test/testutil/random.c

   1 /*
   2  * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include "../testutil.h"
  11
  12 /*
  13  * This is an implementation of the algorithm used by the GNU C library's
  14  * random(3) pseudorandom number generator as described:
  15  *      https://www.mscs.dal.ca/~selinger/random/
  16  */
  17 static uint32_t test_random_state[31];
  18
  19 uint32_t test_random(void) {
  20     static unsigned int pos = 3;
  21
  22     if (pos == 31)
  23         pos = 0;
  24     test_random_state[pos] += test_random_state[(pos + 28) % 31];
  25     return test_random_state[pos++] / 2;
  26 }
  27
  28 void test_random_seed(uint32_t sd) {
  29     int i;
  30     int32_t s;
  31     const unsigned int mod = (1u << 31) - 1;
  32
  33     test_random_state[0] = sd;
  34     for (i = 1; i < 31; i++) {
  35         s = (int32_t)test_random_state[i - 1];
  36         test_random_state[i] = (uint32_t)((16807 * (int64_t)s) % mod);
  37     }
  38     for (i = 34; i < 344; i++)
  39         test_random();
  40 }