tests/test-random.c

   1 /* nbdkit
   2  * Copyright (C) 2017-2018 Red Hat Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdint.h>
  38 #include <inttypes.h>
  39 #include <string.h>
  40 #include <unistd.h>
  41 #include <time.h>
  42
  43 #include <guestfs.h>
  44
  45 #include "random.h"
  46
  47 #include "test.h"
  48
  49 #define SIZE 1024*1024
  50 static char data[SIZE];
  51
  52 static unsigned histogram[256];
  53
  54 /* After reading the whole disk above, we then read randomly selected
  55  * subsets of the disk and compare the data (it should be identical).
  56  */
  57 #define RSIZE 10240
  58 #define NR_READS 50
  59
  60 int
  61 main (int argc, char *argv[])
  62 {
  63   guestfs_h *g;
  64   int r, i;
  65   struct random_state random_state;
  66   unsigned offset;
  67   char sizearg[32];
  68   char *rdata;
  69   size_t rsize;
  70
  71   snprintf (sizearg, sizeof sizearg, "%d", SIZE);
  72
  73   if (test_start_nbdkit ("random", sizearg, NULL) == -1)
  74     exit (EXIT_FAILURE);
  75
  76   g = guestfs_create ();
  77   if (g == NULL) {
  78     perror ("guestfs_create");
  79     exit (EXIT_FAILURE);
  80   }
  81
  82   r = guestfs_add_drive_opts (g, "",
  83                               GUESTFS_ADD_DRIVE_OPTS_READONLY, 1,
  84                               GUESTFS_ADD_DRIVE_OPTS_FORMAT, "raw",
  85                               GUESTFS_ADD_DRIVE_OPTS_PROTOCOL, "nbd",
  86                               GUESTFS_ADD_DRIVE_OPTS_SERVER, server,
  87                               -1);
  88   if (r == -1)
  89     exit (EXIT_FAILURE);
  90
  91   if (guestfs_launch (g) == -1)
  92     exit (EXIT_FAILURE);
  93
  94   /* Read the whole device. */
  95   rdata = guestfs_pread_device (g, "/dev/sda", SIZE, 0, &rsize);
  96   if (rdata == NULL)
  97     exit (EXIT_FAILURE);
  98   if (rsize != SIZE) {
  99     fprintf (stderr, "test-random: short read\n");
 100     exit (EXIT_FAILURE);
 101   }
 102   memcpy (data, rdata, SIZE);
 103   free (rdata);
 104
 105   /* Test that the data is sufficiently random using a simple
 106    * histogram.  This just tests for gross errors and is not a
 107    * complete statistical study.
 108    */
 109   for (i = 0; i < SIZE; ++i) {
 110     unsigned char c = (unsigned char) data[i];
 111     histogram[c]++;
 112   }
 113   for (i = 0; i < 256; ++i) {
 114     const unsigned expected = SIZE / 256;
 115     if (histogram[i] < 80 * expected / 100) {
 116       fprintf (stderr, "test-random: "
 117                "random data is not uniformly distributed\n"
 118                "eg. byte %d occurs %u times (expected about %u times)\n",
 119                i, histogram[i], expected);
 120       exit (EXIT_FAILURE);
 121     }
 122   }
 123
 124   /* Randomly read parts of the disk to ensure we get the same data.
 125    */
 126   xsrandom (time (NULL), &random_state);
 127   for (i = 0; i < NR_READS; ++i) {
 128     offset = xrandom (&random_state);
 129     offset %= SIZE - RSIZE;
 130     rdata = guestfs_pread_device (g, "/dev/sda", RSIZE, offset, &rsize);
 131     if (rdata == NULL)
 132       exit (EXIT_FAILURE);
 133     if (rsize != RSIZE) {
 134       fprintf (stderr, "test-random: short read\n");
 135       exit (EXIT_FAILURE);
 136     }
 137     if (memcmp (&data[offset], rdata, rsize) != 0) {
 138       fprintf (stderr, "test-random: returned different data\n");
 139       exit (EXIT_FAILURE);
 140     }
 141     free (rdata);
 142   }
 143
 144   if (guestfs_shutdown (g) == -1)
 145     exit (EXIT_FAILURE);
 146
 147   guestfs_close (g);
 148   exit (EXIT_SUCCESS);
 149 }