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+/* Copyright (C) 1995 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library 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
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA.  */
+
+/* Tree search generalized from Knuth (6.2.2) Algorithm T just like
+   the AT&T man page says.
+  
+   The node_t structure is for internal use only, lint doesn't grok it.
+  
+   Written by reading the System V Interface Definition, not the code.
+  
+   Totally public domain.  */
+/*LINTLIBRARY*/
+
+#include <stdlib.h>
+#include <search.h>
+
+/* This routine is not very bad.  It makes many assumptions about
+   the compiler. It assumpts that the first field in node must be
+   the "key" field, which points to the datum. It is a very trick
+   stuff. H.J.  */
+
+typedef struct node_t
+{
+  const void *key;
+  struct node_t *left;
+  struct node_t *right;
+}
+node;
+
+/* Prototype fpr local function.  */
+static void trecurse __P ((const void *vroot, __action_fn_t action, int level));
+
+
+/* find or insert datum into search tree.
+char 	*key;		 key to be located
+node	**rootp;	 address of tree root
+int	(*compar)();	 ordering function
+*/
+void *
+tsearch (key, vrootp, compar)
+     const void *key;
+     void **vrootp;
+     __compar_fn_t compar;
+{
+  node *q;
+  node **rootp = (node **) vrootp;
+
+  if (rootp == NULL)
+    return NULL;
+
+  while (*rootp != NULL)		/* Knuth's T1: */
+    {
+      int r;
+
+      r = (*compar) (key, (*rootp)->key);
+      if (r == 0)			/* T2: */
+	return *rootp;			/* we found it! */
+      rootp = (r < 0)
+	      ? &(*rootp)->left		/* T3: follow left branch */
+	      : &(*rootp)->right;	/* T4: follow right branch */
+    }
+
+  q = (node *) malloc (sizeof (node));	/* T5: key not found */
+  if (q != NULL)			/* make new node */
+    {
+      *rootp = q;			/* link new node to old */
+      q->key = key;			/* initialize new node */
+      q->left = q->right = NULL;
+    }
+
+  return q;
+}
+
+
+void *
+tfind (key, vrootp, compar)
+     const void *key;
+     const void **vrootp;
+     __compar_fn_t compar;
+{
+  node **rootp = (node **) vrootp;
+
+  if (rootp == NULL)
+    return NULL;
+
+  while (*rootp != NULL)		/* Knuth's T1: */
+    {
+      int r;
+
+      r = (*compar)(key, (*rootp)->key);
+      if (r == 0)			/* T2: */
+	return *rootp;			/* we found it! */
+
+      rootp = (r < 0)
+	      ? &(*rootp)->left		/* T3: follow left branch */
+	      : &(*rootp)->right;	/* T4: follow right branch */
+    }
+    return NULL;
+}
+
+
+/* delete node with given key
+char	*key;		key to be deleted
+node	**rootp;	address of the root of tree
+int	(*compar)();	comparison function
+*/
+void *
+tdelete (key, vrootp, compar)
+     const void *key;
+     void **vrootp;
+     __compar_fn_t compar;
+{
+  node *p;
+  node *q;
+  node *r;
+  int cmp;
+  node **rootp = (node **) vrootp;
+
+  if (rootp == NULL || (p = *rootp) == NULL)
+    return NULL;
+
+  while ((cmp = (*compar) (key, (*rootp)->key)) != 0)
+    {
+      p = *rootp;
+      rootp = (cmp < 0)
+	      ? &(*rootp)->left		/* follow left branch */
+	      : &(*rootp)->right;	/* follow right branch */
+      if (*rootp == NULL)
+	return NULL;			/* key not found */
+    }
+
+  r = (*rootp)->right;			/* D1: */
+  q = (*rootp)->left;
+  if (q == NULL)			/* Left NULL? */
+    q = r;
+  else if (r != NULL)			/* Right link is NULL? */
+    {
+      if (r->left == NULL)		/* D2: Find successor */
+	{
+	  r->left = q;
+	  q = r;
+	}
+      else
+	{				/* D3: Find (struct node_t *)0 link */
+	  for (q = r->left; q->left != NULL; q = r->left)
+	    r = q;
+	  r->left = q->right;
+	  q->left = (*rootp)->left;
+	  q->right = (*rootp)->right;
+	}
+    }
+  free ((struct node_t *) *rootp);	/* D4: Free node */
+  *rootp = q;				/* link parent to new node */
+  return p;
+}
+
+
+/* Walk the nodes of a tree
+node	*root;		Root of the tree to be walked
+void	(*action)();	Function to be called at each node
+int	level;
+*/
+static void
+trecurse (vroot, action, level)
+     const void *vroot;
+     __action_fn_t action;
+     int level;
+{
+  node *root = (node *) vroot;
+
+  if (root->left == NULL && root->right == NULL)
+    (*action) (root, leaf, level);
+  else
+    {
+      (*action) (root, preorder, level);
+      if (root->left != NULL)
+	trecurse (root->left, action, level + 1);
+      (*action) (root, postorder, level);
+      if (root->right != NULL)
+	trecurse (root->right, action, level + 1);
+      (*action) (root, endorder, level);
+    }
+}
+
+
+/* void twalk(root, action)	Walk the nodes of a tree 
+node	*root;			Root of the tree to be walked
+void	(*action)();		Function to be called at each node
+PTR
+*/
+void
+twalk (vroot, action)
+     const void *vroot;
+     __action_fn_t action;
+{
+  const node *root = (node *) vroot;
+
+  if (root != NULL && action != NULL)
+    trecurse (root, action, 0);
+}