find_the_bug.c

// cache

// use segment address to send file, make segment available for other threads right after exit
// the error is in this function
int send_file_through_shm(cache_thread_ctx *ctx) {
  long maxBytesToRead = ctx->seg_size - 1;
  long n_loops = ctx->file_size / maxBytesToRead;
  n_loops += (ctx->file_size % maxBytesToRead) == 0 ? 0 : 1;
  long res = 0;

  for (long i = 0, offset = 0; i < n_loops; i++) {
    sem_wait(ctx->sem_write);

    if ((res = pread(ctx->fd, ctx->seg_addr, maxBytesToRead, offset)) < 0) {
      perror("pread:");
      return -1;
    }
    ctx->seg_addr[res] = '\0';
    offset += res;
    sem_post(ctx->sem_read);
  }
  
  return 0;
}

// proxy
// receiving function, just for the context
ssize_t recv_file(gfcontext_t *ctx, thread_ctx *thr_ctx, mq_resp_msg *response) {
  long segsize = thr_ctx->system_resources->segsize;
  long file_size = response->file_size;
  char *addr = thr_ctx->system_resources->segments_pool[response->segment_id].seg_addr;
  sem_t *sem_read = thr_ctx->system_resources->segments_pool[response->segment_id].sem_read;
  sem_t *sem_write = thr_ctx->system_resources->segments_pool[response->segment_id].sem_write;

  long bytes_transferred = 0;
  long bytes_sent = 0;
  
  while(bytes_transferred < file_size){
    sem_wait(sem_read);
    long left_to_transfer = file_size - bytes_transferred;
    long bytes_to_send = left_to_transfer >= segsize ? segsize - 1 : left_to_transfer;

    bytes_sent = gfs_send(ctx, addr,bytes_to_send);
    if (bytes_sent != bytes_to_send){
      sem_post(sem_write);
      fprintf(stderr, "handle_with_file write error");
      return SERVER_FAILURE;
    }

    bytes_transferred += bytes_sent;
    sem_post(sem_write);
  }
  return bytes_transferred;
}