| ------------------------------------------------------------------------------ |
| -- -- |
| -- 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; |
