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[Reverse-engineering] [th04] .MPN: Slot structure 

TH04 is the only game that reserves memory for 8 .MPN slots, despite
only actually using just one of them, like all other games… And there
goes another 458 bytes of conventional RAM.

Part of P0138, funded by [Anonymous] and Blue Bolt.
This commit is contained in:
nmlgc 2021-04-19 15:16:54 +02:00
parent b1cf7ee021
commit cfaa20694a
2 changed files with 51 additions and 31 deletions
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14
th04/formats/mpn.hpp Normal file
View File

@ -0,0 +1,14 @@
#include "th02/formats/mpn.hpp"
// Internal .MPN slot structure
struct mpn_t {
mpn_image_t *images;
size_t count;
Palette8 palette;
int8_t unused[10];
};
// TH04 reserves memory for 8 slots, but only actually uses the first one.
static const int MPN_COUNT = 8;
extern mpn_t mpn_slots[MPN_COUNT];

68
th04_main.asm
View File

@ -194,12 +194,12 @@ arg_6 = word ptr 0Ch
mov bx, [bp+arg_2]
shl bx, 6
mov ax, [bp+arg_0]
cmp ax, [bx+345Eh]
cmp ax, _mpn_slots[bx].MPN_count
ja short loc_36EE
shl ax, 7
mov si, ax
add si, 40h
mov dx, [bx+345Ch]
mov dx, word ptr _mpn_slots[bx].MPN_images+2
mov ds, dx
mov ax, SEG_PLANE_B
mov fs, ax
@ -12987,22 +12987,21 @@ SHARED_ segment word public 'CODE' use16
public MPN_FREE
mpn_free proc far
arg_0 = word ptr 6
@@slot = word ptr 6
push bp
mov bp, sp
push si
mov ax, [bp+arg_0]
shl ax, 6
add ax, 345Ah
mov ax, [bp+@@slot]
shl ax, 6 ; *= size mpn_t
add ax, offset _mpn_slots
mov si, ax
cmp dword ptr [si], 0
jz short loc_1320E
push word ptr [si+2]
call hmem_free
mov dword ptr [si], 0
cmp [si+mpn_t.MPN_images], 0
jz short @@ret
call hmem_free pascal, word ptr [si+mpn_t.MPN_images+2]
mov [si+mpn_t.MPN_images], 0
loc_1320E:
@@ret:
pop si
pop bp
retf 2
@ -13016,15 +13015,15 @@ include th04/hardware/input_wait.asm
public MPN_PALETTE_SHOW
mpn_palette_show proc far
arg_0 = word ptr 6
@@slot = word ptr 6
push bp
mov bp, sp
push size palette_t ; n
push ds
mov ax, [bp+arg_0]
shl ax, 6
add ax, 3460h
mov ax, [bp+@@slot]
shl ax, 6 ; *= size mpn_t
add ax, offset _mpn_slots.MPN_palette
push ax ; src
push ds
push offset Palettes ; dest
@ -13046,17 +13045,17 @@ var_8 = word ptr -8
var_6 = byte ptr -6
var_2 = byte ptr -2
arg_0 = dword ptr 6
arg_4 = word ptr 0Ah
@@slot = word ptr 0Ah
enter 8, 0
push si
push di
mov di, [bp+arg_4]
mov di, [bp+@@slot]
pushd [bp+arg_0]
call file_ropen
mov ax, di
shl ax, 6
add ax, 345Ah
shl ax, 6 ; *= size mpn_t
add ax, offset _mpn_slots
mov si, ax
push ss
lea ax, [bp+var_6]
@ -13065,16 +13064,16 @@ arg_4 = word ptr 0Ah
call file_read
mov al, [bp+var_2]
mov ah, 0
mov [si+4], ax
mov ax, [si+4]
mov [si+mpn_t.MPN_count], ax
mov ax, [si+mpn_t.MPN_count]
inc ax
shl ax, 5
shl ax, 2
mov [bp+var_8], ax
push ds
lea ax, [si+6]
lea ax, [si+mpn_t.MPN_palette]
push ax
push 30h ; '0'
push size palette_t
call file_read
cmp byte_21AF2, 0
jz short loc_132E3
@ -13086,9 +13085,9 @@ loc_132E3:
nopcall mpn_free
push [bp+var_8]
call hmem_allocbyte
mov [si+2], ax
mov word ptr [si], 0
cmp dword ptr [si], 0
mov word ptr [si+mpn_t.MPN_images+2], ax
mov word ptr [si+mpn_t.MPN_images+0], 0
cmp [si+mpn_t.MPN_images], 0
jnz short loc_13308
call file_close
mov ax, 0FFFFh
@ -13096,9 +13095,7 @@ loc_132E3:
; ---------------------------------------------------------------------------
loc_13308:
pushd dword ptr [si]
push [bp+var_8]
call file_read
call file_read pascal, large [si+mpn_t.MPN_images], [bp+var_8]
call file_close
xor ax, ax
@ -35172,7 +35169,16 @@ include libs/master.lib/superpa[bss].asm
include th01/hardware/vram_planes[bss].asm
include libs/master.lib/pfint21[bss].asm
include th03/formats/hfliplut[bss].asm
db 512 dup(?)
mpn_t struc
MPN_images dd ?
MPN_count dw ?
MPN_palette palette_t ?
db 10 dup(?)
mpn_t ends
public _mpn_slots
_mpn_slots mpn_t 8 dup(?)
include th04/snd/interrupt[bss].asm
include libs/master.lib/bgm[bss].asm
include libs/master.lib/super_wave_put[bss].asm