#ifndef LLVM_ADT_ITERATOR_H
#define LLVM_ADT_ITERATOR_H
+#include <cstddef>
#include <iterator>
namespace llvm {
-/// \brief CRTP base class for adapting an iterator to a different type.
+/// \brief CRTP base class which implements the entire standard iterator facade
+/// in terms of a minimal subset of the interface.
///
-/// This class can be used through CRTP to adapt one iterator into another.
-/// Typically this is done through providing in the derived class a custom \c
-/// operator* implementation. Other methods can be overridden as well.
+/// Use this when it is reasonable to implement most of the iterator
+/// functionality in terms of a core subset. If you need special behavior or
+/// there are performance implications for this, you may want to override the
+/// relevant members instead.
///
-/// FIXME: Factor out the iterator-facade-like aspects into a base class that
-/// can be used for defining completely custom iterators.
-template <typename DerivedT, typename WrappedIteratorT, typename T,
- typename PointerT = T *, typename ReferenceT = T &,
- // Don't provide these, they are mostly to act as aliases below.
- typename WrappedTraitsT = std::iterator_traits<WrappedIteratorT>>
-class iterator_adaptor_base
- : public std::iterator<typename WrappedTraitsT::iterator_category, T,
- typename WrappedTraitsT::difference_type, PointerT,
+/// Note, one abstraction that this does *not* provide is implementing
+/// subtraction in terms of addition by negating the difference. Negation isn't
+/// always information preserving, and I can see very reasonable iterator
+/// designs where this doesn't work well. It doesn't really force much added
+/// boilerplate anyways.
+///
+/// Another abstraction that this doesn't provide is implementing increment in
+/// terms of addition of one. These aren't equivalent for all iterator
+/// categories, and respecting that adds a lot of complexity for little gain.
+template <typename DerivedT, typename IteratorCategoryT, typename T,
+ typename DifferenceTypeT = std::ptrdiff_t, typename PointerT = T *,
+ typename ReferenceT = T &>
+class iterator_facade_base
+ : public std::iterator<IteratorCategoryT, T, DifferenceTypeT, PointerT,
ReferenceT> {
protected:
- WrappedIteratorT I;
-
- iterator_adaptor_base() {}
-
- template <
- typename U,
- typename = typename std::enable_if<
- !std::is_same<typename std::remove_cv<
- typename std::remove_reference<U>::type>::type,
- DerivedT>::value>::type>
- explicit iterator_adaptor_base(U &&u)
- : I(std::forward<U &&>(u)) {}
+ enum {
+ IsRandomAccess =
+ std::is_base_of<std::random_access_iterator_tag, IteratorCategoryT>::value,
+ IsBidirectional =
+ std::is_base_of<std::bidirectional_iterator_tag, IteratorCategoryT>::value,
+ };
public:
- typedef typename iterator_adaptor_base::iterator::difference_type
- difference_type;
-
- DerivedT &operator+=(difference_type n) {
- I += n;
- return *static_cast<DerivedT *>(this);
- }
- DerivedT &operator-=(difference_type n) {
- I -= n;
- return *static_cast<DerivedT *>(this);
- }
- DerivedT operator+(difference_type n) const {
- DerivedT tmp = *this;
+ DerivedT operator+(DifferenceTypeT n) const {
+ static_assert(
+ IsRandomAccess,
+ "The '+' operator is only defined for random access iterators.");
+ DerivedT tmp = *static_cast<const DerivedT *>(this);
tmp += n;
return tmp;
}
- friend DerivedT operator+(difference_type n, const DerivedT &i) {
+ friend DerivedT operator+(DifferenceTypeT n, const DerivedT &i) {
+ static_assert(
+ IsRandomAccess,
+ "The '+' operator is only defined for random access iterators.");
return i + n;
}
- DerivedT operator-(difference_type n) const {
- DerivedT tmp = *this;
+ DerivedT operator-(DifferenceTypeT n) const {
+ static_assert(
+ IsRandomAccess,
+ "The '-' operator is only defined for random access iterators.");
+ DerivedT tmp = *static_cast<const DerivedT *>(this);
tmp -= n;
return tmp;
}
- difference_type operator-(const DerivedT &RHS) const { return I - RHS.I; }
DerivedT &operator++() {
- ++I;
- return *static_cast<DerivedT *>(this);
- }
- DerivedT &operator--() {
- --I;
- return *static_cast<DerivedT *>(this);
+ return static_cast<DerivedT *>(this)->operator+=(1);
}
DerivedT operator++(int) {
DerivedT tmp = *static_cast<DerivedT *>(this);
- ++*this;
+ ++*static_cast<DerivedT *>(this);
return tmp;
}
+ DerivedT &operator--() {
+ static_assert(
+ IsBidirectional,
+ "The decrement operator is only defined for bidirectional iterators.");
+ return static_cast<DerivedT *>(this)->operator-=(1);
+ }
DerivedT operator--(int) {
+ static_assert(
+ IsBidirectional,
+ "The decrement operator is only defined for bidirectional iterators.");
DerivedT tmp = *static_cast<DerivedT *>(this);
- --*this;
+ --*static_cast<DerivedT *>(this);
return tmp;
}
- bool operator==(const DerivedT &RHS) const { return I == RHS.I; }
bool operator!=(const DerivedT &RHS) const {
return !static_cast<const DerivedT *>(this)->operator==(RHS);
}
- bool operator<(const DerivedT &RHS) const { return I < RHS.I; }
bool operator>(const DerivedT &RHS) const {
+ static_assert(
+ IsRandomAccess,
+ "Relational operators are only defined for random access iterators.");
return !static_cast<const DerivedT *>(this)->operator<(RHS) &&
!static_cast<const DerivedT *>(this)->operator==(RHS);
}
bool operator<=(const DerivedT &RHS) const {
+ static_assert(
+ IsRandomAccess,
+ "Relational operators are only defined for random access iterators.");
return !static_cast<const DerivedT *>(this)->operator>(RHS);
}
bool operator>=(const DerivedT &RHS) const {
+ static_assert(
+ IsRandomAccess,
+ "Relational operators are only defined for random access iterators.");
return !static_cast<const DerivedT *>(this)->operator<(RHS);
}
- ReferenceT operator*() const { return *I; }
PointerT operator->() const {
- return static_cast<const DerivedT *>(this)->operator*();
+ return &static_cast<const DerivedT *>(this)->operator*();
}
- ReferenceT operator[](difference_type n) const {
+ ReferenceT operator[](DifferenceTypeT n) const {
+ static_assert(IsRandomAccess,
+ "Subscripting is only defined for random access iterators.");
return *static_cast<const DerivedT *>(this)->operator+(n);
}
};
+/// \brief CRTP base class for adapting an iterator to a different type.
