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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- S Y S T E M . B I T _ O P S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2025, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception 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/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package provides subprograms on bit strings. The compiler uses these
-- subprograms for packed array operations.
package System.Bit_Ops is
-- In all the following routines, the System.Address parameters
-- represent the address of the first byte of an array used to represent
-- a packed array (of type System.Unsigned_Types.Packed_Bytes{1,2,4})
-- The length in bits is passed as a separate parameter. Note that all
-- addresses must be of byte aligned arrays.
procedure Bit_And
(Left : System.Address;
Llen : Natural;
Right : System.Address;
Rlen : Natural;
Result : System.Address);
-- Bitwise "and" of given bit string with result being placed in
-- ``Result``. The and operation is allowed to destroy unused bits in
-- the last byte, i.e. to leave them set in an undefined manner. Note that
-- ``Left``, ``Right`` and ``Result`` always have the same length in bits.
--
-- The procedure raises Constraint_Error if ``Llen`` and ``Rlen`` are not
-- equal.
--
-- The bitwise "and" operation is performed byte per byte, where the number
-- of bytes is the smallest number not less than ``Llen`` (or ``Rlen``)
-- divided by the 8.
function Bit_Eq
(Left : System.Address;
Llen : Natural;
Right : System.Address;
Rlen : Natural) return Boolean;
-- ``Left`` and ``Right`` are the addresses of two bit packed arrays with
-- ``Llen`` and ``Rlen`` being the respective length in bits. The routine
-- compares the two bit strings for equality, being careful not to include
-- the unused bits in the final byte.
--
-- Note that the result is always False if ``Rlen`` is not equal to
-- ``Llen``.
--
-- Otherwise all the bytes but the last one are compared, and False is
-- returned if they aren't equal. Only the ``Llen`` mod 8 bits of the last
-- byte are compared, and false is returned if they aren't equal.
--
-- Otherwise, True is returned.
procedure Bit_Not
(Opnd : System.Address;
Len : Natural;
Result : System.Address);
-- Bitwise "not" of given bit string with result being placed in
-- ``Result``. The not operation is allowed to destroy unused bits in the
-- last byte, i.e. to leave them set in an undefined manner. Note that
-- ``Result`` and ``Opnd`` always have the same length in bits (``Len``).
--
-- The bitwise "not" operation is performed byte per byte, where the
-- number of bytes is the smallest number not less that ``Len`` divided by
-- the number of bits in a byte (8).
procedure Bit_Or
(Left : System.Address;
Llen : Natural;
Right : System.Address;
Rlen : Natural;
Result : System.Address);
-- Bitwise "or" of given bit string with result being placed in ``Result``.
-- The or operation is allowed to destroy unused bits in the last byte,
-- i.e. to leave them set in an undefined manner. Note that ``Left``,
-- ``Right`` and ``Result`` always have the same length in bits.
--
-- The implementation is similar to *Bit_And* but for the bitwise "or"
-- operation.
procedure Bit_Xor
(Left : System.Address;
Llen : Natural;
Right : System.Address;
Rlen : Natural;
Result : System.Address);
-- Bitwise "xor" of given bit string with result being placed in
-- ``Result``. The xor operation is allowed to destroy unused bits in the
-- last byte, i.e. to leave them set in an undefined manner. Note that
-- ``Left``, ``Right`` and ``Result`` always have the same length in bits.
--
-- The implementation is similar to *Bit_And* but for the bitwise "xor"
-- operation.
end System.Bit_Ops;
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