Message structure

The format of a message is presented below as it is defined in the form of C structure MESSAGE.

    typedef struct  mess   {
           int    time ;
           int    drsy_time ;
           int    kind ; (*)
           int    value[10] ; (*)
           long   special_field[10] ;
           int    from ; (*)
           int    hops ;
           int    maxhops ;
           int    port ; (*)

           struct mess *next ;
    }     MESSAGE ;

The fields of the MESSAGE fall in two categories :

System specified fields

These fields obtain proper values by the simulator, so the user is not allowed to update them. These fields are the followings:

• time: When the message must be delivered to the destination process.
• drsy_time: The real part of the above field time; this is used in the simulation of a synchronizer.
• from: Source process number.
• hops: On how many links has the message been propagated till now. The value of this field is meaningfull only if the system call pass_message() has been used for the delivering of the message (i.e. if the sender and the recepient could not communicate dierctly).
• port: The port of the node on which this message has arrived.
• next: Pointer to next message in a message queue.

User specified fields

The user (the protocol to be simulated) can use these fields for his own protocol:

• kind: Kind of message.
• value[]: Information that this message must carry.
• special_field[]: Extra information that the message must carry when the previous field value[] is not sufficient.
• maxhops: The maximum distance this message can propagate.