2010-02-23, 12:39 AM
C provides bit shift functions >> and << which aren't available in Sinclair or ZX basic. Since I happened to have a need for such a function, I decided to drop them up here. Again, this is something that's easy on the CPU.
They work with Long Unsigned integers - and will work fine with smaller values, or you can use them as a template for 16 or 8 bit versions in assembler.
They work with Long Unsigned integers - and will work fine with smaller values, or you can use them as a template for 16 or 8 bit versions in assembler.
Code:
FUNCTION bitL(num as uLong) as uLong
REM we get DEHL as uLong
asm
SLA L
RL H
RL E
RL D
END asm
END FUNCTIONCode:
FUNCTION bitR(num as uLong) as uLong
REM we get DEHL as uLong
asm
SRA D
RES 7,D ; makes a zero shift into D instead of what was there originally. If you want this to work with signed numbers, you could always change it to res 6,d.
RR E
RR H
RR L
END asm
END FUNCTION