core: Add rbtree based hash table

Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 145 (NFSv3 related additions to 2.1 task list)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=145

2 files changed, 1051 insertions, 0 deletions

diff --git a/contrib/rbtree/rb.c b/contrib/rbtree/rb.c
new file mode 100644
index 000000000..d1339b97d
--- /dev/null
+++ b/contrib/rbtree/rb.c
@@ -0,0 +1,929 @@
+/* Produced by texiweb from libavl.w. */
+
+/* libavl - library for manipulation of binary trees.
+   Copyright (C) 1998-2002, 2004 Free Software Foundation, Inc.
+
+   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 2 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, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+   02111-1307, USA.
+
+   The author may be contacted at <blp@gnu.org> on the Internet, or
+   write to Ben Pfaff, Stanford University, Computer Science Dept., 353
+   Serra Mall, Stanford CA 94305, USA.
+*/
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "rb.h"
+
+/* Creates and returns a new table
+   with comparison function |compare| using parameter |param|
+   and memory allocator |allocator|.
+   Returns |NULL| if memory allocation failed. */
+struct rb_table *
+rb_create (rb_comparison_func *compare, void *param,
+            struct libavl_allocator *allocator)
+{
+  struct rb_table *tree;
+
+  assert (compare != NULL);
+
+  if (allocator == NULL)
+    allocator = &rb_allocator_default;
+
+  tree = allocator->libavl_malloc (allocator, sizeof *tree);
+  if (tree == NULL)
+    return NULL;
+
+  tree->rb_root = NULL;
+  tree->rb_compare = compare;
+  tree->rb_param = param;
+  tree->rb_alloc = allocator;
+  tree->rb_count = 0;
+  tree->rb_generation = 0;
+
+  return tree;
+}
+
+/* Search |tree| for an item matching |item|, and return it if found.
+   Otherwise return |NULL|. */
+void *
+rb_find (const struct rb_table *tree, const void *item)
+{
+  const struct rb_node *p;
+
+  assert (tree != NULL && item != NULL);
+  for (p = tree->rb_root; p != NULL; )
+    {
+      int cmp = tree->rb_compare (item, p->rb_data, tree->rb_param);
+
+      if (cmp < 0)
+        p = p->rb_link[0];
+      else if (cmp > 0)
+        p = p->rb_link[1];
+      else /* |cmp == 0| */
+        return p->rb_data;
+    }
+
+  return NULL;
+}
+
+/* Inserts |item| into |tree| and returns a pointer to |item|'s address.
+   If a duplicate item is found in the tree,
+   returns a pointer to the duplicate without inserting |item|.
+   Returns |NULL| in case of memory allocation failure. */
+void **
+rb_probe (struct rb_table *tree, void *item)
+{
+  struct rb_node *pa[RB_MAX_HEIGHT]; /* Nodes on stack. */
+  unsigned char da[RB_MAX_HEIGHT];   /* Directions moved from stack nodes. */
+  int k;                             /* Stack height. */
+
+  struct rb_node *p; /* Traverses tree looking for insertion point. */
+  struct rb_node *n; /* Newly inserted node. */
+
+  assert (tree != NULL && item != NULL);
+
+  pa[0] = (struct rb_node *) &tree->rb_root;
+  da[0] = 0;
+  k = 1;
+  for (p = tree->rb_root; p != NULL; p = p->rb_link[da[k - 1]])
+    {
+      int cmp = tree->rb_compare (item, p->rb_data, tree->rb_param);
+      if (cmp == 0)
+        return &p->rb_data;
+
+      pa[k] = p;
+      da[k++] = cmp > 0;
