reactos/lib/rtl/random.c

   1 /*
   2  * COPYRIGHT:         See COPYING in the top level directory
   3  * PROJECT:           ReactOS system libraries
   4  * PURPOSE:           Random number generator functions
   5  * FILE:              lib/rtl/random.c
   6  * PROGRAMMER:        Wine
   7  *                    Pierre Schweitzer (pierre@reactos.org)
   8  */
   9
  10 /* INCLUDES *****************************************************************/
  11
  12 #include <rtl.h>
  13
  14 #define NDEBUG
  15 #include <debug.h>
  16
  17 static ULONG RtlpRandomConstantVector[128] =
  18 {
  19     0x4c8bc0aa, 0x4c022957, 0x2232827a, 0x2f1e7626,  /*   0 */
  20     0x7f8bdafb, 0x5c37d02a, 0x0ab48f72, 0x2f0c4ffa,  /*   4 */
  21     0x290e1954, 0x6b635f23, 0x5d3885c0, 0x74b49ff8,  /*   8 */
  22     0x5155fa54, 0x6214ad3f, 0x111e9c29, 0x242a3a09,  /*  12 */
  23     0x75932ae1, 0x40ac432e, 0x54f7ba7a, 0x585ccbd5,  /*  16 */
  24     0x6df5c727, 0x0374dad1, 0x7112b3f1, 0x735fc311,  /*  20 */
  25     0x404331a9, 0x74d97781, 0x64495118, 0x323e04be,  /*  24 */
  26     0x5974b425, 0x4862e393, 0x62389c1d, 0x28a68b82,  /*  28 */
  27     0x0f95da37, 0x7a50bbc6, 0x09b0091c, 0x22cdb7b4,  /*  32 */
  28     0x4faaed26, 0x66417ccd, 0x189e4bfa, 0x1ce4e8dd,  /*  36 */
  29     0x5274c742, 0x3bdcf4dc, 0x2d94e907, 0x32eac016,  /*  40 */
  30     0x26d33ca3, 0x60415a8a, 0x31f57880, 0x68c8aa52,  /*  44 */
  31     0x23eb16da, 0x6204f4a1, 0x373927c1, 0x0d24eb7c,  /*  48 */
  32     0x06dd7379, 0x2b3be507, 0x0f9c55b1, 0x2c7925eb,  /*  52 */
  33     0x36d67c9a, 0x42f831d9, 0x5e3961cb, 0x65d637a8,  /*  56 */
  34     0x24bb3820, 0x4d08e33d, 0x2188754f, 0x147e409e,  /*  60 */
  35     0x6a9620a0, 0x62e26657, 0x7bd8ce81, 0x11da0abb,  /*  64 */
  36     0x5f9e7b50, 0x23e444b6, 0x25920c78, 0x5fc894f0,  /*  68 */
  37     0x5e338cbb, 0x404237fd, 0x1d60f80f, 0x320a1743,  /*  72 */
  38     0x76013d2b, 0x070294ee, 0x695e243b, 0x56b177fd,  /*  76 */
  39     0x752492e1, 0x6decd52f, 0x125f5219, 0x139d2e78,  /*  80 */
  40     0x1898d11e, 0x2f7ee785, 0x4db405d8, 0x1a028a35,  /*  84 */
  41     0x63f6f323, 0x1f6d0078, 0x307cfd67, 0x3f32a78a,  /*  88 */
  42     0x6980796c, 0x462b3d83, 0x34b639f2, 0x53fce379,  /*  92 */
  43     0x74ba50f4, 0x1abc2c4b, 0x5eeaeb8d, 0x335a7a0d,  /*  96 */
  44     0x3973dd20, 0x0462d66b, 0x159813ff, 0x1e4643fd,  /* 100 */
  45     0x06bc5c62, 0x3115e3fc, 0x09101613, 0x47af2515,  /* 104 */
  46     0x4f11ec54, 0x78b99911, 0x3db8dd44, 0x1ec10b9b,  /* 108 */
  47     0x5b5506ca, 0x773ce092, 0x567be81a, 0x5475b975,  /* 112 */
  48     0x7a2cde1a, 0x494536f5, 0x34737bb4, 0x76d9750b,  /* 116 */
  49     0x2a1f6232, 0x2e49644d, 0x7dddcbe7, 0x500cebdb,  /* 120 */
