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minio/pkgs/erasure/decode.c

147 lines
5.2 KiB

/*
* Mini Object Storage, (C) 2014 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <erasure-code.h>
#include "common.h"
int32_t minio_src_in_err (int r, int *src_err_list)
{
int i;
for (i = 0; src_err_list[i] != -1; i++) {
if (src_err_list[i] == r) {
// true
return 1;
}
}
// false
return 0;
}
int32_t minio_get_source_target(int *src_err_list,
int errs, int k, int m,
unsigned char **data,
unsigned char **coding,
unsigned char ***source,
unsigned char ***target)
{
int i, j, l;
unsigned char *tmp_source[k];
unsigned char *tmp_target[m];
// Fill zeroes
memset (tmp_source, 0, sizeof(tmp_source));
memset (tmp_target, 0, sizeof(tmp_target));
// Separate out source and target buffers from input data/coding chunks
// This separation needs to happen at error chunks from input chunks
for (i = 0, j = 0, l = 0;
((l < k) || (j < errs)) && (i < (k + m)); i++) {
if (!minio_src_in_err(i, src_err_list)) {
if (l < k) {
if (i < k)
tmp_source[l] =
(unsigned char *) data[i];
else
tmp_source[l] =
(unsigned char *) coding[i - k];
l++;
}
} else {
if (j < m) {
if (i < k)
tmp_target[j] =
(unsigned char *) data[i];
else
tmp_target[j] =
(unsigned char *) coding[i - k];
j++;
}
}
}
*source = tmp_source;
*target = tmp_target;
}
/*
Generate decode matrix during the decoding phase
*/
int minio_init_decoder (int *src_err_list,
unsigned char *encode_matrix,
unsigned char **decode_matrix,
unsigned char **decode_tbls,
int k, int n, int errs)
{
int i, j, r, s, l, z;
unsigned char input_matrix[k * n];
unsigned char inverse_matrix[k * n];
unsigned char *tmp_decode_matrix;
unsigned char *tmp_decode_tbls;
tmp_decode_matrix = (unsigned char *) malloc (k * n);
if (!tmp_decode_matrix)
return -1;
tmp_decode_tbls = (unsigned char *) malloc (k * n * 32);
if (!tmp_decode_tbls)
return -1;
for (i = 0, r = 0; i < k; i++, r++) {
while (minio_src_in_err(r, src_err_list))
r++;
for (j = 0; j < k; j++) {
input_matrix[k * i + j] = encode_matrix[k * r + j];
}
}
// Not all Vandermonde matrix can be inverted
if (gf_invert_matrix(input_matrix, inverse_matrix, k) < 0) {
return -1;
}
for (l = 0; l < errs; l++) {
if (src_err_list[l] < k) {
// decoding matrix elements for data chunks
for (j = 0; j < k; j++) {
tmp_decode_matrix[k * l + j] =
inverse_matrix[k *
src_err_list[l] + j];
}
} else {
int s = 0;
// decoding matrix element for coding chunks
for (i = 0; i < k; i++) {
s = 0;
for (j = 0; j < k; j++) {
s ^= gf_mul(inverse_matrix[j * k + i],
encode_matrix[k *
src_err_list[l] + j]);
}
tmp_decode_matrix[k * l + i] = s;
}
}
}
ec_init_tables(k, errs, tmp_decode_matrix, tmp_decode_tbls);
*decode_matrix = tmp_decode_matrix;
*decode_tbls = tmp_decode_tbls;
return 0;
}