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[Reverse-engineering] [th05] Player shot cycle bitflags 

A TH05 innovation that actually makes the game code easier to read?!
Although it was quite hard to actually reverse-engineer it, with the
confusing flag ordering pointing to some deeper meaning behind the
flags, which really doesn't exist.

Completes P0036, funded by zorg.
This commit is contained in:
nmlgc 2019-10-13 20:52:53 +02:00
parent a84fa33beb
commit 82b0e1db24
5 changed files with 154 additions and 109 deletions
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42
Research/Borland C++ decompilation.md
View File

@ -1,3 +1,45 @@
## Signedness
| | |
|-|-|
| `MOV al, var`<br />`MOV ah, 0`| `var` is *unsigned char* |
## Arithmetic
| | |
|-|-|
| `ADD [m8], imm8` | Only achievable through a C++ method operating on a member? |
| `MOV AL, [m8]`<br />`ADD AL, imm8`<br />`MOV [m8], AL` | Opposite; *not* an inlined function |
### Arithmetic on a register *after* assigning it to a variable?
Assigment is part of the C expression. If it's a comparison, that comparison
must be spelled out to silence the `Possibly incorrect assignment` warning.
| | |
|-|-|
| `CALL somefunc`<br />`MOV ??, AX`<br />`OR AX, AX`<br />`JNZ ↑` | `while(( ?? = somefunc() ) != NULL)` |
### `SUB ??, imm` vs. `ADD ??, -imm`
`SUB` means that `??` is unsigned. Might require suffixing `imm` with `u` in
case it's part of an arithmetic expression that was promoted to `int`.
## `switch` statements
* Sequence of the individual cases is identical in both C and ASM
* Multiple cases with the same offset in the table, to code that doesn't
return? Code was compiled with `-O`
## Inlining
Always worth a try to get rid of a potential macro. Some edge cases don't
inline optimally though:
* Assignments to a pointer in `SI` – that pointer is moved to `DI`,
[clobbering that register](#clobbering-di). Try a [class method](#C++)
instead.
## C++ ## C++
* Every class method that returns `*this` inlines to the ideal representation. * Every class method that returns `*this` inlines to the ideal representation.

56
th05/player/shot_cycle_init.asm Normal file
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@ -0,0 +1,56 @@
public SHOT_CYCLE_INIT
shot_cycle_init proc near
@@cycle_flag = byte ptr [bp-1]
enter 2, 0
mov @@cycle_flag, 0
mov al, _shot_time
mov ah, 0
sub ax, 3
mov bx, ax
cmp bx, 15
ja short @@cycle____
add bx, bx
jmp word ptr cs:@@time_to_cycle[bx]
@@cycle6321:
mov @@cycle_flag, SC_6X or SC_3X or SC_2X or SC_1X
jmp short @@snd
@@cycle6_2_:
mov @@cycle_flag, SC_6X or SC_2X
jmp short @@in_a_cycle
@@cycle63__:
mov @@cycle_flag, SC_6X or SC_3X
@@snd:
call snd_se_play pascal, 1
jmp short @@in_a_cycle
@@cycle6___:
mov @@cycle_flag, SC_6X
jmp short @@in_a_cycle
@@cycle____:
mov al, 0
leave
retn
@@in_a_cycle:
mov _shot_ptr, offset _shots
mov _shot_last_id, 0
mov al, @@cycle_flag
leave
retn
db 0
@@time_to_cycle label word
dw @@cycle6___, @@cycle____, @@cycle____
dw @@cycle63__, @@cycle____, @@cycle____
dw @@cycle6_2_, @@cycle____, @@cycle____
dw @@cycle63__, @@cycle____, @@cycle____
dw @@cycle6___, @@cycle____, @@cycle____
dw @@cycle6321
shot_cycle_init endp

