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+------------------------------------------------------------------------------
+-- --
+-- 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;