lib/roken/tsearch.c

   1 /*
   2  * Tree search generalized from Knuth (6.2.2) Algorithm T just like
   3  * the AT&T man page says.
   4  *
   5  * The node_t structure is for internal use only, lint doesn't grok it.
   6  *
   7  * Written by reading the System V Interface Definition, not the code.
   8  *
   9  * Totally public domain.
  10  *
  11  * $NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $
  12  * $NetBSD: twalk.c,v 1.1 1999/02/22 10:33:16 christos Exp $
  13  * $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
  14  * $NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
  15  */
  16
  17 #include <config.h>
  18 #include "roken.h"
  19 #include "search.h"
  20 #include <stdlib.h>
  21
  22 typedef struct node {
  23   char         *key;
  24   struct node  *llink, *rlink;
  25 } node_t;
  26
  27 #ifndef __DECONST
  28 #define __DECONST(type, var)    ((type)(uintptr_t)(const void *)(var))
  29 #endif
  30
  31 /*
  32  * find or insert datum into search tree
  33  *
  34  * Parameters:
  35  *      vkey:   key to be located
  36  *      vrootp: address of tree root
  37  */
  38
  39 ROKEN_LIB_FUNCTION void *
  40 rk_tsearch(const void *vkey, void **vrootp,
  41         int (*compar)(const void *, const void *))
  42 {
  43         node_t *q;
  44         node_t **rootp = (node_t **)vrootp;
  45
  46         if (rootp == NULL)
  47                 return NULL;
  48
  49         while (*rootp != NULL) {        /* Knuth's T1: */
  50                 int r;
  51
  52                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
  53                         return *rootp;          /* we found it! */
  54
  55                 rootp = (r < 0) ?
  56                     &(*rootp)->llink :          /* T3: follow left branch */
  57                     &(*rootp)->rlink;           /* T4: follow right branch */
  58         }
  59
  60         q = malloc(sizeof(node_t));             /* T5: key not found */
  61         if (q != 0) {                           /* make new node */
  62                 *rootp = q;                     /* link new node to old */
  63                 /* LINTED const castaway ok */
  64                 q->key = __DECONST(void *, vkey); /* initialize new node */
  65                 q->llink = q->rlink = NULL;
  66         }
  67         return q;
  68 }
  69
  70 /*
  71  * Walk the nodes of a tree
  72  *
  73  * Parameters:
  74  *      root:   Root of the tree to be walked
  75  */
  76 static void
  77 trecurse(const node_t *root, void (*action)(const void *, VISIT, int),
  78          int level)
  79 {
  80
  81         if (root->llink == NULL && root->rlink == NULL)
  82                 (*action)(root, leaf, level);
  83         else {
  84                 (*action)(root, preorder, level);
  85                 if (root->llink != NULL)
  86                         trecurse(root->llink, action, level + 1);
  87                 (*action)(root, postorder, level);
  88                 if (root->rlink != NULL)
  89                         trecurse(root->rlink, action, level + 1);
  90                 (*action)(root, endorder, level);
  91         }
  92 }
  93
  94 /*
  95  * Walk the nodes of a tree
  96  *
  97  * Parameters:
  98  *      vroot:  Root of the tree to be walked
  99  */
 100 ROKEN_LIB_FUNCTION void
 101 rk_twalk(const void *vroot,
 102       void (*action)(const void *, VISIT, int))
 103 {
 104         if (vroot != NULL && action != NULL)
 105                 trecurse(vroot, action, 0);
 106 }
 107
 108 /*
 109  * delete node with given key
 110  *
 111  * vkey:   key to be deleted
 112  * vrootp: address of the root of the tree
 113  * compar: function to carry out node comparisons
 114  */
 115 ROKEN_LIB_FUNCTION void *
 116 rk_tdelete(const void * vkey, void ** vrootp,
 117         int (*compar)(const void *, const void *))
 118 {
 119         node_t **rootp = (node_t **)vrootp;
 120         node_t *p, *q, *r;
 121         int cmp;
 122
 123         if (rootp == NULL || (p = *rootp) == NULL)
 124                 return NULL;
 125
 126         while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
 127                 p = *rootp;
 128                 rootp = (cmp < 0) ?
 129                     &(*rootp)->llink :          /* follow llink branch */
 130                     &(*rootp)->rlink;           /* follow rlink branch */
 131                 if (*rootp == NULL)
 132                         return NULL;            /* key not found */
 133         }
 134         r = (*rootp)->rlink;                    /* D1: */
 135         if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */
 136                 q = r;
 137         else if (r != NULL) {                   /* Right link is NULL? */
 138                 if (r->llink == NULL) {         /* D2: Find successor */
 139                         r->llink = q;
 140                         q = r;
 141                 } else {                        /* D3: Find NULL link */
 142                         for (q = r->llink; q->llink != NULL; q = r->llink)
 143                                 r = q;
 144                         r->llink = q->rlink;
 145                         q->llink = (*rootp)->llink;
 146                         q->rlink = (*rootp)->rlink;
 147                 }
 148         }
 149         free(*rootp);                           /* D4: Free node */
 150         *rootp = q;                             /* link parent to new node */
 151         return p;
 152 }
 153
 154 /*
 155  * find a node, or return 0
 156  *
 157  * Parameters:
 158  *      vkey:   key to be found
 159  *      vrootp: address of the tree root
 160  */
 161 ROKEN_LIB_FUNCTION void *
 162 rk_tfind(const void *vkey, void * const *vrootp,
 163       int (*compar)(const void *, const void *))
 164 {
 165         node_t **rootp = (node_t **)vrootp;
 166
 167         if (rootp == NULL)
 168                 return NULL;
 169
 170         while (*rootp != NULL) {                /* T1: */
 171                 int r;
 172
 173                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
 174                         return *rootp;          /* key found */
 175                 rootp = (r < 0) ?
 176                     &(*rootp)->llink :          /* T3: follow left branch */
 177                     &(*rootp)->rlink;           /* T4: follow right branch */
 178         }
 179         return NULL;
 180 }