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tfind.c revision 1.2 
      1 /*	$NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 lukem 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: tfind.c,v 1.2 1999/09/16 11:45:37 lukem Exp $");
     17 #endif /* LIBC_SCCS and not lint */
     18 
     19 #include <assert.h>
     20 #define _SEARCH_PRIVATE
     21 #include <stdlib.h>
     22 #include <search.h>
     23 
     24 /* find a node, or return 0 */
     25 void *
     26 tfind(vkey, vrootp, compar)
     27 	const void *vkey;		/* key to be found */
     28 	void **vrootp;			/* address of the tree root */
     29 	int (*compar) __P((const void *, const void *));
     30 {
     31 	node_t **rootp = (node_t **)vrootp;
     32 
     33 	_DIAGASSERT(vkey != NULL);
     34 	_DIAGASSERT(compar != NULL);
     35 #ifdef _DIAGNOSTIC
     36 	if (vkey == NULL || compar == NULL)
     37 		return (NULL);
     38 #endif
     39 
     40 	if (rootp == NULL)
     41 		return NULL;
     42 
     43 	while (*rootp != NULL) {		/* T1: */
     44 		int r;
     45 
     46 		if ((r = (*compar)(vkey, (*rootp)->key)) == 0)	/* T2: */
     47 			return *rootp;		/* key found */
     48 		rootp = (r < 0) ?
     49 		    &(*rootp)->llink :		/* T3: follow left branch */
     50 		    &(*rootp)->rlink;		/* T4: follow right branch */
     51 	}
     52 	return NULL;
     53 }
     54