/*
* Copyright (c) 1999 Kungliga Tekniska Högskolan
* (Royal Institute of Technology, Stockholm, Sweden).
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed by the Kungliga Tekniska
*      Högskolan and its contributors.
*
* 4. Neither the name of the Institute nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: addrtostr.c,v 1.6 2024/09/02 16:15:29 christos Exp $");
#endif

#include <config.h>

#include "netdissect-stdinc.h"
#include "addrtostr.h"

#include <stdio.h>
#include <string.h>

/*
*
*/

#ifndef IN6ADDRSZ
#define IN6ADDRSZ   16   /* IPv6 T_AAAA */
#endif

#ifndef INT16SZ
#define INT16SZ     2    /* word size */
#endif

const char *
addrtostr (const void *src, char *dst, size_t size)
{
   const u_char *srcaddr = (const u_char *)src;
   const char digits[] = "0123456789";
   int i;
   const char *orig_dst = dst;

   if (size < INET_ADDRSTRLEN) {
       errno = ENOSPC;
       return NULL;
   }
   for (i = 0; i < 4; ++i) {
       int n = *srcaddr++;
       int non_zerop = 0;

       if (non_zerop || n / 100 > 0) {
           *dst++ = digits[n / 100];
           n %= 100;
           non_zerop = 1;
       }
       if (non_zerop || n / 10 > 0) {
           *dst++ = digits[n / 10];
           n %= 10;
           non_zerop = 1;
       }
       *dst++ = digits[n];
       if (i != 3)
           *dst++ = '.';
   }
   *dst++ = '\0';
   return orig_dst;
}

/*
* Convert IPv6 binary address into presentation (printable) format.
*/
const char *
addrtostr6 (const void *src, char *dst, size_t size)
{
 /*
  * Note that int32_t and int16_t need only be "at least" large enough
  * to contain a value of the specified size.  On some systems, like
  * Crays, there is no such thing as an integer variable with 16 bits.
  * Keep this in mind if you think this function should have been coded
  * to use pointer overlays.  All the world's not a VAX.
  */
 const u_char *srcaddr = (const u_char *)src;
 char *dp;
 size_t space_left, added_space;
 int snprintfed;
 struct {
   int base;
   int len;
 } best, cur;
 uint16_t words [IN6ADDRSZ / INT16SZ];
 int  i;

 /* Preprocess:
  *  Copy the input (bytewise) array into a wordwise array.
  *  Find the longest run of 0x00's in src[] for :: shorthanding.
  */
 for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++)
     words[i] = (srcaddr[2*i] << 8) | srcaddr[2*i + 1];

 best.len = 0;
 best.base = -1;
 cur.len = 0;
 cur.base  = -1;
 for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
   if (words[i] == 0) {
     if (cur.base == -1)
          cur.base = i, cur.len = 1;
     else cur.len++;
   } else if (cur.base != -1) {
     if (best.base == -1 || cur.len > best.len)
        best = cur;
     cur.base = -1;
   }
 }
 if ((cur.base != -1) && (best.base == -1 || cur.len > best.len))
    best = cur;
 if (best.base != -1 && best.len < 2)
    best.base = -1;

 /* Format the result.
  */
 dp = dst;
 space_left = size;
#define APPEND_CHAR(c) \
   { \
       if (space_left == 0) { \
           errno = ENOSPC; \
           return (NULL); \
       } \
       *dp++ = c; \
       space_left--; \
   }
 for (i = 0; i < (IN6ADDRSZ / INT16SZ); i++) {
   /* Are we inside the best run of 0x00's?
    */
   if (best.base != -1 && i >= best.base && i < (best.base + best.len)) {
     if (i == best.base)
         APPEND_CHAR(':');
     continue;
   }

   /* Are we following an initial run of 0x00s or any real hex?
    */
   if (i != 0)
      APPEND_CHAR(':');

   /* Is this address an encapsulated IPv4?
    */
   if (i == 6 && best.base == 0 &&
       (best.len == 6 || (best.len == 5 && words[5] == 0xffff)))
   {
     if (!addrtostr(srcaddr+12, dp, space_left)) {
       errno = ENOSPC;
       return (NULL);
     }
     added_space = strlen(dp);
     dp += added_space;
     space_left -= added_space;
     break;
   }
   snprintfed = snprintf (dp, space_left, "%x", words[i]);
   if (snprintfed < 0)
       return (NULL);
   if ((size_t) snprintfed >= space_left) {
       errno = ENOSPC;
       return (NULL);
   }
   dp += snprintfed;
   space_left -= snprintfed;
 }

 /* Was it a trailing run of 0x00's?
  */
 if (best.base != -1 && (best.base + best.len) == (IN6ADDRSZ / INT16SZ))
    APPEND_CHAR(':');
 APPEND_CHAR('\0');

 return (dst);
}