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Posted by Erwin Moller on 09/27/07 12:43
DM wrote:
> "Erwin Moller"
> <Since_humans_read_this_I_am_spammed_too_much@spamyourself.com> wrote in
> message news:46fb87ea$0$244$e4fe514c@news.xs4all.nl...
>> DM wrote:
>>> Hi All,
>>>
>>> I'm writing a program that connects to a data stream containing a number
>>> of
>>> different variable types. Ie 4 & 8 byte integers, ASCII characters and 8
>>> byte floats.
>>>
>>> I use fgetc to capture the data in characters then I reconstruct the
>>> variables from these bytes.
>>>
>>> For integers this is easy, just multiply the bytes by orders of 256 to
>>> get
>>> the right offset values. The thing I can't figure out is how to
>>> reconstruct
>>> a double precision floating point number from its 8 component bytes.
>>>
>>> Is there an easy way to do this in PHP? I couldn't find anything useful
>>> through
>>> Google...
>>>
>>> Any pointers would be greatly appreciated.
>>>
>>> -DM
>>>
>> Hi DM,
>>
>> This data stream, where is it coming from?
>> What program is producing it?
>> Also PHP?
>>
>> Regards,
>> Erwin Moller
>
> Hi Erwin, thanks for the reply.
>
Hi,
> The data stream is coming from a custom Win32 Visual C++ real-time server
> program which pumps out up to 1,000,000 of these multi-type messages per
> day.
>
> I would like to grab and parse this data, then insert it into a postgreSQL
> database under Linux rather than looking for a Windows solution.
Good. (I love Postgres)
>
> I'm looking for a way to get this data into the postgres database so I can
> utillise a whole suite of PHP diagnostic & analysis program I wrote for
> another similar application.
>
> I had a look at the IEEE standard for double precision floats, but it looks
> like I would have to do around 10-15 calculations per message to manually
> restore the value. This would be impractical for the amount of through-put I
> am facing...
Shame.
Are you sure 10 to 15 calculations is too much?
Too slow?
I mean, if you only get 1 milion messages/day.
Would that be too much?
Maybe you can simply throw the 8 bytes straight into Postgres, and write
the bytes->float function in there?
PL/PGsql is bloody fast.
Maybe a trick exists in Postgres to do this more directly.
You could try your luck at their mailinglist: pgsql-general@postgresql.org
You could also simply put the 8 bytes into postgres, and calculate them
to real floats when you need them for diagnostics & analysis app.
That way you are sure your datastream gets in, since you don't need the
conversion right away.
Good luck.
Regards,
Erwin
>
> -DM
>
>
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