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[Vtd-xml-users] Fw: push and pop
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From: Jimmy Z. <cra...@co...> - 2006-08-23 17:59:11
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RE: push and pop
----- Original Message -----=20
From: Jimmy Zhang=20
To: Walinsky, Frank=20
Cc: vtd...@us...=20
Sent: Wednesday, August 23, 2006 10:51 AM
Subject: Re: push and pop
It is great that you brought up this interesting discussion, we =
certainly want to know
how you use VTD-XML and how it can be made better...
When you say "Xpath with the same AutoPilot to somewhere else and print =
it's content." do you mean
you use AutoPilot to compile a different XPath expression ??
If that is the case, if you have already lost the Xpath expression =
previously compiled, and
even you got back to the original position using pop(), the old xpath =
expression is completely
gone...
Did I misunderstand anything?
----- Original Message -----=20
From: Walinsky, Frank=20
To: Jimmy Zhang=20
Sent: Wednesday, August 23, 2006 5:36 AM
Subject: RE: push and pop
It would be easier to have you give me a code snippet using your =
product, since that's what I'm trying to use.=20
If you could provide a code snippet that shows the following =
(highlighted in red and a direct copy from your website):=20
Cursor-based hierarchical view: In this view, one navigates the cursor =
across the hierarchy. However, one should notice that this hierarchy is =
for elements only; in other words, in our processing, we only consider =
elements as part of the hierarchy, and treats text node, CDATA and =
attributes as belongings of an element. Also there is one and only one =
global cursor available. Duplicate of this cursor is disallowed. To =
record the position of a cursor, one can either save the VTD index value =
or push the cursor value into a global stack, and later pop it back. The =
following code snippet navigates a very simple XML document and prints =
out value of interest. =20
I need to see a working code snippet that does both ways that are =
described above in red highlight.=20
Here is a simple senerio using 1 AutoPilot that would be of most use:=20
:=20
Setup, with an xpath, an iteration that will have more than one =
result.=20
Do the "evalXPath" iteration.=20
Save the current location as described above in red.=20
Xpath with the same AutoPilot to somewhere else and print it's =
content.=20
Reset back to the location saved previously.=20
Go back to the "evalXPath" iteration step above and get the next =
iteration=20
Again - thank you for your patience and all the help you have been =
giving me.=20
Frank=20
-----Original Message-----=20
From: Jimmy Zhang [mailto:cra...@co...]=20
Sent: Tuesday, August 22, 2006 5:34 PM=20
To: Walinsky, Frank=20
Cc: vtd...@li...=20
Subject: Re: push and pop=20
Yes, this is indeed how Autopilot is implemented, one xpath expression =
per autoPilot object is the intended user, and nodeIteration can be =
thought of as an xpath expression...
I think it may be easier if there is code on how DOM would work, and I =
can offer you suggestions/workarounds in VTD-XML code...
If you try DOM's node iterator, it is quite similar to VTD-XML's =
autoPilot=20
----- Original Message -----=20
From: "Walinsky, Frank" <fwa...@ex...>=20
To: "Jimmy Zhang" <jz...@xi...>=20
Sent: Tuesday, August 22, 2006 1:58 PM=20
Subject: RE: push and pop=20
Using the xml doc from below:=20
I'm iterating over the "a" element and then the "b" element.=20
For each "b" element, the user wants to use one of its children(one of =
the "c" elements). I have the "c" element name in a variable ( in =
actual=20
practice the "c" element names are unique) and I do an xpath using the =
AutoPilot and this variable to get the correct child. Then I do=20
something with the "c" element content. Now I want to go back to the =
top=20
of the iteration and get the next "b" element. This is where the=20
AutoPilot thinks there are no more "b" elements when in fact there is=20
one more "b" element in the first "a" element.=20
-----Original Message-----=20
From: Jimmy Zhang [mailto:jz...@xi...]=20
Sent: Tuesday, August 22, 2006 3:57 PM=20
To: Walinsky, Frank=20
Cc: vtd...@li...=20
Subject: Re: push and pop=20
It may be a case-specific hack for you...=20
AutoPilot internally *remembers* a few variables (string name, depth=20
etc), to capture/restore, there may be additional data structure (e.g. =
a=20
stack) needed to store those variables...=20
but my questions is how you really do anything different from using =
DOM=20
you will still have to instantiate nodeIterators for each levels =
right?=20
also vtd...@li... seems to be working now=20
----- Original Message -----=20
From: "Walinsky, Frank" <fwa...@ex...>=20
To: "Jimmy Zhang" <jz...@xi...>=20
Sent: Tuesday, August 22, 2006 11:46 AM=20
