inet_ntop.c

#include "inet_aton.h"
#ifdef __cplusplus
extern "C" {
#endif

/*
 * Copyright (C) 1996-2001  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
 * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
 * INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
 * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#ifndef HAVE_INET_NTOP
#define NS_INT16SZ       2
#define NS_INADDRSZ     4
#define NS_IN6ADDRSZ    16

/*
 * WARNING: Don't even consider trying to compile this on a system where
 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
 */


/* char *
 * isc_net_ntop(af, src, dst, size)
 *      convert a network format address to presentation format.
 * return:
 *      pointer to presentation format address (`dst'), or NULL (see errno).
 * author:
 *      Paul Vixie, 1996.
 */
int
inet_ntop(int af, const void *src, char *dst, size_t size) {
    switch ( af ) {
        case AF_INET:
            return(inet_ntop4(src, dst, size));
#ifdef HAVE_IPV6
        case AF_INET6:
            return(inet_ntop6(src, dst, size));
#endif
        default:
            return 0;
    }
    /* NOTREACHED */
}

/* const char *
 * inet_ntop4(src, dst, size)
 *      format an IPv4 address
 * return:
 *      `dst' (as a const)
 * notes:
 *      (1) uses no statics
 *      (2) takes a unsigned char* not an in_addr as input
 * author:
 *      Paul Vixie, 1996.
 */
int
inet_ntop4(const unsigned char *src, char *dst, size_t size) {
    static const char *fmt = "%u.%u.%u.%u";
    char tmp[sizeof "255.255.255.255"];

    if ( (size_t)sprintf(tmp, fmt, src[0], src[1], src[2], src[3]) >= size ) {
        return 0;
    }
    strcpy(dst, tmp);

    return 1;
}

/* const char *
 * isc_inet_ntop6(src, dst, size)
 *      convert IPv6 binary address into presentation (printable) format
 * author:
 *      Paul Vixie, 1996.
 */
#ifdef HAVE_IPV6
int
inet_ntop6(const unsigned char *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.
     */
    char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
    struct {
        int base, len;
    } best, cur;
    unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
    int i;

    /*
     * Preprocess:
     *      Copy the input (bytewise) array into a wordwise array.
     *      Find the longest run of 0x00's in src[] for :: shorthanding.
     */
    memset(words, '\0', sizeof words);
    for ( i = 0; i < NS_IN6ADDRSZ; i++ )
        words[i / 2] |= (src[i] << ((1 - (i % 2)) << 3));
    best.base = -1;
    cur.base = -1;
    for ( i = 0; i < (NS_IN6ADDRSZ / NS_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 ) {
        if ( best.base == -1 || cur.len > best.len )
            best = cur;
    }
    if ( best.base != -1 && best.len < 2 )
        best.base = -1;

    /*
     * Format the result.
     */
    tp = tmp;
    for ( i = 0; i < (NS_IN6ADDRSZ / NS_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 )
                *tp++ = ':';
            continue;
        }
        /* Are we following an initial run of 0x00s or any real hex? */
        if ( i != 0 )
            *tp++ = ':';
        /* Is this address an encapsulated IPv4? */
        if ( i == 6 && best.base == 0 &&
             (best.len == 6 || (best.len == 5 && words[5] == 0xffff)) ) {
            if ( !inet_ntop4(src+12, tp,
                             sizeof tmp - (tp - tmp)) )
                return 0;
            tp += strlen(tp);
            break;
        }
        tp += sprintf(tp, "%x", words[i]);
    }
    /* Was it a trailing run of 0x00's? */
    if ( best.base != -1 && (best.base + best.len) ==
         (NS_IN6ADDRSZ / NS_INT16SZ) )
        *tp++ = ':';
    *tp++ = '\0';

    /*
     * Check for overflow, copy, and we're done.
     */
    if ( (size_t)(tp - tmp) > size ) {
        errno = ENOSPC;
        return 0;
    }
    strcpy(dst, tmp);
    return 1;
}
#endif /* HAVE_IPV6 */
#endif /* HAVE_INET_NTOP */

#ifdef __cplusplus
} /* end extern "C" */
#endif