random.cc revision 2 
1/*
2 * Copyright (c) 2003 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <cstdlib>
30#include <cmath>
31
32#include "param.hh"
33#include "random.hh"
34
35using namespace std;
36
37class RandomContext : public ParamContext
38{
39  public:
40    RandomContext(const string &_iniSection)
41        : ::ParamContext(_iniSection) {}
42    ~RandomContext();
43
44    void checkParams();
45};
46
47RandomContext paramContext("random");
48
49Param<unsigned>
50seed(&paramContext, "seed", "seed to random number generator", 1);
51
52void
53RandomContext::checkParams()
54{
55    ::srandom(seed);
56}
57
58long
59getLong()
60{
61    return random();
62}
63
64// idea for generating a double from erand48
65double
66getDouble()
67{
68    union {
69        uint32_t _long[2];
70        uint16_t _short[4];
71    };
72
73    _long[0] = random();
74    _long[1] = random();
75
76    return ldexp((double) _short[0], -48) +
77        ldexp((double) _short[1], -32) +
78        ldexp((double) _short[2], -16);
79}
80