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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 ( [id://736720]=note: print w/replies, xml ) Need Help??


in reply to Re: How do I convert a very long bit string into a number?
in thread How do I convert a very long bit string into a number?

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)) ) ;

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