lib/dnet_ntop.c

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #include <errno.h>
   3 #include <string.h>
   4 #include <sys/types.h>
   5 #include <netinet/in.h>
   6
   7 #include "utils.h"
   8
   9 static __inline__ u_int16_t dn_ntohs(u_int16_t addr)
  10 {
  11         union {
  12                 u_int8_t byte[2];
  13                 u_int16_t word;
  14         } u;
  15
  16         u.word = addr;
  17         return ((u_int16_t)u.byte[0]) | (((u_int16_t)u.byte[1]) << 8);
  18 }
  19
  20 static __inline__ int do_digit(char *str, u_int16_t *addr, u_int16_t scale, size_t *pos, size_t len, int *started)
  21 {
  22         u_int16_t tmp = *addr / scale;
  23
  24         if (*pos == len)
  25                 return 1;
  26
  27         if (((tmp) > 0) || *started || (scale == 1)) {
  28                 *str = tmp + '0';
  29                 *started = 1;
  30                 (*pos)++;
  31                 *addr -= (tmp * scale);
  32         }
  33
  34         return 0;
  35 }
  36
  37
  38 static const char *dnet_ntop1(const struct dn_naddr *dna, char *str, size_t len)
  39 {
  40         u_int16_t addr, area;
  41         size_t pos = 0;
  42         int started = 0;
  43
  44         memcpy(&addr, dna->a_addr, sizeof(addr));
  45         addr = dn_ntohs(addr);
  46         area = addr >> 10;
  47
  48         if (dna->a_len != 2)
  49                 return NULL;
  50
  51         addr &= 0x03ff;
  52
  53         if (len == 0)
  54                 return str;
  55
  56         if (do_digit(str + pos, &area, 10, &pos, len, &started))
  57                 return str;
  58
  59         if (do_digit(str + pos, &area, 1, &pos, len, &started))
  60                 return str;
  61
  62         if (pos == len)
  63                 return str;
  64
  65         *(str + pos) = '.';
  66         pos++;
  67         started = 0;
  68
  69         if (do_digit(str + pos, &addr, 1000, &pos, len, &started))
  70                 return str;
  71
  72         if (do_digit(str + pos, &addr, 100, &pos, len, &started))
  73                 return str;
  74
  75         if (do_digit(str + pos, &addr, 10, &pos, len, &started))
  76                 return str;
  77
  78         if (do_digit(str + pos, &addr, 1, &pos, len, &started))
  79                 return str;
  80
  81         if (pos == len)
  82                 return str;
  83
  84         *(str + pos) = 0;
  85
  86         return str;
  87 }
  88
  89
  90 const char *dnet_ntop(int af, const void *addr, char *str, size_t len)
  91 {
  92         switch(af) {
  93                 case AF_DECnet:
  94                         errno = 0;
  95                         return dnet_ntop1((struct dn_naddr *)addr, str, len);
  96                 default:
  97                         errno = EAFNOSUPPORT;
  98         }
  99
 100         return NULL;
 101 }