Fastest way of encoding values for RFVAR/RFVARS
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in Propeller 2
Inspired by the nibble reversing thread and some conversation I had with @moony , what is the fastest way to encode a value for fast-yet-compact FIFO retrieval?
Conditions:
- HUBEXEC, so expensive branches and no FIFO (although if you want to try optimizing for COGEXEC, who's to tell you no?)
- input value in
inp
- put encoded value in
out
(bonus points if unused high bytes are zero,but it really doesn't matter) - put encoding length in
length
- alternatively, write to hub ram with PTRB
My attempt (untested):
encode_any_signed abs tmp,inp encod tmp,tmp sca tmp,##9363 ' divide by 7 mov tmp,tmp mul tmp,#7 add tmp,#7 zerox inp,tmp encode_any mov length,#1 getbyte out,inp,#0 shr inp,#7 wz bitnz out,#7 if_z ret mov length,#2 setbyte out,inp,#1 shr inp,#7 wz bitnz out,#7+8 if_z ret mov length,#3 setbyte out,inp,#2 shr inp,#7 wz bitnz out,#7+16 if_z ret mov length,#4 setbyte out,inp,#3 shr inp,#7 wz bitnz out,#7+24 if_z ret '' error handling here
Not sure if that actually works. Also, surely, there's a better way.