Re: [xml] Dump document to a buffer without xml version

[Iñigo Martínez <inigomartinez gmail com>]

Yeah, it's ok, and the answer is totally valid. I only wondered if my
approach had any known drawback.

Thank you very much :)

2014-08-22 9:16 GMT+02:00 Daniel Veillard <veillard redhat com>:
> On Fri, Aug 22, 2014 at 08:34:37AM +0200, Iñigo Martínez wrote:
> > It looks like a longer way. I mean, with the new saving API there is
> > one more variable and one more function call, plus the creation of the
> > full document, instead of using only just the nodes. Some code
> > snippets.
> >
> > Using the saving API:
> >
> >       xmlDocPtr doc;
> >       xmlNodePtr node;
> >       xmlBufferPtr buffer;
> >       xmlSaveCtxtPtr ctx;
> >
> >       doc = xmlNewDoc (NULL);
> >       node = xmlNewNode (NULL, BAD_CAST "Command");
> >       xmlDocSetRootElement (doc, node);
> >
> >       xmlNewProp(node, BAD_CAST "Timestamp", BAD_CAST "0");
> >       xmlNewProp(node, BAD_CAST "ReceptionTimestamp", BAD_CAST "0");
> >       xmlNewProp(node, BAD_CAST "Sender", BAD_CAST "P1");
> >       xmlNewProp(node, BAD_CAST "Receiver", BAD_CAST "P2");
> >
> >       xmlNewChild(node, NULL, BAD_CAST "GetData", NULL);
> >
> >       buffer = xmlBufferCreate ();
> >       ctx = xmlSaveToBuffer (buffer, NULL, XML_SAVE_NO_DECL);
> >       if (xmlSaveDoc (ctx, doc) == -1) {
> >           fprintf (stderr, "Error saving buffer\n");
> >           return;
> >       }
> >       xmlBufferFree (buffer);
> >
> > Using xmlNodeDump:
> >
> >       xmlNodePtr node;
> >       xmlBufferPtr buffer;
> >
> >       node = xmlNewNode (NULL, BAD_CAST "Command");
> >
> >       xmlNewProp (node, BAD_CAST "Timestamp", BAD_CAST "0");
> >       xmlNewProp (node, BAD_CAST "ReceptionTimestamp", BAD_CAST "0");
> >       xmlNewProp (node, BAD_CAST "Sender", BAD_CAST "P1");
> >       xmlNewProp (node, BAD_CAST "Receiver", BAD_CAST "P2");
> >
> >       xmlNewChild (node, NULL, BAD_CAST "GetData", NULL);
> >
> >       buffer = xmlBufferCreate ();
> >       if (xmlNodeDump(buffer, NULL, cmd, 0, 0) == -1) {
> >           fprintf (stderr, "Error saving buffer\n");
> >           return;
> >       }
> >       xmlBufferFree (buffer);
> >
> > Is there any benefit on using the new saving API ?
>
>   Depends on a variety of things I don't know like if your tree
> is always that simple, how much/often do you save, if you can reuse the
> ctx, if you can hook the ctx to your I/O, etc ...
>   If the goal is purely to save to ram and discard it, yes it looks
> simpler
>   You asked a question "how to save a doc without the XMLDecl ?",
> I answered, that's all !
>
> Daniel
>
> > 2014-08-22 6:34 GMT+02:00 Daniel Veillard <veillard redhat com>:
> > > On Wed, Aug 20, 2014 at 07:04:06PM +0200, Iñigo Martínez wrote:
> > > > Hi:
> > > >
> > > > I'm working with a protocol based on XML, something like:
> > > >
> > > > <Command Timestamp="0" ReceptionTimeStamp="0" Sender="P1"
> > > > Receiver="P2"><GetData/></Command>
> > > >
> > > > I can successfully parse these messages using xmlReadMemory and
> > > > navigating through the tree. When trying to create my own messages I
> > > > can create them successfully this way:
> > > >
> > > > doc = xmlNewDoc(NULL);
> > > > node = xmlNewNode(NULL, BAD_CAST "Command");
> > > > xmlDocSetRootElement(doc, node);
> > > >
> > > > xmlNewProp(node, BAD_CAST "Timestamp", BAD_CAST "0");
> > > > xmlNewProp(node, BAD_CAST "ReceptionTimestamp", BAD_CAST "0");
> > > > xmlNewProp(node, BAD_CAST "Sender", BAD_CAST "P1");
> > > > xmlNewProp(node, BAD_CAST "Receiver", BAD_CAST "P2");
> > > >
> > > > xmlNewChild(node, NULL, BAD_CAST "GetData", NULL);
> > > >
> > > > The problem comes when trying to get the correspondant string as I get
> > > > the xml version in the output:
> > > >
> > > > <?xml version="1.0"?><Command Timestamp="0" ReceptionTimeStamp="0"
> > > > Sender="P1" Receiver="P2"><GetData/></Command>
> > > >
> > > > I have seen some tricks using a xmlTextWriter, but in my case I need
> > > > an string not a file.
> > > >
> > > > Is there any way to avoid it ?
> > >
> > >   Best way is to use the 'new' saving APIs
> > >
> > > http://xmlsoft.org/html/libxml-xmlsave.html#xmlSaveToBuffer
> > > with XML_SAVE_NO_DECL in the option
> > >
> > > and use
> > > http://xmlsoft.org/html/libxml-xmlsave.html#xmlSaveDoc
> > >
> > > if you are piling up such messages on an IO just use anothe xmlSaveTo...
> > > function and Flush to output instead of writing in memory and doing
> > > the I/O separately
> > >
> > > Daniel
> > >
> > > --
> > > Daniel Veillard      | Open Source and Standards, Red Hat
> > > veillard redhat com  | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
> > > http://veillard.com/ | virtualization library  http://libvirt.org/
>
> --
> Daniel Veillard      | Open Source and Standards, Red Hat
> veillard redhat com  | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
> http://veillard.com/ | virtualization library  http://libvirt.org/