fix for #220 bcd length encoding

[ddvk]

Here's is my proposition for fixing the bcd length encoding. This also fixes the variable encoding where an odd length was encoded with the next even number.

The problem I had with bcd is that there is no way to find out whether the length of original data was odd or even, that's why the Encoder interface, Encode return type change.

I couldn't come up with a more elegant solution.

[adamdecaf]

Thanks for opening this PR! Can you update the godoc comments to mention what that integer represents?

[ddvk]

the godoc of the Encode method?

[adamdecaf]

Yep, thanks.

[adamdecaf]

cc @alovak

Can we fix and amend that typo? @ddvk

[codecov-commenter]

Codecov Report

Patch coverage: 93.47% and project coverage change: +0.01 🎉

Comparison is base (79404f0) 73.18% compared to head (4c3426a) 73.19%.

❗ Current head 4c3426a differs from pull request most recent head c55f697. Consider uploading reports for the commit c55f697 to get more accurate results

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #221      +/-   ##
==========================================
+ Coverage   73.18%   73.19%   +0.01%     
==========================================
  Files          41       41              
  Lines        1995     1996       +1     
==========================================
+ Hits         1460     1461       +1     
  Misses        326      326              
  Partials      209      209              

Impacted Files	Coverage Δ
encoding/binary.go	30.00% <0.00%> (ø)
encoding/ebcdic1047.go	76.47% <66.66%> (ø)
encoding/ascii.go	89.47% <100.00%> (ø)
encoding/bcd.go	100.00% <100.00%> (ø)
encoding/bertlv.go	90.90% <100.00%> (-0.40%)	⬇️
encoding/ebcdic.go	100.00% <100.00%> (ø)
encoding/hex.go	87.09% <100.00%> (ø)
encoding/lbcd.go	100.00% <100.00%> (ø)
field/binary.go	60.67% <100.00%> (ø)
field/bitmap.go	74.19% <100.00%> (ø)
... and 11 more

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[alovak]

I'm not sure that there is an issue with BCD encoding and prefixes. In the issue #220 specified length does not match the length of the value that is set to the field. Here is my comment about it: #220 (comment)

Maybe, we should add length validation to avoid such issues (#58).

[alovak]

@ddvk thanks for raising the issue and your contributions. You helped us to realize that there is an issue with field packing/unpacking. I'm closing this PR as the issue is going to be addressed by this PR: #227

[ddvk]

sure, thanks a lot.