xmlrpc_helpers.h

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#ifndef XMLRPCHELPERS_H
#define XMLRPCHELPERS_H

#include <sstream>
#include <ros/ros.h>

namespace xh
{

class XmlrpcHelperException : public ros::Exception
{
public:
  XmlrpcHelperException(const std::string& what)
    : ros::Exception(what) {}
};

typedef XmlRpc::XmlRpcValue Struct;
typedef XmlRpc::XmlRpcValue Array;

template <class T>
void fetchParam(ros::NodeHandle nh, const std::string& param_name, T& output)
{
  XmlRpc::XmlRpcValue val;
  if (!nh.getParamCached(param_name, val))
  {
    std::ostringstream err_msg;
    err_msg << "could not load parameter '" << param_name << "'. (namespace: "
      << nh.getNamespace() << ")";
    throw XmlrpcHelperException(err_msg.str());
  }

  output = static_cast<T>(val);
}

void checkArrayItem(const Array& col, int index)
{
  if (col.getType() != XmlRpc::XmlRpcValue::TypeArray)
    throw XmlrpcHelperException("not an array");
  if(index >= col.size())
  {
    std::ostringstream err_msg;
    err_msg << "index '" << index << "' is over array capacity";
    throw XmlrpcHelperException(err_msg.str());
  }
}

void checkStructMember(const Struct& col, const std::string& member)
{
  if (col.getType() != XmlRpc::XmlRpcValue::TypeStruct)
    throw XmlrpcHelperException("not a struct");
  if (!col.hasMember(member))
  {
    std::ostringstream err_msg;
    err_msg << "could not find member '" << member << "'";
    throw XmlrpcHelperException(err_msg.str());
  }
}

template <class T>
void getArrayItem(Array& col, int index, T& output) // XXX: XmlRpcValue::operator[] is not const
{
  checkArrayItem(col, index);
  output = static_cast<T>(col[index]);
}

template <class T>
void getStructMember(Struct& col, const std::string& member, T& output)
{
  checkStructMember(col, member);
  output = static_cast<T>(col[member]);
}

} // namespace xh

#endif // XMLRPCHELPERS_H