audacity/lib-src/libraptor/docs/raptor-tutorial-querying-functionality.xml

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<chapter id="tutorial-querying-functionality">
<title>Listing built-in functionality</title>

<para>
Raptor can be configured and compiled with support for different
parsers and serializers.  Lists of the functionality built into the
library can be interrogated by means of
<emphasis>enumerate</emphasis> functions.  These take as input an
<literal>int</literal> counter and return descriptions of the feature
at that offset in the list.  The descriptions are returned stored in
the variables pointed to by the reference arguments of the
<literal>**</literal><emphasis>var</emphasis> form.
The return value of the function is non-zero when the counter has
gone too far.
</para>

<variablelist>
<title>Listing Functionality with Enumeration</title>
<varlistentry><term>List the parse syntaxes (parser names)</term>
<listitem><programlisting>
int
raptor_parsers_enumerate(const unsigned int counter,
                         const char **name, const char **label);
</programlisting></listitem>
</varlistentry>
<varlistentry><term>List the parse syntaxes
(same as above but with more information)</term>
<listitem><programlisting>
int
raptor_syntaxes_enumerate(const unsigned int counter,
                          const char **name,
                          const char **label, 
                          const char **mime_type,
                          const unsigned char **uri_string);
</programlisting></listitem>
</varlistentry>
<varlistentry><term>List the serializer syntaxes (serializer names)</term>
<listitem><programlisting>
int
raptor_serializers_enumerate(const unsigned int counter,
                             const char **name,
                             const char **label,
                             const char **mime_type,
                             const unsigned char **uri_string);
</programlisting></listitem>
</varlistentry>
<varlistentry><term>List the Parser features</term>
<listitem><programlisting>
int
raptor_features_enumerate(const raptor_feature feature,
                          const char **name, raptor_uri **uri,
                          const char **label);
</programlisting></listitem>
</varlistentry>
<varlistentry><term>List the Serializer features</term>
<listitem><programlisting>
int
raptor_serializer_features_enumerate(const raptor_feature feature,
                                     const char **name,
                                     raptor_uri **uri,
                                     const char **label);
</programlisting></listitem>
</varlistentry>
<varlistentry><term>List the XML Writer features</term>
<listitem><programlisting>
int
raptor_xml_writer_features_enumerate(const raptor_feature feature,
                                     const char **name,
                                     raptor_uri **uri,
                                     const char **label);
</programlisting></listitem>
</varlistentry>
</variablelist>

<para>These functions can be called directly after
<link linkend="raptor-init"><function>raptor_init()</function></link>
has been called so can be used to find name parameters for creating
parser and serializer instances.  This is one way to find a parser
(name) by it's MIME Type, the other is to use the mime_type parameter
of the
<link linkend="raptor-new-parser-for-content"><function>raptor_new_parser_for_content()</function></link>.</para>

<example id="raptor-example-list-all-parser-features">
<title>List all features of parsers with an enumerate function</title>
<programlisting>
  int i;
  for(i=0; i &lt; RAPTOR_FEATURE_LAST; i++) {
    const char *name;
    raptor_uri *uri;
    const char *label;
    if(raptor_features_enumerate((raptor_feature)i, &amp;name, &amp;uri, &amp;label))
      continue;
    /* do something with name, uri and label */
  }
</programlisting>
<para>There are more examples of this usage in the source for the
<literal>rapper</literal> utility in <filename>util/rapper.c</filename>.
</para>
</example>

</chapter>

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