Re: How to convert bigint to bytearray in perl

Hello tajinderpalsingh61, and welcome to the Monastery!

To expand on swl’s answer, here is one approach:

use strict;
use warnings;
use Data::Dump;
use Math::BigInt;

my  $string = '1677259342285725925376';
my  $n      =  Math::BigInt->new($string);
my  @bytes  =  map { ord } split //, $n->to_bytes();
    @bytes  =  map { $_ >= 128 ? $_ - 256 : $_ } @bytes;
dd \@bytes;
[download]

Output:

16:16 >perl 2015_SoPW.pl
[90, -20, -90, 53, 78, -38, 2, -128, 0]

16:16 >
[download]

Explanation: Math::BigInt->to_bytes returns a reprsentation of the integer as a byte string. split // splits that string into its component bytes. ord() turns a byte from a character into a number (its numerical representation).

The useful function map applies the expression in braces to each element of the list it receives, and returns the resulting new list; so I’ve used it twice, once to convert byte characters into their numerical representations, and again to convert those numbers above 127 into their corresponding signed 8-bit integers.

For the ?: ternary operator, see Conditional Operator. And Data::Dump is a useful CPAN module for displaying complex data structures.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^2: How to convert bigint to bytearray in perl by ikegami (Patriarch) on Aug 26, 2019 at 07:10 UTC
That's not equivalent. It fails for negative numbers, as well as positive numbers that requires a multiple of 8 bits to represent (e.g. 128-255, and 32678-65535). The following addresses the second of the above limitations: `sub bigint_to_bytearray { my $bigint = shift; die "Negative numbers not supported" if $bigint < 0; my @bytes = unpack('c', $bigint->to_bytes); unshift @bytes, 0x00 if $bytes[0] < 0; # Add sign bit if necessary return @bytes; }` [download] The above requires a relatively new version of Math::BigInt. The following is less efficient, but it works on far older versions: `sub bigint_to_bytearray { my $bigint = shift; die "Negative numbers not supported" if $bigint < 0; my @bytes = unpack('c', pack('H*', substr($bigint->as_hex, 2))); unshift @bytes, 0x00 if $bytes[0] < 0; # Add sign bit if necessary return @bytes; }` [download]	[reply] [d/l] [select]
Re^3: How to convert bigint to bytearray in perl by tajinderpalsingh61 (Initiate) on Aug 26, 2019 at 09:03 UTC
Thanks, You saved my day, How can I accept your answer?	[reply]
Re^4: How to convert bigint to bytearray in perl by hippo (Archbishop) on Aug 26, 2019 at 09:18 UTC
Once you have attained the rank of Novice you can vote on the nodes. See I just became a Novice; Why can't I vote yet? in the Voting, Reputation, Experience, and Levels section of the PerlMonks FAQ. However, just by posting the reply as you have done, other readers are aware of how the post has been of benefit to you, so just keep doing that for helpful nodes.	[reply]
Re^2: How to convert bigint to bytearray in perl by tajinderpalsingh61 (Initiate) on Aug 26, 2019 at 06:31 UTC
Thanks for your help, tried your code, unfortunately, i am getting below error. Can't locate object method "to_bytes" via package "Math::BigInt"	[reply]
Re^3: How to convert bigint to bytearray in perl by haukex (Archbishop) on Aug 26, 2019 at 06:59 UTC
Can't locate object method "to_bytes" via package "Math::BigInt" The `to_bytes` method was added in Math::BigInt 1.999807, which was distributed with Perl 5.28. You should be able to install the latest version from CPAN.	[reply] [d/l]