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--                                                                          --

--                         GNAT LIBRARY COMPONENTS                          --

--                                                                          --

--                           G N A T . C R C 3 2                            --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--                     Copyright (C) 2004-2005, AdaCore                     --

--                                                                          --

-- 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.      --

--                                                                          --

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--  This package provides routines for computing a commonly used checksum

--  called CRC-32. This is a checksum based on treating the binary data

--  as a polynomial over a binary field, and the exact specifications of

--  the CRC-32 algorithm are as follows:

--     Name   : "CRC-32"

--     Width  : 32

--     Poly   : 04C11DB7

--     Init   : FFFFFFFF

--     RefIn  : True

--     RefOut : True

--     XorOut : FFFFFFFF

--     Check  : CBF43926

--  Note that this is the algorithm used by PKZip, Ethernet and FDDI

--  For more information about this algorithm see:

--    ftp://ftp.rocksoft.com/papers/crc_v3.txt

--  "A Painless Guide to CRC Error Detection Algorithms", Ross N. Williams

--  "Computation of Cyclic Redundancy Checks via Table Look-Up", Communications

--  of the ACM, Vol. 31 No. 8, pp.1008-1013 Aug. 1988. Sarwate, D.V.

with Ada.Streams;

with Interfaces;

with System.CRC32;

package GNAT.CRC32 is

   subtype CRC32 is System.CRC32.CRC32;

   --  Used to represent CRC32 values, which are 32 bit bit-strings

   procedure Initialize (C : out CRC32)

     renames System.CRC32.Initialize;

   --  Initialize CRC value by assigning the standard Init value (16#FFFF_FFFF)

   procedure Update

     (C     : in out CRC32;

      Value : Character)

     renames System.CRC32.Update;

   --  Evolve CRC by including the contribution from Character'Pos (Value)

   procedure Update

     (C     : in out CRC32;

      Value : String);

   --  For each character in the Value string call above routine

   procedure Wide_Update

     (C     : in out CRC32;

      Value : Wide_Character);

   --  Evolve CRC by including the contribution from Wide_Character'Pos (Value)

   --  with the bytes being included in the natural memory order.

   procedure Wide_Update

     (C     : in out CRC32;

      Value : Wide_String);

   --  For each character in the Value string call above routine

   procedure Update

     (C     : in out CRC32;

      Value : Ada.Streams.Stream_Element);

   --  Evolve CRC by including the contribution from Value

   procedure Update

     (C     : in out CRC32;

      Value : Ada.Streams.Stream_Element_Array);

   --  For each element in the Value array call above routine

   function Get_Value (C : CRC32) return Interfaces.Unsigned_32

     renames System.CRC32.Get_Value;

   --  Get_Value computes the CRC32 value by performing an XOR with the

   --  standard XorOut value (16#FFFF_FFFF). Note that this does not

   --  change the value of C, so it may be used to retrieve intermediate

   --  values of the CRC32 value during a sequence of Update calls.

   pragma Inline (Update);

   pragma Inline (Wide_Update);

end GNAT.CRC32;