Re: [Boost-users] Boost Serialization make_binary & XML/ASCII

From: Javier Estrada (JEstrada_at_[hidden])
Date: 2006-12-19 12:14:26

Terence,

We use Spirit in a similar way to SAX: we read binary data from a serial
port, assemble it into discrete units (messages) and push them through
parser generated by Spirit, which in turn calls a function upon finding
a match.  Some of our messages are multi-part, so we need to keep some
form of state that allows us to assemble the final message.  I would
imagine that there would be a way to break from the parsing.

-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of Terence Wilson
Sent: Saturday, December 09, 2006 2:55 PM
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] Boost Serialization make_binary & XML/ASCII

Robert,

XML is normally parsed using a DOM or SAX parser. DOM reads the whole
file into memory, SAX behaves like a recursive descent parser with
callbacks to the client application. By placing the data block at the
start of the file I should be able to get good performance from SAX or
Spirit. Both would be good choices, however, I want to write some
'reference' code using standard tools since my work will be part of an
SDK.

Regards,

Terence

> -----Original Message-----
> From: boost-users-bounces_at_[hidden] [mailto:boost-users- 
> bounces_at_[hidden]] On Behalf Of Robert Ramey
> Sent: Saturday, December 09, 2006 2:10 PM
> To: boost-users_at_[hidden]
> Subject: Re: [Boost-users] Boost Serialization make_binary & XML/ASCII
> 
> Well, now I'm out of my depth.  Some have commented that the spirit 
> parser is slower than other xml parsers.I don't know.  I would have 
> hoped that since spirit does a lot of the heavy lifting at compile 
> time, it would be pretty fast.  I haven't seen too much data on this
so I really don't know.
> Any parser has to scan every character in the file so its not clear to

> me that a SAX parser or any other can be know a priore to be faster 
> than any other one.
> 
> My reason for using spirit was
> 
> a) it was already part of boost
> b) it was - after some learning curve - a good fit with what I wanted 
> to do.
> c) well documented.
> d) customizable - serialization only uses a portion of the full xml so

> it seemed the most efficient.
> e) all done at compile time so it wouldn't include dead code.
> f) portability to all compilers boost supports.
> g) By exercising a little care in code organization I was able to 
> arrange things so that the module containing the parsing didn't depend

> on the rest of the program.  So the long compile time is not an issue.

> It is in the library and is only recompiled when the grammar changes.
> 
> It is the last feature that suggests that you can easily use this to 
> do your own actions upon parsing the serialization library.
> 
> After some initial pain figuring out how to use it, I have to say I 
> have been extremely pleased with this application of spirit.  I never 
> wanted to do xml serialization as I felt it was a pain in the neck and

> of relatively little utility in my view. I had anticipated a 
> maintainence nightmare so more and more obscure corners of xml syntax 
> were touched.  I'm pleased to say this thing has been fantastic as far

> as I'm concerned.  After the intial one time pain - I haven't had to 
> touch it since 2002 - and this (through spirt 1.6x - still available) 
> is still compatible with Borland 5.51.  And all the hacks required to 
> make this so portable are only compiled into the platforms that need 
> them.
> 
> This has been one of the most significant implementations in making 
> the serialization library possible.  (the other one would probably be
mpl).
> 
> So if this were my problem I would:
> 
> a) Include the xml grammar and parser from the serialization library -

> add my own actions.
> b) finish my code.  Really this I would expect it would be 100 lines.
> c) If its too slow - and if profiling suggests that the spirit parser 
> is the bottleneck - then I would look at tweaking the grammar to speed

> up parsing or replacing the spirit parser with a faster one.  This is 
> my rule:  "First make it work ASAP - then make it faster if necessary"
> 
> But I already am somewhat familiar with spirit so it might not be an 
> interesting option for you.  But then yo might be able to use the 
> current parser unchanged.  Of course this would bring the huge benefit

> that if the xml_archive parser is tweaked for some reason (there are a

> couple of issues with special characters), you would automatically 
> inherit these changes and still be in sync.
> 
> I made the choice to invest the effort to figure out spirit rather 
> than write my 10,000th file parser. Of course that was my decision and

> may not be everyone's preference.
> 
> 
> Good Luck
> 
> Terence Wilson wrote:
> > Robert,
> >
> > The utility I am writing needs to be able to extract a small portion

> > from a large XML file generated by your library. Since it is 
> > performance sensitive I chose to use a SAX parser in order to avoid 
> > reading the whole file. Would it be much work to do this with the 
> > Spirit parser?
> >
> > As always, thanks for the super-fast response.
> >
> > Best regards,
> 
> 
> 
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users

_______________________________________________
Boost-users mailing list
Boost-users_at_[hidden]
http://lists.boost.org/mailman/listinfo.cgi/boost-users