changeset 40007:31ddfa01e256

rbtree-omap: New module. * lib/gl_rbtree_omap.h: New file. * lib/gl_rbtree_omap.c: New file. * lib/gl_rbtree_ordered.h: Code moved to here from lib/gl_rbtree_oset.c. Parameterize. * lib/gl_rbtree_oset.c: Include gl_rbtree_ordered.h. * modules/rbtree-omap: New file. * modules/rbtree-oset (Files): Add lib/gl_rbtree_ordered.h. (Makefile.am): Add gl_rbtree_ordered.h to lib_SOURCES.
author Bruno Haible <bruno@clisp.org>
date Tue, 11 Dec 2018 20:56:27 +0100
parents 0caeb347e88e
children eb287ca6dd6c
files ChangeLog lib/gl_rbtree_omap.c lib/gl_rbtree_omap.h lib/gl_rbtree_ordered.h lib/gl_rbtree_oset.c modules/rbtree-omap modules/rbtree-oset
diffstat 7 files changed, 939 insertions(+), 759 deletions(-) [+]
line wrap: on
line diff
--- a/ChangeLog	Tue Dec 11 20:56:25 2018 +0100
+++ b/ChangeLog	Tue Dec 11 20:56:27 2018 +0100
@@ -1,5 +1,15 @@
 2018-12-11  Bruno Haible  <bruno@clisp.org>
 
+	rbtree-omap: New module.
+	* lib/gl_rbtree_omap.h: New file.
+	* lib/gl_rbtree_omap.c: New file.
+	* lib/gl_rbtree_ordered.h: Code moved to here from lib/gl_rbtree_oset.c.
+	Parameterize.
+	* lib/gl_rbtree_oset.c: Include gl_rbtree_ordered.h.
+	* modules/rbtree-omap: New file.
+	* modules/rbtree-oset (Files): Add lib/gl_rbtree_ordered.h.
+	(Makefile.am): Add gl_rbtree_ordered.h to lib_SOURCES.
+
 	avltree-omap: New module.
 	* lib/gl_avltree_omap.h: New file.
 	* lib/gl_avltree_omap.c: New file.
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_rbtree_omap.c	Tue Dec 11 20:56:27 2018 +0100
@@ -0,0 +1,75 @@
+/* Ordered map data type implemented by a binary tree.
+   Copyright (C) 2006-2007, 2009-2018 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2018.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "gl_rbtree_omap.h"
+
+#include <stdlib.h>
+
+/* -------------------------- gl_omap_t Data Type -------------------------- */
+
+/* Parameterization of gl_rbtree_ordered.h.  */
+#define CONTAINER_T gl_omap_t
+#define CONTAINER_IMPL gl_omap_impl
+#define CONTAINER_IMPL_BASE gl_omap_impl_base
+#define NODE_IMPL gl_omap_node_impl
+#define NODE_T gl_omap_node_t
+#define NODE_PAYLOAD_FIELDS \
+  const void *key; \
+  const void *value;
+#define NODE_PAYLOAD_PARAMS \
+  const void *key, const void *value
+#define NODE_PAYLOAD_ASSIGN(node) \
+  node->key = key; \
+  node->value = value;
+#define NODE_PAYLOAD_DISPOSE \
+  if (container->base.vdispose_fn != NULL) \
+    container->base.vdispose_fn (node->value); \
+  if (container->base.kdispose_fn != NULL) \
+    container->base.kdispose_fn (node->key);
+
+#include "gl_rbtree_ordered.h"
+
+/* Generic binary tree code.  */
+#include "gl_anytree_omap.h"
+
+/* For debugging.  */
+void
+gl_rbtree_omap_check_invariants (gl_omap_t map)
+{
+  size_t counter = 0;
+  if (map->root != NULL)
+    check_invariants (map->root, NULL, &counter);
+  if (!(map->count == counter))
+    abort ();
+}
+
+const struct gl_omap_implementation gl_rbtree_omap_implementation =
+  {
+    gl_tree_nx_create_empty,
+    gl_tree_size,
+    gl_tree_search,
+    gl_tree_search_atleast,
+    gl_tree_nx_getput,
+    gl_tree_getremove,
+    gl_tree_omap_free,
+    gl_tree_iterator,
+    gl_tree_iterator_next,
+    gl_tree_iterator_free
+  };
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_rbtree_omap.h	Tue Dec 11 20:56:27 2018 +0100
@@ -0,0 +1,34 @@
+/* Ordered map data type implemented by a binary tree.
+   Copyright (C) 2006, 2009-2018 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2018.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _GL_RBTREE_OMAP_H
+#define _GL_RBTREE_OMAP_H
+
+#include "gl_omap.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern const struct gl_omap_implementation gl_rbtree_omap_implementation;
+#define GL_RBTREE_OMAP &gl_rbtree_omap_implementation
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _GL_RBTREE_OMAP_H */
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/gl_rbtree_ordered.h	Tue Dec 11 20:56:27 2018 +0100
@@ -0,0 +1,778 @@
+/* Ordered {set,map} data type implemented by a binary tree.
+   Copyright (C) 2006-2007, 2009-2018 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2006.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* 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.
+ */
+
+/* Color of a node.  */
+typedef enum color { BLACK, RED } color_t;
+
+/* Tree node implementation, valid for this file only.  */
+struct NODE_IMPL
+{
+  struct NODE_IMPL *left;   /* left branch, or NULL */
+  struct 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 NODE_T can be returned without
+     memory allocation, on which the functions <container>_remove_node,
+     <container>_add_before, <container>_add_after can be implemented.  */
+  struct NODE_IMPL *parent;
+  color_t color;                    /* node's color */
+  NODE_PAYLOAD_FIELDS
+};
+typedef struct NODE_IMPL * NODE_T;
+
+/* Concrete CONTAINER_IMPL type, valid for this file only.  */
+struct CONTAINER_IMPL
+{
+  struct CONTAINER_IMPL_BASE base;
+  struct NODE_IMPL *root;           /* root node or NULL */
+  size_t count;                     /* number of nodes */
+};
+
+/* 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 (NODE_IMPL) * (2^59 - 1) > 2^64
+   this would exceed the address space of the machine.  */
+#define MAXHEIGHT 116
+
+/* Rotate left a subtree.
+
+                         B                         D
+                       /   \                     /   \
+                     A       D       -->       B       E
+                            / \               / \
+                           C   E             A   C
+
+   Change the tree structure, update the branch sizes.
