Decoded: OpenTTD (2003) v1.8 (2018)
Source file: random_func.cpp
Line-by-line code walkthrough by MaiZure

random_func.cpp defines functions for a random number generator

Original code:
https://github.com/MaiZure/OpenTTD-1.8/blob/master/src/core/random_func.cpp





1     COMMENT (*)
2     BLANK (-)
3     *
4     *
5     *
6     *
7     *
8     *
9     -
10    *
11    -
12    Include the OpenTTD platform-specific header
13    Include the OpenTTD randomizer header
14    Include the OpenTTD bitmath header
15    -
16    Check if randomizer debugging is enabled
17    Include the OpenTTD network subsystem header
18    Include the OpenTTD network server header
19    Include the OpenTTD network internals header
20    Include the OpenTTD company functions header
21    Include the OpenTTD file I/O functions header
22    Include the OpenTTD date functions header
23    End check for randomizer debugging
24    -
25    Include the OpenTTD safeguards header
26    -
27    Declare two global randomizers
28    -
29    *
30    *
31    *
32    *
33    Define Randomizer::Next with no arguments
34    BLOCK START - Randomizer::Next, increments to the next random number
35    Stores the current state 0
36    Stores the current state 1
37    -
38    Updates state 0 with some crypto fun stuff (uses old state too)
39    Updates state 1 with the old state and returns the new value
40    BLOCK END - Randomizer::Next
41    -
42    *
43    *
44    *
45    *
46    *
47    *
48    Defines Randomizer::Next with one argument, the upper bound
49    BLOCK START - Randomizer::Next, gets a bounded random value
50    Returns the next random value ranged to the upper bound
51    BLOCK END - Randomizer::Next
52    -
53    *
54    *
55    *
56    *
57    Defines Randomizer::SetSeed with one argument: the seed
58    BLOCK START - Randomizer::SetSeed, changes the random seed
59    Set randomizer state 0 to the seed
60    Set randomizer state 1 to the seed
61    BLOCK END - Randomizer::SetSeed
62    -
63    *
64    *
65    *
66    *
67    Defines SetRandomSeed with one argument
68    BLOCK START - SetRandomSeed, updates seeds for global randomizers
69    Resets the first randomizer with the new seed
70    Bumps the second randomizer with the new seed
71    BLOCK END - SetRandomSeed
72    -
73    Check if randomizer debugging is enabled
74    Defines DoRandom with 2 arguments, a line number and output file name
75    BLOCK START - DoRandom, Pulls a random number with logging
76    Checks for an inactive networking state
77    Outputs random debug input to the provided file
78    End check for networking state
79    -
80    Returns a random number
81    BLOCK END - DoRandom
82    -
83    Defines DoRandomRange with three arguments, 
84    BLOCK START - DoRandomRange, logs result of a ranged random call
85    Returns the value and write the output
86    BLOCK END - DoRandomRange
87    End check for randomizer debugging