+    }
+
+  n = pa[k - 1]->rb_link[da[k - 1]] =
+    tree->rb_alloc->libavl_malloc (tree->rb_alloc, sizeof *n);
+  if (n == NULL)
+    return NULL;
+
+  n->rb_data = item;
+  n->rb_link[0] = n->rb_link[1] = NULL;
+  n->rb_color = RB_RED;
+  tree->rb_count++;
+  tree->rb_generation++;
+
+  while (k >= 3 && pa[k - 1]->rb_color == RB_RED)
+    {
+      if (da[k - 2] == 0)
+        {
+          struct rb_node *y = pa[k - 2]->rb_link[1];
+          if (y != NULL && y->rb_color == RB_RED)
+            {
+              pa[k - 1]->rb_color = y->rb_color = RB_BLACK;
+              pa[k - 2]->rb_color = RB_RED;
+              k -= 2;
+            }
+          else
+            {
+              struct rb_node *x;
+
+              if (da[k - 1] == 0)
+                y = pa[k - 1];
+              else
+                {
+                  x = pa[k - 1];
+                  y = x->rb_link[1];
+                  x->rb_link[1] = y->rb_link[0];
+                  y->rb_link[0] = x;
+                  pa[k - 2]->rb_link[0] = y;
+                }
+
+              x = pa[k - 2];
+              x->rb_color = RB_RED;
+              y->rb_color = RB_BLACK;
+
+              x->rb_link[0] = y->rb_link[1];
+              y->rb_link[1] = x;
+              pa[k - 3]->rb_link[da[k - 3]] = y;
+              break;
+            }
+        }
+      else
+        {
+          struct rb_node *y = pa[k - 2]->rb_link[0];
+          if (y != NULL && y->rb_color == RB_RED)
+            {
+              pa[k - 1]->rb_color = y->rb_color = RB_BLACK;
+              pa[k - 2]->rb_color = RB_RED;
+              k -= 2;
+            }
+          else
+            {
+              struct rb_node *x;
+
+              if (da[k - 1] == 1)
+                y = pa[k - 1];
+              else
+                {
+                  x = pa[k - 1];
+                  y = x->rb_link[0];
+                  x->rb_link[0] = y->rb_link[1];
+                  y->rb_link[1] = x;
+                  pa[k - 2]->rb_link[1] = y;
+                }
+
+              x = pa[k - 2];
+              x->rb_color = RB_RED;
+              y->rb_color = RB_BLACK;
+
+              x->rb_link[1] = y->rb_link[0];
+              y->rb_link[0] = x;
+              pa[k - 3]->rb_link[da[k - 3]] = y;
+              break;
+            }
+        }
+    }
+  tree->rb_root->rb_color = RB_BLACK;
+
+
+  return &n->rb_data;
+}
+
+/* Inserts |item| into |table|.
+   Returns |NULL| if |item| was successfully inserted
+   or if a memory allocation error occurred.
+   Otherwise, returns the duplicate item. */
+void *
+rb_insert (struct rb_table *table, void *item)
+{
+  void **p = rb_probe (table, item);
+  return p == NULL || *p == item ? NULL : *p;
+}
+
+/* Inserts |item| into |table|, replacing any duplicate item.
+   Returns |NULL| if |item| was inserted without replacing a duplicate,
+   or if a memory allocation error occurred.
+   Otherwise, returns the item that was replaced. */
+void *
+rb_replace (struct rb_table *table, void *item)
+{
+  void **p = rb_probe (table, item);
+  if (p == NULL || *p == item)
+    return NULL;
+  else
+    {
+      void *r = *p;
+      *p = item;
+      return r;
+    }
+}
+
+/* Deletes from |tree| and returns an item matching |item|.
