bslstl_mapcomparator.h

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/// @file bslstl_mapcomparator.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslstl_mapcomparator.h                                             -*-C++-*-
#ifndef INCLUDED_BSLSTL_MAPCOMPARATOR
#define INCLUDED_BSLSTL_MAPCOMPARATOR
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslstl_mapcomparator bslstl_mapcomparator
/// @brief  Provide a comparator for `TreeNode` objects and a lookup key.
/// @addtogroup bsl
/// @{
/// @addtogroup bslstl
/// @{
/// @addtogroup bslstl_mapcomparator
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslstl_mapcomparator-purpose"> Purpose</a>
/// * <a href="#bslstl_mapcomparator-classes"> Classes </a>
/// * <a href="#bslstl_mapcomparator-description"> Description </a>
///   * <a href="#bslstl_mapcomparator-usage"> Usage </a>
///     * <a href="#bslstl_mapcomparator-example-1-create-a-simple-tree-of-treenode-objects"> Example 1: Create a Simple Tree of TreeNode Objects </a>
///
/// # Purpose {#bslstl_mapcomparator-purpose}
/// Provide a comparator for `TreeNode` objects and a lookup key.
///
/// # Classes {#bslstl_mapcomparator-classes}
///
/// -   bslstl::MapComparator: comparator for `TreeNode` objects and key objects
///
/// @see  bslstl_map, bslstl_treenode, bslalg_rbtreeutil
///
/// # Description {#bslstl_mapcomparator-description}
/// This component provides a functor adapter, `MapComparator`,
/// that adapts a parameterized `COMPARATOR` comparing objects of a
/// parameterized `KEY` type into a functor comparing a object of `KEY` type
/// with objects of `TreeNode` type holding a `bsl::pair<KEY, VALUE>` object.
/// Note that this functor was designed to be supplied to functions in
/// `bslalg::RbTreeUtil`, primarily for the purpose of implementing a `map`
/// container using the utilities defined in `bslalg::RbTreeUtil`.
///
/// ## Usage {#bslstl_mapcomparator-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Create a Simple Tree of TreeNode Objects {#bslstl_mapcomparator-example-1-create-a-simple-tree-of-treenode-objects}
///
///
/// Suppose that we want to create a tree of `TreeNode` objects arranged
/// according to a functor that we supply.
///
/// First, we create an array of `bslstl::TreeNode` objects, each holding a pair
/// of integers:
/// @code
/// typedef bsl::allocator<TreeNode<bsl::pair<int, int> > > Alloc;
///
/// bslma::TestAllocator oa;
/// Alloc allocator(&oa);
///
/// enum { NUM_NODES = 5 };
///
/// bslstl::TreeNode<bsl::pair<int, int> >* nodes[NUM_NODES];
///
/// typedef bsl::allocator_traits<Alloc>  AllocTraits;
///
/// for (int i = 0; i < NUM_NODES; ++i) {
///     nodes[i] = AllocTraits::allocate(allocator, 1);
///     AllocTraits::construct(allocator, &nodes[i]->value(),
///                            i, 2*i);
/// }
/// @endcode
/// Then, we define a `MapComparator` object, `comparator`, for comparing
/// `bslstl::TreeNode<pair<int, int> >` objects with integers.
/// @code
/// MapComparator<int, int, std::less<int> > comparator;
/// @endcode
/// Now, we can use the functions in `bslalg::RbTreeUtil` to arrange our tree:
/// @code
/// bslalg::RbTreeAnchor tree;
///
/// for (int i = 0; i < NUM_NODES; ++i) {
///     int comparisonResult;
///     bslalg::RbTreeNode *insertLocation =
///         bslalg::RbTreeUtil::findUniqueInsertLocation(
///             &comparisonResult,
///             &tree,
///             comparator,
///             nodes[i]->value().first);
///
///     assert(0 != comparisonResult);
///
///     bslalg::RbTreeUtil::insertAt(&tree,
///                                  insertLocation,
///                                  comparisonResult < 0,
///                                  nodes[i]);
/// }
///
/// assert(5 == tree.numNodes());
/// @endcode
/// Then, we use `bslalg::RbTreeUtil::next()` to navigate the elements of the
/// tree, printing their values:
/// @code
/// const bslalg::RbTreeNode *nodeIterator = tree.firstNode();
///
/// while (nodeIterator != tree.sentinel()) {
///     const TreeNode<bsl::pair<int, int> > *node =
///     static_cast<const TreeNode<bsl::pair<int, int> >*>(nodeIterator);
///     printf("Node value: (%d, %d)\n",
///            node->value().first, node->value().second);
///     nodeIterator = bslalg::RbTreeUtil::next(nodeIterator);
/// }
/// @endcode
/// Next, we destroy and deallocate each of the `bslstl::TreeNode` objects:
/// @code
/// for (int i = 0; i < NUM_NODES; ++i) {
///     AllocTraits::destroy(allocator, &nodes[i]->value());
///     AllocTraits::deallocate(allocator, nodes[i], 1);
/// }
/// @endcode
/// Finally, we observe the console output:
/// @code
/// Node value: (0, 0)
/// Node value: (1, 2)
/// Node value: (2, 4)
/// Node value: (3, 6)
/// Node value: (4, 8)
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslstl
 * @{
 */
/** @addtogroup bslstl_mapcomparator
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslstl_pair.h>
#include <bslstl_treenode.h>
 
