namespace llvm {
+/// \brief CRTP base class which implements the entire standard iterator facade
+/// in terms of a minimal subset of the interface.
+///
+/// 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.
+///
+/// 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, typename PointerT = T *,
+ typename ReferenceT = T &>
+struct iterator_facade_base
+ : std::iterator<IteratorCategoryT, T, DifferenceTypeT, PointerT,
+ ReferenceT> {
+ DerivedT operator+(DifferenceTypeT n) const {
+ DerivedT tmp = *static_cast<const DerivedT *>(this);
+ tmp += n;
+ return tmp;
+ }
+ friend DerivedT operator+(DifferenceTypeT n, const DerivedT &i) {
+ return i + n;
+ }
+ DerivedT operator-(DifferenceTypeT n) const {
+ DerivedT tmp = *static_cast<const DerivedT *>(this);
+ tmp -= n;
+ return tmp;
+ }
+
+ DerivedT &operator++() {
+ return static_cast<DerivedT *>(this)->operator+=(1);
+ }
+ DerivedT operator++(int) {
+ DerivedT tmp = *static_cast<DerivedT *>(this);
+ ++*static_cast<DerivedT *>(this);
+ return tmp;
+ }
+ DerivedT &operator--() {
+ return static_cast<DerivedT *>(this)->operator-=(1);
+ }
+ DerivedT operator--(int) {
+ DerivedT tmp = *static_cast<DerivedT *>(this);
+ --*static_cast<DerivedT *>(this);
+ return tmp;
+ }
+
+ bool operator!=(const DerivedT &RHS) const {
+ return !static_cast<const DerivedT *>(this)->operator==(RHS);
+ }
+
+ bool operator>(const DerivedT &RHS) const {
+ return !static_cast<const DerivedT *>(this)->operator<(RHS) &&
+ !static_cast<const DerivedT *>(this)->operator==(RHS);
+ }
+ bool operator<=(const DerivedT &RHS) const {
+ return !static_cast<const DerivedT *>(this)->operator>(RHS);
+ }
+ bool operator>=(const DerivedT &RHS) const {
+ return !static_cast<const DerivedT *>(this)->operator<(RHS);
+ }
+
+ PointerT operator->() const {
+ return &static_cast<const DerivedT *>(this)->operator*();
+ }
+ ReferenceT operator[](DifferenceTypeT n) const {
+ 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.
-///
-/// 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,
- ReferenceT> {
+ : public iterator_facade_base<
+ DerivedT, typename WrappedTraitsT::iterator_category, T,
+ typename WrappedTraitsT::difference_type, PointerT, ReferenceT> {
protected:
WrappedIteratorT I;
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>
+ !std::is_base_of<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)) {}
public:
- typedef typename iterator_adaptor_base::iterator::difference_type
- difference_type;
+ typedef typename WrappedTraitsT::difference_type difference_type;
DerivedT &operator+=(difference_type n) {
I += n;
I -= n;
return *static_cast<DerivedT *>(this);
}
- DerivedT operator+(difference_type n) const {
- DerivedT tmp = *this;
- tmp += n;
- return tmp;
- }
- friend DerivedT operator+(difference_type n, const DerivedT &i) {
- return i + n;
- }
- DerivedT operator-(difference_type n) const {
- DerivedT tmp = *this;
- tmp -= n;
- return tmp;
- }
+ using iterator_adaptor_base::iterator_facade_base::operator-;
difference_type operator-(const DerivedT &RHS) const { return I - RHS.I; }
+ // We have to explicitly provide ++ and -- rather than letting the facade
+ // forward to += because WrappedIteratorT might not support +=.
+ using iterator_adaptor_base::iterator_facade_base::operator++;
DerivedT &operator++() {
++I;
return *static_cast<DerivedT *>(this);
}
+ using iterator_adaptor_base::iterator_facade_base::operator--;
DerivedT &operator--() {
--I;
return *static_cast<DerivedT *>(this);
}
- DerivedT operator++(int) {
- DerivedT tmp = *static_cast<DerivedT *>(this);
- ++*this;
- return tmp;
- }
- DerivedT operator--(int) {
- DerivedT tmp = *static_cast<DerivedT *>(this);
- --*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 {
- return !static_cast<const DerivedT *>(this)->operator<(RHS) &&
- !static_cast<const DerivedT *>(this)->operator==(RHS);
- }
- bool operator<=(const DerivedT &RHS) const {
- return !static_cast<const DerivedT *>(this)->operator>(RHS);
- }
- bool operator>=(const DerivedT &RHS) const {
- return !static_cast<const DerivedT *>(this)->operator<(RHS);
- }
ReferenceT operator*() const { return *I; }
- PointerT operator->() const {
- return static_cast<const DerivedT *>(this)->operator*();
- }
- ReferenceT operator[](difference_type n) const {
- return *static_cast<const DerivedT *>(this)->operator+(n);
- }
};
/// \brief An iterator type that allows iterating over the pointees via some