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
On 3/12/19, 2:02 PM, "Costello, Roger L. costello(_at_)mitre(_dot_)org"
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> 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(_at_)mitre(_dot_)org
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> 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
>
>
>
>
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