Blackboard Serialization

Serialization refers to the process of converting a structure (such as the Blackboard on the Nao) into a format suitable for transmitting over a network (such as the rUNSWift network), where the structure can be reconstructed (such as in Offnao).

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To add a blackboard variable to be serialized

Where x is the variable you want to serialize, T is its type, and n is the current blackboard class version:

• Blackboard.tcc:

BOOST_CLASS_VERSION(Blackboard, n);

becomes:

BOOST_CLASS_VERSION(Blackboard, n + 1);

• Blackboard.tcc, shallowSerialize, add some lines like:

if (version > n) { ar & x; }

• Blackboard.cpp, initialize the variable to something sensible in the no-argument constructor

To remove a blackboard variable from being serialized

Where x is the variable you want to not serialize, T is its type, and n is the current blackboard class version:

• Blackboard.tcc:

BOOST_CLASS_VERSION(Blackboard, n);

becomes:

BOOST_CLASS_VERSION(Blackboard, n + 1);

• Blackboard.tcc, shallowSerialize:

  ar & x;

  becomes:

   if(version <= n) {
       T tmp;
       ar & tmp;
    }
  

  Note: There is a Garbage class if T no longer exists. See Pose.tcc for an example.

Changing the type of a blackboard variable and loading the old types information

Where x is the variable you want to serialize, T1 is the old type, T2 is the new type, and n is the current blackboard class version:

• Blackboard.tcc:

BOOST_CLASS_VERSION(Blackboard, n);

becomes:

BOOST_CLASS_VERSION(Blackboard, n + 1);

• Blackboard.tcc, shallowSerialize:

ar & x;

becomes:

if(version <= n) { T1 tmp; ar & tmp; x = convert(tmp); } else { ar & x; }

Note: There is a Garbage class if T1 no longer exists. See Pose.tcc for an example.

Combining multiple blackboard variable into a wrapper class and loading the old types' information

Where x and y are the variables you want to combine into xy, T1x and T1y are the old types, T2 is the new type, and n is the current blackboard class version:

• Blackboard.tcc:

BOOST_CLASS_VERSION(Blackboard, n);

becomes:

BOOST_CLASS_VERSION(Blackboard, n + 1);

• Blackboard.tcc, shallowSerialize:

ar & x; ... ar & y;

becomes:

T1x x; if(version <= n) { ar & x; } ... if(version <= n) { T1y y; ar & y; xy = convert(x, y); } else { ar & xy; }

Note: There is a Garbage class if T1x or T1y no longer exist. See Pose.tcc for an example.