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lib: pretty ip_masklen and masklen2ip

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nonwithstanding any desire for optimisation, these versions are shorter
and more concise.  reading the comments, they might even be easier to
understand.

I've tested them on i686 and x86_64, and checked that correct assembler
code is emitted for ARM, MIPS and PowerPC.

IPv6 is left as an exercise for another day, none of the ideas I had led
to a "yes, this is the one to go with" solution.

Signed-off-by: David Lamparter <equinox@diac24.net>
This commit is contained in:
David Lamparter 2012-04-04 00:14:36 +02:00
parent a3537862f3
commit e96b312150
1 changed files with 19 additions and 109 deletions
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128
lib/prefix.c
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@ -31,79 +31,6 @@
/* Maskbit. */
static const u_char maskbit[] = {0x00, 0x80, 0xc0, 0xe0, 0xf0,
0xf8, 0xfc, 0xfe, 0xff};
static const u_int32_t maskbytes_big_endian[] =
{
0x00000000, /* /0 0.0.0.0 */
0x80000000, /* /1 128.0.0.0 */
0xc0000000, /* /2 192.0.0.0 */
0xe0000000, /* /3 224.0.0.0 */
0xf0000000, /* /4 240.0.0.0 */
0xf8000000, /* /5 248.0.0.0 */
0xfc000000, /* /6 252.0.0.0 */
0xfe000000, /* /7 254.0.0.0 */
0xff000000, /* /8 255.0.0.0 */
0xff800000, /* /9 255.128.0.0 */
0xffc00000, /* /10 255.192.0.0 */
0xffe00000, /* /11 255.224.0.0 */
0xfff00000, /* /12 255.240.0.0 */
0xfff80000, /* /13 255.248.0.0 */
0xfffc0000, /* /14 255.252.0.0 */
0xfffe0000, /* /15 255.254.0.0 */
0xffff0000, /* /16 255.255.0.0 */
0xffff8000, /* /17 255.255.128.0 */
0xffffc000, /* /18 255.255.192.0 */
0xffffe000, /* /19 255.255.224.0 */
0xfffff000, /* /20 255.255.240.0 */
0xfffff800, /* /21 255.255.248.0 */
0xfffffc00, /* /22 255.255.252.0 */
0xfffffe00, /* /23 255.255.254.0 */
0xffffff00, /* /24 255.255.255.0 */
0xffffff80, /* /25 255.255.255.128 */
0xffffffc0, /* /26 255.255.255.192 */
0xffffffe0, /* /27 255.255.255.224 */
0xfffffff0, /* /28 255.255.255.240 */
0xfffffff8, /* /29 255.255.255.248 */
0xfffffffc, /* /30 255.255.255.252 */
0xfffffffe, /* /31 255.255.255.254 */
0xffffffff /* /32 255.255.255.255 */
};
static const u_int32_t maskbytes_little_endian[] =
{
0x00000000, /* /0 0.0.0.0 */
0x00000080, /* /1 128.0.0.0 */
0x000000c0, /* /2 192.0.0.0 */
0x000000e0, /* /3 224.0.0.0 */
0x000000f0, /* /4 240.0.0.0 */
0x000000f8, /* /5 248.0.0.0 */
0x000000fc, /* /6 252.0.0.0 */
0x000000fe, /* /7 254.0.0.0 */
0x000000ff, /* /8 255.0.0.0 */
0x000080ff, /* /9 255.128.0.0 */
0x0000c0ff, /* /10 255.192.0.0 */
0x0000e0ff, /* /11 255.224.0.0 */
0x0000f0ff, /* /12 255.240.0.0 */
0x0000f8ff, /* /13 255.248.0.0 */
0x0000fcff, /* /14 255.252.0.0 */
0x0000feff, /* /15 255.254.0.0 */
0x0000ffff, /* /16 255.255.0.0 */
0x0080ffff, /* /17 255.255.128.0 */
0x00c0ffff, /* /18 255.255.192.0 */
0x00e0ffff, /* /19 255.255.224.0 */
0x00f0ffff, /* /20 255.255.240.0 */
0x00f8ffff, /* /21 255.255.248.0 */
0x00fcffff, /* /22 255.255.252.0 */
0x00feffff, /* /23 255.255.254.0 */
0x00ffffff, /* /24 255.255.255.0 */
0x80ffffff, /* /25 255.255.255.128 */
0xc0ffffff, /* /26 255.255.255.192 */
0xe0ffffff, /* /27 255.255.255.224 */
0xf0ffffff, /* /28 255.255.255.240 */
0xf8ffffff, /* /29 255.255.255.248 */
0xfcffffff, /* /30 255.255.255.252 */
0xfeffffff, /* /31 255.255.255.254 */
0xffffffff /* /32 255.255.255.255 */
};
static const struct in6_addr maskbytes6[] =
{
@ -527,11 +454,15 @@ void
masklen2ip (const int masklen, struct in_addr *netmask)
{
assert (masklen >= 0 && masklen <= IPV4_MAX_BITLEN);
#if (BYTE_ORDER == LITTLE_ENDIAN)
netmask->s_addr = maskbytes_little_endian[masklen];
#elif (BYTE_ORDER == BIG_ENDIAN)
netmask->s_addr = maskbytes_big_endian[masklen];
#endif
/* left shift is only defined for less than the size of the type.
* we unconditionally use long long in case the target platform
* has defined behaviour for << 32 (or has a 64-bit left shift) */
if (sizeof(unsigned long long) > 4)
netmask->s_addr = htonl(0xffffffffULL << (32 - masklen));
else
netmask->s_addr = htonl(masklen ? 0xffffffffU << (32 - masklen) : 0);
}
/* Convert IP address's netmask into integer. We assume netmask is
@ -539,43 +470,22 @@ masklen2ip (const int masklen, struct in_addr *netmask)
u_char
ip_masklen (struct in_addr netmask)
{
u_char len;
u_char *pnt;
u_char *end;
u_char val;
len = 0;
pnt = (u_char *) &netmask;
end = pnt + 4;
while ((pnt < end) && (*pnt == 0xff))
{
len+= 8;
pnt++;
}
if (pnt < end)
{
val = *pnt;
while (val)
{
len++;
val <<= 1;
}
}
return len;
uint32_t tmp = ~ntohl(netmask.s_addr);
if (tmp)
/* clz: count leading zeroes. sadly, the behaviour of this builtin
* is undefined for a 0 argument, even though most CPUs give 32 */
return __builtin_clz(tmp);
else
return 32;
}
/* Apply mask to IPv4 prefix (network byte order). */
void
apply_mask_ipv4 (struct prefix_ipv4 *p)
{
assert (p->prefixlen >= 0 && p->prefixlen <= IPV4_MAX_BITLEN);
#if (BYTE_ORDER == LITTLE_ENDIAN)
p->prefix.s_addr &= maskbytes_little_endian[p->prefixlen];
#elif (BYTE_ORDER == BIG_ENDIAN)
p->prefix.s_addr &= maskbytes_big_endian[p->prefixlen];
#endif
struct in_addr mask;
masklen2ip(p->prefixlen, &mask);
p->prefix.s_addr &= mask.s_addr;
}
/* If prefix is 0.0.0.0/0 then return 1 else return 0. */