bslalg_rbtreeutil.h

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/// @file bslalg_rbtreeutil.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslalg_rbtreeutil.h                                                -*-C++-*-
#ifndef INCLUDED_BSLALG_RBTREEUTIL
#define INCLUDED_BSLALG_RBTREEUTIL
 
#include <bsls_ident.h>
BSLS_IDENT("$Id$ $CSID$")
 
/// @defgroup bslalg_rbtreeutil bslalg_rbtreeutil
/// @brief  Provide a suite of primitive algorithms on red-black trees.
/// @addtogroup bsl
/// @{
/// @addtogroup bslalg
/// @{
/// @addtogroup bslalg_rbtreeutil
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslalg_rbtreeutil-purpose"> Purpose</a>
/// * <a href="#bslalg_rbtreeutil-classes"> Classes </a>
/// * <a href="#bslalg_rbtreeutil-description"> Description </a>
///   * <a href="#bslalg_rbtreeutil-summary"> Summary </a>
///     * <a href="#bslalg_rbtreeutil-navigation"> Navigation </a>
///     * <a href="#bslalg_rbtreeutil-modification"> Modification </a>
///     * <a href="#bslalg_rbtreeutil-utility"> Utility </a>
///     * <a href="#bslalg_rbtreeutil-testing"> Testing </a>
///   * <a href="#bslalg_rbtreeutil-well-formed-rbtreeanchor-objects"> Well-Formed RbTreeAnchor Objects </a>
///     * <a href="#bslalg_rbtreeutil-the-sentinel-node"> The Sentinel Node </a>
///   * <a href="#bslalg_rbtreeutil-usage"> Usage </a>
///     * <a href="#bslalg_rbtreeutil-example-1-creating-and-using-a-tree-with-rbtreeutil"> Example 1: Creating and Using a Tree with RbTreeUtil </a>
///     * <a href="#bslalg_rbtreeutil-example-2-implementing-a-set-of-integers"> Example 2: Implementing a Set of Integers </a>
///
/// # Purpose {#bslalg_rbtreeutil-purpose}
/// Provide a suite of primitive algorithms on red-black trees.
///
/// # Classes {#bslalg_rbtreeutil-classes}
///
/// -  bslalg::RbTreeUtil: namespace for red-black tree functions
/// -  bslalg::RbTreeUtilTreeProctor: proctor to manage all nodes in a tree
///
/// @see  bslalg_rbtreenode
///
/// # Description {#bslalg_rbtreeutil-description}
/// This component provides a variety of algorithms that operate
/// on nodes forming a red-black binary search tree.
///
/// This implementation is adapted from Cormen, Leiserson, Rivest,
/// "Introduction to Algorithms" [MIT Press, 1997].
///
/// ## Summary {#bslalg_rbtreeutil-summary}
///
///
/// The following section provides a short synopsis describing observable
/// behavior of functions supplied in this component.  See the full
/// function-level contract for detailed description.
///
/// ### Navigation {#bslalg_rbtreeutil-navigation}
///
///
/// The following algorithms search a tree for a value, or iterate over the
/// nodes in a tree:
/// @code
/// leftmost            Return the leftmost node.
///
/// rightmost           Return the rightmost node.
///
/// next                Return the next node in an in-order traversal.
///
/// previous            Return the previous node in an in-order traversal.
///
/// find                Find the node with the supplied value.
///
/// lowerBound          Find the first node not less-than the supplied value.
///
/// upperBound          Find the first node greater than the supplied value.
/// @endcode
///
/// ### Modification {#bslalg_rbtreeutil-modification}
///
///
/// The following algorithms are used in the process of manipulating the
/// structure of a tree:
/// @code
/// copyTree            Return a deep-copy of the supplied tree.
///
/// deleteTree          Delete all the nodes of the supplied tree.
///
/// findInsertLocation  Find the location where a value may be inserted.
///
/// findUniqueInsertLocation
///                     Find the location where a unique value may be inserted.
///
/// insert              Insert the supplied node into the tree.
///
/// insertAt            Insert the supplied node at the indicated position.
///
/// remove              Remove the supplied node from the tree.
///
/// swap                Swap the contents of two trees.
/// @endcode
///
/// ### Utility {#bslalg_rbtreeutil-utility}
///
///
/// The following algorithms are typically used when implementing higher-level
/// algorithms (and are not generally used by clients):
/// @code
/// isLeftChild         Return 'true' if the supplied node is a left child.
///
/// isRightChild        Return 'true' if the supplied node is a right child.
///
/// rotateLeft          Perform a counter-clockwise rotation on a node.
///
/// rotateRight         Perform a clockwise rotation on a node.
/// @endcode
///
/// ### Testing {#bslalg_rbtreeutil-testing}
///
///
/// The following algorithms are used for testing and debugging, and
/// generally should not be used in production code:
/// @code
/// printTreeStructure  Print, to a file, the structure of the supplied tree.
///
/// validateRbTree      Indicate if a tree is a valid red-black tree.
///
/// isWellFormed        Indicate if the 'RbTreeAnchor' object is well-formed.
/// @endcode
///
/// ## Well-Formed RbTreeAnchor Objects {#bslalg_rbtreeutil-well-formed-rbtreeanchor-objects}
///
///
/// Many of the algorithms defined in this component operate over a complete
/// tree of nodes, rather than a (possible) subtree referred to through a
/// pointer to a node.  These operations refer to a complete tree through a
/// `RbTreeAnchor` object, which maintains references to the first, root, and
/// sentinel nodes for the tree, as well as a count of the number of nodes in
/// the tree.  `RbTreeAnchor` objects supplied to `RbTreeUtil` are frequently
/// required to meet a series of constraints that are not enforced by the
/// `RbTreeAnchor` type itself.  An `RbTreeAnchor` object meeting these
/// constraints is said to be "well-formed", and `RbTreeUtil::isWellFormed`
/// will return `true` for such an object.  A `RbTreeAnchor` object is
/// considered well-formed if all of the following are true:
///
/// 1. The root node refers to a valid red-black tree (see `validateRbTree`).
/// 2. The first node refers to the leftmost node in the tree, or the sentinel
///    node if the tree is empty.
/// 3. The node count is the number of nodes in the tree (not counting the
///    sentinel node).
/// 4. The sentinel node refers to the root node as its left child, and the
///    root node refers to the sentinel as its parent.
/// 5. The root node is either 0 or is colored black.
///
/// The manipulation functions of `RbTreeUtil` guarantee that these properties
/// are maintained for any supplied tree.  Note that `RbTreeUtil::isWellFormed`
/// has linear complexity with respect to the number of nodes in the tree, and
/// is typically used for debugging and testing purposes only.  Note also that
/// the final condition, that the root node be either 0 or colored black, is
/// not a canonical requirement of a red-black tree but an additional invariant
/// enforced by the methods of `RbTreeUtil` to simplify the implementations.
///
/// ### The Sentinel Node {#bslalg_rbtreeutil-the-sentinel-node}
///
///
/// The sentinel node is `RbTreeNode` object (unique to an `RbTreeAnchor`
/// instance) which does not have a value, and provides a fixed end-point for
/// navigation over the tree (which is distinct from the `rightmost` node of
/// that tree).  The sentinel node will be returned by `next` if the supplied
/// node is the rightmost node in the tree, as well as by search operations
/// when no nodes meet the supplied search-criteria.  In addition, the sentinel
/// node may be supplied as a `hint` to `findInsertLocation` and
/// `findUniqueInsertLocation`, as well as supplied to `previous` to obtain the
/// rightmost node of a (non-empty) tree.
///
/// ## Usage {#bslalg_rbtreeutil-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Creating and Using a Tree with RbTreeUtil {#bslalg_rbtreeutil-example-1-creating-and-using-a-tree-with-rbtreeutil}
///
///
/// This example demonstrates how to create a tree of integers using
/// `RbTreeUtil`.
///
/// First, we define a type `SimpleIntNode` that will represent a nodes in our
/// tree of integer values.  `SimpleIntNode` contains an `int` payload, and
/// inherits from `RbTreeNode`, allowing it to be operated on by
/// `RbTreeUtil`.
/// @code
/// struct SimpleIntNode : public RbTreeNode {
///     int d_value;
/// };
/// @endcode
/// Then, we define a comparison function for `SimpleIntNode` objects (note
/// that we static-cast `RBTreeNode` objects to the actual node type,
/// `SimpleIntNode`, for comparison purposes):
/// @code
/// struct SimpleIntNodeValueComparator {
///     // This class defines a comparator providing comparison operations
///     // between 'SimpleIntNode' objects, and 'int' values.
///
///     bool operator()(const RbTreeNode& lhs, int rhs) const
///     {
///         return static_cast<const SimpleIntNode&>(lhs).d_value < rhs;
///     }
///
///     bool operator()(int lhs, const RbTreeNode& rhs) const
///     {
///         return lhs < static_cast<const SimpleIntNode&>(rhs).d_value;
///     }
/// };
///
/// @endcode
/// Next, we begin to define the example function that will build a tree of
/// nodes holding integer values:
/// @code
/// void createTestTreeExample()
/// {
/// @endcode
/// Then, within this function, we define a `RbTreeAnchor` object that will
/// hold the root, first, last, and sentinel nodes of tree, as well a count of
/// the number of nodes in the tree:
/// @code
///     RbTreeAnchor tree;
/// @endcode
/// Next, we define an array of 5 `SimpleIntNode` objects that we will insert
/// into the tree; in practice, nodes are more often allocated on the heap (see
/// example 2):
/// @code
///     const int NUM_NODES = 5;
///     SimpleIntNode nodes[NUM_NODES];
/// @endcode
/// Then, we assign unique values to each of the `nodes`:
/// @code
///     for (int i = 0; i < NUM_NODES; ++i) {
///         nodes[i].d_value = i;
///     }
/// @endcode
/// Now, for each node in the tree, we use `RbTreeUtil` to first find the
/// location at which the node should be inserted, and then insert that node
/// into the tree:
/// @code
///     for (int i = 0; i < NUM_NODES; ++i) {
///         int comparisonResult;
///         SimpleIntNodeValueComparator comparator;
///         RbTreeNode *insertLocation = RbTreeUtil::findUniqueInsertLocation(
///                                             &comparisonResult,
///                                             &tree,
///                                             comparator,
///                                             nodes[i].d_value);
///         BSLS_ASSERT(comparisonResult);
///         RbTreeUtil::insertAt(&tree,
///                              insertLocation,
///                              comparisonResult < 0,
///                              &nodes[i]);
///     }
/// @endcode
/// And verify the resulting `tree` holds 5 nodes, and the first node has
/// the value 0:
/// @code
///     assert(5 == tree.numNodes());
///     assert(0 == static_cast<SimpleIntNode *>(tree.firstNode())->d_value);
/// @endcode
/// Finally, we use `RbTreeUtil` to iterate through the nodes of `tree`, and
/// write the value of each node to the console:
/// @code
///     const RbTreeNode *nodeIterator = tree.firstNode();
///     while (tree.sentinel() != nodeIterator) {
///         printf("Node value: %d\n",
///                static_cast<const SimpleIntNode *>(nodeIterator)->d_value);
///         nodeIterator = RbTreeUtil::next(nodeIterator);
///     }
/// }
/// @endcode
/// Notice that each of the `RbTreeNode` objects must be @ref static_cast  to the
/// derived type, `SimpleIntNode`, in order to access their values.
///
/// The resulting output is displayed on the console:
/// @code
/// Node value: 0
/// Node value: 1
/// Node value: 2
/// Node value: 3
/// Node value: 4
/// @endcode
///
/// ### Example 2: Implementing a Set of Integers {#bslalg_rbtreeutil-example-2-implementing-a-set-of-integers}
///
///
/// This example demonstrates how to use `RbTreeUtil` to implement a simple
/// container holding a set of (unique) integer values as a red-black binary
/// search tree.
///
/// Before defining the `IntSet` class, we need to define a series of
/// associated helper types:
/// 1. The node-type, for the nodes in the tree.
/// 2. An iterator, for iterating over nodes in the tree.
/// 3. A comparison functor for comparing nodes and values.
/// 4. A factory for creating and destroying nodes.
///
/// First, we define a type, `IntSet_Node`, that will represent the nodes in our
/// tree of integer values; it contains an `int` payload, and inherits from
/// `RbTreeNode`, allowing it to be operated on by `RbTreeUtil` (note that the
/// underscore "_" indicates that this type is a private implementation type of
/// `IntSet`, and not for use by clients of `IntSet`):
/// @code
/// class IntSet_Node : public RbTreeNode {
///     // A red-black tree node containing an integer data-value.
///
///     // DATA
///     int d_value;  // actual value represented by the node
///
///   public:
///     // MANIPULATORS
///     int& value() { return d_value; }
///         // Return a reference providing modifiable access to the 'value' of
///         // this object.
///
///     // ACCESSORS
///     const int& value() const { return d_value; }
///         // Return a reference providing non-modifiable access to the
///         // 'value' of this object.
/// };
/// @endcode
/// Then, we define a iterator over `IntSet_Node` objects.  We use the `next`
/// function of `RbTreeUtil` to increment the iterator (note that, for
/// simplicity, this iterator is *not* a fully STL compliant iterator
/// implementation):
/// @code
/// class IntSetConstIterator {
///     // This class defines an STL-style iterator over a non-modifiable tree
///     // of 'IntSet_Node' objects.
///
///     // DATA
///     const RbTreeNode *d_node_p;  // current location of this iterator
///
///   public:
///     IntSetConstIterator() : d_node_p(0) {}
///         // Create an iterator that does not refer to a node.
///
