BitFiddleClass

     NAME
	  bitfiddleclass - Routines to do bit manipulation on 32-bit
	  integers.

     DESCRIPTION
	  The routines in this class do	bit-mainpulation on 32-bit
	  integers.  They are implemented in assembler for speed. They
	  might	be useful to do	low level interfacing and as a compact
	  way to store Booleans.

     EXAMPLE
	     external class bitfiddleClass;
	     ref(bitfiddleclass) Fiddler;
	     integer i,	mask=16RFF000000;
	     Fiddler:-new bitfiddleclass;
	     Fiddler.bit0high; !-- set bit mapping to left->right --;
	     i:=Fiddler.BitSet(i,31);	!- set the least sign. bit of
	  i;
	     i:=Fiddler.BitAnd(i,mask);	!- mask	out most sign. byte of
	  i;
	     1:=Fiddler.BitShift(i,-2);	!- divide by 4 (and zero-fill
	  signbit)

     AUTHOR
	  Boris	Magnusson, Lund	University.

     DETAILED INTERFACE
	     class BitFiddleClass;
	  Operations  for  logical  bitwise  manipulations  on	32-bit
	  integers.

	  This class only  specifies  operations  and  have  no	 state
	  varaiables.	All  data  to  the  operations	are  given  as
	  paramaters.

	  The class might serve	useful to use this class  as  a	 super
	  class	  for	more   specialized   abstractions,   such   as
	  BitSetClass.

	  Supers: -
	  Kind:	Instantiable
	  Init:	none (Defualt Bit0Low)
	  Sequencing: (Bit0Low / Bit0High / BitClear / BitSet /	BitGet
	  / BitNot / BitAnd BitIor / BitXor / BitFirst / BitShift)*

     OPERATIONS
     Bit0Low
	     procedure	Bit0Low;
	  Set bitordering so bit number	0  is  the  least  significant
	  bit.
	  bitnumbering:	31,30,29,...,0 (bit 0 lowest significans, bit
	  31 is	sign).
	  This is default.

     Bit0High
	     procedure	Bit0High;
	  Set bitordering so bit number	0 is the most significant bit.

	  bitnumbering:	0,1,2,..,31 (bit 0 is signbit, bit 31 is least
	  significant.)

     BitClear
	     integer procedure	BitClear(i,bno);
	     integer i;	! Input	bitpattern;
	     integer bno; ! Affected bit number;
	  Return the value of i	with bit numbered bno cleared (=0).

     BitSet
	     integer procedure	BitSet(i,bno);
	     integer i;	! Input	bitpattern;
	     integer bno; ! Affected bit number;
	  Return the value of i	with bit numbered bno set (=1).

     BitGet
	     Boolean procedure	BitGet(i,bno);
	     integer i;	! Input	bitpattern;
	     integer bno; ! Affected bit number;
	  Return Value of bit bno of i.

     BitNot
	     integer procedure	BitNot (i);
	     integer i;	! Input	bitpattern;
	  Return the bitwise inverted value of i.

     BitAnd
	     integer procedure	BitAnd(i,j);
	     integer i,j; ! Input bitpatterns;
	  Return the result of i AND j calculated bitwise.

     BitIor
	     integer procedure BitIor(i,j);
	     integer i,j; ! Input bitpatterns;
	  Return the result of i IOR j calculated bitwise.

     BitXor
	     integer procedure	BitXor(i,j);
	     integer i,j; ! Input bitpatterns;
	  Return the bit-number	of the first set bit in	i.   If	 there
	  is no	set bit, the result is -1.

     BitFirst
	     integer procedure	BitFirst(i);
	     integer i;	! Input	bitpattern;
	  Return the bit-number	of the first set bit in	i.   If	 there
	  is no	set bit, the result is -1.

     BitShift
	     integer procedure	BitShift(i,s);
	     integer i;	! Input	bitpattern;
	     integer s;	! multiplication with 2**s;
	  Return the integer result of shifting	i s steps. If  Bit0low
	  this	means  shifting	left (s>0) or right (s<0). If Bit0High
	  the shift direction is reversed so shift left	corresponds to
	  multiplication  and right to division	in both	cases. This is
	  a logical shift, so all bits shifted in are zeroes.