galois.c 10.1 KB
/* Galois.c
 * James S. Plank

Jerasure - A C/C++ Library for a Variety of Reed-Solomon and RAID-6 Erasure Coding Techniques

Revision 1.2A
May 24, 2011

James S. Plank
Department of Electrical Engineering and Computer Science
University of Tennessee
Knoxville, TN 37996
plank@cs.utk.edu

Copyright (c) 2011, James S. Plank
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

 - Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.

 - 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.

 - Neither the name of the University of Tennessee nor the names of its
   contributors may be used to endorse or promote products derived
   from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"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 COPYRIGHT
HOLDER OR CONTRIBUTORS 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 "galois.h"

#define MAX_GF_INSTANCES 128
gf_t *gfp_array[MAX_GF_INSTANCES] = { 0 };

gf_t *galois_get_field_ptr(int w)
{
  if (gfp_array[w] != NULL) {
    return gfp_array[w];
  }

  return NULL;
}

int galois_init_base_field(int w,
                           int mult_type,
                           int region_type,
                           int divide_type,
                           uint64_t prim_poly,
                           int arg1,
                           int arg2)
{
  int scratch_size;
  void *scratch_memory;
  int ret;

  if (w <= 0 || w > 32) {
    fprintf(stderr, "ERROR -- cannot init default Galois field for w=%d\n", w);
    exit(1);
  }

  scratch_size = gf_scratch_size(w, mult_type, region_type, divide_type, arg1, arg2);
  if (!scratch_size) {
    fprintf(stderr, "ERROR -- cannot get scratch size for base field w=%d\n", w);
    exit(1);
  }

  scratch_memory = malloc(scratch_size);
  if (!scratch_memory) {
    fprintf(stderr, "ERROR -- cannot get scratch memory for base field w=%d\n", w);
    exit(1);
  }

  /*
   * Properly free up the old field
   */
  if (gfp_array[w] != NULL) {
    gf_free(gfp_array[w], 0); 
  }

  gfp_array[w] = (gf_t*)malloc(sizeof(gf_t));
  if (gfp_array[w] == NULL) {
    fprintf(stderr, "ERROR -- cannot allocate memory for Galois field w=%d\n", w);
    exit(1);
  }

  if(!gf_init_hard(gfp_array[w], 
                   w, 
                   mult_type, 
                   region_type, 
                   divide_type, 
                   prim_poly, 
                   arg1, 
                   arg2, 
                   NULL, 
                   scratch_memory))
  {
    fprintf(stderr, "ERROR -- cannot init default Galois field for w=%d\n", w);
    exit(1);
  }
  return 0;
}

int galois_init_composite_field(int w,
                                int region_type,
                                int divide_type,
                                uint64_t prim_poly,
                                int arg1,
                                int arg2,
                                gf_t* base_gf)
{
  int scratch_size;
  void *scratch_memory;
  int ret;
  
  if (w <= 0 || w > 32) {
    fprintf(stderr, "ERROR -- cannot init composite field for w=%d\n", w);
    exit(1);
  }

  scratch_size = gf_scratch_size(w, GF_MULT_COMPOSITE, region_type, divide_type, arg1, arg2);
  if (!scratch_size) {
    fprintf(stderr, "ERROR -- cannot get scratch size for composite field w=%d\n", w);
    exit(1);
  }

  scratch_memory = malloc(scratch_size);
  if (!scratch_memory) {
    fprintf(stderr, "ERROR -- cannot get scratch memory for composite field w=%d\n", w);
    exit(1);
  }

  /*
   * Properly free up the old field
   */
  if (gfp_array[w] != NULL) {
    gf_free(gfp_array[w], 1);
  }

  gfp_array[w] = (gf_t*)malloc(sizeof(gf_t));
  if (gfp_array[w] == NULL) {
    fprintf(stderr, "ERROR -- cannot allocate memory for composite field w=%d\n", w);
    exit(1);
  }

  if(!gf_init_hard(gfp_array[w],
                   w,
                   GF_MULT_COMPOSITE,
                   region_type,
                   divide_type,
                   prim_poly,
                   arg1,
                   arg2,
                   base_gf,
                   scratch_memory))
  {
    fprintf(stderr, "ERROR -- cannot init default composite field for w=%d\n", w);
    exit(1);
  }
  return 0;
}

static void galois_init_default_field(int w)
{
  if (w <= 0 || w > 32) {
    fprintf(stderr, "ERROR -- cannot init default Galois field for w=%d\n", w);
    exit(1);
  }

  if (gfp_array[w] == NULL) {
    gfp_array[w] = (gf_t*)malloc(sizeof(gf_t));
    if (gfp_array[w] == NULL) {
      fprintf(stderr, "ERROR -- cannot allocate memory for Galois field w=%d\n", w);
      exit(1);
    }
  }

  if (w == 16) {
    if (!gf_init_hard(gfp_array[w], w, GF_MULT_SPLIT_TABLE, GF_REGION_ALTMAP, GF_DIVIDE_DEFAULT, 0, 16, 4, NULL, NULL)) {
      fprintf(stderr, "ERROR -- cannot init default Galois field for w=%d\n", w);
      exit(1); 
    }
  }

