76 lines
3.2 KiB
C
76 lines
3.2 KiB
C
/* Sequential list data type implemented by a binary tree.
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Copyright (C) 2006, 2009-2024 Free Software Foundation, Inc.
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Written by Bruno Haible <bruno@clisp.org>, 2006.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Common code of gl_rbtree_list.c and gl_rbtreehash_list.c. */
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/* A red-black tree is a binary tree where every node is colored black or
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red such that
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1. The root is black.
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2. No red node has a red parent.
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Or equivalently: No red node has a red child.
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3. All paths from the root down to any NULL endpoint contain the same
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number of black nodes.
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Let's call this the "black-height" bh of the tree. It follows that every
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such path contains exactly bh black and between 0 and bh red nodes. (The
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extreme cases are a path containing only black nodes, and a path colored
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alternately black-red-black-red-...-black-red.) The height of the tree
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therefore is >= bh, <= 2*bh.
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*/
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/* -------------------------- gl_list_t Data Type -------------------------- */
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/* Color of a node. */
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typedef enum color { BLACK, RED } color_t;
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/* Concrete list node implementation, valid for this file only. */
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struct gl_list_node_impl
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{
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#if WITH_HASHTABLE
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struct gl_hash_entry h; /* hash table entry fields; must be first */
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#endif
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struct gl_list_node_impl *left; /* left branch, or NULL */
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struct gl_list_node_impl *right; /* right branch, or NULL */
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/* Parent pointer, or NULL. The parent pointer is not needed for most
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operations. It is needed so that a gl_list_node_t can be returned
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without memory allocation, on which the functions gl_list_remove_node,
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gl_list_add_before, gl_list_add_after can be implemented. */
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struct gl_list_node_impl *parent;
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color_t color; /* node's color */
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size_t branch_size; /* number of nodes in this branch,
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= branchsize(left)+branchsize(right)+1 */
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const void *value;
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};
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/* Concrete gl_list_impl type, valid for this file only. */
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struct gl_list_impl
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{
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struct gl_list_impl_base base;
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#if WITH_HASHTABLE
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/* A hash table: managed as an array of collision lists. */
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struct gl_hash_entry **table;
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size_t table_size;
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#endif
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struct gl_list_node_impl *root; /* root node or NULL */
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};
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/* A red-black tree of height h has a black-height bh >= ceil(h/2) and
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therefore at least 2^ceil(h/2) - 1 elements. So, h <= 116 (because a tree
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of height h >= 117 would have at least 2^59 - 1 elements, and because even
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on 64-bit machines,
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sizeof (gl_list_node_impl) * (2^59 - 1) > 2^64
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this would exceed the address space of the machine. */
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#define MAXHEIGHT 116
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