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decompile mersenne twister prng algorhitm

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This commit is contained in:
DizzyEggg 2025-03-18 13:25:18 +01:00
parent c06beb68b7
commit a93aa61988
10 changed files with 133 additions and 315 deletions
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275
asm/code_8094D28.s
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@ -1,275 +0,0 @@
#include "asm/constants/gba_constants.inc"
#include "asm/macros.inc"
.syntax unified
.text
thumb_func_start sub_8094D74
sub_8094D74:
push {r4-r7,lr}
mov r7, r9
mov r6, r8
push {r6,r7}
mov r8, r0
adds r7, r1, 0
ldr r0, _08094E34
bl sub_8094D28
movs r4, 0x1
movs r5, 0
adds r3, r7, 0
movs r0, 0x9C
lsls r0, 2
cmp r3, r0
bge _08094D96
adds r3, r0, 0
_08094D96:
ldr r6, _08094E38
cmp r3, 0
beq _08094DE2
mov r9, r6
ldr r0, _08094E3C
adds r0, r6
mov r12, r0
adds r2, r6, 0
_08094DA6:
ldr r1, [r2]
lsrs r0, r1, 30
eors r1, r0
ldr r0, _08094E40
muls r0, r1
ldr r1, [r2, 0x4]
eors r1, r0
lsls r0, r5, 2
add r0, r8
ldr r0, [r0]
adds r1, r0
adds r1, r5
str r1, [r2, 0x4]
adds r2, 0x4
adds r4, 0x1
adds r5, 0x1
ldr r0, _08094E44
cmp r4, r0
ble _08094DD6
mov r1, r12
ldr r0, [r1]
str r0, [r6]
mov r2, r9
movs r4, 0x1
_08094DD6:
cmp r5, r7
blt _08094DDC
movs r5, 0
_08094DDC:
subs r3, 0x1
cmp r3, 0
bne _08094DA6
_08094DE2:
ldr r3, _08094E44
ldr r5, _08094E38
ldr r0, _08094E3C
adds r0, r5
mov r8, r0
lsls r0, r4, 2
subs r0, 0x4
adds r2, r0, r5
ldr r1, _08094E48
mov r12, r1
adds r7, r3, 0
_08094DF8:
ldr r0, [r2]
lsrs r1, r0, 30
eors r0, r1
mov r1, r12
muls r1, r0
ldr r0, [r2, 0x4]
eors r0, r1
subs r0, r4
str r0, [r2, 0x4]
adds r2, 0x4
adds r4, 0x1
cmp r4, r7
ble _08094E1C
mov r1, r8
ldr r0, [r1]
str r0, [r6]
adds r2, r5, 0
movs r4, 0x1
_08094E1C:
subs r3, 0x1
cmp r3, 0
bne _08094DF8
movs r0, 0x80
lsls r0, 24
str r0, [r6]
pop {r3,r4}
mov r8, r3
mov r9, r4
pop {r4-r7}
pop {r0}
bx r0
.align 2, 0
_08094E34: .4byte 0x012bd6aa
_08094E38: .4byte gUnknown_3001198
_08094E3C: .4byte 0x000009bc
_08094E40: .4byte 0x0019660d
_08094E44: .4byte 0x0000026f
_08094E48: .4byte 0x5d588b65
thumb_func_end sub_8094D74
thumb_func_start sub_8094E4C
sub_8094E4C:
push {r4-r7,lr}
mov r7, r9
mov r6, r8
push {r6,r7}
