ON 20031212@6:29:42 AM at page:
http://www.piclist.com/techref/microchip/math/bit/whatbit.htm
GB-adinet-IC4 Gonzalo Damian Barco Code:

<PRE>;Gonzalo Barco
;A looped approach (a bit smaller and lot slower)
;In case you are sure there's at least one bit set you can loose the first bsf

COMPACT4BIT	MACRO	FILE
;Returns bit 3 set on error (no bits set)
	local	loop, tail
	bsf	STATUS, C	;To be sure we don't looooooooooooop forever
	clrw			;Clear counter

loop:
	rrf	FILE, F		;Send bits off the edge...
	btfsc	STATUS, C	;...on to STATUS, C
	goto 	tail		;If we hit the bit... stop
	addlw	1		;Otherwise add to the counter...
	goto	loop		;...and keep looping
tail:
	movwf	FILE		;Overwrite source with result
	ENDM
</PRE>