///     IntSetConstIterator(const RbTreeNode *node) : d_node_p(node) {}
///         // Create an iterator referring to the specified 'node'.
///
/// //  IntSetConstIterator(const IntSetConstIterator&) = default;
///
///     // MANIPULATOR
/// //  IntSetConstIterator& operator=(const IntSetConstIterator&) = default;
///
/// @endcode
/// Here, we implement the prefix-increment operator using the `next` function
/// of 'RbTreeUtil:
/// @code
///     IntSetConstIterator& operator++()
///        // Advance this iterator to the subsequent value it the 'IntSet',
///        // and return a reference providing modifiable access to this
///        // iterator.   The behavior is undefined unless this iterator
///        // refers to a element in an 'IntSet'.
///     {
///         d_node_p = RbTreeUtil::next(d_node_p);
///         return *this;
///     }
///
///     // ACCESSORS
///     const int& operator*() const
///         // Return a reference providing non-modifiable access to the value
///         // referred to by this iterator.
///     {
///         return static_cast<const IntSet_Node *>(d_node_p)->value();
///     }
///
///     const int *operator->() const
///         // Return an address providing non-modifiable access to the value
///         // referred to by this iterator.
///     {
///         return &(static_cast<const IntSet_Node *>(d_node_p)->value());
///     }
///
///     const IntSet_Node *nodePtr() const
///         // Return the address of the non-modifiable int-set node referred
///         // to by this iterator
///     {
///         return static_cast<const IntSet_Node *>(d_node_p);
///     }
/// };
///
/// // FREE OPERATORS
/// bool operator==(const IntSetConstIterator &lhs,
///                 const IntSetConstIterator &rhs)
///     // Return 'true' if the 'lhs' and 'rhs' objects have the same value,
///     // and 'false' otherwise.  Two 'IntSetConstIterator' objects have the
///     // same value if they refer to the same node.
/// {
///     return lhs.nodePtr() == rhs.nodePtr();
/// }
///
/// bool operator!=(const IntSetConstIterator &lhs,
///                 const IntSetConstIterator &rhs)
///     // Return 'true' if the specified 'lhs' and 'rhs' objects do not have
///     // the same value, and 'false' otherwise.  Two 'IntSetConstIterator'
///     // objects do not have the same value if they refer to different nodes.
/// {
///     return lhs.nodePtr() != rhs.nodePtr();
/// }
/// @endcode
/// Next, we define a comparison functor for `IntSet_Node` objects, which will
/// be supplied to `RbTreeUtil` functions that must compare nodes with values
/// -- i.e., those with a `NODE_VALUE_COMPARATOR` template parameter (e.g.,
/// `find` and `findInsertLocation`):
/// @code
/// struct IntSet_NodeValueComparator {
///     // This class defines a comparator providing comparison operations
///     // between 'IntSet_Node' objects, and 'int' values.
///
///     bool operator()(const RbTreeNode& lhs, int rhs) const
///     {
///         return static_cast<const IntSet_Node&>(lhs).value() < rhs;
///     }
///
///     bool operator()(int lhs, const RbTreeNode& rhs) const
///     {
///         return lhs < static_cast<const IntSet_Node&>(rhs).value();
///     }
/// };
/// @endcode
/// Notice that we static-cast `RbTreeNode` objects to the actual node type,
/// `IntSet_Node` for comparison.
///
/// Next, we define a factory for creating and destroying `IntSet_Node`
/// objects.  This factory provides the operations `createNode` and
/// `deleteNode`.  These operations will be used directly by our container
/// implementation, and they are also required by `RbTreeUtil` functions taking
/// a `FACTORY` template parameter (e.g., `copyTree` and `deleteTree`):
/// @code
/// class IntSet_NodeFactory {
///     // This class defines a creator object, that when invoked, creates a
///     // new 'IntSet_Node' (either from a int value, or an existing
///     // 'IntSet_Node' object) using the allocator supplied at construction.
///
///     bslma::Allocator *d_allocator_p;  // allocator, (held, not owned)
///
///   public:
///
///     IntSet_NodeFactory(bslma::Allocator *allocator)
///     : d_allocator_p(allocator)
///     {
///         BSLS_ASSERT_SAFE(allocator);
///     }
///
///     RbTreeNode *createNode(int value) const
///     {
///         IntSet_Node *newNode = new (*d_allocator_p) IntSet_Node;
///         newNode->value() = value;
///         return newNode;
///     }
///
///     RbTreeNode *createNode(const RbTreeNode& node) const
///     {
///         IntSet_Node *newNode = new (*d_allocator_p) IntSet_Node;
///         newNode->value() = static_cast<const IntSet_Node&>(node).value();
///         return newNode;
///     }
///     void deleteNode(RbTreeNode *node) const
///     {
///         d_allocator_p->deleteObject(static_cast<IntSet_Node *>(node));
///     }
///
///     bslma::Allocator *allocator() const
///     {
///         return d_allocator_p;
///     }
/// };
/// @endcode
/// Then, having defined the requisite helper types, we define the public
/// interface for our `IntSet` type.  Note that for the purposes of
/// illustrating the use of `RbTreeUtil` a number of simplifications have been
/// made.  For example, this implementation provides only a minimal set of
/// critical operations, and it does not use the empty base-class optimization
/// for the comparator, etc.  We define the interface of `IntSet` as follows:
/// @code
/// class IntSet {
///     // This class implements a set of (unique) 'int' values.
///
///     // DATA
///     RbTreeAnchor           d_tree;         // root, first, and last tree
///                                            // nodes
///
///     IntSet_NodeValueComparator
///                            d_comparator;   // comparison functor for ints
///
///     IntSet_NodeFactory     d_nodeFactory;  // factory for creating and
///                                            // destroying nodes
///
///     // FRIENDS
///     friend bool operator==(const IntSet& lhs, const IntSet& rhs);
///
///   public:
///     // PUBLIC TYPES
///     typedef IntSetConstIterator const_iterator;
///
///     // CREATORS
///     IntSet(bslma::Allocator *basicAllocator = 0);
///         // Create a empty 'IntSet'.  Optionally specify a 'basicAllocator'
///         // used to supply memory.  If 'basicAllocator' is 0, the currently
///         // installed default allocator is used.
///
///     IntSet(const IntSet& original, bslma::Allocator *basicAllocator = 0);
///         // Create a 'IntSet' object having the same value as the specified
///         // 'original' object.  If 'basicAllocator' is 0, the currently
///         // installed default allocator is used.
///
///     ~IntSet();
///         // Destroy this object.
///
///     // MANIPULATORS
///     IntSet& operator=(const IntSet& rhs);
///         // Assign to this object the value of the specified 'rhs' object,
///         // and return a reference providing modifiable access to this
///         // object.
///
///     const_iterator insert(int value);
///         // If the specified 'value' is not already a member of this set,
///         // insert it into this set, returning an iterator referring to the
///         // newly added value, and return an iterator referring to the
///         // existing instance of 'value' in this set, with no other effect,
///         // otherwise.
///
///     const_iterator erase(const_iterator iterator);
///         // Remove the value referred to by the specified 'iterator' from
///         // this set, and return an iterator referring to the value
///         // subsequent to 'iterator' (prior to its removal).  The behavior
///         // is undefined unless 'iterator' refers to a valid value in this
///         // set.
///
///     void clear();
///         // Remove all the elements from this set.
///
///     void swap(IntSet& other);
///         // Efficiently exchange the value of this object with the value of
///         // the specified 'other' object.
///
///     // ACCESSORS
///     const_iterator begin() const;
///         // Return an iterator referring leftmost node value in this set, or
///         // 'end()' if this set is empty.
///
///     const_iterator end() const;
///         // Return an iterator referring to the value one past the
///         // rightmost value in this set.
///
///     const_iterator find(int value) const;
///         // Return a iterator referring to the specified 'value' in this
///         // set, or 'end()' if 'value' is not a member of this set.
///
///     int size() const;
///         // Return the number of elements in this set.
/// };
///
/// // FREE OPERATORS
/// bool operator==(const IntSet& lhs, const IntSet& rhs);
///     // Return 'true' if the 'lhs' and 'rhs' objects have the same value,
///     // and 'false' otherwise.  Two 'IntSet' objects have the same value if
///     // they contain the same number of elements, and if for each element
///     // in 'lhs' there is a corresponding element in 'rhs' with the same
///     // value.
///
/// bool operator!=(const IntSet& lhs, const IntSet& rhs);
///     // Return 'true' if the specified 'lhs' and 'rhs' objects do not have
///     // the same value, and 'false' otherwise.  Two 'IntSet' objects do not
///     // have the same value if they differ in the number of elements they
///     // contain, or if for any element in 'lhs' there is not a
///     // corresponding element in 'rhs' with the same value.
/// @endcode
/// Now, we implement the methods of `IntSet` using `RbTreeUtil` and the
/// helper types we defined earlier:
/// @code
/// // CREATORS
/// IntSet::IntSet(bslma::Allocator *basicAllocator)
/// : d_tree()
/// , d_comparator()
/// , d_nodeFactory(bslma::Default::allocator(basicAllocator))
/// {
/// }
///
/// IntSet::IntSet(const IntSet& original, bslma::Allocator *basicAllocator)
/// : d_tree()
/// , d_comparator()
/// , d_nodeFactory(bslma::Default::allocator(basicAllocator))
/// {
///     if (original.d_tree.rootNode()) {
///         RbTreeUtil::copyTree(&d_tree, original.d_tree, &d_nodeFactory);
///     }
/// }
///
/// IntSet::~IntSet()
/// {
///     clear();
/// }
///
/// // MANIPULATORS
/// IntSet& IntSet::operator=(const IntSet& rhs)
/// {
///     IntSet temp(rhs, d_nodeFactory.allocator());
///     swap(temp);
///     return *this;
/// }
///
/// @endcode
/// Here, we implement `insert` by using the `RbTreeUtil` algorithms
/// `findUniqueInsertLocation` and `insertAt`:
/// @code
/// IntSet::const_iterator IntSet::insert(int value)
/// {
///     // To insert a value into the tree, we first find the location where
///     // the node would be added, and whether 'value' is unique.  If 'value'
///     // is not unique we do not want to incur the expense of allocating
///     // memory for a node.
///
///     int comparisonResult;
///     RbTreeNode *insertLocation =
///                   RbTreeUtil::findUniqueInsertLocation(&comparisonResult,
///                                                        &d_tree,
///                                                        d_comparator,
///                                                        value);
///     if (0 == comparisonResult) {
///         // 'value' already exists in 'd_tree'.
///
///         return const_iterator(insertLocation);                    // RETURN
///     }
///
///     // If 'value' is unique, we create a new node and supply it to
///     // 'insertAt', along with the tree location returned by
///     // 'findUniqueInsertLocation'.
///
///     RbTreeNode *newNode = d_nodeFactory.createNode(value);
///     RbTreeUtil::insertAt(&d_tree,
///                          insertLocation,
///                          comparisonResult < 0,
///                          newNode);
///     return const_iterator(newNode);
/// }
///
/// IntSet::const_iterator IntSet::erase(const_iterator iterator)
/// {
///     BSLS_ASSERT(iterator.nodePtr());
///     IntSet_Node *node = const_cast<IntSet_Node *>(iterator.nodePtr());
///
///     // Before removing the node, we first find the subsequent node to which
///     // we will return an iterator.
///
///     RbTreeNode *next = RbTreeUtil::next(node);
///     RbTreeUtil::remove(&d_tree, node);
///     d_nodeFactory.deleteNode(node);
///     return const_iterator(next);
/// }
///
/// void IntSet::clear()
/// {
///     if (d_tree.rootNode()) {
///         RbTreeUtil::deleteTree(&d_tree, &d_nodeFactory);
///     }
/// }
///
/// void IntSet::swap(IntSet& other) {
///     BSLS_ASSERT(d_nodeFactory.allocator() ==
///                 other.d_nodeFactory.allocator());
///     RbTreeUtil::swap(&d_tree, &other.d_tree);
/// }
///
/// // ACCESSORS
/// IntSet::const_iterator IntSet::begin() const
/// {
///     return const_iterator(d_tree.firstNode());
/// }
///
/// IntSet::const_iterator IntSet::end() const
/// {
///     return const_iterator(d_tree.sentinel());
/// }
///
/// IntSet::const_iterator IntSet::find(int value) const
/// {
///     return const_iterator(RbTreeUtil::find(d_tree, d_comparator, value));
/// }
///
/// int IntSet::size() const
/// {
///     return d_tree.numNodes();
/// }
/// @endcode
/// Finally, we implement the free operators on `IntSet`:
/// @code
/// // FREE OPERATORS
/// bool operator==(const IntSet& lhs, const IntSet& rhs)
/// {
///     return bslalg::RangeCompare::equal(lhs.begin(),
///                                       lhs.end(),
///                                       lhs.size(),
///                                       rhs.begin(),
///                                       rhs.end(),
///                                       rhs.size());
/// }
///
/// bool operator!=(const IntSet& lhs, const IntSet& rhs)
/// {
///     return !(lhs == rhs);
/// }
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslalg
 * @{
 */
/** @addtogroup bslalg_rbtreeutil
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslalg_rbtreeanchor.h>
#include <bslalg_rbtreenode.h>
 
