#!/usr/bin/perl -w
use strict;
use warnings;

use Math::BigInt;
use Benchmark 'cmpthese';

our $bigint;
our @bytes;

sub bigint_to_bytearray {
  my $bigint = shift;
  my @bytes;
  while(1) {
    my ($q,$r) = $bigint->brsft(8);
    push(@bytes,$r+0);
    last if $q == 0;
    $bigint = Math::BigInt->new($q);
  }
  return @bytes;
}
## This is the one I would like to speed up
## The array looks something like (127,6,64,27,166,33 .... )
sub bytearray_to_bigint {
  my @array = @_;
  my $count = Math::BigInt->new('0');
  my $result = Math::BigInt->new('0');
  foreach my $a (@array) {
    $result += $a * (256**$count++);
  }
  return $result;
}

sub bytearray_to_bigint2 {
    my $result = Math::BigInt->new('0');
    for my $byte (reverse @_) {
        my $tmp  = Math::BigInt->new($byte);
        $result  = $result->blsft(8);
        $result += $tmp;
    }
    return $result;
}

sub ba2bi2 {
    my @ba = reverse (@_, (0) x (4 - ( @_%4 || 4 ) ) );
    my $result = Math::BigInt->new(0);
    $result *= 4294967296
    , $result += $_
        for map{
                unpack 'N'
                , pack 'C4'
                , @ba[4*$_ .. 4*$_+3]
            } 0 .. ($#ba/4);
    return $result;
}

sub ba2bi2_clean {
    my @ba = reverse (@_, (0) x (4 - ( @_%4 || 4 ) ) );
    my $result = Math::BigInt->new(0);
    for (0 .. ($#ba/4)) {
    	$result *= 4294967296;
    	$result += unpack 'N', pack 'C4', @ba[4*$_ .. 4*$_+3]
    }
    return $result;
}

sub ba2bi2_nomap {
    my @ba = reverse (@_, (0) x (4 - ( @_%4 || 4 ) ) );
    my $result = Math::BigInt->new(0);
    $result *= 4294967296,
      $result += unpack 'N', pack 'C4', @ba[4*$_ .. 4*$_+3]
        for (0 .. ($#ba/4));
    return $result;
}

sub ba2bi2_unpack {
    my $result = Math::BigInt->new(0);
    $result *= 4294967296,
      $result += $_
        for unpack 'N*', reverse pack 'C'.(4*int(@_/4+1)), @_;
    return $result;
}

$|++;

$bigint = Math::BigInt->new('12345678' x 10);
@bytes  = bigint_to_bytearray($bigint);

my $comphash={
  'mult'   => 'bytearray_to_bigint(@bytes)',
  'shift'  => 'bytearray_to_bigint2(@bytes)',
  'ba2bi2' => 'ba2bi2(@bytes)',
  'nomap'  => 'ba2bi2_nomap(@bytes)',
  'clean'  => 'ba2bi2_clean(@bytes)',
  'unpack' => 'ba2bi2_unpack(@bytes)',
};

foreach my $comp (values %$comphash) {
	eval <<EVAL or die $@;
	print '$comp',"\n",$comp,"\n";
	1
EVAL
}

cmpthese(-10, $comphash);
__END__