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

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;
}
[download]

Comment on Re: How do I convert a very long bit string into a number? Download Code

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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: 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 ) ;` [download] 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 $bitstring ) ;` [download] Note that this is the same order as `vec($v, $b, 1)` 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)) ) ;` [download] 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)) ) ;` [download]	[reply] [d/l] [select]

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:

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 ) ;
[download]
```
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 $bitstring ) ;
[download]
```
Note that this is the same order as vec($v, $b, 1)
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)) ) ;
[download]
```
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)) ) ;
[download]
```

[reply]
[d/l]
[select]