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

2010-02-14 04:57:23
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


--
Gerrit Imsieke
Geschäftsführer / Managing Director
le-tex publishing services GmbH
Weissenfelser Str. 84, 04229 Leipzig, Germany
Phone +49 341 355356 110, Fax +49 341 355356 510
gerrit(_dot_)imsieke(_at_)le-tex(_dot_)de, http://www.le-tex.de

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Registernummer / Registration Number: HRB 24930

Geschäftsführer: Gerrit Imsieke, Svea Jelonek,
Thomas Schmidt, Dr. Reinhard Vöckler

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