.. comment SPDX-License-Identifier: CC-BY-SA-4.0 .. COMMENT: COPYRIGHT (c) 1988-2012. .. COMMENT: On-Line Applications Research Corporation (OAR). .. COMMENT: All rights reserved. .. index:: Red-Black Trees .. index:: rbtrees Red-Black Trees *************** Introduction ============ The Red-Black Tree API is an interface to the SuperCore (score) rbtree implementation. Within RTEMS, red-black trees are used when a binary search tree is needed, including dynamic priority thread queues and non-contiguous heap memory. The Red-Black Tree API provided by RTEMS is: - ``rtems_rtems_rbtree_node`` - Red-Black Tree node embedded in another struct - ``rtems_rtems_rbtree_control`` - Red-Black Tree control node for an entire tree - ``rtems_rtems_rbtree_initialize`` - initialize the red-black tree with nodes - ``rtems_rtems_rbtree_initialize_empty`` - initialize the red-black tree as empty - ``rtems_rtems_rbtree_set_off_tree`` - Clear a node's links - ``rtems_rtems_rbtree_root`` - Return the red-black tree's root node - ``rtems_rtems_rbtree_min`` - Return the red-black tree's minimum node - ``rtems_rtems_rbtree_max`` - Return the red-black tree's maximum node - ``rtems_rtems_rbtree_left`` - Return a node's left child node - ``rtems_rtems_rbtree_right`` - Return a node's right child node - ``rtems_rtems_rbtree_parent`` - Return a node's parent node - ``rtems_rtems_rbtree_are_nodes_equal`` - Are the node's equal ? - ``rtems_rtems_rbtree_is_empty`` - Is the red-black tree empty ? - ``rtems_rtems_rbtree_is_min`` - Is the Node the minimum in the red-black tree ? - ``rtems_rtems_rbtree_is_max`` - Is the Node the maximum in the red-black tree ? - ``rtems_rtems_rbtree_is_root`` - Is the Node the root of the red-black tree ? - ``rtems_rtems_rbtree_find`` - Find the node with a matching key in the red-black tree - ``rtems_rtems_rbtree_predecessor`` - Return the in-order predecessor of a node. - ``rtems_rtems_rbtree_successor`` - Return the in-order successor of a node. - ``rtems_rtems_rbtree_extract`` - Remove the node from the red-black tree - ``rtems_rtems_rbtree_get_min`` - Remove the minimum node from the red-black tree - ``rtems_rtems_rbtree_get_max`` - Remove the maximum node from the red-black tree - ``rtems_rtems_rbtree_peek_min`` - Returns the minimum node from the red-black tree - ``rtems_rtems_rbtree_peek_max`` - Returns the maximum node from the red-black tree - ``rtems_rtems_rbtree_insert`` - Add the node to the red-black tree Background ========== The Red-Black Trees API is a thin layer above the SuperCore Red-Black Trees implementation. A Red-Black Tree is defined by a control node with pointers to the root, minimum, and maximum nodes in the tree. Each node in the tree consists of a parent pointer, two children pointers, and a color attribute. A tree is parameterized as either unique, meaning identical keys are rejected, or not, in which case duplicate keys are allowed. Users must provide a comparison functor that gets passed to functions that need to compare nodes. In addition, no internal synchronization is offered within the red-black tree implementation, thus users must ensure at most one thread accesses a red-black tree instance at a time. Nodes ----- A red-black tree is made up from nodes that orginate from a red-black tree control object. A node is of type ``rtems_rtems_rbtree_node``. The node is designed to be part of a user data structure. To obtain the encapsulating structure users can use the ``RTEMS_CONTAINER_OF`` macro. The node can be placed anywhere within the user's structure and the macro will calculate the structure's address from the node's address. Controls -------- A red-black tree is rooted with a control object. Red-Black Tree control provide the user with access to the nodes on the red-black tree. The implementation does not require special checks for manipulating the root of the red-black tree. To accomplish this the ``rtems_rtems_rbtree_control`` structure is treated as a ``rtems_rtems_rbtree_node`` structure with a ``NULL`` parent and left child pointing to the root. Operations ========== Examples for using the red-black trees can be found in the ``testsuites/sptests/sprbtree01/init.c`` file. Directives ========== .. index:: rbtree doc Documentation for the Red-Black Tree Directives ----------------------------------------------- Source documentation for the Red-Black Tree API can be found in the generated Doxygen output for ``cpukit/sapi``.