str_split_internal.h | Explore in Territory

// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

// This file declares INTERNAL parts of the Split API that are inline/templated
// or otherwise need to be available at compile time. The main abstractions
// defined in here are
//
//   - ConvertibleToStringView
//   - SplitIterator<>
//   - Splitter<>
//
// DO NOT INCLUDE THIS FILE DIRECTLY. Use this file by including
// absl/strings/str_split.h.
//
// IWYU pragma: private, include "absl/strings/str_split.h"

#ifndef ABSL_STRINGS_INTERNAL_STR_SPLIT_INTERNAL_H_
#define ABSL_STRINGS_INTERNAL_STR_SPLIT_INTERNAL_H_

#include <array>
#include <cstddef>
#include <initializer_list>
#include <iterator>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>

#include "absl/base/macros.h"
#include "absl/base/port.h"
#include "absl/meta/type_traits.h"
#include "absl/strings/string_view.h"

#ifdef _GLIBCXX_DEBUG
#include "absl/strings/internal/stl_type_traits.h"
#endif  // _GLIBCXX_DEBUG

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace strings_internal {

// This class is implicitly constructible from everything that absl::string_view
// is implicitly constructible from, except for rvalue strings.  This means it
// can be used as a function parameter in places where passing a temporary
// string might cause memory lifetime issues.
class ConvertibleToStringView { … };

// An iterator that enumerates the parts of a string from a Splitter. The text
// to be split, the Delimiter, and the Predicate are all taken from the given
// Splitter object. Iterators may only be compared if they refer to the same
// Splitter instance.
//
// This class is NOT part of the public splitting API.
template <typename Splitter>
class SplitIterator { … };

// HasMappedType<T>::value is true iff there exists a type T::mapped_type.
template <typename T, typename = void>
struct HasMappedType : std::false_type { … };
template <typename T>
struct HasMappedType<T, absl::void_t<typename T::mapped_type>>
    : std::true_type {};

// HasValueType<T>::value is true iff there exists a type T::value_type.
template <typename T, typename = void>
struct HasValueType : std::false_type { … };
template <typename T>
struct HasValueType<T, absl::void_t<typename T::value_type>> : std::true_type {
};

// HasConstIterator<T>::value is true iff there exists a type T::const_iterator.
template <typename T, typename = void>
struct HasConstIterator : std::false_type { … };
template <typename T>
struct HasConstIterator<T, absl::void_t<typename T::const_iterator>>
    : std::true_type {};

// HasEmplace<T>::value is true iff there exists a method T::emplace().
template <typename T, typename = void>
struct HasEmplace : std::false_type { … };
template <typename T>
struct HasEmplace<T, absl::void_t<decltype(std::declval<T>().emplace())>>
    : std::true_type {};

// IsInitializerList<T>::value is true iff T is an std::initializer_list. More
// details below in Splitter<> where this is used.
std::false_type IsInitializerListDispatch(...);  // default: No
template <typename T>
std::true_type IsInitializerListDispatch(std::initializer_list<T>*);
template <typename T>
struct IsInitializerList
    : decltype(IsInitializerListDispatch(static_cast<T*>(nullptr))) { … };

// A SplitterIsConvertibleTo<C>::type alias exists iff the specified condition
// is true for type 'C'.
//
// Restricts conversion to container-like types (by testing for the presence of
// a const_iterator member type) and also to disable conversion to an
// std::initializer_list (which also has a const_iterator). Otherwise, code
// compiled in C++11 will get an error due to ambiguous conversion paths (in
// C++11 std::vector<T>::operator= is overloaded to take either a std::vector<T>
// or an std::initializer_list<T>).

template <typename C, bool has_value_type, bool has_mapped_type>
struct SplitterIsConvertibleToImpl : std::false_type { … };

SplitterIsConvertibleToImpl<C, true, false>;

SplitterIsConvertibleToImpl<C, true, true>;

template <typename C>
struct SplitterIsConvertibleTo
    : SplitterIsConvertibleToImpl<
          C,
#ifdef _GLIBCXX_DEBUG
          !IsStrictlyBaseOfAndConvertibleToSTLContainer<C>::value &&
#endif  // _GLIBCXX_DEBUG
              !IsInitializerList<
                  typename std::remove_reference<C>::type>::value &&
              HasValueType<C>::value && HasConstIterator<C>::value,
          HasMappedType<C>::value> { … };

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

template <typename StringType, typename Container>
struct ShouldUseLifetimeBound<
    StringType, Container,
    std::enable_if_t<
        std::is_same<StringType, std::string>::value &&
        std::is_same<typename Container::value_type, absl::string_view>::value>>
    : std::true_type {};

template <typename StringType, typename First, typename Second>
using ShouldUseLifetimeBoundForPair = std::integral_constant<
    bool, std::is_same<StringType, std::string>::value &&
              (std::is_same<First, absl::string_view>::value ||
               std::is_same<Second, absl::string_view>::value)>;


// This class implements the range that is returned by absl::StrSplit(). This
// class has templated conversion operators that allow it to be implicitly
// converted to a variety of types that the caller may have specified on the
// left-hand side of an assignment.
//
// The main interface for interacting with this class is through its implicit
// conversion operators. However, this class may also be used like a container
// in that it has .begin() and .end() member functions. It may also be used
// within a range-for loop.
//
// Output containers can be collections of any type that is constructible from
// an absl::string_view.
//
// An Predicate functor may be supplied. This predicate will be used to filter
// the split strings: only strings for which the predicate returns true will be
// kept. A Predicate object is any unary functor that takes an absl::string_view
// and returns bool.
//
// The StringType parameter can be either string_view or string, depending on
// whether the Splitter refers to a string stored elsewhere, or if the string
// resides inside the Splitter itself.
template <typename Delimiter, typename Predicate, typename StringType>
class Splitter { … };

}  // namespace strings_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_STRINGS_INTERNAL_STR_SPLIT_INTERNAL_H_
chromium/third_party/abseil-cpp/absl/strings/internal/str_split_internal.h
