Boost logo

Boost Users :

Subject: Re: [Boost-users] Convert big endian to little endian (floating point values)
From: Martin Vymazal (martin.vymazal_at_[hidden])
Date: 2015-12-08 16:14:21


On 2015-12-08 19:40, Aaron_Wright_at_[hidden] wrote:
>> From: Martin Vymazal <martin.vymazal_at_[hidden]>
>> Hello,
>>
>> I am trying to convert a floating point value from big endian to
> little
>> endian, but the code below does not compile:
>>
>> double x = 10.0;
>>
>> const double x_big_endian = boost::endian::native_to_big(x);
>> boost::endian::native_to_big_inplace(x);
>
> Be very careful how you swap floats. They aren't like integer data
> types where the swapped representation can fit nicely into the same
> type. Not all swapped floats are valid floats, and you'll find that
> the bits will be messaged into a valid float, thus changing your value
> without telling you. You can only swap a float into an integer. You
> can't swap a float into a float.

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.

Martin


Boost-users list run by williamkempf at hotmail.com, kalb at libertysoft.com, bjorn.karlsson at readsoft.com, gregod at cs.rpi.edu, wekempf at cox.net