headers/private/kernel/util/Random.h

   1 /*
   2  * Copyright 2013 Haiku, Inc. All rights reserved.
   3  * Distributed under the terms of the MIT License.
   4  *
   5  * Authors:
   6  *              Paweł Dziepak, pdziepak@quarnos.org
   7  */
   8 #ifndef KERNEL_UTIL_RANDOM_H
   9 #define KERNEL_UTIL_RANDOM_H
  10
  11
  12 #include <smp.h>
  13 #include <SupportDefs.h>
  14
  15
  16 #define MAX_FAST_RANDOM_VALUE           0x7fff
  17 #define MAX_RANDOM_VALUE                        0x7fffffffu
  18 #define MAX_SECURE_RANDOM_VALUE         0xffffffffu
  19
  20 static const int        kFastRandomShift                = 15;
  21 static const int        kRandomShift                    = 31;
  22 static const int        kSecureRandomShift              = 32;
  23
  24 #ifdef __cplusplus
  25 extern "C" {
  26 #endif
  27
  28 unsigned int    fast_random_value(void);
  29 unsigned int    random_value(void);
  30 unsigned int    secure_random_value(void);
  31
  32 #ifdef __cplusplus
  33 }
  34 #endif
  35
  36
  37 #ifdef __cplusplus
  38
  39 template<typename T>
  40 T
  41 fast_get_random()
  42 {
  43         size_t shift = 0;
  44         T random = 0;
  45         while (shift < sizeof(T) * 8) {
  46                 random |= (T)fast_random_value() << shift;
  47                 shift += kFastRandomShift;
  48         }
  49
  50         return random;
  51 }
  52
  53
  54 template<typename T>
  55 T
  56 get_random()
  57 {
  58         size_t shift = 0;
  59         T random = 0;
  60         while (shift < sizeof(T) * 8) {
  61                 random |= (T)random_value() << shift;
  62                 shift += kRandomShift;
  63         }
  64
  65         return random;
  66 }
  67
  68
  69 template<typename T>
  70 T
  71 secure_get_random()
  72 {
  73         size_t shift = 0;
  74         T random = 0;
  75         while (shift < sizeof(T) * 8) {
  76                 random |= (T)secure_random_value() << shift;
  77                 shift += kSecureRandomShift;
  78         }
  79
  80         return random;
  81 }
  82
  83
  84 #endif  // __cplusplus
  85
  86 #endif  // KERNEL_UTIL_RANDOM_H
  87