+   Returns a null pointer if no matching item found. */
+void *
+rb_delete (struct rb_table *tree, const void *item)
+{
+  struct rb_node *pa[RB_MAX_HEIGHT]; /* Nodes on stack. */
+  unsigned char da[RB_MAX_HEIGHT];   /* Directions moved from stack nodes. */
+  int k;                             /* Stack height. */
+
+  struct rb_node *p;    /* The node to delete, or a node part way to it. */
+  int cmp;              /* Result of comparison between |item| and |p|. */
+
+  assert (tree != NULL && item != NULL);
+
+  k = 0;
+  p = (struct rb_node *) &tree->rb_root;
+  for (cmp = -1; cmp != 0;
+       cmp = tree->rb_compare (item, p->rb_data, tree->rb_param))
+    {
+      int dir = cmp > 0;
+
+      pa[k] = p;
+      da[k++] = dir;
+
+      p = p->rb_link[dir];
+      if (p == NULL)
+        return NULL;
+    }
+  item = p->rb_data;
+
+  if (p->rb_link[1] == NULL)
+    pa[k - 1]->rb_link[da[k - 1]] = p->rb_link[0];
+  else
+    {
+      enum rb_color t;
+      struct rb_node *r = p->rb_link[1];
+
+      if (r->rb_link[0] == NULL)
+        {
+          r->rb_link[0] = p->rb_link[0];
+          t = r->rb_color;
+          r->rb_color = p->rb_color;
+          p->rb_color = t;
+          pa[k - 1]->rb_link[da[k - 1]] = r;
+          da[k] = 1;
+          pa[k++] = r;
+        }
+      else
+        {
+          struct rb_node *s;
+          int j = k++;
+
+          for (;;)
+            {
+              da[k] = 0;
+              pa[k++] = r;
+              s = r->rb_link[0];
+              if (s->rb_link[0] == NULL)
+                break;
+
+              r = s;
+            }
+
+          da[j] = 1;
+          pa[j] = s;
+          pa[j - 1]->rb_link[da[j - 1]] = s;
+
+          s->rb_link[0] = p->rb_link[0];
+          r->rb_link[0] = s->rb_link[1];
+          s->rb_link[1] = p->rb_link[1];
+
+          t = s->rb_color;
+          s->rb_color = p->rb_color;
+          p->rb_color = t;
+        }
+    }
+
+  if (p->rb_color == RB_BLACK)
+    {
+      for (;;)
+        {
+          struct rb_node *x = pa[k - 1]->rb_link[da[k - 1]];
+          if (x != NULL && x->rb_color == RB_RED)
+            {
+              x->rb_color = RB_BLACK;
+              break;
+            }
+          if (k < 2)
+            break;
+
+          if (da[k - 1] == 0)
+            {
+              struct rb_node *w = pa[k - 1]->rb_link[1];
+
+              if (w->rb_color == RB_RED)
+                {
+                  w->rb_color = RB_BLACK;
+                  pa[k - 1]->rb_color = RB_RED;
+
+                  pa[k - 1]->rb_link[1] = w->rb_link[0];
+                  w->rb_link[0] = pa[k - 1];
+                  pa[k - 2]->rb_link[da[k - 2]] = w;
+
+                  pa[k] = pa[k - 1];
+                  da[k] = 0;
+                  pa[k - 1] = w;
+                  k++;
+
+                  w = pa[k - 1]->rb_link[1];
+                }
+
+              if ((w->rb_link[0] == NULL
+                   || w->rb_link[0]->rb_color == RB_BLACK)
+                  && (w->rb_link[1] == NULL
+                      || w->rb_link[1]->rb_color == RB_BLACK))
+                w->rb_color = RB_RED;
+              else
+                {
+                  if (w->rb_link[1] == NULL
+                      || w->rb_link[1]->rb_color == RB_BLACK)
+                    {
+                      struct rb_node *y = w->rb_link[0];
+                      y->rb_color = RB_BLACK;
+                      w->rb_color = RB_RED;
+                      w->rb_link[0] = y->rb_link[1];
+                      y->rb_link[1] = w;
+                      w = pa[k - 1]->rb_link[1] = y;
+                    }
+
+                  w->rb_color = pa[k - 1]->rb_color;
+                  pa[k - 1]->rb_color = RB_BLACK;
+                  w->rb_link[1]->rb_color = RB_BLACK;
+
+                  pa[k - 1]->rb_link[1] = w->rb_link[0];
+                  w->rb_link[0] = pa[k - 1];
+                  pa[k - 2]->rb_link[da[k - 2]] = w;
+                  break;
+                }
+            }
+          else
+            {
+              struct rb_node *w = pa[k - 1]->rb_link[0];
+
+              if (w->rb_color == RB_RED)
+                {
+                  w->rb_color = RB_BLACK;
