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

backup_type.hpp defines a Backup class to preserve variables

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





1     COMMENT (*)
2     BLANK (-)
3     *
4     *
5     *
6     *
7     *
8     *
9     -
10    *
11    -
12    Header guard
13    Header guard
14    -
15    Includes the OpenTTD header for debug functions
16    -
17    *
18    *
19    *
20    *
21    *
22    Sets up a class template with a type parameter
23    BLOCK START - Backup, type-specific class to wrap a variable to back up
      its contents
24    *
25    *
26    *
27    *
28    *
29    *
30    Defines parameterized constructor using only an initial (original) value
31    -
32    *
33    *
34    *
35    *
36    *
37    *
38    *
39    Sets up a template with a type parameter for the new value
40    Defines a parameterized constructor using both an old and new value
41    BLOCK START - Backup parameterized constructor
42    *
43    Replaces the old value
44    BLOCK END - Backup parameterized constructor
45    -
46    *
47    *
48    *
49    Defines a 
50    BLOCK START - Backup destructor
51    *
52    If the original value is valid...
53    BLOCK START - Check restoration
54    *
55    *
56    Output debug information
57    Restore the backed up value
58    BLOCK END - Check restoration
59    BLOCK END - Backup destructor
60    -
61    *
62    *
63    *
64    *
65    Defines IsValid with no arguments
66    BLOCK START - Backup::IsValid, checks state of the backup
67    Return the value of the 'valid' member
68    BLOCK END - Backup::IsValid
69    -
70    *
71    *
72    *
73    *
74    Defines Backup::GetOriginalValue with no arguments
75    BLOCK START - Backup::GetOriginalValue, returns the backup
76    Checks if the original value is actually valid
77    Returns the original value that was backed up
78    BLOCK END - Backup::GetOriginalValue
79    -
80    *
81    *
82    *
83    *
84    *
85    Sets up a template with a type name
86    Defines Backup::Change with one argument: a value of input type
87    BLOCK START - Backup::Change, changes the backup
88    *
89    Check if the backup is valid...
90    So we can update the value pointer knowing it's backed up
91    BLOCK END - Backup::Change
92    -
93    *
94    *
95    *
96    Defines Backup::Revert with no arguments
97    BLOCK START - Backup::Revert, matches the current to the backup
98    Check that the backup is valid
99    Restore the backed up value
100   BLOCK END - Backup::Revert
101   -
102   *
103   *
104   *
105   Defines Backup::Trash
106   BLOCK START - Backup::Trash, gets rid of the backup
107   Check that the backup is valid
108   Invalidate the backup
109   BLOCK END - Backup::Trash
110   -
111   *
112   *
113   *
114   Defines Backup::Restore
115   BLOCK START - Backup::Restore, fully restores the backup
116   Restore the original backup valid
117   Get rid of the backup now that it's restored
118   BLOCK END - Backup::Restore
119   -
120   *
121   *
122   *
123   *
124   Defines Backup::Update
125   BLOCK START - Backup::Update, changes the backed up value
126   Check that the backup is valid
127   Backup a new value
128   BLOCK END - Backup::Update
129   -
130   *
131   *
132   *
133   *
134   Defines Backup::Verify
135   BLOCK START - Backup::Verify, checks that current and backup match
136   Check that the backup is valid
137   Check that the current and backup values match
138   BLOCK END - Backup::Verify
139   -
140   Begins the private section, which holds the data
141   Declares a reference to the original value location
142   Declares a flag indicating if the value is currently valid
143   Declares a local value to back up
144   -
145   Declares a debug output file name
146   Declares a debug ouptut file line number
147   BLOCK END - Backup
148   -
149   Header guard end