+   The caller must update the colors and register D as child of its parent.  */
+static NODE_T
+rotate_left (NODE_T b_node, NODE_T d_node)
+{
+  NODE_T c_node = d_node->left;
+
+  b_node->right = c_node;
+  d_node->left = b_node;
+
+  d_node->parent = b_node->parent;
+  b_node->parent = d_node;
+  if (c_node != NULL)
+    c_node->parent = b_node;
+
+  return d_node;
+}
+
+/* Rotate right a subtree.
+
+                           D                     B
+                         /   \                 /   \
+                       B       E     -->     A       D
+                      / \                           / \
+                     A   C                         C   E
+
+   Change the tree structure, update the branch sizes.
+   The caller must update the colors and register B as child of its parent.  */
+static NODE_T
+rotate_right (NODE_T b_node, NODE_T d_node)
+{
+  NODE_T c_node = b_node->right;
+
+  d_node->left = c_node;
+  b_node->right = d_node;
+
+  b_node->parent = d_node->parent;
+  d_node->parent = b_node;
+  if (c_node != NULL)
+    c_node->parent = d_node;
+
+  return b_node;
+}
+
+/* Ensure the tree is balanced, after an insertion operation.
+   Also assigns node->color.
+   parent is the given node's parent, known to be non-NULL.  */
+static void
+rebalance_after_add (CONTAINER_T container, NODE_T node, NODE_T parent)
+{
+  for (;;)
+    {
+      /* At this point, parent = node->parent != NULL.
+         Think of node->color being RED (although node->color is not yet
+         assigned.)  */
+      NODE_T grandparent;
+      NODE_T uncle;
+
+      if (parent->color == BLACK)
+        {
+          /* A RED color for node is acceptable.  */
+          node->color = RED;
+          return;
+        }
+
+      grandparent = parent->parent;
+      /* Since parent is RED, we know that
+         grandparent is != NULL and colored BLACK.  */
+
+      if (grandparent->left == parent)
+        uncle = grandparent->right;
+      else if (grandparent->right == parent)
+        uncle = grandparent->left;
+      else
+        abort ();
+
+      if (uncle != NULL && uncle->color == RED)
+        {
+          /* Change grandparent from BLACK to RED, and
+             change parent and uncle from RED to BLACK.
+             This makes it acceptable for node to be RED.  */
+          node->color = RED;
+          parent->color = uncle->color = BLACK;
+          node = grandparent;
+        }
+      else
+        {
+          /* grandparent and uncle are BLACK.  parent is RED.  node wants
+             to be RED too.
+             In this case, recoloring is not sufficient.  Need to perform
+             one or two rotations.  */
+          NODE_T *grandparentp;
+
+          if (grandparent->parent == NULL)
+            grandparentp = &container->root;
+          else if (grandparent->parent->left == grandparent)
+            grandparentp = &grandparent->parent->left;
+          else if (grandparent->parent->right == grandparent)
+            grandparentp = &grandparent->parent->right;
+          else
+            abort ();
+
+          if (grandparent->left == parent)
+            {
+              if (parent->right == node)
+                {
+                  /* Rotation between node and parent.  */
+                  grandparent->left = rotate_left (parent, node);
+                  node = parent;
+                  parent = grandparent->left;
+                }
+              /* grandparent and uncle are BLACK.  parent and node want to be
+                 RED.  parent = grandparent->left.  node = parent->left.
+
+                      grandparent              parent
+                         bh+1                   bh+1
+                         /   \                 /   \
+                     parent  uncle    -->   node  grandparent
+                      bh      bh             bh      bh
+                      / \                           / \
+                   node  C                         C  uncle
+                    bh   bh                       bh    bh
+               */
+              *grandparentp = rotate_right (parent, grandparent);
+              parent->color = BLACK;
+              node->color = grandparent->color = RED;
+            }
+          else /* grandparent->right == parent */
+            {
+              if (parent->left == node)
+                {
+                  /* Rotation between node and parent.  */
+                  grandparent->right = rotate_right (node, parent);
+                  node = parent;
+                  parent = grandparent->right;
+                }
+              /* grandparent and uncle are BLACK.  parent and node want to be
+                 RED.  parent = grandparent->right.  node = parent->right.
+
+                    grandparent                    parent
+                       bh+1                         bh+1
+                       /   \                       /   \
+                   uncle  parent     -->   grandparent  node
+                     bh     bh                  bh       bh
+                            / \                 / \
+                           C  node          uncle  C
+                          bh   bh            bh    bh
+               */
+              *grandparentp = rotate_left (grandparent, parent);
+              parent->color = BLACK;
+              node->color = grandparent->color = RED;
+            }
+          return;
+        }
+
+      /* Start again with a new (node, parent) pair.  */
+      parent = node->parent;
+
+      if (parent == NULL)
+        {
+          /* Change node's color from RED to BLACK.  This increases the
+             tree's black-height.  */
+          node->color = BLACK;
+          return;
+        }
+    }
+}
+
+/* Ensure the tree is balanced, after a deletion operation.
+   CHILD was a grandchild of PARENT and is now its child.  Between them,
+   a black node was removed.  CHILD is also black, or NULL.
+   (CHILD can also be NULL.  But PARENT is non-NULL.)  */
+static void
+rebalance_after_remove (CONTAINER_T container, NODE_T child, NODE_T parent)
+{
+  for (;;)
+    {
+      /* At this point, we reduced the black-height of the CHILD subtree by 1.
+         To make up, either look for a possibility to turn a RED to a BLACK
+         node, or try to reduce the black-height tree of CHILD's sibling
+         subtree as well.  */
+      NODE_T *parentp;
+
+      if (parent->parent == NULL)
+        parentp = &container->root;
+      else if (parent->parent->left == parent)
+        parentp = &parent->parent->left;
+      else if (parent->parent->right == parent)
+        parentp = &parent->parent->right;
+      else
+        abort ();
+
+      if (parent->left == child)
+        {
+          NODE_T sibling = parent->right;
+          /* sibling's black-height is >= 1.  In particular,
+             sibling != NULL.
+
+                      parent
+                       /   \
+                   child  sibling
+                     bh    bh+1
+           */
+
+          if (sibling->color == RED)
+            {
+              /* sibling is RED, hence parent is BLACK and sibling's children
+                 are non-NULL and BLACK.
+
+                      parent                       sibling
+                       bh+2                         bh+2
+                       /   \                        /   \
+                   child  sibling     -->       parent    SR
+                     bh    bh+1                  bh+1    bh+1
+                            / \                  / \
+                          SL   SR            child  SL
+                         bh+1 bh+1             bh  bh+1
+               */
+              *parentp = rotate_left (parent, sibling);
+              parent->color = RED;
+              sibling->color = BLACK;
+
+              /* Concentrate on the subtree of parent.  The new sibling is
+                 one of the old sibling's children, and known to be BLACK.  */
+              parentp = &sibling->left;
+              sibling = parent->right;
+            }
+          /* Now we know that sibling is BLACK.
