ec_simple_example.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include "erasure_code.h" // use <isa-l.h> instead when linking against installed

#define MMAX 255
#define KMAX 255

typedef unsigned char u8;

int
usage(void)
{
        fprintf(stderr,
                "Usage: ec_simple_example [options]\n"
                "  -h        Help\n"
                "  -k <val>  Number of source fragments\n"
                "  -p <val>  Number of parity fragments\n"
                "  -l <val>  Length of fragments\n"
                "  -e <val>  Simulate erasure on frag index val. Zero based. Can be repeated.\n"
                "  -r <seed> Pick random (k, p) with seed\n");
        exit(0);
}

static int
gf_gen_decode_matrix_simple(u8 *encode_matrix, u8 *decode_matrix, u8 *invert_matrix,
                            u8 *temp_matrix, u8 *decode_index, u8 *frag_err_list, int nerrs, int k,
                            int m);

int
main(int argc, char *argv[])
{
        int i, j, m, c, e, ret;
        int k = 10, p = 4, len = 8 * 1024; // Default params
        int nerrs = 0;

        // Fragment buffer pointers
        u8 *frag_ptrs[MMAX];
        u8 *recover_srcs[KMAX];
        u8 *recover_outp[KMAX];
        u8 frag_err_list[MMAX];

        // Coefficient matrices
        u8 *encode_matrix, *decode_matrix;
        u8 *invert_matrix, *temp_matrix;
        u8 *g_tbls;
        u8 decode_index[MMAX];

        if (argc == 1)
                for (i = 0; i < p; i++)
                        frag_err_list[nerrs++] = rand() % (k + p);

        while ((c = getopt(argc, argv, "k:p:l:e:r:h")) != -1) {
                switch (c) {
                case 'k':
                        k = atoi(optarg);
                        break;
                case 'p':
                        p = atoi(optarg);
                        break;
                case 'l':
                        len = atoi(optarg);
                        if (len < 0)
                                usage();
                        break;
                case 'e':
                        e = atoi(optarg);
                        frag_err_list[nerrs++] = e;
                        break;
                case 'r':
                        srand(atoi(optarg));
                        k = (rand() % (MMAX - 1)) + 1; // Pick k {1 to MMAX - 1}
                        p = (rand() % (MMAX - k)) + 1; // Pick p {1 to MMAX - k}

                        for (i = 0; i < k + p && nerrs < p; i++)
                                if (rand() & 1)
                                        frag_err_list[nerrs++] = i;
                        break;
                case 'h':
                default:
                        usage();
                        break;
                }
        }
        m = k + p;

        // Check for valid parameters
        if (m > MMAX || k > KMAX || m < 0 || p < 1 || k < 1) {
                printf(" Input test parameter error m=%d, k=%d, p=%d, erasures=%d\n", m, k, p,
                       nerrs);
                usage();
        }
        if (nerrs > p) {
                printf(" Number of erasures chosen exceeds power of code erasures=%d p=%d\n", nerrs,
                       p);
                usage();
        }
        for (i = 0; i < nerrs; i++) {
                if (frag_err_list[i] >= m) {
                        printf(" fragment %d not in range\n", frag_err_list[i]);
                        usage();
                }
        }

        printf("ec_simple_example:\n");

        // Allocate coding matrices
        encode_matrix = malloc(m * k);
        decode_matrix = malloc(m * k);
        invert_matrix = malloc(m * k);
        temp_matrix = malloc(m * k);
        g_tbls = malloc(k * p * 32);

        if (encode_matrix == NULL || decode_matrix == NULL || invert_matrix == NULL ||
            temp_matrix == NULL || g_tbls == NULL) {
                printf("Test failure! Error with malloc\n");
                return -1;
        }
        // Allocate the src & parity buffers
        for (i = 0; i < m; i++) {
                if (NULL == (frag_ptrs[i] = malloc(len))) {
                        printf("alloc error: Fail\n");
                        return -1;
                }
        }

        // Allocate buffers for recovered data
        for (i = 0; i < p; i++) {
                if (NULL == (recover_outp[i] = malloc(len))) {
                        printf("alloc error: Fail\n");
                        return -1;
                }
        }

