Question

如何为用户定义的C ++类提供所有三个函数：msgpack_pack，msgpack_unpack和msgpack_object（以及它们的含义，确切地说是什么？）（以同样的方式MSGPACK_DEFINE为包含普通旧数据数组（例如dobule[]或char[]）的非数组POD / UD类型执行此操作，因此我的类可以更好地使用更高级别 - 级别类，在地图或向量中包含此类？

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];
};

msgpack_ *成员的功能是什么？

Answer 1

感谢那个回答我问题的人，我感到不满并探索了msgpack的实际未记录的代码库。这是前面提到的函数的例子，有一些解释，我的数量（由于缺少文档而大大不完整）的理解：

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 { 

  }
};

如何使用POD阵列msgpack一个用户定义的C ++类？

1 个答案: