------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- S Y S T E M . B I T _ O P S -- -- -- -- B o d y -- -- -- -- Copyright (C) 1996-2019, 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 -- -- . -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ pragma Compiler_Unit_Warning; with System; use System; with System.Unsigned_Types; use System.Unsigned_Types; with Ada.Exceptions; use Ada.Exceptions; with Ada.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 Ada.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; pragma No_Return (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 (Constraint_Error'Identity, "operand lengths are unequal"); end Raise_Error; end System.Bit_Ops;