        // Fill sources with random data
        for (i = 0; i < k; i++)
                for (j = 0; j < len; j++)
                        frag_ptrs[i][j] = rand();

        printf(" encode (m,k,p)=(%d,%d,%d) len=%d\n", m, k, p, len);

        // Pick an encode matrix. A Cauchy matrix is a good choice as even
        // large k are always invertable keeping the recovery rule simple.
        gf_gen_cauchy1_matrix(encode_matrix, m, k);

        // Initialize g_tbls from encode matrix
        ec_init_tables(k, p, &encode_matrix[k * k], g_tbls);

        // Generate EC parity blocks from sources
        ec_encode_data(len, k, p, g_tbls, frag_ptrs, &frag_ptrs[k]);

        if (nerrs <= 0)
                return 0;

        printf(" recover %d fragments\n", nerrs);

        // Find a decode matrix to regenerate all erasures from remaining frags
        ret = gf_gen_decode_matrix_simple(encode_matrix, decode_matrix, invert_matrix, temp_matrix,
                                          decode_index, frag_err_list, nerrs, k, m);
        if (ret != 0) {
                printf("Fail on generate decode matrix\n");
                return -1;
        }
        // Pack recovery array pointers as list of valid fragments
        for (i = 0; i < k; i++)
                recover_srcs[i] = frag_ptrs[decode_index[i]];

        // Recover data
        ec_init_tables(k, nerrs, decode_matrix, g_tbls);
        ec_encode_data(len, k, nerrs, g_tbls, recover_srcs, recover_outp);

        // Check that recovered buffers are the same as original
        printf(" check recovery of block {");
        for (i = 0; i < nerrs; i++) {
                printf(" %d", frag_err_list[i]);
                if (memcmp(recover_outp[i], frag_ptrs[frag_err_list[i]], len)) {
                        printf(" Fail erasure recovery %d, frag %d\n", i, frag_err_list[i]);
                        return -1;
                }
        }

        printf(" } done all: Pass\n");
        return 0;
}

/*
 * Generate decode matrix from encode matrix and erasure list
 *
 */

static int
gf_gen_decode_matrix_simple(u8 *encode_matrix, u8 *decode_matrix, u8 *invert_matrix,
                            u8 *temp_matrix, u8 *decode_index, u8 *frag_err_list, int nerrs, int k,
                            int m)
{
        int i, j, p, r;
        int nsrcerrs = 0;
        u8 s, *b = temp_matrix;
        u8 frag_in_err[MMAX];

        memset(frag_in_err, 0, sizeof(frag_in_err));

        // Order the fragments in erasure for easier sorting
        for (i = 0; i < nerrs; i++) {
                if (frag_err_list[i] < k)
                        nsrcerrs++;
                frag_in_err[frag_err_list[i]] = 1;
        }

        // Construct b (matrix that encoded remaining frags) by removing erased rows
        for (i = 0, r = 0; i < k; i++, r++) {
                while (frag_in_err[r])
                        r++;
                for (j = 0; j < k; j++)
                        b[k * i + j] = encode_matrix[k * r + j];
                decode_index[i] = r;
        }

        // Invert matrix to get recovery matrix
        if (gf_invert_matrix(b, invert_matrix, k) < 0)
                return -1;

        // Get decode matrix with only wanted recovery rows
        for (i = 0; i < nerrs; i++) {
                if (frag_err_list[i] < k) // A src err
                        for (j = 0; j < k; j++)
                                decode_matrix[k * i + j] = invert_matrix[k * frag_err_list[i] + j];
        }

        // For non-src (parity) erasures need to multiply encode matrix * invert
        for (p = 0; p < nerrs; p++) {
                if (frag_err_list[p] >= k) { // A parity err
                        for (i = 0; i < k; i++) {
                                s = 0;
                                for (j = 0; j < k; j++)
                                        s ^= gf_mul(invert_matrix[j * k + i],
                                                    encode_matrix[k * frag_err_list[p] + j]);
                                decode_matrix[k * p + i] = s;
                        }
                }
        }
        return 0;
}