+                  pa[k - 1]->rb_color = RB_RED;
+
+                  pa[k - 1]->rb_link[0] = w->rb_link[1];
+                  w->rb_link[1] = pa[k - 1];
+                  pa[k - 2]->rb_link[da[k - 2]] = w;
+
+                  pa[k] = pa[k - 1];
+                  da[k] = 1;
+                  pa[k - 1] = w;
+                  k++;
+
+                  w = pa[k - 1]->rb_link[0];
+                }
+
+              if ((w->rb_link[0] == NULL
+                   || w->rb_link[0]->rb_color == RB_BLACK)
+                  && (w->rb_link[1] == NULL
+                      || w->rb_link[1]->rb_color == RB_BLACK))
+                w->rb_color = RB_RED;
+              else
+                {
+                  if (w->rb_link[0] == NULL
+                      || w->rb_link[0]->rb_color == RB_BLACK)
+                    {
+                      struct rb_node *y = w->rb_link[1];
+                      y->rb_color = RB_BLACK;
+                      w->rb_color = RB_RED;
+                      w->rb_link[1] = y->rb_link[0];
+                      y->rb_link[0] = w;
+                      w = pa[k - 1]->rb_link[0] = y;
+                    }
+
+                  w->rb_color = pa[k - 1]->rb_color;
+                  pa[k - 1]->rb_color = RB_BLACK;
+                  w->rb_link[0]->rb_color = RB_BLACK;
+
+                  pa[k - 1]->rb_link[0] = w->rb_link[1];
+                  w->rb_link[1] = pa[k - 1];
+                  pa[k - 2]->rb_link[da[k - 2]] = w;
+                  break;
+                }
+            }
+
+          k--;
+        }
+
+    }
+
+  tree->rb_alloc->libavl_free (tree->rb_alloc, p);
+  tree->rb_count--;
+  tree->rb_generation++;
+  return (void *) item;
+}
+
+/* Refreshes the stack of parent pointers in |trav|
+   and updates its generation number. */
+static void
+trav_refresh (struct rb_traverser *trav)
+{
+  assert (trav != NULL);
+
+  trav->rb_generation = trav->rb_table->rb_generation;
+
+  if (trav->rb_node != NULL)
+    {
+      rb_comparison_func *cmp = trav->rb_table->rb_compare;
+      void *param = trav->rb_table->rb_param;
+      struct rb_node *node = trav->rb_node;
+      struct rb_node *i;
+
+      trav->rb_height = 0;
+      for (i = trav->rb_table->rb_root; i != node; )
+        {
+          assert (trav->rb_height < RB_MAX_HEIGHT);
+          assert (i != NULL);
+
+          trav->rb_stack[trav->rb_height++] = i;
+          i = i->rb_link[cmp (node->rb_data, i->rb_data, param) > 0];
+        }
+    }
+}
+
+/* Initializes |trav| for use with |tree|
+   and selects the null node. */
+void
+rb_t_init (struct rb_traverser *trav, struct rb_table *tree)
+{
+  trav->rb_table = tree;
+  trav->rb_node = NULL;
+  trav->rb_height = 0;
+  trav->rb_generation = tree->rb_generation;
+}
+
+/* Initializes |trav| for |tree|
+   and selects and returns a pointer to its least-valued item.
+   Returns |NULL| if |tree| contains no nodes. */
+void *
+rb_t_first (struct rb_traverser *trav, struct rb_table *tree)
+{
+  struct rb_node *x;
+
+  assert (tree != NULL && trav != NULL);
+
+  trav->rb_table = tree;
+  trav->rb_height = 0;
+  trav->rb_generation = tree->rb_generation;
+
+  x = tree->rb_root;
+  if (x != NULL)
+    while (x->rb_link[0] != NULL)
+      {
+        assert (trav->rb_height < RB_MAX_HEIGHT);
+        trav->rb_stack[trav->rb_height++] = x;
+        x = x->rb_link[0];
+      }
+  trav->rb_node = x;
+
+  return x != NULL ? x->rb_data : NULL;
+}
+
+/* Initializes |trav| for |tree|
+   and selects and returns a pointer to its greatest-valued item.
+   Returns |NULL| if |tree| contains no nodes. */
+void *
+rb_t_last (struct rb_traverser *trav, struct rb_table *tree)
+{
+  struct rb_node *x;
+
+  assert (tree != NULL && trav != NULL);
+
+  trav->rb_table = tree;
+  trav->rb_height = 0;
+  trav->rb_generation = tree->rb_generation;
+
+  x = tree->rb_root;
+  if (x != NULL)
+    while (x->rb_link[1] != NULL)
+      {
+        assert (trav->rb_height < RB_MAX_HEIGHT);
+        trav->rb_stack[trav->rb_height++] = x;
+        x = x->rb_link[1];
+      }
+  trav->rb_node = x;
+
+  return x != NULL ? x->rb_data : NULL;
+}
+
+/* Searches for |item| in |tree|.
+   If found, initializes |trav| to the item found and returns the item
+   as well.
