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RE: [xsl] String conversion problem when string is large


Subject: RE: [xsl] String conversion problem when string is large
From: "Bulgrien, Kevin" <Kevin.Bulgrien@xxxxxxxxxxxx>
Date: Wed, 21 Mar 2012 17:18:38 -0500

And this variant seems to balance speed and memory usage, but still kills all
the engines I have except the Saxonica engine.

Execution time: 1.039s (1039ms)
Memory used: 30306880

<xsl:call-template name="HexToDec">
  <xsl:with-param name="HexData" select="." />
  <xsl:with-param name="Hex" select="'0123456789ABCDEF'" />
</xsl:call-template>

<xsl:template name="HexToDec">
  <xsl:param name="HexData" />
  <xsl:param name="Hex" />
  <xsl:if test="string-length($HexData) &gt; 0">
    <xsl:text>,</xsl:text>
    <xsl:value-of
      select="string-length(
                substring-before(
                  $Hex, substring($HexData, 3, 1))) * 16 +
              string-length(
                  substring-before(
                  $Hex, substring($HexData, 4, 1)))" />
    <xsl:call-template name="HexToDec">
      <xsl:with-param name="HexData"
        select="substring-after($HexData, ',')" />
      <xsl:with-param name="Hex" select="$Hex" />
    </xsl:call-template>
  </xsl:if>
</xsl:template>

To let other XSLT engines that do not optimize recursion, a divide and conquer
approach was simple enough to concoct.  The chunk size was a bit arbitrary,
but is about half of what it took to break another engine at its default stack
depth.  xsltproc took about 2.8 seconds.  sablotron took 5.8 seconds.  I won't
bother to show times for the Windows engines as the platform difference makes
them hard to compare fairly.

Execution time: 832ms
Memory used: 26545336

<xsl:call-template name="HexToDecChunker">
  <xsl:with-param name="HexData" select="." />
  <xsl:with-param name="Hex" select="'0123456789ABCDEF'" />
</xsl:call-template>

<xsl:template name="HexToDecChunker">
  <xsl:param  name="HexData" />
  <xsl:param name="Hex" />
  <xsl:variable name="ChunkLen" select="5120" />
  <xsl:variable name="InputLen" select="string-length($HexData)" />
  <xsl:choose>
    <xsl:when test="$InputLen &gt; $ChunkLen">
      <xsl:call-template name="HexToDec">
        <xsl:with-param name="HexData"
          select="substring($HexData, 1, $ChunkLen)" />
        <xsl:with-param name="Hex" select="$Hex" />
      </xsl:call-template>
      <xsl:call-template name="HexToDecChunker">
        <xsl:with-param name="HexData"
          select="substring($HexData, $ChunkLen + 1)" />
        <xsl:with-param name="Hex" select="$Hex" />
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise>
      <xsl:call-template name="HexToDec">
        <xsl:with-param name="HexData" select="$HexData" />
        <xsl:with-param name="Hex" select="$Hex" />
      </xsl:call-template>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>

What an adventure.  There are probably a lot more ways to tackle this issue.

Kevin Bulgrien

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