Change in libosmocore[master]: bitvec_read_field(): indicate errors using errno

[fixeria]

fixeria has posted comments on this change. ( https://gerrit.osmocom.org/c/libosmocore/+/26307 )

Change subject: bitvec_read_field(): indicate errors using errno
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Patch Set 1:

> Patch Set 1: Code-Review+1
> 
> deprecating the function would be the clean solution IMHO, but if you say it's not worth it... fine with me.

If we go for bitvec_read_field2(), we would have to rework a lot of stuff in osmo-pcu. Basically all invocations of this function, for example:

  uint64_t field = bitvec_read_field(bv, offset, len);

would need to be rewritten to:

  uint64_t field;

  if (bitvec_read_field2(bv, &field, offset, len) != 0)
    // handle error

The problem here is that oftentimes it makes more sense to check if the vector has enough data *once*, and then invoke bitvec_read_field() many times without any checks. Here is a good example from osmo-pcu:

  data->PAYLOAD_TYPE = bitvec_read_field(vector, &readIndex, 2);
  data->RRBP = bitvec_read_field(vector, &readIndex, 2);
  data->SP = bitvec_read_field(vector, &readIndex, 1);
  data->USF = bitvec_read_field(vector, &readIndex, 3);

This is why I prefer the errno approach: you get a possibility to detect errors, but you don't force the user to use the new API, what makes sense in places where checking for errors is not needed.


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Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Change-Id: I2cc734caa3365d03c2ae2b3f2cd9544933c25e9e
Gerrit-Change-Number: 26307
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de>
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Gerrit-Reviewer: dexter <pmaier at sysmocom.de>
Gerrit-Reviewer: laforge <laforge at osmocom.org>
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Gerrit-Comment-Date: Thu, 18 Nov 2021 13:10:17 +0000
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