[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

Re: Find the number of elements that are prior to the

Subject: Re: Find the number of elements that are prior to the series of elements that match a string?
From: "Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 12 Mar 2019 18:01:21 -0000
Re:  Find the number of elements that are prior to the
My instinct is to use index-of() to get the positions of the elements that
match the first required byte, and then for each of these positions, form the
string of N bytes starting at this position and do a string comparison to test
whether there is a match at this position.

let $candidates := index-of(/Bytes/Byte, substring($req, 1, 2))
return $candidates[string-join(subsequence(/Bytes/Byte, ., $len), '') eq
$req][1] - 1

Michael Kay
Saxoniica



> On 12 Mar 2019, at 17:35, Costello, Roger L. costello@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hi Folks,
>
> I have an XML document containing a long list of Byte elements, e.g.,
>
> <Bytes>
>    <Byte hexAddress="0">4D</Byte>
>    <Byte hexAddress="1">5A</Byte>
>    <Byte hexAddress="2">90</Byte>
>    <Byte hexAddress="3">00</Byte>
>    <Byte hexAddress="4">03</Byte>
>    <Byte hexAddress="5">00</Byte>
>    <Byte hexAddress="6">00</Byte>
>    <Byte hexAddress="7">00</Byte>
>    <Byte hexAddress="8">04</Byte>
>    <Byte hexAddress="9">00</Byte>
>    <Byte hexAddress="A">00</Byte>
>    <Byte hexAddress="B">00</Byte>
>    <Byte hexAddress="C">FF</Byte>
>    <Byte hexAddress="D">FF</Byte>
>    ...
> </Bytes>
>
> I have a string of hex values, e.g.,
>
> 04000000FF
>
> You can see that the string is contained within this series of Byte
elements:
>
>    <Byte hexAddress="8">04</Byte>
>    <Byte hexAddress="9">00</Byte>
>    <Byte hexAddress="A">00</Byte>
>    <Byte hexAddress="B">00</Byte>
>    <Byte hexAddress="C">FF</Byte>
>
> I want to find the number of <Byte> elements that occur prior to the series
of Byte elements.
>
> I figured one approach is to convert all the Byte text node values into a
string and then perform string manipulations:
>
> string-length(substring-before(string-join(/Bytes/Byte/text(), ''),
'04000000FF')) idiv 2
>
> Note: I divided by two because each Byte has 2 digits.
>
> That seems to work, but I suspect it is horribly inefficient because it
creates a string containing all the Byte text node values and there may be
tens or hundreds of thousands of Byte elements.
>
> What is an efficient way to solve this problem?
>
> /Roger

Current Thread

PURCHASE STYLUS STUDIO ONLINE TODAY!

Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Buy Stylus Studio Now

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Don't miss another message! Subscribe to this list today.
Email
First Name
Last Name
Company
Subscribe in XML format
RSS 2.0
Atom 0.3
Site Map | Privacy Policy | Terms of Use | Trademarks
Free Stylus Studio XML Training:
W3C Member
Stylus Studio® and DataDirect XQuery ™are products from DataDirect Technologies, is a registered trademark of Progress Software Corporation, in the U.S. and other countries. © 2004-2013 All Rights Reserved.