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(* BitByteOps.mod provides a Logitech-3.0 compatible library.
Copyright (C) 2007-2025 Free Software Foundation, Inc.
Contributed by Gaius Mulley <gaius.mulley@southwales.ac.uk>.
This file is part of GNU Modula-2.
GNU Modula-2 is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GNU Modula-2 is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. *)
IMPLEMENTATION MODULE BitByteOps ;
FROM SYSTEM IMPORT ADR, SHIFT, ROTATE, TSIZE, BITSET8, CARDINAL8 ;
(*
GetBits - returns the bits firstBit..lastBit from source.
Bit 0 of byte maps onto the firstBit of source.
*)
PROCEDURE GetBits (source: BYTE; firstBit, lastBit: CARDINAL) : BYTE ;
VAR
si : CARDINAL8 ;
sb : BITSET8 ;
mask: BITSET8 ;
i : CARDINAL ;
BEGIN
sb := VAL (BITSET8, source) ;
mask := BITSET8 {} ;
FOR i := firstBit TO lastBit DO
INCL (mask, i)
END ;
sb := VAL (BITSET8, source) * mask ;
i := 1 ;
WHILE firstBit > 0 DO
DEC (firstBit) ;
i := i*2
END ;
si := VAL (CARDINAL8, sb) ;
RETURN VAL (BYTE, si DIV VAL (CARDINAL8, i))
END GetBits ;
(*
SetBits - sets bits in, byte, starting at, firstBit, and ending at,
lastBit, with, pattern. The bit zero of, pattern, will
be placed into, byte, at position, firstBit.
*)
PROCEDURE SetBits (VAR byte: BYTE; firstBit, lastBit: CARDINAL;
pattern: BYTE) ;
VAR
pb, pp: BITSET8 ;
i, j : CARDINAL ;
BEGIN
pb := VAL (BITSET8, byte) ;
pp := VAL (BITSET8, pattern) ;
j := 0 ;
FOR i := firstBit TO lastBit DO
IF j IN pp
THEN
INCL (pb, i)
ELSE
EXCL (pb, i)
END ;
INC (j)
END ;
byte := VAL (BYTE, pb)
END SetBits ;
(*
ByteAnd - returns a bitwise (left AND right)
*)
PROCEDURE ByteAnd (left, right: BYTE) : BYTE ;
BEGIN
RETURN VAL (BYTE, VAL (BITSET8, left) * VAL (BITSET8, right))
END ByteAnd ;
(*
ByteOr - returns a bitwise (left OR right)
*)
PROCEDURE ByteOr (left, right: BYTE) : BYTE ;
BEGIN
RETURN VAL (BYTE, VAL (BITSET8, left) + VAL (BITSET8, right))
END ByteOr ;
(*
ByteXor - returns a bitwise (left XOR right)
*)
PROCEDURE ByteXor (left, right: BYTE) : BYTE ;
BEGIN
RETURN VAL (BYTE, VAL (BITSET8, left) DIV VAL (BITSET8, right))
END ByteXor ;
(*
ByteNot - returns a byte with all bits inverted.
*)
PROCEDURE ByteNot (byte: BYTE) : BYTE ;
BEGIN
RETURN VAL (BYTE, -VAL (BITSET8, byte))
END ByteNot ;
(*
ByteShr - returns a, byte, which has been shifted, count
bits to the right.
*)
PROCEDURE ByteShr (byte: BYTE; count: CARDINAL) : BYTE ;
BEGIN
RETURN VAL (BYTE, SHIFT (VAL (BITSET8, byte), count))
END ByteShr ;
(*
ByteShl - returns a, byte, which has been shifted, count
bits to the left.
*)
PROCEDURE ByteShl (byte: BYTE; count: CARDINAL) : BYTE ;
BEGIN
RETURN VAL (BYTE, SHIFT (VAL (BITSET8, byte), -VAL (INTEGER, count)))
END ByteShl ;
(*
ByteSar - shift byte arthemetic right. Preserves the top
end bit as the value is shifted right.
*)
PROCEDURE ByteSar (byte: BYTE; count: CARDINAL) : BYTE ;
VAR
b: BYTE ;
BEGIN
IF MAX(BITSET8) IN VAL(BITSET8, byte)
THEN
b := VAL (BYTE, SHIFT (VAL (BITSET8, byte), count) + BITSET8 {MAX (BITSET8)}) ;
RETURN b
ELSE
RETURN VAL (BYTE, SHIFT (VAL (BITSET8, byte), count))
END
END ByteSar ;
(*
ByteRor - returns a, byte, which has been rotated, count
bits to the right.
*)
PROCEDURE ByteRor (byte: BYTE; count: CARDINAL) : BYTE ;
BEGIN
RETURN VAL (BYTE, ROTATE (VAL (BITSET8, byte), count))
END ByteRor ;
(*
ByteRol - returns a, byte, which has been rotated, count
bits to the left.
*)
PROCEDURE ByteRol (byte: BYTE; count: CARDINAL) : BYTE ;
BEGIN
RETURN VAL (BYTE, ROTATE (VAL (BITSET8, byte), -VAL (INTEGER, count)))
END ByteRol ;
(*
HighHibble - returns the top nibble only from, byte,
in the lowest nibble position.
*)
PROCEDURE HighNibble (byte: BYTE) : BYTE ;
BEGIN
RETURN VAL (BYTE, VAL (CARDINAL8, byte) DIV 16)
END HighNibble ;
(*
LowNibble - returns the low nibble only from, byte.
The top nibble is replaced by zeros.
*)
PROCEDURE LowNibble (byte: BYTE) : BYTE ;
BEGIN
RETURN VAL (BYTE, VAL (BITSET8, byte) * BITSET8 {0..3})
END LowNibble ;
(*
Swap - swaps the low and high nibbles in the, byte.
*)
PROCEDURE Swap (byte: BYTE) : BYTE ;
BEGIN
RETURN VAL(BYTE,
VAL(BITSET8, VAL (CARDINAL8,
VAL (BITSET8, byte) *
BITSET8 {4..7}) DIV 16) +
VAL(BITSET8, byte) * BITSET8 {0..3})
END Swap ;
END BitByteOps.
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