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From: Ed Schouten <ed@nuxi.nl>
To: Ed Schouten <ed@nuxi.nl>, musl@lists.openwall.com
Subject: Re: AVL tree: storing balances instead of heights
Date: Mon, 7 Dec 2015 14:19:58 +0100	[thread overview]
Message-ID: <CABh_MKnkw_Yp9ifwybXBOMb0FuPvP05T183utZ1kW6Ohqq3gvQ@mail.gmail.com> (raw)
In-Reply-To: <20151207130344.GZ23362@port70.net>

Hi Szabolcs,

2015-12-07 14:03 GMT+01:00 Szabolcs Nagy <nsz@port70.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@nuxi.nl>
Nuxi, 's-Hertogenbosch, the Netherlands
KvK-nr.: 62051717


  reply	other threads:[~2015-12-07 13:19 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CABh_MKm1Ow5_dc4ENJM-fAqWc+uPPZgftRdSDxPJiPXZAfZ+FQ@mail.gmail.com>
2015-12-07 13:03 ` Szabolcs Nagy
2015-12-07 13:19   ` Ed Schouten [this message]
2015-12-07 13:22     ` Ed Schouten
2015-12-07 14:46     ` Szabolcs Nagy
2015-12-10  9:21       ` Ed Schouten
2015-12-10 12:14         ` Szabolcs Nagy
2015-12-10 13:12           ` Ed Schouten
2015-12-10 13:43             ` Szabolcs Nagy
2015-12-20 21:43               ` Szabolcs Nagy
2015-12-21  1:28                 ` Szabolcs Nagy

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