52 lines
1.3 KiB
C
52 lines
1.3 KiB
C
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/* $NetBSD: tsearch.c,v 1.4 1999/09/20 04:39:43 lukem Exp $ */
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/*
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* Tree search generalized from Knuth (6.2.2) Algorithm T just like
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* the AT&T man page says.
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*
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* The node_t structure is for internal use only, lint doesn't grok it.
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*
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* Written by reading the System V Interface Definition, not the code.
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*
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* Totally public domain.
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*/
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#include <assert.h>
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#define _SEARCH_PRIVATE
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#include <search.h>
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#include <stdlib.h>
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/* find or insert datum into search tree */
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void *
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tsearch(const void * __restrict__ vkey, /* key to be located */
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void ** __restrict__ vrootp, /* address of tree root */
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int (*compar) (const void *, const void *))
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{
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node_t *q;
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node_t **rootp = (node_t **)vrootp;
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if (rootp == NULL)
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return NULL;
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while (*rootp != NULL) { /* Knuth's T1: */
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int r;
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if ((r = (*compar)(vkey, (*rootp)->key)) == 0) /* T2: */
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return *rootp; /* we found it! */
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rootp = (r < 0) ?
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&(*rootp)->llink : /* T3: follow left branch */
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&(*rootp)->rlink; /* T4: follow right branch */
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}
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q = malloc(sizeof(node_t)); /* T5: key not found */
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if (q != 0) { /* make new node */
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*rootp = q; /* link new node to old */
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/* LINTED const castaway ok */
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q->key = (void *)vkey; /* initialize new node */
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q->llink = q->rlink = NULL;
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}
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return q;
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}
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