of_ldpc_full_repair.c

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <of_openfec_api.h>

#define CHECK(expr) if (!(expr)) { fprintf(stderr, "CHECK failed: %s\n", #expr); exit(1); }

// these parameters allows us to repair *all* source packets
#define N_SOURCE 10
#define N_REPAIR 20

static char **encode_block(size_t payload_size) {
  of_session_t *of_inst = NULL;
  struct of_ldpc_parameters params = {};

  CHECK(OF_STATUS_OK == of_create_codec_instance(&of_inst,
                                                 OF_CODEC_LDPC_STAIRCASE_STABLE,
                                                 OF_ENCODER, 0));

  params.nb_source_symbols = N_SOURCE;
  params.nb_repair_symbols = N_REPAIR;
  params.encoding_symbol_length = payload_size;
  params.prng_seed = 1297501556;
  params.N1 = 7;

  CHECK(OF_STATUS_OK ==
        of_set_fec_parameters(of_inst, (of_parameters_t *)&params));

  char **encoded_block = calloc(N_SOURCE + N_REPAIR, sizeof(void *));
  unsigned i;

  // allocate source and repair packets
  for (i = 0; i < N_SOURCE + N_REPAIR; i++) {
    encoded_block[i] = calloc(payload_size, 1);
  }

  // fill source packets
  for (i = 0; i < N_SOURCE; i++) {
      memset(encoded_block[i], 0xcc, payload_size);
  }

  // build repair packets
  for (i = N_SOURCE; i < N_SOURCE + N_REPAIR; i++) {
    CHECK(OF_STATUS_OK ==
          of_build_repair_symbol(of_inst, (void **)encoded_block, i));
  }

  of_release_codec_instance(of_inst);

  return encoded_block;
}

static void full_repair(char **encoded_block, size_t payload_size) {
  of_session_t *of_inst = NULL;
  struct of_ldpc_parameters params = {};

  CHECK(OF_STATUS_OK == of_create_codec_instance(&of_inst,
                                                 OF_CODEC_LDPC_STAIRCASE_STABLE,
                                                 OF_DECODER, 0));

  params.nb_source_symbols = N_SOURCE;
  params.nb_repair_symbols = N_REPAIR;
  params.encoding_symbol_length = payload_size;
  params.prng_seed = 1297501556;
  params.N1 = 7;

  CHECK(OF_STATUS_OK ==
        of_set_fec_parameters(of_inst, (of_parameters_t *)&params));

  // pass repair packets to the decoder
  unsigned i;
  for (i = N_SOURCE; i < N_SOURCE + N_REPAIR; i++) {
    CHECK(OF_STATUS_OK == of_decode_with_new_symbol(of_inst, encoded_block[i], i));
  }
  CHECK(OF_STATUS_OK == of_finish_decoding(of_inst));

  // try to repair all source packets
  char **decoded_block = calloc(N_SOURCE + N_REPAIR, sizeof(void *));
  of_get_source_symbols_tab(of_inst, (void **)decoded_block);

  for (i = 0; i < N_SOURCE; i++) {
      CHECK(decoded_block[i] != NULL);
      CHECK(memcmp(encoded_block[i], decoded_block[i], payload_size) == 0);
  }

  of_release_codec_instance(of_inst);

  // free decoded packets
  for (i = 0; i < N_SOURCE; i++) {
      free(decoded_block[i]);
  }
  free(decoded_block);
}

static void release(char **encoded_block) {
  unsigned i;
  for (i = 0; i < N_SOURCE + N_REPAIR; i++) {
    free(encoded_block[i]);
  }
  free(encoded_block);
}

int main(int argc, char **argv) {
  CHECK(argc == 2);
  size_t payload_size = atoi(argv[1]);

  char **encoded_block = encode_block(payload_size);
  CHECK(encoded_block);

  printf("encoding done\n");

  full_repair(encoded_block, payload_size);

  printf("decoding done\n");

  release(encoded_block);

  return 0;
}