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hitachi.c

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/*! \file hitachi.c
    This file implements special Hitachi's MAC address processing.
 */


#include <string.h>


/*! \brief Subtract 4 from a given digit.
    \author Denis BEURIVE
    \param car Hexadecimal character that represents the digit.
    \param carry Pointer to an integer that will be used to signal a possible crry. The value
                 pointed by "carry" can be:
                 <ul>
                    <li>0: no carry.
                    <li>1: carry.
                 </ul>
    \return The function returns the value "car-4" in hexadecimal.
 */


static char minus4 (char car, int *carry)
{
  switch (car)
  {
    case 'F': *carry=0; return 'B';
    case 'E': *carry=0; return 'A';
    case 'D': *carry=0; return '9';
    case 'C': *carry=0; return '8';
    case 'B': *carry=0; return '7';
    case 'A': *carry=0; return '6';
    case '9': *carry=0; return '5';
    case '8': *carry=0; return '4';
    case '7': *carry=0; return '3';
    case '6': *carry=0; return '2';
    case '5': *carry=0; return '1';
    case '4': *carry=0; return '0';
    case '3': *carry=1; return 'F';
    case '2': *carry=1; return 'E';
    case '1': *carry=1; return 'D';
    case '0': *carry=1; return 'C';
  }

  *carry=0;
  return 'X';
}

/*! \brief Subtract 1 from a given digit.
    \author Denis BEURIVE
    \param car Hexadecimal character that represents the digit.
    \param carry Pointer to an integer that will be used to signal a possible crry. The value
                 pointed by "carry" can be:
                 <ul>
                    <li>0: no carry.
                    <li>1: carry.
                 </ul>
    \return The function returns the value "car-1" in hexadecimal.
 */

static char minus1 (char car, int *carry)
{
  switch (car)
  {
    case 'F': *carry=0; return 'E';
    case 'E': *carry=0; return 'D';
    case 'D': *carry=0; return 'C';
    case 'C': *carry=0; return 'B';
    case 'B': *carry=0; return 'A';
    case 'A': *carry=0; return '9';
    case '9': *carry=0; return '8';
    case '8': *carry=0; return '7';
    case '7': *carry=0; return '6';
    case '6': *carry=0; return '5';
    case '5': *carry=0; return '4';
    case '4': *carry=0; return '3';
    case '3': *carry=0; return '2';
    case '2': *carry=0; return '1';
    case '1': *carry=0; return '0';
    case '0': *carry=1; return 'F';
  }

  *carry=0;
  return 'X';
}

/*! \brief Subtract 4 from a given number writen in hexadecimal.
    \author Denis BEURIVE
    \param haddr Pointer to a zero terminated string of characters that represents the number
                 writen in hexadecimal base.
    \return The function returns a pointer to "haddr". The string "haddr" now represents the
            value "haddr-4".
    \warning This function modifies the content of the string pointed by "haddr"). If macro "USE_PLUGINS" is defined, then
             the function returns a pointer to a statically allocated buffer. Otherwize, the function returns "haddr" itself.
    \remark This function should be used to calculate the MAC address of an HITACHI modem.
 */

char* calculate_mac (char *haddr)
{
  int  i, carry, lastid;
  char r;

  #ifdef USE_PLUGINS
     static char new_mac[128];
     memset((void*)new_mac, 0, 128*sizeof(char));
  #endif

  lastid = strlen(haddr)-1;

  r = minus4 (haddr[lastid], &carry);
  haddr[lastid] = r;

  lastid--;
  for (i=lastid; ((i>=0) && carry); i--)
  {
    r = minus1 (haddr[i], &carry);
    haddr[i] = r;
  }

  #ifndef USE_PLUGINS
     return haddr;
  #else
     strncpy (new_mac, haddr, 127);
     return new_mac;
  #endif
}

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