third-party/thrift/src/thrift/compiler/ast/detail/view.h

   1 /*
   2  * Copyright (c) Meta Platforms, Inc. and affiliates.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #pragma once
  18
  19 #include <cassert>
  20 #include <cstddef>
  21 #include <iterator>
  22 #include <type_traits>
  23
  24 namespace apache {
  25 namespace thrift {
  26 namespace compiler {
  27 namespace ast_detail {
  28
  29 template <typename Derived, typename T>
  30 class base_view {
  31  public:
  32   using element_type = T;
  33   using value_type = std::remove_cv_t<T>;
  34
  35   constexpr auto rbegin() const noexcept {
  36     return std::make_reverse_iterator(derived().end());
  37   }
  38   constexpr auto rend() const noexcept {
  39     return std::make_reverse_iterator(derived().begin());
  40   }
  41   constexpr bool empty() const noexcept { return derived().size() == 0; }
  42
  43  private:
  44   Derived& derived() { return *static_cast<Derived*>(this); }
  45   const Derived& derived() const { return *static_cast<const Derived*>(this); }
  46 };
  47
  48 template <typename Derived, typename T>
  49 class base_span : public base_view<Derived, T> {
  50   using base = base_view<Derived, T>;
  51
  52  public:
  53   using size_type = std::size_t;
  54   using difference_type = std::ptrdiff_t;
  55   using pointer = T*;
  56   using reference = T&;
  57   using iterator = pointer;
  58   using reverse_iterator = std::reverse_iterator<iterator>;
  59   using const_iterator = iterator;
  60
  61   constexpr base_span(pointer data, std::size_t size) noexcept
  62       : data_(data), size_(size) {}
  63
  64   constexpr iterator begin() const noexcept { return data_; }
  65   constexpr iterator end() const noexcept { return data_ + size_; }
  66   constexpr size_type size() const noexcept { return size_; }
  67   constexpr reference operator[](size_type pos) const {
  68     assert(pos < size_);
  69     return *(data_ + pos);
  70   }
  71   constexpr reference front() const { return operator[](0); }
  72   constexpr reference back() const {
  73     assert(size_ > 0);
  74     return operator[](size_ - 1);
  75   }
  76
  77  private:
  78   pointer data_;
  79   size_type size_;
  80 };
  81
  82 } // namespace ast_detail
  83 } // namespace compiler
  84 } // namespace thrift
  85 } // namespace apache