text: /* nbdkit
   * Copyright (C) 2017-2020 Red Hat Inc.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   * * Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *
   * * Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution.
   *
   * * Neither the name of Red Hat nor the names of its contributors may be
   * used to endorse or promote products derived from this software without
   * specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
   * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  #include <config.h>
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <stdint.h>
  #include <inttypes.h>
  #include <string.h>
  #include <unistd.h>
  #include <time.h>
  
  #include <libnbd.h>
  
  #include "random.h"
  
  #define SIZE 1024*1024
  static char data[SIZE];
  
  static unsigned histogram[256];
  
  /* After reading the whole disk above, we then read randomly selected
   * subsets of the disk and compare the data (it should be identical).
   */
  #define RSIZE 10240
  #define NR_READS 50
  static char rdata[RSIZE];
  
  int
  main (int argc, char *argv[])
  {
    struct nbd_handle *nbd;
    struct random_state random_state;
    int i;
    unsigned offset;
    char sizearg[32];
  
    nbd = nbd_create ();
    if (nbd == NULL) {
      fprintf (stderr, "%s\n", nbd_get_error ());
      exit (EXIT_FAILURE);
    }
  
    snprintf (sizearg, sizeof sizearg, "%d", SIZE);
    if (nbd_connect_command (nbd,
                             (char *[]) {
                               "nbdkit", "-s", "--exit-with-parent",
                               "random", sizearg,
                               NULL }) == -1) {
      fprintf (stderr, "%s\n", nbd_get_error ());
      exit (EXIT_FAILURE);
    }
  
    /* Read the whole device. */
    if (nbd_pread (nbd, data, sizeof data, 0, 0) == -1) {
      fprintf (stderr, "%s\n", nbd_get_error ());
      exit (EXIT_FAILURE);
    }
  
    /* Test that the data is sufficiently random using a simple
     * histogram.  This just tests for gross errors and is not a
     * complete statistical study.
     */
    for (i = 0; i < SIZE; ++i) {
      unsigned char c = (unsigned char) data[i];
      histogram[c]++;
    }
    for (i = 0; i < 256; ++i) {
      const unsigned expected = SIZE / 256;
      if (histogram[i] < 80 * expected / 100) {
        fprintf (stderr, "test-random: "
                 "random data is not uniformly distributed\n"
                 "eg. byte %d occurs %u times (expected about %u times)\n",
                 i, histogram[i], expected);
        exit (EXIT_FAILURE);
      }
    }
  
    /* Randomly read parts of the disk to ensure we get the same data.
     */
    xsrandom (time (NULL), &random_state);
    for (i = 0; i < NR_READS; ++i) {
      offset = xrandom (&random_state);
      offset %= SIZE - RSIZE;
      if (nbd_pread (nbd, rdata, sizeof rdata, offset, 0) == -1) {
        fprintf (stderr, "%s\n", nbd_get_error ());
        exit (EXIT_FAILURE);
      }
      if (memcmp (&data[offset], rdata, RSIZE) != 0) {
        fprintf (stderr, "test-random: returned different data\n");
        exit (EXIT_FAILURE);
      }
    }
  
    nbd_close (nbd);
    exit (EXIT_SUCCESS);
  }
  