#include <bslma_allocatortraits.h>
 
#include <bslmf_movableref.h>
 
#include <bsls_assert.h>
 
#include <stdio.h>
 
 
namespace bslalg {
 
                        // ================
                        // class RbTreeUtil
                        // ================
 
/// This `struct` provides a namespace for a suite of utility functions that
/// operate on elements of type `RbTreeNode`.
///
/// Each method of this class, other than `copyTree`, provides the
/// *no-throw* exception guarantee if the client-supplied comparator
/// provides the no-throw guarantee, and provides the *strong* guarantee
/// otherwise (see @ref bsldoc_glossary ).  `copyTree` provides the *strong*
/// guarantee.
struct RbTreeUtil {
 
    // CLASS METHODS
                                 // Navigation
 
    /// Return the address of the leftmost node in the specified `subtree`,
    /// and `subtree` if `subtree` has no left child.  The behavior is
    /// undefined unless `0 != subtree`, and `subtree` refers to a valid
    /// binary tree.  Note that the value held by the returned node will not
    /// compare greater than that of any other node in `subtree` (as
    /// determined by the comparator used to organize the red-black subtree
    /// data).
    static const RbTreeNode *leftmost(const RbTreeNode *subtree);
    static       RbTreeNode *leftmost(      RbTreeNode *subtree);
 
    /// Return the address of the rightmost node in the specified
    /// `subtree`, and `subtree` if `subtree` has no right child.  The
    /// behavior is undefined unless `0 != subtree` and `subtree` refers to
    /// a valid binary tree.  Note that the value held by the returned node
    /// will not compare less than that of any other node in `subtree` (as
    /// determined by the comparator used to organize the red-black subtree
    /// data).
    static const RbTreeNode *rightmost(const RbTreeNode *subtree);
    static       RbTreeNode *rightmost(      RbTreeNode *subtree);
 
    /// Return the address of the node that follows the specified `node` in
    /// an in-order traversal of the binary tree to which `node` belongs, or
    /// the tree's sentinel node if `node` is the rightmost node in the
    /// tree.  The behavior is undefined unless `node` is a member of a
    /// valid binary tree, and is not a sentinel node.  Note that if the
    /// tree does not contain duplicate values, then the returned node will
    /// have the smallest value greater than that of `node`.
    static const RbTreeNode *next(const RbTreeNode *node);
    static       RbTreeNode *next(      RbTreeNode *node);
 
