1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
------------------------------------------------------------------------------
-- --
-- GNAT LIBRARY COMPONENTS --
-- --
-- G N A T . C R C 3 2 --
-- --
-- S p e c --
-- --
-- Copyright (C) 2004 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, 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. --
-- --
------------------------------------------------------------------------------
-- 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;
|
