------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- S Y S T E M . B I T _ O P S -- -- -- -- B o d y -- -- -- -- Copyright (C) 1996-2005 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, 51 Franklin Street, Fifth Floor, -- -- Boston, MA 02110-1301, 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. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ with System; use System; with System.Pure_Exceptions; use System.Pure_Exceptions; 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); -- Dummy array type used to interpret 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). Note that we never allocate any -- objects of this type (we can't because they would be absurdly big). 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 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;