    /// Return the address of the node that precedes the specified `node` in
    /// an in-order traversal of the binary tree to which `node` belongs, or
    /// the tree's rightmost node if `node` is the sentinel node of the
    /// tree.  The behavior is undefined unless or `node` is a non-leftmost
    /// member of a valid binary tree or is a sentinel `node`.  Note that if
    /// the tree does not contain duplicate values, then the returned node
    /// will have the largest value less than that of `node`.
    static const RbTreeNode *previous(const RbTreeNode *node);
    static       RbTreeNode *previous(      RbTreeNode *node);
 
                                 // Search
 
    /// Return the address of the leftmost node holding the specified
    /// `value` in the specified `tree` (organized according to the
    /// specified `comparator) if found, and return `tree.sentinel()'
    /// otherwise.  `COMPARATOR` shall be a functor providing two methods
    /// that can be called as if they had the following signatures:
    /// @code
    /// bool operator()(const RbTreeNode&, const VALUE&) const;
    /// bool operator()(const VALUE&, const RbTreeNode&) const;
    /// @endcode
    /// The behavior is undefined unless `comparator` provides a strict
    /// weak ordering on objects of type `VALUE`, and `tree` is well-formed
    /// (see `isWellFormed`).
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static const RbTreeNode *find(const RbTreeAnchor&    tree,
                                  NODE_VALUE_COMPARATOR& comparator,
                                  const VALUE&           value);
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static       RbTreeNode *find(RbTreeAnchor&          tree,
                                  NODE_VALUE_COMPARATOR& comparator,
                                  const VALUE&           value);
 
    /// Return the address of the leftmost node holding the smallest
    /// value greater-than or equal-to `value` in the specified `tree`
    /// (organized according to the specified 'comparator) if found, and
    /// return `tree.sentinel()` if `value` is greater-than the rightmost
    /// node in `tree`.  `COMPARATOR` shall be a functor providing two
    /// methods that can be called as if they had the following signatures:
    /// @code
    /// bool operator()(const RbTreeNode&, const VALUE&) const;
    /// bool operator()(const VALUE&, const RbTreeNode&) const;
    /// @endcode
    /// The behavior is undefined unless `comparator` provides a strict
    /// weak ordering on objects of type `VALUE`, and `tree` is well-formed
    /// (`isWellFormed`).   Note that this function returns the *first*
    /// position before which `value` could be inserted into `tree` while
    /// preserving its ordering.
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static const RbTreeNode *lowerBound(const RbTreeAnchor&    tree,
                                        NODE_VALUE_COMPARATOR& comparator,
                                        const VALUE&           value);
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static       RbTreeNode *lowerBound(RbTreeAnchor&         tree,
                                        NODE_VALUE_COMPARATOR& comparator,
                                        const VALUE&           value);
 
    /// Return the address of the leftmost node holding the smallest
    /// value greater-than `value` in the specified `tree` (organized
    /// according to the specified 'comparator) if found, and return
    /// `tree.sentinel()` if `value` is greater-than or equal-to the
    /// rightmost node in `tree`.  `COMPARATOR` shall be a functor
    /// providing two methods that can be called as if they had the
    /// following signatures:
    /// @code
    /// bool operator()(const RbTreeNode&, const VALUE&) const;
    /// bool operator()(const VALUE&, const RbTreeNode&) const;
    /// @endcode
    /// The behavior is undefined unless `comparator` provides a strict
    /// weak ordering on objects of type `VALUE`, and `tree` is well-formed
    /// (`isWellFormed`).   Note that this function returns the *last*
    /// position before which `value` could be inserted into `tree` while
    /// preserving its ordering.
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static const RbTreeNode *upperBound(const RbTreeAnchor&    tree,
                                        NODE_VALUE_COMPARATOR& comparator,
                                        const VALUE&           value);
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static       RbTreeNode *upperBound(RbTreeAnchor&          tree,
                                        NODE_VALUE_COMPARATOR& comparator,
                                        const VALUE&           value);
 
                                 // Modification
 
    /// Load, into the specified `result`, a collection of newly created
    /// nodes having the same red-black tree structure as that of the
    /// specified `original` tree, where each node in the returned tree is
    /// created by invoking `nodeFactory->createNode` on the corresponding
    /// `original` node; if an exception occurs, use
    /// `nodeFactory->deleteNode` to destroy any newly created nodes, and
    /// propagate the exception to the caller (i.e., this operation provides
    /// the *strong* exception guarantee).  `FACTORY` shall be a class
    /// providing two methods that can be called as if they had the
    /// following signatures:
    /// @code
    /// RbTreeNode *createNode(const RbTreeNode&);
    /// void deleteNode(RbTreeNode *);
    /// @endcode
    /// The behavior is undefined unless `result` is an empty tree,
    /// `original` is a well-formed (see `isWellFormed`), and
    /// `nodeFactory->deleteNode` does not throw.
    template <class FACTORY>
    static void copyTree(RbTreeAnchor        *result,
                         const RbTreeAnchor&  original,
                         FACTORY             *nodeFactory);
 
    /// Load into the specified `result`, using the specified `nodeFactory`
    /// to create and delete nodes, a collection of newly created nodes with
    /// the same (red-black) tree structure as that of the specified
    /// `original` tree, which uses the specified `originalNodeFactory` to
    /// create and delete nodes, where the `value` attribute of each node in
    /// `result` is constructed from explicitly moving the `value` attribute
    /// of the corresponding node in `original`.  `original` is left in a
    /// valid but unspecified state.  If an exception occurs, both `result`
    /// and `original` are left in a valid but unspecified state.  The
    /// behavior is undefined unless `result` is an empty tree,  `original`
    /// is well-formed (see `isWellFormed`), and `nodeFactory->deleteNode`
    /// and `originalNodeFactory->deleteNode` do not throw.
    template <class FACTORY>
    static void moveTree(RbTreeAnchor *result,
                         RbTreeAnchor *original,
                         FACTORY      *nodeFactory,
                         FACTORY      *originalNodeFactory);
 
    /// Call `nodeFactory->deleteNode` on each node in `tree` and reset
    /// `tree` to an empty state.  `FACTORY` shall be a class providing a
    /// method that can be called as if it has the following signature:
    /// @code
    /// void deleteNode(RbTreeNode *);
    /// @endcode
    /// The behavior is undefined unless `tree` is a valid binary tree, and
    /// `nodeFactory->deleteNode` does not throw.
    template <class FACTORY>
    static void deleteTree(RbTreeAnchor *tree, FACTORY *nodeFactory);
 
    /// Return the address of the node that would be the parent a node
    /// holding the specified `value`, if it were to be inserted into the
    /// specified `tree` (organized according to the specified
    /// `comparator`), and load, into the specified `insertAsLeftChildFlag`,
    /// `true` if `value` would be held as the returned node's left child,
    /// and `false` if `value` would be held in its right child, unless
    /// `tree` is empty, in which case return `tree->sentinel()` and load
    /// `true` into `insertAsLeftChildFlag`.  Optionally specify a `hint`,
    /// suggesting a node in `tree` that might be the immediate successor of
    /// a node holding `value` if it were to be inserted into `tree`.  If
    /// the supplied `hint` is the successor, this operation will take
    /// amortized constant time; otherwise, it will take O(log(N))
    /// operations, where N is the number of nodes in the tree.  If a node
    /// holding `value` is inserted as suggested by this method, the
    /// resulting tree will be an ordered binary tree, but may require
    /// rebalancing (and re-coloring) to again be a valid red-black tree.
    /// `COMPARATOR` shall be a functor providing two methods that can be
    /// called as if they have the following signatures:
    /// @code
    /// bool operator()(const RbTreeNode&, const VALUE&) const;
    /// bool operator()(const VALUE&, const RbTreeNode&) const;
    /// @endcode
    /// The behavior is undefined unless `comparator` provides a strict
    /// weak ordering on objects of type `VALUE`, `tree` is well-formed
    /// (see `isWellFormed`), and `hint`, if supplied, is a node in `tree`.
    /// Note that this operation is intended to be used in conjunction with
    /// the `insertAt` method.
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static RbTreeNode *findInsertLocation(
                                 bool                   *insertAsLeftChildFlag,
                                 RbTreeAnchor           *tree,
                                 NODE_VALUE_COMPARATOR&  comparator,
                                 const VALUE&            value);
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static RbTreeNode *findInsertLocation(
                                 bool                   *insertAsLeftChildFlag,
                                 RbTreeAnchor           *tree,
                                 NODE_VALUE_COMPARATOR&  comparator,
                                 const VALUE&            value,
                                 RbTreeNode             *hint);
 
