+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- GNAT LIBRARY COMPONENTS --
--- --
--- S Y S T E M . C R C 3 2 --
--- --
--- S p e c --
--- --
--- $Revision: 1.1 $
--- --
--- Copyright (C) 2001 Ada Core Technologies, 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 is maintained by Ada Core Technologies Inc (http://www.gnat.com). --
--- --
-------------------------------------------------------------------------------
-
--- 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 Interfaces;
-
-package System.CRC32 is
-
- type CRC32 is new Interfaces.Unsigned_32;
- -- Used to represent CRC32 values, which are 32 bit bit-strings
-
- procedure Initialize (C : out CRC32);
- pragma Inline (Initialize);
- -- Initialize CRC value by assigning the standard Init value (16#FFFF_FFFF)
-
- procedure Update
- (C : in out CRC32;
- Value : Character);
- pragma Inline (Update);
- -- Evolve CRC by including the contribution from Character'Pos (Value)
-
- function Get_Value (C : CRC32) return Interfaces.Unsigned_32;
- pragma Inline (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.
-
-end System.CRC32;
projects / msp430-gcc.git / blobdiff