blob: a5629862f3bc901f40a49c3fc002b859a088fb88 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
/*++
Copyright (c) 1989 Microsoft Corporation
Module Name:
Random.c
Abstract:
This module implements a simple random number generator
Author:
Gary Kimura [GaryKi] 26-May-1989
Environment:
Pure utility routine
Revision History:
--*/
#include <ntrtlp.h>
#if defined(ALLOC_PRAGMA) && defined(NTOS_KERNEL_RUNTIME)
#pragma alloc_text(PAGE, RtlRandom)
#endif
#define Multiplier ((ULONG)(0x80000000ul - 19)) // 2**31 - 19
#define Increment ((ULONG)(0x80000000ul - 61)) // 2**31 - 61
#define Modulus ((ULONG)(0x80000000ul - 1)) // 2**31 - 1
#if !defined(NTOS_KERNEL_RUNTIME)
ULONG
RtlUniform (
IN OUT PULONG Seed
)
/*++
Routine Description:
A simple uniform random number generator, based on D.H. Lehmer's 1948
alrogithm.
Arguments:
Seed - Supplies a pointer to the random number generator seed.
Return Value:
ULONG - returns a random number uniformly distributed over [0..MAXLONG]
--*/
{
*Seed = ((Multiplier * (*Seed)) + Increment) % Modulus;
return *Seed;
}
#endif
#define UniformMacro(Seed) ( \
*Seed = (((Multiplier * (*Seed)) + Increment) % Modulus) \
)
extern ULONG V[];
ULONG
RtlRandom (
IN OUT PULONG Seed
)
/*++
Routine Description:
An every better random number generator based on MacLaren and Marsaglia.
Arguments:
Seed - Supplies a pointer to the random number generator seed.
Return Value:
ULONG - returns a random number uniformly distributed over [0..MAXLONG]
--*/
{
ULONG X;
ULONG Y;
ULONG j;
ULONG Result;
RTL_PAGED_CODE();
X = UniformMacro(Seed);
Y = UniformMacro(Seed);
j = Y % 128;
Result = V[j];
V[j] = X;
return Result;
}
|
