如何使用POD阵列msgpack一个用户定义的C++类？

Question

它是如何能够提供三个功能:msgpack_pack,msgpack_unpack和msgpack_object(？还有,什么是他们的意义,精确地)为用户定义的C++类(以同样的方式MSGPACK_DEFINE做它用在非阵列POD/UD类型)包含普通老式数据数组(例如dobule[]或者char[]),所以我的类可以很好地使用更高级别的类,在地图或向量中包含这个类？

是否有任何为您自己的类或至少msgpack C++ api文档实现它们的示例？

我发现可能的API参考的唯一链接是http://redmine.msgpack.org/projects/msgpack/wiki ; 但它现在已经死了.

说,我有一个类似的结构

struct entity {
  const char name[256];
  double mat[16];
};

什么是msgpack_*成员函数呢？

Answer 1

感谢那个对我提问的人,我感到不满,并探索了msgpack的实际未记录的代码库.以下是前面提到的函数的示例,其中有一些解释,我的数量(由于缺少文档而非常不完整)理解:

struct entity {
  char name[256];
  double mat[16];

  // this function is appears to be a mere serializer
  template <typename Packer>
  void msgpack_pack(Packer& pk) const {
    // make array of two elements, by the number of class fields
    pk.pack_array(2); 

    // pack the first field, strightforward
    pk.pack_raw(sizeof(name));
    pk.pack_raw_body(name, sizeof(name));

    // since it is array of doubles, we can't use direct conversion or copying
    // memory because it would be a machine-dependent representation of floats
    // instead, we converting this POD array to some msgpack array, like this:
    pk.pack_array(16);
    for (int i = 0; i < 16; i++) {
      pk.pack_double(mat[i]);
    }
  }

  // this function is looks like de-serializer, taking an msgpack object
  // and extracting data from it to the current class fields
  void msgpack_unpack(msgpack::object o) {
    // check if received structure is an array
    if(o.type != msgpack::type::ARRAY) { throw msgpack::type_error(); }

    const size_t size = o.via.array.size;

    // sanity check
    if(size <= 0) return;
    // extract value of first array entry to a class field
    memcpy(name, o.via.array.ptr[0].via.raw.ptr, o.via.array.ptr[0].via.raw.size);

    // sanity check
    if(size <= 1) return;
    // extract value of second array entry which is array itself:
    for (int i = 0; i < 16 ; i++) {
      mat[i] = o.via.array.ptr[1].via.array.ptr[i].via.dec;
    }
  }

  // destination of this function is unknown - i've never ran into scenary
  // what it was called. some explaination/documentation needed.
  template <typename MSGPACK_OBJECT>
  void msgpack_object(MSGPACK_OBJECT* o, msgpack::zone* z) const { 

  }
};