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crc16_ccitt.c
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crc16_ccitt.c
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/* =============================================================================
Copyright (c) 2008 Pieter Conradie [www.piconomic.co.za]
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
Title: 16-bit CRC calculator
Author(s): Pieter.Conradie
Creation Date: 2008/11/06
Revision Info: $Id: crc16_ccitt.c 117 2010-06-24 20:21:28Z pieterconradie $
============================================================================= */
/* _____STANDARD INCLUDES____________________________________________________ */
#ifdef __AVR__
// Include program space support if CRC table must be stored in FLASH
#include <avr/io.h>
#include <avr/pgmspace.h>
#endif
/* _____PROJECT INCLUDES_____________________________________________________ */
#include "crc16_ccitt.h"
/* _____LOCAL DEFINITIONS____________________________________________________ */
/**
* Option to store CRC table in RAM(SRAM) or ROM(FLASH).
*
* The table is used to decrease CRC calculation time.
* It is useful to precalculate and store the table in SRAM if
* FLASH space is limited, e.g. in a bootloader. Otherwise, SRAM
* is a limited resource and it may be better to store it in FLASH.
*/
#ifndef CRC16_CCITT_USE_RAM_TABLE
#define CRC16_CCITT_USE_RAM_TABLE 0
#endif
/* _____MACROS_______________________________________________________________ */
#if defined(__AVR__) && !CRC16_CCITT_USE_RAM_TABLE
/// Update 16-bit CRC macro
#define CRC16_CCITT_UPDATE(crc, data) \
crc = (crc >> 8) ^ pgm_read_word_near(&crc16_ccitt_table[(crc ^ (data)) & 0xff]);
#else
/// Update 16-bit CRC macro
#define CRC16_CCITT_UPDATE(crc, data) \
crc = (crc >> 8) ^ crc16_ccitt_table[(crc ^ (data)) & 0xff];
#endif
/* _____GLOBAL VARIABLES_____________________________________________________ */
/* _____LOCAL VARIABLES______________________________________________________ */
#if CRC16_CCITT_USE_RAM_TABLE
static quint16 crc16_ccitt_table[256];
#else
#ifdef __AVR__
// http://nongnu.org/avr-libc/user-manual/pgmspace.html
const quint16 crc16_ccitt_table[256] PROGMEM =
#else
static const quint16 crc16_ccitt_table[256] =
#endif
{
0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};
#endif
/* _____LOCAL FUNCTION DECLARATIONS__________________________________________ */
#if CRC16_CCITT_USE_RAM_TABLE
static void crc16_ccitt_generate_table(void);
#endif
/* _____LOCAL FUNCTIONS______________________________________________________ */
#if CRC16_CCITT_USE_RAM_TABLE
/// Function that will generate and store CRC lookup table in RAM
static void crc16_ccitt_generate_table(void)
{
quint16 value;
quint16 index;
quint8 i;
for(index=0; index<256; index++)
{
value = index;
for(i=8; i!=0; i--)
{
value = value & 1 ? (value >> 1) ^ CRC16_CCITT_POLYNOMIAL : value >> 1;
}
crc16_ccitt_table[index] = value;
}
}
#endif
/* _____GLOBAL FUNCTIONS_____________________________________________________ */
void crc16_ccitt_init(void)
{
#if CRC16_CCITT_USE_RAM_TABLE
// Precalculate 16-bit CRC table in SRAM
crc16_ccitt_generate_table();
#endif
}
quint16 crc16_ccitt_calc_byte(quint16 crc, quint8 data)
{
CRC16_CCITT_UPDATE(crc,data);
return crc;
}
quint16 crc16_ccitt_calc_data(quint16 crc, quint8* data, quint16 data_length)
{
while(data_length)
{
CRC16_CCITT_UPDATE(crc,*data);
data++;
data_length--;
}
return crc;
}
/* _____LOG__________________________________________________________________ */
/*
2008/11/06 : Pieter.Conradie
- Created
*/