  if (!gf_init_easy(gfp_array[w], w)) {
    fprintf(stderr, "ERROR -- cannot init default Galois field for w=%d\n", w);
    exit(1);
  }
}


static int is_valid_gf(gf_t *gf, int w)
{
  // TODO: I assume we may eventually
  // want to do w=64 and 128, so w
  // will be needed to perform this check
  (void)w;

  if (gf == NULL) {
    return 0;
  }
  if (gf->multiply.w32 == NULL) {
    return 0;
  }
  if (gf->multiply_region.w32 == NULL) {
    return 0;
  }
  if (gf->divide.w32 == NULL) {
    return 0;
  }
  if (gf->inverse.w32 == NULL) {
    return 0;
  }
  if (gf->extract_word.w32 == NULL) {
    return 0;
  }

  return 1;
}

void galois_change_technique(gf_t *gf, int w)
{
  if (w <= 0 || w > 32) {
    fprintf(stderr, "ERROR -- cannot support Galois field for w=%d\n", w);
    exit(1);
  }

  if (!is_valid_gf(gf, w)) {
    fprintf(stderr, "ERROR -- overriding with invalid Galois field for w=%d\n", w);
    exit(1);
  }

  gfp_array[w] = gf;
}

int galois_single_multiply(int x, int y, int w)
{
  if (x == 0 || y == 0) return 0;
  
  if (gfp_array[w] == NULL) {
    galois_init_default_field(w);
  }

  if (w <= 32) {
    return gfp_array[w]->multiply.w32(gfp_array[w], x, y);
  } else {
    fprintf(stderr, "ERROR -- Galois field not implemented for w=%d\n", w);
  }
}

int galois_single_divide(int x, int y, int w)
{
  if (x == 0) return 0;
  if (y == 0) return -1;

  if (gfp_array[w] == NULL) {
    galois_init_default_field(w);
  }

  if (w <= 32) {
    return gfp_array[w]->divide.w32(gfp_array[w], x, y);
  } else {
    fprintf(stderr, "ERROR -- Galois field not implemented for w=%d\n", w);
  }
}

void galois_w08_region_multiply(char *region,      /* Region to multiply */
                                  int multby,       /* Number to multiply by */
                                  int nbytes,        /* Number of bytes in region */
                                  char *r2,          /* If r2 != NULL, products go here */
                                  int add)
{
  if (gfp_array[8] == NULL) {
    galois_init_default_field(8);
  }
  gfp_array[8]->multiply_region.w32(gfp_array[8], region, r2, multby, nbytes, add);
}

void galois_w16_region_multiply(char *region,      /* Region to multiply */
                                  int multby,       /* Number to multiply by */
                                  int nbytes,        /* Number of bytes in region */
                                  char *r2,          /* If r2 != NULL, products go here */
                                  int add)
{
  if (gfp_array[16] == NULL) {
    galois_init_default_field(16);
  }
  gfp_array[16]->multiply_region.w32(gfp_array[16], region, r2, multby, nbytes, add);
}


void galois_w32_region_multiply(char *region,      /* Region to multiply */
                                  int multby,       /* Number to multiply by */
                                  int nbytes,        /* Number of bytes in region */
                                  char *r2,          /* If r2 != NULL, products go here */
                                  int add)
{
  if (gfp_array[32] == NULL) {
    galois_init_default_field(32);
  }
  gfp_array[32]->multiply_region.w32(gfp_array[32], region, r2, multby, nbytes, add);
}

void galois_w8_region_xor(void *src, void *dest, int nbytes)
{
  if (gfp_array[8] == NULL) {
    galois_init_default_field(8);
  }
  gfp_array[8]->multiply_region.w32(gfp_array[32], src, dest, 1, nbytes, 1);
}

void galois_w16_region_xor(void *src, void *dest, int nbytes)
{
  if (gfp_array[16] == NULL) {
    galois_init_default_field(16);
  }
  gfp_array[16]->multiply_region.w32(gfp_array[16], src, dest, 1, nbytes, 1);
}

void galois_w32_region_xor(void *src, void *dest, int nbytes)
{
  if (gfp_array[32] == NULL) {
    galois_init_default_field(32);
  }
  gfp_array[32]->multiply_region.w32(gfp_array[32], src, dest, 1, nbytes, 1);
}

void galois_region_xor(char *r1,         /* Region 1 */
                            char *r2,         /* Region 2 */
                            char *r3,         /* Sum region (r3 = r1 ^ r2) -- can be r1 or r2 */
                            int nbytes)       /* Number of bytes in region */
{
  long *l1;
  long *l2;
  long *l3;
  long *ltop;
  char *ctop;
  
  ctop = r1 + nbytes;
  ltop = (long *) ctop;
  l1 = (long *) r1;
  l2 = (long *) r2;
  l3 = (long *) r3;
 
  while (l1 < ltop) {
    *l3 = ((*l1)  ^ (*l2));
    l1++;
    l2++;
    l3++;
  }
}

int galois_inverse(int y, int w)
{
  if (y == 0) return -1;
  return galois_single_divide(1, y, w);
}