Subject: RE: push and pop=20
What might be needed is a capture/restore of the AutoPilot along with=20
the currentoffset=20
-----Original Message-----=20
From: Jimmy Zhang [mailto:jz...@xi...]=20
Sent: Tuesday, August 22, 2006 11:19 AM=20
To: Walinsky, Frank=20
Subject: Re: push and pop=20
I need to think about this...=20
----- Original Message -----=20
From: "Walinsky, Frank" <fwa...@ex...>=20
To: <jz...@xi...>=20
Sent: Tuesday, August 22, 2006 4:13 AM=20
Subject: RE: push and pop=20
I will try another approach using just 1 AutoPilot by trying to rework =
my current code.=20
-----Original Message-----=20
From: jz...@xi... [mailto:jz...@xi...]=20
Sent: Monday, August 21, 2006 10:18 PM=20
To: Walinsky, Frank=20
Subject: Re: push and pop=20
Can you kinda explain why allocating multiple AutoPilots is=20
show-stopping??=20
because autoPilot allocation is fairly light weight? Maybe VTD-XML can =
custom build something for your case...=20
Walinsky, Frank writes:=20
> Jimmy,=20
> I did try 3 different AutoPilots after I sent this and that does =
work=20
> just as you thought it would.=20
> It also works without doing any push or pop.=20
> My situation has a user generated state which could have an =
unlimited=20
> amount of nesting.=20
> This state is processed by some generic code, which is not custom=20
> generated but used by all user generated states.=20
> This works fine with the DOM product I'm using.=20
> I was looking to reduce the memory footprint and do a proof of =
concept=20
> with your app for management.=20
> If I can't use the one AutoPilot with push and pop, I'm dead in the=20
> water with your app right out of the gate.=20
> If you could take a closer look, when you have time, and see if it =
is=20
a=20
> bug or just not possible, I would greatly appreciate it.=20
> Thx for all your help,=20
> Frank=20
>=20
>=20
> ________________________________=20
>=20
> From: Jimmy Zhang [mailto:jz...@xi...]=20
> Sent: Monday, August 21, 2006 4:13 PM=20
> To: Walinsky, Frank; vtd...@li...=20
> Subject: Re: push and pop=20
>=20
>=20
> Frank, upon a quick look, I feel you might want to instantiate three =
> autoPilot=20
> objects, the first one you set the element name "a," the second set=20
the=20
> element=20
> name "b," and the last one set the element "c." Could=20
> Cheers,=20
> Jimmy Zhang=20
>=20
> ----- Original Message -----=20
> From: Walinsky, Frank <mailto:fwa...@ex...>=20
> To: in...@xi...=20
> Sent: Monday, August 21, 2006 12:40 PM=20
> Subject: push and pop=20
>=20
> Jim,=20
> I apologize again for using this address but it has become=20
> completely frustrrating trying to send to the list.=20
> I just tried a handfull of times and had my message returned. I=20
> did get one through this morning so I know it does work=20
> but when is anybodies guess.=20
>=20
> Could you please look at this when you have time?=20
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> Is it possible and if so, is there any sample code somewhere=20
> that does the following:=20
> (I ask because I haven't found a way or I'm probably using the=20
> api incorrectly)=20
>=20
> I'm trying to use the same AutoPilot object in a 3 level nesting=20
> using a VTDNav "push"=20
> before entering the next lower level and the VTDNav "pop" before=20
> returning to the previous higher level.=20
> Neither the "iterate" or an "evalXPath" advance to the next=20
> element after the pop.=20
>=20
> Here's a sample xml I'm using:=20
> <?xml version=3D\"1.0\" encoding=3D\"UTF-8\"?>=20
> <root>=20
> <a>=20
> <b>=20
> <c>this is abc_11</c>=20
> <c>this is abc_12</c>=20
> <c>this is abc_13</c>=20
> <c>this is abc_14</c>=20
> </b>=20
> <b>=20
> <c>this is abc_21</c>=20
> <c>this is abc_22</c>=20
> <c>this is abc_23</c>=20
> <c>this is abc_24</c>=20
> </b>=20
> </a>=20
> <a>=20
> <b>=20
> <c>this is second abc_31</c>=20
> </b>=20
> </a>=20
> </root>=20
>=20
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> Here's a snippet of my code.=20
>=20
> vn.toElement(VTDNav.ROOT);=20
>=20
> ap.selectElement("a");=20
> while (ap.iterate()) {=20
> System.out.println("--- before push() of \"a\"---");=20
> vn.dumpContext();=20
> vn.push();=20
> System.out.println("a =3D " + vn.getCurrentIndex());=20
>=20
> ap.selectElement("b");=20
> while (ap.iterate()) {=20
> System.out.println("--- before push() of \"b\" ---");=20
> vn.dumpContext();=20
> vn.push();=20
> System.out.println("b =3D " + vn.getCurrentIndex());=20
>=20
> ap.selectElement("c");=20
> while (ap.iterate()) {=20
> System.out.println("c =3D " + vn.getCurrentIndex());=20
> }=20
>=20
> vn.pop();=20
> System.out.println("--- after pop() of \"b\" ---");=20
> vn.dumpContext();=20
> }=20
>=20
> vn.pop();=20
> System.out.println("--- after pop() of \"a\" ---");=20
> vn.dumpContext();=20
> }=20
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