+
+                      parent
+                       /   \
+                   child  sibling
+                     bh    bh+1
+           */
+          if (sibling->right != NULL && sibling->right->color == RED)
+            {
+              /*
+                      parent                     sibling
+                     bh+1|bh+2                  bh+1|bh+2
+                       /   \                      /   \
+                   child  sibling    -->      parent    SR
+                     bh    bh+1                bh+1    bh+1
+                            / \                / \
+                          SL   SR           child  SL
+                          bh   bh             bh   bh
+               */
+              *parentp = rotate_left (parent, sibling);
+              sibling->color = parent->color;
+              parent->color = BLACK;
+              sibling->right->color = BLACK;
+              return;
+            }
+          else if (sibling->left != NULL && sibling->left->color == RED)
+            {
+              /*
+                      parent                   parent
+                     bh+1|bh+2                bh+1|bh+2
+                       /   \                    /   \
+                   child  sibling    -->    child    SL
+                     bh    bh+1               bh    bh+1
+                            / \                     /  \
+                          SL   SR                 SLL  sibling
+                          bh   bh                 bh     bh
+                         /  \                           /   \
+                       SLL  SLR                       SLR    SR
+                       bh    bh                       bh     bh
+
+                 where SLL, SLR, SR are all black.
+               */
+              parent->right = rotate_right (sibling->left, sibling);
+              /* Change sibling from BLACK to RED and SL from RED to BLACK.  */
+              sibling->color = RED;
+              sibling = parent->right;
+              sibling->color = BLACK;
+
+              /* Now do as in the previous case.  */
+              *parentp = rotate_left (parent, sibling);
+              sibling->color = parent->color;
+              parent->color = BLACK;
+              sibling->right->color = BLACK;
+              return;
+            }
+          else
+            {
+              if (parent->color == BLACK)
+                {
+                  /* Change sibling from BLACK to RED.  Then the entire
+                     subtree at parent has decreased its black-height.
+                              parent                   parent
+                               bh+2                     bh+1
+                               /   \                    /   \
+                           child  sibling    -->    child  sibling
+                             bh    bh+1               bh     bh
+                   */
+                  sibling->color = RED;
+
+                  child = parent;
+                }
+              else
+                {
+                  /* Change parent from RED to BLACK, but compensate by
+                     changing sibling from BLACK to RED.
+                              parent                   parent
+                               bh+1                     bh+1
+                               /   \                    /   \
+                           child  sibling    -->    child  sibling
+                             bh    bh+1               bh     bh
+                   */
+                  parent->color = BLACK;
+                  sibling->color = RED;
+                  return;
+                }
+            }
+        }
+      else if (parent->right == child)
+        {
+          NODE_T sibling = parent->left;
+          /* sibling's black-height is >= 1.  In particular,
+             sibling != NULL.
+
+                      parent
+                       /   \
+                  sibling  child
+                    bh+1     bh
+           */
+
+          if (sibling->color == RED)
+            {
+              /* sibling is RED, hence parent is BLACK and sibling's children
+                 are non-NULL and BLACK.
+
+                      parent                 sibling
+                       bh+2                    bh+2
+                       /   \                  /   \
+                  sibling  child    -->     SR    parent
+                    bh+1     ch            bh+1    bh+1
+                    / \                            / \
+                  SL   SR                        SL  child
+                 bh+1 bh+1                      bh+1   bh
+               */
+              *parentp = rotate_right (sibling, parent);
+              parent->color = RED;
+              sibling->color = BLACK;
+
+              /* Concentrate on the subtree of parent.  The new sibling is
+                 one of the old sibling's children, and known to be BLACK.  */
+              parentp = &sibling->right;
+              sibling = parent->left;
+            }
+          /* Now we know that sibling is BLACK.
+
+                      parent
+                       /   \
+                  sibling  child
+                    bh+1     bh
+           */
+          if (sibling->left != NULL && sibling->left->color == RED)
+            {
+              /*
+                       parent                 sibling
+                      bh+1|bh+2              bh+1|bh+2
+                        /   \                  /   \
+                   sibling  child    -->     SL   parent
+                     bh+1     bh            bh+1   bh+1
+                     / \                           / \
+                   SL   SR                       SR  child
+                   bh   bh                       bh    bh
+               */
+              *parentp = rotate_right (sibling, parent);
+              sibling->color = parent->color;
+              parent->color = BLACK;
+              sibling->left->color = BLACK;
+              return;
+            }
+          else if (sibling->right != NULL && sibling->right->color == RED)
+            {
+              /*
+                      parent                       parent
+                     bh+1|bh+2                    bh+1|bh+2
+                       /   \                        /   \
+                   sibling  child    -->          SR    child
+                    bh+1      bh                 bh+1     bh
+                     / \                         /  \
+                   SL   SR                  sibling  SRR
+                   bh   bh                    bh      bh
+                       /  \                  /   \
+                     SRL  SRR               SL   SRL
+                     bh    bh               bh    bh
+
+                 where SL, SRL, SRR are all black.
+               */
+              parent->left = rotate_left (sibling, sibling->right);
+              /* Change sibling from BLACK to RED and SL from RED to BLACK.  */
+              sibling->color = RED;
+              sibling = parent->left;
+              sibling->color = BLACK;
+
+              /* Now do as in the previous case.  */
+              *parentp = rotate_right (sibling, parent);
+              sibling->color = parent->color;
+              parent->color = BLACK;
+              sibling->left->color = BLACK;
+              return;
+            }
+          else
+            {
+              if (parent->color == BLACK)
+                {
+                  /* Change sibling from BLACK to RED.  Then the entire
+                     subtree at parent has decreased its black-height.
+                              parent                   parent
+                               bh+2                     bh+1
+                               /   \                    /   \
+                           sibling  child    -->    sibling  child
+                            bh+1      bh              bh       bh
+                   */
+                  sibling->color = RED;
+
+                  child = parent;
+                }
+              else
+                {
+                  /* Change parent from RED to BLACK, but compensate by
+                     changing sibling from BLACK to RED.
