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      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 }
     41