// // FILE: CRC32.cpp // AUTHOR: Rob Tillaart // PURPOSE: Arduino class for CRC32; // URL: https://github.com/RobTillaart/CRC #include "CRC32.h" CRC32::CRC32() { reset(); } CRC32::CRC32(uint32_t polynome, uint32_t XORstart, uint32_t XORend, bool reverseIn, bool reverseOut) { _polynome = polynome; _startMask = XORstart; _endMask = XORend; _reverseIn = reverseIn; _reverseOut = reverseOut; _crc = 0; _started = false; _count = 0; _canYield = true; } void CRC32::reset() { _polynome = CRC32_DEFAULT_POLYNOME; _startMask = 0; _endMask = 0; _crc = 0; _reverseIn = false; _reverseOut = false; _started = false; _count = 0; _canYield = true; } void CRC32::restart() { _started = true; _crc = _startMask; _count = 0; } void CRC32::add(uint8_t value) { _count++; if (_canYield && ((_count & 0xFF) == 0)) yield(); _update(value); } void CRC32::add(const uint8_t * array, uint16_t length) { while (length--) { add(*array++); } } uint32_t CRC32::getCRC() { uint32_t rv = _crc; if (_reverseOut) rv = _reverse(rv); rv ^=_endMask; return rv; } void CRC32::_update(uint8_t value) { if (!_started) restart(); if (_reverseIn) value = _reverse8(value); _crc ^= ((uint32_t)value) << 24; for (uint8_t i = 8; i; i--) { if (_crc & (1UL << 31)) { _crc <<= 1; _crc ^= _polynome; } else { _crc <<= 1; } } } uint32_t CRC32::_reverse(uint32_t in) { uint32_t x = in; x = (((x & 0xAAAAAAAA) >> 1) | ((x & 0x55555555) << 1)); x = (((x & 0xCCCCCCCC) >> 2) | ((x & 0x33333333) << 2)); x = (((x & 0xF0F0F0F0) >> 4) | ((x & 0x0F0F0F0F) << 4)); x = (((x & 0xFF00FF00) >> 8) | ((x & 0x00FF00FF) << 8)); x = (x >> 16) | (x << 16); return x; } uint8_t CRC32::_reverse8(uint8_t in) { uint8_t x = in; x = (((x & 0xAA) >> 1) | ((x & 0x55) << 1)); x = (((x & 0xCC) >> 2) | ((x & 0x33) << 2)); x = ((x >> 4) | (x << 4)); return x; } // -- END OF FILE --