blob: 441f8e6e10fce9b7dff585f0743eb5525e329cbf (
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
|
// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
namespace search {
/*
* Simple random generator based on lrand48() spec.
*/
class Rand48
{
private:
uint64_t _state;
public:
void
srand48(long seed)
{
_state = ((static_cast<uint64_t>(seed & 0xffffffffu)) << 16) + 0x330e;
}
Rand48(void)
: _state(0)
{
srand48(0x1234abcd);
};
void iterate(void) {
_state = (UINT64_C(0x5DEECE66D) * _state + 0xb) &
UINT64_C(0xFFFFFFFFFFFF);
}
/*
* Return value from 0 to 2^31 - 1
*/
long lrand48(void) {
iterate();
return static_cast<long>(_state >> 17);
}
};
} // namespace search
|
