The ns Manual (formerly ns Notes and Documentation)1 - NM Lab at ...

send_data(ADU)Application(HttpApp, ...)process_data(ADU)Application(HttpApp, ...)Agent Wrapper(TcpApp, ...)send_data(ADU)process_data(ADU)send(bytes)recv(bytes)Agents supporting user data(HttpInvalAgent, ...)Agent (TCP, ...)packetspacketsFigure 39.1: Examples of application-level data flowprivate:AppDataType type_; // ADU typepublic:struct hdr {AppDataType type_;};public:AppData(char* b) {assert(b != NULL);type_ = ((hdr *)b)->type_;}virtual void pack(char* buf) const;}Here pack(char* buf) is used to write an AppData object into an array, and AppData(char* b) is used to build anew AppData from a “serialized” copy of the object in an array.When deriving new ADU from the base class, users may add more data, but at the same time a new pack(char *b) anda new constructor should be provided to write and read those new data members from an array. For an example as how toderive from an ADU, look at ns/webcache/http-aux.h.39.1.2 Passing data between applicationsThe base class of Application, Process, allows applications to pass data or request data between each other. It is defined asfollows:class Process {public:Process() : target_(0) {}inline Process*& target() { return target_; }342