  50     0x619dab9e, 0x48c626fe, 0x1cda3193, 0x52dabe9d   /* 124 */
  51 };
  52
  53 static ULONG RtlpRandomExConstantVector[128] =
  54 {
  55     0x4c8bc0aa, 0x51a0b326, 0x7112b3f1, 0x1b9ca4e1,  /*   0 */
  56     0x735fc311, 0x6fe48580, 0x320a1743, 0x494045ca,  /*   4 */
  57     0x103ad1c5, 0x4ba26e25, 0x62f1d304, 0x280d5677,  /*   8 */
  58     0x070294ee, 0x7acef21a, 0x62a407d5, 0x2dd36af5,  /*  12 */
  59     0x194f0f95, 0x1f21d7b4, 0x307cfd67, 0x66b9311e,  /*  16 */
  60     0x60415a8a, 0x5b264785, 0x3c28b0e4, 0x08faded7,  /*  20 */
  61     0x556175ce, 0x29c44179, 0x666f23c9, 0x65c057d8,  /*  24 */
  62     0x72b97abc, 0x7c3be3d0, 0x478e1753, 0x3074449b,  /*  28 */
  63     0x675ee842, 0x53f4c2de, 0x44d58949, 0x6426cf59,  /*  32 */
  64     0x111e9c29, 0x3aba68b9, 0x242a3a09, 0x50ddb118,  /*  36 */
  65     0x7f8bdafb, 0x089ebf23, 0x5c37d02a, 0x27db8ca6,  /*  40 */
  66     0x0ab48f72, 0x34995a4e, 0x189e4bfa, 0x2c405c36,  /*  44 */
  67     0x373927c1, 0x66c20c71, 0x5f991360, 0x67a38fa3,  /*  48 */
  68     0x4edc56aa, 0x25a59126, 0x34b639f2, 0x1679b2ce,  /*  52 */
  69     0x54f7ba7a, 0x319d28b5, 0x5155fa54, 0x769e6b87,  /*  56 */
  70     0x323e04be, 0x4565a5aa, 0x5974b425, 0x5c56a104,  /*  60 */
  71     0x25920c78, 0x362912dc, 0x7af3996f, 0x5feb9c87,  /*  64 */
  72     0x618361bf, 0x433fbe97, 0x0244da8e, 0x54e3c739,  /*  68 */
  73     0x33183689, 0x3533f398, 0x0d24eb7c, 0x06428590,  /*  72 */
  74     0x09101613, 0x53ce5c5a, 0x47af2515, 0x2e003f35,  /*  76 */
  75     0x15fb4ed5, 0x5e5925f4, 0x7f622ea7, 0x0bb6895f,  /*  80 */
  76     0x2173cdb6, 0x0467bb41, 0x2c4d19f1, 0x364712e1,  /*  84 */
  77     0x78b99911, 0x0a39a380, 0x3db8dd44, 0x6b4793b8,  /*  88 */
  78     0x09b0091c, 0x47ef52b0, 0x293cdcb3, 0x707b9e7b,  /*  92 */
  79     0x26d33ca3, 0x1e527faa, 0x3fe08625, 0x42560b04,  /*  96 */
  80     0x139d2e78, 0x0b558cdb, 0x28a68b82, 0x7ba3a51d,  /* 100 */
  81     0x52dabe9d, 0x59c3da1d, 0x5676cf9c, 0x152e972f,  /* 104 */
  82     0x6d8ac746, 0x5eb33591, 0x78b30601, 0x0ab68db0,  /* 108 */
  83     0x34737bb4, 0x1b6dd168, 0x76d9750b, 0x2ddc4ff2,  /* 112 */
  84     0x18a610cd, 0x2bacc08c, 0x422db55f, 0x169b89b6,  /* 116 */
  85     0x5274c742, 0x615535dd, 0x46ad005d, 0x4128f8dd,  /* 120 */
  86     0x29f5875c, 0x62c6f3ef, 0x2b3be507, 0x4a8e003f   /* 124 */
  87 };
  88
  89 static ULONG RtlpRandomExAuxVarY = 0x7775fb16;
  90
  91 #define LCG_A 0x7fffffed
  92 #define LCG_C 0x7fffffc3
  93 #define LCG_M MAXLONG
  94
  95 /*************************************************************************
  96  * RtlRandom   [NTDLL.@]
  97  *
  98  * Generates a random number. This is based on a LCG.
  99  * This makes it not suitable for Monte Carlo simulations nor
 100  * cryptographic applications.
 101  * See LCG_A, LCG_C, LCG_M for parameters.
 102  *
 103  * PARAMS
 104  *  Seed [O] The seed of the Random function
 105  *
 106  * RETURNS
 107  *  It returns a random number distributed over [0..MAXLONG-1].
 108  */
 109 /*
 110 * @implemented
 111 */
 112 ULONG NTAPI
 113 RtlRandom (IN OUT PULONG Seed)
 114 {
 115    ULONG Rand;
 116    int Pos;
 117    ULONG Result;
 118
 119    PAGED_CODE_RTL();
 120
 121    Rand = (*Seed * LCG_A + LCG_C) % LCG_M;
 122    *Seed = (Rand * LCG_A + LCG_C) % LCG_M;
 123    Pos = *Seed & (sizeof(RtlpRandomConstantVector) / sizeof(RtlpRandomConstantVector[0]) - 1);
 124    Result = RtlpRandomConstantVector[Pos];
 125    RtlpRandomConstantVector[Pos] = Rand;
 126
 127    return Result;
 128 }
 129
 130 /*************************************************************************
 131  * RtlRandomEx   [NTDLL.@]
 132  *
 133  * Generates a random number. This is based on a LCG.
 134  * This makes it not suitable for Monte Carlo simulations nor
 135  * cryptographic applications.
 136  * This one is faster than RtlRandom.
 137  * See LCG_A, LCG_C, LCG_M for parameters.
 138  *
 139  * PARAMS
 140  *  Seed [O] The seed of the Random function
 141  *
 142  * RETURNS
 143  *  It returns a random number distributed over [0..MAXLONG-1].
 144  */
 145 /*
 146 * @implemented
 147 */
 148 ULONG
 149 NTAPI
 150 RtlRandomEx( IN OUT PULONG Seed
 151         )
 152 {
 153    ULONG Rand;
 154    int Pos;
 155
 156    PAGED_CODE_RTL();
 157
 158    Pos = RtlpRandomExAuxVarY & (sizeof(RtlpRandomExConstantVector) / sizeof(RtlpRandomExConstantVector[0]) - 1);
 159    RtlpRandomExAuxVarY = RtlpRandomExConstantVector[Pos];
 160    Rand = (*Seed * LCG_A + LCG_C) % LCG_M;
 161    RtlpRandomExConstantVector[Pos] = Rand;
 162    *Seed = Rand;
 163
 164    return Rand;
 165 }
 166
 167
 168
 169 /*************************************************************************
 170  * RtlUniform   [NTDLL.@]
 171  *
 172  * Generates an uniform random number
 173  *
 174  * PARAMS
 175  *  Seed [O] The seed of the Random function
 176  *
 177  * RETURNS
 178  *  It returns a random number uniformly distributed over [0..MAXLONG-1].
 179  *
 180  * NOTES
 181  *  Generates an uniform random number using LCG. In spite of what
 182  *  MSDN states, this is an LCG and not a Lehmer RNG since C is defined.
 183  *  This makes it not suitable for Monte Carlo simulations nor
 184  *  cryptographic applications.
 185  *  See LCG_A, LCG_C, LCG_M for parameters.
 186  *
 187  * DIFFERENCES
 188  *  The native documentation states that the random number is
 189  *  uniformly distributed over [0..MAXLONG]. In reality the native
 190  *  function and our function return a random number uniformly
 191  *  distributed over [0..MAXLONG-1].
 192  */
 193 ULONG
 194 NTAPI
 195 RtlUniform(IN PULONG Seed)
 196 {
 197     ULONG Result;
 198
 199     /* Generate the random number */
 200     Result = (*Seed * LCG_A + LCG_C) % LCG_M;
 201
 202     /* Return it */
 203     *Seed = Result;
 204     return Result;
 205 }