    /// Return the address of the node holding the specified `value` in the
    /// specified `tree` (organized according to the specified `comparator`)
    /// if found, and the address of the node that would be the parent for
    /// `value` otherwise; load, into the specified `comparisonResult`, 0 if
    /// `value` is found, a negative number if `value` would be held in its
    /// left child, and a positive number if `value` would be held in its
    /// right child, unless `tree` is empty, in which case load a negative
    /// number into `comparisonResult` and return `tree->sentinel()`.
    /// Optionally specify a `hint`, suggesting a node in `tree` that might
    /// be the immediate successor of a node holding `value` if it were to
    /// be inserted into `tree`.  If the supplied `hint` is the successor,
    /// this operation will take amortized constant time; otherwise, it will
    /// take O(log(N)) operations, where N is the number of nodes in the
    /// tree.  If a node holding `value` is inserted as suggested by this
    /// method, the resulting tree will be an ordered binary tree, but may
    /// require rebalancing (and re-coloring) to again be a valid red-black
    /// tree.  `COMPARATOR` shall be a functor providing two methods that
    /// can be called as if they have the following signatures:
    /// @code
    /// bool operator()(const RbTreeNode&, const VALUE&) const;
    /// bool operator()(const VALUE&, const RbTreeNode&) const;
    /// @endcode
    /// The behavior is undefined unless `comparator` provides a strict
    /// weak ordering on objects of type `VALUE`, `tree` is well-formed
    /// (see `isWellFormed`), and `hint`, if supplied, is a node in `tree`.
    /// Note that this operation is intended to be used in conjunction with
    /// the `insertAt` method.
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static RbTreeNode *findUniqueInsertLocation(
                                      int                    *comparisonResult,
                                      RbTreeAnchor           *tree,
                                      NODE_VALUE_COMPARATOR&  comparator,
                                      const VALUE&            value);
    template <class NODE_VALUE_COMPARATOR, class VALUE>
    static RbTreeNode *findUniqueInsertLocation(
                                      int                    *comparisonResult,
                                      RbTreeAnchor           *tree,
                                      NODE_VALUE_COMPARATOR&  comparator,
                                      const VALUE&            value,
                                      RbTreeNode             *hint);
 
    /// Insert the specified `newNode` into the specified `tree`, organized
    /// according to the specified `comparator`.  The resulting tree will
    /// be well-formed (see `isWellFormed`).  `NODE_COMPARATOR` shall be a
    /// functor providing a method that can be called as if it had the
    /// following signatures:
    /// @code
    /// bool operator()(const RbTreeNode&, const RbTreeNode&) const;
    /// @endcode
    /// The behavior is undefined unless `comparator` provides a strict
    /// weak ordering on objects of type `VALUE`, and `tree` is well-formed
    /// (see `isWellFormed`).
    template <class NODE_COMPARATOR>
    static void insert(RbTreeAnchor           *tree,
                       const NODE_COMPARATOR&  comparator,
                       RbTreeNode             *newNode);
 
    /// Insert the specified `newNode` into the specified `tree` as either
    /// the left or right child of the specified `parentNode`, as indicated
    /// by the specified `leftChildFlag`, and then rebalance the tree so
    /// that it is a valid red-black tree (see `validateRbTree`).  The
    /// behavior is undefined unless `tree` is well-formed (see
    /// `isWellFormed`), and, if `tree` is empty, `parentNode` is
    /// `tree->sentinel()` and `leftChildFlag` is `true`, or, if `tree` is
    /// not empty, `parentNode` is a node in `tree` whose left or right
    /// child (as indicated by `leftChildFlag`) is 0 where if `newNode` were
    /// attached as that child (without rebalancing) `tree` would still
    /// form an ordered binary tree (though not necessarily a valid
    /// red-black tree).  Note that this operation is intended to be used in
    /// conjunction with the `findInsertLocation` or
    /// `findUniqueInsertLocation` methods.
    static void insertAt(RbTreeAnchor *tree,
                         RbTreeNode   *parentNode,
                         bool          leftChildFlag,
                         RbTreeNode   *newNode);
 
    /// Remove the specified `node` from the specified `tree`, and then
    /// rebalance `tree` so that it again forms a valid red-black tree (see
    /// `validateRbTree`).  The behavior is undefined unless `tree` is
    /// well-formed (see `isWellFormed`).
    static void remove(RbTreeAnchor *tree, RbTreeNode *node);
 
    /// Efficiently exchange the nodes in the specified `a` tree with the
    /// nodes in the specified `b` tree.  This method provides the no-throw
    /// exception-safety guarantee.  The behavior is undefined unless `a`
    /// and `b` are well-formed (see `isWellFormed`).
    static void swap(RbTreeAnchor *a, RbTreeAnchor *b);
 
                                 // Utility
 
    /// Return `true` if the specified `node` is the left child of its
    /// parent, and `false` otherwise.  The behavior is undefined unless
    /// `0 != node->parent()`.
    static bool isLeftChild(const RbTreeNode *node);
 
    /// Return `true` if the specified `node` is the left child of its
    /// parent, and `false` otherwise.  The behavior is undefined unless
    /// `0 != node->parent()`.
    static bool isRightChild(const RbTreeNode *node);
 
    /// Perform counter-clockwise rotation on the specified `node`: Rotate
    /// the node's right child (the pivot) to be the node's parent, and
    /// attach the pivot's left child as the node's right child.
    /// @code
    ///    (node)              (pivot)
    ///    /    \              /     \.
    ///   a   (pivot)  --->  (node)   c
    ///        /   \         /    \.
    ///       b     c       a      b
    /// @endcode
    /// The behavior is undefined unless `node->rightChild()` is not 0,
    /// `node->parent()` is not 0, and node's parent refers to `node` as one
    /// of its children.  Note that this operation maintains the ordering
    /// of the subtree rooted at `node`.  Also note this operation will
    /// successfully rotate the root node of an unbalanced, but otherwise
    /// well-formed, tree referred to by a `RbTreeAnchor` object (see
    /// `isWellFormed`) because the parent of the root node is the tree's
    /// sentinel node (i.e., not 0), which refers to the root node as its
    /// left child, and an `RbTreeAnchor` object returns the left child of
    /// the sentinel node as the root of the tree.
    static void rotateLeft(RbTreeNode *node);
 
    /// Perform clockwise rotation on the specified `node`: Rotate the
    /// node's left child (the pivot) to be the node's parent, and attach
    /// the pivot's right child as the node's left child.
    /// @code
    ///      (node)            (pivot)
    ///      /    \            /     \.
    ///  (pivot)   c   --->   a     (node)
    ///   /  \                      /    \.
    ///  a    b                    b      c
    /// @endcode
    /// The behavior is undefined unless `node->leftChild()` is not 0,
    /// `node->parent()` is not 0, and node's parent refers to `node` as one
    /// of its children.  Note that this operation maintains the ordering
    /// of the subtree rooted at `node`.  Also note this operation will
    /// successfully rotate the root node of an unbalanced, but otherwise
    /// well-formed, tree referred to by a `RbTreeAnchor` object (see
    /// `isWellFormed`) because the parent of the root node is the tree's
    /// sentinel node (i.e., not 0), which refers to the root node as its
    /// left child, and an `RbTreeAnchor` object returns the left child of
    /// the sentinel node as the root of the tree.
    static void rotateRight(RbTreeNode *node);
 
                                 // Testing
 
    /// Write a description of the structure of the specified `subtree` to
    /// the specified output `file` in a human-readable format, using the
    /// specified `printValueCallback` to render the value of each node.
    /// Optionally specify an initial indentation `level`, whose absolute
    /// value is incremented recursively for nested objects.  If `level` is
    /// specified, optionally specify `spacesPerLevel`, whose absolute value
    /// indicates the number of spaces per indentation level for this and
    /// all of its nested objects.  If `level` is negative, suppress
    /// indentation of the first line.  If `spacesPerLevel` is negative,
    /// format the entire output on one line, suppressing all but the
    /// initial indentation (as governed by `level`).  The behavior
    /// is undefined unless `node` is 0, or the root of a valid binary
    /// tree.  Note that the implementation of this function is recursive
    /// and expensive to perform, it is intended for debugging purposes
    /// only.  Also note that the format is not fully specified, and can
    /// change without notice.
    static void printTreeStructure(
                    FILE                   *file,
                    const RbTreeNode       *subtree,
                    void (*printNodeValueCallback)(FILE *, const RbTreeNode *),
                    int                     level = 0,
                    int                     spacesPerLevel = 4);
 
    /// Return the (common) number of black nodes on each path from the
    /// specified `rootNode` to a leaf in the tree, 0 if `rootNode` is 0,
    /// and a negative number if `rootNode` does not refer to a valid
    /// red-black binary search tree, ordered according to the specified
    /// `comparator`.  Optionally specify `errorNode` and `errorDescription`
    /// in which to load the address of a node violating a red-black tree
    /// constraint and a description of that violation, respectively.  The
    /// behavior is undefined unless `rootNode` is 0, or refers to a valid
    /// binary tree.
    ///
    /// Each node of a red-black tree is colored either red or black; null
    /// nodes are considered black.  Four requirements must be satisfied
    /// for `rootNode` to refer to a valid red-black binary search tree:
    ///
    /// 1. For each node in the tree, no descendents to the left of that
    ///    node would order after that node (according to the `comparator`),
    ///    and no descendents to the right of that node would order before
    ///    it.
    /// 2. For each node in the tree, each non-null child of that node
    ///    refers to that node as its parent.
    /// 3. If a node in the tree is colored red, all its children are
    ///    colored black or are null (which is considered black).
    /// 4. For each node in the tree, every path from that node to a leaf
    ///    contains the same number of black nodes, where null children are
    ///    considered black leaf nodes.
    ///
    /// The behavior is undefined unless `rootNode` is 0, or refers to a
    /// valid binary tree.  Note that the implementation of this function
    /// is recursive and has linear complexity with respect to the number of
    /// nodes in `tree`, it is intended for debugging purposes only.
    template <class NODE_COMPARATOR>
    static int validateRbTree(const RbTreeNode       *rootNode,
                              const NODE_COMPARATOR&  comparator);
    template <class NODE_COMPARATOR>
    static int validateRbTree(const RbTreeNode       **errorNode,
                              const char             **errorDescription,
                              const RbTreeNode        *rootNode,
                              const NODE_COMPARATOR&   comparator);
 
