Re: [Boost-users] Convert big endian to little endian (floating point values)

Subject: Re: [Boost-users] Convert big endian to little endian (floating point values)
From: Martin Vymazal (martin.vymazal_at_[hidden])
Date: 2015-12-08 17:18:39

On 2015-12-08 22:48, Maarten de Vries wrote:
> On 8 December 2015 at 22:14, Martin Vymazal <martin.vymazal_at_[hidden]>
> wrote:
> 
>> Hi,
>> 
>> ok, here's the whole story. We have a code that computes some data,
>> compresses them through zlib and saves as binary. We also use our
>> own utility to postprocess the compressed file and convert it to
>> human-readable format.
>> 
>> What happened recently is that the code ran on a big-endian machine
>> and since zlib preserves the endian-ess of the data, it generated a
>> binary with big-endian doubles. We would like to have the
>> possibility of bringing that file on a little-endian machine (say
>> user's laptop) and postprocess there, instead of doing everything on
>> the big-endian machine. Do you have an alternative suggestion how to
>> approach this problem? Let's assume that writing the output data in
>> any other format than the current one is not possible.
>> 
>> I am also still interested in knowing whether boost (1.59) supports
>> conversions between endian representations of floating-point values.
> 
> If you absolutely must, the easiest way to do this is to read the data
> as if it's an unsigned integer type (of the correct size), convert
> endianness, then reinterpret_cast (or something similarly horrible) to
> the floating point type.
> 
> Of course, not relying on the platform specific bit representation of
> primitive data types when serializing data is a much better idea.
> 
> -- Maarten

What would be a possible approach to save the data without 'relying on 
the platform specific bit representation of primitive data types' as you 
put it? I can not save the data as plain ascii text, because the files 
would simply be huge (the're already big as they are). Is there some 
more intelligent solution? I'm not a software engineer, so I'd be happy 
to hear what is the common practice here.

I will also try one last time: does boost support conversion of floating 
point types or not? The website says so, but it doesn't work for me. I 
am not asking because I plan to use this functionality, I'm simply 
curious since I already started playing with it.

Martin

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