// magic value for messages
const uint32_t MSG_MAGIC = 0x46474653;  // "FGFS"
// protocoll version
const uint32_t PROTO_VER = 0x00010001;  // 1.1

// Message identifiers
#define CHAT_MSG_ID             1
#define UNUSABLE_POS_DATA_ID    2
#define OLD_OLD_POS_DATA_ID     3
#define OLD_POS_DATA_ID         4
#define OLD_PROP_MSG_ID         5
#define RESET_DATA_ID           6
#define POS_DATA_ID             7

// XDR demands 4 byte alignment, but some compilers use8 byte alignment
// so it's safe to let the overall size of a network message be a 
// multiple of 8!
#define MAX_CALLSIGN_LEN        8
#define MAX_CHAT_MSG_LEN        256
#define MAX_MODEL_NAME_LEN      96
#define MAX_PROPERTY_LEN        52

// Header for use with all messages sent 
struct T_MsgHdr {
    xdr_data_t  Magic;                  // Magic Value
    xdr_data_t  Version;                // Protocoll version
    xdr_data_t  MsgId;                  // Message identifier 
    xdr_data_t  MsgLen;                 // absolute length of message
    xdr_data_t  ReplyAddress;           // (player's receiver address
    xdr_data_t  ReplyPort;              // player's receiver port
    char Callsign[MAX_CALLSIGN_LEN];    // Callsign used by the player
};

// Chat message 
struct T_ChatMsg {
    char Text[MAX_CHAT_MSG_LEN];       // Text of chat message
};

// Position message
struct T_PositionMsg {
    char Model[MAX_MODEL_NAME_LEN];    // Name of the aircraft model
    // Time when this packet was generated
    xdr_data2_t time;
    xdr_data2_t lag;

    // position wrt the earth centered frame
    xdr_data2_t position[3];
    // orientation wrt the earth centered frame, stored in the angle axis
    // representation where the angle is coded into the axis length
    xdr_data_t orientation[3];
    // linear velocity wrt the earth centered frame measured in
    // the earth centered frame
    xdr_data_t linearVel[3];
    // angular velocity wrt the earth centered frame measured in
    // the earth centered frame
    xdr_data_t angularVel[3];
    // linear acceleration wrt the earth centered frame measured in
    // the earth centered frame
    xdr_data_t linearAccel[3];
    // angular acceleration wrt the earth centered frame measured in
    // the earth centered frame
    xdr_data_t angularAccel[3];
    // Padding. The alignment is 8 bytes on x86_64 because there are
    // 8-byte types in the message, so the size should be explicitly
    // rounded out to a multiple of 8. Of course, it's a bad idea to
    // put a C struct directly on the wire, but that's a fight for
    // another day...
    xdr_data_t pad;
};