101 lines
1.8 KiB
C
101 lines
1.8 KiB
C
/*
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* Cisco router simulation platform.
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* Copyright (c) 2006 Christophe Fillot (cf@utc.fr)
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*
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* CRC functions.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/mman.h>
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#include <signal.h>
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#include <fcntl.h>
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#include <assert.h>
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#include "utils.h"
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#include "crc.h"
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#define CRC12_POLY 0x0f01
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#define CRC16_POLY 0xa001
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#define CRC32_POLY 0xedb88320L
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/* CRC tables */
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m_uint16_t crc12_array[256], crc16_array[256];
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m_uint32_t crc32_array[256];
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/* Initialize CRC-12 algorithm */
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static void crc12_init (void)
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{
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m_uint16_t crc, c;
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int i, j;
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for (i = 0; i < 256; i++) {
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crc = 0;
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c = (m_uint16_t) i;
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for (j = 0; j < 8; j++) {
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if ((crc ^ c) & 0x0001)
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crc = (crc >> 1) ^ CRC12_POLY;
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else
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crc = crc >> 1;
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c = c >> 1;
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}
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crc12_array[i] = crc;
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}
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}
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/* Initialize CRC-16 algorithm */
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static void crc16_init (void)
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{
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m_uint16_t crc, c;
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int i, j;
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for (i = 0; i < 256; i++) {
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crc = 0;
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c = (m_uint16_t) i;
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for (j = 0; j < 8; j++) {
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if ((crc ^ c) & 0x0001)
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crc = (crc >> 1) ^ CRC16_POLY;
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else
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crc = crc >> 1;
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c = c >> 1;
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}
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crc16_array[i] = crc;
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}
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}
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/* Initialize CRC-32 algorithm */
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static void crc32_init (void)
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{
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unsigned long c;
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int n, k;
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for (n = 0; n < 256; n++) {
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c = (unsigned long) n;
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for (k = 0; k < 8; k++) {
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if (c & 1)
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c = CRC32_POLY ^ (c >> 1);
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else
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c = c >> 1;
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}
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crc32_array[n] = c;
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}
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}
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/* Initialize CRC algorithms */
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void crc_init (void)
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{
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crc12_init ();
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crc16_init ();
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crc32_init ();
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}
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