Encode and decode binary-coded decimals

[jmcnamara]

Some simple one-liners for encoding and decoding binary-coded decimals (BCD).

    # Encode
    perl -le 'print join " ", map {ord pack "H2", $_} shift =~ /../g' 
+num

    # decode
    perl -le 'print unpack "H*", pack "C*", @ARGV'  num1 num2 ...

    perl -le 'print map {int($_/16).($_%16)} @ARGV' num1 num2 ...

Some examples:

    # Encode

    $ perl -le 'print join " ", map {ord pack "H2", $_} shift =~ /../g
+' 019774
    1 151 116


    # decode

    $ perl -le 'print unpack "H*", pack "C*", @ARGV' 1 151 116
    019774

You can use "h" instead of "H" for low nibble first encoding. Single digit components of the number to be encoded should be zero padded.

--
John.

[jryan]

I tried all of your snippets, and none seemed to work. For instance:

perl -le 'print join " ", map {ord pack "H2", $_} shift =~ /../g' 396

I'd expect to get: 0011 1001 0110, but instead I get 57, which isn't very binary at all :)

Similarly with decode:

perl -le 'print unpack "H*", pack "C*", @ARGV' 0011 1001 0110

Results in 0be96e (hex!) instead of 396.

These should work:

# encode
perl -e 'print sprintf("%04b ",$_) for shift =~ /\d/g' decimal

#decode
perl -e '$p=1; map{$l+=oct("0b$_")*$p;$p*=10} reverse @ARGV; print $l'
+ bcddigit1 bcddigit2 etc

Update: Updated decoder to use 5.6.1's oct("0b") feature instead of the old perlfaq way to convery binary to decimal.

[jmcnamara]

In the first case you need to use 0396 instead of 396. That's what the comment about "zero padding" refers to.

    $ perl -le 'print join " ", map {ord pack "H2", $_} shift =~ /../g
+' 0396
    3 150

I'd expect to get: 0011 1001 011

That is at odds with my expectation.:-) Nevertheless, it isn't too difficult to change these routines to support other ascii, hex or binary representations.

--
John.

[jryan]

My definition of BCD is similar to this, but maybe you are referring to something different? :)