1 /* $NetBSD: tsearch.c,v 1.1 1999/02/22 10:33:16 christos Exp $ */ 2 3 /* 4 * Tree search generalized from Knuth (6.2.2) Algorithm T just like 5 * the AT&T man page says. 6 * 7 * The node_t structure is for internal use only, lint doesn't grok it. 8 * 9 * Written by reading the System V Interface Definition, not the code. 10 * 11 * Totally public domain. 12 */ 13 14 #include <sys/cdefs.h> 15 #if defined(LIBC_SCCS) && !defined(lint) 16 __RCSID("$NetBSD: tsearch.c,v 1.1 1999/02/22 10:33:16 christos Exp $"); 17 #endif /* LIBC_SCCS and not lint */ 18 19 #define _SEARCH_PRIVATE 20 #include <search.h> 21 #include <stdlib.h> 22 23 /* find or insert datum into search tree */ 24 void * 25 tsearch(vkey, vrootp, compar) 26 const void *vkey; /* key to be located */ 27 void **vrootp; /* address of tree root */ 28 int (*compar) __P((const void *, const void *)); 29 { 30 node_t *q; 31 node_t **rootp = (node_t **)vrootp; 32 33 if (rootp == NULL) 34 return NULL; 35 36 while (*rootp != NULL) { /* Knuth's T1: */ 37 int r; 38 39 if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */ 40 return *rootp; /* we found it! */ 41 42 rootp = (r < 0) ? 43 &(*rootp)->llink : /* T3: follow left branch */ 44 &(*rootp)->rlink; /* T4: follow right branch */ 45 } 46 47 q = malloc(sizeof(node_t)); /* T5: key not found */ 48 if (q != 0) { /* make new node */ 49 *rootp = q; /* link new node to old */ 50 q->key = (void *)vkey; /* initialize new node */ 51 q->llink = q->rlink = NULL; 52 } 53 return q; 54 } 55