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          <h1 align="center"><a href="../index.html">Boost.Python</a></h1>

          <h2 align="center">Header
          &lt;boost/python/return_opaque_pointer.hpp&gt;</h2>
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    <h2>Contents</h2>

    <dl class="page-index">
      <dt><a href="#classes">Classes</a></dt>

      <dd>
        <dl class="page-index">
          <dt><a href="#return_opaque_pointer-spec">Class
          <code>return_opaque_pointer</code></a></dt>

          <dd>
            <dl class="page-index">
              <dt><a href="#return_opaque_pointer-spec-synopsis">Class
              <code>return_opaque_pointer</code> synopsis</a></dt>

              <dt><a href="#return_opaque_pointer-spec-metafunctions">Class
              <code>return_opaque_pointer</code> metafunctions</a></dt>
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      <dt><a href="#examples">Example</a></dt>

      <dt><a href="#see-also">See Also</a></dt>
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        <h2><a name="classes"></a>Classes</h2>

        <h3><a name="return_opaque_pointer-spec"></a>Class
          <code>return_opaque_pointer</code></h3>

        <p><code>return_opaque_pointer</code> is a model of
          <a href="ResultConverter.html#ResultConverterGenerator-concept">
            ResultConverterGenerator</a>
          which can be used to wrap C++ functions returning pointers to
          undefined types such that the return value is copied into a
          new Python object.</p>
        <p>In addition to specifying the <code>return_opaque_pointer</code>
          policy the <a href="opaque.html#BOOST_PYTHON_OPAQUE_SPECIALIZED_TYPE_ID-spec">
          <code>BOOST_PYTHON_OPAQUE_SPECIALIZED_TYPE_ID</code></a> macro must be
          used to define specializations for the 
          <a href="type_id.html#type_id-spec">type_id</a> function
          on the type pointed to by returned pointer.</p>

    <h4><a name="return_opaque_pointer-spec-synopsis"></a>Class
    <code>return_opaque_pointer</code> synopsis</h4>
<pre>
namespace boost { namespace python
{
    struct return_opaque_pointer
    {
        template &lt;class R&gt; struct apply;
    };
}}
</pre>

    <h4><a name="return_opaque_pointer-spec-metafunctions"></a>Class
    <code>return_opaque_pointer</code> metafunctions</h4>
<pre>
template &lt;class R&gt; struct apply
</pre>

    <dl class="metafunction-semantics">
      <dt><b>Returns:</b> <code>typedef
                detail::opaque_conversion_holder&lt;R&gt;
      type;</code></dt>
    </dl>

    <h2><a name="examples"></a>Example</h2>

    <h3>C++ Module Definition</h3>
<pre>
# include &lt;boost/python/return_opaque_pointer.hpp&gt;
# include &lt;boost/python/def.hpp&gt;
# include &lt;boost/python/module.hpp&gt;
# include &lt;boost/python/return_value_policy.hpp&gt;

typedef struct opaque_ *opaque;

opaque the_op   = ((opaque) 0x47110815);

opaque get () { return the_op; }
void use (opaque op) {
    if (op != the_op)
	throw std::runtime_error (std::string ("failed"));
}

void failuse (opaque op) {
    if (op == the_op)
	throw std::runtime_error (std::string ("success"));
}

BOOST_PYTHON_OPAQUE_SPECIALIZED_TYPE_ID(opaque_)

namespace bpl = boost::python;

BOOST_PYTHON_MODULE(opaque_ext)
{
    bpl::def (
        "get", &::get, bpl::return_value_policy&lt;bpl::return_opaque_pointer&gt;());
    bpl::def ("use", &::use);
    bpl::def ("failuse", &::failuse);
}
</pre>

    <h3>Python Code</h3>
<pre>
"""
>>> from opaque_ext import *
>>> #
>>> # Check for correct conversion
>>> use(get())
>>> failuse(get())
Traceback (most recent call last):
        ...
RuntimeError: success
>>> #
>>> # Check that there is no conversion from integers ...
>>> use(0)
Traceback (most recent call last):
        ...
TypeError: bad argument type for built-in operation
>>> #
>>> # ... and from strings to opaque objects
>>> use("")
Traceback (most recent call last):
        ...
TypeError: bad argument type for built-in operation
"""
def run(args = None):
    import sys
    import doctest

    if args is not None:
        sys.argv = args
    return doctest.testmod(sys.modules.get(__name__))
    
if __name__ == '__main__':
    print "running..."
    import sys
    sys.exit(run()[0])
</pre>

    <h2><a name="see-also"></a>See Also</h2>
        <p>
          <a href="opaque.html">
            opaque</a>
        </p>

    <p>Revised 
  28 January, 2003
    </p>

    <p><i>&copy; Copyright 2003 Haufe Mediengruppe. All Rights
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