Thing Innovations / CRC

A simple CRC library used to verify configuration data

Fork of CRC by Andrew Lindsay

crc.cpp@3:599d283e5a44, 2016-10-03 (annotated)

Committer:
SomeRandomBloke
Date:
Mon Oct 03 09:45:59 2016 +0000
Revision:
3:599d283e5a44
Parent:
2:53b7db1f47ea 
First commit for OSIO desk sensor

Who changed what in which revision?

UserRevisionLine numberNew contents of line
SomeRandomBloke 3:599d283e5a44 1 /** crc.cpp
SomeRandomBloke 3:599d283e5a44 2 *
SomeRandomBloke 3:599d283e5a44 3 * @license
SomeRandomBloke 3:599d283e5a44 4 * MIT License
SomeRandomBloke 3:599d283e5a44 5 *
SomeRandomBloke 3:599d283e5a44 6 * Copyright (c) 2016 Andrew D Lindsay/Thing Innovations https://thinginnovations.uk
SomeRandomBloke 3:599d283e5a44 7 *
SomeRandomBloke 3:599d283e5a44 8 * Permission is hereby granted, free of charge, to any person obtaining a copy
SomeRandomBloke 3:599d283e5a44 9 * of this software and associated documentation files (the "Software"), to deal
SomeRandomBloke 3:599d283e5a44 10 * in the Software without restriction, including without limitation the rights
SomeRandomBloke 3:599d283e5a44 11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
SomeRandomBloke 3:599d283e5a44 12 * copies of the Software, and to permit persons to whom the Software is
SomeRandomBloke 3:599d283e5a44 13 * furnished to do so, subject to the following conditions:
SomeRandomBloke 3:599d283e5a44 14 *
SomeRandomBloke 3:599d283e5a44 15 * The above copyright notice and this permission notice shall be included in all
SomeRandomBloke 3:599d283e5a44 16 * copies or substantial portions of the Software.
SomeRandomBloke 3:599d283e5a44 17 *
SomeRandomBloke 3:599d283e5a44 18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
SomeRandomBloke 3:599d283e5a44 19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
SomeRandomBloke 3:599d283e5a44 20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
SomeRandomBloke 3:599d283e5a44 21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
SomeRandomBloke 3:599d283e5a44 22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
SomeRandomBloke 3:599d283e5a44 23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SomeRandomBloke 3:599d283e5a44 24 * SOFTWARE.
SomeRandomBloke 3:599d283e5a44 25 *
SomeRandomBloke 3:599d283e5a44 26 */
sam_grove 0:28e16d33040f 27 #define CRC32_POLYNOMIAL 0xEDB88320L
sam_grove 0:28e16d33040f 28
SomeRandomBloke 2:53b7db1f47ea 29 void CRC32Value(unsigned long &CRCval, unsigned char c)
sam_grove 0:28e16d33040f 30 {
sam_grove 0:28e16d33040f 31 /////////////////////////////////////////////////////////////////////////////////////
sam_grove 0:28e16d33040f 32 //CRC must be initialized as zero
sam_grove 0:28e16d33040f 33 //c is a character from the sequence that is used to form the CRC
sam_grove 0:28e16d33040f 34 //this code is a modification of the code from the Novatel OEM615 specification
sam_grove 0:28e16d33040f 35 /////////////////////////////////////////////////////////////////////////////////////
SomeRandomBloke 2:53b7db1f47ea 36 unsigned long ulTemp1 = ( CRCval >> 8 ) & 0x00FFFFFFL;
SomeRandomBloke 2:53b7db1f47ea 37 unsigned long ulCRC = ((int) CRCval ^ c ) & 0xff ;
sam_grove 0:28e16d33040f 38 for (int j = 8 ; j > 0; j-- )
sam_grove 0:28e16d33040f 39 {
sam_grove 0:28e16d33040f 40 if ( ulCRC & 1 )
sam_grove 1:ec8513f94d23 41 {
sam_grove 0:28e16d33040f 42 ulCRC = ( ulCRC >> 1 ) ^ CRC32_POLYNOMIAL;
sam_grove 1:ec8513f94d23 43 }
sam_grove 0:28e16d33040f 44 else
sam_grove 1:ec8513f94d23 45 {
sam_grove 0:28e16d33040f 46 ulCRC >>= 1;
sam_grove 1:ec8513f94d23 47 }
sam_grove 0:28e16d33040f 48 }
SomeRandomBloke 2:53b7db1f47ea 49 CRCval = ulTemp1 ^ ulCRC;
sam_grove 0:28e16d33040f 50 }
sam_grove 0:28e16d33040f 51
sam_grove 0:28e16d33040f 52 /* --------------------------------------------------------------------------
sam_grove 0:28e16d33040f 53 Calculates the CRC-32 of a block of data all at once
sam_grove 0:28e16d33040f 54 //the CRC is from the complete message (header plus data)
sam_grove 0:28e16d33040f 55 //but excluding (of course) the CRC at the end
sam_grove 0:28e16d33040f 56 -------------------------------------------------------------------------- */
sam_grove 0:28e16d33040f 57 unsigned long CalculateBlockCRC32(
sam_grove 0:28e16d33040f 58 unsigned long ulCount, /* Number of bytes in the data block */
sam_grove 0:28e16d33040f 59 unsigned char *ucBuffer ) /* Data block */
sam_grove 0:28e16d33040f 60 {
sam_grove 0:28e16d33040f 61 //////////////////////////////////////////////////////////////////////
sam_grove 0:28e16d33040f 62 //the below code tests the CRC32Value procedure used in a markov form
sam_grove 0:28e16d33040f 63 //////////////////////////////////////////////////////////////////////
sam_grove 0:28e16d33040f 64 unsigned long CRC = 0;
sam_grove 1:ec8513f94d23 65 for (int i = 0; i<ulCount; i++)
sam_grove 1:ec8513f94d23 66 {
sam_grove 1:ec8513f94d23 67 CRC32Value( CRC, *ucBuffer++ );
sam_grove 1:ec8513f94d23 68 }
sam_grove 0:28e16d33040f 69 return CRC;
sam_grove 0:28e16d33040f 70 }
sam_grove 0:28e16d33040f 71
sam_grove 0:28e16d33040f 72 /*
sam_grove 0:28e16d33040f 73 unsigned long CalculateBlockCRC32(
sam_grove 0:28e16d33040f 74 unsigned long ulCount,
sam_grove 0:28e16d33040f 75 unsigned char *ucBuffer )
sam_grove 0:28e16d33040f 76 {
sam_grove 0:28e16d33040f 77 ////////////////////////////////////////////
sam_grove 0:28e16d33040f 78 //original code from the OEM615 manual
sam_grove 0:28e16d33040f 79 ////////////////////////////////////////////
sam_grove 0:28e16d33040f 80 unsigned long ulTemp1;
sam_grove 0:28e16d33040f 81 unsigned long ulTemp2;
sam_grove 0:28e16d33040f 82 unsigned long ulCRC = 0;
sam_grove 0:28e16d33040f 83 while ( ulCount-- != 0 )
sam_grove 0:28e16d33040f 84 {
sam_grove 0:28e16d33040f 85 ulTemp1 = ( ulCRC >> 8 ) & 0x00FFFFFFL;
sam_grove 0:28e16d33040f 86 ulTemp2 = CRC32Value( ((int) ulCRC ^ *ucBuffer++ ) & 0xff );
sam_grove 0:28e16d33040f 87 ulCRC = ulTemp1 ^ ulTemp2;
sam_grove 0:28e16d33040f 88 }
sam_grove 0:28e16d33040f 89 return( ulCRC );
sam_grove 0:28e16d33040f 90 }
sam_grove 0:28e16d33040f 91 */