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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);
+}