
ArrayRef<T> makeArrayRef(const T& OneElt) {
return OneElt;
}
/// Construct an ArrayRef from a pointer and length.
template <typename T>
ArrayRef<T> makeArrayRef(const T* data, size_t length) {
return ArrayRef<T>(data, length);
}
/// Construct an ArrayRef from a range.
template <typename T>
ArrayRef<T> makeArrayRef(const T* begin, const T* end) {
return ArrayRef<T>(begin, end);
}
/// Construct an ArrayRef from a SmallVector.
template <typename T>
ArrayRef<T> makeArrayRef(const SmallVectorImpl<T>& Vec) {
return Vec;
}
/// Construct an ArrayRef from a SmallVector.
template <typename T, unsigned N>
ArrayRef<T> makeArrayRef(const SmallVector<T, N>& Vec) {
return Vec;
}
/// Construct an ArrayRef from a std::vector.
template <typename T>
ArrayRef<T> makeArrayRef(const std::vector<T>& Vec) {
return Vec;
}
/// Construct an ArrayRef from a std::array.
template <typename T, std::size_t N>
ArrayRef<T> makeArrayRef(const std::array<T, N>& Arr) {
return Arr;
}
/// Construct an ArrayRef from an ArrayRef (no-op) (const)
template <typename T>
ArrayRef<T> makeArrayRef(const ArrayRef<T>& Vec) {
return Vec;
}
/// Construct an ArrayRef from an ArrayRef (no-op)
template <typename T>
ArrayRef<T>& makeArrayRef(ArrayRef<T>& Vec) {
return Vec;
}
/// Construct an ArrayRef from a C array.
template <typename T, size_t N>
// NOLINTNEXTLINE(*c-arrays*)
ArrayRef<T> makeArrayRef(const T (&Arr)[N]) {
return ArrayRef<T>(Arr);
}
// WARNING: Template instantiation will NOT be willing to do an implicit
// conversions to get you to an c10::ArrayRef, which is why we need so
// many overloads.
template <typename T>
bool operator==(c10::ArrayRef<T> a1, c10::ArrayRef<T> a2) {
return a1.equals(a2);
}
template <typename T>
bool operator!=(c10::ArrayRef<T> a1, c10::ArrayRef<T> a2) {
return !a1.equals(a2);
}
template <typename T>
bool operator==(const std::vector<T>& a1, c10::ArrayRef<T> a2) {
return c10::ArrayRef<T>(a1).equals(a2);
}
template <typename T>
bool operator!=(const std::vector<T>& a1, c10::ArrayRef<T> a2) {
return !c10::ArrayRef<T>(a1).equals(a2);
}
template <typename T>
bool operator==(c10::ArrayRef<T> a1, const std::vector<T>& a2) {
return a1.equals(c10::ArrayRef<T>(a2));
}
template <typename T>
bool operator!=(c10::ArrayRef<T> a1, const std::vector<T>& a2) {
return !a1.equals(c10::ArrayRef<T>(a2));
}
using IntArrayRef = ArrayRef<int64_t>;
// This alias is deprecated because it doesn't make ownership
// semantics obvious. Use IntArrayRef instead!
C10_DEFINE_DEPRECATED_USING(IntList, ArrayRef<int64_t>)
} // namespace c10