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

SAVE.C provides functions to save and restore the game

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

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



1     COMMENT
2     COMMENT
3     COMMENT
4     COMMENT
5     COMMENT
6     BLANK
7     COMMENT
8     COMMENT
9     COMMENT
10    COMMENT
11    COMMENT
12    COMMENT
13    BLANK
14    Includes the game header
15    Includes the console management header
16    BLANK
17    COMMENT
18    COMMENT
19    COMMENT
20    Imports pointer to the saved game window
21    Imports errno for return values
22    Imports the bottom of user memory
23    Imports the top of user memory
24    Imports the screen retrace checking state
25    Imports the screen color mode
26    BLANK
27    Defines a macro for the id string length
28    Defines a string to id the save
29    BLANK
30    Defines a macro for printf to printw (for the ONE case of printf :S)
31    COMMENT
32    COMMENT
33    COMMENT
34    COMMENT
35    COMMENT
36    Defines the sector size...which is unused
37    BLANK
38    COMMENT
39    COMMENT
40    COMMENT
41    COMMENT

SAVE THE GAME

42    Defines save_game with no arguments
43    BLOCK START - save_game, saves the game
44    Check if this is NOT the demo version. Can't save game in the demo
45    Declare a return value
46    Declare a buffer for the save game name
47    BLANK
48    Clear the output message buffer
49    Set message buffer position to 0
50    If we're in terse mode
51    Print a short message asking for a save game name
52    Otherwise we're in long mode
53    Print a longer message...
54    Including the default save game name
55    The return code is the player's input for game name
56    If no name was entered
57    Use the default name
58    Output a blank message
59    And set message buffer position to zero
60    If the player didn't hit escape (want's to save)
61    BLOCK START - Save the game
62    Perform save of data segment and if the return value is failure...
63    BLOCK START - Failed to save
64    If there was no file to delete...
65    Output a message suggesting that the drive is out of space
66    In any case, output failure message
67    Clear save flag
68    BLOCK END - Failed to save
69    Otherwise success. If there is some value for the return code
70    End process with successful save message
71    BLOCK END - Save the game
72    Otherwise this is the demo
73    BLOCK END - save_game
74    End check for demo
75    COMMENT
76    COMMENT
77    COMMENT
78    COMMENT
79    COMMENT
80    COMMENT
81    COMMENT
82    COMMENT

SAVE DATA SEGMENT

83    Defines save_ds with one argument
84    Argument 1 is the name of the save game
85    BLOCK START - save_ds, saves the data segment containing game data
86    Declare an integer file descriptor
87    Declare a character for user input
88    BLANK
89    Attempt to open the input file name and if it exists...
90    BLOCK START - Overwrite save game
91    Close the file
92    Send a query for permission to overwrite the save game
93    Get user answer
94    Clear message buffer
95    If the user didn't answer yes
96    Return failure
97    BLOCK END - Overwrite save game
98    BLANK
99    Attempt to create a file from data at 0ffset 666. If this fails...
100   BLOCK START - Cannot create file
101   Send failure message
102   Return failure
103   BLOCK END - Cannot create file
104   Set save flag to true
105   Message buffer position to zero
106   BLANK
107   Errno to 1
108   If we cannot write the save header and get the correct size value...
109   Or if the user segment size writes don't match...
110   Or if the heap doesn't match...
111   Jump to error on line 120
112   COMMENT
113   COMMENT
114   COMMENT
115   Save the current screen state
116   Write the screen data to the save file and check size. If it matches...
117   Errno is good to go
118   Restore the screen
119   BLANK
120   Label for error and normal exit
121   Close the file
122   Switch on errno
123   BLOCK START - Switch on errno
124   If errno is any value other than 0
125   Send message about failure
126   Return failure to save
127   If errno is ok
128   Move to the bottom left
129   Clear the line
130   Move back one line (presumably to exit to prompt at the bottom)
131   Return true
132   BLOCK END - Switch on errno
133   BLOCK END - save_ds
134   End check for demo
135   COMMENT
136   COMMENT
137   COMMENT
138   COMMENT
139   COMMENT
140   COMMENT
141   COMMENT
142   COMMENT
143   COMMENT
144   COMMENT
145   COMMENT

RESTORE A SAVED GAME

146   Defines restore with one argument
147   Argument 1 is the name of the save file
148   BLOCK START - restore, loads and continues a saved game
149   Check if this is NOT the demo...no loading games in the demo
150   Declare integers to check save version
151   Declare integers for file descriptor and column width
152   Declare two buffers for file name and error
153   Declare an error string
154   Declare a register set
155   Declare counter of bytes
156   Declare a buffer for the save ID
157   BLANK
158   Save the original register pointer
159   Initialize the game window
160   If we're in black and white mode
161   Set the black and white mode
162   If we're skipping the screen retrace check
163   Match the flags
164   Save the old flag
165   Copy the default error message to the buffer
166   COMMENT
167   COMMENT
168   COMMENT
169   COMMENT
170   Save the current revision
171   Save the current version
172   BLANK
173   Make sure we know the drive letter
174   BLOCK START - Print message for restart (this appears dead)
175   Save the current screen type
176   Print message for space bar
177   Kill the screen type (some interrupt triggered here?? - check CURSES)
178   Wait for the space bar
179   Restore te screen type
180   Add carriage return
181   BLOCK END - Print message for drive restart
182   Try to open the file, but if there is an error...
183   Quit with error message
184   Otherwise...
185   Print a game loading message
186   Copy the file name to the buffer
187   Calculate the file size
188   Read in the short file header, compare it, and if it doesn't match...
189   Output an error message
190   Otherwise success
191   BLOCK START - Read in save file data
192   If we can properly read in the data segment
193   and we can properly read in the heap
194   Jump to line 200
195   Otherwise fail with error
196   BLOCK END - Read in save file data
197   Close the save game file 
198   Exit the game
199   BLANK
200   Label after an ok read
201   Restore the registers in case they were clobbered
202   If the version numbers don't match
203   BLOCK START - Version mismatch
204   Close the save game file
205   Exit the game
206   BLOCK END - Version mismatch
207   BLANK
208   Restore the old column value
209   Move to the new heap
210   Reinit the data segment
211   Close the current screen
212   Open with the new screen data
213   If the screen sizes between games don't match...
214   BLOCK START - screen mismatch
215   Close the save game file
216   Exit the game
217   BLOCK END - screen mismatch
218   BLANK
219   Get rid of the current screen
220   Read in the screen and if the screen data doesn't match...
221   BLOCK START - Failed to get old screen
222   Close the save game file
223   Exit the game
224   BLOCK END - Failed to get old screen
225   Restore the game screen with the new data
226   BLANK
227   Everything worked! Close the file
228   Match the retrace settings
229   Set message buffer position to 0
230   Output a welcome back message
231   Roll a new random seed
232   Delete the save game file
233   End check for demo version
234   BLOCK END - restore
235   EOF˙