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