221 lines
7.2 KiB
Ada
221 lines
7.2 KiB
Ada
------------------------------------------------------------------------------
|
|
-- --
|
|
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
|
|
-- --
|
|
-- S Y S T E M . B I T _ O P S --
|
|
-- --
|
|
-- B o d y --
|
|
-- --
|
|
-- Copyright (C) 1996-2013, 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. --
|
|
-- --
|
|
------------------------------------------------------------------------------
|
|
|
|
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;
|