+                              parent                   parent
+                               bh+1                     bh+1
+                               /   \                    /   \
+                           sibling  child    -->    sibling  child
+                            bh+1      bh              bh       bh
+                   */
+                  parent->color = BLACK;
+                  sibling->color = RED;
+                  return;
+                }
+            }
+        }
+      else
+        abort ();
+
+      /* Start again with a new (child, parent) pair.  */
+      parent = child->parent;
+
+#if 0 /* Already handled.  */
+      if (child != NULL && child->color == RED)
+        {
+          child->color = BLACK;
+          return;
+        }
+#endif
+
+      if (parent == NULL)
+        return;
+    }
+}
+
+static NODE_T
+gl_tree_nx_add_first (CONTAINER_T container, NODE_PAYLOAD_PARAMS)
+{
+  /* Create new node.  */
+  NODE_T new_node =
+    (struct NODE_IMPL *) malloc (sizeof (struct NODE_IMPL));
+
+  if (new_node == NULL)
+    return NULL;
+
+  new_node->left = NULL;
+  new_node->right = NULL;
+  NODE_PAYLOAD_ASSIGN(new_node)
+
+  /* Add it to the tree.  */
+  if (container->root == NULL)
+    {
+      new_node->color = BLACK;
+      container->root = new_node;
+      new_node->parent = NULL;
+    }
+  else
+    {
+      NODE_T node;
+
+      for (node = container->root; node->left != NULL; )
+        node = node->left;
+
+      node->left = new_node;
+      new_node->parent = node;
+
+      /* Color and rebalance.  */
+      rebalance_after_add (container, new_node, node);
+    }
+
+  container->count++;
+  return new_node;
+}
+
+static NODE_T
+gl_tree_nx_add_before (CONTAINER_T container, NODE_T node, NODE_PAYLOAD_PARAMS)
+{
+  /* Create new node.  */
+  NODE_T new_node =
+    (struct NODE_IMPL *) malloc (sizeof (struct NODE_IMPL));
+
+  if (new_node == NULL)
+    return NULL;
+
+  new_node->left = NULL;
+  new_node->right = NULL;
+  NODE_PAYLOAD_ASSIGN(new_node)
+
+  /* Add it to the tree.  */
+  if (node->left == NULL)
+    node->left = new_node;
+  else
+    {
+      for (node = node->left; node->right != NULL; )
+        node = node->right;
+      node->right = new_node;
+    }
+  new_node->parent = node;
+
+  /* Color and rebalance.  */
+  rebalance_after_add (container, new_node, node);
+
+  container->count++;
+  return new_node;
+}
+
+static NODE_T
+gl_tree_nx_add_after (CONTAINER_T container, NODE_T node, NODE_PAYLOAD_PARAMS)
+{
+  /* Create new node.  */
+  NODE_T new_node =
+    (struct NODE_IMPL *) malloc (sizeof (struct NODE_IMPL));
+
+  if (new_node == NULL)
+    return NULL;
+
+  new_node->left = NULL;
+  new_node->right = NULL;
+  NODE_PAYLOAD_ASSIGN(new_node)
+
+  /* Add it to the tree.  */
+  if (node->right == NULL)
+    node->right = new_node;
+  else
+    {
+      for (node = node->right; node->left != NULL; )
+        node = node->left;
+      node->left = new_node;
+    }
+  new_node->parent = node;
+
+  /* Color and rebalance.  */
+  rebalance_after_add (container, new_node, node);
+
+  container->count++;
+  return new_node;
+}
+
+static bool
+gl_tree_remove_node (CONTAINER_T container, NODE_T node)
+{
+  NODE_T parent = node->parent;
+
+  if (node->left == NULL)
+    {
+      /* Replace node with node->right.  */
+      NODE_T child = node->right;
+
+      if (child != NULL)
+        {
+          child->parent = parent;
+          /* Since node->left == NULL, child must be RED and of height 1,
+             hence node must have been BLACK.  Recolor the child.  */
+          child->color = BLACK;
+        }
+      if (parent == NULL)
+        container->root = child;
+      else
+        {
+          if (parent->left == node)
+            parent->left = child;
+          else /* parent->right == node */
+            parent->right = child;
+
+          if (child == NULL && node->color == BLACK)
+            rebalance_after_remove (container, child, parent);
+        }
+    }
+  else if (node->right == NULL)
+    {
+      /* It is not absolutely necessary to treat this case.  But the more
+         general case below is more complicated, hence slower.  */
+      /* Replace node with node->left.  */
+      NODE_T child = node->left;
+
+      child->parent = parent;
+      /* Since node->right == NULL, child must be RED and of height 1,
+         hence node must have been BLACK.  Recolor the child.  */
+      child->color = BLACK;
+      if (parent == NULL)
+        container->root = child;
+      else
+        {
+          if (parent->left == node)
+            parent->left = child;
+          else /* parent->right == node */
+            parent->right = child;
+        }
+    }
+  else
+    {
+      /* Replace node with the rightmost element of the node->left subtree.  */
+      NODE_T subst;
+      NODE_T subst_parent;
+      NODE_T child;
+      color_t removed_color;
+
+      for (subst = node->left; subst->right != NULL; )
+        subst = subst->right;
+
+      subst_parent = subst->parent;
+
+      child = subst->left;
+
+      removed_color = subst->color;
+
+      /* The case subst_parent == node is special:  If we do nothing special,
+         we get confusion about node->left, subst->left and child->parent.
+           subst_parent == node
+           <==> The 'for' loop above terminated immediately.
+           <==> subst == subst_parent->left
+                [otherwise subst == subst_parent->right]
+         In this case, we would need to first set
+           child->parent = node; node->left = child;
+         and later - when we copy subst into node's position - again
+           child->parent = subst; subst->left = child;
+         Altogether a no-op.  */
+      if (subst_parent != node)
+        {
+          if (child != NULL)
+            child->parent = subst_parent;
+          subst_parent->right = child;
+        }
+
+      /* Copy subst into node's position.
