180 lines
4.2 KiB
C
180 lines
4.2 KiB
C
/*
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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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* $NetBSD: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $
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* $NetBSD: twalk.c,v 1.1 1999/02/22 10:33:16 christos Exp $
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* $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
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* $NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
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*/
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#include <config.h>
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#include "roken.h"
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#include "search.h"
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#include <stdlib.h>
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typedef struct node {
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char *key;
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struct node *llink, *rlink;
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} node_t;
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#ifndef __DECONST
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#define __DECONST(type, var) ((type)(uintptr_t)(const void *)(var))
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#endif
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/*
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* find or insert datum into search tree
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*
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* Parameters:
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* vkey: key to be located
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* vrootp: address of tree root
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*/
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ROKEN_LIB_FUNCTION void *
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rk_tsearch(const void *vkey, void **vrootp,
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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 = __DECONST(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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/*
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* Walk the nodes of a tree
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*
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* Parameters:
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* root: Root of the tree to be walked
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*/
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static void
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trecurse(const node_t *root, void (*action)(const void *, VISIT, int),
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int level)
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{
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if (root->llink == NULL && root->rlink == NULL)
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(*action)(root, leaf, level);
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else {
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(*action)(root, preorder, level);
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if (root->llink != NULL)
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trecurse(root->llink, action, level + 1);
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(*action)(root, postorder, level);
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if (root->rlink != NULL)
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trecurse(root->rlink, action, level + 1);
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(*action)(root, endorder, level);
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}
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}
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/*
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* Walk the nodes of a tree
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*
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* Parameters:
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* vroot: Root of the tree to be walked
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*/
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ROKEN_LIB_FUNCTION void
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rk_twalk(const void *vroot,
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void (*action)(const void *, VISIT, int))
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{
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if (vroot != NULL && action != NULL)
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trecurse(vroot, action, 0);
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}
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/*
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* delete node with given key
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*
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* vkey: key to be deleted
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* vrootp: address of the root of the tree
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* compar: function to carry out node comparisons
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*/
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ROKEN_LIB_FUNCTION void *
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rk_tdelete(const void * vkey, void ** vrootp,
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int (*compar)(const void *, const void *))
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{
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node_t **rootp = (node_t **)vrootp;
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node_t *q, *r;
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int cmp;
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if (rootp == NULL || *rootp == NULL)
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return NULL;
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while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
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rootp = (cmp < 0) ?
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&(*rootp)->llink : /* follow llink branch */
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&(*rootp)->rlink; /* follow rlink branch */
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if (*rootp == NULL)
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return NULL; /* key not found */
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}
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r = (*rootp)->rlink; /* D1: */
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if ((q = (*rootp)->llink) == NULL) /* Left NULL? */
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q = r;
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else if (r != NULL) { /* Right link is NULL? */
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if (r->llink == NULL) { /* D2: Find successor */
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r->llink = q;
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q = r;
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} else { /* D3: Find NULL link */
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for (q = r->llink; q->llink != NULL; q = r->llink)
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r = q;
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r->llink = q->rlink;
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q->llink = (*rootp)->llink;
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q->rlink = (*rootp)->rlink;
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}
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}
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free(*rootp); /* D4: Free node */
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*rootp = q; /* link parent to new node */
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return *rootp;
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}
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/*
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* find a node, or return 0
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*
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* Parameters:
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* vkey: key to be found
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* vrootp: address of the tree root
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*/
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ROKEN_LIB_FUNCTION void *
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rk_tfind(const void *vkey, void * const *vrootp,
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int (*compar)(const void *, const void *))
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{
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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) { /* 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; /* key found */
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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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return NULL;
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}
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