16
th05/th05.hpp
View File

@ -11,6 +11,22 @@
bb_seg_t pascal near bb_load(const char far *fn); bb_seg_t pascal near bb_load(const char far *fn);
/// ------- /// -------
/// Player
/// ------
// Shots
// -----
// Shot cycle bitflags
#define SC_1X 0x8 // Triggered 1× per cycle
#define SC_2X 0x2 // Triggered 2× per cycle
#define SC_3X 0x1 // Triggered 3× per cycle
#define SC_6X 0x4 // Triggered 6× per cycle
// Returns the current shot cycle, and prepares everything for more shots
// being added.
char pascal near shot_cycle_init(void);
// -----
/// ------
/// Stages /// Stages
/// ------ /// ------
void pascal near stage2_update(void); void pascal near stage2_update(void);

5
th05/th05.inc
View File

@ -2,6 +2,11 @@ GAME = 5
include th04/shared.inc include th04/shared.inc
include th05/player/shot_types.inc include th05/player/shot_types.inc
; Shot cycle bitflags
SC_1X = 08h ; Triggered 1× per cycle
SC_2X = 02h ; Triggered 2× per cycle
SC_3X = 01h ; Triggered 3× per cycle
SC_6X = 04h ; Triggered 6× per cycle
_player_option_patnum = 26 _player_option_patnum = 26