+         (This is safer than to copy subst's value into node, keep node in
+         place, and free subst.)  */
+      if (subst_parent != node)
+        {
+          subst->left = node->left;
+          subst->left->parent = subst;
+        }
+      subst->right = node->right;
+      subst->right->parent = subst;
+      subst->color = node->color;
+      subst->parent = parent;
+      if (parent == NULL)
+        container->root = subst;
+      else if (parent->left == node)
+        parent->left = subst;
+      else /* parent->right == node */
+        parent->right = subst;
+
+      if (removed_color == BLACK)
+        {
+          if (child != NULL && child->color == RED)
+            /* Recolor the child.  */
+            child->color = BLACK;
+          else
+            /* Rebalancing starts at child's parent, that is subst_parent -
+               except when subst_parent == node.  In this case, we need to use
+               its replacement, subst.  */
+            rebalance_after_remove (container, child,
+                                    subst_parent != node ? subst_parent : subst);
+        }
+    }
+
+  container->count--;
+  NODE_PAYLOAD_DISPOSE
+  free (node);
+  return true;
+}
+
+/* For debugging.  */
+static unsigned int
+check_invariants (NODE_T node, NODE_T parent, size_t *counterp)
+{
+  unsigned int left_blackheight =
+    (node->left != NULL ? check_invariants (node->left, node, counterp) : 0);
+  unsigned int right_blackheight =
+    (node->right != NULL ? check_invariants (node->right, node, counterp) : 0);
+
+  if (!(node->parent == parent))
+    abort ();
+  if (!(node->color == BLACK || node->color == RED))
+    abort ();
+  if (parent == NULL && !(node->color == BLACK))
+    abort ();
+  if (!(left_blackheight == right_blackheight))
+    abort ();
+
+  (*counterp)++;
+
+  return left_blackheight + (node->color == BLACK ? 1 : 0);
+}
--- a/lib/gl_rbtree_oset.c	Tue Dec 11 20:56:25 2018 +0100
+++ b/lib/gl_rbtree_oset.c	Tue Dec 11 20:56:27 2018 +0100
@@ -22,773 +22,30 @@
 
 #include <stdlib.h>
 
-/* 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_oset_t Data Type -------------------------- */
 
-/* Color of a node.  */
-typedef enum color { BLACK, RED } color_t;
-
-/* Tree node implementation, valid for this file only.  */
-struct gl_oset_node_impl
-{
-  struct gl_oset_node_impl *left;   /* left branch, or NULL */
-  struct gl_oset_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_oset_node_t can be returned
-     without memory allocation, on which the functions gl_oset_remove_node,
-     gl_oset_add_before, gl_oset_add_after can be implemented.  */
-  struct gl_oset_node_impl *parent;
-  color_t color;                    /* node's color */
+/* Parameterization of gl_rbtree_ordered.h.  */
+#define CONTAINER_T gl_oset_t
+#define CONTAINER_IMPL gl_oset_impl
+#define CONTAINER_IMPL_BASE gl_oset_impl_base
+#define NODE_IMPL gl_oset_node_impl
+#define NODE_T gl_oset_node_t
+#define NODE_PAYLOAD_FIELDS \
   const void *value;
-};
-typedef struct gl_oset_node_impl * gl_oset_node_t;
-
-/* Concrete gl_oset_impl type, valid for this file only.  */
-struct gl_oset_impl
-{
-  struct gl_oset_impl_base base;
-  struct gl_oset_node_impl *root;   /* root node or NULL */
-  size_t count;                     /* number of nodes */
-};
-
-/* 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_oset_node_impl) * (2^59 - 1) > 2^64
-   this would exceed the address space of the machine.  */
-#define MAXHEIGHT 116
-
-/* Rotate left a subtree.
-
-                         B                         D
-                       /   \                     /   \
-                     A       D       -->       B       E
-                            / \               / \
-                           C   E             A   C
-
-   Change the tree structure, update the branch sizes.
-   The caller must update the colors and register D as child of its parent.  */
-static gl_oset_node_t
-rotate_left (gl_oset_node_t b_node, gl_oset_node_t d_node)
-{
-  gl_oset_node_t c_node = d_node->left;
-
-  b_node->right = c_node;
-  d_node->left = b_node;
-
-  d_node->parent = b_node->parent;
-  b_node->parent = d_node;
-  if (c_node != NULL)
-    c_node->parent = b_node;
-
-  return d_node;
-}
-
-/* Rotate right a subtree.
-
-                           D                     B
-                         /   \                 /   \
-                       B       E     -->     A       D
-                      / \                           / \
-                     A   C                         C   E
-
-   Change the tree structure, update the branch sizes.
-   The caller must update the colors and register B as child of its parent.  */
-static gl_oset_node_t
-rotate_right (gl_oset_node_t b_node, gl_oset_node_t d_node)
-{
-  gl_oset_node_t c_node = b_node->right;
-
-  d_node->left = c_node;
-  b_node->right = d_node;
-
-  b_node->parent = d_node->parent;
-  d_node->parent = b_node;
-  if (c_node != NULL)
-    c_node->parent = d_node;
-
-  return b_node;
-}
-
-/* Ensure the tree is balanced, after an insertion operation.
-   Also assigns node->color.
-   parent is the given node's parent, known to be non-NULL.  */
-static void
-rebalance_after_add (gl_oset_t set, gl_oset_node_t node, gl_oset_node_t parent)
-{
-  for (;;)
-    {
-      /* At this point, parent = node->parent != NULL.
-         Think of node->color being RED (although node->color is not yet
-         assigned.)  */
-      gl_oset_node_t grandparent;
-      gl_oset_node_t uncle;
-
-      if (parent->color == BLACK)
-        {
-          /* A RED color for node is acceptable.  */
-          node->color = RED;
-          return;
-        }
-
-      grandparent = parent->parent;
-      /* Since parent is RED, we know that
-         grandparent is != NULL and colored BLACK.  */
-
-      if (grandparent->left == parent)
-        uncle = grandparent->right;
-      else if (grandparent->right == parent)
-        uncle = grandparent->left;
-      else
-        abort ();
-
-      if (uncle != NULL && uncle->color == RED)
-        {
-          /* Change grandparent from BLACK to RED, and
-             change parent and uncle from RED to BLACK.
-             This makes it acceptable for node to be RED.  */
-          node->color = RED;
-          parent->color = uncle->color = BLACK;
-          node = grandparent;
-        }
-      else
-        {
-          /* grandparent and uncle are BLACK.  parent is RED.  node wants
-             to be RED too.
-             In this case, recoloring is not sufficient.  Need to perform
-             one or two rotations.  */
-          gl_oset_node_t *grandparentp;
-
-          if (grandparent->parent == NULL)
-            grandparentp = &set->root;
-          else if (grandparent->parent->left == grandparent)
-            grandparentp = &grandparent->parent->left;
-          else if (grandparent->parent->right == grandparent)
-            grandparentp = &grandparent->parent->right;
-          else
-            abort ();
-
-          if (grandparent->left == parent)
-            {
-              if (parent->right == node)
-                {
-                  /* Rotation between node and parent.  */
-                  grandparent->left = rotate_left (parent, node);
-                  node = parent;
-                  parent = grandparent->left;
-                }
-              /* grandparent and uncle are BLACK.  parent and node want to be
-                 RED.  parent = grandparent->left.  node = parent->left.
