On Mon, Apr 9, 2018 at 11:19 PM, Gert Wollny <gw.foss...@gmail.com> wrote:
> Am Montag, den 09.04.2018, 14:03 -0400 schrieb Marek Olšák: > > On Mon, Apr 9, 2018 at 10:51 AM, Bas Vermeulen <b...@daedalean.ai> > > wrote: > Which solution is better depends on what is done more often: reading > the index or writing to the bit fields. > The bitfields are read and written, and the index is mostly read. I found four instances of the bitfields being written after which the index needs to be updated. > > > I am working on a new version of this patch. I have one version > > > which does away with all the bitfields, and uses functions to > > > update the index. > This emulates the code the compiler would create, but it requires that > for each bit field setters (and getters?) must be implemented. > Yes. I have a git branch with this change ready if that's what's wanted/needed. > > > Another approach would be to change the union to a struct, and use > > > a function to get the index. > This method has the advantage that only the access to the index needs > new implementation. > I can prepare a patch for this as well. > > > Yet another approach would be to keep the contents of the union and > > > the index in one struct, and use a function to > > > (re)calculate the index. > I don't think that would make much sense. > It adds four lines to the code, all the key->u.xxx has it's u. removed. But future implementation needs to remember to call that function if any of the bitfields are changed. Which can be annoying. There is another option: Check at configuration time whether the bit > field layout is like the low or the high endian layout you already > implemented, and instead of basing the selection of the struct layout > on the big/low-endianess of the architecture, base it on this test. > > It would probably be prudent to test both layouts and then fail > configuration if non of the two reflect the actual layout (at which > point one would have to thing about how to implement all the bit > shifting properly). Or just keep the union dependent on endianness, and add an assert/check/test to make sure that everything works as expected. > > > > > > Which would you prefer? > > > > > > > I don't mind bitfields. They make the code nice and tiny. Shifts > > would decrease readability. > The problem is, that the layout of bitfields is compiler dependend. > Let me know what you guys want to have this included. I just want it fixed, I don't really care on the form. :) Bas Vermeulen
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