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mktables.c

#ident "$Id: mktables.c,v 1.2 2002/12/12 22:41:27 hpa Exp $"
/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2002 H. Peter Anvin - All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
 *   Bostom MA 02111-1307, USA; either version 2 of the License, or
 *   (at your option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * mktables.c
 *
 * Make RAID-6 tables.  This is a host user space program to be run at
 * compile time.
 */

#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <stdlib.h>
#include <time.h>

static uint8_t gfmul(uint8_t a, uint8_t b)
{
  uint8_t v = 0;

  while ( b ) {
    if ( b & 1 ) v ^= a;
    a = (a << 1) ^ (a & 0x80 ? 0x1d : 0);
    b >>= 1;
  }
  return v;
}

static uint8_t gfpow(uint8_t a, int b)
{
  uint8_t v = 1;

  b %= 255;
  if ( b < 0 )
    b += 255;

  while ( b ) {
    if ( b & 1 ) v = gfmul(v,a);
    a = gfmul(a,a);
    b >>= 1;
  }
  return v;
}

int main(int argc, char *argv[])
{
  int i, j, k;
  uint8_t v;
  uint8_t exptbl[256], invtbl[256];

  printf("#include \"raid6.h\"\n");

  /* Compute multiplication table */
  printf("\nconst u8  __attribute__((aligned(256)))\n"
       "raid6_gfmul[256][256] =\n"
       "{\n");
  for ( i = 0 ; i < 256 ; i++ ) {
    printf("\t{\n");
    for ( j = 0 ; j < 256 ; j += 8 ) {
      printf("\t\t");
      for ( k = 0 ; k < 8 ; k++ ) {
      printf("0x%02x, ", gfmul(i,j+k));
      }
      printf("\n");
    }
    printf("\t},\n");
  }
  printf("};\n");

  /* Compute power-of-2 table (exponent) */
  v = 1;
  printf("\nconst u8 __attribute__((aligned(256)))\n"
       "raid6_gfexp[256] =\n"
       "{\n");
  for ( i = 0 ; i < 256 ; i += 8 ) {
    printf("\t");
    for ( j = 0 ; j < 8 ; j++ ) {
      exptbl[i+j] = v;
      printf("0x%02x, ", v);
      v = gfmul(v,2);
      if ( v == 1 ) v = 0;    /* For entry 255, not a real entry */
    }
    printf("\n");
  }
  printf("};\n");

  /* Compute inverse table x^-1 == x^254 */
  printf("\nconst u8 __attribute__((aligned(256)))\n"
       "raid6_gfinv[256] =\n"
       "{\n");
  for ( i = 0 ; i < 256 ; i += 8 ) {
    printf("\t");
    for ( j = 0 ; j < 8 ; j++ ) {
      invtbl[i+j] = v = gfpow(i+j,254);
      printf("0x%02x, ", v);
    }
    printf("\n");
  }
  printf("};\n");

  /* Compute inv(2^x + 1) (exponent-xor-inverse) table */
  printf("\nconst u8 __attribute__((aligned(256)))\n"
       "raid6_gfexi[256] =\n"
       "{\n");
  for ( i = 0 ; i < 256 ; i += 8 ) {
    printf("\t");
    for ( j = 0 ; j < 8 ; j++ ) {
      printf("0x%02x, ", invtbl[exptbl[i+j]^1]);
    }
    printf("\n");
  }
  printf("};\n\n");

  return 0;
}

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