aboutsummaryrefslogtreecommitdiffstats
path: root/gcc-4.9/gcc/ada/s-crc32.ads
diff options
context:
space:
mode:
Diffstat (limited to 'gcc-4.9/gcc/ada/s-crc32.ads')
-rw-r--r--gcc-4.9/gcc/ada/s-crc32.ads83
1 files changed, 83 insertions, 0 deletions
diff --git a/gcc-4.9/gcc/ada/s-crc32.ads b/gcc-4.9/gcc/ada/s-crc32.ads
new file mode 100644
index 000000000..7d9e15859
--- /dev/null
+++ b/gcc-4.9/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) 2001-2013, 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. --
+-- --
+------------------------------------------------------------------------------
+
+-- 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_Warning;
+
+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;