srecord: crc16.h Source File

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crc16.h
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1//
2// srecord - manipulate eprom load files
3// Copyright (C) 2000-2003, 2006-2010, 2012 Peter Miller
4//
5// This program is free software; you can redistribute it and/or modify
6// it under the terms of the GNU Lesser General Public License as published by
7// the Free Software Foundation; either version 3 of the License, or (at
8// your option) any later version.
9//
10// This program is distributed in the hope that it will be useful,
11// but WITHOUT ANY WARRANTY; without even the implied warranty of
12// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13// General Public License for more details.
14//
15// You should have received a copy of the GNU Lesser General Public License
16// along with this program. If not, see <http://www.gnu.org/licenses/>.
17//
18//
19// See http://www.joegeluso.com/software/articles/ccitt.htm for a great
20// write-up on the CRC16 calculation.
21//
22
23#ifndef SRECORD_CRC16_H
24#define SRECORD_CRC16_H
25
26#include <stddef.h>
27
28namespace srecord
29{
30
31/**
32 * The crc16 class is used to represent the running value of a 16-bit
33 * cyclic redundancy check of series of bytes.
34 *
35 * Note: this CRC16 works for systems that process the leaast
36 * significant bit of each byte first, and working to wards the most
37 * significant bit.
38 *
39 * If you were expecting MSB first (you may not even know it) this
40 * code will give you "wrong" answers. Try using the bitrev filter.
41 */
42 class crc16
43{
44public:
45 // See http://en.wikipedia.org/wiki/Cyclic_redundancy_check
46 // for table of polynomials.
47 enum
48 {
49 /**
50 * X.25, V.41, HDLC, XMODEM, Bluetooth, SD, CRC-CCITT
51 */
52 polynomial_ccitt = 0x1021,
53
54 /**
55 * CRC-16-IBM, Bisync, Modbus, USB, ANSI X3.28, CRC-16-ANSI
56 */
57 polynomial_ansi = 0x8005,
58
59 /**
60 * CRC-16-DNP, DNP, IEC 870, M-Bus
61 */
62 polynomial_dnp = 0x3D65,
63
64 /**
65 * CRC-16-DECT
66 */
67 polynomial_dect = 0x0589,
68
69 /**
70 * CRC-16-T10-DIF, SCSI DIF
71 */
72 polynomial_t10_dif = 0x8BB7,
73 };
74
75 /**
76 * The polynomial_by_name class method is used to take the name
77 * of a CRC-16 polynamlial, and return the value of the CRC-16
78 * polynomial corresponding to that name.
79 */
80 static int polynomial_by_name(const char *name);
81
82 enum seed_mode_t
83 {
84 seed_mode_ccitt,
85 seed_mode_xmodem,
86 seed_mode_broken
87 };
88
89 /**
90 * The destructor.
91 */
92 virtual ~crc16();
93
94 enum bit_direction_t
95 {
96 bit_direction_most_to_least,
97 bit_direction_least_to_most,
98 };
99
100 /**
101 * The default constructor.
102 *
103 * @param seed_mode
104 * This selects which CRC16 calculation seed is to be used.
105 * @param augment
106 * This is true if the 16-zero-bit augmentation is desired.
107 * This is the default. False if no augmentation is desired.
108 * @param polynomial
109 * The checksum polynomial.
110 * @param bitdir
111 * The direction of bits in a characters as they pass through
112 * the algorithm.
113 */
114 crc16(seed_mode_t seed_mode = seed_mode_ccitt, bool augment = true,
115 unsigned short polynomial = polynomial_ccitt,
116 bit_direction_t bitdir = bit_direction_most_to_least);
117
118 /**
119 * The copy constructor.
120 */
121 crc16(const crc16 &);
122
123 /**
124 * The assignment operator.
125 */
126 crc16 &operator=(const crc16 &);
127
128 /**
129 * The get method is used to obtain the running value of the cyclic
130 * redundancy check.
131 */
132 unsigned short get() const;
133
134 /**
135 * The next method is used to advance the state by one byte.
136 */
137 void next(unsigned char);
138
139 /**
140 * The nextbuf method is used to advance the state by a series of bytes.
141 */
142 void nextbuf(const void *, size_t);
143
144 /**
145 * The print_table method may be used to print the table being used.
146 * This is principally for debugging the table generation process.
147 */
148 void print_table(void) const;
149
150private:
151 /**
152 * The state instance variable is used to remember the running
153 * value of the 16-bit cyclic redundancy check.
154 */
155 unsigned short state;
156
157 /**
158 * The augment instance variable is used to remember whether or
159 * not the 16 zero bits of augmentation are to be processed before
160 * reporting the result.
161 */
162 bool augment;
163
164 /**
165 * The polynomial instance variable is used to remember the CRC
166 * polynomial being calculated with. Note that if the bitdir is
167 * low-to-high then the bits in the polynomial will be reversed.
168 */
169 unsigned short polynomial;
170
171 /**
172 * The bitdir instance variable is sued to remember the direction
173 * of bits in a characters as they pass through the algorithm.
174 */
175 bit_direction_t bitdir;
176
177 /**
178 * The table instance variable is used to remember the results of 8
179 * shift-and-process operations for each byte value. This is used
180 * to improve efficiency. It is filled in the the #calculate_table
181 * method, called from the constructor.
182 */
183 unsigned short table[256];
184
185 /**
186 * The calculate_table method is called by the constructor to fill
187 * in the #table instance variable.
188 */
189 void calculate_table(void);
190
191 /**
192 * The updcrc method is to add another byte of data to the running
193 * CRC state. It is called by the #next and next_buf methods.
194 */
195 inline unsigned short updcrc(unsigned char c, unsigned short state) const;
196};
197
198};
199
200#endif // SRECORD_CRC16_H
srecord::crc16::print_table
void print_table(void) const
The print_table method may be used to print the table being used.
srecord::crc16::operator=
crc16 & operator=(const crc16 &)
The assignment operator.
srecord::crc16::seed_mode_t
seed_mode_t
Definition crc16.h:83
srecord::crc16::seed_mode_xmodem
@ seed_mode_xmodem
Definition crc16.h:85
srecord::crc16::seed_mode_broken
@ seed_mode_broken
Definition crc16.h:86
srecord::crc16::seed_mode_ccitt
@ seed_mode_ccitt
Definition crc16.h:84
srecord::crc16::nextbuf
void nextbuf(const void *, size_t)
The nextbuf method is used to advance the state by a series of bytes.
srecord::crc16::polynomial_ccitt
@ polynomial_ccitt
X.25, V.41, HDLC, XMODEM, Bluetooth, SD, CRC-CCITT.
Definition crc16.h:52
srecord::crc16::polynomial_ansi
@ polynomial_ansi
CRC-16-IBM, Bisync, Modbus, USB, ANSI X3.28, CRC-16-ANSI.
Definition crc16.h:57
srecord::crc16::polynomial_dect
@ polynomial_dect
CRC-16-DECT.
Definition crc16.h:67
srecord::crc16::polynomial_dnp
@ polynomial_dnp
CRC-16-DNP, DNP, IEC 870, M-Bus.
Definition crc16.h:62
srecord::crc16::polynomial_t10_dif
@ polynomial_t10_dif
CRC-16-T10-DIF, SCSI DIF.
Definition crc16.h:72
srecord::crc16::get
unsigned short get() const
The get method is used to obtain the running value of the cyclic redundancy check.
srecord::crc16::~crc16
virtual ~crc16()
The destructor.
srecord::crc16::bit_direction_t
bit_direction_t
Definition crc16.h:95
srecord::crc16::bit_direction_least_to_most
@ bit_direction_least_to_most
Definition crc16.h:97
srecord::crc16::bit_direction_most_to_least
@ bit_direction_most_to_least
Definition crc16.h:96
srecord::crc16::crc16
crc16(seed_mode_t seed_mode=seed_mode_ccitt, bool augment=true, unsigned short polynomial=polynomial_ccitt, bit_direction_t bitdir=bit_direction_most_to_least)
The default constructor.
srecord::crc16::polynomial_by_name
static int polynomial_by_name(const char *name)
The polynomial_by_name class method is used to take the name of a CRC-16 polynamlial,...
srecord::crc16::crc16
crc16(const crc16 &)
The copy constructor.
srecord::crc16::next
void next(unsigned char)
The next method is used to advance the state by one byte.
srecord
Definition adler16.h:25