ldr r0, _08094F54
ldr r2, [r0]
ldr r1, _08094F58
mov r8, r0
cmp r2, r1
ble _08094F1C
ldr r0, _08094F5C
cmp r2, r0
bne _08094E6C
ldr r0, _08094F60
bl sub_8094D28
_08094E6C:
movs r3, 0
ldr r0, _08094F64
mov r9, r0
ldr r7, _08094F68
mov r12, r9
adds r5, r7, 0
_08094E78:
ldr r4, [r5]
movs r6, 0x80
lsls r6, 24
ands r4, r6
ldr r0, [r5, 0x4]
ldr r1, _08094F6C
ands r0, r1
orrs r4, r0
ldr r1, _08094F70
adds r0, r3, r1
lsls r0, 2
adds r0, r7
lsrs r2, r4, 1
ldr r1, [r0]
eors r1, r2
movs r0, 0x1
ands r4, r0
lsls r0, r4, 2
add r0, r12
ldr r0, [r0]
eors r1, r0
stm r5!, {r1}
adds r3, 0x1
cmp r3, 0xE2
ble _08094E78
ldr r5, _08094F74
cmp r3, r5
bgt _08094EE6
ldr r1, _08094F68
ldr r4, _08094F64
mov r12, r4
lsls r0, r3, 2
adds r2, r0, r1
ldr r4, _08094F78
adds r0, r4
adds r7, r0, r1
_08094EC0:
ldr r4, [r2]
ands r4, r6
ldr r0, [r2, 0x4]
ldr r1, _08094F6C
ands r0, r1
orrs r4, r0
lsrs r0, r4, 1
ldm r7!, {r1}
eors r1, r0
movs r0, 0x1
ands r4, r0
lsls r0, r4, 2
add r0, r12
ldr r0, [r0]
eors r1, r0
stm r2!, {r1}
adds r3, 0x1
cmp r3, r5
ble _08094EC0
_08094EE6:
ldr r2, _08094F68
ldr r0, _08094F7C
adds r3, r2, r0
ldr r4, [r3]
movs r0, 0x80
lsls r0, 24
ands r4, r0
ldr r0, [r2]
ldr r1, _08094F6C
ands r0, r1
orrs r4, r0
movs r1, 0xC6
lsls r1, 3
adds r2, r1
lsrs r0, r4, 1
ldr r1, [r2]
eors r1, r0
movs r0, 0x1
ands r4, r0
lsls r0, r4, 2
add r0, r9
ldr r0, [r0]
eors r1, r0
str r1, [r3]
movs r0, 0
mov r4, r8
str r0, [r4]
_08094F1C:
ldr r2, _08094F68
mov r0, r8
ldr r1, [r0]
lsls r0, r1, 2
adds r0, r2
ldr r4, [r0]
adds r1, 0x1
mov r0, r8
str r1, [r0]
lsrs r0, r4, 11
eors r4, r0
lsls r0, r4, 7
ldr r1, _08094F80
ands r0, r1
eors r4, r0
lsls r0, r4, 15
ldr r1, _08094F84
ands r0, r1
eors r4, r0
lsrs r0, r4, 18
eors r4, r0
adds r0, r4, 0
pop {r3,r4}
mov r8, r3
mov r9, r4
pop {r4-r7}
pop {r1}
bx r1
.align 2, 0
_08094F54: .4byte gUnknown_203B470
_08094F58: .4byte 0x0000026f
_08094F5C: .4byte 0x00000271
_08094F60: .4byte 0x00001571
_08094F64: .4byte gUnknown_203B474
_08094F68: .4byte gUnknown_3001198
_08094F6C: .4byte 0x7fffffff
_08094F70: .4byte 0x0000018d
_08094F74: .4byte 0x0000026e
_08094F78: .4byte 0xfffffc74
_08094F7C: .4byte 0x000009bc
_08094F80: .4byte 0x9d2c5680
_08094F84: .4byte 0xefc60000
thumb_func_end sub_8094E4C
.align 2,0

