Underlying C++ objects are created in support of the interface specified
in Section 26.3 and are linked into the network topology
as network elements.
The single C++ Trace class is used to implement the OTcl
classes Trace/Hop, Trace/Enque, Trace/Deque,
and Trace/Drop.
The type
_ field is used to differentiate among the
various types of
traces any particular Trace object might implement.
Currently, this field may contain one of the following symbolic characters:
+ for enque, - for deque, h for hop, and
d for drop.
The overall class is defined as follows in ~ns/trace.cc:
class Trace : public Connector { protected: int type_; nsaddr_t src_; nsaddr_t dst_; Tcl_Channel channel_; int callback_; char wrk_[256]; void format(int tt, int s, int d, Packet* p); void annotate(const char* s); int show_tcphdr_; // bool flags; backward compat public: Trace(int type); ~Trace(); int command(int argc, const char*const* argv); void recv(Packet* p, Handler*); void dump(); inline char* buffer() { return (wrk_); } };The src
void Trace::recv(Packet* p, Handler* h) { format(type_, src_, dst_, p); dump(); /* hack: if trace object not attached to anything free packet */ if (target_ == 0) Packet::free(p); else send(p, h); /* \fcn[]{Connector::send} */ }The function merely formats a trace entry using the source, destination, and particular trace type character. The dump function writes the formatted entry out to the I/O handle associated with channel
Tom Henderson 2011-11-05