Re: CRC and Serial Port

about the checksum -- you obvously know more than I do about the other end that's sending you the data, but i've always done checksums on the whole record after zeroing the checksum, so you might end up having to pack it back up using the same unpack template...

...but for calculating the checksum itself, you might end up using unpack a third time

from perldoc -f unpack:

For example, the following computes the same
number as the System V sum program:

$checksum = do {
   local $/;  # slurp!
   unpack("%32C*",<>) % 65535;
};
[download]

--twerq

Comment on Re: CRC and Serial Port Download Code

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Rea: CRC and Serial Port by baku (Scribe) on Dec 06, 2001 at 02:48 UTC
If you want to process data one block at a time, set $/ to your field length. That will save you from waiting to slurp the entire "file" before processing it.	[reply]
Re: Rea: CRC and Serial Port by twerq (Deacon) on Dec 06, 2001 at 21:23 UTC
true, you can pass a value reference to $/ which translates into a record length, but as far as I know, there's no way to tell it to read 12 "lines", where a line can be variable length. --twerq	[reply]