+   If there is no matching item, initializes |trav| to the null item
+   and returns |NULL|. */
+void *
+rb_t_find (struct rb_traverser *trav, struct rb_table *tree, void *item)
+{
+  struct rb_node *p, *q;
+
+  assert (trav != NULL && tree != NULL && item != NULL);
+  trav->rb_table = tree;
+  trav->rb_height = 0;
+  trav->rb_generation = tree->rb_generation;
+  for (p = tree->rb_root; p != NULL; p = q)
+    {
+      int cmp = tree->rb_compare (item, p->rb_data, tree->rb_param);
+
+      if (cmp < 0)
+        q = p->rb_link[0];
+      else if (cmp > 0)
+        q = p->rb_link[1];
+      else /* |cmp == 0| */
+        {
+          trav->rb_node = p;
+          return p->rb_data;
+        }
+
+      assert (trav->rb_height < RB_MAX_HEIGHT);
+      trav->rb_stack[trav->rb_height++] = p;
+    }
+
+  trav->rb_height = 0;
+  trav->rb_node = NULL;
+  return NULL;
+}
+
+/* Attempts to insert |item| into |tree|.
+   If |item| is inserted successfully, it is returned and |trav| is
+   initialized to its location.
+   If a duplicate is found, it is returned and |trav| is initialized to
+   its location.  No replacement of the item occurs.
+   If a memory allocation failure occurs, |NULL| is returned and |trav|
+   is initialized to the null item. */
+void *
+rb_t_insert (struct rb_traverser *trav, struct rb_table *tree, void *item)
+{
+  void **p;
+
+  assert (trav != NULL && tree != NULL && item != NULL);
+
+  p = rb_probe (tree, item);
+  if (p != NULL)
+    {
+      trav->rb_table = tree;
+      trav->rb_node =
+        ((struct rb_node *)
+         ((char *) p - offsetof (struct rb_node, rb_data)));
+      trav->rb_generation = tree->rb_generation - 1;
+      return *p;
+    }
+  else
+    {
+      rb_t_init (trav, tree);
+      return NULL;
+    }
+}
+
+/* Initializes |trav| to have the same current node as |src|. */
+void *
+rb_t_copy (struct rb_traverser *trav, const struct rb_traverser *src)
+{
+  assert (trav != NULL && src != NULL);
+
+  if (trav != src)
+    {
+      trav->rb_table = src->rb_table;
+      trav->rb_node = src->rb_node;
+      trav->rb_generation = src->rb_generation;
+      if (trav->rb_generation == trav->rb_table->rb_generation)
+        {
+          trav->rb_height = src->rb_height;
+          memcpy (trav->rb_stack, (const void *) src->rb_stack,
+                  sizeof *trav->rb_stack * trav->rb_height);
+        }
+    }
+
+  return trav->rb_node != NULL ? trav->rb_node->rb_data : NULL;
+}
+
+/* Returns the next data item in inorder
+   within the tree being traversed with |trav|,
+   or if there are no more data items returns |NULL|. */
+void *
+rb_t_next (struct rb_traverser *trav)
+{
+  struct rb_node *x;
+
+  assert (trav != NULL);
+
+  if (trav->rb_generation != trav->rb_table->rb_generation)
+    trav_refresh (trav);
+
+  x = trav->rb_node;
+  if (x == NULL)
+    {
+      return rb_t_first (trav, trav->rb_table);
+    }
+  else if (x->rb_link[1] != NULL)
+    {
+      assert (trav->rb_height < RB_MAX_HEIGHT);
+      trav->rb_stack[trav->rb_height++] = x;
+      x = x->rb_link[1];
+
+      while (x->rb_link[0] != NULL)
+        {
+          assert (trav->rb_height < RB_MAX_HEIGHT);
+          trav->rb_stack[trav->rb_height++] = x;
