| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNU ADA RUNTIME LIBRARY (GNARL) COMPONENTS -- |
| -- -- |
| -- S Y S T E M . B I T _ O P S -- |
| -- -- |
| -- B o d y -- |
| -- -- |
| -- $Revision: 1.10 $ |
| -- -- |
| -- Copyright (C) 1996-2000 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 2, 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. See the GNU General Public License -- |
| -- for more details. You should have received a copy of the GNU General -- |
| -- Public License distributed with GNAT; see file COPYING. If not, write -- |
| -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- |
| -- MA 02111-1307, USA. -- |
| -- -- |
| -- As a special exception, if other files instantiate generics from this -- |
| -- unit, or you link this unit with other files to produce an executable, -- |
| -- this unit does not by itself cause the resulting executable to be -- |
| -- covered by the GNU General Public License. This exception does not -- |
| -- however invalidate any other reasons why the executable file might be -- |
| -- covered by the GNU Public License. -- |
| -- -- |
| -- GNAT was originally developed by the GNAT team at New York University. -- |
| -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| with GNAT.Exceptions; use GNAT.Exceptions; |
| with System; use System; |
| with System.Unsigned_Types; use System.Unsigned_Types; |
| with Unchecked_Conversion; |
| |
| package body System.Bit_Ops is |
| |
| subtype Bits_Array is System.Unsigned_Types.Packed_Bytes1 (Positive); |
| -- Unconstrained array used to interprete the address values. We use the |
| -- unaligned version always, since this will handle both the aligned and |
| -- unaligned cases, and we always do these operations by bytes anyway. |
| -- Note: we use a ones origin array here so that the computations of the |
| -- length in bytes work correctly (give a non-negative value) for the |
| -- case of zero length bit strings). |
| |
| type Bits is access Bits_Array; |
| -- This is the actual type into which address values are converted |
| |
| function To_Bits is new Unchecked_Conversion (Address, Bits); |
| |
| LE : constant := Standard'Default_Bit_Order; |
| -- Static constant set to 0 for big-endian, 1 for little-endian |
| |
| -- The following is an array of masks used to mask the final byte, either |
| -- at the high end (big-endian case) or the low end (little-endian case). |
| |
| Masks : constant array (1 .. 7) of Packed_Byte := ( |
| (1 - LE) * 2#1000_0000# + LE * 2#0000_0001#, |
| (1 - LE) * 2#1100_0000# + LE * 2#0000_0011#, |
| (1 - LE) * 2#1110_0000# + LE * 2#0000_0111#, |
| (1 - LE) * 2#1111_0000# + LE * 2#0000_1111#, |
| (1 - LE) * 2#1111_1000# + LE * 2#0001_1111#, |
| (1 - LE) * 2#1111_1100# + LE * 2#0011_1111#, |
| (1 - LE) * 2#1111_1110# + LE * 2#0111_1111#); |
| |
| |
| ----------------------- |
| -- Local Subprograms -- |
| ----------------------- |
| |
| procedure Raise_Error; |
| -- Raise Constraint_Error, complaining about unequal lengths |
| |
| ------------- |
| -- Bit_And -- |
| ------------- |
| |
| procedure Bit_And |
| (Left : Address; |
| Llen : Natural; |
| Right : Address; |
| Rlen : Natural; |
| Result : Address) |
| is |
| LeftB : constant Bits := To_Bits (Left); |
| RightB : constant Bits := To_Bits (Right); |
| ResultB : constant Bits := To_Bits (Result); |
| |
| begin |
| if Llen /= Rlen then |
| Raise_Error; |
| end if; |
| |
| for J in 1 .. (Rlen + 7) / 8 loop |
| ResultB (J) := LeftB (J) and RightB (J); |
| end loop; |
| end Bit_And; |
| |
| ------------ |
| -- Bit_Eq -- |
| ------------ |
| |
| function Bit_Eq |
| (Left : Address; |
| Llen : Natural; |
| Right : Address; |
| Rlen : Natural) |
| return Boolean |
| is |
| LeftB : constant Bits := To_Bits (Left); |
| RightB : constant Bits := To_Bits (Right); |
| |
| begin |
| if Llen /= Rlen then |
| return False; |
| |
| else |
| declare |
| BLen : constant Natural := Llen / 8; |
| Bitc : constant Natural := Llen mod 8; |
| |
| begin |
| if Llen /= Rlen then |
| return False; |
| |
| elsif LeftB (1 .. BLen) /= RightB (1 .. BLen) then |
| return False; |
| |
| elsif Bitc /= 0 then |
| return |
| ((LeftB (BLen + 1) xor RightB (BLen + 1)) |
| and Masks (Bitc)) = 0; |
| |
| else -- Bitc = 0 |
| return True; |
| end if; |
| end; |
| end if; |
| end Bit_Eq; |
| |
| ------------- |
| -- Bit_Not -- |
| ------------- |
| |
| procedure Bit_Not |
| (Opnd : System.Address; |
| Len : Natural; |
| Result : System.Address) |
| is |
| OpndB : constant Bits := To_Bits (Opnd); |
| ResultB : constant Bits := To_Bits (Result); |
| |
| begin |
| for J in 1 .. (Len + 7) / 8 loop |
| ResultB (J) := not OpndB (J); |
| end loop; |
| end Bit_Not; |
| |
| ------------ |
| -- Bit_Or -- |
| ------------ |
| |
| procedure Bit_Or |
| (Left : Address; |
| Llen : Natural; |
| Right : Address; |
| Rlen : Natural; |
| Result : Address) |
| is |
| LeftB : constant Bits := To_Bits (Left); |
| RightB : constant Bits := To_Bits (Right); |
| ResultB : constant Bits := To_Bits (Result); |
| |
| begin |
| if Llen /= Rlen then |
| Raise_Error; |
| end if; |
| |
| for J in 1 .. (Rlen + 7) / 8 loop |
| ResultB (J) := LeftB (J) or RightB (J); |
| end loop; |
| end Bit_Or; |
| |
| ------------- |
| -- Bit_Xor -- |
| ------------- |
| |
| procedure Bit_Xor |
| (Left : Address; |
| Llen : Natural; |
| Right : Address; |
| Rlen : Natural; |
| Result : Address) |
| is |
| LeftB : constant Bits := To_Bits (Left); |
| RightB : constant Bits := To_Bits (Right); |
| ResultB : constant Bits := To_Bits (Result); |
| |
| begin |
| if Llen /= Rlen then |
| Raise_Error; |
| end if; |
| |
| for J in 1 .. (Rlen + 7) / 8 loop |
| ResultB (J) := LeftB (J) xor RightB (J); |
| end loop; |
| end Bit_Xor; |
| |
| ----------------- |
| -- Raise_Error -- |
| ----------------- |
| |
| procedure Raise_Error is |
| begin |
| Raise_Exception (CE, "unequal lengths in logical operation"); |
| end Raise_Error; |
| |
| end System.Bit_Ops; |
