4ef9bd22ed
Back in 2015 when I reimplemented these functions to use an AVL tree, I was annoyed by the weakness of the typing of these functions. Both tree nodes and keys are represented by 'void *', meaning that things like the documentation for these functions are an absolute train wreck. To make things worse, users of these functions need to cast the return value of tfind()/tsearch() from 'void *' to 'type_of_key **' in order to access the key. Technically speaking such casts violate aliasing rules. I've observed actual breakages as a result of this by enabling features like LTO. I've filed a bug report at the Austin Group. Looking at the way the bug got resolved, they made a pretty good step in the right direction. A new type 'posix_tnode' has been added to correspond to tree nodes. It is still defined as 'void' for source-level compatibility, but in the very far future it could be replaced by a proper structure type containing a key pointer. MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D8205
51 lines
1.2 KiB
C
51 lines
1.2 KiB
C
/* $NetBSD: twalk.c,v 1.4 2012/03/20 16:38:45 matt 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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* 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 <sys/cdefs.h>
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#if 0
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#if defined(LIBC_SCCS) && !defined(lint)
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__RCSID("$NetBSD: twalk.c,v 1.4 2012/03/20 16:38:45 matt Exp $");
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#endif /* LIBC_SCCS and not lint */
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#endif
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__FBSDID("$FreeBSD$");
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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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typedef void (*cmp_fn_t)(const posix_tnode *, VISIT, int);
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/* Walk the nodes of a tree */
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static void
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trecurse(const posix_tnode *root, cmp_fn_t action, 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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/* Walk the nodes of a tree */
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void
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twalk(const posix_tnode *vroot, cmp_fn_t action)
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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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