/*
 * Cisco router simulation platform.
 * Copyright (c) 2006 Christophe Fillot (cf@utc.fr)
 *
 * CRC functions.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <signal.h>
#include <fcntl.h>
#include <assert.h>

#include "utils.h"
#include "crc.h"

#define CRC12_POLY  0x0f01
#define CRC16_POLY  0xa001
#define CRC32_POLY  0xedb88320L

/* CRC tables */
m_uint16_t crc12_array[256], crc16_array[256];
m_uint32_t crc32_array[256];

/* Initialize CRC-12 algorithm */
static void crc12_init (void)
{
    m_uint16_t crc, c;
    int i, j;

    for (i = 0; i < 256; i++) {
        crc = 0;
        c = (m_uint16_t) i;

        for (j = 0; j < 8; j++) {
            if ((crc ^ c) & 0x0001)
                crc = (crc >> 1) ^ CRC12_POLY;
            else
                crc = crc >> 1;

            c = c >> 1;
        }

        crc12_array[i] = crc;
    }
}

/* Initialize CRC-16 algorithm */
static void crc16_init (void)
{
    m_uint16_t crc, c;
    int i, j;

    for (i = 0; i < 256; i++) {
        crc = 0;
        c = (m_uint16_t) i;

        for (j = 0; j < 8; j++) {
            if ((crc ^ c) & 0x0001)
                crc = (crc >> 1) ^ CRC16_POLY;
            else
                crc = crc >> 1;

            c = c >> 1;
        }

        crc16_array[i] = crc;
    }
}

/* Initialize CRC-32 algorithm */
static void crc32_init (void)
{
    unsigned long c;
    int n, k;

    for (n = 0; n < 256; n++) {
        c = (unsigned long) n;
        for (k = 0; k < 8; k++) {
            if (c & 1)
                c = CRC32_POLY ^ (c >> 1);
            else
                c = c >> 1;
        }
        crc32_array[n] = c;
    }
}

/* Initialize CRC algorithms */
void crc_init (void)
{
    crc12_init ();
    crc16_init ();
    crc32_init ();
}