Spin NS2 code

Sample code for spin routing protocol:
From this code we learn the information of how data packets are handled in spin routing protocols.
PacketHeaderClass::PacketHeaderClass(const char* classname, int hdrlen) :
TclClass(classname), hdrlen_(hdrlen), offset_(0)
{ }

TclObject* PacketHeaderClass::create(int, const char*const*)
{ return (0); }

void PacketHeaderClass::bind()
{
TclClass::bind();
Tcl& tcl = Tcl::instance();
tcl.evalf("%s set hdrlen_ %d", classname_, hdrlen_);
export_offsets();
add_method("offset");
}

void PacketHeaderClass::export_offsets()
{ }

void PacketHeaderClass::field_offset(const char* fieldname, int offset)
{
Tcl& tcl = Tcl::instance();
tcl.evalf("%s set offset_(%s) %d", classname_, fieldname, offset);
}

int PacketHeaderClass::method(int ac, const char*const* av)
{
Tcl& tcl = Tcl::instance();
int argc = ac - 2;
const char*const* argv = av + 2;
if (argc == 3) {

if (strcmp(argv[1], "offset") == 0) {
if (offset_) {
*offset_ = atoi(argv[2]);
return TCL_OK;
}
tcl.resultf("Warning: cannot set offset_ for %s",
classname_);
return TCL_OK;
}}
else if (argc == 2) {
if (strcmp(argv[1], "offset") == 0) {
if (offset_) {
tcl.resultf("%d", *offset_);
return TCL_OK;
}}}
return TclClass::method(argc, argv); }