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MODBUS CRC Calculation (Performance Test)

CPU Model:

$ cat /proc/cpuinfo | grep "model name" | cut -d: -f2
Intel(R) Core(TM) i5-7400 CPU @ 3.00GHz
Intel(R) Core(TM) i5-7400 CPU @ 3.00GHz
Intel(R) Core(TM) i5-7400 CPU @ 3.00GHz
Intel(R) Core(TM) i5-7400 CPU @ 3.00GHz

Compiling:

$ gcc -O2 -Wall -Wextra -ansi -pedantic MODBUS_CRC16.c -o MODBUS_CRC16

Algorithm 1:

static uint16_t MODBUS_CRC16_v1( const unsigned char *buf, unsigned int len )
{
	uint16_t crc = 0xFFFF;
	unsigned int i = 0;
	char bit = 0;

	for( i = 0; i < len; i++ )
	{
		crc ^= buf[i];

		for( bit = 0; bit < 8; bit++ )
		{
			if( crc & 0x0001 )
			{
				crc >>= 1;
				crc ^= 0xA001;
			}
			else
			{
				crc >>= 1;
			}
		}
	}

	return crc;
}

Measuring Algorithm 1 Execution Time:

$ time ./MODBUS_CRC16 1 1000000
real	0m22.606s
user	0m22.598s
sys	0m0.005s

Algorithm 2

static uint16_t MODBUS_CRC16_v2( const unsigned char *buf, unsigned int len )
{
	static const uint16_t table[2] = { 0x0000, 0xA001 };
	uint16_t crc = 0xFFFF;
	unsigned int i = 0;
	char bit = 0;
	unsigned int xor = 0;

	for( i = 0; i < len; i++ )
	{
		crc ^= buf[i];

		for( bit = 0; bit < 8; bit++ )
		{
			xor = crc & 0x01;
			crc >>= 1;
			crc ^= table[xor];
		}
	}

	return crc;
}

Measuring Algorithm 2 Execution Time:

$ time ./MODBUS_CRC16 2 1000000
real	0m17.392s
user	0m17.389s
sys	0m0.004s

Algorithm 3

static uint16_t MODBUS_CRC16_v3( const unsigned char *buf, unsigned int len )
{
	static const uint16_t table[256] = {
	0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
	0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
	0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
	0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
	0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
	0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
	0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
	0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
	0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
	0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
	0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
	0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
	0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
	0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
	0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
	0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
	0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
	0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
	0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
	0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
	0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
	0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
	0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
	0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
	0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
	0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
	0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
	0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
	0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
	0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
	0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
	0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040 };

	uint8_t xor = 0;
	uint16_t crc = 0xFFFF;

	while( len-- )
	{
		xor = (*buf++) ^ crc;
		crc >>= 8;
		crc ^= table[xor];
	}

	return crc;
}

Measuring Algorithm 3 Execution Time:

$ time ./MODBUS_CRC16 3 1000000
real	0m2.443s
user	0m2.441s
sys	0m0.002s

License

MIT License

Copyright (c) 2019 Tiago Ventura

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

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