1 /* $NetBSD: tsearch.c,v 1.5 2005/11/29 03:12:00 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 1.5 2005/11/29 03:12:00 christos Exp $"); 17 #endif /* LIBC_SCCS and not lint */ 18 19 #include <assert.h> 20 #define _SEARCH_PRIVATE 21 #include <search.h> 22 #include <stdlib.h> 23 24 /* find or insert datum into search tree */ 25 void * 26 tsearch(vkey, vrootp, compar) 27 const void *vkey; /* key to be located */ 28 void **vrootp; /* address of tree root */ 29 int (*compar) __P((const void *, const void *)); 30 { 31 node_t *q; 32 node_t **rootp = (node_t **)vrootp; 33 34 _DIAGASSERT(vkey != NULL); 35 _DIAGASSERT(compar != NULL); 36 37 if (rootp == NULL) 38 return NULL; 39 40 while (*rootp != NULL) { /* Knuth's T1: */ 41 int r; 42 43 if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */ 44 return *rootp; /* we found it! */ 45 46 rootp = (r < 0) ? 47 &(*rootp)->llink : /* T3: follow left branch */ 48 &(*rootp)->rlink; /* T4: follow right branch */ 49 } 50 51 q = malloc(sizeof(node_t)); /* T5: key not found */ 52 if (q != 0) { /* make new node */ 53 *rootp = q; /* link new node to old */ 54 q->key = __UNCONST(vkey); /* initialize new node */ 55 q->llink = q->rlink = NULL; 56 } 57 return q; 58 } 59