144
th05_main.asm
View File

@ -13640,81 +13640,7 @@ loc_128FA:
retf retf
sub_12842 endp sub_12842 endp
include th05/player/shot_cycle_init.asm
; =============== S U B R O U T I N E =======================================
; Attributes: bp-based frame
sub_12914 proc near
var_1 = byte ptr -1
enter 2, 0
mov [bp+var_1], 0
mov al, _shot_time
mov ah, 0
sub ax, 3
mov bx, ax
cmp bx, 0Fh
ja short loc_12951
add bx, bx
jmp word ptr cs:table_12966[bx]
loc_12932:
mov [bp+var_1], 0Fh
jmp short loc_12942
; ---------------------------------------------------------------------------
loc_12938:
mov [bp+var_1], 6
jmp short loc_12955
; ---------------------------------------------------------------------------
loc_1293E:
mov [bp+var_1], 5
loc_12942:
call snd_se_play pascal, 1
jmp short loc_12955
; ---------------------------------------------------------------------------
loc_1294B:
mov [bp+var_1], 4
jmp short loc_12955
; ---------------------------------------------------------------------------
loc_12951:
mov al, 0
leave
retn
; ---------------------------------------------------------------------------
loc_12955:
mov _shot_ptr, offset _shots
mov _shot_last_id, 0
mov al, [bp+var_1]
leave
retn
sub_12914 endp
; ---------------------------------------------------------------------------
db 0
table_12966 dw loc_1294B
dw loc_12951
dw loc_12951
dw loc_1293E
dw loc_12951
dw loc_12951
dw loc_12938
dw loc_12951
dw loc_12951
dw loc_1293E
dw loc_12951
dw loc_12951
dw loc_1294B
dw loc_12951
dw loc_12951
dw loc_12932
; =============== S U B R O U T I N E ======================================= ; =============== S U B R O U T I N E =======================================
@ -13724,7 +13650,7 @@ shot_l0 proc near
push bp push bp
mov bp, sp mov bp, sp
push si push si
call sub_12914 call shot_cycle_init
test al, 1 test al, 1
jz short loc_1299E jz short loc_1299E
call shots_add call shots_add
@ -13748,7 +13674,7 @@ shot_l1 proc near
push bp push bp
mov bp, sp mov bp, sp
push si push si
call sub_12914 call shot_cycle_init
test al, 1 test al, 1
jz short loc_129C8 jz short loc_129C8
call shots_add call shots_add
@ -13779,7 +13705,7 @@ shot_reimu_l2 proc near
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp-1], 1 mov byte ptr [bp-1], 1
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz short loc_12A49 jz short loc_12A49
test al, 8 test al, 8
@ -13853,7 +13779,7 @@ shot_reimu_l3 proc near
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp-1], 2 mov byte ptr [bp-1], 2
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz short loc_12ACD jz short loc_12ACD
test al, 8 test al, 8
@ -13930,7 +13856,7 @@ shot_reimu_l4 proc near
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp-1], 3 mov byte ptr [bp-1], 3
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz short loc_12B51 jz short loc_12B51
test al, 8 test al, 8
@ -14005,7 +13931,7 @@ shot_reimu_l5 proc near
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp-1], 3 mov byte ptr [bp-1], 3
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_12BEE jz loc_12BEE
test al, 2 test al, 2
@ -14091,7 +14017,7 @@ shot_reimu_l6 proc near
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp-1], 3 mov byte ptr [bp-1], 3
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_12C8B jz loc_12C8B
test al, 2 test al, 2
@ -14177,7 +14103,7 @@ shot_reimu_l7 proc near
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp-1], 5 mov byte ptr [bp-1], 5
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_12D28 jz loc_12D28
test al, 2 test al, 2
@ -14263,7 +14189,7 @@ shot_reimu_l8 proc near
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp-1], 7 mov byte ptr [bp-1], 7
call sub_12914 call shot_cycle_init
test al, 1 test al, 1
jnz short loc_12DA0 jnz short loc_12DA0
jmp short loc_12DA9 jmp short loc_12DA9
@ -14338,7 +14264,7 @@ shot_reimu_l9 proc near
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp-1], 7 mov byte ptr [bp-1], 7
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_12E5F jz loc_12E5F
test al, 2 test al, 2
@ -14437,7 +14363,7 @@ var_1 = byte ptr -1
enter 2, 0 enter 2, 0
push si push si
mov [bp+var_1], 1 mov [bp+var_1], 1
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz short loc_12EE1 jz short loc_12EE1
test al, 8 test al, 8
@ -14512,7 +14438,7 @@ var_1 = byte ptr -1
enter 2, 0 enter 2, 0
push si push si
mov [bp+var_1], 2 mov [bp+var_1], 2
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz loc_12F94 jz loc_12F94
test al, 8 test al, 8
@ -14619,7 +14545,7 @@ var_2 = word ptr -2
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp+var_2+1], 3 mov byte ptr [bp+var_2+1], 3
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz loc_1308E jz loc_1308E
test al, 8 test al, 8
@ -14746,7 +14672,7 @@ var_2 = word ptr -2
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp+var_2+1], 3 mov byte ptr [bp+var_2+1], 3
