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120 lines
3.9 KiB
C
120 lines
3.9 KiB
C
#include <string.h>
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#include <stdint.h>
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#include <stdio.h>
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#include "erasure_code.h"
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#define MAX_CHECK 63 /* Size is limited by using uint64_t to represent subsets */
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#define M_MAX 0x20
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#define K_MAX 0x10
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#define ROWS M_MAX
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#define COLS K_MAX
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static inline uint64_t
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min(const uint64_t a, const uint64_t b)
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{
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if (a <= b)
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return a;
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else
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return b;
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}
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void
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gen_sub_matrix(unsigned char *out_matrix, const uint64_t dim, unsigned char *in_matrix,
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const uint64_t rows, const uint64_t cols, const uint64_t row_indicator,
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const uint64_t col_indicator)
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{
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uint64_t i, j, r, s;
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for (i = 0, r = 0; i < rows; i++) {
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if (!(row_indicator & ((uint64_t) 1 << i)))
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continue;
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for (j = 0, s = 0; j < cols; j++) {
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if (!(col_indicator & ((uint64_t) 1 << j)))
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continue;
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out_matrix[dim * r + s] = in_matrix[cols * i + j];
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s++;
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}
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r++;
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}
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}
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/* Gosper's Hack */
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uint64_t
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next_subset(uint64_t *subset, uint64_t element_count, uint64_t subsize)
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{
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uint64_t tmp1 = *subset & -*subset;
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uint64_t tmp2 = *subset + tmp1;
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*subset = (((*subset ^ tmp2) >> 2) / tmp1) | tmp2;
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if (*subset & (((uint64_t) 1 << element_count))) {
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/* Overflow on last subset */
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*subset = ((uint64_t) 1 << subsize) - 1;
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return 1;
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}
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return 0;
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}
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int
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are_submatrices_singular(unsigned char *vmatrix, const uint64_t rows, const uint64_t cols)
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{
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unsigned char matrix[COLS * COLS];
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unsigned char invert_matrix[COLS * COLS];
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uint64_t subsize;
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/* Check all square subsize x subsize submatrices of the rows x cols
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* vmatrix for singularity*/
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for (subsize = 1; subsize <= min(rows, cols); subsize++) {
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const uint64_t subset_init = (1ULL << subsize) - 1ULL;
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uint64_t col_indicator = subset_init;
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do {
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uint64_t row_indicator = subset_init;
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do {
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gen_sub_matrix(matrix, subsize, vmatrix, rows, cols, row_indicator,
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col_indicator);
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if (gf_invert_matrix(matrix, invert_matrix, (int) subsize))
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return 1;
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} while (next_subset(&row_indicator, rows, subsize) == 0);
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} while (next_subset(&col_indicator, cols, subsize) == 0);
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}
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return 0;
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}
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int
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main(int argc, char **argv)
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{
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unsigned char vmatrix[(ROWS + COLS) * COLS];
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uint64_t rows, cols;
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if (K_MAX > MAX_CHECK) {
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printf("K_MAX too large for this test\n");
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return 0;
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}
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if (M_MAX > MAX_CHECK) {
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printf("M_MAX too large for this test\n");
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return 0;
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}
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if (M_MAX < K_MAX) {
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printf("M_MAX must be smaller than K_MAX");
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return 0;
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}
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printf("Checking gen_rs_matrix for k <= %d and m <= %d.\n", K_MAX, M_MAX);
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printf("gen_rs_matrix creates erasure codes for:\n");
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for (cols = 1; cols <= K_MAX; cols++) {
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for (rows = 1; rows <= M_MAX - cols; rows++) {
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gf_gen_rs_matrix(vmatrix, rows + cols, cols);
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/* Verify the Vandermonde portion of vmatrix contains no
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* singular submatrix */
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if (are_submatrices_singular(&vmatrix[cols * cols], rows, cols))
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break;
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}
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printf(" k = %2u, m <= %2u \n", (unsigned) cols, (unsigned) (rows + cols - 1));
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}
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return 0;
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}
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