tests/helpers/c/prng.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Very simple prng to allow for randomized tests with reproducable
   4  * results.
   5  *
   6  * Copyright (C) 2012 by Open Source Routing.
   7  * Copyright (C) 2012 by Internet Systems Consortium, Inc. ("ISC")
   8  * Copyright (C) 2017 Christian Franke
   9  *
  10  * This file is part of Quagga
  11  */
  12
  13 #include <zebra.h>
  14
  15 #include <assert.h>
  16 #include <stdlib.h>
  17 #include <string.h>
  18
  19 #include "prng.h"
  20
  21 struct prng {
  22         uint64_t state;
  23 };
  24
  25 struct prng *prng_new(unsigned long long seed)
  26 {
  27         struct prng *rv = calloc(sizeof(*rv), 1);
  28         assert(rv);
  29
  30         rv->state = seed;
  31
  32         return rv;
  33 }
  34
  35 /*
  36  * This implementation has originally been provided to musl libc by
  37  * Szabolcs Nagy <nsz at port70 dot net> in 2013 under the terms of
  38  * the MIT license.
  39  * It is a simple LCG which D.E. Knuth attributes to C.E. Haynes in
  40  * TAOCP Vol2 3.3.4
  41  */
  42 int prng_rand(struct prng *prng)
  43 {
  44         prng->state = 6364136223846793005ULL * prng->state + 1;
  45         return prng->state >> 33;
  46 }
  47
  48 const char *prng_fuzz(struct prng *prng, const char *string,
  49                       const char *charset, unsigned int operations)
  50 {
  51         static char buf[256];
  52         unsigned int charset_len;
  53         unsigned int i;
  54         unsigned int offset;
  55         unsigned int op;
  56         unsigned int character;
  57
  58         assert(strlen(string) < sizeof(buf));
  59
  60         strncpy(buf, string, sizeof(buf));
  61         charset_len = strlen(charset);
  62
  63         for (i = 0; i < operations; i++) {
  64                 offset = prng_rand(prng) % strlen(buf);
  65                 op = prng_rand(prng) % 3;
  66
  67                 switch (op) {
  68                 case 0:
  69                         /* replace */
  70                         character = prng_rand(prng) % charset_len;
  71                         buf[offset] = charset[character];
  72                         break;
  73                 case 1:
  74                         /* remove */
  75                         memmove(buf + offset, buf + offset + 1,
  76                                 strlen(buf) - offset);
  77                         break;
  78                 case 2:
  79                         /* insert */
  80                         assert(strlen(buf) + 1 < sizeof(buf));
  81
  82                         memmove(buf + offset + 1, buf + offset,
  83                                 strlen(buf) + 1 - offset);
  84                         character = prng_rand(prng) % charset_len;
  85                         buf[offset] = charset[character];
  86                         break;
  87                 }
  88         }
  89         return buf;
  90 }
  91
  92 void prng_free(struct prng *prng)
  93 {
  94         free(prng);
  95 }