#include <bslalg_functoradapter.h>
#include <bslalg_swaputil.h>
 
#include <bsls_platform.h>
#include <bsls_util.h>
 
 
namespace bslstl {
 
                       // ===================
                       // class MapComparator
                       // ===================
 
template <class KEY, class VALUE, class COMPARATOR>
#ifdef BSLS_PLATFORM_CMP_MSVC
// Visual studio compiler fails to resolve the conversion operator in
// 'bslalg::FunctorAdapter_FunctionPointer' when using private inheritance.
// Below is a workaround until a more suitable way the resolve this issue can
// be found.
class MapComparator : public bslalg::FunctorAdapter<COMPARATOR>::Type {
#else
class MapComparator : private bslalg::FunctorAdapter<COMPARATOR>::Type {
#endif
    // This class overloads the function-call operator to compare a referenced
    // 'bslalg::RbTreeNode' object with a object of the parameterized 'KEY'
    // type, assuming the reference to 'bslalg::RbTreeNode' is a base of a
    // 'bslstl::TreeNode' holding a 'pair<KEY, VALUE>', using a functor of the
    // parameterized 'COMPARATOR' type.
 
  private:
    // This class does not support assignment.
 
    MapComparator& operator=(const MapComparator&);  // Declared but not
                                                     // defined
 
  public:
    // TYPES
 
    /// This alias represents the type of the values held by nodes in an
    /// `bslalg::RbTree` object.
    typedef bsl::pair<const KEY, VALUE>  ValueType;
 
    /// This alias represents the type of node holding a `ValueType` object.
    typedef TreeNode<ValueType> NodeType;
 
    // CREATORS
 
    /// Create a `MapComparator` object that will use a default constructed
    /// `COMPARATOR`.
    MapComparator();
 
    /// Create a `MapComparator` object holding a copy of the specified
    /// `keyComparator`.
    explicit MapComparator(const COMPARATOR& keyComparator);
 
     MapComparator(const MapComparator& original) = default;
        // Create a 'MapComparator' object with the 'COMPARATOR' object of the
        // specified 'original' object.
 
     ~MapComparator() = default;
        // Destroy this object.
 
    // MANIPULATORS
 
    /// Return `true` if the specified `lhs` is less than (ordered before,
    /// according to the comparator held by this object) `value().first` of
    /// the specified `rhs` after being cast to `NodeType`, and `false` otherwise.  
    /// 
    /// \pre The behavior is undefined   unless `rhs` can be safely
    /// cast to `NodeType`.
    template <class LOOKUP_KEY>
    bool operator()(const LOOKUP_KEY&         lhs,
                    const bslalg::RbTreeNode& rhs);
 
    /// Return `true` if `value().first()` of the specified `lhs` after
    /// being cast to `NodeType` is less than (ordered before, according to
    /// the comparator held by this object) the specified `rhs`, and `false` otherwise.  
    /// 
    /// \pre The behavior is undefined   unless `rhs` can be safely
    /// cast to `NodeType`.
    template <class LOOKUP_KEY>
    bool operator()(const bslalg::RbTreeNode& lhs,
                    const LOOKUP_KEY&         rhs);
 
    /// Efficiently exchange the value of this object with the value of the
    /// specified `other` object.  This method provides the no-throw
    /// exception-safety guarantee.
    void swap(MapComparator& other);
 
    // ACCESSORS
 
    /// Return `true` if the specified `lhs` is less than (ordered before,
    /// according to the comparator held by this object) `value().first` of
    /// the specified `rhs` after being cast to `NodeType`, and `false` otherwise.  
    /// 
    /// \pre The behavior is undefined   unless `rhs` can be safely
    /// cast to `NodeType`.
    template <class LOOKUP_KEY>
    bool operator()(const LOOKUP_KEY&         lhs,
                    const bslalg::RbTreeNode& rhs) const;
 
