skarg
154 lines
4.6 KiB
C
154 lines
4.6 KiB
C
/*####COPYRIGHTBEGIN####
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-------------------------------------------
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Copyright (C) 2004 Steve Karg
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to:
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The Free Software Foundation, Inc.
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59 Temple Place - Suite 330
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Boston, MA 02111-1307
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USA.
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As a special exception, if other files instantiate templates or
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use macros or inline functions from this file, or you compile
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this file and link it with other works to produce a work based
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on this file, this file does not by itself cause the resulting
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work to be covered by the GNU General Public License. However
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the source code for this file must still be made available in
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accordance with section (3) of the GNU General Public License.
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This exception does not invalidate any other reasons why a work
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based on this file might be covered by the GNU General Public
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License.
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-------------------------------------------
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####COPYRIGHTEND####*/
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#include <stddef.h>
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#include <stdint.h>
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#include <stdbool.h>
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// Accumulate "dataValue" into the CRC in crcValue.
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// Return value is updated CRC
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//
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// The ^ operator means exclusive OR.
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// Note: This function is copied directly from the BACnet standard.
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uint8_t CRC_Calc_Header(uint8_t dataValue, uint8_t crcValue)
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{
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uint16_t crc;
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crc = crcValue ^ dataValue; /* XOR C7..C0 with D7..D0 */
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/* Exclusive OR the terms in the table (top down) */
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crc = crc ^ (crc << 1) ^ (crc << 2) ^ (crc << 3)
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^ (crc << 4) ^ (crc << 5) ^ (crc << 6)
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^ (crc << 7);
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/* Combine bits shifted out left hand end */
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return (crc & 0xfe) ^ ((crc >> 8) & 1);
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}
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// Accumulate "dataValue" into the CRC in crcValue.
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// Return value is updated CRC
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//
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// The ^ operator means exclusive OR.
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// Note: This function is copied directly from the BACnet standard.
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uint16_t CRC_Calc_Data(uint8_t dataValue, uint16_t crcValue)
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{
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uint16_t crcLow;
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crcLow = (crcValue & 0xff) ^ dataValue; /* XOR C7..C0 with D7..D0 */
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/* Exclusive OR the terms in the table (top down) */
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return (crcValue >> 8) ^ (crcLow << 8) ^ (crcLow << 3)
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^ (crcLow << 12) ^ (crcLow >> 4)
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^ (crcLow & 0x0f) ^ ((crcLow & 0x0f) << 7);
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}
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#ifdef TEST
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#include <assert.h>
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#include <string.h>
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#include "ctest.h"
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#include "bytes.h"
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// test from Annex G 1.0 of BACnet Standard
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void testCRC8(Test * pTest)
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{
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uint8_t crc = 0xff; // accumulates the crc value
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uint8_t frame_crc; // appended to the end of the frame
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crc = CRC_Calc_Header(0x00, crc);
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ct_test(pTest, crc == 0x55);
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crc = CRC_Calc_Header(0x10, crc);
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ct_test(pTest, crc == 0xC2);
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crc = CRC_Calc_Header(0x05, crc);
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ct_test(pTest, crc == 0xBC);
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crc = CRC_Calc_Header(0x00, crc);
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ct_test(pTest, crc == 0x95);
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crc = CRC_Calc_Header(0x00, crc);
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ct_test(pTest, crc == 0x73);
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// send the ones complement of the CRC in place of
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// the CRC, and the resulting CRC will always equal 0x55.
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frame_crc = ~crc;
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ct_test(pTest, frame_crc == 0x8C);
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// use the ones complement value and the next to last CRC value
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crc = CRC_Calc_Header(frame_crc, crc);
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ct_test(pTest, crc == 0x55);
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}
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// test from Annex G 2.0 of BACnet Standard
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void testCRC16(Test * pTest)
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{
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uint16_t crc = 0xffff;
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uint16_t data_crc;
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crc = CRC_Calc_Data(0x01, crc);
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ct_test(pTest, crc == 0x1E0E);
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crc = CRC_Calc_Data(0x22, crc);
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ct_test(pTest, crc == 0xEB70);
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crc = CRC_Calc_Data(0x30, crc);
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ct_test(pTest, crc == 0x42EF);
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// send the ones complement of the CRC in place of
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// the CRC, and the resulting CRC will always equal 0xF0B8.
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data_crc = ~crc;
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ct_test(pTest, data_crc == 0xBD10);
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crc = CRC_Calc_Data(LO_BYTE(data_crc), crc);
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ct_test(pTest, crc == 0x0F3A);
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crc = CRC_Calc_Data(HI_BYTE(data_crc), crc);
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ct_test(pTest, crc == 0xF0B8);
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}
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#endif
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#ifdef TEST_CRC
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int main(void)
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{
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Test *pTest;
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bool rc;
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pTest = ct_create("crc", NULL);
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/* individual tests */
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rc = ct_addTestFunction(pTest, testCRC8);
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assert(rc);
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rc = ct_addTestFunction(pTest, testCRC16);
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assert(rc);
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ct_setStream(pTest, stdout);
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ct_run(pTest);
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(void) ct_report(pTest);
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ct_destroy(pTest);
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return 0;
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}
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#endif
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