[fpc-pascal] Writing floating points to steams

Torsten Bonde Christiansen tc at epidata.info
Wed Jan 13 10:45:51 CET 2016


On 2016-01-13 10:40, Mark Morgan Lloyd wrote:
> Torsten Bonde Christiansen wrote:
>> On 2016-01-13 10:06, Mark Morgan Lloyd wrote:
>>> Serguei TARASSOV wrote:
>>>> On 13/01/2016 08:47, fpc-pascal-request at lists.freepascal.org wrote:
>>>>> On 2016-01-12 10:45, Torsten Bonde Christiansen wrote:
>>>>>> Since TStream doesn't have any native WriteFloat/Double and the 
>>>>>> likes,
>>>>>> some conversion is needed - but what is a good strategy for this?
>>>> Depends on size constraints.
>>>> In the simple case you should convert float to locale-independent 
>>>> string value (no spaces, no commas separators) then write it.
>>>> If the size does matter, you may convert float to corresponding 
>>>> byte array then write it.
>>>
>>> Can I ask a naive question here please: does a binary stream store 
>>> endianness anywhere? In other words, is there any indication that 
>>> something running on ARM is about to get into trouble by reading 
>>> something written by (big-endian) MIPS?
>
>> Not that I'm aware of - i would think of it as a stream of bytes. 
>> Endianess is defined by the CPU not by the file.
>
> Thanks, I assumed that was the case but thought it worth checking.
>
> I suppose that one could stream variants, i.e. the enumeration saying 
> what one was followed by a value.
>
>>> Should writing binary floating point to a stream note that it's IEEE 
>>> format, just in case anybody ever tries to process it on a platform 
>>> that supports alternatives?
>>>
>> It would be great if storing floating point could be in IEEE, to have 
>> a standard as reference.
>
> I'm not at all sure about this, but I think I've seen something that 
> suggested that byte ordering in external representations was covered 
> by the standard.

I'm not even sure how (or even if) TStream decendants handles endianness 
for integers.... I'm guessing they are not.

Regards,
Torsten.



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