    /// Return `true` if the specified `tree` is well-formed and refers to
    /// a valid red-black tree, and `false` otherwise.  For a
    /// `RbTreeAnchor` to be considered well-formed *all* of the following
    /// must be true:
    ///
    /// 1. `tree.rootNode()` must refer to a valid red-black tree, whose
    ///    nodes are organized according to `comparator` (see
    ///    `validateRbTree`).
    /// 2. `tree.firstNode()` must refer to `tree.sentinel()` if
    ///    `tree.rootNode()` is 0, and leftmost(tree.rootNode())' otherwise.
    /// 3. `tree.nodeCount()` must be the count of nodes in `tree` (not
    ///    including the sentinel node).
    /// 4. `tree.sentinel()->leftchild()` is `tree.rootNode()`, and (if
    ///    `tree.rootNode()` is not 0) `tree.rootNode()->parent()` is
    ///    `tree.sentinel()`.
    /// 5. `tree.rootNode()` is 0 or `tree.rootNode().isBlack()` is `true`
    ///
    /// The behavior is undefined unless `tree.rootNode()` is 0 or refers
    /// to a valid binary tree.  Note that the implementation of this
    /// function is recursive and has linear complexity with respect to the
    /// number of nodes in `tree`, it is intended for debugging purposes
    /// only.  Note also that the final condition, that the root node be
    /// either 0 or colored black, is not a canonical requirement of a
    /// red-black tree but an additional invariant enforced by the methods
    /// of `RbTreeUtil` to simplify the implementations.
    template <class NODE_COMPARATOR>
    static bool isWellFormed(const RbTreeAnchor&    tree,
                             const NODE_COMPARATOR& comparator);
};
 
                      // ==========================
                      // class RbTreeUtil_Validator
                      // ==========================
 
/// This `struct` provides a namespace for auxiliary functions used to
/// validate a red-black binary search tree.
struct RbTreeUtil_Validator {
 
    // CLASS METHODS
 
    /// Return the (common) number of black nodes on each path from the
    /// specified `rootNode` to a leaf in the tree, 0 if `rootNode` is 0,
    /// and a negative number if `rootNode` does not refer to a valid
    /// red-black binary search tree (ordered according to the specified
    /// `comparator`) that contains no nodes whose value is less than the
    /// specified `minNodeValue` (if not 0) or greater-than the specified
    /// `maxNodeValue` (if not 0).  If `rootNode` does not refer to a valid
    /// red-black tree containing nodes whose values are between the
    /// specified `minNodeValue` and `maxNodeValue` (inclusively) then load
    /// `errorNode` and `errorDescription` with the address of a node
    /// violating a red-black tree constraint and a description of that
    /// violation, respectively.  The behavior is undefined unless
    /// `rootNode` is 0, or refers to a valid binary tree.
    template <class NODE_COMPARATOR>
    static int validateRbTree(const RbTreeNode       **errorNode,
                              const char             **errorDescription,
                              const RbTreeNode        *rootNode,
                              const RbTreeNode        *minNodeValue,
                              const RbTreeNode        *maxNodeValue,
                              const NODE_COMPARATOR&   comparator);
 
    /// Return `true` if the specified `tree` is well-formed, without
    /// confirming that it refers to a valid-red-black tree, and
    /// `false` otherwise.  This method will return `true` if *all* of the
    /// following are true:
    ///
    /// 1. `tree.firstNode()` must refer to `tree.sentinel()` if
    ///    `tree.rootNode()` is 0, and leftmost(tree.rootNode())' otherwise.
    /// 2. `tree.nodeCount()` must be the count of nodes in `tree` (not
    ///    including the sentinel node).
    /// 3. `tree.sentinel()->leftchild()` is `tree.rootNode()`, and (if
    ///    `tree.rootNode()` is not 0), `tree.rootNode()->parent()` is
    ///    'tree.sentinel().
    /// 4. `tree.rootNode()` is 0 or `tree.rootNode().isBlack()` is `true`
    ///
    /// The behavior is undefined unless `tree.rootNode()` is 0, or refers
    /// to a valid binary tree.  Note that this function provides a
    /// non-templatized implementation for several criteria of a
    /// well-formed tree (but not the complete set verified by
    /// `RbTreeUtil::isWellFormed`).
    static bool isWellFormedAnchor(const RbTreeAnchor& tree);
};
 
                        // ============================
                        // struct RbTreeUtilTreeProctor
                        // ============================
 
/// This class implements a proctor that, unless `release` is called,
/// invokes the parameterized `DELETER` on each node in the tree supplied at
/// construction.
///
/// See @ref bslalg_rbtreeutil 
template <class DELETER>
class RbTreeUtilTreeProctor {
 
    // DATA
    RbTreeAnchor *d_tree_p;     // address of root node (held, not owned)
 
    DELETER      *d_deleter_p;  // address of deleter used to destroy each
                                // node (held, not owned)
 
  public:
    // CREATORS
 
    /// Create a proctor object that, unless `release` is called, will,
    /// on destruction, invoke the specified `deleter` on each node in
    /// `tree`.
    RbTreeUtilTreeProctor(RbTreeAnchor *tree, DELETER *deleter);
 
    /// Unless `release` has been called, invoke the deleter supplied at
    /// construction on each node in the tree supplied at construction.
    ~RbTreeUtilTreeProctor();
 
    // MANIPULATORS
 
    /// Release from management the tree supplied at construction.
    void release();
};
 
// ============================================================================
//                      INLINE FUNCTION DEFINITIONS
// ============================================================================
 
                        // ----------------
                        // class RbTreeUtil
                        // ----------------
 
// CLASS METHODS
inline
RbTreeNode *RbTreeUtil::leftmost(RbTreeNode *subtree)
{
    return const_cast<RbTreeNode *>(
                            leftmost(const_cast<const RbTreeNode *>(subtree)));
}
 
inline
RbTreeNode *RbTreeUtil::rightmost(RbTreeNode *subtree)
{
    return const_cast<RbTreeNode *>(
                           rightmost(const_cast<const RbTreeNode *>(subtree)));
}
 
inline
RbTreeNode *RbTreeUtil::next(RbTreeNode *node)
{
    return const_cast<RbTreeNode *>(
                                   next(const_cast<const RbTreeNode *>(node)));
}
 
inline
RbTreeNode *RbTreeUtil::previous(RbTreeNode *node)
{
    return const_cast<RbTreeNode *>(
                               previous(const_cast<const RbTreeNode *>(node)));
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
inline
RbTreeNode *RbTreeUtil::find(RbTreeAnchor&          tree,
                             NODE_VALUE_COMPARATOR& comparator,
                             const VALUE&           value)
{
    return const_cast<RbTreeNode *>(
               find(const_cast<const RbTreeAnchor&>(tree), comparator, value));
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
inline
const RbTreeNode *RbTreeUtil::find(const RbTreeAnchor&    tree,
                                   NODE_VALUE_COMPARATOR& comparator,
                                   const VALUE&           value)
{
    const RbTreeNode *lowBound = lowerBound(tree, comparator, value);
 
    // Note that a Solaris compiler bug prevents using a ternary ('?:')
    // operator here in certain contexts.
 
    if (lowBound != tree.sentinel() && !comparator(value, *lowBound)) {
        return lowBound;                                              // RETURN
    }
    return tree.sentinel();
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
RbTreeNode *RbTreeUtil::lowerBound(RbTreeAnchor&          tree,
                                   NODE_VALUE_COMPARATOR& comparator,
                                   const VALUE&           value)
{
    return const_cast<RbTreeNode *>(
         lowerBound(const_cast<const RbTreeAnchor&>(tree), comparator, value));
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
inline
const RbTreeNode *RbTreeUtil::lowerBound(const RbTreeAnchor&    tree,
                                         NODE_VALUE_COMPARATOR& comparator,
                                         const VALUE&           value)
{
    const RbTreeNode *nextLargestNode = tree.sentinel();
    const RbTreeNode *node            = tree.rootNode();
    while (node) {
        if (comparator(*node, value)) {
            node = node->rightChild();
        }
        else {
            nextLargestNode = node;
            node = node->leftChild();
        }
    }
    return nextLargestNode;
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
inline
RbTreeNode *RbTreeUtil::upperBound(RbTreeAnchor&          tree,
                                   NODE_VALUE_COMPARATOR& comparator,
                                   const VALUE&           value)
{
    return const_cast<RbTreeNode *>(
        upperBound(const_cast<const RbTreeAnchor&>(tree), comparator, value));
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
inline
const RbTreeNode *RbTreeUtil::upperBound(const RbTreeAnchor&    tree,
                                         NODE_VALUE_COMPARATOR& comparator,
                                         const VALUE&           value)
{
    const RbTreeNode *nextLargestNode = tree.sentinel();
    const RbTreeNode *node            = tree.rootNode();
    while (node) {
        if (comparator(value, *node)) {
            nextLargestNode = node;
            node = node->leftChild();
        }
        else {
            node = node->rightChild();
        }
    }
    return nextLargestNode;
}
 
template <class FACTORY>
void RbTreeUtil::copyTree(RbTreeAnchor        *result,
                          const RbTreeAnchor&  original,
                          FACTORY             *nodeFactory)
{
    BSLS_ASSERT_SAFE(result);
    BSLS_ASSERT_SAFE(0 == result->rootNode());
    BSLS_ASSERT_SAFE(nodeFactory);
 
    if (!original.rootNode()) {
        result->reset(0, result->sentinel(), 0);
        return;                                                       // RETURN
    }
 
    // Perform an pre-order traversal of the nodes of the tree, invoking
    // 'nodeFactory->createNode()' on each node.
 
    const RbTreeNode *originalNode = original.rootNode();
 
    RbTreeNode   *copiedRoot = nodeFactory->cloneNode(*originalNode);
    RbTreeAnchor  tree(copiedRoot, 0, 1);
 
    RbTreeUtilTreeProctor<FACTORY> proctor(&tree, nodeFactory);
 