+          x = x->rb_link[0];
+        }
+    }
+  else
+    {
+      struct rb_node *y;
+
+      do
+        {
+          if (trav->rb_height == 0)
+            {
+              trav->rb_node = NULL;
+              return NULL;
+            }
+
+          y = x;
+          x = trav->rb_stack[--trav->rb_height];
+        }
+      while (y == x->rb_link[1]);
+    }
+  trav->rb_node = x;
+
+  return x->rb_data;
+}
+
+/* Returns the previous data item in inorder
+   within the tree being traversed with |trav|,
+   or if there are no more data items returns |NULL|. */
+void *
+rb_t_prev (struct rb_traverser *trav)
+{
+  struct rb_node *x;
+
+  assert (trav != NULL);
+
+  if (trav->rb_generation != trav->rb_table->rb_generation)
+    trav_refresh (trav);
+
+  x = trav->rb_node;
+  if (x == NULL)
+    {
+      return rb_t_last (trav, trav->rb_table);
+    }
+  else if (x->rb_link[0] != NULL)
+    {
+      assert (trav->rb_height < RB_MAX_HEIGHT);
+      trav->rb_stack[trav->rb_height++] = x;
+      x = x->rb_link[0];
+
+      while (x->rb_link[1] != NULL)
+        {
+          assert (trav->rb_height < RB_MAX_HEIGHT);
+          trav->rb_stack[trav->rb_height++] = x;
+          x = x->rb_link[1];
+        }
+    }
+  else
+    {
+      struct rb_node *y;
+
+      do
+        {
+          if (trav->rb_height == 0)
+            {
+              trav->rb_node = NULL;
+              return NULL;
+            }
+
+          y = x;
+          x = trav->rb_stack[--trav->rb_height];
+        }
+      while (y == x->rb_link[0]);
+    }
+  trav->rb_node = x;
+
+  return x->rb_data;
+}
+
+/* Returns |trav|'s current item. */
+void *
+rb_t_cur (struct rb_traverser *trav)
+{
+  assert (trav != NULL);
+
+  return trav->rb_node != NULL ? trav->rb_node->rb_data : NULL;
+}
+
+/* Replaces the current item in |trav| by |new| and returns the item replaced.
+   |trav| must not have the null item selected.
+   The new item must not upset the ordering of the tree. */
+void *
+rb_t_replace (struct rb_traverser *trav, void *new)
+{
+  void *old;
+
+  assert (trav != NULL && trav->rb_node != NULL && new != NULL);
+  old = trav->rb_node->rb_data;
+  trav->rb_node->rb_data = new;
+  return old;
+}
+
+/* Destroys |new| with |rb_destroy (new, destroy)|,
+   first setting right links of nodes in |stack| within |new|
+   to null pointers to avoid touching uninitialized data. */
+static void
+copy_error_recovery (struct rb_node **stack, int height,
+                     struct rb_table *new, rb_item_func *destroy)
+{
+  assert (stack != NULL && height >= 0 && new != NULL);
+
+  for (; height > 2; height -= 2)
+    stack[height - 1]->rb_link[1] = NULL;
+  rb_destroy (new, destroy);
+}
+
+/* Copies |org| to a newly created tree, which is returned.
+   If |copy != NULL|, each data item in |org| is first passed to |copy|,
+   and the return values are inserted into the tree,
+   with |NULL| return values taken as indications of failure.
+   On failure, destroys the partially created new tree,
+   applying |destroy|, if non-null, to each item in the new tree so far,
+   and returns |NULL|.
+   If |allocator != NULL|, it is used for allocation in the new tree.