+///
+/// This class can be used through CRTP to adapt one iterator into another.
+/// Typically this is done through providing in the derived class a custom \c
+/// operator* implementation. Other methods can be overridden as well.
+template <
+ typename DerivedT, typename WrappedIteratorT,
+ typename IteratorCategoryT =
+ typename std::iterator_traits<WrappedIteratorT>::iterator_category,
+ typename T = typename std::iterator_traits<WrappedIteratorT>::value_type,
+ typename DifferenceTypeT =
+ typename std::iterator_traits<WrappedIteratorT>::difference_type,
+ typename PointerT = T *, typename ReferenceT = T &,
+ // Don't provide these, they are mostly to act as aliases below.
+ typename WrappedTraitsT = std::iterator_traits<WrappedIteratorT>>
+class iterator_adaptor_base
+ : public iterator_facade_base<DerivedT, IteratorCategoryT, T,
+ DifferenceTypeT, PointerT, ReferenceT> {
+ typedef typename iterator_adaptor_base::iterator_facade_base BaseT;
+
+protected:
+ WrappedIteratorT I;
+
+ iterator_adaptor_base() = default;
+
+ template <typename U>
+ explicit iterator_adaptor_base(
+ U &&u,
+ typename std::enable_if<
+ !std::is_base_of<typename std::remove_cv<
+ typename std::remove_reference<U>::type>::type,
+ DerivedT>::value,
+ int>::type = 0)
+ : I(std::forward<U &&>(u)) {}
+
+public:
+ typedef DifferenceTypeT difference_type;
+
+ DerivedT &operator+=(difference_type n) {
+ static_assert(
+ BaseT::IsRandomAccess,
+ "The '+=' operator is only defined for random access iterators.");
+ I += n;
+ return *static_cast<DerivedT *>(this);
+ }
+ DerivedT &operator-=(difference_type n) {
+ static_assert(
+ BaseT::IsRandomAccess,
+ "The '-=' operator is only defined for random access iterators.");
+ I -= n;
+ return *static_cast<DerivedT *>(this);
+ }
+ using BaseT::operator-;
+ difference_type operator-(const DerivedT &RHS) const {
+ static_assert(
+ BaseT::IsRandomAccess,
+ "The '-' operator is only defined for random access iterators.");
+ return I - RHS.I;
+ }
+
+ // We have to explicitly provide ++ and -- rather than letting the facade
+ // forward to += because WrappedIteratorT might not support +=.
+ using BaseT::operator++;
+ DerivedT &operator++() {
+ ++I;
+ return *static_cast<DerivedT *>(this);
+ }
+ using BaseT::operator--;
+ DerivedT &operator--() {
+ static_assert(
+ BaseT::IsBidirectional,
+ "The decrement operator is only defined for bidirectional iterators.");
+ --I;
+ return *static_cast<DerivedT *>(this);
+ }
+
+ bool operator==(const DerivedT &RHS) const { return I == RHS.I; }
+ bool operator<(const DerivedT &RHS) const {
+ static_assert(
+ BaseT::IsRandomAccess,
+ "Relational operators are only defined for random access iterators.");
+ return I < RHS.I;
+ }
+
+ ReferenceT operator*() const { return *I; }
+};
+
/// \brief An iterator type that allows iterating over the pointees via some
/// other iterator.
///
/// \code
/// typedef pointee_iterator<SmallVectorImpl<T *>::iterator> iterator;
/// \endcode
-template <
- typename WrappedIteratorT,
- typename T = typename std::remove_pointer<
- typename std::iterator_traits<WrappedIteratorT>::value_type>::type>
+template <typename WrappedIteratorT,
+ typename T = typename std::remove_reference<
+ decltype(**std::declval<WrappedIteratorT>())>::type>
struct pointee_iterator
- : iterator_adaptor_base<pointee_iterator<WrappedIteratorT>,
- WrappedIteratorT, T> {
- pointee_iterator() {}
+ : iterator_adaptor_base<
+ pointee_iterator<WrappedIteratorT>, WrappedIteratorT,
+ typename std::iterator_traits<WrappedIteratorT>::iterator_category,
+ T> {
+ pointee_iterator() = default;
template <typename U>
pointee_iterator(U &&u)
: pointee_iterator::iterator_adaptor_base(std::forward<U &&>(u)) {}
T &operator*() const { return **this->I; }
};
-}
+} // namespace llvm
#endif
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