-
-                      grandparent              parent
-                         bh+1                   bh+1
-                         /   \                 /   \
-                     parent  uncle    -->   node  grandparent
-                      bh      bh             bh      bh
-                      / \                           / \
-                   node  C                         C  uncle
-                    bh   bh                       bh    bh
-               */
-              *grandparentp = rotate_right (parent, grandparent);
-              parent->color = BLACK;
-              node->color = grandparent->color = RED;
-            }
-          else /* grandparent->right == parent */
-            {
-              if (parent->left == node)
-                {
-                  /* Rotation between node and parent.  */
-                  grandparent->right = rotate_right (node, parent);
-                  node = parent;
-                  parent = grandparent->right;
-                }
-              /* grandparent and uncle are BLACK.  parent and node want to be
-                 RED.  parent = grandparent->right.  node = parent->right.
-
-                    grandparent                    parent
-                       bh+1                         bh+1
-                       /   \                       /   \
-                   uncle  parent     -->   grandparent  node
-                     bh     bh                  bh       bh
-                            / \                 / \
-                           C  node          uncle  C
-                          bh   bh            bh    bh
-               */
-              *grandparentp = rotate_left (grandparent, parent);
-              parent->color = BLACK;
-              node->color = grandparent->color = RED;
-            }
-          return;
-        }
-
-      /* Start again with a new (node, parent) pair.  */
-      parent = node->parent;
-
-      if (parent == NULL)
-        {
-          /* Change node's color from RED to BLACK.  This increases the
-             tree's black-height.  */
-          node->color = BLACK;
-          return;
-        }
-    }
-}
-
-/* Ensure the tree is balanced, after a deletion operation.
-   CHILD was a grandchild of PARENT and is now its child.  Between them,
-   a black node was removed.  CHILD is also black, or NULL.
-   (CHILD can also be NULL.  But PARENT is non-NULL.)  */
-static void
-rebalance_after_remove (gl_oset_t set, gl_oset_node_t child, gl_oset_node_t parent)
-{
-  for (;;)
-    {
-      /* At this point, we reduced the black-height of the CHILD subtree by 1.
-         To make up, either look for a possibility to turn a RED to a BLACK
-         node, or try to reduce the black-height tree of CHILD's sibling
-         subtree as well.  */
-      gl_oset_node_t *parentp;
-
-      if (parent->parent == NULL)
-        parentp = &set->root;
-      else if (parent->parent->left == parent)
-        parentp = &parent->parent->left;
-      else if (parent->parent->right == parent)
-        parentp = &parent->parent->right;
-      else
-        abort ();
-
-      if (parent->left == child)
-        {
-          gl_oset_node_t sibling = parent->right;
-          /* sibling's black-height is >= 1.  In particular,
-             sibling != NULL.
-
-                      parent
-                       /   \
-                   child  sibling
-                     bh    bh+1
-           */
-
-          if (sibling->color == RED)
-            {
-              /* sibling is RED, hence parent is BLACK and sibling's children
-                 are non-NULL and BLACK.
-
-                      parent                       sibling
-                       bh+2                         bh+2
-                       /   \                        /   \
-                   child  sibling     -->       parent    SR
-                     bh    bh+1                  bh+1    bh+1
-                            / \                  / \
-                          SL   SR            child  SL
-                         bh+1 bh+1             bh  bh+1
-               */
-              *parentp = rotate_left (parent, sibling);
-              parent->color = RED;
-              sibling->color = BLACK;
-
-              /* Concentrate on the subtree of parent.  The new sibling is
-                 one of the old sibling's children, and known to be BLACK.  */
-              parentp = &sibling->left;
-              sibling = parent->right;
-            }
-          /* Now we know that sibling is BLACK.
-
-                      parent
-                       /   \
-                   child  sibling
-                     bh    bh+1
-           */
-          if (sibling->right != NULL && sibling->right->color == RED)
-            {
-              /*
-                      parent                     sibling
-                     bh+1|bh+2                  bh+1|bh+2
-                       /   \                      /   \
-                   child  sibling    -->      parent    SR
-                     bh    bh+1                bh+1    bh+1
-                            / \                / \
-                          SL   SR           child  SL
-                          bh   bh             bh   bh
-               */
-              *parentp = rotate_left (parent, sibling);
-              sibling->color = parent->color;
-              parent->color = BLACK;
-              sibling->right->color = BLACK;
-              return;
-            }
-          else if (sibling->left != NULL && sibling->left->color == RED)
-            {
-              /*
-                      parent                   parent
-                     bh+1|bh+2                bh+1|bh+2
-                       /   \                    /   \
-                   child  sibling    -->    child    SL
-                     bh    bh+1               bh    bh+1
-                            / \                     /  \
-                          SL   SR                 SLL  sibling
-                          bh   bh                 bh     bh
-                         /  \                           /   \
-                       SLL  SLR                       SLR    SR
-                       bh    bh                       bh     bh
-
-                 where SLL, SLR, SR are all black.
-               */
-              parent->right = rotate_right (sibling->left, sibling);
-              /* Change sibling from BLACK to RED and SL from RED to BLACK.  */
-              sibling->color = RED;
-              sibling = parent->right;
-              sibling->color = BLACK;
-
-              /* Now do as in the previous case.  */
-              *parentp = rotate_left (parent, sibling);
-              sibling->color = parent->color;
-              parent->color = BLACK;
-              sibling->right->color = BLACK;
-              return;
-            }
-          else
-            {
-              if (parent->color == BLACK)
-                {
-                  /* Change sibling from BLACK to RED.  Then the entire
-                     subtree at parent has decreased its black-height.
-                              parent                   parent
-                               bh+2                     bh+1
-                               /   \                    /   \
-                           child  sibling    -->    child  sibling
-                             bh    bh+1               bh     bh
-                   */
-                  sibling->color = RED;
-
-                  child = parent;
-                }
-              else
-                {
-                  /* Change parent from RED to BLACK, but compensate by
-                     changing sibling from BLACK to RED.
-                              parent                   parent
-                               bh+1                     bh+1
-                               /   \                    /   \
-                           child  sibling    -->    child  sibling
-                             bh    bh+1               bh     bh
-                   */
-                  parent->color = BLACK;
-                  sibling->color = RED;
-                  return;
-                }
-            }
-        }
-      else if (parent->right == child)
-        {
-          gl_oset_node_t sibling = parent->left;
-          /* sibling's black-height is >= 1.  In particular,
-             sibling != NULL.
