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+/* Sequential list data type implemented by a binary tree.
+ Copyright (C) 2006, 2009-2022 Free Software Foundation, Inc.
+ Written by Bruno Haible <bruno@clisp.org>, 2006.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ This file is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* Common code of gl_rbtree_list.c and gl_rbtreehash_list.c. */
+
+/* A red-black tree is a binary tree where every node is colored black or
+ red such that
+ 1. The root is black.
+ 2. No red node has a red parent.
+ Or equivalently: No red node has a red child.
+ 3. All paths from the root down to any NULL endpoint contain the same
+ number of black nodes.
+ Let's call this the "black-height" bh of the tree. It follows that every
+ such path contains exactly bh black and between 0 and bh red nodes. (The
+ extreme cases are a path containing only black nodes, and a path colored
+ alternately black-red-black-red-...-black-red.) The height of the tree
+ therefore is >= bh, <= 2*bh.
+ */
+
+/* -------------------------- gl_list_t Data Type -------------------------- */
+
+/* Color of a node. */
+typedef enum color { BLACK, RED } color_t;
+
+/* Concrete list node implementation, valid for this file only. */
+struct gl_list_node_impl
+{
+#if WITH_HASHTABLE
+ struct gl_hash_entry h; /* hash table entry fields; must be first */
+#endif
+ struct gl_list_node_impl *left; /* left branch, or NULL */
+ struct gl_list_node_impl *right; /* right branch, or NULL */
+ /* Parent pointer, or NULL. The parent pointer is not needed for most
+ operations. It is needed so that a gl_list_node_t can be returned
+ without memory allocation, on which the functions gl_list_remove_node,
+ gl_list_add_before, gl_list_add_after can be implemented. */
+ struct gl_list_node_impl *parent;
+ color_t color; /* node's color */
+ size_t branch_size; /* number of nodes in this branch,
+ = branchsize(left)+branchsize(right)+1 */
+ const void *value;
+};
+
+/* Concrete gl_list_impl type, valid for this file only. */
+struct gl_list_impl
+{
+ struct gl_list_impl_base base;
+#if WITH_HASHTABLE
+ /* A hash table: managed as an array of collision lists. */
+ struct gl_hash_entry **table;
+ size_t table_size;
+#endif
+ struct gl_list_node_impl *root; /* root node or NULL */
+};
+
+/* A red-black tree of height h has a black-height bh >= ceil(h/2) and
+ therefore at least 2^ceil(h/2) - 1 elements. So, h <= 116 (because a tree
+ of height h >= 117 would have at least 2^59 - 1 elements, and because even
+ on 64-bit machines,
+ sizeof (gl_list_node_impl) * (2^59 - 1) > 2^64
+ this would exceed the address space of the machine. */
+#define MAXHEIGHT 116