libc/src/__support/CPP/iterator.h

   1 //===-- Standalone implementation of iterator -------------------*- 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_LIBC_SRC___SUPPORT_CPP_ITERATOR_H
  10 #define LLVM_LIBC_SRC___SUPPORT_CPP_ITERATOR_H
  11
  12 #include "src/__support/CPP/type_traits/enable_if.h"
  13 #include "src/__support/CPP/type_traits/is_convertible.h"
  14 #include "src/__support/CPP/type_traits/is_same.h"
  15 #include "src/__support/macros/attributes.h"
  16 #include "src/__support/macros/config.h"
  17
  18 namespace LIBC_NAMESPACE_DECL {
  19 namespace cpp {
  20
  21 template <typename T> struct iterator_traits;
  22 template <typename T> struct iterator_traits<T *> {
  23   using reference = T &;
  24   using value_type = T;
  25 };
  26
  27 template <typename Iter> class reverse_iterator {
  28   Iter current;
  29
  30 public:
  31   using reference = typename iterator_traits<Iter>::reference;
  32   using value_type = typename iterator_traits<Iter>::value_type;
  33   using iterator_type = Iter;
  34
  35   LIBC_INLINE reverse_iterator() : current() {}
  36   LIBC_INLINE constexpr explicit reverse_iterator(Iter it) : current(it) {}
  37
  38   template <typename Other,
  39             cpp::enable_if_t<!cpp::is_same_v<Iter, Other> &&
  40                                  cpp::is_convertible_v<const Other &, Iter>,
  41                              int> = 0>
  42   LIBC_INLINE constexpr explicit reverse_iterator(const Other &it)
  43       : current(it) {}
  44
  45   LIBC_INLINE friend constexpr bool operator==(const reverse_iterator &lhs,
  46                                                const reverse_iterator &rhs) {
  47     return lhs.base() == rhs.base();
  48   }
  49
  50   LIBC_INLINE friend constexpr bool operator!=(const reverse_iterator &lhs,
  51                                                const reverse_iterator &rhs) {
  52     return lhs.base() != rhs.base();
  53   }
  54
  55   LIBC_INLINE friend constexpr bool operator<(const reverse_iterator &lhs,
  56                                               const reverse_iterator &rhs) {
  57     return lhs.base() > rhs.base();
  58   }
  59
  60   LIBC_INLINE friend constexpr bool operator<=(const reverse_iterator &lhs,
  61                                                const reverse_iterator &rhs) {
  62     return lhs.base() >= rhs.base();
  63   }
  64
  65   LIBC_INLINE friend constexpr bool operator>(const reverse_iterator &lhs,
  66                                               const reverse_iterator &rhs) {
  67     return lhs.base() < rhs.base();
  68   }
  69
  70   LIBC_INLINE friend constexpr bool operator>=(const reverse_iterator &lhs,
  71                                                const reverse_iterator &rhs) {
  72     return lhs.base() <= rhs.base();
  73   }
  74
  75   LIBC_INLINE constexpr iterator_type base() const { return current; }
  76
  77   LIBC_INLINE constexpr reference operator*() const {
  78     Iter tmp = current;
  79     return *--tmp;
  80   }
  81   LIBC_INLINE constexpr reverse_iterator operator--() {
  82     ++current;
  83     return *this;
  84   }
  85   LIBC_INLINE constexpr reverse_iterator &operator++() {
  86     --current;
  87     return *this;
  88   }
  89   LIBC_INLINE constexpr reverse_iterator operator++(int) {
  90     reverse_iterator tmp(*this);
  91     --current;
  92     return tmp;
  93   }
  94 };
  95
  96 } // namespace cpp
  97 } // namespace LIBC_NAMESPACE_DECL
  98
  99 #endif // LLVM_LIBC_SRC___SUPPORT_CPP_ITERATOR_H