+#define NODE_PAYLOAD_PARAMS \
+  const void *elt
+#define NODE_PAYLOAD_ASSIGN(node) \
+  node->value = elt;
+#define NODE_PAYLOAD_DISPOSE \
+  if (container->base.dispose_fn != NULL) \
+    container->base.dispose_fn (node->value);
 
-                      parent
-                       /   \
-                  sibling  child
-                    bh+1     bh
-           */
-
-          if (sibling->color == RED)
-            {
-              /* sibling is RED, hence parent is BLACK and sibling's children
-                 are non-NULL and BLACK.
-
-                      parent                 sibling
-                       bh+2                    bh+2
-                       /   \                  /   \
-                  sibling  child    -->     SR    parent
-                    bh+1     ch            bh+1    bh+1
-                    / \                            / \
-                  SL   SR                        SL  child
-                 bh+1 bh+1                      bh+1   bh
-               */
-              *parentp = rotate_right (sibling, parent);
-              parent->color = RED;
-              sibling->color = BLACK;
-
-              /* Concentrate on the subtree of parent.  The new sibling is
-                 one of the old sibling's children, and known to be BLACK.  */
-              parentp = &sibling->right;
-              sibling = parent->left;
-            }
-          /* Now we know that sibling is BLACK.
-
-                      parent
-                       /   \
-                  sibling  child
-                    bh+1     bh
-           */
-          if (sibling->left != NULL && sibling->left->color == RED)
-            {
-              /*
-                       parent                 sibling
-                      bh+1|bh+2              bh+1|bh+2
-                        /   \                  /   \
-                   sibling  child    -->     SL   parent
-                     bh+1     bh            bh+1   bh+1
-                     / \                           / \
-                   SL   SR                       SR  child
-                   bh   bh                       bh    bh
-               */
-              *parentp = rotate_right (sibling, parent);
-              sibling->color = parent->color;
-              parent->color = BLACK;
-              sibling->left->color = BLACK;
-              return;
-            }
-          else if (sibling->right != NULL && sibling->right->color == RED)
-            {
-              /*
-                      parent                       parent
-                     bh+1|bh+2                    bh+1|bh+2
-                       /   \                        /   \
-                   sibling  child    -->          SR    child
-                    bh+1      bh                 bh+1     bh
-                     / \                         /  \
-                   SL   SR                  sibling  SRR
-                   bh   bh                    bh      bh
-                       /  \                  /   \
-                     SRL  SRR               SL   SRL
-                     bh    bh               bh    bh
-
-                 where SL, SRL, SRR are all black.
-               */
-              parent->left = rotate_left (sibling, sibling->right);
-              /* Change sibling from BLACK to RED and SL from RED to BLACK.  */
-              sibling->color = RED;
-              sibling = parent->left;
-              sibling->color = BLACK;
-
-              /* Now do as in the previous case.  */
-              *parentp = rotate_right (sibling, parent);
-              sibling->color = parent->color;
-              parent->color = BLACK;
-              sibling->left->color = BLACK;
-              return;
-            }
-          else
-            {
-              if (parent->color == BLACK)
-                {
-                  /* Change sibling from BLACK to RED.  Then the entire
-                     subtree at parent has decreased its black-height.
-                              parent                   parent
-                               bh+2                     bh+1
-                               /   \                    /   \
-                           sibling  child    -->    sibling  child
-                            bh+1      bh              bh       bh
-                   */
-                  sibling->color = RED;
-
-                  child = parent;
-                }
-              else
-                {
-                  /* Change parent from RED to BLACK, but compensate by
-                     changing sibling from BLACK to RED.
-                              parent                   parent
-                               bh+1                     bh+1
-                               /   \                    /   \
-                           sibling  child    -->    sibling  child
-                            bh+1      bh              bh       bh
-                   */
-                  parent->color = BLACK;
-                  sibling->color = RED;
-                  return;
-                }
-            }
-        }
-      else
-        abort ();
-
-      /* Start again with a new (child, parent) pair.  */
-      parent = child->parent;
-
-#if 0 /* Already handled.  */
-      if (child != NULL && child->color == RED)
-        {
-          child->color = BLACK;
-          return;
-        }
-#endif
-
-      if (parent == NULL)
-        return;
-    }
-}
-
-static gl_oset_node_t
-gl_tree_nx_add_first (gl_oset_t set, const void *elt)
-{
-  /* Create new node.  */
-  gl_oset_node_t new_node =
-    (struct gl_oset_node_impl *) malloc (sizeof (struct gl_oset_node_impl));
-
-  if (new_node == NULL)
-    return NULL;
-
-  new_node->left = NULL;
-  new_node->right = NULL;
-  new_node->value = elt;
-
-  /* Add it to the tree.  */
-  if (set->root == NULL)
-    {
-      new_node->color = BLACK;
-      set->root = new_node;
-      new_node->parent = NULL;
-    }
-  else
-    {
-      gl_oset_node_t node;
-
-      for (node = set->root; node->left != NULL; )
-        node = node->left;
-
-      node->left = new_node;
-      new_node->parent = node;
-
-      /* Color and rebalance.  */
-      rebalance_after_add (set, new_node, node);
-    }
-
-  set->count++;
-  return new_node;
-}
-
-static gl_oset_node_t
-gl_tree_nx_add_before (gl_oset_t set, gl_oset_node_t node, const void *elt)
-{
-  /* Create new node.  */
-  gl_oset_node_t new_node =
-    (struct gl_oset_node_impl *) malloc (sizeof (struct gl_oset_node_impl));
-
-  if (new_node == NULL)
-    return NULL;
-
-  new_node->left = NULL;
-  new_node->right = NULL;
-  new_node->value = elt;
-
-  /* Add it to the tree.  */
-  if (node->left == NULL)
-    node->left = new_node;
-  else
-    {
-      for (node = node->left; node->right != NULL; )
-        node = node->right;
