chromium/third_party/pdfium/core/fxcrt/containers/contains.h

// Copyright 2024 The PDFium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CORE_FXCRT_CONTAINERS_CONTAINS_H_
#define CORE_FXCRT_CONTAINERS_CONTAINS_H_

#include <algorithm>
#include <iterator>
#include <type_traits>

#include "core/fxcrt/template_util.h"

namespace pdfium {

namespace internal {

// Small helper to detect whether a given type has a nested `key_type` typedef.
// Used below to catch misuses of the API for associative containers.
template <typename T, typename SFINAE = void>
struct HasKeyType : std::false_type { … };

HasKeyType<T, std::void_t<typename T::key_type>>;

// Utility type traits used for specializing pdfium::Contains() below.
template <typename Container, typename Element, typename = void>
struct HasFindWithNpos : std::false_type { … };

HasFindWithNpos<Container, Element, std::void_t<decltype(std::declval<const Container &>().find(std::declval<const Element &>()) != Container::npos)>>;

template <typename Container, typename Element, typename = void>
struct HasFindWithEnd : std::false_type { … };

HasFindWithEnd<Container, Element, std::void_t<decltype(std::declval<const Container &>().find(std::declval<const Element &>()) != std::declval<const Container &>().end())>>;

template <typename Container, typename Element, typename = void>
struct HasContains : std::false_type { … };

HasContains<Container, Element, std::void_t<decltype(std::declval<const Container &>().contains(std::declval<const Element &>()))>>;

}  // namespace internal

// General purpose implementation to check if |container| contains |value|.
template <typename Container,
          typename Value,
          std::enable_if_t<
              !internal::HasFindWithNpos<Container, Value>::value &&
              !internal::HasFindWithEnd<Container, Value>::value &&
              !internal::HasContains<Container, Value>::value>* = nullptr>
bool Contains(const Container& container, const Value& value) { … }

// Specialized Contains() implementation for when |container| has a find()
// member function and a static npos member, but no contains() member function.
template <typename Container,
          typename Value,
          std::enable_if_t<internal::HasFindWithNpos<Container, Value>::value &&
                           !internal::HasContains<Container, Value>::value>* =
              nullptr>
bool Contains(const Container& container, const Value& value) { … }

// Specialized Contains() implementation for when |container| has a find()
// and end() member function, but no contains() member function.
template <typename Container,
          typename Value,
          std::enable_if_t<internal::HasFindWithEnd<Container, Value>::value &&
                           !internal::HasContains<Container, Value>::value>* =
              nullptr>
bool Contains(const Container& container, const Value& value) { … }

// Specialized Contains() implementation for when |container| has a contains()
// member function.
template <
    typename Container,
    typename Value,
    std::enable_if_t<internal::HasContains<Container, Value>::value>* = nullptr>
bool Contains(const Container& container, const Value& value) { … }

}  // namespace pdfium

#endif  // CORE_FXCRT_CONTAINERS_CONTAINS_H_