    RbTreeNode *copiedNode = copiedRoot;
 
    copiedNode->setColor(originalNode->color());
    copiedNode->setParent(result->sentinel());
    copiedNode->setLeftChild(0);
    copiedNode->setRightChild(0);
    do {
        if (0 != originalNode->leftChild() && 0 == copiedNode->leftChild()) {
            originalNode = originalNode->leftChild();
            RbTreeNode *newNode = nodeFactory->cloneNode(*originalNode);
            copiedNode->setLeftChild(newNode);
            newNode->setColor(originalNode->color());
            newNode->setParent(copiedNode);
            newNode->setLeftChild(0);
            newNode->setRightChild(0);
 
            copiedNode = newNode;
        }
        else if (0 != originalNode->rightChild() &&
                 0 == copiedNode->rightChild()) {
            originalNode = originalNode->rightChild();
            RbTreeNode *newNode = nodeFactory->cloneNode(*originalNode);
            copiedNode->setRightChild(newNode);
            newNode->setColor(originalNode->color());
            newNode->setParent(copiedNode);
            newNode->setLeftChild(0);
            newNode->setRightChild(0);
 
            copiedNode = newNode;
        }
        else {
            originalNode = originalNode->parent();
            copiedNode   = copiedNode->parent();
        }
    } while (original.sentinel() != originalNode);
 
    proctor.release();
 
    result->reset(copiedRoot,
                  leftmost(copiedRoot),
                  original.numNodes());
}
 
template <class FACTORY>
void RbTreeUtil::moveTree(RbTreeAnchor *result,
                          RbTreeAnchor *original,
                          FACTORY      *nodeFactory,
                          FACTORY      *originalNodeFactory)
{
    BSLS_ASSERT_SAFE(result);
    BSLS_ASSERT_SAFE(0 == result->rootNode());
    BSLS_ASSERT_SAFE(nodeFactory);
    BSLS_ASSERT_SAFE(originalNodeFactory);
 
    if (!original->rootNode()) {
        result->reset(0, result->sentinel(), 0);
        return;                                                       // RETURN
    }
 
    // Perform an pre-order traversal of the nodes of the tree, invoking
    // 'nodeFactory->createNode()' on each node.
 
    RbTreeNode *originalNode = original->rootNode();
 
    RbTreeNode *copiedRoot = nodeFactory->moveIntoNewNode(originalNode);
 
    RbTreeAnchor  tree(copiedRoot, 0, 1);
 
    RbTreeUtilTreeProctor<FACTORY> proctor(&tree, nodeFactory);
    RbTreeUtilTreeProctor<FACTORY> oproctor(original, originalNodeFactory);
 
    RbTreeNode *copiedNode = copiedRoot;
 
    copiedNode->setColor(originalNode->color());
    copiedNode->setParent(result->sentinel());
    copiedNode->setLeftChild(0);
    copiedNode->setRightChild(0);
    do {
        if (0 != originalNode->leftChild() && 0 == copiedNode->leftChild()) {
            originalNode = originalNode->leftChild();
            RbTreeNode *newNode = nodeFactory->moveIntoNewNode(originalNode);
            copiedNode->setLeftChild(newNode);
            newNode->setColor(originalNode->color());
            newNode->setParent(copiedNode);
            newNode->setLeftChild(0);
            newNode->setRightChild(0);
 
            copiedNode = newNode;
        }
        else if (0 != originalNode->rightChild() &&
                 0 == copiedNode->rightChild()) {
            originalNode = originalNode->rightChild();
            RbTreeNode *newNode = nodeFactory->moveIntoNewNode(originalNode);
            copiedNode->setRightChild(newNode);
            newNode->setColor(originalNode->color());
            newNode->setParent(copiedNode);
            newNode->setLeftChild(0);
            newNode->setRightChild(0);
 
            copiedNode = newNode;
        }
        else {
            originalNode = originalNode->parent();
            copiedNode   = copiedNode->parent();
        }
    } while (original->sentinel() != originalNode);
 
    proctor.release();
 
    result->reset(copiedRoot,
                  leftmost(copiedRoot),
                  original->numNodes());
 
    // 'oproctor' takes care of clearing 'original', even when an exception is
    // not thrown, since the tree is no longer valid if the elements have been
    // moved from.
}
 
template <class FACTORY>
void RbTreeUtil::deleteTree(RbTreeAnchor *tree, FACTORY *nodeFactory)
{
    BSLS_ASSERT_SAFE(tree);
    BSLS_ASSERT_SAFE(nodeFactory);
 
    if (0 == tree->rootNode()) {
        BSLS_ASSERT_SAFE(tree->sentinel() == tree->firstNode());
        return;                                                       // RETURN
    }
 
    // Perform a post-order traversal of the nodes of the tree, invoking
    // 'nodeFactory->deleteNode()' on each node.
 
    RbTreeNode *node = tree->firstNode();
    do {
        // At each iteration through this loop, we are at a leftmost (i.e.,
        // minimum) node of some sub-tree.  Note that 'node->leftChild()' may
        // not be 0 if we've simply deleted the left sub-tree of this node.
 
        if (node->rightChild()) {
            // If this node has a right child, then navigate to the first node
            // in the subtree to remove, and set 'node->rightChild()' to 0 so
            // we know this sub-tree has been removed when we iterate back up
            // parent pointers of the tree to this node.
 
            RbTreeNode *rightChild = node->rightChild();
            node->setRightChild(0);
            node = leftmost(rightChild);
        }
        else {
            RbTreeNode *parent = node->parent();
            nodeFactory->deleteNode(node);
            node = parent;
        }
    } while (tree->sentinel() != node);
    tree->reset(0, tree->sentinel(), 0);
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
RbTreeNode *RbTreeUtil::findInsertLocation(
                                 bool                   *insertAsLeftChildFlag,
                                 RbTreeAnchor           *tree,
                                 NODE_VALUE_COMPARATOR&  comparator,
                                 const VALUE&            value)
{
    BSLS_ASSERT_SAFE(insertAsLeftChildFlag);
    BSLS_ASSERT_SAFE(tree);
 
    RbTreeNode *parent = tree->sentinel();
    RbTreeNode *node   = tree->rootNode();
    *insertAsLeftChildFlag = true;
    while (node) {
        // Find the leaf node that would be the parent of 'newNode'.
 
        parent = node;
        *insertAsLeftChildFlag = comparator(value, *node);
        if (*insertAsLeftChildFlag) {
            node = node->leftChild();
        }
        else {
            node = node->rightChild();
        }
    }
    return parent;
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
RbTreeNode *RbTreeUtil::findInsertLocation(
                                 bool                   *insertAsLeftChildFlag,
                                 RbTreeAnchor           *tree,
                                 NODE_VALUE_COMPARATOR&  comparator,
                                 const VALUE&            value,
                                 RbTreeNode             *hint)
{
    BSLS_ASSERT_SAFE(insertAsLeftChildFlag);
    BSLS_ASSERT_SAFE(tree);
    BSLS_ASSERT_SAFE(hint);
 
    // 'hint' is valid if it is equal to, or the smallest value greater than,
    // 'value'.
 
    if (tree->sentinel() == hint || !comparator(*hint, value)) {
        // 'hint' is greater-than or equal-to 'value', if the previous node,
        // 'prev' is less-than or equal-to 'value', then we have a valid hint.
 
        RbTreeNode *prev = (tree->firstNode() == hint) ? hint : previous(hint);
        if (tree->firstNode() == hint || !comparator(value, *prev)) {
            // There will be an empty position for a child node between every
            // two consecutive nodes (in an in-order traversal) of a binary
            // tree.  Determine whether that empty position is the left child
            // of 'hint' or the right child of 'prev'.
 
            if (0 == hint->leftChild()) {
                *insertAsLeftChildFlag = true;
                return hint;                                          // RETURN
            }
            BSLS_ASSERT_SAFE(prev);
            *insertAsLeftChildFlag = false;
            return prev;                                              // RETURN
        }
        // 'prev' is greater than 'value', so this is not a valid hint.
 
    }
    // If 'hint' was less than 'value', it is not a valid hint.
 
    // The 'hint' is not valid, fall-back and search the entire tree.
 
    return findInsertLocation(insertAsLeftChildFlag, tree, comparator, value);
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
RbTreeNode *RbTreeUtil::findUniqueInsertLocation(
                                      int                    *comparisonResult,
                                      RbTreeAnchor           *tree,
                                      NODE_VALUE_COMPARATOR&  comparator,
                                      const VALUE&            value)
{
    BSLS_ASSERT_SAFE(comparisonResult);
    BSLS_ASSERT_SAFE(tree);
 
    // Note that 'nextSmallestNode' is used, rather than 'nextLargestNode' (as
    // seen in 'upperBound' and 'lowerBound') to avoid an unnecessary
    // negation.
 
    RbTreeNode *parent           = tree->sentinel();
    RbTreeNode *nextSmallestNode = 0;
    RbTreeNode *node             = tree->rootNode();
 
    bool leftChild = true;
    while (node) {
        // Find the leaf node that would be the parent of 'newNode'.
 
        parent = node;
        leftChild = comparator(value, *node);
        if (leftChild) {
            node = node->leftChild();
        }
        else {
            nextSmallestNode = node;
            node = node->rightChild();
        }
    }
 
    if (nextSmallestNode && !comparator(*nextSmallestNode, value)) {
        *comparisonResult = 0;
        return nextSmallestNode;                                      // RETURN
    }
    *comparisonResult = leftChild ? -1 : 1;
    return parent;
}
 
template <class NODE_VALUE_COMPARATOR, class VALUE>
RbTreeNode *RbTreeUtil::findUniqueInsertLocation(
                                      int                    *comparisonResult,
                                      RbTreeAnchor           *tree,
                                      NODE_VALUE_COMPARATOR&  comparator,
                                      const VALUE&            value,
                                      RbTreeNode             *hint)
{
    BSLS_ASSERT_SAFE(comparisonResult);
    BSLS_ASSERT_SAFE(tree);
    BSLS_ASSERT_SAFE(hint);
 
    enum { LEFT_CHILD = -1, NODE_FOUND = 0, RIGHT_CHILD = 1 };
 
    // 'hint' is valid if it is first value greater than 'value' in the tree.
 
    if (tree->sentinel() == hint || comparator(value, *hint)) {
        // 'hint' is greater than 'value'.  If the previous node, 'prev' is
        // less than the value, then we have a valid hint.
 
