bsltf_inputiterator.h

Go to the documentation of this file.

/// @file bsltf_inputiterator.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bsltf_inputiterator.h                                              -*-C++-*-
#ifndef INCLUDED_BSLTF_INPUTITERATOR
#define INCLUDED_BSLTF_INPUTITERATOR
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bsltf_inputiterator bsltf_inputiterator
/// @brief  Provide a pure input iterator capable of traversing a range.
/// @addtogroup bsl
/// @{
/// @addtogroup bsltf
/// @{
/// @addtogroup bsltf_inputiterator
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bsltf_inputiterator-purpose"> Purpose</a>
/// * <a href="#bsltf_inputiterator-classes"> Classes </a>
/// * <a href="#bsltf_inputiterator-description"> Description </a>
///   * <a href="#bsltf_inputiterator-usage"> Usage </a>
///     * <a href="#bsltf_inputiterator-example-1-basic-use-of-bsltf-inputiterator"> Example 1: Basic Use of bsltf::InputIterator: </a>
///
/// # Purpose {#bsltf_inputiterator-purpose}
/// Provide a pure input iterator capable of traversing a range.
///
/// # Classes {#bsltf_inputiterator-classes}
///
/// -  bsltf::InputIterator: empty input iterator template
///
/// # Description {#bsltf_inputiterator-description}
/// This components provides a value-semantic `class`,
/// `bsltf::InputIterator`, that defines an input iterator that supports the
/// following operations:
///
/// * Obj& operator++()
/// * Obj operator++(int)
/// * pointer operator->() const
/// * reference& operator*() const
///
/// The iterator is initializable with either a pointer into a range, or a
/// non-pointer iterator over a contiguous range.
///
/// This iterator type is typically used to check algorithms for compatibility
/// with input iterators.  The goal is to make sure that their code is able to
/// compile and work even with the most restrictive input iterator.
///
/// ## Usage {#bsltf_inputiterator-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Basic Use of bsltf::InputIterator: {#bsltf_inputiterator-example-1-basic-use-of-bsltf-inputiterator}
///
///
/// In the following example we use a `bsltf::InputIterator` to test that an
/// aggregation function compiles and works when instantiated with a pure input
/// iterator.
///
/// First, we define a function `sum` that accepts two input iterators and
/// returns the sum of all elements in range specified by them:
/// @code
/// template <class IN_ITER>
/// double sum(IN_ITER first, IN_ITER last)
///     // Return the sum of the 'double's in the specified range
///     // '[ first, last )'.
/// {
///     double total = 0;
///     while (first != last) {
///         total += *first++;
///     }
///     return total;
/// }
/// @endcode
/// Then, in `main`, we define an array of `double`s and define `InputIterators`
/// pointing to the beginning and ending of it, initializing the iterators with
/// pointers:
/// @code
/// static double myArray[] = { 2.5, 3, 5, 7, 11.5, 5 };
/// enum { k_MY_ARRAY_LEN = sizeof myArray / sizeof *myArray };
///
/// typedef bsltf::InputIterator<const double> Iter;
///
/// Iter begin(myArray + 0), end(myArray + k_MY_ARRAY_LEN);
/// @endcode
/// Next, we call `sum` with the two iterators, and observe that its yields the
/// expected result, and because it compiles, we know that `sum` did not attempt
/// any operations on the iterators other than those defined for the most basic
/// input iterator:
/// @code
/// const double x = sum(begin, end);
/// assert(34.0 == x);
/// @endcode
/// Then, we illustrate that we can just make `begin` and `end` iterators from
/// the array directly with the `begin` and `end` class methods of the
/// `InputIteratorUtil` class.
/// @code
/// typedef bsltf::InputIteratorUtil Util;
///
/// const double y = sum(Util::begin(myArray), Util::end(myArray));
/// assert(34.0 == y);
/// @endcode
/// Now, we make an `std::vector` containing the elements of `myArray`:
/// @code
/// const std::vector<double> v(myArray + 0, myArray + k_MY_ARRAY_LEN);
/// @endcode
/// Finally, we call `sum` using, again, the `begin` and `end` class methods to
/// create iterators for it directly from our `vector`:
/// @code
/// const double z = sum(Util::begin(v), Util::end(v));
/// assert(34.0 == z);
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bsltf
 * @{
 */
/** @addtogroup bsltf_inputiterator
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bsls_assert.h>
#include <bsls_libraryfeatures.h>
 
#include <cstddef>
#include <iterator>
 
 
namespace bsltf {
 
                            // ===================
                            // class InputIterator
                            // ===================
 
#if defined(BSLS_LIBRARYFEATURES_STDCPP_LIBCSTD)
// Sun CC workaround: iterators must be derived from 'std::iterator' to work
// with the native std library algorithms.  However, 'std::iterator' is
// deprecated in C++17, so do not rely on derivation unless required, to avoid
// deprecation warnings on modern compilers.
 
template <class TYPE>
class InputIterator : public std::iterator<std::input_iterator_tag,
                                           TYPE,
                                           std::ptrdiff_t,
                                           TYPE *,
                                           TYPE> {
#else
template <class TYPE>
class InputIterator {
#endif
    // Provide an input iterator that iterates that can iterate over a
    // contiguous range of object while supporting no operations other than
    // those defined for 'LegacyInputIterator'.
 
  public:
    // PUBLIC TYPES
    typedef std::input_iterator_tag  iterator_category;
    typedef TYPE                     value_type;
    typedef std::ptrdiff_t           difference_type;
    typedef TYPE                    *pointer;
    typedef TYPE&                    reference;
 
  private:
    // DATA
    TYPE *d_value_p;
 
    // FRIENDS
    template <class TYPE2>
    friend bool operator==(const InputIterator<TYPE2>&,
                           const InputIterator<TYPE2>&);
    template <class TYPE2>
    friend bool operator!=(const InputIterator<TYPE2>&,
                           const InputIterator<TYPE2>&);
 
  public:
    // CREATORS
 
    /// Construct an empty input iterator.
    InputIterator();
 
    /// Construct an input iterator based on the specified `ptr`.
    explicit InputIterator(TYPE *ptr);
 
    // InputIterator(const InputIterator& original) = default;
        // Construct a copy of the specified 'original' object.
 
    // ~InputIterator() = default;
        // Destroy this object.
 
    // MANIPULATORS
    // InputIterator& operator=(const InputIterator& rhs) = default;
        // Assign to this object the value of the specified 'rhs' and return a
        // reference to this modifiable object.
 
    /// Increment this iterator to refer to the next contiguous `TYPE`
    /// object, and return a reference to after the increment.  The behavior
    /// is undefined if this iterator is empty.
    InputIterator& operator++();
 
    /// Copy this iterator, increment, and return by value the copy that was
    /// made prior to the increment.  The behavior is undefined if this
    /// iterator is empty.
    InputIterator operator++(int);
 
    // ACCESSORS
 
    /// Return a pointer to the `TYPE` object referred to by this iterator.
    /// The behavior is undefined if this iterator is empty.
    pointer operator->() const;
 
    /// Return a const reference to the `TYPE` object referred to by this
    /// iterator.  The behavior is undefined if this iterator is empty.
    reference operator*() const;
};
 
// FREE OPERATORS
 
/// Return `true` if the specified `lhs` and `rhs` refer to the same `TYPE`
/// object and `false` othersise.
template <class TYPE>
inline
bool operator==(const InputIterator<TYPE>& lhs,
                const InputIterator<TYPE>& rhs);
 
/// Return `true` if the specified `lhs` and `rhs` do not refer to the same
/// `TYPE` object and `false` othersise.
template <class TYPE>
inline
bool operator!=(const InputIterator<TYPE>& lhs,
                const InputIterator<TYPE>& rhs);
 
                          // =======================
                          // class InputIteratorUtil
                          // =======================
 
/// This namespace `struct` allows the easy creation of `begin` and `end`
/// iterators from a variety of contiguous range types.  Either the argument
/// must be an array, or a container that supports the following operations:
/// * `size()`
/// * `operator@ref size_t ` (if 0 != size())
///
/// and the type `CONTIGUOUS_CONTAINER::value_type`.
struct InputIteratorUtil {
 
    // CLASS METHODS
 
    /// Return an `InputIterator` referring to the first element of the
    /// specified `container` or a null iterator if `container` is empty.
    template <class CONTIGUOUS_CONTAINER>
    static InputIterator<typename CONTIGUOUS_CONTAINER::value_type> begin(
                                              CONTIGUOUS_CONTAINER& container);
    template <class CONTIGUOUS_CONTAINER>
    static InputIterator<const typename CONTIGUOUS_CONTAINER::value_type>
                                  begin(const CONTIGUOUS_CONTAINER& container);
 
    /// Return an `InputIterator` referring to the first element of the
    /// specified `array`.
    template <class TYPE, std::size_t LEN>
    static InputIterator<TYPE> begin(TYPE (&array)[LEN]);
    template <class TYPE, std::size_t LEN>
    static InputIterator<const TYPE> begin(const TYPE (&array)[LEN]);
 
    /// Return an `InputIterator` referring to after the last element of the
    /// specified `container` or a null iterator if `container` is empty.
    template <class CONTIGUOUS_CONTAINER>
    static InputIterator<typename CONTIGUOUS_CONTAINER::value_type> end(
                                              CONTIGUOUS_CONTAINER& container);
    template <class CONTIGUOUS_CONTAINER>
    static InputIterator<const typename CONTIGUOUS_CONTAINER::value_type> end(
                                        const CONTIGUOUS_CONTAINER& container);
 
    /// Return an `InputIterator` referring to after the last element of the
    /// specified `array`.
    template <class TYPE, std::size_t LEN>
    static InputIterator<TYPE> end(TYPE (&array)[LEN]);
    template <class TYPE, std::size_t LEN>
    static InputIterator<const TYPE> end(const TYPE (&array)[LEN]);
};
 
// ============================================================================
//                              INLINE DEFINITIONS
// ============================================================================
 
                              // -------------------
                              // class InputIterator
                              // -------------------
 
// CREATORS
template<class TYPE>
inline
InputIterator<TYPE>::InputIterator()
: d_value_p(0)
{
}
 
template<class TYPE>
inline
InputIterator<TYPE>::InputIterator(TYPE *ptr)
: d_value_p(ptr)
{
}
 
// MANIPULATORS
template<class TYPE>
inline
InputIterator<TYPE>& InputIterator<TYPE>::operator++()
{
    BSLS_ASSERT_SAFE(d_value_p);
 
    ++d_value_p;
 
    return *this;
}
 
template<class TYPE>
inline
InputIterator<TYPE> InputIterator<TYPE>::operator++(int)
{
    BSLS_ASSERT_SAFE(d_value_p);
 
    TYPE *prev = d_value_p++;
    return InputIterator(prev);
}
 
// ACCESSORS
template<class TYPE>
inline
typename InputIterator<TYPE>::pointer InputIterator<TYPE>::operator->() const
{
    BSLS_ASSERT_SAFE(d_value_p);
 
    return d_value_p;
}
 
template<class TYPE>
inline
typename InputIterator<TYPE>::reference InputIterator<TYPE>::operator*() const
{
    BSLS_ASSERT_SAFE(d_value_p);
 
    return *d_value_p;
}
 
}  // close package namespace
 
// FREE OPERATORS
template <class TYPE>
inline
bool bsltf::operator==(const bsltf::InputIterator<TYPE>& lhs,
                       const bsltf::InputIterator<TYPE>& rhs)
{
    return lhs.d_value_p == rhs.d_value_p;
}
 
template <class TYPE>
inline
bool bsltf::operator!=(const bsltf::InputIterator<TYPE>& lhs,
                       const bsltf::InputIterator<TYPE>& rhs)
{
    return lhs.d_value_p != rhs.d_value_p;
}
 
namespace bsltf {
 
                          // -----------------------
                          // class InputIteratorUtil
                          // -----------------------
 
// CLASS METHODS
template <class CONTIGUOUS_CONTAINER>
inline
InputIterator<typename CONTIGUOUS_CONTAINER::value_type>
                      InputIteratorUtil::begin(CONTIGUOUS_CONTAINER& container)
{
    return InputIterator<typename CONTIGUOUS_CONTAINER::value_type>(
                                    0 == container.size() ? 0 : &container[0]);
}
 
template <class CONTIGUOUS_CONTAINER>
InputIterator<const typename CONTIGUOUS_CONTAINER::value_type>
                InputIteratorUtil::begin(const CONTIGUOUS_CONTAINER& container)
{
    return InputIterator<const typename CONTIGUOUS_CONTAINER::value_type>(
                                    0 == container.size() ? 0 : &container[0]);
}
 
template <class TYPE, std::size_t LEN>
InputIterator<TYPE> InputIteratorUtil::begin(TYPE (&array)[LEN])
{
    return InputIterator<TYPE>(array + 0);
}
 
template <class TYPE, std::size_t LEN>
InputIterator<const TYPE> InputIteratorUtil::begin(const TYPE (&array)[LEN])
{
    return InputIterator<const TYPE>(array + 0);
}
 
template <class CONTIGUOUS_CONTAINER>
InputIterator<typename CONTIGUOUS_CONTAINER::value_type>
                        InputIteratorUtil::end(CONTIGUOUS_CONTAINER& container)
{
    return InputIterator<typename CONTIGUOUS_CONTAINER::value_type>(
                 0 == container.size() ? 0 : &container[0] + container.size());
}
 
template <class CONTIGUOUS_CONTAINER>
InputIterator<const typename CONTIGUOUS_CONTAINER::value_type>
                  InputIteratorUtil::end(const CONTIGUOUS_CONTAINER& container)
{
    return InputIterator<const typename CONTIGUOUS_CONTAINER::value_type>(
                 0 == container.size() ? 0 : &container[0] + container.size());
}
 
template <class TYPE, std::size_t LEN>
InputIterator<TYPE> InputIteratorUtil::end(TYPE (&array)[LEN])
{
    return InputIterator<TYPE>(array + LEN);
}
 
template <class TYPE, std::size_t LEN>
InputIterator<const TYPE> InputIteratorUtil::end(const TYPE (&array)[LEN])
{
    return InputIterator<const TYPE>(array + LEN);
}
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2021 Bloomberg Finance L.P.
//
// 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
//
//     http://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.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */