kyle johnson
/
PololuQik2
Example
Fork of PololuQik2 by
CRC7.h
- Committer:
- johnson6987
- Date:
- 2014-09-15
- Revision:
- 1:1ac7b13ff4c3
- Parent:
- 0:511d65ef1276
File content as of revision 1:1ac7b13ff4c3:
/** * @file CRC7.h * @author Edward Wilson (edwilson1989@gmail.com) * @date Dec 16, 2010 * @brief Cyclic Redundancy Check Class. This class computes a CRC7 of the provided data. * * */ #ifndef CRC7_H_ #define CRC7_H_ #define CRC7_POLY 0x91 /**< The Chosen Polynomial for CRC7. This is a standard value */ /** * This is a CRC7 implementation for checking validity of messages. It will compute * a checksum which can be used to determine if a message has been recieved unaltered. * This is used particularly over wireless tranmission or noisy serial lines. * * This implements a stored CRC table. This will taken up 256 bytes of RAM when the object * is instantiated. The reason for using a stored CRC table is speed. This is a compromise * between speed and storage spaces. * * This could possibly be static object. */ class CRC7 { public: /** * Default constructor. This method sets up the CRC table with pre-hashed values. */ CRC7(); /** * this method will generate the CRC7 checksum for the supplied message. It will be returned * from this method. * * @param message[] the message to be hashed. * @param length the length of the message to be hashed in characters. * @return the checksum computed. */ unsigned char CRC(unsigned char message[], unsigned int length); private: /** * Used to retrieve the value from the CRCTable. * * @see GenerateCRCTable() * @param val the character which the hash is required for. * @return the precomputed hash. */ unsigned char GetCRC(unsigned char val); /** * Generates the CRC table which is used for lookups during operation. * This method is faster than having to compute the hash code each time * however it comes at a cost of using up valuable RAM. */ void GenerateCRCTable(); /** * The array of characters which stores the precomputed hash codes. */ unsigned char CRCTable[256]; }; #endif /* CRC7_H_ */