On Sat, Dec 10, 2005 at 11:42:05AM +0900, JINMEI Tatuya / [EMAIL
PROTECTED]@C#:H wrote:
> >>>>> On Fri, 9 Dec 2005 18:28:14 -0500,
> >>>>> Roy Smith <[EMAIL PROTECTED]> said:
>
> > Is there a standard API for getting the prefix given an address and a
> > prefix length? I.e., I've got
> > "FFEE:0200:0045:0000:0000:0000:0123:0012" and 64 and I want to get
> > "FFEE:0200:0045:0000:0000:0000:0000:0000".
>
> > I looked in RFC 3493 and 3542 and didn't see anything in either one
> > that looked like it did this. Did I just miss it, or does it not
> > exist?
>
> There's no standard API for this as far as I know.
Pretty sure there isn't. I don't see the need for it myself, it
is easy enough to implement. I'm sure there are people willing to
share code for this.
For a reasonably quick implementation, you could use memset() for
the 0-bytes, and have an array with the bitmasks for the remainder.
Something like:
struct in6_addr *addr;
uint8_t plen, div8;
uint8_t mask[] = { 0, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe };
...
div8 = plen / 8;
if (div8 < 15)
memset(&addr->s6_addr[1 + div8], 0, 15 - div8);
if (div8 < 16)
addr->s6_addr[div8] = addr->s6_addr[div8] & mask[plen % 8];
The above is not tested, but should be ok...
Stig
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