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 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``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 AUTHORS
 * 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.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#define MSDOS /* LEAVE THIS IN PLACE EVEN ON UNIX! */

/*
 * compatibility stuff
 */
#ifdef MSDOS	/* but also for others, e.g. sun... */
#define NEED_BCOPY
#define bcmp(a,b,n) memcmp(a,b,n)
#endif

#ifdef NEED_BCOPY
#define bcopy(s, d, siz)        memcpy((d), (s), (siz))
#define bzero(d, siz)   memset((d), '\0', (siz))
#endif

/*
 * stuff used for testing purposes only
 */

#ifdef	TEST
#define DEB(x)
#define DDB(x) x
#define	DEBUG	0	/* minimal debugging */

#ifdef	MSDOS
#include <time.h>
struct timeval {
    unsigned long ticks;
};
#define gettimeofday(x, dummy) { (x)->ticks = clock() ; }
#define DIFF_T(a,b) (1+ 1000000*(a.ticks - b.ticks) / CLOCKS_PER_SEC )
typedef unsigned long u_long ;
typedef unsigned short u_short ;
#else /* typically, unix systems */
#include <sys/time.h>
#define DIFF_T(a,b) \
	(1+ 1000000*(a.tv_sec - b.tv_sec) + (a.tv_usec - b.tv_usec) )
#endif

#define TICK(t) \
	{struct timeval x ; \
	gettimeofday(&x, NULL) ; \
	t = x.tv_usec + 1000000* (x.tv_sec & 0xff ) ; \
	}
#define TOCK(t) \
	{ u_long t1 ; TICK(t1) ; \
	  if (t1 < t) t = 256000000 + t1 - t ; \
	  else t = t1 - t ; \
	  if (t == 0) t = 1 ;}
	
u_long ticks[10];	/* vars for timekeeping */
#else
#define DEB(x)
#define DDB(x)
#define TICK(x)
#define TOCK(x)
#endif /* TEST */

/*
 * You should not need to change anything beyond this point.
 * The first part of the file implements linear algebra in GF.
 *
 * gf is the type used to store an element of the Galois Field.
 * Must constain at least GF_BITS bits.
 *
 * Note: unsigned char will work up to GF(256) but int seems to run
 * faster on the Pentium. We use int whenever have to deal with an
 * index, since they are generally faster.
 */
#if (GF_BITS < 2  && GF_BITS >16)
#error "GF_BITS must be 2 .. 16"
#endif
#if (GF_BITS <= 8)
typedef uint8_t gf;
#else
typedef uint16_t gf;
#endif

#define	GF_SIZE ((1 << GF_BITS) - 1)	/* powers of \alpha */

/*
 * Primitive polynomials - see Lin & Costello, Appendix A,
 * and  Lee & Messerschmitt, p. 453.
 */
static char *allPp[] = {    /* GF_BITS	polynomial		*/
    NULL,		    /*  0	no code			*/
    NULL,		    /*  1	no code			*/
    "111",		    /*  2	1+x+x^2			*/
    "1101",		    /*  3	1+x+x^3			*/
    "11001",		    /*  4	1+x+x^4			*/
    "101001",		    /*  5	1+x^2+x^5		*/
    "1100001",		    /*  6	1+x+x^6			*/
    "10010001",		    /*  7	1 + x^3 + x^7		*/
    "101110001",	    /*  8	1+x^2+x^3+x^4+x^8	*/