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
49 lines
1.1 KiB
C
49 lines
1.1 KiB
C
/* $NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 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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* 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: tfind.c,v 1.2 1999/09/16 11:45:37 lukem 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 <stdlib.h>
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#include <search.h>
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/*
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* find a node, or return 0
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*
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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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posix_tnode *
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tfind(const void *vkey, posix_tnode * const *rootp,
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int (*compar)(const void *, const void *))
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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;
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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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