-      node->right = new_node;
-    }
-  new_node->parent = node;
-
-  /* Color and rebalance.  */
-  rebalance_after_add (set, new_node, node);
-
-  set->count++;
-  return new_node;
-}
-
-static gl_oset_node_t
-gl_tree_nx_add_after (gl_oset_t set, gl_oset_node_t node, const void *elt)
-{
-  /* Create new node.  */
-  gl_oset_node_t new_node =
-    (struct gl_oset_node_impl *) malloc (sizeof (struct gl_oset_node_impl));
-
-  if (new_node == NULL)
-    return NULL;
-
-  new_node->left = NULL;
-  new_node->right = NULL;
-  new_node->value = elt;
-
-  /* Add it to the tree.  */
-  if (node->right == NULL)
-    node->right = new_node;
-  else
-    {
-      for (node = node->right; node->left != NULL; )
-        node = node->left;
-      node->left = new_node;
-    }
-  new_node->parent = node;
-
-  /* Color and rebalance.  */
-  rebalance_after_add (set, new_node, node);
-
-  set->count++;
-  return new_node;
-}
-
-static bool
-gl_tree_remove_node (gl_oset_t set, gl_oset_node_t node)
-{
-  gl_oset_node_t parent = node->parent;
-
-  if (node->left == NULL)
-    {
-      /* Replace node with node->right.  */
-      gl_oset_node_t child = node->right;
-
-      if (child != NULL)
-        {
-          child->parent = parent;
-          /* Since node->left == NULL, child must be RED and of height 1,
-             hence node must have been BLACK.  Recolor the child.  */
-          child->color = BLACK;
-        }
-      if (parent == NULL)
-        set->root = child;
-      else
-        {
-          if (parent->left == node)
-            parent->left = child;
-          else /* parent->right == node */
-            parent->right = child;
-
-          if (child == NULL && node->color == BLACK)
-            rebalance_after_remove (set, child, parent);
-        }
-    }
-  else if (node->right == NULL)
-    {
-      /* It is not absolutely necessary to treat this case.  But the more
-         general case below is more complicated, hence slower.  */
-      /* Replace node with node->left.  */
-      gl_oset_node_t child = node->left;
-
-      child->parent = parent;
-      /* Since node->right == NULL, child must be RED and of height 1,
-         hence node must have been BLACK.  Recolor the child.  */
-      child->color = BLACK;
-      if (parent == NULL)
-        set->root = child;
-      else
-        {
-          if (parent->left == node)
-            parent->left = child;
-          else /* parent->right == node */
-            parent->right = child;
-        }
-    }
-  else
-    {
-      /* Replace node with the rightmost element of the node->left subtree.  */
-      gl_oset_node_t subst;
-      gl_oset_node_t subst_parent;
-      gl_oset_node_t child;
-      color_t removed_color;
-
-      for (subst = node->left; subst->right != NULL; )
-        subst = subst->right;
-
-      subst_parent = subst->parent;
-
-      child = subst->left;
-
-      removed_color = subst->color;
-
-      /* The case subst_parent == node is special:  If we do nothing special,
-         we get confusion about node->left, subst->left and child->parent.
-           subst_parent == node
-           <==> The 'for' loop above terminated immediately.
-           <==> subst == subst_parent->left
-                [otherwise subst == subst_parent->right]
-         In this case, we would need to first set
-           child->parent = node; node->left = child;
-         and later - when we copy subst into node's position - again
-           child->parent = subst; subst->left = child;
-         Altogether a no-op.  */
-      if (subst_parent != node)
-        {
-          if (child != NULL)
-            child->parent = subst_parent;
-          subst_parent->right = child;
-        }
-
-      /* Copy subst into node's position.
-         (This is safer than to copy subst's value into node, keep node in
-         place, and free subst.)  */
-      if (subst_parent != node)
-        {
-          subst->left = node->left;
-          subst->left->parent = subst;
-        }
-      subst->right = node->right;
-      subst->right->parent = subst;
-      subst->color = node->color;
-      subst->parent = parent;
-      if (parent == NULL)
-        set->root = subst;
-      else if (parent->left == node)
-        parent->left = subst;
-      else /* parent->right == node */
-        parent->right = subst;
-
-      if (removed_color == BLACK)
-        {
-          if (child != NULL && child->color == RED)
-            /* Recolor the child.  */
-            child->color = BLACK;
-          else
-            /* Rebalancing starts at child's parent, that is subst_parent -
-               except when subst_parent == node.  In this case, we need to use
-               its replacement, subst.  */
-            rebalance_after_remove (set, child,
-                                    subst_parent != node ? subst_parent : subst);
-        }
-    }
-
-  set->count--;
-  if (set->base.dispose_fn != NULL)
-    set->base.dispose_fn (node->value);
-  free (node);
-  return true;
-}
+#include "gl_rbtree_ordered.h"
 
 /* Generic binary tree code.  */
 #include "gl_anytree_oset.h"
 
 /* For debugging.  */
-static unsigned int
-check_invariants (gl_oset_node_t node, gl_oset_node_t parent, size_t *counterp)
-{
-  unsigned int left_blackheight =
-    (node->left != NULL ? check_invariants (node->left, node, counterp) : 0);
-  unsigned int right_blackheight =
-    (node->right != NULL ? check_invariants (node->right, node, counterp) : 0);
-
-  if (!(node->parent == parent))
-    abort ();
-  if (!(node->color == BLACK || node->color == RED))
-    abort ();
-  if (parent == NULL && !(node->color == BLACK))
-    abort ();
-  if (!(left_blackheight == right_blackheight))
-    abort ();
-
-  (*counterp)++;
-
-  return left_blackheight + (node->color == BLACK ? 1 : 0);
-}
 void
 gl_rbtree_oset_check_invariants (gl_oset_t set)
 {
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modules/rbtree-omap	Tue Dec 11 20:56:27 2018 +0100
@@ -0,0 +1,25 @@
+Description:
+Ordered map data type implemented by a binary tree.
+
+Files:
+lib/gl_rbtree_omap.h
+lib/gl_rbtree_omap.c
+lib/gl_rbtree_ordered.h
+lib/gl_anytree_omap.h
+
+Depends-on:
+omap
+
+configure.ac:
+
+Makefile.am:
+lib_SOURCES += gl_rbtree_omap.h gl_rbtree_omap.c gl_rbtree_ordered.h gl_anytree_omap.h
+
+Include:
+"gl_rbtree_omap.h"
+
+License:
+GPL
+
+Maintainer:
+all
--- a/modules/rbtree-oset	Tue Dec 11 20:56:25 2018 +0100
+++ b/modules/rbtree-oset	Tue Dec 11 20:56:27 2018 +0100
@@ -4,6 +4,7 @@
 Files:
 lib/gl_rbtree_oset.h
 lib/gl_rbtree_oset.c
+lib/gl_rbtree_ordered.h
 lib/gl_anytree_oset.h
 
 Depends-on:
@@ -12,7 +13,7 @@
 configure.ac:
 
 Makefile.am:
-lib_SOURCES += gl_rbtree_oset.h gl_rbtree_oset.c gl_anytree_oset.h
+lib_SOURCES += gl_rbtree_oset.h gl_rbtree_oset.c gl_rbtree_ordered.h gl_anytree_oset.h
 
 Include:
 "gl_rbtree_oset.h"