misc/tsearch.c

   1 /* Copyright (C) 1995 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17 Boston, MA 02111-1307, USA.  */
  18
  19 /* Tree search generalized from Knuth (6.2.2) Algorithm T just like
  20    the AT&T man page says.
  21
  22    The node_t structure is for internal use only, lint doesn't grok it.
  23
  24    Written by reading the System V Interface Definition, not the code.
  25
  26    Totally public domain.  */
  27 /*LINTLIBRARY*/
  28
  29 #include <stdlib.h>
  30 #include <search.h>
  31
  32 /* This routine is not very bad.  It makes many assumptions about
  33    the compiler. It assumpts that the first field in node must be
  34    the "key" field, which points to the datum. It is a very trick
  35    stuff. H.J.  */
  36
  37 typedef struct node_t
  38 {
  39   const void *key;
  40   struct node_t *left;
  41   struct node_t *right;
  42 }
  43 node;
  44
  45 /* Prototype fpr local function.  */
  46 static void trecurse __P ((const void *vroot, __action_fn_t action, int level));
  47
  48
  49 /* find or insert datum into search tree.
  50 char    *key;            key to be located
  51 node    **rootp;         address of tree root
  52 int     (*compar)();     ordering function
  53 */
  54 void *
  55 tsearch (key, vrootp, compar)
  56      const void *key;
  57      void **vrootp;
  58      __compar_fn_t compar;
  59 {
  60   node *q;
  61   node **rootp = (node **) vrootp;
  62
  63   if (rootp == NULL)
  64     return NULL;
  65
  66   while (*rootp != NULL)                /* Knuth's T1: */
  67     {
  68       int r;
  69
  70       r = (*compar) (key, (*rootp)->key);
  71       if (r == 0)                       /* T2: */
  72         return *rootp;                  /* we found it! */
  73       rootp = (r < 0)
  74               ? &(*rootp)->left         /* T3: follow left branch */
  75               : &(*rootp)->right;       /* T4: follow right branch */
  76     }
  77
  78   q = (node *) malloc (sizeof (node));  /* T5: key not found */
  79   if (q != NULL)                        /* make new node */
  80     {
  81       *rootp = q;                       /* link new node to old */
  82       q->key = key;                     /* initialize new node */
  83       q->left = q->right = NULL;
  84     }
  85
  86   return q;
  87 }
  88
  89
  90 void *
  91 tfind (key, vrootp, compar)
  92      const void *key;
  93      const void **vrootp;
  94      __compar_fn_t compar;
  95 {
  96   node **rootp = (node **) vrootp;
  97
  98   if (rootp == NULL)
  99     return NULL;
 100
 101   while (*rootp != NULL)                /* Knuth's T1: */
 102     {
 103       int r;
 104
 105       r = (*compar)(key, (*rootp)->key);
 106       if (r == 0)                       /* T2: */
 107         return *rootp;                  /* we found it! */
 108
 109       rootp = (r < 0)
 110               ? &(*rootp)->left         /* T3: follow left branch */
 111               : &(*rootp)->right;       /* T4: follow right branch */
 112     }
 113     return NULL;
 114 }
 115
 116
 117 /* delete node with given key
 118 char    *key;           key to be deleted
 119 node    **rootp;        address of the root of tree
 120 int     (*compar)();    comparison function
 121 */
 122 void *
 123 tdelete (key, vrootp, compar)
 124      const void *key;
 125      void **vrootp;
 126      __compar_fn_t compar;
 127 {
 128   node *p;
 129   node *q;
 130   node *r;
 131   int cmp;
 132   node **rootp = (node **) vrootp;
 133
 134   if (rootp == NULL || (p = *rootp) == NULL)
 135     return NULL;
 136
 137   while ((cmp = (*compar) (key, (*rootp)->key)) != 0)
 138     {
 139       p = *rootp;
 140       rootp = (cmp < 0)
 141               ? &(*rootp)->left         /* follow left branch */
 142               : &(*rootp)->right;       /* follow right branch */
 143       if (*rootp == NULL)
 144         return NULL;                    /* key not found */
 145     }
 146
 147   r = (*rootp)->right;                  /* D1: */
 148   q = (*rootp)->left;
 149   if (q == NULL)                        /* Left NULL? */
 150     q = r;
 151   else if (r != NULL)                   /* Right link is NULL? */
 152     {
 153       if (r->left == NULL)              /* D2: Find successor */
 154         {
 155           r->left = q;
 156           q = r;
 157         }
 158       else
 159         {                               /* D3: Find (struct node_t *)0 link */
 160           for (q = r->left; q->left != NULL; q = r->left)
 161             r = q;
 162           r->left = q->right;
 163           q->left = (*rootp)->left;
 164           q->right = (*rootp)->right;
 165         }
 166     }
 167   free ((struct node_t *) *rootp);      /* D4: Free node */
 168   *rootp = q;                           /* link parent to new node */
 169   return p;
 170 }
 171
 172
 173 /* Walk the nodes of a tree
 174 node    *root;          Root of the tree to be walked
 175 void    (*action)();    Function to be called at each node
 176 int     level;
 177 */
 178 static void
 179 trecurse (vroot, action, level)
 180      const void *vroot;
 181      __action_fn_t action;
 182      int level;
 183 {
 184   node *root = (node *) vroot;
 185
 186   if (root->left == NULL && root->right == NULL)
 187     (*action) (root, leaf, level);
 188   else
 189     {
 190       (*action) (root, preorder, level);
 191       if (root->left != NULL)
 192         trecurse (root->left, action, level + 1);
 193       (*action) (root, postorder, level);
 194       if (root->right != NULL)
 195         trecurse (root->right, action, level + 1);
 196       (*action) (root, endorder, level);
 197     }
 198 }
 199
 200
 201 /* void twalk(root, action)     Walk the nodes of a tree
 202 node    *root;                  Root of the tree to be walked
 203 void    (*action)();            Function to be called at each node
 204 PTR
 205 */
 206 void
 207 twalk (vroot, action)
 208      const void *vroot;
 209      __action_fn_t action;
 210 {
 211   const node *root = (node *) vroot;
 212
 213   if (root != NULL && action != NULL)
 214     trecurse (root, action, 0);
 215 }