point_traits.h

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 * $Id: point_traits.h 4302 2012-02-07 23:14:39Z rusu $
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#ifndef PCL_POINT_TRAITS_H_
#define PCL_POINT_TRAITS_H_

#include <sensor_msgs/PointField.h>
#include <boost/type_traits/remove_all_extents.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/mpl/assert.hpp>

namespace pcl 
{

  namespace fields
  {
    // Tag types get put in this namespace
  }

  namespace traits
  {
    // Metafunction to return enum value representing a type
    template<typename T> struct asEnum {};
    template<> struct asEnum<int8_t>   { static const uint8_t value = sensor_msgs::PointField::INT8;    };
    template<> struct asEnum<uint8_t>  { static const uint8_t value = sensor_msgs::PointField::UINT8;   };
    template<> struct asEnum<int16_t>  { static const uint8_t value = sensor_msgs::PointField::INT16;   };
    template<> struct asEnum<uint16_t> { static const uint8_t value = sensor_msgs::PointField::UINT16;  };
    template<> struct asEnum<int32_t>  { static const uint8_t value = sensor_msgs::PointField::INT32;   };
    template<> struct asEnum<uint32_t> { static const uint8_t value = sensor_msgs::PointField::UINT32;  };
    template<> struct asEnum<float>    { static const uint8_t value = sensor_msgs::PointField::FLOAT32; };
    template<> struct asEnum<double>   { static const uint8_t value = sensor_msgs::PointField::FLOAT64; };

    // Metafunction to return type of enum value 
    template<int> struct asType {};
    template<> struct asType<sensor_msgs::PointField::INT8>    { typedef int8_t   type; };
    template<> struct asType<sensor_msgs::PointField::UINT8>   { typedef uint8_t  type; };
    template<> struct asType<sensor_msgs::PointField::INT16>   { typedef int16_t  type; };
    template<> struct asType<sensor_msgs::PointField::UINT16>  { typedef uint16_t type; };
    template<> struct asType<sensor_msgs::PointField::INT32>   { typedef int32_t  type; };
    template<> struct asType<sensor_msgs::PointField::UINT32>  { typedef uint32_t type; };
    template<> struct asType<sensor_msgs::PointField::FLOAT32> { typedef float    type; };
    template<> struct asType<sensor_msgs::PointField::FLOAT64> { typedef double   type; };

    // Metafunction to decompose a type (possibly of array of any number of dimensions) into
    // its scalar type and total number of elements.
    template<typename T> struct decomposeArray
    {
      typedef typename boost::remove_all_extents<T>::type type;
      static const uint32_t value = sizeof(T) / sizeof(type);
    };

    // For non-POD point types, this is specialized to return the corresponding POD type.
    template<typename PointT> 
    struct POD
    {
      typedef PointT type;
    };

    // name
    /* This really only depends on Tag, but we go through some gymnastics to avoid ODR violations.
       We template it on the point type PointT to avoid ODR violations when registering multiple
       point types with shared tags.
       The dummy parameter is so we can partially specialize name on PointT and Tag but leave it
       templated on dummy. Each specialization declares a static char array containing the tag
       name. The definition of the static member would conflict when linking multiple translation
       units that include the point type registration. But when the static member definition is
       templated (on dummy), we sidestep the ODR issue.
    */
    template<class PointT, typename Tag, int dummy = 0>
    struct name : name<typename POD<PointT>::type, Tag, dummy>
    {
      // Contents of specialization:
      // static const char value[];
      
      // Avoid infinite compile-time recursion
      BOOST_MPL_ASSERT_MSG((!boost::is_same<PointT, typename POD<PointT>::type>::value),
                           POINT_TYPE_NOT_PROPERLY_REGISTERED, (PointT&));
    };

    // offset
    template<class PointT, typename Tag>
    struct offset : offset<typename POD<PointT>::type, Tag>
    {
      // Contents of specialization:
      // static const size_t value;
      
      // Avoid infinite compile-time recursion
      BOOST_MPL_ASSERT_MSG((!boost::is_same<PointT, typename POD<PointT>::type>::value),
                           POINT_TYPE_NOT_PROPERLY_REGISTERED, (PointT&));
    };

    // datatype
    template<class PointT, typename Tag>
    struct datatype : datatype<typename POD<PointT>::type, Tag>
    {
      // Contents of specialization:
      // typedef ... type;
      // static const uint8_t value;
      // static const uint32_t size;
      
      // Avoid infinite compile-time recursion
      BOOST_MPL_ASSERT_MSG((!boost::is_same<PointT, typename POD<PointT>::type>::value),
                           POINT_TYPE_NOT_PROPERLY_REGISTERED, (PointT&));
    };

    // fields
    template<typename PointT>
    struct fieldList : fieldList<typename POD<PointT>::type>
    {
      // Contents of specialization:
      // typedef boost::mpl::vector<...> type;
      
      // Avoid infinite compile-time recursion
      BOOST_MPL_ASSERT_MSG((!boost::is_same<PointT, typename POD<PointT>::type>::value),
                           POINT_TYPE_NOT_PROPERLY_REGISTERED, (PointT&));
    };

  } //namespace traits


  template <typename PointInT, typename OutT>
  struct CopyIfFieldExists 
  {
    typedef typename traits::POD<PointInT>::type Pod;

    CopyIfFieldExists (const PointInT &pt, 
                       const std::string &field, 
                       bool &exists, 
                       OutT &value)
      : pt_ (reinterpret_cast<const Pod&>(pt)), name_ (field), exists_ (exists), value_ (value)
    {
      exists_ = false;
    }

    CopyIfFieldExists (const PointInT &pt, 
                       const std::string &field, 
                       OutT &value)
      : pt_ (reinterpret_cast<const Pod&>(pt)), name_ (field), exists_ (exists_tmp_), value_ (value)
    {
    }

    template <typename Key> inline void
    operator() ()
    {
      if (name_ == pcl::traits::name<PointInT, Key>::value)
      {
        exists_ = true;
        typedef typename pcl::traits::datatype<PointInT, Key>::type T;
        const uint8_t* data_ptr = reinterpret_cast<const uint8_t*>(&pt_) + pcl::traits::offset<PointInT, Key>::value;
        value_ = *reinterpret_cast<const T*>(data_ptr);
      }
    }

    private:
      const Pod &pt_;
      const std::string &name_;
      bool &exists_;
      // Bogus entry
      bool exists_tmp_;
      OutT &value_;
  };
}

#endif  //#ifndef PCL_POINT_TRAITS_H_