1//============================================================================
2//
3// SSSS tt lll lll
4// SS SS tt ll ll
5// SS tttttt eeee ll ll aaaa
6// SSSS tt ee ee ll ll aa
7// SS tt eeeeee ll ll aaaaa -- "An Atari 2600 VCS Emulator"
8// SS SS tt ee ll ll aa aa
9// SSSS ttt eeeee llll llll aaaaa
10//
11// Copyright (c) 1995-2019 by Bradford W. Mott, Stephen Anthony
12// and the Stella Team
13//
14// See the file "License.txt" for information on usage and redistribution of
15// this file, and for a DISCLAIMER OF ALL WARRANTIES.
16//============================================================================
17
18#ifndef RANDOM_HXX
19#define RANDOM_HXX
20
21#include "bspf.hxx"
22#include "Serializable.hxx"
23
24/**
25 This is a quick-and-dirty random number generator. It is based on
26 information in Chapter 7 of "Numerical Recipes in C". It's a simple
27 linear congruential generator.
28
29 @author Bradford W. Mott
30*/
31class Random : public Serializable
32{
33 public:
34 /**
35 Create a new random number generator
36 */
37 explicit Random(uInt32 seed) { initSeed(seed); }
38
39 /**
40 Re-initialize the random number generator with a new seed,
41 to generate a different set of random numbers.
42 */
43 void initSeed(uInt32 seed)
44 {
45 myValue = seed;
46 }
47
48 /**
49 Answer the next random number from the random number generator
50
51 @return A random number
52 */
53 uInt32 next() const
54 {
55 return (myValue = (myValue * 2416 + 374441) % 1771875);
56 }
57
58 /**
59 Save the current state of this device to the given Serializer.
60
61 @param out The Serializer object to use
62 @return False on any errors, else true
63 */
64 bool save(Serializer& out) const override
65 {
66 try
67 {
68 out.putInt(myValue);
69 }
70 catch(...)
71 {
72 cerr << "ERROR: Random::save" << endl;
73 return false;
74 }
75
76 return true;
77 }
78
79 /**
80 Load the current state of this device from the given Serializer.
81
82 @param in The Serializer object to use
83 @return False on any errors, else true
84 */
85 bool load(Serializer& in) override
86 {
87 try
88 {
89 myValue = in.getInt();
90 }
91 catch(...)
92 {
93 cerr << "ERROR: Random::load" << endl;
94 return false;
95 }
96
97 return true;
98 }
99
100 private:
101 // Indicates the next random number
102 // We make this mutable, since it's not immediately obvious that
103 // calling next() should change internal state (ie, the *logical*
104 // state of the object shouldn't change just by asking for another
105 // random number)
106 mutable uInt32 myValue;
107
108 private:
109 // Following constructors and assignment operators not supported
110 Random() = delete;
111 Random(const Random&) = delete;
112 Random(Random&&) = delete;
113 Random& operator=(const Random&) = delete;
114 Random& operator=(Random&&) = delete;
115};
116
117#endif
118