Maps

• Trivial map, integer-indexed:
  static const int        mon_lengths[2][MONSPERYEAR] = {
    { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
    { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
  };
  
• More sophisticated: key/value pairs
• The following map is used to dispatch functions based on the name of the command:
  #define F_NEEDARG       0x01                    /* needs an argument */
  #define F_OFFOK         0x02                    /* can turn off */
  static struct key {
          char *name;                             /* name */
          void (*f) __P((struct info *));         /* function */
          int flags;
  } keys[] = {
          { "all",        f_all,          0 },
          { "cbreak",     f_cbreak,       F_OFFOK },
          { "cols",       f_columns,      F_NEEDARG },
          { "columns",    f_columns,      F_NEEDARG },
          { "cooked",     f_sane,         0 },
          { "dec",        f_dec,          0 },
          { "everything", f_everything,   0 },
          { "extproc",    f_extproc,      F_OFFOK },
  /* [...] */
          { "size",       f_size,         0 },
          { "speed",      f_speed,        0 },
          { "tty",        f_tty,          0 },
  };
  
  static int c_key __P((const void *, const void *));
  
  static int
  c_key(a, b)
          const void *a, *b;
  {
  
          return (strcmp(((struct key *)a)->name, ((struct key *)b)->name));
  }
  
  int
  ksearch(argvp, ip)
          char ***argvp;
          struct info *ip;
  {
          char *name;
          struct key *kp, tmp;
  
          name = **argvp;
          if (*name == '-') {
                  ip->off = 1;
                  ++name;
          } else
                  ip->off = 0;
  
          tmp.name = name;
          if (!(kp = (struct key *)bsearch(&tmp, keys,
              sizeof(keys)/sizeof(struct key), sizeof(struct key), c_key)))
                  return (0);
          if (!(kp->flags & F_OFFOK) && ip->off) {
                  warnx("illegal option -- %s", name);
                  usage();
          }
          if (kp->flags & F_NEEDARG && !(ip->arg = *++*argvp)) {
                  warnx("option requires an argument -- %s", name);
                  usage();
          }
          kp->f(ip);
          return (1);
  }
  
  void
  f_all(ip)
          struct info *ip;
  {
          print(&ip->t, &ip->win, ip->ldisc, BSD);
  }
  
  

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 Last change: Friday, March 26, 2004 7:03 pm
 Unless otherwise expressly stated, all original material on this page created by Diomidis Spinellis is licensed under a Creative Commons Attribution-Share Alike 3.0 Greece License.