UDP (User Datagram Protocol) datagram: C++/STL parsing library

UDP is a simple stateless transport layer (AKA OSI layer 4) protocol, one of the core Internet protocols. It provides source and destination ports, basic checksumming, but provides not guarantees of delivery, order of packets, or duplicate delivery.

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of UDP (User Datagram Protocol) datagram using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Using Kaitai Struct in C++/STL usually consists of 3 steps.

  1. We need to create an STL input stream (std::istream).
    • One can open a stream for reading from a local file:
      #include <fstream>
      
      std::ifstream is("path/to/local/file.udp_datagram", std::ifstream::binary);
    • Or one can prepare a stream for reading from existing std::string str:
      #include <sstream>
      
      std::istringstream is(str);
    • Or one can parse arbitrary char* buffer in memory, given that we know its size:
      #include <sstream>
      
      const char buf[] = { ... };
      std::string str(buf, sizeof buf);
      std::istringstream is(str);
  2. We need to wrap our input stream into Kaitai stream:
    #include <kaitai/kaitaistream.h>
    
    kaitai::kstream ks(&is);
  3. And finally, we can invoke the parsing:
    udp_datagram_t data(&ks);

After that, one can get various attributes from the structure by invoking getter methods like:

data.src_port() // => get src port

C++/STL source code to parse UDP (User Datagram Protocol) datagram

udp_datagram.h

#ifndef UDP_DATAGRAM_H_
#define UDP_DATAGRAM_H_

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

#include "kaitai/kaitaistruct.h"

#include <stdint.h>

#if KAITAI_STRUCT_VERSION < 7000L
#error "Incompatible Kaitai Struct C++/STL API: version 0.7 or later is required"
#endif

/**
 * UDP is a simple stateless transport layer (AKA OSI layer 4)
 * protocol, one of the core Internet protocols. It provides source and
 * destination ports, basic checksumming, but provides not guarantees
 * of delivery, order of packets, or duplicate delivery.
 */

class udp_datagram_t : public kaitai::kstruct {

public:

    udp_datagram_t(kaitai::kstream* p__io, kaitai::kstruct* p__parent = 0, udp_datagram_t* p__root = 0);

private:
    void _read();

public:
    ~udp_datagram_t();

private:
    uint16_t m_src_port;
    uint16_t m_dst_port;
    uint16_t m_length;
    uint16_t m_checksum;
    std::string m_body;
    udp_datagram_t* m__root;
    kaitai::kstruct* m__parent;

public:
    uint16_t src_port() const { return m_src_port; }
    uint16_t dst_port() const { return m_dst_port; }
    uint16_t length() const { return m_length; }
    uint16_t checksum() const { return m_checksum; }
    std::string body() const { return m_body; }
    udp_datagram_t* _root() const { return m__root; }
    kaitai::kstruct* _parent() const { return m__parent; }
};

#endif  // UDP_DATAGRAM_H_

udp_datagram.cpp

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

#include "udp_datagram.h"



udp_datagram_t::udp_datagram_t(kaitai::kstream* p__io, kaitai::kstruct* p__parent, udp_datagram_t* p__root) : kaitai::kstruct(p__io) {
    m__parent = p__parent;
    m__root = this;
    _read();
}

void udp_datagram_t::_read() {
    m_src_port = m__io->read_u2be();
    m_dst_port = m__io->read_u2be();
    m_length = m__io->read_u2be();
    m_checksum = m__io->read_u2be();
    m_body = m__io->read_bytes_full();
}

udp_datagram_t::~udp_datagram_t() {
}