Problems restraining read command to 32 bits -perl Post: 302334516

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Top Forums Shell Programming and Scripting Problems restraining read command to 32 bits -perl Post 302334516 by TeamUSA on Wednesday 15th of July 2009 07:03:35 PM

07-15-2009

Registered User

Problems restraining read command to 32 bits -perl

Hey everybody,

I'm having difficulty using the read command to perform a checksum operation. Whenever I print the final checksum, the result always returns FFFFFFFF, and I know thats not the checksum.

Code:

 #!/usr/bin/perl -w
  
  use strict;
  use FileHandle;
  use warnings;
  my $data = "file.bin";
  my $buffer;
  my $string;
  my $n = 0;
  my $checksum = 0;
  my $num = 0;
  my $str = unpack("B32", pack("N", shift));
  my $bits = 4;
  my $decimal;

open FILE, $data or die $!;
binmode FILE;  
 while (($n = read FILE, $buffer, 4))
 {
 
 $decimal = unpack("N", pack("B32", $buffer));
 
 {$checksum = $checksum + $decimal;
 #$num = $num + $bits;}
 
 #print "1. $num\n";
 print "2. $decimal\n";
 #print "3. $n bytes read\n";
 print "4. $checksum \n";
 }
 
 $checksum = $checksum & 0xFFFFFFFF;

Basically, I'm trying to read a binary file 32 bits at a time by unpacking them into decimal and then adding them. Furthermore, I am trying to use the $checksum & 0xFFFFFFFFF command to restrain the checksum to 32 bits. Also, just ignore the commented out stuff, I was using it for my own testing. Any assistance would be greatly appreciated.

TeamUSA

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LEARN ABOUT SUNOS

b2sum

B2SUM(1)							   User Commands							  B2SUM(1)

NAME

       b2sum - compute and check BLAKE2 message digest

SYNOPSIS

       b2sum [OPTION]... [FILE]...

DESCRIPTION

       Print or check BLAKE2 (512-bit) checksums.

       With no FILE, or when FILE is -, read standard input.

       -b, --binary
	      read in binary mode

       -c, --check
	      read BLAKE2 sums from the FILEs and check them

       -l, --length
	      digest length in bits; must not exceed the maximum for the blake2 algorithm and must be a multiple of 8

       --tag  create a BSD-style checksum

       -t, --text
	      read in text mode (default)

   The following five options are useful only when verifying checksums:
       --ignore-missing
	      don't fail or report status for missing files

       --quiet
	      don't print OK for each successfully verified file

       --status
	      don't output anything, status code shows success

       --strict
	      exit non-zero for improperly formatted checksum lines

       -w, --warn
	      warn about improperly formatted checksum lines

       --help display this help and exit

       --version
	      output version information and exit

       The  sums  are computed as described in RFC 7693.  When checking, the input should be a former output of this program.  The default mode is
       to print a line with checksum, a space, a character indicating input mode ('*' for binary, ' ' for text or where binary is  insignificant),
       and name for each FILE.

AUTHOR

       Written by Padraig Brady and Samuel Neves.

REPORTING BUGS

       GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
       Report b2sum translation bugs to <http://translationproject.org/team/>

COPYRIGHT

       Copyright (C) 2017 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       Full documentation at: <http://www.gnu.org/software/coreutils/b2sum>
       or available locally via: info '(coreutils) b2sum invocation'

GNU coreutils 8.28						   January 2018 							  B2SUM(1)