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100 lines
2.9 KiB
C++
100 lines
2.9 KiB
C++
// Example by Ralf W. Grosse-Kunstleve
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/*
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This example shows how to make an Extension Class "pickleable".
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The world class below contains member data (secret_number) that
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cannot be restored by any of the constructors. Therefore it is
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necessary to provide the __getstate__/__setstate__ pair of pickle
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interface methods.
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For simplicity, the __dict__ is not included in the result of
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__getstate__. This is not generally recommended, but a valid
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approach if it is anticipated that the object's __dict__ will
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always be empty. Note that safety guards are provided to catch
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the cases where this assumption is not true.
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pickle3.cpp shows how to include the object's __dict__ in the
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result of __getstate__.
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For more information refer to boost/libs/python/doc/pickle.html.
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*/
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#include <string>
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#include <boost/python/module.hpp>
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#include <boost/python/class.hpp>
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#include <boost/python/list.hpp>
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#include <boost/python/tuple.hpp>
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#include <boost/python/extract.hpp>
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#include <boost/python/detail/api_placeholder.hpp>
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namespace { // Avoid cluttering the global namespace.
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// A friendly class.
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class world
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{
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public:
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world(const std::string& country) : secret_number(0) {
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this->country = country;
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}
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std::string greet() const { return "Hello from " + country + "!"; }
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std::string get_country() const { return country; }
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void set_secret_number(int number) { secret_number = number; }
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int get_secret_number() const { return secret_number; }
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private:
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std::string country;
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int secret_number;
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};
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struct world_pickle_suite : boost::python::pickle_suite
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{
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static
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boost::python::tuple
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getinitargs(const world& w)
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{
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using namespace boost::python;
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list result;
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result.append(object(w.get_country()));
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return tuple(result);
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}
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static
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boost::python::tuple
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getstate(const world& w)
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{
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using namespace boost::python;
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list result;
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result.append(object(w.get_secret_number()));
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return tuple(result);
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}
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static
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void
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setstate(world& w, boost::python::object state)
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{
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using namespace boost::python;
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extract<tuple> state_proxy(state);
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if (!state_proxy.check() || len(state_proxy()) != 1) {
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PyErr_SetString(PyExc_ValueError,
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"Unexpected argument in call to __setstate__.");
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throw_error_already_set();
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}
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long number = extract<long>(state_proxy()[0])();
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if (number != 42) w.set_secret_number(number);
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}
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};
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}
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BOOST_PYTHON_MODULE_INIT(pickle2_ext)
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{
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boost::python::class_<world>(
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"world", boost::python::args<const std::string&>())
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.def("greet", &world::greet)
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.def("get_secret_number", &world::get_secret_number)
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.def("set_secret_number", &world::set_secret_number)
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.def_pickle(world_pickle_suite())
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;
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}
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