        RbTreeNode *prev = (tree->firstNode() == hint) ? hint : previous(hint);
        if (tree->firstNode() == hint || comparator(*prev, value)) {
            // There will be an empty position for a child node between every
            // two consecutive nodes (in an in-order traversal) of a binary
            // tree.  Determine whether that empty position is the left child
            // of 'hint' or the right child of 'prev'.
 
            if (0 == hint->leftChild()) {
                *comparisonResult = LEFT_CHILD;
                return hint;                                          // RETURN
            }
 
            BSLS_ASSERT_SAFE(prev);
            *comparisonResult = RIGHT_CHILD;
            return prev;                                              // RETURN
        }
        // 'value' is ordered before 'hint', but 'prev' is not ordered before
        // 'value', so either: (1) 'value' is equal to 'prev' or (2) 'hint' is
        // not a valid hint.  Optimize for (1), by handling it as a special
        // case, as this may reasonably occur using 'upperBound' on 'value' to
        // determine a hint.
 
        if (!comparator(value, *prev)) {
            *comparisonResult = NODE_FOUND;
            return prev;                                              // RETURN
        }
 
        // 'prev' is greater than 'value', so this is not a valid hint.
    }
    // If 'value' is not ordered before 'hint', either: (1) 'value' is equal
    // to 'hint', or (2) 'hint' is not a valid hint.  Optimize for (1).
 
    else if (tree->sentinel() != hint && !comparator(*hint, value)) {
        *comparisonResult = NODE_FOUND;
        return hint;                                                  // RETURN
    }
    // The 'hint' is not valid, fall-back and search the entire tree.
 
    return findUniqueInsertLocation(comparisonResult,
                                    tree,
                                    comparator,
                                    value);
}
 
template <class NODE_COMPARATOR>
void RbTreeUtil::insert(RbTreeAnchor           *tree,
                        const NODE_COMPARATOR&  comparator,
                        RbTreeNode             *newNode)
{
    BSLS_ASSERT_SAFE(tree);
    BSLS_ASSERT_SAFE(newNode);
 
    // Note that the following logic is the same as 'findInsertLocation'
    // except that the comparator required for this operation compares two
    // nodes, rather than comparing a value to a node.
 
    RbTreeNode *parent        = tree->sentinel();
    RbTreeNode *node          = tree->rootNode();
    bool        leftChildFlag = true;
    while (node) {
        // Find the leaf node that would be the parent of 'newNode'.
 
        parent = node;
        leftChildFlag = comparator(*newNode, *node);
        if (leftChildFlag) {
            node = node->leftChild();
        }
        else {
            node = node->rightChild();
        }
    }
    return insertAt(tree, parent, leftChildFlag, newNode);
}
 
inline
bool RbTreeUtil::isLeftChild(const RbTreeNode *node)
{
    BSLS_ASSERT_SAFE(node);
    BSLS_ASSERT_SAFE(node->parent());
 
    return node->parent()->leftChild() == node;
}
 
inline
bool RbTreeUtil::isRightChild(const RbTreeNode *node)
{
    BSLS_ASSERT_SAFE(node);
    BSLS_ASSERT_SAFE(node->parent());
 
    return node->parent()->rightChild() == node;
}
 
template <class NODE_COMPARATOR>
inline
int RbTreeUtil::validateRbTree(const RbTreeNode       *rootNode,
                               const NODE_COMPARATOR&  comparator)
{
    const RbTreeNode *errorNode;
    const char       *errorDescription;
    return validateRbTree(&errorNode, &errorDescription, rootNode, comparator);
}
 
template <class NODE_COMPARATOR>
int RbTreeUtil::validateRbTree(const RbTreeNode       **errorNode,
                               const char             **errorDescription,
                               const RbTreeNode        *rootNode,
                               const NODE_COMPARATOR&   comparator)
{
    BSLS_ASSERT(errorNode);
    BSLS_ASSERT(errorDescription);
 
    return RbTreeUtil_Validator::validateRbTree(errorNode,
                                                errorDescription,
                                                rootNode,
                                                0,
                                                0,
                                                comparator);
}
 
template <class NODE_COMPARATOR>
inline
bool RbTreeUtil::isWellFormed(const RbTreeAnchor&    tree,
                              const NODE_COMPARATOR& comparator)
{
    if (!RbTreeUtil_Validator::isWellFormedAnchor(tree)) {
        return false;                                                 // RETURN
    }
    return 0 <= validateRbTree(tree.rootNode(), comparator);
}
 
                      // --------------------------
                      // class RbTreeUtil_Validator
                      // --------------------------
 
// CLASS METHODS
template <class NODE_COMPARATOR>
int RbTreeUtil_Validator::validateRbTree(
                                     const RbTreeNode       **errorNode,
                                     const char             **errorDescription,
                                     const RbTreeNode        *rootNode,
                                     const RbTreeNode        *minNodeValue,
                                     const RbTreeNode        *maxNodeValue,
                                     const NODE_COMPARATOR&   comparator)
{
    BSLS_ASSERT_SAFE(errorNode);
    BSLS_ASSERT_SAFE(errorDescription);
 
    //: 1 All the descendents to the left of each node are ordered that at or
    //:   before that node, and all descendents to the right of each node are
    //:   ordered at or after that node, as determined by 'comparator'.
    //:
    //: 2 Both children of every node refer to 'node' as a parent.
    //:
    //: 3 If a node in the tree has no children, it is black.
    //:
    //: 4 If a node in the tree is red, its children are either black or 0.
    //:
    //: 5 For each node in the tree, every path from that node to a leaf
    //:   contains the same number of black nodes.
 
    enum { INVALID_RBTREE = -1};
 
    // 'NIL' nodes are considered black
 
    if (!rootNode) {
        return 0;                                                     // RETURN
    }
 
    // Rule 1.
 
    if ((minNodeValue && comparator(*rootNode, *minNodeValue)) ||
        (maxNodeValue && comparator(*maxNodeValue, *rootNode))) {
        *errorNode        = rootNode;
        *errorDescription = "Invalid binary search tree.";
        return INVALID_RBTREE;                                        // RETURN
    }
 
    const RbTreeNode *left  = rootNode->leftChild();
    const RbTreeNode *right = rootNode->rightChild();
    if ((left != 0 || right != 0) && left == right) {
        *errorNode        = rootNode;
        *errorDescription = "Invalid children";
        return INVALID_RBTREE;                                        // RETURN
    }
 
    // Rule 2.
 
    if ((left  && left->parent()  != rootNode) ||
        (right && right->parent() != rootNode)) {
        *errorNode        = rootNode;
        *errorDescription = "Invalid parent pointers for children";
        return INVALID_RBTREE;                                        // RETURN
    }
 
    // Rule 4.
 
    if (RbTreeNode::BSLALG_RED == rootNode->color()) {
        if ((left  && left->color()  != RbTreeNode::BSLALG_BLACK) ||
            (right && right->color() != RbTreeNode::BSLALG_BLACK)) {
            *errorNode        = rootNode;
            *errorDescription = "Red node with a red child.";
            return INVALID_RBTREE;                                    // RETURN
        }
    }
 
    int leftDepth  = validateRbTree(errorNode,
                                    errorDescription,
                                    rootNode->leftChild(),
                                    minNodeValue,
                                    rootNode,
                                    comparator);
    int rightDepth = validateRbTree(errorNode,
                                    errorDescription,
                                    rootNode->rightChild(),
                                    rootNode,
                                    maxNodeValue,
                                    comparator);
 
    if (leftDepth < 0 || rightDepth < 0) {
        return INVALID_RBTREE;                                        // RETURN
    }
 
    // Rule 5.
 
    if (leftDepth != rightDepth) {
        *errorNode        = rootNode;
        *errorDescription =
            "Black violation (unequal black depth from node to leaves).";
        return INVALID_RBTREE;                                        // RETURN
    }
 
    return (rootNode->color() == RbTreeNode::BSLALG_BLACK)
          ? leftDepth + 1
          : leftDepth;
}
 
                        // ----------------------------
                        // struct RbTreeUtilTreeProctor
                        // ----------------------------
 
template <class DELETER>
inline
RbTreeUtilTreeProctor<DELETER>::RbTreeUtilTreeProctor(RbTreeAnchor *tree,
                                                      DELETER      *deleter)
: d_tree_p(tree)
, d_deleter_p(deleter)
{
    BSLS_ASSERT_SAFE(deleter);
}
 
template <class DELETER>
inline
RbTreeUtilTreeProctor<DELETER>::~RbTreeUtilTreeProctor()
{
    if (d_tree_p && d_tree_p->rootNode()) {
        d_tree_p->rootNode()->setParent(d_tree_p->sentinel());
 
        d_tree_p->setFirstNode(RbTreeUtil::leftmost(d_tree_p->rootNode()));
        RbTreeUtil::deleteTree(d_tree_p, d_deleter_p);
    }
}
 
template <class DELETER>
inline
void RbTreeUtilTreeProctor<DELETER>::release()
{
    d_tree_p = 0;
}
 
}  // 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */