[xsl] Re: Testing the existence of a binary file (was: How to specify 'raw' encoding in xslt:unparsed-text-available?)

["Imsieke, Gerrit, le-tex" <gerrit.imsieke@xxxxxxxxx>]

Since nobody answered, I tried to come up with a solution on my own.

It seems that in Java there is no such thing as a 'raw' encoding, since 
everything will be represented as 16-bit Unicode characters internally. 
http://java.sun.com/javase/7/docs/api/java/nio/charset/CharsetDecoder.html
If I supplied my own CharsetDecoder, maybe I could just ignore malformed 
input and unmappable characters and report success for any input of 
non-zero length. But I was looking for a solution that works with Saxon 
out of the box, not requiring users to install Java extension functions.

Looking at what I was trying to achieve, that is: testing the sheer 
existence of a binary file, rather than reading its raw contents, I came 
up with the following solution:

<sch:assert
  test="saxon:try(
          format-dateTime(
            saxon:last-modified(
              resolve-uri(
                @src,
                $base-uri
              )
            ),
            '[Y]'
          ),
          false()
        )"
  id="ImageMissing">
    Image <sch:value-of select="@src"/> must be present at its @src 
location.
</sch:assert>

This relies on the operating system reporting a last change date for the 
file in question, and of course on Saxon's built-in extension functions 
which will be an issue for Saxon HE users.

Gerrit


On 05.02.2010 10:21, Imsieke, Gerrit, le-tex wrote:
> Dear List Members,
>
> In Schematron using the xslt2 binding, I want to check whether image
> files (whose relative path is given in a @src attribute) are present.
>
> So in the generated XSLT file, I have code like the following.
>
> <xsl:when test="unparsed-text-available(resolve-uri(@src, $base-uri))"/>
>
> This works fine if @src refers to text files in US-ASCII or UTF-8
> encodings, but not for PNGs oder JPEGs.
>
> So I was looking for an encoding name that I can use as the second
> argument to unparsed-text-available. But I couldn't find an encoding
> such as RAW or BINARY that Java accepts (I'm using saxon 9.2.0.3 on Java
> 1.6.0_17).
>
> This issue must have been raised before, but unfortunately I didn't find
> previous threads on this matter.
>
> Any hints appreciated.
>
> Gerrit

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Gerrit Imsieke
Geschdftsf|hrer / Managing Director
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