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Diffstat (limited to 'gcc/ada/s-crc32.ads')
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diff --git a/gcc/ada/s-crc32.ads b/gcc/ada/s-crc32.ads new file mode 100644 index 000000000..b450c8cd3 --- /dev/null +++ b/gcc/ada/s-crc32.ads @@ -0,0 +1,83 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT LIBRARY COMPONENTS -- +-- -- +-- S Y S T E M . C R C 3 2 -- +-- -- +-- S p e c -- +-- -- +-- Copyright (C) 2001-2009, 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. -- +-- -- +------------------------------------------------------------------------------ + +-- 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. + +pragma Compiler_Unit; + +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; |