Beefy Boxes and Bandwidth Generously Provided by pair Networks
Welcome to the Monastery
 
PerlMonks  

Answer: How do I convert a very long bit string into a number?

by jdporter (Canon)
on Jan 15, 2009 at 21:46 UTC ( #736687=categorized answer: print w/replies, xml ) Need Help??

Q&A > math > How do I convert a very long bit string into a number? - Answer contributed by jdporter

Combine unpack with Math::BigInt:
use Math::BigInt; use bigint; use strict; use warnings; sub convert_bitstring_to_number { my $bitstring = shift; my $h = unpack( 'H*', $bitstring ); my $bh = new Math::BigInt '0x'.$h; $bh->as_int; }

Replies are listed 'Best First'.
Re: Answer: How do I convert a very long bit string into a number?
by gone2015 (Deacon) on Jan 16, 2009 at 02:00 UTC

    This can be generalised for other orderings of the bytes, and of the bits in each byte, of the bitstring. Four types of bitstring can be identified:

    1. big-endian: ms-bit of first byte is the ms-bit of the multi-byte number. This is handled as shown, ie:

      my $h = unpack( 'H*', $bitstring ) ;

    2. little-endian: ls-bit of first byte is the ls-bit of the multi-byte number. This is handled:

      my $h = unpack( 'H*', scalar reverse $bitstring ) ;
      Note that this is the same order as vec($v, $b, 1)

    3. big-endian reversed bytes: ls-bit of first byte is the ms-bit of the multi-byte number. This is handled:

      my $h = unpack( 'H*', pack('b*', unpack('B*', $bitstring)) ) ;

    4. little-endian reversed bytes: ms-bit of first byte is the ls-bit of the multi-byte number. This is handled:

      my $h = unpack( 'H*', pack('b*', unpack('B*', scalar reverse $bitstr +ing)) ) ;

Log In?
Username:
Password:

What's my password?
Create A New User
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others chanting in the Monastery: (3)
As of 2020-10-22 14:27 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    My favourite web site is:












    Results (226 votes). Check out past polls.

    Notices?