Signature::md5 - Signature class based on MD5 checksum

makepp documentation Contained in the makepp distribution.

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Signature::md5 -- Signature class based on MD5 checksum

DESCRIPTION

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Unlike the usual signature class, this class computes an MD5 checksum of all input files. The date on your source file may change, but if you use this signature class, makepp will realize that no rebuild is necessary as long as the contents have not changed. Just make sure that no build time is actually written into the files themselves.

For C/C++ sources, Signature::c_compilation_md5 is more suitable, since it ignores comments and whitespace. That compilation method is used by default if the statement is recognized as C compilation.

makepp documentation Contained in the makepp distribution. 
# $Id: md5.pm,v 1.9 2006/06/24 01:21:34 topnerd Exp $
use strict;
package Signature::md5;

use Signature;
use Digest::MD5;

our @ISA = 'Signature';


our $md5 = bless \@ISA;		# Make the singleton object.

#
# The only subroutine we need to override is the signature method; we use
# exact matching of MD5 signatures.
#
sub signature {
  my $finfo = $_[1];		# Name the argument.

  my $stored_cksum = FileInfo::build_info_string( $finfo, "MD5_SUM");

  unless ($stored_cksum) {	# Don't bother resumming if we
				# already know the answer.

    my $fname = FileInfo::absolute_filename( $finfo );
    if(-f $fname && open my $infile, $fname) {
#      $main::warn_level and
#	print "Computing MD5 sum of $fname\n";
      my $ctx = Digest::MD5->new;	# Make a context for computing.
      $ctx->addfile( $infile );	# Read in the whole file.
      close $infile;

      # Digest key and format needs to match BuildCache::copy_from_cache
      $stored_cksum = $ctx->b64digest;
      FileInfo::set_build_info_string( $finfo, "MD5_SUM", $stored_cksum);
				# Store the checksum so we don't have to do
				# that again.
    }
    else {			# Can't open the file?
      $stored_cksum = '';
    }
  }

  return $stored_cksum;
}

1;