Re^5: How to use perl digest module to calculate CRC?

However, it seems that there is a problem with this approach. Not all HEX values have a "valid" ascii value that can be sent to the digest::crc. For example: if HEX=01 --> ASCII=SOH, which is not really a char that can be sent. That means that many HEX vals can't be in the game... Am I correct about that?

No. SOH is just a byte with the numeric value 1, and it is a perfectly valid ASCII character. pack will pack it just fine.

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Comment on Re^5: How to use perl digest module to calculate CRC?

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Re^6: How to use perl digest module to calculate CRC? by guyra (Novice) on Apr 02, 2013 at 11:17 UTC
Thanks! indeed, the SOH does affect the CRC result. #data = (HEX) 3132 my $ctx = Digest::CRC->new(width => 32, poly => 0x04c11db7, init => +0xFFFFFFFF, xorout => 0xFFFFFFFF, refin => 1, refout => 1); my $r = $ctx->add( pack 'H', '3132' )->hexdigest; print "data=", (pack 'H', '3132'), "= \| r=$r=\n"; #data = (ASCII) 12 my $ctx = Digest::CRC->new(width => 32, poly => 0x04c11db7, init => +0xFFFFFFFF, xorout => 0xFFFFFFFF, refin => 1, refout => 1); my $r = $ctx->add( "12" )->hexdigest; print "data=", (pack 'H','3132'), "= \| r=$r=\n"; #data = (HEX) 310132 my $ctx = Digest::CRC->new(width => 32, poly => 0x04c11db7, init => +0xFFFFFFFF, xorout => 0xFFFFFFFF, refin => 1, refout => 1); my $r = $ctx->add(pack 'H','310132' )->hexdigest; print "data=", (pack 'H*', '310132'), "= \| r=$r=\n"; [download] Results in: `data=12= \| r=4f5344cd= data=12= \| r=4f5344cd= data=12= \| r=b243674=` [download]	[reply] [d/l] [select]

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Re^6: How to use perl digest module to calculate CRC?
by guyra (Novice) on Apr 02, 2013 at 11:17 UTC

Thanks!

indeed, the SOH does affect the CRC result.

#data = (HEX) 3132
my $ctx = Digest::CRC->new(width => 32,   poly => 0x04c11db7, init => 
+0xFFFFFFFF, xorout => 0xFFFFFFFF, refin => 1, refout => 1);
my $r = $ctx->add( pack 'H*', '3132' )->hexdigest;
print "data=", (pack 'H*', '3132'), "= | r=$r=\n";

#data = (ASCII) 12
my $ctx = Digest::CRC->new(width => 32,   poly => 0x04c11db7, init => 
+0xFFFFFFFF, xorout => 0xFFFFFFFF, refin => 1, refout => 1);
my $r = $ctx->add( "12" )->hexdigest;
print "data=", (pack 'H*','3132'), "= | r=$r=\n";

#data = (HEX) 310132
my $ctx = Digest::CRC->new(width => 32,   poly => 0x04c11db7, init => 
+0xFFFFFFFF, xorout => 0xFFFFFFFF, refin => 1, refout => 1);
my $r = $ctx->add(pack 'H*','310132' )->hexdigest;
print "data=", (pack 'H*', '310132'), "= | r=$r=\n";
[download]

Results in:

data=12= | r=4f5344cd=
data=12= | r=4f5344cd=
data=12= | r=b243674=
[download]

[reply]
[d/l]
[select]