serialize_msg.h

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/* Author: Ioan Sucan */
 
#pragma once
 
#include <ros/ros.h>
#include <Python.h>
#include <boost/python.hpp>
#include <string>
#include <stdexcept>
#include <type_traits>
 
namespace moveit
{
namespace py_bindings_tools
{
class ByteString : public boost::python::object
{
public:
  // constructors for bp::handle and friends
  BOOST_PYTHON_FORWARD_OBJECT_CONSTRUCTORS(ByteString, boost::python::object)
  ByteString() : boost::python::object(boost::python::handle<>(PyBytes_FromString("")))
  {
  }
  explicit ByteString(const char* s) : boost::python::object(boost::python::handle<>(PyBytes_FromString(s)))
  {
  }
  explicit ByteString(const std::string& s)
    : boost::python::object(boost::python::handle<>(PyBytes_FromStringAndSize(s.c_str(), s.size())))
  {
  }
  // bp::list[] returns a proxy which has to be converted to an object first
  template <typename T>
  explicit ByteString(const boost::python::api::proxy<T>& proxy) : boost::python::object(proxy)
  {
  }
  template <typename T, typename std::enable_if<ros::message_traits::IsMessage<T>::value, int>::type = 0>
  explicit ByteString(const T& msg)
    : boost::python::object(
          boost::python::handle<>(PyBytes_FromStringAndSize(nullptr, ros::serialization::serializationLength(msg))))
  {
    ros::serialization::OStream stream_arg(reinterpret_cast<uint8_t*>(PyBytes_AS_STRING(ptr())),
                                           PyBytes_GET_SIZE(ptr()));
    ros::serialization::serialize(stream_arg, msg);
  }
 
  template <typename T>
  void deserialize(T& msg) const
  {
    static_assert(sizeof(uint8_t) == sizeof(char), "ros/python buffer layout mismatch");
    char* buf = PyBytes_AsString(ptr());
    // buf == nullptr on error
    if (!buf)
    {
      throw std::runtime_error("Underlying python object is not a Bytes/String instance");
    }
    // unfortunately no constructor with const uint8_t
    ros::serialization::IStream stream_arg(reinterpret_cast<uint8_t*>(buf), PyBytes_GET_SIZE(ptr()));
    ros::serialization::deserialize(stream_arg, msg);
  }
};
 
template <typename T>
ByteString serializeMsg(const T& msg)
{
  return ByteString(msg);
}
 
template <typename T>
void deserializeMsg(const ByteString& data, T& msg)
{
  data.deserialize(msg);
}
 
}  // namespace py_bindings_tools
}  // namespace moveit
 
namespace boost
{
namespace python
{
namespace converter
{
// only accept Python 3 Bytes / Python 2 String instance when used as C++ function parameter
template <>
struct object_manager_traits<moveit::py_bindings_tools::ByteString>
#if PY_VERSION_HEX >= 0x03000000
  : pytype_object_manager_traits<&PyBytes_Type, moveit::py_bindings_tools::ByteString>
#else
  : pytype_object_manager_traits<&PyString_Type, moveit::py_bindings_tools::ByteString>
#endif
 
{
};
}  // namespace converter
}  // namespace python
}  // namespace boost