8
include/code_8094D28.h
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@ -1,8 +0,0 @@
#ifndef GUARD_CODE_8094D28_H
#define GUARD_CODE_8094D28_H
// code_8094D28.s
void sub_8094D28(s32 r0);
extern s32 sub_8094E4C(void);
#endif // GUARD_CODE_8094D28_H

7
include/random_mersenne_twister.h Normal file
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@ -0,0 +1,7 @@
#ifndef GUARD_RANDOM_MERSENNE_TWISTER_H
#define GUARD_RANDOM_MERSENNE_TWISTER_H
void MersenneTwister_InitializeState(u32 seed);
s32 Random32MersenneTwister(void);
#endif // GUARD_RANDOM_MERSENNE_TWISTER_H

5
ld_script.txt
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@ -290,8 +290,7 @@ SECTIONS {
src/code_809447C.o(.text);
src/code_8092334.o(.text);
src/game_options.o(.text);
src/code_8094D28.o(.text);
asm/code_8094D28.o(.text);
src/random_mersenne_twister.o(.text);
src/play_time.o(.text);
src/code_8094F88.o(.text);
src/code_80958E8.o(.text);
@ -566,7 +565,7 @@ SECTIONS {
src/pokemon.o(.rodata);
data/data_81076E4.o(.rodata);
src/game_options.o(.rodata);
src/code_8094D28.o(.rodata);
src/random_mersenne_twister.o(.rodata);
src/play_time.o(.rodata);
src/code_8094F88.o(.rodata);
src/code_80958E8.o(.rodata);

20
src/code_8094D28.c
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@ -1,20 +0,0 @@
#include "global.h"
#include "globaldata.h"
IWRAM_DATA u32 gUnknown_3001198[0x270] = {0};
EWRAM_INIT s32 gUnknown_203B470 = 0x271;
EWRAM_INIT s32 gUnknown_203B474 = 0;
UNUSED static EWRAM_INIT s32 sUnusedEwramVar = 0x9908b0df; // Hm...
void sub_8094D28(s32 r0) {
gUnknown_3001198[0] = r0;
gUnknown_203B470 = 1;
for(; gUnknown_203B470 < 0x270; gUnknown_203B470++)
{
gUnknown_3001198[gUnknown_203B470] =
(gUnknown_3001198[gUnknown_203B470 - 1] ^
(gUnknown_3001198[gUnknown_203B470 - 1] >> 0x1e)) * 0x6c078965 + gUnknown_203B470;
}
}

6
src/code_8094F88.c
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@ -1,6 +1,6 @@
#include "global.h"
#include "globaldata.h"
#include "code_8094D28.h"
#include "random_mersenne_twister.h"
#include "code_8094F88.h"
#include "constants/wonder_mail.h"
#include "dungeon.h"
@ -277,8 +277,8 @@ void sub_809542C(WonderMailSub *param_1)
gUnknown_203B480->mailType = 1;
gUnknown_203B480->unk4 = *param_1;
sub_8094D28(Rand32Bit());
gUnknown_203B480->unk10.unk10 = sub_8094E4C();
MersenneTwister_InitializeState(Rand32Bit());
gUnknown_203B480->unk10.unk10 = Random32MersenneTwister();
gUnknown_203B480->clientSpecies = GetPlayerPokemonStruct()->speciesNum;
PrintPokeNameToBuffer(buffer, GetPlayerPokemonStruct());
CopyStringtoBuffer(gUnknown_203B480->playerName, buffer);

8
src/personality_test1.c
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@ -3,7 +3,7 @@
#include "bg_palette_buffer.h"
#include "string_format.h"
#include "code_801602C.h"
#include "code_8094D28.h"
#include "random_mersenne_twister.h"
#include "code_8099360.h"
#include "constants/emotions.h"
#include "game_options.h"
@ -148,14 +148,14 @@ u32 HandleTestTrackerState(void)
break;
case PERSONALITY_TEST_END:
iVar1 = Rand32Bit() * sPersonalityTestTracker->FrameCounter;
sub_8094D28(Rand32Bit());
MersenneTwister_InitializeState(Rand32Bit());
for (counter = 0; counter < NUM_PERSONALITIES; counter++)
iVar1 *= sPersonalityTestTracker->NatureTotals[counter] + counter + 3;
iVar1 += sub_8094E4C();
iVar1 += Random32MersenneTwister();
while (iVar1 == -1)
iVar1 += sub_8094E4C();
iVar1 += Random32MersenneTwister();
sub_8011C40(iVar1);
return 3;

