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

I was thinking of doing something with looking up the individual byte()
elements using key() on the string values but I couldn't think of an elegant
way to split the input string into two-character chunks. But I'm sure there's
a clever XPath 3 way to do it that I'm just not seeing. Easy to do with a
recursive function or xsl:iterator or analyze-string but I suspect there's a
more succinct way to do it.

So what is the easiest/clearest/most-clever way in XPath 3 to break a string
of arbitrary length into a sequence of strings of a fixed size?

Cheers,

E.
--
Eliot Kimber
http://contrext.com


o;?On 3/12/19, 2:02 PM, "Costello, Roger L. costello@xxxxxxxxx"
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

    Michael Kay wrote:

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

    Wow!

    That is mind-blowing!

    Thank you Michael!

    /Roger


    > 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