39 lines
1.0 KiB
C
39 lines
1.0 KiB
C
#if !defined(lint) && defined(SCCSIDS)
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static char sccsid[] = "@(#)tfind.c 1.1 92/07/30 SMI"; /* from S5R2 1.2 */
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#endif
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/*LINTLIBRARY*/
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/*
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* Tree search algorithm, generalized from Knuth (6.2.2) Algorithm T.
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*
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* The NODE * arguments are declared in the lint files as char *,
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* because the definition of NODE isn't available to the user.
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*/
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#include <search.h>
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typedef char *POINTER;
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typedef struct node { POINTER key; struct node *llink, *rlink; } NODE;
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#define NULL 0
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/* tfind - find a node, or return 0 */
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NODE *
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tfind(key, rootp, compar)
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POINTER key; /* Key to be located */
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register NODE **rootp; /* Address of the root of the tree */
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int (*compar)(); /* Comparison function */
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{
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if (rootp == NULL)
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return (NULL);
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while (*rootp != NULL) { /* T1: */
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int r = (*compar)(key, (*rootp)->key); /* T2: */
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if (r == 0)
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return (*rootp); /* Key found */
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rootp = (r < 0) ?
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&(*rootp)->llink : /* T3: Take left branch */
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&(*rootp)->rlink; /* T4: Take right branch */
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}
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return (NODE *)(NULL);
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}
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