Decoded: Rogue (1980) by Toy, Arnold, Wichman
DOS version (1983) by Mel Sibony and Jon Lane
Source file: DAEMON.C
Beginner friendly, line-by-line code walkthrough by MaiZure

DAEMON.C handles background daemon systems. Creation, tracking, and execution.

Original code:
https://britzl.github.io/roguearchive/

Original code with line numbers
http://www.maizure.org/projects/decoded-rogue/DAEMON_linenum.txt



1     COMMENT
2     COMMENT
3     COMMENT
4     COMMENT
5     COMMENT
6     COMMENT
7     BLANK
8     Include the game header
9     Include the console management header
10    BLANK
11    Declare marco for EMPTY as 0 (null)
12    Declare macro for FULL as i
13    Declare macro for DAEMON as -1 (used as an init value)
14    Declares a macro for the maximum number of daemons in operation (20)
15    BLANK

DEFINE A DAEMON STRUCTURE

16    Declares a struct to hold a daemon
17    Declares an event function to execute when the daemon triggers
18    Declares an argument for the daemon to execute
19    Declares a timer used to trigger daemon events (next time to execute)
20    Ends declaration of daemon structure and allocates 20 in an array
21    BLANK
22    COMMENT
23    COMMENT
24    COMMENT
25    COMMENT

FIND DAEMON SLOT

26    d_slot returns a daemon structure
27    Define d_slot with no arguments
28    BLOCK START - d_slot returns an unused daemon slot
29    Declares a pointer to a daemon
30    BLANK
31    Loop through the daemon array
32    If an empty slot is found (empty means a slot with no function)
33    Return that slot
34    Check for debug mode (not enabled)
35    If we made it this far, we failed to find an empty. Print message
36    End check for debug mode
37    Return failure
38    BLOCK END - d_slot
39    BLANK
40    COMMENT
41    COMMENT
42    COMMENT
43    COMMENT

FIND DAEMON BY FUNCTION

44    find_slot returns a pointer to a daemon
45    Define find_slot with one argument
46    Argument 1 is a function to execute
47    BLOCK START - find_slot, returns a daemon by its function
48    Declare a pointer to a daemon slot
49    BLANK
50    Loop through the daemon list
51    If the current daemon's function matches the input..
52    Return that daemon
53    Return NULL if no match is found
54    BLOCK END - find_slot
55    BLANK
56    COMMENT
57    COMMENT
58    COMMENT
59    COMMENT

INITAILIZE A DAEMON

60    Defines daemon with two arguments
61    Argument 1 is a function to execute, Argument 2 is the function argument
62    BLOCK START - daemon, creates a daemon
63    Declares a pointer to a daemon
64    BLANK
65    Get an empty slot
66    Set the slot's function
67    Set the slot's argument 
68    Set the slot's timer to an initial value of -1 (execute immediately)
69    BLOCK END - daemon
70    BLANK
71    COMMENT
72    COMMENT
73    COMMENT
74    COMMENT

PROCESS ALL DAEMONS

75    Declare do_daemons with no arguments
76    BLOCK START - do_daemons, run daemons that are ready
77    Declare a pointer to a daemon
78    BLANK
79    COMMENT
80    COMMENT
81    COMMENT
82    Loop through the daemon list
83    COMMENT
84    COMMENT
85    COMMENT
86    If the daemon's time is expired and it has a valid function...
87    Execute that function with the arguments
88    BLOCK END - do_daemons
89    BLANK
90    COMMENT
91    COMMENT
92    COMMENT
93    COMMENT

START A DAEMON

94    Declare fuse with three arguments
95    Arg 1 is the function, argument 2 is the input arg, and 3 is the delay
96    BLOCK START - fuse, sets a daemon to go off after a delay
97    Declare a pointer to the daemon
98    BLANK
99    Find an empty daemon slot
100   Set the function
101   Set the argument
102   Set the time delay
103   BLOCK END - fuse
104   BLANK
105   COMMENT
106   COMMENT
107   COMMENT
108   COMMENT

EXTEND A DAEMON

109   Declare lengthen with two arguments
110   Argument 1 is the function to delay
111   Argument 2 is the time to delay
112   BLOCK START - lengthen, increases the time delay of a daemon
113   Declare a pointer to a daemon
114   BLANK
115   If we cannot find a daemon with the desired function...
116   Nothing to lengthen, return failure
117   Otherwise, add the delay time to the daemon we found
118   BLOCK END - lengthen
119   BLANK
120   COMMENT
121   COMMENT
122   COMMENT
123   COMMENT

DESTROY A DAEMON

124   Declares extinguish with one argument
125   Argument 1 is a daemon function
126   BLOCK START - extinguish, destroys a daemon
127   Declare a pointer to a daemon
128   BLANK
129   If there is no daemon with matching function...
130   Nothing to destroy, return
131   Remove the daemon's function, effectively ending its processing
132   BLOCK END - extinguish
133   BLANK
134   COMMENT
135   COMMENT
136   COMMENT
137   COMMENT

UPDATE AND TRIGGER DAEMONS

138   Declare do_fuses with no arguments
139   BLOCK START - do_fuses, goes through timed daemons and decrements timers
140   Declare a pointer to a daemon
141   BLANK
142   COMMENT
143   COMMENT
144   COMMENT
145   Loop through all the daemons
146   COMMENT
147   COMMENT
148   COMMENT
149   COMMENT
150   If the daemon is active, has a valid timer, but gets decremented to zero
151   BLOCK START - trigger daemon
152   Execeute the daemon function
153   Remove that daemon (only one-shot)
154   BLOCK END - trigger daemon
155   Repeat loop through all 20 daemon slots
156   BLOCK END - do_fuses
157   EOF˙