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Subject: Re: [boost] [Review] Boost.Endian
From: Beman Dawes (bdawes_at_[hidden])
Date: 2011-09-08 10:49:55

On Thu, Sep 8, 2011 at 7:50 AM, Vitaly Budovski
<vbudovski+news_at_[hidden]> wrote:
> On 8 September 2011 21:31, Beman Dawes <bdawes_at_[hidden]> wrote:
>> Several others have also expressed interest in FP, so I'll give it a
>> try. Issues:
>> * Because FP formats vary, just dealing with endianness doesn't ensure
>> portability.
>> * The endianness of FP and integer values differs on some platforms,
>> so we will have to build up a config file with separate entries for
>> each platform, and that will take time to mature.
>> * Ditto FP sizes.
>> * I'm only willing to provide conversion.hpp FP support. Providing
>> types that mimic FP types is far beyond my knowledge of how to deal
>> with floating point's notorious arithmetic issues.
> I would also like to add my +1 for float support. You could limit
> support to IEEE754 format (32 bit, 64 bit).

The plan is to support the most common platforms. I suspect that's
IEEE754 format (32 bit, 64 bit), but I haven't had a chance to check

> I'm not sure how widespread differing endianness between ints and
> floats is across the various platforms.

The Wikipedia article says it's uncommon, IIRC, but we need some real
data on that.

> Would it be acceptable to provide a #define that will cause ints and
> floats to be treated as having reversed endianness relative to each
> other (i.e. if native int is little-endian, float would be
> big-endian)?

Yes, and that might be a good way to deal with less common platforms
until our config file coverage matures.



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