115
src/random_mersenne_twister.c Normal file
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@ -0,0 +1,115 @@
#include "global.h"
#include "globaldata.h"
#include "random_mersenne_twister.h"
// Implementation and names based on https://en.wikipedia.org/wiki/Mersenne_Twister
#define n (624) // degree of recurrence
#define m (397) // middle word, an offset used in the recurrence relation defining the series x, 1 <= m < n
#define w (32) // word size (in number of bits)
#define r (31) // separation point of one word, or the number of bits of the lower bitmask, 0 <= r <= w − 1
#define UMASK (0xffffffffU << r)
#define LMASK (0xffffffffU >> (w-r))
#define a (0x9908b0dfU) // coefficients of the rational normal form twist matrix
// additional Mersenne Twister tempering bit shifts/masks
#define u (11)
#define s (7)
#define t (15)
#define l (18)
// tempering bitmasks
#define b (0x9d2c5680U)
#define c (0xefc60000U)
#define f (1812433253U)
#define INITIAL_SEED (19650218U) // // suggested initial seed
static IWRAM_DATA u32 sStateArray[n] = {0}; // the array for the state vector
static EWRAM_INIT s32 sStateIndex = n + 1; // index into state vector array, 0 <= state_index <= n-1
static EWRAM_INIT s32 sTwistMatrix[2] = {0, a};
void MersenneTwister_InitializeState(u32 seed)
{
sStateArray[0] = seed;
for (sStateIndex = 1; sStateIndex < n; sStateIndex++) {
sStateArray[sStateIndex] =
(sStateArray[sStateIndex - 1] ^
(sStateArray[sStateIndex - 1] >> (w - 2))) * f + sStateIndex;
}
}
// Apparently this could improve entropy of the randomness...Though it remained unused.
UNUSED static void MersenneTwister_MixSeeds(u32 *seeds, s32 count)
{
s32 i;
s32 id;
s32 seedId;
MersenneTwister_InitializeState(INITIAL_SEED);
id = 1;
seedId = 0;
for (i = max(count, n); i != 0; i--) {
u32 bits = sStateArray[id - 1] ^ (sStateArray[id - 1] >> (w - 2));
sStateArray[id] = (sStateArray[id] ^ (bits * 0x19660d)) + seeds[seedId] + seedId;
id++;
seedId++;
if (id >= n) {
sStateArray[0] = sStateArray[n - 1];
id = 1;
}
if (seedId >= count) {
seedId = 0;
}
}
for (i = n - 1; i != 0; i--) {
u32 bits = sStateArray[id - 1] ^ (sStateArray[id - 1] >> (w - 2));
sStateArray[id] = (sStateArray[id] ^ (bits * 0x5d588b65)) - id;
id++;
if (id >= n) {
sStateArray[0] = sStateArray[n - 1];
id = 1;
}
}
sStateArray[0] = UMASK;
}
s32 Random32MersenneTwister(void)
{
u32 bits1, bits2;
s32 i;
if (sStateIndex >= n) {
// Re-initialize state if all numbers were used
if (sStateIndex == n + 1) {
MersenneTwister_InitializeState(0x1571);
}
for (i = 0; i < 227; i++) {
bits1 = (sStateArray[i] & UMASK) | (sStateArray[i + 1] & LMASK);
bits2 = sStateArray[i + m] ^ (bits1 >> 1);
sStateArray[i] = bits2 ^ sTwistMatrix[bits1 & 1];
}
for (; i < n - 1; i++) {
bits1 = (sStateArray[i] & UMASK) | (sStateArray[i + 1] & LMASK);
bits2 = sStateArray[i - 227] ^ (bits1 >> 1);
sStateArray[i] = bits2 ^ sTwistMatrix[bits1 & 1];
}
bits1 = (sStateArray[n - 1] & UMASK) | (sStateArray[0] & LMASK);
bits2 = sStateArray[m - 1] ^ (bits1 >> 1);
sStateArray[n - 1] = bits2 ^ sTwistMatrix[bits1 & 1];
sStateIndex = 0;
}
// tempering
bits1 = sStateArray[sStateIndex++];
bits1 ^= (bits1 >> u);
bits1 ^= (bits1 << s) & b;
bits1 ^= (bits1 << t) & c;
bits1 ^= (bits1 >> l);
return bits1;
}

2
sym_ewram_init.txt
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@ -127,7 +127,7 @@
.include "src/rescue_team_info.o"
.include "src/friend_area.o"
.include "src/game_options.o"
.include "src/code_8094D28.o"
.include "src/random_mersenne_twister.o"
.include "src/play_time.o"
.include "src/code_8094F88.o"
.include "src/code_80958E8.o"

2
sym_iwram.txt
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@ -9,4 +9,4 @@ gUnknown_3000C00: /* 3000C00 */
.include "src/text.o"
.include "src/music.o"
.include "src/code_803E724.o"
.include "src/code_8094D28.o"
.include "src/random_mersenne_twister.o"