Re: dotted quad netmask conversion

[Steve Clark <sclark@xxxxxxxxxxxxx>]

On 12/07/2010 11:43 AM, Tom Lane wrote:

Steve Clark <sclark@xxxxxxxxxxxxx> writes:
  

Thanks for the response Jon. I should have stated this PG 8.1.x and '&' 
doesn't exist for network functions.
    

I don't think & does what you want anyway.  It just does a bit AND on
the two addresses, it doesn't change the masklen property.

There's probably only a small number of distinct netmasks you actually
need to handle in this conversion.  What I'd suggest is writing a simple
function with a CASE statement to translate netmask to an integer mask
length, and then you can use set_masklen to merge that result into the
address value.

			regards, tom lane

  

Googling on the net I found a couple of functions that with tweaks for 8.1
seem to work.

CREATE OR REPLACE FUNCTION inet_to_longip(v_t INET)
RETURNS BIGINT AS
$inet_to_longip$
DECLARE
    t1 TEXT;
    t2 TEXT;
    t3 TEXT;
    t4 TEXT;
    i BIGINT;

BEGIN
    t1 := SPLIT_PART(HOST(v_t), '.',1);
    t2 := SPLIT_PART(HOST(v_t), '.',2);
    t3 := SPLIT_PART(HOST(v_t), '.',3);
    t4 := SPLIT_PART(HOST(v_t), '.',4);
    i := (t1::BIGINT << 24) + (t2::BIGINT << 16) +
            (t3::BIGINT << 8) + t4::BIGINT;
    RETURN i;
END;
$inet_to_longip$ LANGUAGE plpgsql STRICT IMMUTABLE;

CREATE OR REPLACE FUNCTION netmask_bits(v_i BIGINT)
RETURNS INTEGER AS
$netmask_msb$
DECLARE
    n INTEGER;

BEGIN
    n := (32-log(2, 4294967296 - v_i ))::integer;
    RETURN n;
END;
$netmask_msb$ LANGUAGE plpgsql STRICT IMMUTABLE;

Which seems to do the trick.

select netmask_bits(inet_to_longip('255.255.255.0'));
 netmask_bits
--------------
           24

select netmask_bits(inet_to_longip('255.255.128.0'));
 netmask_bits
--------------
           17


Thanks all.

--
Stephen Clark
NetWolves
Sr. Software Engineer III
Phone: 813-579-3200
Fax: 813-882-0209
Email: steve.clark@xxxxxxxxxxxxx
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