+   Otherwise, the same allocator used for |org| is used. */
+struct rb_table *
+rb_copy (const struct rb_table *org, rb_copy_func *copy,
+          rb_item_func *destroy, struct libavl_allocator *allocator)
+{
+  struct rb_node *stack[2 * (RB_MAX_HEIGHT + 1)];
+  int height = 0;
+
+  struct rb_table *new;
+  const struct rb_node *x;
+  struct rb_node *y;
+
+  assert (org != NULL);
+  new = rb_create (org->rb_compare, org->rb_param,
+                    allocator != NULL ? allocator : org->rb_alloc);
+  if (new == NULL)
+    return NULL;
+  new->rb_count = org->rb_count;
+  if (new->rb_count == 0)
+    return new;
+
+  x = (const struct rb_node *) &org->rb_root;
+  y = (struct rb_node *) &new->rb_root;
+  for (;;)
+    {
+      while (x->rb_link[0] != NULL)
+        {
+          assert (height < 2 * (RB_MAX_HEIGHT + 1));
+
+          y->rb_link[0] =
+            new->rb_alloc->libavl_malloc (new->rb_alloc,
+                                           sizeof *y->rb_link[0]);
+          if (y->rb_link[0] == NULL)
+            {
+              if (y != (struct rb_node *) &new->rb_root)
+                {
+                  y->rb_data = NULL;
+                  y->rb_link[1] = NULL;
+                }
+
+              copy_error_recovery (stack, height, new, destroy);
+              return NULL;
+            }
+
+          stack[height++] = (struct rb_node *) x;
+          stack[height++] = y;
+          x = x->rb_link[0];
+          y = y->rb_link[0];
+        }
+      y->rb_link[0] = NULL;
+
+      for (;;)
+        {
+          y->rb_color = x->rb_color;
+          if (copy == NULL)
+            y->rb_data = x->rb_data;
+          else
+            {
+              y->rb_data = copy (x->rb_data, org->rb_param);
+              if (y->rb_data == NULL)
+                {
+                  y->rb_link[1] = NULL;
+                  copy_error_recovery (stack, height, new, destroy);
+                  return NULL;
+                }
+            }
+
+          if (x->rb_link[1] != NULL)
+            {
+              y->rb_link[1] =
+                new->rb_alloc->libavl_malloc (new->rb_alloc,
+                                               sizeof *y->rb_link[1]);
+              if (y->rb_link[1] == NULL)
+                {
+                  copy_error_recovery (stack, height, new, destroy);
+                  return NULL;
+                }
+
+              x = x->rb_link[1];
+              y = y->rb_link[1];
+              break;
+            }
+          else
+            y->rb_link[1] = NULL;
+
+          if (height <= 2)
+            return new;
+
+          y = stack[--height];
+          x = stack[--height];
+        }
+    }
+}
+
+/* Frees storage allocated for |tree|.
+   If |destroy != NULL|, applies it to each data item in inorder. */
+void
+rb_destroy (struct rb_table *tree, rb_item_func *destroy)
+{
+  struct rb_node *p, *q;
+
+  assert (tree != NULL);
+
+  for (p = tree->rb_root; p != NULL; p = q)
+    if (p->rb_link[0] == NULL)
+      {
+        q = p->rb_link[1];
+        if (destroy != NULL && p->rb_data != NULL)
+          destroy (p->rb_data, tree->rb_param);
+        tree->rb_alloc->libavl_free (tree->rb_alloc, p);
+      }
+    else
+      {
+        q = p->rb_link[0];
+        p->rb_link[0] = q->rb_link[1];
+        q->rb_link[1] = p;
+      }
+
+  tree->rb_alloc->libavl_free (tree->rb_alloc, tree);
+}
+
+/* Allocates |size| bytes of space using |malloc()|.
+   Returns a null pointer if allocation fails. */
+void *
+rb_malloc (struct libavl_allocator *allocator, size_t size)
+{
+  assert (allocator != NULL && size > 0);
+  return malloc (size);
+}
+
+/* Frees |block|. */
+void
+rb_free (struct libavl_allocator *allocator, void *block)
+{
+  assert (allocator != NULL && block != NULL);
+  free (block);
+}
+
+/* Default memory allocator that uses |malloc()| and |free()|. */
+struct libavl_allocator rb_allocator_default =
+  {
+    rb_malloc,
+    rb_free
+  };
+
+#undef NDEBUG
+#include <assert.h>
+
+/* Asserts that |rb_insert()| succeeds at inserting |item| into |table|. */
+void
+(rb_assert_insert) (struct rb_table *table, void *item)
+{
+  void **p = rb_probe (table, item);
+  assert (p != NULL && *p == item);
+}
+
+/* Asserts that |rb_delete()| really removes |item| from |table|,
+   and returns the removed item. */
+void *
+(rb_assert_delete) (struct rb_table *table, void *item)
+{
+  void *p = rb_delete (table, item);
+  assert (p != NULL);
+  return p;
+}
+
diff --git a/contrib/rbtree/rb.h b/contrib/rbtree/rb.h
new file mode 100644
index 000000000..c8858b556
--- /dev/null
+++ b/contrib/rbtree/rb.h
@@ -0,0 +1,122 @@
+/* Produced by texiweb from libavl.w. */
+
+/* libavl - library for manipulation of binary trees.
+   Copyright (C) 1998-2002, 2004 Free Software Foundation, Inc.
