| #include <cstdlib>
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| #include <cstring>
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| #include <cmath>
|
| #include <cstdio>
|
| #include "stc_extract_c.h"
|
|
|
|
|
| int stc_extract(const u8 *vector, int vectorlength, u8 *message, int syndromelength, int matrixheight)
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| {
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| int i, j, k, index, index2, base, height;
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|
|
| u8 *binmat[2];
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| int *matrices, *widths;
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|
|
| height = matrixheight;
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|
|
| if(matrixheight > 31) {
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| fprintf(stderr, "Submatrix height must not exceed 31.");
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| return -1;
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| }
|
|
|
| {
|
| double invalpha;
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| int shorter, longer, worm;
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| u32 *columns[2];
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|
|
| matrices = (int *)malloc(syndromelength * sizeof(int));
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| widths = (int *)malloc(syndromelength * sizeof(int));
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|
|
| invalpha = (double)vectorlength / syndromelength;
|
| if(invalpha < 1) {
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| fprintf(stderr, "The message cannot be longer than the cover object.\n");
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| return -1;
|
| }
|
| shorter = (int)floor(invalpha);
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| longer = (int)ceil(invalpha);
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| if((columns[0] = getMatrix(shorter, matrixheight)) == NULL) {
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| free(widths);
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| free(matrices);
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| return -1;
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| }
|
| if((columns[1] = getMatrix(longer, matrixheight)) == NULL) {
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| free(columns[0]);
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| free(widths);
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| free(matrices);
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| return -1;
|
| }
|
| worm = 0;
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| for(i = 0; i < syndromelength; i++) {
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| if(worm + longer <= (i + 1) * invalpha + 0.5) {
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| matrices[i] = 1;
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| widths[i] = longer;
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| worm += longer;
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| } else {
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| matrices[i] = 0;
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| widths[i] = shorter;
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| worm += shorter;
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| }
|
| }
|
| binmat[0] = (u8*)malloc(shorter * matrixheight * sizeof(u8));
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| binmat[1] = (u8*)malloc(longer * matrixheight * sizeof(u8));
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| for(i = 0, index = 0; i < shorter; i++) {
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| for(j = 0; j < matrixheight; j++, index++) {
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| binmat[0][index] = (columns[0][i] & (1 << j)) ? 1 : 0;
|
| }
|
| }
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| for(i = 0, index = 0; i < longer; i++) {
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| for(j = 0; j < matrixheight; j++, index++) {
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| binmat[1][index] = (columns[1][i] & (1 << j)) ? 1 : 0;
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| }
|
| }
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| free(columns[0]);
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| free(columns[1]);
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| }
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|
|
| for(i = 0; i < syndromelength; i++) {
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| message[i] = 0;
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| }
|
|
|
| for(index = 0, index2 = 0; index2 < syndromelength; index2++) {
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| for(k = 0, base = 0; k < widths[index2]; k++, index++, base += matrixheight) {
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| if(vector[index]) {
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| for(i = 0; i < height; i++) {
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| message[index2 + i] ^= binmat[matrices[index2]][base + i];
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| }
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| }
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| }
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| if(syndromelength - index2 <= matrixheight)
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| height--;
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| }
|
|
|
| free(matrices);
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| free(widths);
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| free(binmat[0]);
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| free(binmat[1]);
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|
|
| return 0;
|
| }
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|
