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 * $FreeBSD: src/lib/libc/stdlib/tsearch.c,v 1.4 2003/01/05 02:43:18 tjr Exp $ 13 * $DragonFly: src/lib/libc/stdlib/tsearch.c,v 1.6 2005/11/24 17:18:30 swildner Exp $ 14 */ 15 16 #define _SEARCH_PRIVATE 17 #include <search.h> 18 #include <stdlib.h> 19 20 /* 21 * find or insert datum into search tree 22 * 23 * Parameters: 24 * vkey: key to be located 25 * vrootp: address of tree root 26 */ 27 28 void * 29 tsearch(const void *vkey, void **vrootp, 30 int (*compar)(const void *, const void *)) 31 { 32 node_t *q; 33 node_t **rootp = (node_t **)vrootp; 34 35 if (rootp == NULL) 36 return NULL; 37 38 while (*rootp != NULL) { /* Knuth's T1: */ 39 int r; 40 41 if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */ 42 return *rootp; /* we found it! */ 43 44 rootp = (r < 0) ? 45 &(*rootp)->llink : /* T3: follow left branch */ 46 &(*rootp)->rlink; /* T4: follow right branch */ 47 } 48 49 q = malloc(sizeof(node_t)); /* T5: key not found */ 50 if (q != 0) { /* make new node */ 51 *rootp = q; /* link new node to old */ 52 /* LINTED const castaway ok */ 53 q->key = __DECONST(void *, vkey); /* initialize new node */ 54 q->llink = q->rlink = NULL; 55 } 56 return q; 57 } 58