1 /* $OpenBSD: tfind.c,v 1.7 2015/09/26 16:03:48 guenther 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 8 * 9 * Written by reading the System V Interface Definition, not the code. 10 * 11 * Totally public domain. 12 */ 13 #include <search.h> 14 15 typedef struct node_t 16 { 17 char *key; 18 struct node_t *llink, *rlink; 19 } node; 20 21 /* find a node, or return 0 */ 22 void * 23 tfind(const void *vkey, void * const *vrootp, 24 int (*compar)(const void *, const void *)) 25 { 26 char *key = (char *)vkey; 27 node **rootp = (node **)vrootp; 28 29 if (rootp == (struct node_t **)0) 30 return ((struct node_t *)0); 31 while (*rootp != (struct node_t *)0) { /* T1: */ 32 int r; 33 if ((r = (*compar)(key, (*rootp)->key)) == 0) /* T2: */ 34 return (*rootp); /* key found */ 35 rootp = (r < 0) ? 36 &(*rootp)->llink : /* T3: follow left branch */ 37 &(*rootp)->rlink; /* T4: follow right branch */ 38 } 39 return (node *)0; 40 } 41
