lib: make masklen2ip() safer and faster
diff --git a/lib/prefix.c b/lib/prefix.c
index fff0932..7d24600 100644
--- a/lib/prefix.c
+++ b/lib/prefix.c
@@ -31,6 +31,42 @@
/* Maskbit. */
static const u_char maskbit[] = {0x00, 0x80, 0xc0, 0xe0, 0xf0,
0xf8, 0xfc, 0xfe, 0xff};
+static const u_int32_t maskbytes[] =
+{
+ 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 */
+};
/* Number of bits in prefix type. */
#ifndef PNBBY
@@ -303,23 +339,10 @@
/* Convert masklen into IP address's netmask. */
void
-masklen2ip (int masklen, struct in_addr *netmask)
+masklen2ip (const int masklen, struct in_addr *netmask)
{
- u_char *pnt;
- int bit;
- int offset;
-
- memset (netmask, 0, sizeof (struct in_addr));
- pnt = (unsigned char *) netmask;
-
- offset = masklen / 8;
- bit = masklen % 8;
-
- while (offset--)
- *pnt++ = 0xff;
-
- if (bit)
- *pnt = maskbit[bit];
+ assert (masklen >= 0 && masklen <= 32);
+ netmask->s_addr = maskbytes[masklen];
}
/* Convert IP address's netmask into integer. We assume netmask is
diff --git a/lib/prefix.h b/lib/prefix.h
index 54f47c7..675f94d 100644
--- a/lib/prefix.h
+++ b/lib/prefix.h
@@ -178,7 +178,7 @@
extern void apply_classful_mask_ipv4 (struct prefix_ipv4 *);
extern u_char ip_masklen (struct in_addr);
-extern void masklen2ip (int, struct in_addr *);
+extern void masklen2ip (const int, struct in_addr *);
/* returns the network portion of the host address */
extern in_addr_t ipv4_network_addr (in_addr_t hostaddr, int masklen);
/* given the address of a host on a network and the network mask length,