JNetwork.hh

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#ifndef __JSYSTEM__JNETWORK__
#define __JSYSTEM__JNETWORK__

#include <unistd.h>
#include <netdb.h>
#include <arpa/inet.h>

#include <string.h>
#include <sstream>

#include "JLang/JException.hh"

/**
 * \file
 * Hostname and IP address functions.
 * \author mdejong
 */
namespace JSYSTEM {}
namespace JPP { using namespace JSYSTEM; }

namespace JSYSTEM {


  namespace {

    using JLANG::JSystemException;


    /**
     * Auxiliary class to compare endianess of network and system.
     */
    class JCompareEndian {
    public:
      /**
       * Default constructor.
       */
      JCompareEndian() :
        endian(ntohs(0x1234) == 0x1234) 
      {}


      /**
       * Function object operator.
       *
       * \return              true if network and system endianess same; else false
       */
      bool operator()() const 
      { 
        return endian; 
      }


    private:
      const bool endian;
    };
  }


  /**
   * Function object operator.
   *
   * \return              true if network and system endianess same; else false
   */
  static const JCompareEndian compareEndian;


  /**
   * Get host name.
   *
   * Note that to obtain a host name including the domain name, 
   * JSYSTEM::getHostname(JSYSTEM::getIPnumber()) should be used.
   *
   * \return              host name
   */
  inline std::string getHostname()
  {
    const size_t MAXIMUM_LENGTH = 256;
    char  buffer[MAXIMUM_LENGTH];

    if (gethostname(buffer, MAXIMUM_LENGTH) == 0)
      return std::string(buffer);
    else
      throw JSystemException("Unknown host name.");
  }



  /**
   * Get host name.
   *
   * \param  ip           IP number
   * \return              host name
   */
  inline std::string getHostname(const int ip)
  {
    in_addr buffer;

    buffer.s_addr = ip;

    hostent* p = gethostbyaddr(&buffer, sizeof(in_addr), AF_INET);

    if (p != NULL)
      return std::string(p->h_name);
    else
      throw JSystemException("Unknown IP address.");
  }


  /**
   * Get IP number.
   *
   * \param  host_name    host name
   * \return              IP number
   */
  inline int getIPnumber(const std::string& host_name)
  {
    int ip = -1;

    std::string buffer = host_name;

    if (buffer == "" || buffer == "localhost")
      buffer = getHostname();

    const hostent* hp = gethostbyname(buffer.c_str());

    if (hp != NULL)
      memcpy((char *) &ip, hp->h_addr, sizeof(int));

    return ip;
  }


  /**
   * Get IP number.
   *
   * \return              IP number
   */
  inline int getIPnumber()
  {
    return getIPnumber(getHostname());
  }


  /**
   * Get IP address (decimal-dot notation).
   *
   * \param  ip           IP number
   * \return              IP address
   */
  inline std::string getIPaddress(const int ip)
  {
    std::ostringstream os;

    if (compareEndian())
      os << ((ip >> 24) & 0xFF) << '.'
         << ((ip >> 16) & 0xFF) << '.'
         << ((ip >>  8) & 0xFF) << '.'
         << ((ip >>  0) & 0xFF);
    else
      os << ((ip >>  0) & 0xFF) << '.'
         << ((ip >>  8) & 0xFF) << '.'
         << ((ip >> 16) & 0xFF) << '.'
         << ((ip >> 24) & 0xFF);
  
    return os.str();
  }


  /**
   * Get IP address (decimal-dot notation).
   *
   * \return              IP address
   */
  inline std::string getIPaddress()
  {
    return getIPaddress(getIPnumber());
  }


  /**
   * Get host identifier within network.
   *
   * \param  ip           IP number
   * \return              ID
   */
  inline unsigned short getSubaddress(const int ip)
  {
    if (ntohs(0x1234) == 0x1234) 
      return (unsigned short) (ip & 0x0000FFFF);
    else
      return (unsigned short) (((ip & 0xFF000000) >> 24) |
                               ((ip & 0x00FF0000) >>  8) );
  }


  /**
   * Get host identifier within network.
   *
   * \return              ID
   */
  inline unsigned short getSubaddress()
  {
    return getSubaddress(getIPnumber());
  }
}

#endif