Re^6: ECC computation

[LanX]

> more than five times faster than my previous one:

Cool, it works?

> Yes, I'm not a frequent user of pack and unpack

neither am I, so I left it to you ... ;-)

[choroba]

> Cool, it works?

It works the same way as my previous solutions. The specification was vague and there were no test cases, so I'm waiting for the OP to confirm its correctness.

Update: BTW, have you noticed the id of your node (as well as this one) is a possible output?

[LanX]

> BTW, have you noticed the id of your node (as well as this one) is a possible output?

Now that you mention it...

we should keep replying ... but only as long as error correction fits ;-)

update

[id://11111012] damn!

[savangadi]

Thanks, it is quite fast, but doesn't seem to match parity I have. My specification was perhaps ambiguous.

I tried online parity calculator from here.

For example, I entered my hex data 7EA0F6A0 and clicked 'use extra parity bit'. Then the hamming code it generated is 0111111 (The CGI code for this is such that it puts the code in LSB bits for some reason).

With the Perl code, I see ECC as 0110110.

[choroba]

OK, so just reverse all the masks and store the bits in reverse order into each @r:

my @masks = qw( 01010110101010101010110101011011
                10011011001100110011011001101101
                11100011110000111100011110001110
                00000011111111000000011111110000
                00000011111111111111100000000000
                11111100000000000000000000000000
                11111111111111111111111111111111 );
sub ecc {
    my ($hex) = @_;
    my $d = unpack 'B32', pack 'H8', $hex;
    my @r;
    unshift @r, unpack '%1B*', $_ & $d for @masks;
    $r[0] = unpack '%1B*', $r[0] . join "", @r[ 1 .. $#r ];
    return join "", @r
}