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Re: hashlittle(), hashbig(), hashword() and endianness

From: Alex Vinokur <alexvn(at)users(dot)sourceforge(dot)net>
To: pgsql-patches(at)postgresql(dot)org
Subject: Re: hashlittle(), hashbig(), hashword() and endianness
Date: 2007-11-15 10:56:21
Message-ID: 4a96bb23-fb44-4285-9b46-093efc483be1@w28g2000hsf.googlegroups.com (view raw or flat)
Thread:
Lists: pgsql-patches
On Nov 15, 10:40 am, Alex Vinokur <ale(dot)(dot)(dot)(at)users(dot)sourceforge(dot)net>
wrote:
[snip]
> I have some question concerning Bob Jenkins' functions
> hashword(uint32_t*, size_t), hashlittle(uint8_t*, size_t) and
> hashbig(uint8_t*, size_t) in lookup3.c.
>
> Let k1 by a key: uint8_t* k1; strlen(k1)%sizeof(uint32_t) == 0.
>
> 1. hashlittle(k1) produces the same value on Little-Endian and Big-
> Endian machines.
>    Let hashlittle(k1) be == L1.
>
> 2. hashbig(k1) produces the same value on Little-Endian and Big-Endian
> machines.
>    Let hashbig(k1) be == B1.
>
>   L1 != B1
>
> 3. hashword((uint32_t*)k1) produces
>     * L1 on LittleEndian machine and
>     * B1 on BigEndian machine.
>
===================================
> ---------------------
> The question is: is it possible to change hashword() to get
>     * L1 on Little-Endian machine and
>     * B1 on Big-Endian machine
>    ?

Sorry, it should be as follows:

Is it possible to create two new hash functions on basis of
hashword():
   i)  hashword_little () that produces L1 on Little-Endian and Big-
Endian machines;
   ii) hashword_big ()    that produces B1 on Little-Endian and Big-
Endian machines
   ?

====================================

Thanks.

Alex Vinokur
     email: alex DOT vinokur AT gmail DOT com
     http://mathforum.org/library/view/10978.html
     http://sourceforge.net/users/alexvn


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Next:From: Heikki LinnakangasDate: 2007-11-15 11:23:44
Subject: Re: hashlittle(), hashbig(), hashword() and endianness
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