+
+   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 2 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, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+   02111-1307, USA.
+
+   The author may be contacted at <blp@gnu.org> on the Internet, or
+   write to Ben Pfaff, Stanford University, Computer Science Dept., 353
+   Serra Mall, Stanford CA 94305, USA.
+*/
+
+#ifndef RB_H
+#define RB_H 1
+
+#include <stddef.h>
+
+/* Function types. */
+typedef int rb_comparison_func (const void *rb_a, const void *rb_b,
+                                 void *rb_param);
+typedef void rb_item_func (void *rb_item, void *rb_param);
+typedef void *rb_copy_func (void *rb_item, void *rb_param);
+
+#ifndef LIBAVL_ALLOCATOR
+#define LIBAVL_ALLOCATOR
+/* Memory allocator. */
+struct libavl_allocator
+  {
+    void *(*libavl_malloc) (struct libavl_allocator *, size_t libavl_size);
+    void (*libavl_free) (struct libavl_allocator *, void *libavl_block);
+  };
+#endif
+
+/* Default memory allocator. */
+extern struct libavl_allocator rb_allocator_default;
+void *rb_malloc (struct libavl_allocator *, size_t);
+void rb_free (struct libavl_allocator *, void *);
+
+/* Maximum RB height. */
+#ifndef RB_MAX_HEIGHT
+#define RB_MAX_HEIGHT 48
+#endif
+
+/* Tree data structure. */
+struct rb_table
+  {
+    struct rb_node *rb_root;          /* Tree's root. */
+    rb_comparison_func *rb_compare;   /* Comparison function. */
+    void *rb_param;                    /* Extra argument to |rb_compare|. */
+    struct libavl_allocator *rb_alloc; /* Memory allocator. */
+    size_t rb_count;                   /* Number of items in tree. */
+    unsigned long rb_generation;       /* Generation number. */
+  };
+
+/* Color of a red-black node. */
+enum rb_color
+  {
+    RB_BLACK,   /* Black. */
+    RB_RED      /* Red. */
+  };
+
+/* A red-black tree node. */
+struct rb_node
+  {
+    struct rb_node *rb_link[2];   /* Subtrees. */
+    void *rb_data;                /* Pointer to data. */
+    unsigned char rb_color;       /* Color. */
+  };
+
+/* RB traverser structure. */
+struct rb_traverser
+  {
+    struct rb_table *rb_table;        /* Tree being traversed. */
+    struct rb_node *rb_node;          /* Current node in tree. */
+    struct rb_node *rb_stack[RB_MAX_HEIGHT];
+                                        /* All the nodes above |rb_node|. */
+    size_t rb_height;                  /* Number of nodes in |rb_parent|. */
+    unsigned long rb_generation;       /* Generation number. */
+  };
+
+/* Table functions. */
+struct rb_table *rb_create (rb_comparison_func *, void *,
+                              struct libavl_allocator *);
+struct rb_table *rb_copy (const struct rb_table *, rb_copy_func *,
+                            rb_item_func *, struct libavl_allocator *);
+void rb_destroy (struct rb_table *, rb_item_func *);
+void **rb_probe (struct rb_table *, void *);
+void *rb_insert (struct rb_table *, void *);
+void *rb_replace (struct rb_table *, void *);
+void *rb_delete (struct rb_table *, const void *);
+void *rb_find (const struct rb_table *, const void *);
+void rb_assert_insert (struct rb_table *, void *);
+void *rb_assert_delete (struct rb_table *, void *);
+
+#define rb_count(table) ((size_t) (table)->rb_count)
+
+/* Table traverser functions. */
+void rb_t_init (struct rb_traverser *, struct rb_table *);
+void *rb_t_first (struct rb_traverser *, struct rb_table *);
+void *rb_t_last (struct rb_traverser *, struct rb_table *);
+void *rb_t_find (struct rb_traverser *, struct rb_table *, void *);
+void *rb_t_insert (struct rb_traverser *, struct rb_table *, void *);
+void *rb_t_copy (struct rb_traverser *, const struct rb_traverser *);
+void *rb_t_next (struct rb_traverser *);
+void *rb_t_prev (struct rb_traverser *);
+void *rb_t_cur (struct rb_traverser *);
+void *rb_t_replace (struct rb_traverser *, void *);
+
+#endif /* rb.h */