    /// Return `true` if `value().first()` of the specified `lhs` after
    /// being cast to `NodeType` is less than (ordered before, according to
    /// the comparator held by this object) the specified `rhs`, and `false` otherwise.  
    /// 
    /// \pre The behavior is undefined   unless `rhs` can be safely
    /// cast to `NodeType`.
    template <class LOOKUP_KEY>
    bool operator()(const bslalg::RbTreeNode& lhs,
                    const LOOKUP_KEY&         rhs) const;
 
    /// Return a reference providing modifiable access to the function
    /// pointer or functor to which this comparator delegates comparison
    /// operations.
    COMPARATOR& keyComparator();
 
    /// Return a reference providing non-modifiable access to the function
    /// pointer or functor to which this comparator delegates comparison
    /// operations.
    const COMPARATOR& keyComparator() const;
};
 
// FREE FUNCTIONS
 
/// Efficiently exchange the values of the specified `a` and `b` objects.
/// This function provides the no-throw exception-safety guarantee.
template <class KEY,  class VALUE,  class COMPARATOR>
void swap(MapComparator<KEY, VALUE, COMPARATOR>& a,
          MapComparator<KEY, VALUE, COMPARATOR>& b);
 
// ============================================================================
//                  TEMPLATE AND INLINE FUNCTION DEFINITIONS
// ============================================================================
 
                    // -------------------
                    // class MapComparator
                    // -------------------
 
// CREATORS
template <class KEY, class VALUE, class COMPARATOR>
inline
MapComparator<KEY, VALUE, COMPARATOR>::MapComparator()
: bslalg::FunctorAdapter<COMPARATOR>::Type()
{
}
 
template <class KEY, class VALUE, class COMPARATOR>
inline
MapComparator<KEY, VALUE, COMPARATOR>::
MapComparator(const COMPARATOR& valueComparator)
: bslalg::FunctorAdapter<COMPARATOR>::Type(valueComparator)
{
}
 
// MANIPULATORS
template <class KEY, class VALUE, class COMPARATOR>
inline
void MapComparator<KEY, VALUE, COMPARATOR>::swap(
                                  MapComparator<KEY, VALUE, COMPARATOR>& other)
{
    bslalg::SwapUtil::swap(
      static_cast<typename bslalg::FunctorAdapter<COMPARATOR>::Type*>(this),
      static_cast<typename bslalg::FunctorAdapter<COMPARATOR>::Type*>(
                                                  BSLS_UTIL_ADDRESSOF(other)));
}
 
// ACCESSOR
template <class KEY, class VALUE, class COMPARATOR>
template <class LOOKUP_KEY>
inline
bool MapComparator<KEY, VALUE, COMPARATOR>::operator()(
                                                 const LOOKUP_KEY&         lhs,
                                                 const bslalg::RbTreeNode& rhs)
{
    return keyComparator()(lhs,
                           static_cast<const NodeType&>(rhs).value().first);
}
 
template <class KEY, class VALUE, class COMPARATOR>
template <class LOOKUP_KEY>
inline
bool MapComparator<KEY, VALUE, COMPARATOR>::operator()(
                                           const LOOKUP_KEY&         lhs,
                                           const bslalg::RbTreeNode& rhs) const
{
    return keyComparator()(lhs,
                           static_cast<const NodeType&>(rhs).value().first);
}
 
template <class KEY, class VALUE, class COMPARATOR>
template <class LOOKUP_KEY>
inline
bool MapComparator<KEY, VALUE, COMPARATOR>::operator()(
                                                 const bslalg::RbTreeNode& lhs,
                                                 const LOOKUP_KEY&         rhs)
{
    return keyComparator()(static_cast<const NodeType&>(lhs).value().first,
                           rhs);
}
 
template <class KEY, class VALUE, class COMPARATOR>
template <class LOOKUP_KEY>
inline
bool MapComparator<KEY, VALUE, COMPARATOR>::operator()(
                                           const bslalg::RbTreeNode& lhs,
                                           const LOOKUP_KEY&         rhs) const
{
    return keyComparator()(static_cast<const NodeType&>(lhs).value().first,
                           rhs);
}
 
template <class KEY, class VALUE, class COMPARATOR>
inline
COMPARATOR&
MapComparator<KEY, VALUE, COMPARATOR>::keyComparator()
{
    return *this;
}
 
template <class KEY, class VALUE, class COMPARATOR>
inline
const COMPARATOR&
MapComparator<KEY, VALUE, COMPARATOR>::keyComparator() const
{
    return *this;
}
 
 
// FREE FUNCTIONS
template <class KEY,  class VALUE,  class COMPARATOR>
void swap(MapComparator<KEY, VALUE, COMPARATOR>& a,
          MapComparator<KEY, VALUE, COMPARATOR>& b)
{
    a.swap(b);
}
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2013 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */