tests/helpers/c/prng.c

   1 /*
   2  * Very simple prng to allow for randomized tests with reproducable
   3  * results.
   4  *
   5  * Copyright (C) 2012 by Open Source Routing.
   6  * Copyright (C) 2012 by Internet Systems Consortium, Inc. ("ISC")
   7  * Copyright (C) 2017 Christian Franke
   8  *
   9  * This file is part of Quagga
  10  *
  11  * Quagga is free software; you can redistribute it and/or modify it
  12  * under the terms of the GNU General Public License as published by the
  13  * Free Software Foundation; either version 2, or (at your option) any
  14  * later version.
  15  *
  16  * Quagga is distributed in the hope that it will be useful, but
  17  * WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  * General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License along
  22  * with this program; see the file COPYING; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  24  */
  25
  26 #include <zebra.h>
  27
  28 #include <assert.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31
  32 #include "prng.h"
  33
  34 struct prng {
  35         uint64_t state;
  36 };
  37
  38 struct prng *prng_new(unsigned long long seed)
  39 {
  40         struct prng *rv = calloc(sizeof(*rv), 1);
  41         assert(rv);
  42
  43         rv->state = seed;
  44
  45         return rv;
  46 }
  47
  48 /*
  49  * This implementation has originally been provided to musl libc by
  50  * Szabolcs Nagy <nsz at port70 dot net> in 2013 under the terms of
  51  * the MIT license.
  52  * It is a simple LCG which D.E. Knuth attributes to C.E. Haynes in
  53  * TAOCP Vol2 3.3.4
  54  */
  55 int prng_rand(struct prng *prng)
  56 {
  57         prng->state = 6364136223846793005ULL * prng->state + 1;
  58         return prng->state >> 33;
  59 }
  60
  61 const char *prng_fuzz(struct prng *prng, const char *string,
  62                       const char *charset, unsigned int operations)
  63 {
  64         static char buf[256];
  65         unsigned int charset_len;
  66         unsigned int i;
  67         unsigned int offset;
  68         unsigned int op;
  69         unsigned int character;
  70
  71         assert(strlen(string) < sizeof(buf));
  72
  73         strncpy(buf, string, sizeof(buf));
  74         charset_len = strlen(charset);
  75
  76         for (i = 0; i < operations; i++) {
  77                 offset = prng_rand(prng) % strlen(buf);
  78                 op = prng_rand(prng) % 3;
  79
  80                 switch (op) {
  81                 case 0:
  82                         /* replace */
  83                         character = prng_rand(prng) % charset_len;
  84                         buf[offset] = charset[character];
  85                         break;
  86                 case 1:
  87                         /* remove */
  88                         memmove(buf + offset, buf + offset + 1,
  89                                 strlen(buf) - offset);
  90                         break;
  91                 case 2:
  92                         /* insert */
  93                         assert(strlen(buf) + 1 < sizeof(buf));
  94
  95                         memmove(buf + offset + 1, buf + offset,
  96                                 strlen(buf) + 1 - offset);
  97                         character = prng_rand(prng) % charset_len;
  98                         buf[offset] = charset[character];
  99                         break;
 100                 }
 101         }
 102         return buf;
 103 }
 104
 105 void prng_free(struct prng *prng)
 106 {
 107         free(prng);
 108 }