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz loc_13195 jz loc_13195
test al, 8 test al, 8
@ -14877,7 +14803,7 @@ var_1 = byte ptr -1
push si push si
push di push di
mov [bp+var_1], 4 mov [bp+var_1], 4
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz loc_1329E jz loc_1329E
test al, 8 test al, 8
@ -15017,7 +14943,7 @@ var_1 = byte ptr -1
push si push si
push di push di
mov [bp+var_1], 4 mov [bp+var_1], 4
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz loc_133D8 jz loc_133D8
test al, 8 test al, 8
@ -15175,7 +15101,7 @@ var_1 = byte ptr -1
push si push si
push di push di
mov [bp+var_1], 4 mov [bp+var_1], 4
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz loc_13516 jz loc_13516
test al, 8 test al, 8
@ -15333,7 +15259,7 @@ var_1 = byte ptr -1
push si push si
push di push di
mov [bp+var_1], 6 mov [bp+var_1], 6
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz loc_13697 jz loc_13697
test al, 8 test al, 8
@ -15522,7 +15448,7 @@ var_1 = byte ptr -1
enter 2, 0 enter 2, 0
push si push si
mov [bp+var_1], 2 mov [bp+var_1], 2
call sub_12914 call shot_cycle_init
test al, 5 test al, 5
jz short loc_13720 jz short loc_13720
test al, 1 test al, 1
@ -15591,7 +15517,7 @@ var_1 = byte ptr -1
enter 2, 0 enter 2, 0
push si push si
mov [bp+var_1], 2 mov [bp+var_1], 2
call sub_12914 call shot_cycle_init
test al, 5 test al, 5
jz short loc_13798 jz short loc_13798
test al, 1 test al, 1
@ -15666,7 +15592,7 @@ var_1 = byte ptr -1
enter 2, 0 enter 2, 0
push si push si
mov [bp+var_1], 4 mov [bp+var_1], 4
call sub_12914 call shot_cycle_init
test al, 5 test al, 5
jz short loc_13828 jz short loc_13828
test al, 1 test al, 1
@ -15761,7 +15687,7 @@ var_2 = word ptr -2
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp+var_2+1], 4 mov byte ptr [bp+var_2+1], 4
call sub_12914 call shot_cycle_init
test al, 5 test al, 5
jz short loc_138C0 jz short loc_138C0
test al, 1 test al, 1
@ -15854,7 +15780,7 @@ var_2 = word ptr -2
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp+var_2+1], 4 mov byte ptr [bp+var_2+1], 4
call sub_12914 call shot_cycle_init
test al, 5 test al, 5
jz loc_1396C jz loc_1396C
test al, 1 test al, 1
@ -15956,7 +15882,7 @@ var_2 = word ptr -2
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp+var_2+1], 6 mov byte ptr [bp+var_2+1], 6
call sub_12914 call shot_cycle_init
test al, 5 test al, 5
jz loc_13A1F jz loc_13A1F
test al, 1 test al, 1
@ -16064,7 +15990,7 @@ var_2 = word ptr -2
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp+var_2+1], 6 mov byte ptr [bp+var_2+1], 6
call sub_12914 call shot_cycle_init
test al, 5 test al, 5
jz loc_13AE7 jz loc_13AE7
test al, 1 test al, 1
@ -16174,7 +16100,7 @@ var_2 = word ptr -2
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp+var_2+1], 6 mov byte ptr [bp+var_2+1], 6
call sub_12914 call shot_cycle_init
test al, 5 test al, 5
jz loc_13BE8 jz loc_13BE8
test al, 1 test al, 1
@ -16320,7 +16246,7 @@ var_2 = word ptr -2
enter 2, 0 enter 2, 0
push si push si
mov byte ptr [bp+var_2+1], 1 mov byte ptr [bp+var_2+1], 1
call sub_12914 call shot_cycle_init
test al, 9 test al, 9
jz short loc_13C74 jz short loc_13C74
test al, 8 test al, 8
@ -16394,7 +16320,7 @@ var_2 = word ptr -2
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp+var_2+1], 2 mov byte ptr [bp+var_2+1], 2
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz short loc_13CFF jz short loc_13CFF
test al, 2 test al, 2
@ -16479,7 +16405,7 @@ var_2 = word ptr -2
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp+var_2+1], 3 mov byte ptr [bp+var_2+1], 3
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_13D9D jz loc_13D9D
test al, 2 test al, 2
@ -16569,7 +16495,7 @@ var_2 = word ptr -2
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp+var_2+1], 3 mov byte ptr [bp+var_2+1], 3
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_13E53 jz loc_13E53
test al, 2 test al, 2
@ -16680,7 +16606,7 @@ var_2 = word ptr -2
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp+var_2+1], 4 mov byte ptr [bp+var_2+1], 4
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_13F34 jz loc_13F34
test al, 2 test al, 2
@ -16815,7 +16741,7 @@ var_2 = word ptr -2
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp+var_2+1], 4 mov byte ptr [bp+var_2+1], 4
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_14033 jz loc_14033
test al, 2 test al, 2
@ -16963,7 +16889,7 @@ var_2 = word ptr -2
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp+var_2+1], 5 mov byte ptr [bp+var_2+1], 5
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_14131 jz loc_14131
test al, 2 test al, 2
@ -17116,7 +17042,7 @@ var_2 = word ptr -2
enter 4, 0 enter 4, 0
push si push si
mov byte ptr [bp+var_2+1], 5 mov byte ptr [bp+var_2+1], 5
call sub_12914 call shot_cycle_init
test al, 3 test al, 3
jz loc_14248 jz loc_14248
test al, 2 test al, 2