bitfields - 4425 bells & whistles

[Era Scarecrow]

Following from issue list:

bearophile_hugs 2010-10-04 18:16:44 PDT
>Another possible feature is to make std.bitmanip.bitfields 
>generate two
versions of the code, that get compiled conditionally according 
to the CPU
endianess:

> static if (std.system.endian == std.system.Endian.BigEndian) {
>    ...
> } else {
>     ...
> }

Having it endian specific brings up a couple questions.

  Which endian is 'correct'? Resolutions could be...
   a) Both are correct (Leave as is)
   b) big/little is correct and should always convert to the other 
(which one?)
   c) Specify correct type as a flag, then swaps for the other in 
generated code

  Second, which would be the best approach?
   a) swap bytes in a temporary, modify the temporary, replace 
storage? (In every function)
   b) use current endianness, then prepping saving/loading have it 
swap? (very unlikely)
   c) use ubyte array and use shifting on each byte (small Endian, 
also allows for odd byte sizes, not very likely, but possible)

  I know an instruction for the Pentium system (686+?) bswap will 
swap the appropriate bytes as a conversion and takes a single 
cycle, using assembler that can be incorporated assuming it's 
ready for it (course than the template would be updated more 
likely and not the bitfield template).