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Message-ID: <CABh_MKnkw_Yp9ifwybXBOMb0FuPvP05T183utZ1kW6Ohqq3gvQ@mail.gmail.com>
Date: Mon, 7 Dec 2015 14:19:58 +0100
From: Ed Schouten <ed@...i.nl>
To: Ed Schouten <ed@...i.nl>, musl@...ts.openwall.com
Subject: Re: AVL tree: storing balances instead of heights
Hi Szabolcs,
2015-12-07 14:03 GMT+01:00 Szabolcs Nagy <nsz@...t70.net>:
> i think the macro definitions for inlining twalk and tfind
> are not justified.
I personally think it is justified in this case. In trivial cases it
may even mean that the compare function is inlined into the body of
twalk()/tfind().
I haven't measured this for twalk() and tfind() explicitly, but my
observation for bsearch() was that a separate compare function and an
invocation of bsearch() is about the same size as inlining the
bsearch() routine.
> you got the rootp==0 case wrong too (posix requires that to
> return 0).
That already happens, right? tdelete() sets it to (void *)1, but
tdelete_recurse() then sets it to NULL immediately.
> and the (T**) cast is invalid in
>
> void *tdelete(const void *restrict key, void **restrict rootp,
> int (*compar)(const void *, const void *)) {
> void *result = (void *)1;
> tdelete_recurse(key, (struct __tnode **)rootp, compar, &result);
> return result;
> }
Could you please elaborate this a bit further?
> posix specifies to return a pointer to a node, not to an element
> pointer, i think that's a bug in posix (otherwise the api would
> be useless).
Yes. On lines 40 and 44 the result pointer is set to the parent
object. As __key is the first member of the structure, I could have
written *n instead of &(*n)->__key, but this implementation does not
strongly enforce it. I could put __key anywhere in the node structure
and it would always return a pointer to a pointer to a key.
--
Ed Schouten <ed@...i.nl>
Nuxi, 's-Hertogenbosch, the Netherlands
KvK-nr.: 62051717
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