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minio/pkg/encoding/erasure/ec-decode.c

134 lines
4.2 KiB

/*
* Minimalist 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 "ec-code.h"
#include "ec-common.h"
static
int32_t _minio_src_index_in_error (int r, int32_t *error_index)
{
int i;
for (i = 0; error_index[i] != -1; i++) {
if (error_index[i] == r) {
// true
return 1;
}
}
// false
return 0;
}
// Separate out source data and target buffers
int32_t minio_get_source_target (int errs, int k, int m,
int32_t *error_index,
uint32_t *decode_index,
uint8_t **buffs,
uint8_t ***source,
uint8_t ***target)
{
int i;
uint8_t *tmp_source[k];
uint8_t *tmp_target[m];
if (k < 0 || m < 0) {
return -1;
}
memset (tmp_source, 0, k);
memset (tmp_target, 0, m);
for (i = 0; i < k; i++) {
tmp_source[i] = (uint8_t *) buffs[decode_index[i]];
}
for (i = 0; i < m; i++) {
if (i < errs)
tmp_target[i] = (uint8_t *) buffs[error_index[i]];
}
*source = tmp_source;
*target = tmp_target;
return 0;
}
/*
Generate decode matrix during the decoding phase
*/
int minio_init_decoder (int32_t *error_index,
int k, int n, int errs,
uint8_t *encode_matrix,
uint8_t **decode_matrix,
uint8_t **decode_tbls,
uint32_t **decode_index)
{
int i, j, r, s, l, z;
uint8_t input_matrix[k * n];
uint8_t inverse_matrix[k * n];
uint8_t tmp_decode_matrix[k * n];
uint8_t tmp_decode_tbls[k * n * 32];
uint32_t tmp_decode_index[k];
for (i = 0, r = 0; i < k; i++, r++) {
while (_minio_src_index_in_error(r, error_index))
r++;
for (j = 0; j < k; j++) {
input_matrix[k * i + j] = encode_matrix[k * r + j];
}
tmp_decode_index[i] = r;
}
// 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 (error_index[l] < k) {
// decoding matrix elements for data chunks
for (j = 0; j < k; j++) {
tmp_decode_matrix[k * l + j] =
inverse_matrix[k *
error_index[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 *
error_index[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;
*decode_index = tmp_decode_index;
return 0;
}